The cerebral cortex is a rich and diverse structure that is the basis of intelligent behavior. One of the deepest mysteries of the function of cortex is that neural processing times are only about one hundred times as fast as the fastest response times for complex behavior. At the very least, this would seem to indicate that the cortex does massive amounts of parallel computation.This paper explores the hypothesis that an important part of the cortex can be modeled as (...) a connectionist computer that is especially suited for parallel problem solving. The connectionist computer uses a special representation, termed value unit encoding, that represents small subsets of parameters in a way that allows parallel access to many different parameter values. This computer can be thought of as computing hierarchies of sensorimotor invariants. The neural substrate can be interpreted as a commitment to data structures and algorithms that compute invariants fast enough to explain the behavioral response times. A detailed consideration of this model has several implications for the underlying anatomy and physiology. (shrink)

The exact relationship between qualia and the function of the brain remains elusive. The present approach focuses on the linkage between the neural mechanisms of the brain and the phenomenological and epistemological mechanisms of qualia. It is hypothesized that distinct characteristics of the ventral prefrontal cortical function may be crucial for the generation of these phenomenological and epistemological mechanisms this is reflected in the so-called 'neurophenomenological hypothesis'. The 'phenomenological—qualitative' character of qualia may be related with an early activation (...) in the ventromedial prefrontal cortex . The experience of 'presence' in qualia may be accounted for by a co-activation in both VMPFC and hippocampus and a concurrent deactivation in the ventrolateral prefrontal cortex and posterior cingulate. Past and future temporal dimensions may therefore be integrated within the experience of events, which in turn may account for the phenomenal characteristics of 'presence' and thus 'phenomenal time'. 'Non-structural homogeneity' in the experience of qualia may be accounted for by either 'supramodal character' or 'modality unspecifity' of >the VMPFC. The 'heterogenous' stimuli can therefore be included and integrated within one 'homogenous' event as experienced in qualia. Finally, 'transparency' in the experience of qualia may be related with the 'reciprocal suppression' between VMPFC and VLPFC. Simultaneous cognitive processing during the experience of qualia may be suppressed and may consequently account for their transparent character. Due to several methodological limitations, these 'neurophenomenological hypotheses' must be considered as preliminary. However, they may nevertheless serve as a starting point for the development of a more elaborate neuroscientific hypothesis of qualia in the future. (shrink)

IntroductionSymptoms of schizophrenia are closely related to aberrant language comprehension and production. Macroscopic brain changes seen in some patients with schizophrenia are suspected to relate to impaired language production, but this is yet to be reliably characterized. Since heterogeneity in language dysfunctions, as well as brain structure, is suspected in schizophrenia, we aimed to first seek patient subgroups with different neurobiological signatures and then quantify linguistic indices that capture the symptoms of “negative formal thought disorder”.MethodsAtlas-based cortical thickness values of (...) 66 patients with first-episode psychosis and 36 healthy controls were analyzed with hierarchical clustering algorithms to produce neuroanatomical subtypes. We then examined the generated subtypes and investigated the quantitative differences in MRS-based glutamate levels [in the dorsal anterior cingulate cortex ] as well as in three aspects of language production features: fluency, syntactic complexity, and lexical cohesion.ResultsTwo neuroanatomical subtypes among patients were observed, one with near-normal cortical thickness patterns while the other with widespread cortical thinning. Compared to the subgroup of patients with relatively normal cortical thickness patterns, the subgroup with widespread cortical thinning was older, with higher glutamate concentration in dACC and produced speech with reduced mean length of T-units and lower repeats of content words, despite being equally fluent.ConclusionWe characterized a patient subgroup with thinner cortex in first-episode psychosis. This subgroup, identifiable through macroscopic changes, is also distinguishable in terms of neurochemistry and language behavior. This study supports the hypothesis that glutamate-mediated cortical thinning may contribute to a phenotype that is detectable using the tools of computational linguistics in schizophrenia. (shrink)

Aboitiz et al. describe a hypothesis on the origin of the isocortex. They propose the reptilian dorsal cortex to be the ancestral brain structure to the mammalian isocortex. But why did the dorsal cortex expand in mammals and not in reptiles? A change in development may have provided the mammalian cortex with the ability to organize and therefore the potential to expand.

Philosophers long have noted that some sensations (particularly those of color) seem to be ineffable, or refractory to verbal description. Some proposed neurophysiological explanations of this ineffability deny the intuitive view that sensations have inherently indescribable content. The present paper suggests a new explanation of ineffability that does not have this deflationary consequence. According to the hypothesis presented here, feedback modulation of information flow in the cortex interferes with the production of narratives about sensations, thereby causing the subject to (...) assess as inadequate his or her own verbal descriptions of sensations. (shrink)

Schizophrenia is a worldwide, prevalent disorder with a multifactorial but highly genetic aetiology. A constant prevalence rate in the face of reduced fecundity has caused some to argue that an evolutionary advantage exists in unaffected relatives. Here, I critique this adaptationist approach, and review – and find wanting – Crow's “speciation” hypothesis. In keeping with available biological and psychological evidence, I propose an alternative theory of the origins of this disorder. Schizophrenia is a disorder of the social brain, and (...) it exists as a costly trade-off in the evolution of complex social cognition. Paleoanthropological and comparative primate research suggests that hominids evolved complex cortical interconnectivity (in particular, frontotemporal and frontoparietal circuits) to regulate social cognition and the intellectual demands of group living. I suggest that the ontogenetic mechanism underlying this cerebral adaptation was sequential hypermorphosis and that it rendered the hominid brain vulnerable to genetic and environmental insults. I argue that changes in genes regulating the timing of neurodevelopment occurred prior to the migration of Homo sapiens out of Africa 100,000–150,000 years ago, giving rise to the schizotypal spectrum. While some individuals within this spectrum may have exhibited unusual creativity and iconoclasm, this phenotype was not necessarily adaptive in reproductive terms. However, because the disorder shared a common genetic basis with the evolving circuitry of the social brain, it persisted. Thus schizophrenia emerged as a costly trade-off in the evolution of complex social cognition. Key Words: cortical connectivity; evolution; heterochrony; metarepresentation; primates; psychiatry; schizophrenia; social brain; social cognition. (shrink)

Objective: The dopamine hypothesis is one of the most influential theories of the neurobiological background of schizophrenia (SCZ). However, direct evidence for abnormal dopamine-related subcortical-cortical circuitry disconnectivity is still lacking. The aim of this study was therefore to test dopamine-related substantia nigra (SN)-based striato-thalamo-cortical resting-state functional connectivity (FC) in SCZ. Method: Based on our a priori hypothesis, we analyzed a large sample resting-state functional magnetic resonance imaging (fMRI) dataset from first-episode drug-naïve SCZ patients (n = 112) (...) and healthy controls (n = 82) using the SN as the seed region for an investigation of striato-thalamo-cortical FC. This was done in the standard band of slow frequency oscillations and then in its subfrequency bands (Slow4 and Slow5). Results: The analysis showed in SCZ: (1) reciprocal functional hypo-connectivity between SN and striatum, with differential patterns for Slow5 and Slow4; (2) functional hypo-connectivity between striatum and thalamus, as well as functional hyper-connectivity between thalamus and sensorimotor cortical areas, specifically in Slow4; (3) correlation of thalamo-sensorimotor functional hyper-connectivity with psychopathological symptoms. Conclusions: We demonstrate abnormal dopamine-related SN-based striato-thalamo-cortical FC in slow frequency oscillations in first-episode drug-naive SCZ. This suggests that altered dopaminergic function in the SN leads to abnormal neuronal synchronization (as indexed by FC) within subcortical-cortical circuitry, complementing the dopamine hypothesis in SCZ on the regional level of resting-state activity. (shrink)

This paper presents a computer model of cortical broadcast and competition based on spiking neurons and inspired by the hypothesis of a global neuronal workspace underlying conscious information processing in the human brain. In the model, the hypothesised workspace is realised by a collection of recurrently inter-connected regions capable of sustaining and disseminating a reverberating spatial pattern of activation. At the same time, the workspace remains susceptible to new patterns arriving from outlying cortical populations. Competition among these (...) cortical populations for influence on the workspace is effected by a combination of mutual inhibition and top-down amplification. (shrink)

Human adaptive behavior in sensorimotor control is aimed to increase the confidence in feedforward mechanisms when sensory afferents are uncertain. It is thought that these feedforward mechanisms rely on predictions from internal models. We investigate whether the brain uses an internal model of physical laws to help estimate body equilibrium when tactile inputs from the foot sole are depressed by carrying extra weight. As direct experimental evidence for such a model is limited, we used Judoka athletes thought to have built (...) up internal models of external loads as compared with Non-Athlete participants and Dancers. Using electroencephalography, we first tested the hypothesis that the influence of tactile inputs was amplified by descending cortical efferent signals. We compared the amplitude of P1N1 somatosensory cortical potential evoked by electrical stimulation of the foot sole in participants standing still with their eyes closed. We showed smaller P1N1 amplitudes in the Load compared to No Load conditions in both Non-Athletes and Dancers. This decrease neural response to tactile stimulation was associated with greater postural oscillations. By contrast in the Judoka’s group, the neural early response to tactile stimulation was unregulated in the Load condition. This suggests that the brain can selectively increase the functional gain of sensory inputs, during challenging equilibrium tasks when tactile inputs were mechanically depressed by wearing a weighted vest. In Judokas, the activation of regions such as the right posterior inferior parietal cortex as early as the P1N1 is likely the source of the neural responses being maintained similar in both Load and No Load conditions. An overweight internal model stored in the right PPC known to be involved in maintaining a coherent representation of one’s body in space can optimize predictive mechanisms in situations with high balance constraints. This hypothesis has been confirmed by showing that postural reaction evoked by a translation of the support surface on which participants were standing wearing extra-weight was improved in Judokas. (shrink)

Phenomenal awareness, the ability to be aware of one's sensations and feelings, emerges from the capacity of evolved brains to represent their own cognitive processes by iterating and self-reapplying the cortical operations that generate representations of the outer world. Search for the neuronal substrate of awareness therefore converges with the search for the neuronal code through which brains represent their environment. The hypothesis is put forward that the mammalian brain uses two complementary representational strategies. One consists of the (...) generation of neurons responding selectively to particular constellations of features, and is based on selective recombination of inputs in hierarchically structured feed-forward architectures. The other relies on the dynamic association of large numbers of distributed neurons into functionally coherent cell assemblies which as a whole represent a content of cognition. Arguments and data are presented in favor of the second strategy as the one according to which meta-representations that support awareness are established. My hypothesis is that such distributed representations self-organize through transient synchronization of the oscillatory activity. Evidence showing that similar brain states are required both for the occurrence of these synchronization phenomena and for awareness is provided. (shrink)

Libet demonstrated that a substantial duration (>0.5-1.0 s) of direct electrical stimulation of the surface of a sensory cortex at a threshold or liminal current is required before a subject can experience a percept. Libet and his co-workers originally proposed that the result could be due either to spatial and temporal facilitation of the underlying neurons or additionally to a prolonged central processing time. However, over the next four decades, Libet chose to attribute the prolonged latency for evoking conscious experience (...) to a prolonged central processing time. In my view, Libet has not provided any convincing evidence, either on the basis of his own past work or in his critique of my paper, for his hypothesis of a central processing time exceeding 0.5s before conscious experience emerges following direct electrical threshold stimulation of the cortical surface. I stand by my original results and conclusion that such prolonged latencies are largely the consequence of a dynamically increasing cortical facilitatory process that begins hundreds of milliseconds before there is a sustained neuronal activation. In some cases, the facilitatory process must overcome an initial stimulus-induced inhibition before neuronal firing commences. (shrink)

Word in noise identification is facilitated by acoustic differences between target and competing sounds and temporal separation between the onset of the masker and that of the target. Younger and older adults are able to take advantage of onset delay when the masker is dissimilar to the target word, but only younger adults are able to do so when the masker is similar. We examined the neural underpinning of this age difference using cortical evoked responses to words masked by (...) either Babble or Noise when the masker preceded the target word by 100 or 600 ms in younger and older adults, after adjusting the signal-to-noise ratios to equate behavioural performance across age groups and conditions. For the 100 ms onset delay, the word in noise elicited an acoustic change complex response that was comparable in younger and older adults. For the 600 ms onset delay, the ACC was modulated by both masker type and age. In older adults, the ACC to a word in babble was not affected by the increase in onset delay whereas younger adults showed a benefit from longer delays. Hence, the age difference in sensitivity to temporal delay is indexed by early activity in the auditory cortex. These results are consistent with the hypothesis that an increase in onset delay improves stream segregation in younger adults in both noise and babble, but only in noise for older adults and that this change in stream segregation is evident in early cortical processes. (shrink)

Fundamental questions in evolution concern deep divisions in the living world and vertical versus horizontal information transfer. Two contrasting views are: (i) three superkingdoms Archaea, Eubacteria, and Eukarya based on vertical inheritance of genes encoding ribosomes; versus (ii) a prokaryotic/eukaryotic dichotomy with unconstrained horizontal gene transfer (HGT) among prokaryotes. Vertical inheritance implies continuity of cytoplasmic and structural information whereas HGT transfers only DNA. By hypothesis, HGT of the translation machinery is constrained by interaction between new ribosomal gene products and (...) vertically inherited cytoplasmic structure made largely of preexisting ribosomes. Ribosomes differentially enhance the assembly of new ribosomes made from closely related genes and inhibit the assembly of products from more distal genes. This hypothesis suggests experiments for synthetic biology: the ability of synthetic genomes to “boot,” i.e., establish hereditary continuity, will be constrained by the phylogenetic closeness of the cell “body” into which genomes are placed. (shrink)

Pessoa et al. (1998a) summarize a wide body of data suggesting that perceptual filling-in phenomena can be attributed to neural filling-in processes. However, they reject, on philosophical grounds, the hypothesis that filled-in representations in the brain are the immediate substrate of visual percepts. It is proposed in this commentary that resonant binding between distributed cortical areas may instead be the crucial ingredient for conscious visual percepts, and that filling-in processes may facilitate the interactions between behaving organisms and object (...) surfaces. These suggestions circumvent some of the philosophical problems associated with the idea of localized visual representations. (shrink)

Functional human brain mapping is commonly performed during invasive monitoring with intracranial electroencephalographic electrodes prior to resective surgery for drug­ resistant epilepsy. The current gold standard, electrocortical stimulation mapping, is time ­consuming, sometimes elicits pain, and often induces after discharges or seizures. Moreover, there is a risk of overestimating eloquent areas due to propagation of the effects of stimulation to a broader network of language cortex. Passive iEEG spatial-temporal functional mapping has recently emerged as a potential alternative to ESM. However, (...) investigators have observed less correspondence between STFM and ESM maps of language than between their maps of motor function. We hypothesized that incongruities between ESM and STFM of language function may arise due to propagation of the effects of ESM to cortical areas having strong effective connectivity with the site of stimulation. We evaluated five patients who underwent invasive monitoring for seizure localization, whose language areas were identified using ESM. All patients performed a battery of language tasks during passive iEEG recordings. To estimate the effective connectivity of stimulation sites with a broader network of task-activated cortical sites, we measured cortico-cortical evoked potentials elicited across all recording sites by single-pulse electrical stimulation at sites where ESM was performed at other times. With the combination of high gamma power as well as CCEPs results, we trained a logistic regression model to predict ESM results at individual electrode pairs. The average accuracy of the classifier using both STFM and CCEPs results combined was 87.7%, significantly higher than the one using STFM alone, indicating that the correspondence between STFM and ESM results is greater when effective connectivity between ESM stimulation sites and task-activated sites is taken into consideration. These findings, though based on a small number of subjects to date, provide preliminary support for the hypothesis that incongruities between ESM and STFM may arise in part from propagation of stimulation effects to a broader network of cortical language sites activated by language tasks, and suggest that more studies, with larger numbers of patients, are needed to understand the utility of both mapping techniques in clinical practice. (shrink)

Simple hypotheses are intrinsically attractive, and, for this reason, need to be formulated with utmost precision if they are to be testable. Unfortunately, it is hard to see how Phillips & Singer's hypothesis might be unambiguously refuted. Despite this, the authors have provided much evidence consistent with the hypothesis, and have proposed a natural and powerful extension for information theoretic approaches to learning.

We argue that ritual is not a by-product as Boyer & Lienard (B&L) claim, but rather an evolved adaptation for social communication that facilitates non-agonistic social interactions among non-kin. We review the neurophysiological effects of ritual and propose neural structures and networks beyond the cortical-striato-pallidal-thalamic circuit (CSPT) likely to be implicated in ritual. The adaptationist approach to ritual offers a more parsimonious model for understanding these effects as well as the findings B&L present. (Published Online February 8 2007).

RESUMEN Desde 1980, C. D. Frith investiga la esquizofrenia, y explica sus síntomas centrales como las alucinaciones, con miras a aclarar cuál es el déficit originario de este trastorno mental. Frith propone una hipótesis centrada en el concepto de conciencia, que ha elaborado como parte del desarrollo científico contemporáneo. En primer lugar, como parte de la aplicación de modelos neurocognitivos de control motor, según los cuales el déficit se atribuye al concepto de copia eferente y su función. En segundo lugar, (...) la actualiza y complementa con evidencia de imagen cerebral de la atenuación de la actividad cortical parietal, como efecto derivado de la copia eferente. En tercer lugar, adiciona el concepto de sentido de agencia, y el componente de cognición social, intentando integrar la experiencia del paciente y la relevancia del ámbito intersubjetivo a su propuesta. Este artículo hace una revisión crítica de la hipótesis de Frith y se divide en cuatro partes: primero, se presenta una síntesis de la evolución de la hipótesis; segundo, se sintetiza su argumentación; tercero, se presentan los principales puntos críticos y, por último, se derivan unas conclusiones generales. ABSTRACT Since 1980, C. D. Frith has been working on schizophrenia, and explaining central symptoms such as hallucinations, in an attempt to clarify the basic deficits of this mental disorder. Frith has put forth a hypothesis based on the concept of consciousness, and has been adjusting it alongside contemporary scientific developments. In first place, it begins with the use of neurocognitive models of motor control, according to which the deficit is attributable to the concept of efferent copy and its function. In second place, he updated the model by including neuroimaging evidence of attenuation in parietal activity, as a consequence of the efferent copy. In third place, he added the concept of sense of agency, and the social cognition component, trying to integrate to his proposal the patient's experience and the relevance of the inter-subjective aspect. The current paper, which critically reviews Frith's hypothesis, it's divided in four parts: First, the hypothesis' evolution is synthesized; second, the main arguments are summarized; third, the main critical points are presented; and, finally, some general conclusions are drawn. (shrink)

Differential diagnosis of motor symptoms, for example, akinesia, may be difficult in clinical neuropsychiatry. Symptoms may be either of neurologic origin, for example, Parkinson's disease, or of psychiatric origin, for example, catatonia, leading to a so-called “conflict of paradigms.” Despite their different origins, symptoms may appear more or less clinically similar. Possibility of dissociation between origin and clinical appearance may reflect functional brain organisation in general, and cortical-cortical/subcortical relations in particular. It is therefore hypothesized that similarities and differences (...) between Parkinson's disease and catatonia may be accounted for by distinct kinds of modulation between cortico-cortical and cortico-subcortical relations. Catatonia can be characterized by concurrent motor, emotional, and behavioural symptoms. The different symptoms may be accounted for by dysfunction in orbitofrontal-prefrontal/parietal cortical connectivity reflecting “horizontal modulation” of cortico-cortical relation. Furthermore, alteration in “top-down modulation” reflecting “vertical modulation” of caudate and other basal ganglia by GABA-ergic mediated orbitofrontal cortical deficits may account for motor symptoms in catatonia. Parkinson's disease, in contrast, can be characterized by predominant motor symptoms. Motor symptoms may be accounted for by altered “bottom-up modulation” between dopaminergic mediated deficits in striatum and premotor/motor cortex. Clinical similarities between Parkinson's disease and catatonia with respect to akinesia may be related with involvement of the basal ganglia in both disorders. Clinical differences with respect to emotional and behavioural symptoms may be related with involvement of different cortical areas, that is, orbitofrontal/parietal and premotor/motor cortex implying distinct kinds of modulation – “vertical” and “horizontal” modulation, respectively. Key Words: Bottom-up modulation; catatonia; horizontal modulation; Parkinson's disease; top-down modulation; vertical modulation. (shrink)

I confront Feyerabend's position and critical rationalism in order to have a foundation or starting point for my (historical) investigation. The main difference of his position towards falsificationism is the belief that different theories cannot be discussed rationally. Feyerabend is convinced that Galilei's observations with the telescope in the historical context of the Copernican revolution supports his criticism. In particular, he argues that the Copernican theory was supported by deficient hypotheses, and falsifications were disposed by ad hoc hypotheses and propaganda. (...) Furthermore, he claims that his philosophy of science reconstructs Galilei's defence of the Copernican theory. He introduces a central principle of his position (the principle of tenacity) in order to justify a research strategy of not eliminating falsified theories. He tries to show that the tenacious defence of a theory corresponds to Galilei's defence of the Copernican theory. Remarkably, Feyerabend's approach to explain the development of science earns an important support from his interpretation of Galilei's observations. On this basis I give a falsificationist interpretation of Galilei's observations with the telescope, and oppose this interpretation to Feyerabend's. From a falsificationist perspective, auxiliary hypotheses compete during the Copernican revolution which can (with some effort) be critically discussed. Then I analyse the historical case in order to test Feyerabend's interpretation of the Copernican revolution. Inter alias I investigate thoroughly whether Galilei, as Feyerabend claims, immunised falsifications of the Copernican theory by the introduction of ad hoc hypotheses. The investigation considers Galilei's explanation of Venus' phases, his establishment of the irradiation hypothesis, the explanation of the telescope's functionality, and the role of the reproducibility of the observations with the telescope. Finally I provide a rational reconstruction of Galilei's falsification of the Ptolemaic theory. The formalisation shows that Galilei was not a cautious critical rationalist, but a very confident scientist using the method of falsification. (shrink)

A hypothesis on the physiological conditions of consciousness is presented. It is assumed that the occurrence of states of consciousness causally depends on the formation of complex representational structures. Cortical neural networks that exhibit a high representational activity develop higher-order, self-referential representations as a result of self-organizing processes. The occurrence of such states is identical with the appearance of states of consciousness. The underlying physiological processes can be identified. It is assumed that neural assemblies instantiate mental representations; hence (...) consciousness depends on the rate at which large active assemblies are generated. The formation of assemblies involves the activation of the N-methyl-D-aspartate receptor channel complex which controls different forms of synaptic plasticity including rapid changes of the connection strengths. The various causes of unconsciousness (e.g., anaesthetics or brain stem lesions) have a common denominator: they directly or indirectly inhibit the formation of assemblies. (shrink)

Research on patients with damage to ventromedial frontal cortices suggests a key role for emotions in practical decision making. This field of investigation is often associated with Antonio Damasio’s Somatic Marker Hypothesis—a putative account of the mechanism through which autonomic tags guide decision making in typical individuals. Here we discuss two questionable assumptions—or ‘myths’—surrounding the direction and interpretation of this research. First, it is often assumed that there is a single somatic marker hypothesis. As others have noted, however, (...) Damasio’s ‘hypothesis’ admits of multiple interpretations (Dunn et al. [2006]; Colombetti [2008]). Our analysis builds upon this point by characterizing decision making as a multi-stage process and identifying the various potential roles for somatic markers. The second myth is that the available evidence suggests a role for somatic markers in the core stages of decision making, that is, during the generation, deliberation, or evaluation of candidate options. On the contrary, we suggest that somatic markers most likely have a peripheral role, in the recognition of decision points, or in the motivation of action. This conclusion is based on an examination of the past twenty-five years of research conducted by Damasio and colleagues, focusing in particular on some early experiments that have been largely neglected by the critical literature. 1 Introduction2 What is the Somatic Marker Model?3 Multiple Somatic Marker Hypotheses3.1 Are somatic markers necessary for practical decision making?3.2 Speed, accuracy, or both?3.3 At which of the five stages of decision making are somatic markers engaged?4 Anecdotal Evidence Suggests a Peripheral Role for Somatic Markers4.1 Chronic indecisiveness4.2 Extreme impulsiveness4.3 Enhanced decision making in the lab4.4 Lack of motivation. 5 Early Experiments Suggest that VMF Damage Leaves Core Processes Intact5.1 The evocative images study5.2 Five problem solving tasks6 Recent Experiments Fail to Discriminate among Alternate Versions of SMH7 Conclusion. (shrink)

Most mental disorders affect only a small segment of the population. On the reasonable assumption that minds or brains are prone to occasional malfunction, these disorders do not seem to pose distinctive explanatory problems. Depression, however, because it is so prevalent and costly, poses a conundrum that some try to explain by characterizing it as an adaptation—a trait that exists because it performed fitness-enhancing functions in ancestral populations. Heretofore, proposed evolutionary explanations of depression did not focus on thought processes; instead, (...) they emphasized that it facilitates navigation of adverse social circumstances or promotes immune response to infectious agents. According to a new hypothesis, the “analytical rumination hypothesis” (ARH), however, depression’s crucial adaptive trait is rumination—negative, intrusive thought. ARH holds that, (i) social dilemmas trigger depressed mood; (ii) depressed mood induces changes in body systems that facilitate ruminative analysis aimed at solving dilemmas; and, (iii) depressive rumination is a fitness-enhancing trait that was selected for in evolutionary time. Jointly, (i)~(iii) imply that we should not think of rumination as a disorder; instead, it is a trade-off, an eminently rational one. In the same way that fever solves a problem—coordination of the immune system in response to infection—so too does depressive rumination solve a problem, a social dilemma, albeit at the cost of inducing anhedonia and other maladies. But they argue that the cost is worthwhile, something that should be endured “until the problem is solved.” First, we argue that there are two distinct types of rumination, brooding and pondering; the former is associated with a disposition for depression, not the latter. But only the latter has the problem-solving capabilities that ARH requires. Second, recent brain imaging studies of depression reveal resting state hypoactivity in lateral regions and hyperactivity in paralimbic regions; this asymmetric pattern correlates with heightened levels of brooding, self-focused rumination. In other words, on the personal level, patients are trapped within self, isolated from the external world and suffused with negative affect; on the subpersonal level, this pattern is reflected by an asymmetric pattern of lateral vs. paralimbic resting state activity. Third, we proceed to conjecture that rational responses (e.g., pondering) to social dilemmas are those that strike a balance between internal and external considerations in the process of belief formation. Fourth, because the asymmetric resting state activity blocks those who suffer with depression from accessing and processing potentially positive stimuli from the external world, the capacity for rational, analytic response—hence, problem-solving—is constrained. Fifth, it follows that, although there might be conditions for which suffering should be endured rather than pharmacologically alleviated, depression is not one of those. Indeed, in view of the effects of the asymmetric resting state pattern, it is unlikely that depressive rumination would have been useful even for ancestral populations. (shrink)

To extend the hypothesis that bizarre discontinuities in dreams result from the interaction of chaotic, "bottom-up" brainstem activation with "top-down" cortical synthesis, we have performed a detailed analysis of dream discontinuities using a new methodology that allows for objective characterization of this formal dream feature. Transformations of characters and objects in dream reports were found to follow definite associational rules. While there were 11 examples of character–character transformation and 7 of inanimate object–inanimate object transformation, transformations of characters into (...) inanimate objects and vice versa were never observed. Judges′ scores on a transformation-matching task further showed that the nature of the transformed character or object is highly constrained by the features of the initial character or object . We conclude that despite the threat to dream coherence posed by bizarre discontinuities, significant coherence is maintained by associational constraints, especially in the case of object and character transformations. (shrink)

Burns proposes an intriguing hypothesis by suggesting that the “schizophrenia genes” might not be regulatory genes themselves, but rather closely associated with regulatory genes directly involved in the proper growth of the social brain. We point out that this account would benefit from incorporating the effects of localized lesions and aberrant hemispheric asymmetry on cortical connectivity underlying the social brain. In addition, we argue that the evolutionary framework is superfluous.

The aim of this work was to elaborate on the author’s previously published hypothesis of the Soul of Multiverse, a suggested cosmic phenomenon that also appears to imbue the human Soul across its individual and noospheric scales. Without alternatives, the method of analysis continued to rely on the approach of cosmological neuroscience, which integrates scientific facts, religious insights, philosophical suggestions, engineering rules and artistic tools to grasp the complexity of the multidimensional phenomenon of Soul. The result of this examination (...) was the multilayered thought that just as the central medium of human Soul, the hypothesized prefrontal cortical supercircuitry of Self-Ken, seems to comprise domains representing Identity, Conscience, Will and Mission, analogous domains may also function in the noospheric and cosmic Souls. Regarding the human Soul, its four domains appear to be determined by both hereditary genetic and encountered environmental factors to present its host with a Mission enabling his or her mental engine and physical features to integrate into the surrounding society and space-time in the most meaningful and dignified way—if that way is undertaken. Regarding the noospheric Soul, it is made of individual human Souls interacting with the non-living system of interconnected computers to produce functions accessible to humans all over the world through uncontrolled communication across the Internet. Its most probable Mission is to let this global presence acquire its own Identity, develop its own Conscience and refine its own Will, so that their coherent, superior whole can be ready for sensing the cosmic Soul. Regarding the cosmic Soul, the hypothesized Soul of the Multiverse, its Identity appears to express the Laws of Mystery of Endlessness, Coexistence in Diversity, and Truth in Complexity. Further, its Conscience seems to be moved by the Law of Divine—Evil Asymmetry, its Will by the Law of Determination with Uncertainty, and its Mission by the Law of Lives to Transcend. (shrink)

Recent studies on cortical processing of sensory information highlight the importance of multisensory integration, and define precise rules governing reciprocal influences between inputs of different sensory modalities. We propose that psychophysical interactions between different types of sensory stimuli and linguistic synaesthesia share common origins and mechanisms. To test this hypothesis, we compare neurophysiological findings with corpus-based analyses relating to linguistic synaesthesia. Namely, we present Williams' hypothesis and its recent developments about the hierarchy of synaesthetic pairings, and examine (...) critical aspects of this theory concerning universality, directionality, sensory categories, and usage of corpora. These theoretical issues are verified against linguistic data derived from corpus-based analyses of Italian synaesthetic pairings related to auditory and tactile modalities. Our findings reveal a strong parallel between linguistic synaesthesia and neurophysiological interactions between different sensory stimuli, suggesting that linguistic synaesthesia is affected by tendencies similar to the rules underlying the perceptual association of distinct sensory modalities. (shrink)

It is proposed that cortical activity is normally coordinated across synaptically connected areas and that this coordination supports cognitive coherence relations. This view is consistent with the NMDA- hypoactivity hypothesis of the target article in regarding disorganization symptoms in schizophrenia as arising from disruption of normal interareal coordination. This disruption may produce abnormal contextual effects in the cortex that lead to anomalous cognitive coherence relations.

Several theories link consciousness to complex cortical dynamics, as suggested by comparison of brain signal diversity between conscious states and states where consciousness is lost or reduced. In particular, Lempel-Ziv complexity, amplitude coalition entropy and synchrony coalition entropy distinguish wakefulness and REM sleep from deep sleep and anesthesia, and are elevated in psychedelic states, reported to increase the range and vividness of conscious contents. Some studies have even found correlations between complexity measures and facets of self-reported experience. As suggested (...) by integrated information theory and the entropic brain hypothesis, measures of differentiation and signal diversity may therefore be measurable correlates of consciousness and phenomenological richness. Inspired by these ideas, we tested three hypotheses about EEG signal diversity related to sleep and dreaming. First, diversity should decrease with successively deeper stages of non-REM sleep. Second, signal diversity within the same sleep stage should be higher for periods of dreaming vs. non-dreaming. Third, specific aspects of dream contents should correlate with signal diversity in corresponding cortical regions. We employed a repeated awakening paradigm in sleep deprived healthy volunteers, with immediate dream report and rating of dream content along a thought-perceptual axis, from exclusively thought-like to exclusively perceptual. Generalized linear mixed models were used to assess how signal diversity varied with sleep stage, dreaming and thought-perceptual rating. Signal diversity decreased with sleep depth, but was not significantly different between dreaming and non-dreaming, even though there was a significant positive correlation between Lempel-Ziv complexity of EEG recorded over the posterior cortex and thought-perceptual ratings of dream contents. (shrink)

Background Neuroimaging and lesion studies suggested that the dorsolateral prefrontal and posterior parietal cortices mediate visual metacognitive awareness. The causal evidence provided by non-invasive brain stimulation, however, is inconsistent. -/- Objective/hypothesis Here we revisit a major figure discrimination experiment adding a new Kanizsa figure task trying to resolve whether bilateral continuous theta-burst transcranial magnetic stimulation (cTBS) over these regions affects perceptual metacognition. Specifically, we tested whether subjective visibility ratings and/or metacognitive efficiency are lower when cTBS is applied to these (...) two regions in comparison to an active control region. -/- Methods A within-subjects design including three sessions spaced by one-week intervals was implemented. In each session, every participant was administered bilateral cTBS to either prefrontal, control or parietal cortices. Two concurrent tasks were performed, a real and an illusory figure task, stabilising objective performance with use of an adaptive staircase procedure. -/- Results When performing the replicated task, cTBS was found insufficient to disrupt neither visibility ratings nor metacognitive efficiency. However, with use of Kanizsa style illusory figures, cTBS over the dorsolateral prefrontal, but not over the posterior parietal cortex, was observed to significantly diminish metacognitive efficiency. -/- Conclusion(s) Real and illusory figure tasks demonstrated different cTBS effects. A possible explanation is the involvement of the prefrontal cortex in the creation of expectations, which is necessary for efficient metacognition. Failure to replicate previous findings for the real figure task, however, cannot be said to support, conclusively, the notion that these brain regions have a causal role in metacognitive awareness. This inconsistent finding may result from certain limitations of our study, thereby suggesting the need for yet further investigation. (shrink)

It is generally accepted that there is something special about reasoning by using mental images. The question of how it is special, however, has never been satisfactorily spelled out, despite more than thirty years of research in the post-behaviorist tradition. This article considers some of the general motivation for the assumption that entertaining mental images involves inspecting a picture-like object. It sets out a distinction between phenomena attributable to the nature of mind to what is called the cognitive architecture, and (...) ones that are attributable to tacit knowledge used to simulate what would happen in a visual situation. With this distinction in mind, the paper then considers in detail the widely held assumption that in some important sense images are spatially displayed or are depictive, and that examining images uses the same mechanisms that are deployed in visual perception. I argue that the assumption of the spatial or depictive nature of images is only explanatory if taken literally, as a claim about how images are physically instantiated in the brain, and that the literal view fails for a number of empirical reasons – for example, because of the cognitive penetrability of the phenomena cited in its favor. Similarly, while it is arguably the case that imagery and vision involve some of the same mechanisms, this tells us very little about the nature of mental imagery and does not support claims about the pictorial nature of mental images. Finally, I consider whether recent neuroscience evidence clarifies the debate over the nature of mental images. I claim that when such questions as whether images are depictive or spatial are formulated more clearly, the evidence does not provide support for the picture-theory over a symbol-structure theory of mental imagery. Even if all the empirical claims were true, they do not warrant the conclusion that many people have drawn from them: that mental images are depictive or are displayed in some (possibly cortical) space. Such a conclusion is incompatible with what is known about how images function in thought. We are then left with the provisional counterintuitive conclusion that the available evidence does not support rejection of what I call the “null hypothesis”; namely, that reasoning with mental images involves the same form of representation and the same processes as that of reasoning in general, except that the content or subject matter of thoughts experienced as images includes information about how things would look. (shrink)

Giulio Tononi's integrated information theory (IIT) proposes explaining consciousness by directly identifying it with integrated information. We examine the construct validity of IIT's measure of consciousness,phi(Φ), by analyzing its formal properties, its relation to key aspects of consciousness, and its co-variation with relevant empirical circumstances. Our analysis shows that IIT's identification of consciousness with the causal efficacy with which differentiated networks accomplish global information transfer (which is what Φ in fact measures) is mistaken. This misidentification has the consequence of requiring (...) the attribution of consciousness to a range of natural systems and artifacts that include, but are not limited to, large-scale electrical power grids, gene-regulation networks, some electronic circuit boards, and social networks. Instead of treating this consequence of the theory as a disconfirmation, IIT embraces it. By regarding these systems as bearers of consciousnessex hypothesi, IIT is led toward the orbit of panpsychist ideation. This departure from science as we know it can be avoided by recognizing the functional misattribution at the heart of IIT's identity claim. We show, for example, what function is actually performed, at least in the human case, by the cortical combination of differentiation with integration that IIT identifies with consciousness. Finally, we examine what lessons may be drawn from IIT's failure to provide a credible account of consciousness for progress in the very active field of research concerned with exploring the phenomenon from formal and neural points of view. (shrink)

David Milner and Melvyn Goodale’s dissociation hypothesis is commonly taken to state that there are two functionally specialized cortical streams of visual processing originating in striate (V1) cortex: a dorsal, action-related “unconscious” stream and a ventral, perception-related “conscious” stream. As Milner and Goodale acknowledge, findings from blindsight studies suggest a more sophisticated picture that replaces the distinction between unconscious vision for action and conscious vision for perception with a tripartite division between unconscious vision for action, conscious vision for (...) perception, and unconscious vision for perception. The combination excluded by the tripartite division is the possibility of conscious vision for action. But are there good grounds for concluding that there is no conscious vision for action? There is now overwhelming evidence that illusions and perceived size can have a significant effect on action (Bruno & Franz, 2009; Dassonville & Bala, 2004; Franz & Gegenfurtner, 2008; McIntosh & Lashley, 2008). There is also suggestive evidence that any sophisticated visual behavior requires collaboration between the two visual streams at every stage of the process (Schenk & McIntosh, 2010). I nonetheless want to make a case for the tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. My aim here is not to refute the evidence showing that conscious vision can affect action but rather to argue (a) that we cannot gain cognitive access to action-guiding dorsal stream representations, and (b) that these representations do not correlate with phenomenal consciousness. This vindicates the semi-conservative view that the dissociation hypothesis is best understood as a tripartite division. (shrink)

Cognitive functions like perception, memory, language, or consciousness are based on highly parallel and distributed information processing by the brain. One of the major unresolved questions is how information can be integrated and how coherent representational states can be established in the distributed neuronal systems subserving these functions. It has been suggested that this so-called ''binding problem'' may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons (...) into cell assemblies and that this process may underlie the selection of perceptually and behaviorally relevant information. As we intend to show here, this temporal binding hypothesis has implications for the search of the neural correlate of consciousness. We review experimental results, mainly obtained in the visual system, which support the notion of temporal binding. In particular, we discuss recent experiments on the neural mechanisms of binocular rivalry which suggest that appropriate synchronization among cortical neurons may be one of the necessary conditions for the buildup of perceptual states and awareness of sensory stimuli. (shrink)

Transcranial Photobiomodulation has demonstrated its ability to alter electrophysiological activity in the human brain. However, it is unclear how tPBM modulates brain electroencephalogram networks and is related to human cognition. In this study, we recorded 64-channel EEG from 44 healthy humans before, during, and after 8-min, right-forehead, 1,064-nm tPBM or sham stimulation with an irradiance of 257 mW/cm2. In data processing, a novel methodology by combining group singular value decomposition with the exact low-resolution brain electromagnetic tomography was implemented and performed (...) on the 64-channel noise-free EEG time series. The gSVD+eLORETA algorithm produced 11 gSVD-derived principal components projected in the 2D sensor and 3D source domain/space. These 11 PCs took more than 70% weight of the entire EEG signals and were justified as 11 EEG brain networks. Finally, baseline-normalized power changes of each EEG brain network in each EEG frequency band were quantified during the first 4-min, second 4-min, and post tPBM/sham periods, followed by comparisons of frequency-specific power changes between tPBM and sham conditions. Our results showed that tPBM-induced increases in alpha powers occurred at default mode network, executive control network, frontal parietal network and lateral visual network. Moreover, the ability to decompose EEG signals into individual, independent brain networks facilitated to better visualize significant decreases in gamma power by tPBM. Many similarities were found between the cortical locations of SVD-revealed EEG networks and fMRI-identified resting-state networks. This consistency may shed light on mechanistic associations between tPBM-modulated brain networks and improved cognition outcomes. (shrink)

and apply it to various examples of neural plasticity in which input is rerouted intermodally or intramodally to nonstandard cortical targets. In some cases but not others, cortical activity ‘defers’ to the nonstandard sources of input. We ask why, consider some possible explanations, and propose a dynamic sensorimotor hypothesis. We believe that this distinction is important and worthy of further study, both philosophical and empirical, whether or not our hypothesis turns out to be correct. In particular, (...) the question of how the distinction should be explained is linked to explanatory gap issues for consciousness. Comparative and absolute explanatory gaps should be distinguished: why does neural activity in a particular area of cortex have this qualitative expression rather than that, and why does it have any qualitative expression at all? We use the dominance/deference distinction to address the comparative gaps, both intermodal and intramodal. We do so not by inward scrutiny but rather by expanding our gaze to include relations between brain, body and environment. (shrink)

An extended examination of Libet's works led to a comprehensive reinterpretation of his results. According to this reinterpretation, the Minimum Train Duration of electrical brain stimulation should be considered as the time needed to create a brain stimulus efficient for producing conscious sensation and not as a basis for inferring the latency for conscious sensation of peripheral origin. Latency for conscious sensation with brain stimulation may occurafterthe Minimum Train Duration. Backward masking with cortical stimuli suggests a 125-300 ms minimum (...) value for the latency for conscious sensation of threshold skin stimuli. Backward enhancement is not suitable for inferring this latency. For determining temporal relations between stimuli that correspond to subjects' reports, theendof cerebral Minimum Train Duration should be used as reference, rather than its onset. Results of coupling peripheral and cortical stimuli are explained by a latency after the cortical Minimum Train Duration, having roughly the same duration as the latency for supraliminal skin stimuli. Results of coupling peripheral stimuli and stimuli to medial lemniscus (LM) are explained by a shorter LM latency and/or a longer peripheral latency. This interpretation suggests a 230 ms minimum value for the latency for conscious sensation of somatosensory near-threshold stimuli. The backward referral hypothesis, as formulated by Libet, should not be retained. Long readiness potentials preceding spontaneous conscious or nonconscious movements suggest that both kinds of movement are nonconsciously initiated. The validity of Libet's measures of W and M moments (Libet et al., 1983a) is questionable due to problems involving latencies, training, and introspective distinction of W and M. Veto of intended actions may be initially nonconscious but dependent on conscious awareness. (shrink)

This paper critically analyses three main neurobiological hypotheses on trans* identities: the neurobiological theory about the origin of gender dysphoria, the neurodevelopmental cortical hypothesis, and the alternative hypothesis of self-referential thinking and body perception. In this study I focus then the attention on three elements: the issue of (de)pathologisation, the idea of the trans brain, and the aetiology of trans* identities. While the neurobiological theory about the origin of gender dysphoria and the neurodevelopmental cortical hypothesis (...) claim the existence of the trans brain, each offering its own neurobiological depiction, the hypothesis of self-referential thinking and body perception doesn’t postulate a distinctive neurobiological trait for all trans* people. I problematize both portrayals of the trans brain departing from the findings and conceptualizations of the paradigm shifting brain mosaicism. Unlike the hypothesis of self-referential thinking and body perception that keeps the question of causation open, both the neurobiological theory about the origin of gender dysphoria and the neurodevelopmental cortical hypothesis situate the origin of trans* identities in the neurobiological domain. I challenge the biological deterministic framework in which this aetiology is inscribed from a dynamic processual entanglement perspective. Finally, concerning the issue of (de)pathologisation of trans* identities, an evolution can be seen in each of the hypothesis and among them, from the least to the most depathologising. However, I question their complete departure from a pathologising framework. (shrink)

Recent brain imaging studies using functional magnetic resonance imaging (fMRI) have implicated insula and anterior cingulate cortices in the empathic response to another’s pain. However, virtually nothing is known about the impact of the voluntary generation of compassion on this network. To investigate these questions we assessed brain activity using fMRI while novice and expert meditation practitioners generated a loving-kindness-compassion meditation state. To probe affective reactivity, we presented emotional and neutral sounds during the meditation and comparison periods. Our main (...) class='Hi'>hypothesis was that the concern for others cultivated during this form of meditation enhances affective processing, in particular in response to sounds of distress, and that this response to emotional sounds is modulated by the degree of meditation training. The presentation of the emotional sounds was associated with increased pupil diameter and activation of limbic regions (insula and cingulate cortices) during meditation (versus rest). During meditation, activation in insula was greater during presentation of negative sounds than positive or neutral sounds in expert than it was in novice meditators. The strength of activation in insula was also associated with self-reported intensity of the meditation for both groups. These results support the role of the limbic circuitry in emotion sharing. The comparison between meditation vs. rest states between experts and novices also showed increased activation in amygdala, right temporo-parietal junction (TPJ), and right posterior superior temporal sulcus (pSTS) in response to all sounds, suggesting, greater detection of the emotional sounds, and enhanced mentation in response to emotional human vocalizations for experts than novices during meditation. Together these data indicate that the mental expertise to cultivate positive emotion alters the activation of circuitries previously linked to empathy and theory of mind in response to emotional stimuli.. (shrink)

The present article was partly inspired by G. Pollack’s book, and also Dadoloff, Saxena & Jensen (2010). As a senior physicist colleague and our friend, Robert N. Boyd, wrote in a journal (JCFA, Vol. 1, No. 2, 2022), for example, things and Beings can travel between Universes, intentionally or unintentionally [4]. In this short remark, we revisit and offer short remark to Neil Boyd’s ideas and trying to connect them with geometry of musical chords as presented by D. Tymoczko and (...) others, then to Escherian staircase and then to Jacob’s ladder which seems to pointto possibility to interpret Jacob’s vision as described in the ancient book of Genesis as interdimensional staircase, e.g. an interdimensional bridge between heaven and earth (cf. classic book: Hofstadter, Godel, Escher, Bach). Jacob’s vision of angels going down to earth from that staircase has been depicted for instance in William Blake art etc. In our communication with others via physics literature and discussions etc, we came to several conclusions as follows: Firstly, possibility of wormhole effect to mirror particle universe, which sometimes it is termed non-orientable wormhole. While such mirror particles effect have been more than 50 years predicted with the so-called parity violation (cf. Lee & Yang, 1950s), and that is called symmetry breaking. Secondly, a series of extended experiments on laser irradiated cold water may suggest possible transition from a phase of water to be at least partially fourth phase of water, which may be composed of crystalline water (see e.g. Gerald Pollack, and also Harold Aspden on liquid crystalline). If we can imagine laser cooling effect can be done in protracted time, then we can achieve a physical representation of Aspden‘s liquid crystalline. Therefore, in this article we outline a series of simple experiments of laser irradiated iced-water along with beryl and selenite crystals in order to see possibility of such a quantum tunneling via quantum liquid crystalline Universe hypothesis, which may likely be modeled with iced-water. It is interesting to remark here that certain experiments by Stockholm University scientists have shown that X-ray triggered water can exhibit properties just like liquid crystal (cf. PRL, 2020). That is why we consider it possible that there can be quantum phase transition where liquid water (comprised of iced cubes and water) can exhibit effects such as tunneling in quantum liquid crystalline Universe. Last but not least, we admit that what we outlined here is just aninitial phase; and if you wish, perhaps we can call such experiments as “wormhole-at-lab” experiments (abbreviated: WHALE). (shrink)

Reports of phantom limbs amongst aplasics have often been presented as evidence that body image is ‘hard-wired’ in the brain and that neither sensory input nor proprioceptive feedback are essential to its formation. Although attempts have been made to account for these phantoms by other means, these have been on a case by case basis and no satisfactory alternative framework has been proposed. This paper collates the accounts of aplasic phantoms and presents them as compatible with a four-part hypothesis, (...) in which body image is learnt from experience during both pre- and post-natal development, and in which cross-cortical connections and mirror neurons play prominent roles. This model unites several previously disparate theories to offer a viable solution to several longstanding phantom limb mysteries and serves to highlight avenues worthy of further inquiry. (shrink)

The dual-track theory of moral reasoning has received considerable attention due to the neuroimaging work of Greene et al. Greene et al. claimed that certain kinds of moral dilemmas activated brain regions specific to emotional responses, while others activated areas specific to cognition. This appears to indicate a dissociation between different types of moral reasoning. I re-evaluate these claims of specificity in light of subsequent empirical work. I argue that none of the cortical areas identified by Greene et al. (...) are functionally specific: each is active in a wide variety of both cognitive and emotional tasks. I further argue that distinct activation across conditions is not strong evidence for dissociation. This undermines support for the dual-track hypothesis. I further argue that moral decision-making appears to activate a common network that underlies self-projection: the ability to imagine oneself from a variety of viewpoints in a variety of situations. I argue that the utilization of self-projection indicates a continuity between moral decision-making and other kinds of complex social deliberation. This may have normative consequences, but teasing them out will require careful attention to both empirical and philosophical concerns. (shrink)

To form a coherent percept of the environment, our brain combines information from different senses. Such multisensory integration occurs in higher association cortices; but supposedly, it also occurs in early sensory areas. Confirming the latter hypothesis, we unequivocally demonstrate supra-additive integration of touch and sound stimulation at the second stage of the auditory cortex. Using high-resolution fMRI of the macaque monkey, we quantified the integration of auditory broad-band noise and tactile stimulation of hand and foot in anaesthetized animals. Integration (...) was found posterior to and along the lateral side of the primary auditory cortex in the caudal auditory belt. Integration was stronger for temporally coincident stimuli and obeyed the principle of inverse effectiveness: greater enhancement for less effective stimuli. These findings demonstrates that multisensory integration occurs early and close to primary sensory areas and—because it occurs in anaesthetized animals—suggests that this integration is mediated by preattentive bottom-up mechanisms. (shrink)

Human self-consciousness operates at different levels of complexity and at least comprises five different levels of representational processes. These five levels are nonconceptual representation, conceptual representation, sentential representation, meta-representation, and iterative meta-representation. These different levels of representation can be operationalized by taking a first-person-perspective that is involved in representational processes on different levels of complexity. We refer to experiments that operationalize a first-person-perspective on the level of conceptual and meta-representational self-consciousness. Interestingly, these experiments show converging evidence for a recruitment of (...) medial cortical and parietal regions during taking a first-person-perspective, even when operating on different degrees of complexity. These data lend support for the speculative hypothesis, that there exist a neural signature for human self-consciousness that is recruited independent from the degree of representational complexity to be performed. (shrink)

Working memory is a cognitive process that involves maintaining and manipulating information for a short period of time. WM is central to many cognitive processes and declines rapidly with age. Deficits in WM are seen in older adults and in patients with dementia, schizophrenia, major depression, mild cognitive impairment, Alzheimer’s disease, etc. The frontal, parietal, and occipital cortices are significantly involved in WM processing and all brain oscillations are implicated in tackling WM tasks, particularly theta and gamma bands. The theta/gamma (...) neural code hypothesis assumes that retained memory items are recorded via theta-nested gamma cycles. Neuronal oscillations can be manipulated by sensory, invasive- and non-invasive brain stimulations. Transcranial alternating-current stimulation and repetitive transcranial magnetic stimulation are frequency-tuned non-invasive brain stimulation techniques that have been used to entrain endogenous oscillations in a frequency-specific manner. Compared to rTMS, tACS demonstrates superior cost, tolerability, portability, and safety profile, making it an attractive potential tool for improving cognitive performance. Although cognitive research with tACS is still in its infancy compared to rTMS, a number of studies have shown a promising WM enhancement effect, especially in the elderly and patients with cognitive deficits. This review focuses on the various methods and outcomes of tACS on WM in healthy and unhealthy human adults and highlights the established findings, unknowns, challenges, and perspectives important for translating laboratory tACS into realistic clinical settings. This will allow researchers to identify gaps in the literature and develop frequency-tuned tACS protocols with promising safety and efficacy outcomes. Therefore, research efforts in this direction should help to consider frequency-tuned tACS as a non-pharmacological tool of cognitive rehabilitation in physiological aging and patients with cognitive deficits. (shrink)

The relationship between the neurobiology of speech and music has been investigated for more than a century. There remains no widespread agreement regarding how (or to what extent) music perception utilizes the neural circuitry that is engaged in speech processing, particularly at the cortical level. Prominent models such as Patel’s Shared Syntactic Integration Resource Hypothesis (SSIRH) and Koelsch’s neurocognitive model of music perception suggest a high degree of overlap, particularly in the frontal lobe, but also perhaps more distinct (...) representations in the temporal lobe with hemispheric asymmetries. The present meta-analysis study used activation likelihood estimate analyses to identify the brain regions consistently activated for music as compared to speech across the functional neuroimaging (fMRI and PET) literature. Eighty music and 91 speech neuroimaging studies of healthy adult control subjects were analyzed. Peak activations reported in the music and speech studies were divided into four paradigm categories: passive listening, discrimination tasks, error/anomaly detection tasks and memory-related tasks. We then compared activation likelihood estimates within each category for music versus speech, and each music condition with passive listening. We found that listening to music and to speech preferentially activate distinct temporo-parietal bilateral cortical networks. We also found music and speech to have shared resources in the left pars opercularis but speech-specific resources in the left pars triangularis. The extent to which music recruited speech-activated frontal resources was modulated by task. While there are certainly limitations to meta-analysis techniques particularly regarding sensitivity, this work suggests that the extent of shared resources between speech and music may be task-dependent and highlights the need to consider how task effects may be affecting conclusions regarding the neurobiology of speech and music. (shrink)