We propose a theoretical model of the cerebral cortex which is based on its cellular components and integrates its different levels of organization: (1) cells have general adaptive and memorization properties; (2) cortical columns are repetitive interneuronal circuits which determine an adaptive processing specific to the cerebral cortex; (3) cortical maps effect selective combinations which are very efficient to learn basic behaviourial adaptations such as invariant recognition of forms, visually-guided hand movements, or execution of structured motor (...) programs; (4) the network between cortical areas has a global architecture which integrates successive learning experiences into coherent functions such as the human language. (shrink)

V.S. Ramachandran and William Hirstein's thought-provoking article ‘The science of art: a neurological theory of aesthetic experience’ and the accompanying commentaries raise serious questions about what a science of art is. Unfortunately this short piece will only be able to address them broadly. Overall the problems arise from the exclusion of neurological studies of artists, the exclusion of the artist's experience, and the premises of the theory, which are based on problematic valuations related to aesthetics and spirituality. With these valuations, (...) for which there is no scientific proof, the model is unable to sufficiently address the scope of what artists do and what art forms are. While it is my view that the Ramachandran and Hirstein theory is fundamentally flawed, it is likely the flaws are due to implicit assumptions rather than explicit intentions. (shrink)

Thach's target article presents a remarkable overview and integration of animal and human studies on the functions of the cerebellum and makes clear theoretical predictions for both the normal operation of the cerebellum and for the effects of cerebellar lesions in the mature human. Commentary is provided on three areas, namely, spatial navigation, implicit learning, and cerebellar agenesis to elicit further development of the themes already present in Thach's paper, [THACH].

This paper addresses a fundamental line of research in neuroscience: the identification of a putative neural processing core of the cerebral cortex, often claimed to be “canonical”. This “canonical” core would be shared by the entire cortex, and would explain why it is so powerful and diversified in tasks and functions, yet so uniform in architecture. The purpose of this paper is to analyze the search for canonical explanations over the past 40 years, discussing the theoretical frameworks (...) informing this research. It will highlight a bias that, in my opinion, has limited the success of this research project, that of overlooking the dimension of cortical development. The earliest explanation of the cerebral cortex as canonical was attempted by David Marr, deriving putative cortical circuits from general mathematical laws, loosely following a deductive-nomological account. Although Marr’s theory turned out to be incorrect, one of its merits was to have put the issue of cortical circuit development at the top of his agenda. This aspect has been largely neglected in much of the research on canonical models that has followed. Models proposed in the 1980s were conceived as mechanistic. They identified a small number of components that interacted as a basic circuit, with each component defined as a function. More recent models have been presented as idealized canonical computations, distinct from mechanistic explanations, due to the lack of identifiable cortical components. Currently, the entire enterprise of coming up with a single canonical explanation has been criticized as being misguided, and the premise of the uniformity of the cortex has been strongly challenged. This debate is analyzed here. The legacy of the canonical circuit concept is reflected in both positive and negative ways in recent large-scale brain projects, such as the Human Brain Project. One positive aspect is that these projects might achieve the aim of producing detailed simulations of cortical electrical activity, a negative one regards whether they will be able to find ways of simulating how circuits actually develop. (shrink)

While the past century of neuroscientific research has brought considerable progress in defining the boundaries of the human cerebral cortex, there are cases in which the demarcation of one area from another remains fuzzy. Despite the existence of clearly demarcated areas, examples of gradual transitions between areas are known since early cytoarchitectonic studies. Since multi-modal anatomical approaches and functional connectivity studies brought renewed attention to the topic, a better understanding of the theoretical and methodological implications of fuzzy boundaries (...) in brain science can be conceptually useful. This article provides a preliminary conceptual framework to understand this problem by applying philosophical theories of vagueness to three levels of neuroanatomical research. For the first two levels (cytoarchitectonics and fMRI studies), vagueness will be distinguished from other forms of uncertainty, such as imprecise measurement or ambiguous causal sources of activation. The article proceeds to discuss the implications of these levels for the anatomical study of connectivity between cortical areas. There, vagueness gets imported into connectivity studies since the network structure is dependent on the parcellation scheme and thresholds have to be used to delineate functional boundaries. Functional connectivity may introduce an additional form of vagueness, as it is an organizational principle of the brain. The article concludes by discussing what steps are appropriate to define areal boundaries more precisely. (shrink)

It is common to distinguish between “holist” and “reductionist” views of brain function, where the former envisions the brain as functioning as an indivisible unit and the latter as a collection of distinct units that serve different functions. Opposing reductionism, a number of researchers have pointed out that cortical network architecture does not respect functional boundaries, and the neuroanatomist V. Braitenberg proposed to understand the cerebral cortex as a “great mixing machine” of neuronal activity from sensory inputs, motor (...) commands, and intrinsically generated processes. In this paper, we offer a contextualization of Braitenberg’s point, and we review evidence for the interactions of neuronal activity from multiple sensory inputs and intrinsic neuronal processes in the cerebral cortex. We focus on new insights from studies on audiovisual interactions and on the influence of respiration on brain functions, which do not seem to align well with “reductionist” views of areal functional boundaries. Instead, they indicate that functional boundaries are fuzzy and context dependent. In addition, we discuss the relevance of the influence of sensory, proprioceptive, and interoceptive signals on cortical activity for understanding brain-body interactions, highlight some of the consequences of these new insights for debates on embodied cognition, and offer some suggestions for future studies. (shrink)

The electric activities of cortical pyramidal neurons are supported by structurally stable, morphologically complex axo-dendritic trees. Anatomical differences between axons and dendrites in regard to their length or caliber reflect the underlying functional specializations, for input or output of neural information, respectively. For a proper assessment of the computational capacity of pyramidal neurons, we have analyzed an extensive dataset of three-dimensional digital reconstructions from the NeuroMorphoOrg database, and quantified basic dendritic or axonal morphometric measures in different regions and layers of (...) the mouse, rat or human cerebral cortex. Physical estimates of the total number and type of ions involved in neuronal electric spiking based on the obtained morphometric data, combined with energetics of neurotransmitter release and signaling fueled by glucose consumed by the active brain, support highly efficient cerebral computation performed at the thermodynamically allowed Landauer limit for implementation of irreversible logical operations. Individual proton tunneling events in voltage-sensing S4 protein alpha-helices of Na+, K+ or Ca2+ ion channels are ideally suited to serve as single Landauer elementary logical operations that are then amplified by selective ionic currents traversing the open channel pores. This miniaturization of computational gating allows the execution of over 1.2 zetta logical operations per second in the human cerebral cortex without combusting the brain by the released heat. (shrink)

The cerebral cortex controls our most distinguishing higher cognitive functions. Human‐specific gene expression differences are abundant in the cerebral cortex, yet we have only begun to understand how these variations impact brain function. This review discusses the current evidence linking non‐coding regulatory DNA changes, including enhancers, with neocortical evolution. Functional interrogation using animal models reveals converging roles for our genome in key aspects of cortical development including progenitor cell cycle and neuronal signaling. New technologies, including iPS (...) cells and organoids, offer potential alternatives to modeling evolutionary modifications in a relevant species context. Several diseases rooted in the cerebral cortex uniquely manifest in humans compared to other primates, thus highlighting the importance of understanding human brain differences. Future studies of regulatory loci, including those implicated in disease, will collectively help elucidate key cellular and genetic mechanisms underlying our distinguishing cognitive traits. (shrink)

The materialist critics argue that insuperable difficulties are encountered by the hypothesis that immaterial mental events such as thinking can act in any way on material structures such as neurons of the cerebral cortex, as is diagrammed in Fig. 8. Such a presumed action is alleged to be incompatible with the conservation laws of physics, in particular of the First Law of Thermodynamics. This objection would certainly be sustained by 19th century physicists and by neuroscientists and philosophers who (...) are still ideologically in the physics of the 19th century, not recognizing the revolution wrought by quantum physicists in the 20th century. Unfortunately it is rare for a quantum physicist to dare an intrusion into the brain-mind problem. But in a recent book the quantum physicist Margenau (1984) makes a fundamental contribution. It is a remarkable transformation from 19th century physics to be told (p. 22): "that some fields, such as the probability field of quantum mechanics carry neither energy nor matter." He goes on (p. 96) to state: "In very complicated physical systems such as the brain, the neurons and sense organs, whose constituents are small enough to be governed by probabilistic quantum laws, the physical organ is always poised for a multitude of possible changes, each with a definite probability; if one change takes place that requires energy, or more or less energy than another, the intricate organism furnishes it automatically. Hence, even if the mind has anything to do with the change, that is if there is a mind-body interaction, the mind would not be called upon to furnish energy." In summary (p. 97) Margenau states that: "The mind may be regarded as a field in the accepted physical sense of the term. But it is a nonmaterial field; its closest analogue is perhaps a probability field. It cannot be compared with the simpler nonmaterial fields that require the presence of matter (e.g. gravity) nor does it necessarily have a definite position in space. And so far as present evidence goes it is not an energy field in any physical sense, nor is it required to contain energy in order to account for all known phenomena in which mind interacts with brain". In formulating more precisely the dualist hypothesis of mind-brain interaction, the initial statement is that the whole world of mental events (World 2) has an existence as autonomous as the world of matter-energy (World I ) (Fig. 1). The present interactionist hypothesis does not relate to these ontological problems, but merely to the mode of action of mental events on neural events, that is of the nature of the downward arrows across the frontier in Fig. 8. Following Margenau (1984) the hypothesis is that mind-brain interaction is analogous to a probability field of quantum mechanics, which has neither mass nor energy, yet can cause effective action at microsites. More specifically it is proposed that the mental concentration involved in intentions (Figs. 7, 8) or attention (Fig. 4) or planned thinking (Figs. 5, 6) can cause neural events by a process analogous to the probability fields of quantum mechanics. -/- We can ask: what neural events could be appropriate recipients for mental fields that are analogous to quantal probability fields? Already we may have the answer in recent discoveries on the nature of the synaptic mechanism whereby one nerve cell communicates with another. (shrink)

General psychopathology and cognition are likely to have a bidirectional influence on each other. Yet, the relationship between brain structure, psychopathology, and cognition remains unclear. This brief report investigates the association between structural properties of the cerebral cortex [surface area, cortical thickness, intracortical myelination indexed by the T1w/T2w ratio, and neurite density assessed by restriction spectrum imaging ] with general psychopathology and cognition in a sample of children from the Adolescent Brain Cognitive Development study. Higher levels of psychopathology (...) and lower levels of cognitive ability were associated with a smaller cortical surface area. Inter-regionally—across the cerebral cortex—the strength of association between an area and psychopathology is strongly correlated with the strength of association between an area and cognition. Taken together, structural deviations particularly observed in the cortical surface area influence both psychopathology and cognition. (shrink)

The network model of EEG formation has revealed a unified mechanism for disparate EEG phenomena: for various reactions as well as for ontogenetic and phylogenetic differences. EEG rhythmicity was shown to be an external manifestation of the functioning of the intracortical stabilizing system which provides normal informational operations in the cerebral cortex.

Background: We like to think about sexual activity as something fixed, basic and primal. However, this does not seem to fully capture reality. Even when we relish sex, we may be capable of mentalizing, talking, voluntarily postponing orgasm, and much more. This might indicate that the central control mechanisms of sexual activity are quite flexible and susceptible to learning mechanisms, and that cortical brain areas play a critical part. Objective: This study aimed to identify those cortical areas and mechanisms most (...) consistently implicated in sexual activity. Design: A comprehensive review of the human functional neuroimaging literature on sexual activity, i.e. genital stimulation and orgasm, is made. Results: Genital stimulation recruits the classical somatosensory matrix, but also areas far beyond that. The posterior insula may be particularly important for processing input from the engorged penis and coordinating penile responses. Extrastriate visual cortex tracks sexual arousal and responds to genital stimulation even when subjects have their eyes closed. The ventromedial prefrontal cortex is also tightly coupled to sexual arousal, but low activity in this area predicts high sexual arousal. Conclusion: This review has indicated cortical sites where activity is moderated by tactile genital inflow and high sexual arousal. Behavioral implications are discussed and where possible the relevance for learning mechanisms is indicated. Overall, it is clear that the cerebral cortex has something to say about sexual activity. Keywords: functional neuroimaging; insula; ventromedial prefrontal cortex; extrastriate visual cortex; penis; clitoris; orgasm (Published: 15 March 2012) Citation: Socioaffective Neuroscience & Psychology 2012, 2 : 17337 - DOI: 10.3402/snp.v2i0.17337. (shrink)

0. Introduction The past decade has seen Cognitive Linguistics (CL) emerge as an important, exciting and promising theoretical alternative to Chomskyan approaches to the study of language. Even so, sheer numbers and institutional inertia make it the case that most current neurolinguistic research either assumes that the Chomskyan formalist story is more or less correct (and thus that the task of neurolinguistics is to determine how the brain implements GB, for instance), or that the there are two possibilities, Chomskyanism or (...) associationism/connectionism, and that the task of neurolinguistics is to discover which is really the way the brain does it. In either case, the theoretical apparatus of CL is not being explored by neurolinguistics, and hence the promise CL holds for making genuine fruitful contact with theoretical neurobiology is not materializing as quickly as one might hope. This paper is an attempt to make some initial steps at fulfilling this promise. (shrink)

Applying Behrendt & Young's (B&Y's) model of thalamocortical synchrony to complex visual hallucinations in neurodegenerative disorders, such as dementia with Lewy bodies and progressive supranuclear palsy, leads us to propose that the primary pathology may be cortical rather than thalamic. Additionally, the extinction of active hallucinations by eye closure challenges their conception of the role of reduced sensory input.

Retroviral lineage tracing experiments suggest that the cortical ventricular zone is composed of a mixture of precursor cell types. The majority generate a single cell type (neurones, astrocytes or oligodendrocytes) and the remainder generate neurones and a single type of glial cell. Pluripotential precursor cells, that have the ability to generate all three cell types, are not observed. A recent paper, however, reports that when single ventricular zone cells are cultured in isolation, a small percentage of these cells are pluripotential(1). (...) This review will discuss what this knowledge tells us about cortical development. (shrink)