A fundamental question in visual neuroscience is: Why are the response properties of visual neurons as they are? A modern approach to this problem emphasizes the importance of adaptation to ecologically valid input, and it proceeds by modeling statistical regularities in ecologically valid visual input (natural images). A seminal model was linear sparse coding, which is equivalent to independent component analysis (ICA), and provided a very good description of the receptive fields of simple cells. Further models based on modeling (...) residual dependencies of the ‘‘independent” components have later been introduced. These models lead to emergence of further properties of visual neurons: the complex cell receptive fields, the spatial organization of the cells, and some surround suppression and Gestalt effects. So far, these models have concentrated on the response properties of neurons, but they hold great potential to model various forms of inference and learning. (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 (...) class='Hi'>cortical populations for influence on the workspace is effected by a combination of mutual inhibition and top-down amplification. (shrink)

Phillips & Singer's compelling presentation is weakest in its demonstration of commonalities between sensory plasticity and higher forms of learning and behavior. We propose that available data on schizophrenia can provide such evidence, because of the presence of impairments in a number of functions central to their model, and strong relationships between these dysfunctions and behavior.

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)

The paper argues that the rich cognitive abilities of humans are the result of a unique functional system in the human brain which is absent in the nonhuman brain. This "frontal feedback system" is suggested to have evolved in the transition from the great apes to humans and is a product of a reversal in the preferred direction of information flow in the human cortex due to the phylogenetic enlargement of the human frontal lobe. The frontal feedback system forms an (...) autonomous functional unit in the cortex whereby action-schemes in frontal cortices continually create fictitious sensory scenarios in posterior sensory cortices by manipulating the release of sensory representations there. These internal scenarios are created free of environmental constraints and reflect the human's internal cognitive and language processes. Nonhumans do not have a frontal feedback system and their internal cognitive processes are stimulus-bound. Evidence in support of the proposal is presented and some implications of the frontal feedback model for human experience are discussed. (shrink)

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)

Measuring event-related potentials (ERPs) has been fundamental to our understanding of how language is encoded in the brain. One particular ERP response, the N400 response, has been especially influential as an index of lexical and semantic processing. However, there remains a lack of consensus on the interpretation of this component. Resolving this issue has important consequences for neural models of language comprehension. Here we show that evidence bearing on where the N400 response is generated provides key insights into what (...) it reflects. A neuroanatomical model of semantic processing is used as a guide to interpret the pattern of activated regions in functional MRI, magnetoencephalography and intracranial recordings that are associated with contextual semantic manipulations that lead to N400 effects. (shrink)

Transient global amnesia is a benign memory disorder with etiologies that have been debated for a long time. The prevalence of stressful events before a TGA attack makes it hard to overlook these precipitating factors, given that stress has the potential to organically effect the brain. Cortical spreading depression was proposed as a possible cause decades ago. Being a regional phenomenon, CSD seems to affect every aspect of the micro-mechanism in maintaining the homeostasis of the central nervous system. Corresponding (...) evidence regarding hemodynamic and morphological changes from TGA and CSD have been accumulated separately, but the resemblance between the two has not been systematically explored so far, which is surprising especially considering that CSD had been confirmed to cause secondary damage in the human brain. Thus, by deeply delving into the anatomic and electrophysiological properties of the CNS, the CSD-TGA model may render insights into the basic pathophysiology behind the façade of the enigmatic clinical presentation. (shrink)

An exploration is given of neural network features now being uncovered in cortical processing which begins to go a little way to help bridge the ''Explanatory Gap'' between phenomenal consciousness and correlated brain activity. A survey of properties suggested as being possessed by phenomenal consciousness leads to a set of criteria to be required of the correlated neural activity. Various neural styles of processing are reviewed and those fitting the criteria are selected for further analysis. One particular processing style, (...) in which semiautonomous and long-lasting cortical activity ''bubbles'' are created by input, is selected as being the most appropriate. Further experimental criteria are used to help narrow the possible neural styles involved. This leads to a class of neural models underpinning phenomenal consciousness and to a related set of testable predictions. (shrink)

In amblyopia, abnormal visual experience during development leads to an enduring loss of visual acuity in adulthood. Physiological studies in animal models suggest that intracortical GABAergic inhibition may mediate visual deficits in amblyopia. To better understand the relationship between visual cortical γ-aminobutyric acid (GABA) and perceptual suppression in persons with amblyopia (PWA), we employed magnetic resonance spectroscopy (MRS) to quantify GABA levels in both PWA and normally-sighted persons (NSP). In the same individuals, we obtained psychophysical measures of perceptual (...) suppression for a variety of ocular configurations. In PWA, we found a robust negative correlation between the depth of amblyopia (the difference in visual acuity between the amblyopic and non-amblyopic eyes) and GABA concentration that was specific to visual cortex and was not observed in a sensorimotor cortical control region. Moreover, lower levels of visual cortical GABA were associated with weaker perceptual suppression of the fellow eye by the amblyopic eye and stronger suppression of the amblyopic eye by the fellow eye. Taken together, our findings provide evidence that intracortical GABAergic inhibition is an important component of the pathology of human amblyopia and suggest possible therapeutic interventions to restore vision in the amblyopic eye through enhancement of visual cortical GABAergic signaling in PWA. (shrink)

Isolated feedforward networks (FFNs) of spiking neurons have been studied extensively for their ability to propagate transient synchrony and asynchronous firing rates, in the presence of activity independent synaptic background noise (Diesmann et al., 1999; van Rossum et al., 2002). In a biologically realistic scenario, however, the FFN should be embedded in a recurrent network, such that the activity in the FFN and the network activity may dynamically interact. Previously, transient synchrony propagating in an FFN was found to destabilize the (...) dynamics of the embedding network (Mehring et al., 2003). Here, we show that by modeling synapses as conductance transients, rather than current sources, it is possible to embed and propagate transient synchrony in the FFN, without destabilizing the background network dynamics. However, the network activity has a strong impact on the type of activity that can be propagated in the embedded FFN. Global synchrony and high firing rates in the embedding network prohibit the propagation of both, synchronous and asynchronous spiking activity. In contrast, asynchronous low-rate network states support the propagation of both, synchronous spiking and asynchro- nous, but only low firing rates. In either case, spiking activity tends to synchronize as it propagates, challenging the feasibility to transmit information in asynchronous firing rates. Finally, asynchronous network activity allows to embed more than one FFN, with the amount of cross talk depending on the degree of overlap in the FFNs. This opens the possibility of computational mechanisms using transient synchrony among the activities in multiple FFNs. (shrink)

Despite the growing research and theoretical formulations tied to memory storage within the brain, the role of cortical columns has received relatively little attention. The current paper presents a theoretical formulation based on cortical columns as the binary units that contain all cortical information, and how memory and learning may occur based on the interaction patterns of columns. The described model is an extension of Lurian views, and suggests higher functions to result from the interaction of five (...) systems. Specific mechanisms by which the thalamus and cortex interact to create long term memory formation are delineated. There is the suggestion of two distinct, but interactive, sensory–cortical memory systems, one for factual/generic memories and the other for episodic/personal memories. Hemispheric lateralization of function is explained on the basis of speed and quantity of columnar activation. Conclusions focus on recent technological advances that may allow cortical models to be testable in the near future. (shrink)

Functional roles for cortical synchronization in self-organizing neural networks are described. These properties are best understood by models that link brain to behavior. Synchrony can express itself differently in cortical circuits that perform different behavioral tasks. Cortical temporal properties that seem inexplicable by synchrony are also mentioned.

The present study is an attempt to relate the multicomponent response of the cytoskeleton (CSK), evaluated in twisted living adherent cells, to the heterogeneity of the cytoskeletal structure - evaluated both experimentally by means of 3D reconstructions, and theoretically considering the predictions given by two tensegrity models composed of (four and six) compressive elements and (respectively 12 and 24) tensile elements. Using magnetic twisting cytometry in which beads are attached to integrin receptors linked to the actin CSK of living (...) adherent epithelial cells, we specifically measured the elastic CSK response at quasi equilibrium state and partitioned this response in terms of cortical and cytosolic contributions with a two-component model (i.e., a series of two Voigt bodies). These two CSK components were found to be prestressed and exhibited a stress-hardening response which both characterize tensegrity behaviour with however significant differences: compared to the cytosolic component, the cortical cytoskeleton appears to be a faster responding component, being a less prestressed and easily deformable structure. The discrepancies in elastic behaviour between the cortical and cytosolic CSK components may be understood on the basis of prestress tensegrity model predictions, given that the length and number of constitutive actin elements are taken into account. (shrink)

I support Pylyshyn's skepticism that visual imagery reflects a re-activation of the spatial layout of active neurons embedded within a topographical cortical map of visual space. The pickup of visual information via successive eye movements presents one problem and the two visual systems model poses another difficulty.

About one third of patients with epilepsy have seizures refractory to the medical treatment. Electrical stimulation mapping is the gold standard for the identification of “eloquent” areas prior to resection of epileptogenic tissue. However, it is time-consuming and may cause undesired side effects. Broadband gamma activity recorded with extraoperative electrocorticography during cognitive tasks may be an alternative to ESM but until now has not proven of definitive clinical value. Considering their role in cognition, the alpha and beta bands could further (...) improve the identification of eloquent cortex. We compared gamma, alpha and beta activity, and their combinations for the identification of eloquent cortical areas defined by ESM. Ten patients with intractable focal epilepsy participated in a delayed-match-to-sample task, where syllable sounds were compared to visually presented letters. We used a generalized linear model approach to find the optimal weighting of each band for predicting ESM-defined categories and estimated the diagnostic ability by calculating the area under the receiver operating characteristic curve. Gamma activity increased more in eloquent than in non-eloquent areas, whereas alpha and beta power decreased more in eloquent areas. Diagnostic ability of each band was close to 0.7 for all bands but depended on multiple factors including the time period of the cognitive task, the location of the electrodes and the patient’s degree of attention to the stimulus. We show that diagnostic ability can be increased by 3–5% by combining gamma and alpha and by 7.5–11% when gamma and beta were combined. We then show how ECoG power modulation from cognitive testing can be used to map the probability of eloquence in individual patients and how this probability map can be used in clinical settings to optimize ESM planning. We conclude that the combination of gamma and beta power modulation during cognitive testing can contribute to the identification of eloquent areas prior to ESM in patients with refractory focal epilepsy. (shrink)

In cortical neurones, analogue dendritic potentials are thought to be encoded into patterns of digital spikes. According to this view, neuronal codes and computations are based on the temporal patterns of spikes: spike times, bursts or spike rates. Recently, we proposed an ‘action potential waveform code’ for cortical pyramidal neurones in which the spike shape carries information. Broader somatic action potentials are reliably produced in response to higher conductance input, allowing for four times more information transfer than spike (...) times alone. This information is preserved during synaptic integration in a single neurone, as back‐propagating action potentials of diverse shapes differentially shunt incoming postsynaptic potentials and so participate in the next round of spike generation. An open question has been whether the information in action potential waveforms can also survive axonal conduction and directly influence synaptic transmission to neighbouring neurones. Several new findings have now brought new light to this subject, showing cortical information processing that transcends the classical models. BioEssays 29: 178–187, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Male sexual arousal (SA) has been known as a multidimensional experience involving closely interrelated and coordinated neurobehavioral components that rely on widespread brain regions. Recent functional neuroimaging studies have shown relation between abnormal/altered dynamics in these circuits and male sexual dysfunction. However, alterations in the topological1 organization of structural brain networks in male sexual dysfunction are still unclear. Here, we used graph theory2 to investigate the topological properties of large-scale structural brain networks, which were constructed using inter-regional correlations of (...) class='Hi'>cortical thickness between 78 cortical regions (subcortical regions were not included due to the used cortical surface model) in 40 patients with psychogenic erectile dysfunction (pED) and 39 normal controls. Compared with normal controls, pED patients exhibited a less optimal global topological organization with reduced global and increased local efficiencies. Our results suggest disrupted neural integration among distant brain regions in pED patients, consistent with previous reports of impaired white matter structure and abnormal functional integrity in pED. Additionally, disrupted global network topology in pED was observed to be primarily relevant to altered subnetwork and nodal properties within the networks mediating the cognitive, motivational and inhibitory processes of male SA, possibly indicating disrupted integration of these networks in the whole brain networks and might account for pED patients’ abnormal cognitive, motivational and inhibitory processes for male SA. In total, our findings provide evidence for disrupted integrity in large-scale brain networks underlying the neurobehavioral processes of male SA in pED and provide new insights into the understanding of the pathophysiological mechanisms of pED. (shrink)

Some dichotomies related to modeling electrocortical activities are analyzed. Attractor neural networks versus biologically motivated models, near-equilibrium versus nonequilibrium processes, linear and nonlinear dynamics, stochastic and chaotic patterns, local and global scale simulation of cortical activities are discussed.

The purposes of this article were to obtain mechanical properties of the dry femur cortical bone samples through a tensile load and stress concentration factor approach and to provide simulations to predict experimental behaviors based on manipulations of certain properties and parameters of the biomaterial. Since bone samples have characteristics and geometries, the development of a mathematical model was necessary to describe the combination of stresses interacting in the bone when a tension load is applied. The samples have average (...) diameters and lengths of 0.5 and 2 inches respectively and were tested using a 10 kN Universal Tensile Machine to determine mechanical properties such as yield and ultimate stress, young module, and fracture, among others. Several simulations were conducted to evaluate failure criteria like “Von Mises”, “Tresca” and “Tsai-Wu”. Finally, was concluded that 83% of the data obtained from the 22 samples observed in the “Stress-Strain” charts showed a directly proportional relationship. (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)

We present simulation results of an olfactory cortex model complementing the results presented in Wright & Liley's target article. We show how the cortical dynamics as expressed in EEG can be regulated by neuromodulation and discuss how the system can attain global stability without cortical-subcortical interaction, as presumed necessary by Wright & Liley. Network structure is shown to be crucial.

The paper argues that cognitive states of biological systems are inherently temporal. Three adequacy conditions for neuronal models of representation are vindicated: the compositionality of meaning, the compositionality of content, and the co-variation with content. Classicist and connectionist approaches are discussed and rejected. Based on recent neurobiological data, oscillatory networks are introduced as a third alternative. A mathematical description in a Hilbert space framework is developed. The states of this structure can be regarded as conceptual representations satisfying the three (...) conditions. (shrink)

As many as two million people in the United Kingdom repeatedly see people, animals, and objects that have no objective reality. Hallucinations on the border of sleep, dementing illnesses, delirium, eye disease, and schizophrenia account for 90% of these. The remainder have rarer disorders. We review existing models of recurrent complex visual hallucinations (RCVH) in the awake person, including cortical irritation, cortical hyperexcitability and cortical release, top-down activation, misperception, dream intrusion, and interactive models. We provide (...) evidence that these can neither fully account for the phenomenology of RCVH, nor for variations in the frequency of RCVH in different disorders. We propose a novel Perception and Attention Deficit (PAD) model for RCVH. A combination of impaired attentional binding and poor sensory activation of a correct proto-object, in conjunction with a relatively intact scene representation, bias perception to allow the intrusion of a hallucinatory proto-object into a scene perception. Incorporation of this image into a context-specific hallucinatory scene representation accounts for repetitive hallucinations. We suggest that these impairments are underpinned by disturbances in a lateral frontal cortex–ventral visual stream system. We show how the frequency of RCVH in different diseases is related to the coexistence of attentional and visual perceptual impairments; how attentional and perceptual processes can account for their phenomenology; and that diseases and other states with high rates of RCVH have cholinergic dysfunction in both frontal cortex and the ventral visual stream. Several tests of the model are indicated, together with a number of treatment options that it generates. Key Words: Blindness; Charles Bonnet; cholinergic; cortical release; delirium; dementia; dream intrusion; hallucination; Perception and Attention Deficit (PAD) model; schizophrenia. (shrink)

Both the global workspace theory and Block’s distinction between phenomenal and access consciousness, are central in the current debates about consciousness and the neural correlates of consciousness. In this article, a unifying global workspace model for phenomenal and access consciousness is proposed. In the model, recurrent neural interactions take place in distinct yet interacting access and phenomenal brain loops. The effectiveness of feedback signaling onto sensory cortical maps is emphasized for the neural correlates of phenomenal consciousness. Two forms of (...) top-down attention, attention for perception and attention for access, play differential roles for phenomenal and access consciousness. The model is implemented in a neural network form, with the simulation of single and multiple visual object processing, and of the attentional blink. (shrink)

J. G. Taylor advances an empirically testable local neural network model to understand the neural correlates of phenomenal experience. Taylor's model is better able to explain the presence and unity of phenomenal consciousness which support the idea that consciousness is coherent, undivided, and centered. However, Taylor fails to offer a satisfactory explanation of the nonlinear relationship between local and global neural systems. In addition, the ontological assumptions that PE is immediate, intrinsic, and incorrigible limit an understanding of the different experiential (...) forms consciousness takes during neurobehavioral development. Recent studies suggest that neurobehavioral development is discontinuous and that judgment emerges under conditions of uncertainty to render feeling and perception in equivalent terms of energy and behavior. Approaching the problem of phenomenal experience from a developmental perspective may help resolve the paradox of feeling infinitely close as well as distant from one's self. (shrink)

Hominid-like morphology in habiline cranial endocasts does not necessarily imply the presence of language capacity. The cortical zone in question is not associated exclusively with language in humans, and its emergence in habilines might indicate the evolution of other cognitive functions special to humans that were preconditions for the later evolution of language.

Behrendt & Young's (B&Y's) theory offers a potentially important perspective on the neurobiology of schizophrenia, but it remains incomplete. In addition to bottom-up contributions, such as those associated with disturbances in sensory constraints on cognitive processes, a comprehensive model requires the integration of the consequences of abnormal top-down modulation of input processing for the evolution of “underconstrained” perceptions. Dysfunctional cholinergic modulation of input functions represents a necessary mechanism for the generation of false perceptions.

Meditation comprises a series of practices mainly developed in eastern cultures aiming at controlling emotions and enhancing attentional processes. Several authors proposed to divide meditation techniques in focused attention and open monitoring techniques. Previous studies have reported differences in brain networks underlying FA and OM. On the other hand common activations across different meditative practices have been reported. Despite differences between forms of meditation and their underlying cognitive processes, we propose that all meditative techniques could share a central process that (...) would be supported by a core network for meditation since their general common goal is to induce relaxation, regulating attention and developing an attitude of detachment from one’s own thoughts. To test this hypothesis, we conducted a quantitative meta-analysis based on activation likelihood estimation of 10 neuroimaging studies on different meditative techniques to evidence the core cortical network subserving meditation. We showed activation of basal ganglia , limbic system and medial prefrontal cortex . We discuss the functional role of these structures in meditation and we tentatively propose a neurocognitive model of meditation that could guide future research. (shrink)

The detection and categorization of animate motions is a crucial task underlying social interaction and perceptual decision making. Neural representations of perceived animate objects are partially located in the primate cortical region STS, which is a region that receives convergent input from intermediate-level form and motion representations. Populations of STS cells exist which are selectively responsive to specific animated motion sequences, such as walkers. It is still unclear how and to what extent form and motion information contribute to the (...) generation of such representations and what kind of mechanisms are involved in the learning processes. The article develops a cortical model architecture for the unsupervised learning of animated motion sequence representations. We demonstrate how the model automatically selects significant motion patterns as well as meaningful static form prototypes characterized by a high degree of articulation. Such key poses are selectively reinforced during learning through a cross talk between the motion and form processing streams. Furthermore, we show how sequence-selective representations are learned in STS by fusing static form and motion input from the segregated bottom-up driving input streams. Cells in STS, in turn, feed their activities recurrently to their input sites along top-down signal pathways. We show how such learned feedback connections enable predictions about future input as anticipation generated by sequence-selective STS cells. Network simulations demonstrate the computational capacity of the proposed model by reproducing several experimental findings from neurosciences and by accounting for recent behavioral data. (shrink)

J. G. Taylor advances an empirically testable local neural network model to understand the neural correlates of phenomenal experience. Taylor's model is better able to explain the presence (i.e., persistence, latency, and seamlessness) and unity of phenomenal consciousness which support the idea that consciousness is coherent, undivided, and centered. However, Taylor fails to offer a satisfactory explanation of the nonlinear relationship between local and global neural systems. In addition, the ontological assumptions that PE is immediate, intrinsic, and incorrigible limit an (...) understanding of the different experiential forms consciousness takes during neurobehavioral development. Recent studies suggest that neurobehavioral development is discontinuous and that judgment emerges under conditions of uncertainty to render feeling and perception in equivalent terms of energy and behavior. Approaching the problem of phenomenal experience from a developmental perspective may help resolve the paradox of feeling infinitely close as well as distant from one's self. (shrink)

A geometrical model is proposed that describes the emergence of a primordium at the shoot apex in Dicotyledons. It is based on recent fundamental results on plant morphogenesis, viz.: – the emergence is preceded by the reorganization of the microtubules of the cortical cytoskeleton, leading to a new orientation of the synthesis of the cell wall microfibrils; – the resulting global stress is related to the general orientation of the cell growth.