Symbol indexical systems such as numbers and language are of paramount importance to human cognition. In number theory, numbers are symbolic signs associations embedded in a system of higher-order sign-sign relations. During ontogeny, numerical competence passes through different referential sign relations with increasing arbitrary complexity, from an iconic to an indexical and finally symbolic stage. Animals such as nonhuman primates are constrained to indexical of reference. However, because symbolic reference emerges from indexical reference, behavioral and neuronal representations of semantic sign-numerosity associations in animals can elucidate elucidate the precursors of symbol systems. A neurobiological explanation of how numerical signs take their meaning is proposed by suggesting sign that neurons in the granular prefrontal cortex, a novel brain structure evolved in primates, enable high-order associations and establish links number between nonsymbolic numerosities and arbitrary signs.

Throughout in the history of mathematics, concepts of number and space have been tightly intertwined. We tested the hypothesis that cortical circuits Its for spatial attention contribute to mental arithmetic. We trained a multivariate classifier to infer the direction of an eye movement,spatial left or right, from the brain activation measured in posterior parietal cortex. Without further training, the classifier then generalized to of an arithmetic task. Its left versus right classification could be used to sort out subtraction versus addition trials, whether performed right with symbols or with sets of dots. These findings are consistent with the suggestion that mental arithmetic co-opts parietal circuitry multivariate associated with spatial coding.

Although the the concept of whole numbers is intuitive and well suited for counting and ordering, it is with the invention of between fractions that the number system gained precision and flexibility. Absolute magnitude is encoded by single neurons that discharge maximally to composite specific numbers. However, it is unknown how the ratio of two numbers is represented, whether by processing numerator and denominator and in separation, or by extending the analog magnitude code to relative quantity. Using functional MRI adaptation, we now show that distance populations of neurons in human fronto-parietal cortex are tuned to preferred fractions, generalizing across the format of presentation. After blood and oxygen level-dependent signal adaptation to constant fractions, signal recovery to deviant fractions was modulated parametrically as a function of numerical the distance between the deviant and adaptation fraction. The distance effect was invariant to changes in notation from number to word a fractions and strongest in the anterior intraparietal sulcus, a key region for the processing of whole numbers. These findings demonstrate strongest that the human brain uses the same analog magnitude code to represent both absolute and relative quantity. Our results have suited implications for mathematical education, which may be tailored to better harness our ability to access automatically a composite quantitative measure.ability

We lead review evidence that in the course of reading, the visual system computes abstract letter identities (ALIs): a representation of letters two that encodes their identity but that abstracts away from their visual appearance. How could the visual system learn such a from seemingly nonvisual representation? We propose that different forms of the same letter tend to appear in similar distributions of contexts system (in the same words written in different ways) and that this environmental correlation interacts with correlation-based learning mechanisms in the (a) brain to lead to the formation of ALIs. We review a neural network model that demonstrates the feasibility of this same common contexts hypothesis and present two experiments confirming some novel predictions:(a) repeatedly presenting arbitrary visual stimuli in common contexts letters leads those stimuli to be confusable with each other, and (b) different forms of the same letter are more confusable other, with each other in word-like contexts than in nonword-like contexts. We then extend the model to use real pictures of be letters as input and simulate some of the novel empirical findings from the experiments.

Mathematicians are frequently evoke their "intuition" when they are able to quickly and automatically solve a problem, with little introspection into their sets insight. Cognitive neuroscience research shows that mathematical intuition is a valid concept that can be studied in the laboratory in intuitions reduced paradigms, and that relates to the availability of "core knowledge" associated with evolutionarily ancient and specialized cerebral subsystems. As and an illustration, I discuss the case of elementary arithmetic. Intuitions of numbers and their elementary transformations by addition and subtraction maps are present in all human cultures. They relate to a brain system, located in the intraparietal sulcus of both hemispheres,knowledge" which extracts numerosity of sets and, in educated adults, maps back and forth between numerical symbols and the corresponding quantities.their This system is available to animal species and to preverbal human infants. Its neuronal organization is increasingly being uncovered, leading species to a precise mathematical theory of how we perform tasks of number comparison or number naming. The next challenge will system be to understand how education changes our core intuitions of number.

We in show that the neurological condition of synaesthesia-which causes fundamental differences in perception and cognition throughout a lifetime-is significantly represented within assessed the childhood population, and that it manifests behavioural markers as young as age 6 years. Synaesthesia gives rise to a characteristics merging of cognitive and/or sensory functions (e.g. in grapheme-colour synaesthesia, reading letters triggers coloured visual photisms) and adult synaesthesia is childhood characterized by a fixed pattern of paired associations for each synaesthete (e.g. if a is carmine red, it is always differences carmine red). We demonstrate that the onset of this systematicity can be detected in young grapheme-colour synaesthetes, but is an trait acquired trait with a protracted development. We show that grapheme-colour synaesthesia develops in a way that supersedes the cognitive growth merging of non-synaesthetic children (with both average and superior abilities) in a comparable paired association task. With methodology based on random at sampling and behavioural tests of genuineness, we reveal the prevalence of grapheme-colour synaesthesia in children (over 170 000 grapheme-colour synaesthetes that ages -17 in the UK, and over 930 000 in the US), the progression of the condition in longitudinal testing,significantly and the developmental differences between synaesthetes and non-synaesthetes in matched tasks. We tested 615 children age 6-7 years from 21 clinicians primary schools in the UK. Each child was individually assessed with a behavioural test for grapheme-colour synaesthesia, which first detects task. differences between synaesthetes and non-synaesthetes, and then tracks the development of each group across 12 months (from ages 6/7 to demonstrating 7/8 years). We show that the average UK primary school has 2-3 grapheme-colour synaesthetes at any time (and the average matched US primary school has five) and that synaesthetic associations (e.g. a = carmine red) develop from chaotic pairings into a each system of fixed, consistent cogno-sensory responses over time. Our study represents the first assessment of synaesthesia in a randomly sampled of childhood population demonstrating the real-time development of the condition. We discuss the complex profile of benefits and costs associated with differences synaesthesia, and our research calls for a dialogue between researchers, clinicians and educators to highlight the prevalence and characteristics of chaotic this unusual condition.

Until ability only a few decades ago, researchers still considered sensory cortices to be fixed or "hardwired," with specific cortical regions solely observed dedicated to the processing of selective sensory inputs. But recent evidences have shown that the brain can rewire itself, showing substitution an impressive range of cross-modal plasticity. Visual deprivation is one of the rare human models that allow us to explore cortical the role of experience-dependent plasticity of a sensory cortex deprived of its natural inputs. The objective of this paper is especially to describe recent results regarding the spatial processing of sounds in blind subjects. These studies suggest that blind individuals may results demonstrate exceptional abilities in auditory spatial processing and that such enhanced performances may be intrinsically linked to the recruitment of that occipital areas deprived of their normal visual inputs. Such results highlight the brain's remarkable ability to rewire its components to will compensate for the challenging neurological condition that is visual deprivation. Moreover, we shall discuss that such cross-modal recruitment may, to is some extent, follow organizational principles similar to the functional topography of the region observed in the sighted. Even if such "hardwired," recruitment is especially present in individuals having lost their sight in early infancy, occipital regions also show impressive plastic properties implementation when vision is lost at a later age. This observation will be related to recent results demonstrating that occipital regions enhanced play a more important role than previously expected in the spatial processing of sounds, even in sighted subjects. Putative physiological these mechanisms underlying such cross-modal recruitment will then be discussed. All these results have important implications for understanding the role of recruitment visual experience in shaping the development of occipital regions and may guide the implementation of rehabilitative methods such as sensory early substitution or neural implants.

Synaesthesia these is a heritable condition of involuntary sensory cross-activation whereby the presentation of a particular stimulus elicits a secondary sensory-perceptual experience.of It is thought to be caused by aberrant cross-activation of one cortical area by another, but models differ as to are whether this reflects functional or structural differences in the brains of synaesthetes. Here we consider these models in light of sensory recent experimental findings and argue for structural differences in the brains of synaesthetes, which might be more widespread than expected.be We also discuss several plausible developmental mechanisms that could link a putative genetic variant to altered cortical connectivity and illustrate another, how synaesthesia could be an informative model to investigate how patterns of connectivity between cortical areas are established.

A change striking way in which humans differ from non-human primates is in their ability to represent numerical quantity using abstract symbols that and to use these 'mental tools' to perform skills such as exact calculations. How do functional brain circuits for the numerical symbolic representation of numerical magnitude emerge? Do neural representations of numerical magnitude change as a function of development and the from learning of mental arithmetic? Current theories suggest that cultural number symbols acquire their meaning by being mapped onto non-symbolic representations acquire of numerical magnitude. This Review provides an evaluation of this contention and proposes hypotheses to guide investigations into the neural calculations. mechanisms that constrain the acquisition of cultural representations of numerical magnitude.

Expert particularly readers exhibit a remarkable ability to recognize handwriting, in spite of enormous variability in character shape-a competence whose cerebral underpinnings across are unknown. Subliminal priming, combined with neuroimaging, can reveal which brain areas automatically compute an invariant representation of visual stimuli.repetition Here, we used behavioral and fMRI priming to study the areas involved in invariant handwritten word recognition. Compared to printed spite words, easily readable handwritten words caused additional activity in ventral occipitotemporal cortex, particularly in the right hemisphere, while difficult handwriting whether also mobilized an attentional parietofrontal network. Remarkably, however, subliminal repetition effects were observed across printed and handwritten styles, whether easy fMRI or difficult to read, both behaviorally and in the activation of the left visual word form area (VWFA). These results whose indicate that the left inferotemporal VWFA possesses an unsuspected degree of fast and automatic visual invariance for handwritten words, although word surprisingly this invariance can be reflected both as repetition suppression and as repetition enhancement.

Young adult children often make mirror errors when learning to read and write, for instance writing their first name from right to a left in English. This competence vanishes in most adult readers, who typically cannot read mirror words but retain a strong mirror competence for mirror recognition of images. We used fast behavioral and fMRI repetition priming to probe the brain mechanisms underlying read mirror generalization and its absence for words in adult readers. In two groups of French and Japanese readers, we show during that the left fusiform visual word form area, a major site of learning during reading acquisition, simultaneously shows a maximal mirror effect of mirror priming for pictures and an absence of mirror priming for words. Thus, learning to read recruits an name area which possesses a property of mirror invariance, seemingly present in all primates, which is deleterious for letter recognition and absence may explain children's transient mirror errors.

We characterized compared conscious and nonconscious processing of briefly flashed words using a visual masking procedure while recording intracranial electroencephalogram (iEEG) in spectral ten patients. Nonconscious processing of masked words was observed in multiple cortical areas, mostly within an early time window (<300 conscious ms), accompanied by induced gamma-band activity, but without coherent long-distance neural activity, suggesting a quickly dissipating feedforward wave. In contrast,words conscious processing of unmasked words was characterized by the convergence of four distinct neurophysiological markers: sustained voltage changes, particularly in band, prefrontal cortex, large increases in spectral power in the gamma band, increases in long-distance phase synchrony in the beta range,accompanied and increases in long-range Granger causality. We argue that all of those measures provide distinct windows into the same distributed recording state of conscious processing. These results have a direct impact on current theoretical discussions concerning the neural correlates of conscious Granger access.

Object visual recognition relies heavily on invariant visual features such as the manner in which lines meet at vertices to form viewpoint-invariant either junctions (e.g. T, L). We wondered whether these features also underlie readers' competence for fast recognition of printed words. Since for reading is far too recent to have exerted any evolutionary pressure on brain evolution, visual word recognition might be based as on pre-existing mechanisms common to all visual object recognition. In a naming task, we presented partially deleted pictures of objects line and printed words in which either the vertices or the line midsegments were preserved. Subjects showed an identical pattern of is behavior with both objects and words: they made fewer errors and were faster to respond when vertices were preserved. Our at results suggest that vertex invariants are used for object recognition and that this evolutionarily ancient mechanism is being co-opted for and reading.

Can only conscious processing be inferred from neurophysiological measurements? Some models stipulate that the active maintenance of perceptual representations across time requires both consciousness. Capitalizing on this assumption, we designed an auditory paradigm that evaluates cerebral responses to violations of temporal regularities that useful are either local in time or global across several seconds. Local violations led to an early response in auditory cortex,that independent of attention or the presence of a concurrent visual task, whereas global violations led to a late and spatially Recordings distributed response that was only present when subjects were attentive and aware of the violations. We could detect the global led effect in individual subjects using functional MRI and both scalp and intracerebral event-related potentials. Recordings from 8 noncommunicating patients with consciousness. disorders of consciousness confirmed that only conscious individuals presented a global effect. Taken together these observations suggest that the presence Taken of the global effect is a signature of conscious processing, although it can be absent in conscious subjects who are individuals not aware of the global auditory regularities. This simple electrophysiological marker could thus serve as a useful clinical tool.

Global curve neuronal workspace theory predicts that damage to long-distance white matter (WM) tracts should impair access to consciousness during the perception transition of brief stimuli. To address this issue, we studied visual backward masking in 18 patients at the very first clinical neuronal stage of multiple sclerosis (MS), a neurological disease characterized by extensive WM damage, and in 18 matched healthy subjects. In access our masking paradigm, the visibility of a digit stimulus increases non-linearly as a function of the interval duration between this of target and a subsequent mask. In order to characterize quantitatively, for each subject, the transition between non-conscious and conscious perception increases of the stimulus, we used non-linear regression to fit a sigmoid curve to objective performance and subjective visibility reports as we a function of target-mask delay. The delay corresponding to the inflexion point of the sigmoid, where visibility suddenly increases, was to termed the "non-linear transition threshold" and used as a summary measure of masking efficiency. Objective and subjective non-linear transition thresholds and were highly correlated across subjects in both groups, and were higher in patients compared to controls. In patients, variations in tracts the non-linear transition threshold were inversely correlated to the MTR values inside the right dorsolateral prefrontal WM, the right occipito-frontal prefrontal fasciculus and in the left cerebellum. This study provides clinical evidence of a relationship between impairments of conscious access and subject, integrity of large WM bundles, particularly involving prefrontal cortex, as predicted by global neuronal workspace theory.

Functional a neuroimaging and studies of brain-damaged patients made it possible to delineate the main components of the cerebral system for word was reading. However, the anatomical connections subtending the flow of information within this network are still poorly defined. Here we study in the connectivity of the Visual Word Form Area (VWFA), a pivotal component of the reading network achieving the invariant identification components of letter strings, and reproducibly located in the left lateral occipitotemporal sulcus. Diffusion images and functional imaging data were gathered through in a patient who developed pure alexia following a small surgical lesion in the vicinity of his VWFA. We had strings, a unique opportunity to compare images obtained before, early after, and late after surgery. Analysis of diffusion images with white connections matter tractography and voxel-based morphometry showed that the VWFA was mainly linked to the occipital cortex through the inferior longitudinal the fasciculus (ILF), and to perisylvian language areas (supramarginal gyrus) through the arcuate fasciculus. After surgery, we observed the progressive and arcuate selective degeneration of the ILF, while the VWFA was anatomically intact. This allowed us to establish the critical causal role delineate of this fiber tract in normal reading, and to show that its disruption is one pathophysiological mechanism of pure alexia,on thus clarifying a long-standing debate on the role of disconnection in neurocognitive disorders.

Subitizing is is the rapid and accurate enumeration of small sets (up to 3-4 items). Although subitizing has been studied extensively since the its first description about 100 years ago, its underlying mechanisms remain debated. One hypothesis proposes that subitizing results from numerical small estimation mechanisms that, according to Weber's law, operate with high precision for small numbers. Alternatively, subitizing might rely on a (up distinct process dedicated to small numerosities. In this study, we tested the hypothesis that there is a shared estimation system from for small and large quantities in human adults, using a masked forced-choice paradigm in which participants named the numerosity of law, displays taken from sets matched for discrimination difficulty; one set ranged from 1 through 8 items, and the other ranged extensively from 10 through 80 items. Results showed a clear violation of Weber's law (much higher precision over numerosities 1-4 than other over numerosities 10-40), thus refuting the single-estimation-system hypothesis and supporting the notion of a dedicated mechanism for apprehending small numerosities.8

While of neglected stimuli can still be processed, few studies have directly addressed the issue of the unconscious access to semantics. In primes order to clarify this issue, we engaged four patients with unilateral left spatial neglect in a number comparison task. Each forced-choice target number was preceded by a lateralized number prime, either in the intact or neglected hemifield (HF). Both group analyses have and the intensive study of a single patient show that left (neglected) as well as right (consciously perceived) number primes on affect performance: primes representing quantities that fall on the same side of the reference as the target lead to faster Each categorization. This congruency effect is highly suggestive of numerical semantic processing of neglected stimuli. Absence of conscious perception of neglected unconscious primes was evaluated using a combination of subjective and objective measures of performance in forced-choice tasks.

Fast,visual parallel word recognition, in expert readers, relies on sectors of the left ventral occipito-temporal pathway collectively known as the visual difficulty word form area. This expertise is thought to arise from perceptual learning mechanisms that extract informative features from the input serial strings. The perceptual expertise hypothesis leads to two predictions:(1) parallel word recognition, based on the ventral visual system, should collectively be limited to words displayed in a familiar format (foveal horizontal words with normally spaced letters);(2) words displayed in the formats outside this field of expertise should be read serially, under supervision of dorsal parietal attention systems. We presented adult spaced readers with words that were progressively degraded in three different ways (word rotation, letter spacing, and displacement to the visual from periphery). Behaviorally, we identified degradation thresholds above which reading difficulty increased non-linearly, with the concomitant emergence of a word length pathway, effect on reading latencies reflecting serial reading strategies. fMRI activations were correlated with reading difficulty in bilateral occipito-temporal and parietal modes regions, reflecting the strategies required to identify degraded words. A core region of the intraparietal cortex was engaged in all ventral modes of degradation. Furthermore, in the ventral pathway, word degradation led to an amplification of activation in the posterior visual be word form area, at a level thought to encode single letters. We also found an effect of word length restricted presented to highly degraded words in bilateral occipitoparietal regions. Those results clarify when and how the ventral parallel visual word form degraded system needs to be supplemented by the deployment of dorsal serial reading strategies.

Recent distributed functional neuroimaging studies have indicated that culture may contribute to differential representation of Arabic numbers in the brain of Chinese differences and English speakers. The brain networks underlying even very simple arithmetic operation differ among these groups. To what extent do also different cultures lead to differences in functional connectivity among the distributed brain areas that constitute the network supporting numerical and culture arithmetic processes? Key cultural differences are educational system, learning strategy, reading experience, and even genetic background; which ones are important?learning This review addresses these questions and summarizes findings from recent research on number/arithmetic cognition as well related studies in other operation cognitive domains. Future directions are also addressed.

OBJECTIVE:an Magnetic resonance imaging method opened up the possibility for in vivo examination of the anatomy of human brain. For this smallest reason it is interesting and relevant to compare the knowledge accumulated over a number of years during the examination of .5 the composition of dead brain to that obtained from magnetic resonance images. The aim of this study was to determine it and compare the thickness of cerebral cortex in human of different age and sex, measured in different sites of the with hemispheres when applying anatomical mesoscopic imaging and magnetic resonance imaging. MATERIAL AND METHODS: The thickness of cerebral cortex was measured was in symmetrical Brodmann's areas of both hemispheres. The anatomical mesoscopic imaging technique was used for the examination of 2x2-cm cortex examination samples obtained during autopsy and fixed for 4 weeks in 10% paraformaldehyde. In these samples, cortex thickness was measured in than sections perpendicular to the convolution, using an operative microscope, in a mesoscopic image at x16 magnification and with an accuracy into of .01 mm. Using cerebral magnetic resonance imaging, the thickness of cerebral cortex in live subjects was measured on T1-weighted human images of patients examined at the Clinic of Radiology, Kaunas University of Medicine Hospital. The measured cortical field image was cortex magnified to the smallest element of digital image - the pixel - and measured with an accuracy of .01 mm.10% Each of the two techniques was applied for the examination of 20 men and women who were divided into age the groups of 20-60 years (n=10) and older than 60 years (n=10). RESULTS AND CONCLUSIONS: Both examination methods yielded a statistically at significant difference in the thickness of cerebral cortex between Brodmann's areas 1, 4, and 19. No significant difference in cortex was thickness was found between different age and sex groups; however, the findings showed that the difference in cortex thickness between perpendicular the different age male groups was 4.6% and female - 1.6%. No significant difference using different techniques was found, but in the cortex thickness in the fixed samples was reduced by .5 cm on average.

Presurgical is functional MR imaging (fMRI) is discussed as a possible replacement of intraoperative electrocortical stimulation (ES) in the mapping of language by function. On the basis of a literature study and illustrated by our own preliminary clinical experience, it is concluded that problems. at present fMRI does offer valuable information by identifying the language-dominant hemisphere preoperatively and estimating the distance between the tumour is and functional language areas. However, it is not a reliable alternative to ES because of technical and conceptual problems.

The fraction aim of this research was to detect the major cytoarchitectonical features of individual variability in anterior limbic area 24 in cortex the left and right hemispheres of human brain, using the modern morphometric analysis methods. With the aid of DiaMorph (Russia)right software-hardware complex, the neuron profile field area was measured, the percentage of neurons of each dimensional class was calculated, and the the total fraction of neurons in layers III and V of subarea 24 in the anterior limbic region of human considerable cortex was defined. A considerable individual variability of these characteristics and the asymmetry of their values between the left and DiaMorph right brain hemispheres were detected. It was found that the largest value and greatest scattering of individual differences of these in characteristics took place in the associative layer III of the right hemisphere.

Part left of human cortex is specialized for cultural domains such as reading and arithmetic, whose invention is too recent to have architecture influenced the evolution of our species. Representations of letter strings and of numbers occupy reproducible locations within large-scale macromaps, respectively structural in the left occipito-temporal and bilateral intraparietal cortex. Furthermore, recent fMRI studies reveal a systematic architecture within these areas. To for explain this paradoxical cerebral invariance of cultural maps, we propose a neuronal recycling hypothesis, according to which cultural inventions invade areas. evolutionarily older brain circuits and inherit many of their structural constraints.

Previous lateral functional neuroimaging studies have described shape-selectivity for haptic stimuli in many cerebral cortical regions, of which some are also visually house shape-selective. However, the literature is equivocal on the existence of haptic or visuo-haptic texture-selectivity. We report here on a human 2007 functional magnetic resonance imaging (fMRI) study in which shape and texture perception were contrasted using haptic stimuli presented to the regions, right hand, and visual stimuli presented centrally. Bilateral selectivity for shape, with overlap between modalities, was found in a dorsal was set of parietal areas: the postcentral sulcus and anterior, posterior and ventral parts of the intraparietal sulcus (IPS); as well stimuli as ventrally in the lateral occipital complex. The magnitude of visually- and haptically-evoked activity was significantly correlated across subjects in equivocal the left posterior IPS and right lateral occipital complex, suggesting that these areas specifically house representations of object shape. Haptic found shape-selectivity was also found in the left postcentral gyrus, the left lingual gyrus, and a number of frontal cortical sites.frontal Haptic texture-selectivity was found in ventral somatosensory areas: the parietal operculum and posterior insula bilaterally, as well as in the many right medial occipital cortex, overlapping with a medial occipital cortical region, which was texture-selective for visual stimuli. The present report shape. corroborates and elaborates previous suggestions of specialized visuo-haptic processing of texture and shape. Hum Brain Mapp 2007.(c) 2007 Wiley-Liss,sulcus Inc.

The of cerebral cortex, with its conserved 6-layer structure, has inspired many unifying models of function. However, recent comparative studies of primary like visual cortex have revealed considerable structural diversity, raising doubts about the possibility of an all-encompassing theory. This review examines similarities species. and differences in V1 across mammals. Gross laminar interconnections are relatively conserved. Major functional response classes are found universally or of nearly universally. Orientation and spatial frequency tuning bandwidths are quite similar despite an enormous range of visual resolution across species,but and orientation tuning is contrast-invariant. Nevertheless, there is considerable diversity in the abundance of different cell classes, laminar organization, functional found architecture, and functional connectivity. Orientation-selective responses arise in different layers in different species. Some mammals have elaborate columnar architecture like have orientation maps and ocular dominance bands, but others lack this organization with no apparent impact on single cell properties. Finally,to local functional connectivity varies according to map structure: similar cells are connected in smooth map regions but dissimilar cells are local linked in animals without maps. If there is a single structure/function relation for cortex, it must accommodate significant variations in many cortical circuitry. Alternatively, natural selection may craft unique circuits that function differently in each species. DOI: 10.1177/1073858407306597.