Left Occipitotemporal Area Research Articles

Mentalizing and self-other distinction in visual perspective taking: the analysis of temporal neural processing using high-density EEG.

This high density EEG report dissects the neural processing in the visual perspective taking using four experimental comparisons (Arrow, Avatar and Self, Other). Early activation differences occurred between the Avatar and the Arrow condition in primary visual pathways concomitantly with alpha and beta phase locked responses predominant in the Avatar condition. In later time points, brain activation was stronger for the Avatar condition in paracentral lobule of frontal lobe. When taking the other's perspective, there was an increased recruitment of generators in the occipital and temporal lobes and later on in mentalizing and salience networks bilaterally before spreading to right frontal lobe subdivisions. Microstate analysis further supported late recruitment of the medial frontal gyrus and precentral lobule in this condition. Other perspective for the Avatar only showed a strong beta response located first in left occipito-temporal and right parietal areas, and later on in frontal lobes. Our EEG data support distinct brain processes for the Avatar condition with an increased recruitment of brain generators that progresses from primary visual areas to the anterior brain. Taking the other's perspective needs an early recruitment of neural processors in posterior areas involved in theory of mind with later involvement of additional frontal generators.

A label isn't just a label: Brief training leads to label-dependent visuo-cortical processing in adults

The current study examines the extent to which hearing individual-level names (e.g., Jimmy) and category-level labels (e.g., Hitchel) paired with novel objects impacts neural responses across a brief (6 min) learning period. Event-related Potentials (ERPs) were recorded while adult participants (n = 44) viewed and heard exemplars of two different species of named novel objects. ERPs were examined for each labeling condition and compared across the first and second half of the learning trials (∼3 min/half). Mean amplitude decreased for the P1 and increased for the N170 from the first to the second half of trials. The decrease in P1 was right lateralized. In addition, the P1 amplitude recorded over right occipitotemporal regions was greater than left occipitotemporal areas, but only for objects paired with individual-level labels. Category-level labels did not show regional P1 differences. The N250 component was greatest over the right occipitotemporal region and was enhanced for objects labeled with individual-level relative to category-level names during the second half of trials. Overall, these findings highlight the unfolding of label-dependent visual processing across a short training period in adults. The results suggest that linguistic labels have an important, top-down impact, on visual processing and that label specificity shapes visuo-cortical responses within a 6-min learning period.

Alexia and agraphia in Japanese

AbstractDissociated performance in the reading/writing of kanji (morphogram) and kana (phonogram) in alexia and agraphia in Japanese has attracted attention because kanji and kana differently convey semantics, orthography, and phonology. Although the dissociation between kanji and kana is relative, but not absolute, detailed case studies, in addition to recent neuroimaging and neurophysiological studies, have revealed the partially separable mechanisms of the kanji and kana writing systems. Kanji words are processed mainly, not exclusively, via the orthographic–semantic route, and kana words are processed via both orthographic–semantic and phonological routes. Pure alexia with lesions in the left medial occipital lobe and splenium shows alexia for both kanji and kana, but at the chronic stage, alexia for either kanji or kana may remain depending on the compensatory mechanism. The left occipitotemporal area is important for reading/writing. The slightly different location and extent of lesions are associated with distinct symptoms: kanji alexia with the lesion in the mid‐fusiform gyrus (visual word form area; VWFA), kana alexia with lesions posterior to VWFA, and kanji alexia with kanji agraphia with lesions lateral to VWFA. The left angular gyrus has traditionally been considered important for writing. However, it is unclear whether the crucial site is the angular gyrus or the cortical and subcortical regions adjacent to it. In neurodegenerative diseases, reading/writing abilities are differentially impaired depending on the specific distribution of neuronal degeneration in each disease. Examining the reading/writing abilities of kanji and kana can facilitate understanding of the writing system and related disorders.

Left Amygdala Regulates the Cerebral Reading Network During Fast Emotion Word Processing

Emotion words constitute a special class of verbal stimuli which can quickly activate the limbic system outside the left-hemisphere language network. Such fast response to emotion words may arise independently of the left occipitotemporal area involved in visual word-form analysis and rely on a distinct amygdala-dependent emotion circuit involved in fearful face processing. Using a hemifield priming paradigm with fMRI, we explored how the left and right amygdala systems interact with the reading network during emotion word processing. On each trial, participants viewed a centrally presented target which was preceded by a masked prime flashed either to the left or right visual field. Primes and targets, each denoting negative or positive nouns, could be either affectively congruent or incongruent with each other. We observed that affective congruency produced parallel changes in neural priming between the left frontal and parietotemporal regions and the bilateral amygdala. However, we also found that the left, but not right, amygdala exhibited significant change in functional connectivity with the neural components of reading as a function of affective congruency. Collectively, these results suggest that emotion words activate the bilateral amygdala during early stages of emotion word processing, whereas only the left amygdala exerts a long-distance regulatory influence over the reading network via its strong within-hemisphere connectivity.

Early differential sensitivity of evoked-potentials to local and global shape during the perception of three-dimensional objects

Here we investigated the time course underlying differential processing of local and global shape information during the perception of complex three-dimensional (3D) objects. Observers made shape matching judgments about pairs of sequentially presented multi­part novel objects. Event-related potentials (ERPs) were used to measure perceptual sensitivity to 3D shape differences in terms of local part structure and global shape configuration – based on predictions derived from hierarchical structural description models of object recognition. There were three types of different object trials in which stimulus pairs (1) shared local parts but differed in global shape configuration; (2) contained different local parts but shared global configuration or (3) shared neither local parts nor global configuration. Analyses of the ERP data showed differential amplitude modulation as a function of shape similarity as early as the N1 component between 146–215ms post-stimulus onset. These negative amplitude deflections were more similar between objects sharing global shape configuration than local part structure. Differentiation among all stimulus types was reflected in N2 amplitude modulations between 276–330ms. sLORETA inverse solutions showed stronger involvement of left occipitotemporal areas during the N1 for object discrimination weighted towards local part structure. The results suggest that the perception of 3D object shape involves parallel processing of information at local and global scales. This processing is characterised by relatively slow derivation of ‘fine-grained’ local shape structure, and fast derivation of ‘coarse-grained’ global shape configuration. We propose that the rapid early derivation of global shape attributes underlies the observed patterns of N1 amplitude modulations.

Meningioma with purely intratumoral hemorrhage mimicked intracerebral hemorrhage: Case report and literature review

Meningiomas are the most common non-glial intracranial tumor with an incidence of 2.3-5.5/100,000 people, accounting for 20-30% of all primary adult brain tumor diagnoses. Meningiomas associated with hemorrhage are rare; the reported incidence is 0.5-2.4%. We share a case experience of meningioma with purely intratumoral hemorrhage. The initial image study of the intratumoral hemorrhage mimicked intracerebral hemorrhage. A 63-year-old woman with initial presentation of headache, dizziness, nausea, and vomiting has brought to the emergent department. The brain computed tomography showed a 5.3 cm hyperdense lesion over the left occipitotemporal area. Under the impression of intracerebral hemorrhage with unknown etiology, the brain magnetic resonance imaging was done for tumor survey and showed lobulated enhanced mass over left T-O area. Tumor with bleeding with skull bone invasion was first considered. The surgical pathology revealed atypical meningioma with focal clear cell change (World Health Organization Grade II), which is separated with the brain by pia meter. Meningiomas associated with hemorrhage are rare; the reported incidence is 0.5-2.4%. The clinical features about increasing bleeding tendency: (i) age >70 years old or <30 years old; (ii) the location of meningiomas locate at intraventricle or convexity; (iii) histopathalogical type: Meningotheliomatous, malignant, fibrous, and angioblastic type. Most reported intracranial hemorrhages associated with meningiomas are found in the subarachnoid and subdural spaces. There are several hypotheses for the possible mechanism of tumoral bleeding. The tumoral bleeding in meningioma is a rare event. The incidence depended on the location and the histopathological finding. There might be other indicators but still need more research.

The relationship between inflammatory markers and voxel-based gray matter volumes in nondemented older adults

Ageing is characterized by chronically elevated inflammatory markers (IMs). Peripheral IM levels have been found in negative correlations with brain structural measures including global and lobar volumes and the hippocampus. This study investigated the relationship between 10 peripheral IMs and voxel-based gray matter (GM) volumes in nondemented older adults (n = 463). Two proinflammatory cytokines (tumor necrosis factor-α [TNF-α] and interleukin-1β) and 2 vascular IMs (vascular cellular adhesion molecule–1 and plasminogen activator inhibitor–1) were negatively correlated with regional GM volumes. TNF-α and interleukin-1β were both significantly correlated with GM volumes in the left occipitotemporal area, left superior occipital gyrus, and left inferior parietal lobule; TNF-α was also significantly correlated with the bilateral medial prefrontal cortices and approached significance for the correlations with the bilateral hippocampi. Significant GM correlations with vascular cellular adhesion molecule–1 were located in the bilateral anterior cingulate cortices, and with plasminogen activator inhibitor–1 in the cerebellum and right hippocampus. The neuroanatomical correlation patterns of 2 proinflammatory cytokines and 2 vascular IMs might be reflective of the effects of neurodegenerative and vascular pathological processes in the ageing brain.

Cortical organization of language pathways in children with non-localized cryptogenic epilepsy.

Children with a history of epilepsy are almost six times more likely than their unaffected siblings to be referred for speech or language therapy. However, the abnormalities in neural pathway that cause these delays are poorly understood. We recorded evoked fields using whole-head magnetoencephalography during real and non-word visual and auditory rhyme tasks in 15 children with non-localized cryptogenic epilepsy. Basic phonological and orthographic language skills were assessed using Woodcock–Johnson Test of Achievement subtests. Dynamic statistical parameter mapping was used with individual participant magnetic resonance images. Significant cortical activity was visualized on average and performance weighted maps. For the auditory rhyme tasks, bilateral primary and secondary auditory cortices, the superior temporal sulcus, and insular cortex were activated early with later increases in left hemisphere activity. Visual rhyme tasks evoked early bilateral primary and secondary occipital cortical and angular gyri activity followed by later activation of the planum temporale and supramarginal gyri and the left ventral occipitotemporal area. For the auditory rhyme tasks, performance weighted maps demonstrated that early right hemisphere activation was associated with poorer reading skills while later activity was associated with better reading skills; for the left hemisphere, greater early activation of the secondary auditory cortex, including the planum temporale, was related to better reading skills while relatively later activation of these areas was associated with poorer reading skills. For the visual rhyme tasks, greater activity in the bilateral ventral occipitotemporal and insular areas and angular and supramarginal gyri were associated with better performance. These data suggest that spatiotemporal cortical activation patterns are associated with variations in language performance in non-localized cryptogenic epilepsy.

Is the impaired N170 print tuning specific to developmental dyslexia? A matched reading-level study with poor readers and dyslexics

Left N170 print tuning has been associated with visual expertise for print and has been reported to be impaired in dyslexics, using age matched designs. This is the first time N170 print tuning has been compared in adult dyslexics and adult poor readers, matched in reading level. Participants performed a lexical decision task using both word-like stimuli and symbol strings. In contrast to dyslexics, poor readers displayed similar N170 tuning to control expert readers, suggesting that impaired N170 specialization is a hallmark of developmental dyslexia. Our findings provide electrophysiological support for dyslexia being the result of abnormal specialization of the left occipito-temporal areas involved in the expert processing of print. Furthermore, as shown by correlations data and in accordance with the phonological mapping deficit theory, the impaired visual expertise for print described in dyslexics may have been caused by their core phonological deficits.

Functional plasticity in Alzheimer's disease: Effect of cognitive training on language-related ERP components

Starting from the observation of a reduced gray matter in the inferior temporal regions of Alzheimer's disease (AD) patients, the present study hypothesized an altered language-related functional activity in left occipito-temporal areas in AD, and the possibility of a plastic change of these regions induced by an intensive cognitive training. To this aim, eleven mild/moderate AD underwent to a 5-week cognitive training (40h). Before and after the training, evoked potentials were recorded from 26 scalp electrodes during a lexical decision task which required word/no-word discrimination. Stimuli included high- and low-frequency words and non-words, and the recognition potential (RP) together with the N400 have been analyzed and compared with those collected from a matched healthy control group. Results comparing controls and patients before training showed a normal RP in AD patients with a clear peak over left occipito-temporal sites. In addition, controls exhibited a left anterior lateralization of N400 component to words and an inverted pattern for non-words, whereas an altered N400 with bilateral distribution at both word and non-word conditions was found in AD patients. After the cognitive training, AD patients did not show changes in the N400, but revealed a significant enhanced amplitude of RP to high-frequency words. Behavioral responses to the lexical decision task and scores from neuropsychological tests did not evidence improvements nor worsening after training. These data point to an intact functionality of left posterior linguistic networks in mild/moderate AD, and the possibility to increase plastically their activity after a cognitive training.

The neural manifestation of the word concreteness effect: An electrical neuroimaging study

Previous studies have provided controversial evidence about the way in which words with different degrees of concreteness are represented in the brain. The aim of the present study was to investigate whether the processing of abstract vs. concrete words differently affected the timing and topographical distribution of ERP components. Participants were engaged in a lexical decision task (word/non-word discrimination) while EEG was recorded from 128 scalp sites. Reaction times (RTs) to words were faster than RTs to pseudowords. Words were discriminated from pseudowords since larger N2 responses to words than to pseudowords were observed over the left occipito-temporal areas at 300ms post-stimulus. Concrete words and abstract words were discriminated as early as 350ms post-stimulus, with larger responses to concrete than to abstract words over the mesial occipital regions. Concreteness-related ERP differences were also observed in the amplitudes of the later anterior LP component (between 370 and 570ms), with larger responses to abstract words than to concrete words. The LORETA source localization technique was also applied to identify the intra-cranial generators of surface potentials reflecting lexico-semantic processing. Results showed that words (both abstract and concrete) were associated with a stronger activation of the left fusiform gyrus and the left temporal cortex, as compared to pseudowords. Concrete word processing was associated with a stronger activation of the left extrastriate visual areas (namely BA 18 and BA 19) as compared to abstract word processing. By revealing the neural markers of the concreteness effect, our study contributes to the understanding of the neurogenesis of verbal semantic knowledge impairments and the incidence of these impairments in clinical populations.

The neural correlates of impaired collision avoidance in hemianopic patients

The aim of this study was to assess the brain regions associated with impaired performance in a virtual, dynamic collision avoidance task, in a group of patients with homonymous visual field defects (HVFDs) because of unilateral vascular brain lesions. Overall task performance was quantitatively assessed as the number of collisions while crossing an intersection at two levels of traffic density. Twenty-six patients were divided into two subgroups using the median split method: patients with 'performance above average' (HVFD(A), i.e. lower number of collisions) and patients with 'performance below average' (HVFD(B), i.e. higher number of collisions). In order to identify the anatomical structures that might be specifically affected in HVFD(B) patients but spared in HVFD(A) patients, overlap, subtraction and voxel-based lesion-symptom mapping analyses were performed using the MRIcron software. No significant difference in collision avoidance between patients with left- and right-hemispheric lesions was revealed. Separate lesion analysis in 12 patients with right- and 14 patients with left-hemispheric lesions showed that the cortical structures associated with impaired collision avoidance were the parieto-occipital region and posterior cingulate gyrus in the right hemisphere and the inferior occipital cortex and parts of the fusiform (occipito-temporal) gyrus in the left hemisphere. In the present collision avoidance paradigm, impaired performance of patients with right-hemispheric lesions is associated with damage in the dorsal processing stream and potential impact on the visual spatial working memory (WM), while impaired performance of patients with left-hemispheric lesions is associated with damage in the ventral stream and potential impact on the visual object WM.

How number processing survives left occipito-temporal damage

We investigated the neural systems that support number processing in a patient (JL) who had damage to the left ventral occipito-temporal cortex (LvOT). JL had severely impaired written word recognition but he was remarkably accurate in number tasks, albeit slower than normal. This suggests LvOT activation is necessary for efficient but not for accurate number decisions. Here we investigated how JL made accurate number decisions using fMRI; we compared JL's brain activation to that in healthy controls and in two patients with frontal lobe damage who, like JL, made slow but accurate responses in number tasks. For semantic relative to perceptual decisions on numbers, JL did not activate the left occipito-temporal area that was involved in all other subjects. However, JL had significantly increased activation in a left posterior middle temporal region. In addition, during semantic and perceptual decisions on numbers, JL showed increased activation in: (1) the right occipito-temporal cortex, (2) right caudate, and (3) bilateral frontal regions. These effects were unique to JL and cannot be explained in terms of abnormally long response times because they were not observed in the other patients who made slow but accurate number decisions. Together these results show that although the LvOT usually contributes to efficient number processing, activation in this region is not essential for accurate performance because (i) perceptual processing of numbers can be supported by right occipital, right caudate, and bilateral frontal activation and (ii) semantic processing of numbers can be supported by increased left posterior middle temporal activation associated with hand actions.

On the neural basis of emotional word processing. A combined EEG-MEG study with individual head models

Event Abstract Back to Event On the neural basis of emotional word processing. A combined EEG-MEG study with individual head models Marisa Nordt1*, Kati Keuper1, Peter Zwanzger2 and Christian Dobel1 1 Institute for Biomagnetism and Biosignalanalysis, Germany 2 Department of Psychiatry, University of Münster, Germany Emotional stimuli effectively capture attention and therefore obtain prioritized processing. Kissler et al. (2007) demonstrated in an EEG study that this also holds for emotional words. They reported enhanced amplitudes of the ‘early posterior negativity’ (EPN; 200-300 ms) for emotional compared to neutral nouns in left occipito-temporal brain areas. The present study aimed at further investigating the neural mechanisms of early emotional word processing by means of simultaneous EEG-MEG measurements. Participants silently read continuously presented streams of neutral, positive and negative nouns. Data were analyzed using L2 minimum norm solutions based on individual head models and cortical constraints. For the time window of 200-300msec we found enhanced activation for emotional compared to neutral words in left occipito-temporal regions and the Brodmann areas 30 and 40. Findings in left occipito-temporal regions are in line with the results of Kissler et al. (2007). The enhanced activation in Brodmann area 30 comprising the cingulate cortex is consistent with fMRI studies on emotional word processing (Maddock et al., 2003), but has not been found in electrophysiological studies before. Additionally, we found differences between positive and negative words, with more right dorsolateral prefrontal activity for negative words and more left inferior prefrontal activity for positive words. This supports early hemispheric specialization for symbolic emotional stimuli (e.g. Davidson, 2001). Methodologically, this study emphasizes the benefit of combined neurophysiological measures. Funding: Supported by IZKF (Do3/021/10). Keywords: EEG, Language Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Emotion, Motivation and the Social Brain Citation: Nordt M, Keuper K, Zwanzger P and Dobel C (2011). On the neural basis of emotional word processing. A combined EEG-MEG study with individual head models. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00502 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Ms. Marisa Nordt, Institute for Biomagnetism and Biosignalanalysis, Münster, Germany, marisa.nordt@uni-muenster.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Marisa Nordt Kati Keuper Peter Zwanzger Christian Dobel Google Marisa Nordt Kati Keuper Peter Zwanzger Christian Dobel Google Scholar Marisa Nordt Kati Keuper Peter Zwanzger Christian Dobel PubMed Marisa Nordt Kati Keuper Peter Zwanzger Christian Dobel Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Comparing the timecourse of information processing in visual and haptic object recognition

Event Abstract Back to Event Comparing the timecourse of information processing in visual and haptic object recognition Matt Craddock1*, Rebecca Lawson2 and Jasna Martinovic3 1 Universität Leipzig, Germany 2 University of Liverpool, United Kingdom 3 University of Aberdeen, United Kingdom Vision recognises objects much more rapidly and efficiently than haptics: Whereas vision typically processes object information in parallel, haptics requires more sequential exploration, accumulating information over a relatively prolonged period of time. Yet visual and haptic object recognition display many similarities, and involve substantially overlapping neural areas. Examining the timecourse of activity in these areas is difficult due to the mismatch in exploration time and recognition speed across the two modalities. To overcome this issue, we slowed visual processing to a comparable speed to haptic processing using a novel, restricted viewing technique. In an electroencephalographic (EEG) experiment, participants visually and haptically discriminated familiar, nameable objects from unfamiliar, unnameable objects. Analyses focused on onset-related evoked and induced power in the theta- (5-7 Hz; a marker of working memory) and upper-alpha- (10-12 Hz; a marker of sensory processing) bands. Long latency modulations of theta and alpha band activity differentiated between familiar and unfamiliar objects in haptics, but only upper-alpha-band activity differentiated between the two for vision. Source localization using sLORETA found patterns of theta and alpha band activation in haptics that relied on posterior cortices, with left occipitotemporal areas involved for familiar objects and right lateral occipital areas for unfamiliar objects. Our results are consistent with an account of visual and haptic object recognition in which the two modalities share processing resources in common areas, but also indicate that they access those resources differently over time in a manner reflecting fundamental differences between them. Funding: Supported by British Academy Small Research Grant. Keywords: brain oscillations, visual recognition Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Quantitative Analysis of EEG, MEG & Brain Oscillations Citation: Craddock M, Lawson R and Martinovic J (2011). Comparing the timecourse of information processing in visual and haptic object recognition. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00144 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Matt Craddock, Universität Leipzig, Leipzig, Germany, m.p.craddock@leeds.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Matt Craddock Rebecca Lawson Jasna Martinovic Google Matt Craddock Rebecca Lawson Jasna Martinovic Google Scholar Matt Craddock Rebecca Lawson Jasna Martinovic PubMed Matt Craddock Rebecca Lawson Jasna Martinovic Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

New insights into name category-related effects: is the Age of Acquisition a possible factor?

BackgroundElectrophysiological, hemodynamic and neuropsychological studies have provided evidence of dissociation in the way words belonging to different semantic categories (e.g., animals, tools, actions) are represented in the brain. The aim of the present study was to investigate whether a word's semantic domain may affect the amplitude and latency of ERP components, independently of any other factor.MethodsEEGs were recorded from 16 volunteers engaged in a lexical decision task (word/non-word discrimination) involving 100 words (flora and fauna names). This task allowed us to evaluate differences in processing between words belonging to different categories (fauna vs. flora) independently of task demands. All stimuli were balanced in terms of length, frequency of occurrence, familiarity and imageability. Low Resolution Electromagnetic Tomography (LORETA) was performed on ERP difference waves of interest.ResultsOur findings showed that the two categories were discriminated as early as 200 ms post-stimulus, with larger responses to flora names over the left occipito-temporal areas, namely BA37 and BA20. Category-related ERP differences were also observed in the amplitudes of the later centro-parietal N400, posterior P300 and anterior LP components. Behavioral responses to words denoting fauna were more accurate than to words denoting flora.ConclusionOverall, it seems that it was easier to access the lexical properties of fauna, probably because of their biologically relevant status. The results are discussed in the light of the possible role played by different factors.

Early Left-Hemispheric Dysfunction of Face Processing in Congenital Prosopagnosia: An MEG Study

BackgroundCongenital prosopagnosia is a severe face perception impairment which is not acquired by a brain lesion and is presumably present from birth. It manifests mostly by an inability to recognise familiar persons.Electrophysiological research has demonstrated the relevance to face processing of a negative deflection peaking around 170 ms, labelled accordingly as N170 in the electroencephalogram (EEG) and M170 in magnetoencephalography (MEG). The M170 was shown to be sensitive to the inversion of faces and to familiarity-two factors that are assumed to be crucial for congenital prosopagnosia. In order to locate the cognitive dysfunction and its neural correlates, we investigated the time course of neural activity in response to these manipulations.MethodologySeven individuals with congenital prosopagnosia and seven matched controls participated in the experiment. To explore brain activity with high accuracy in time, we recorded evoked magnetic fields (275 channel whole head MEG) while participants were looking at faces differing in familiarity (famous vs. unknown) and orientation (upright vs. inverted). The underlying neural sources were estimated by means of the least square minimum-norm-estimation (L2-MNE) approach.Principal FindingsThe behavioural data corroborate earlier findings on impaired configural processing in congenital prosopagnosia. For the M170, the overall results replicated earlier findings, with larger occipito-temporal brain responses to inverted than upright faces, and more right- than left-hemispheric activity. Compared to controls, participants with congenital prosopagnosia displayed a general decrease in brain activity, primarily over left occipitotemporal areas. This attenuation did not interact with familiarity or orientation.ConclusionsThe study substantiates the finding of an early involvement of the left hemisphere in symptoms of prosopagnosia. This might be related to an efficient and overused featural processing strategy which serves as a compensation of impaired configural processing.

A comparison of letter and digit processing in letter-by-letter reading

The extent to which letter-by-letter reading results from a specific orthographic deficit, as compared with a nonspecific disturbance in basic visuoperceptual mechanisms, is unclear. The current study directly compared processing of letters and digits in a letter-by-letter reader, G.M., using a rapid serial visual presentation (RSVP) task and a speeded matching task. Comparisons were made to a group of six brain-damaged individuals without reading deficits. In the RSVP task, G.M. had increased difficulty reporting the target identities when they were letters, as compared with digits. Although this general pattern was also evident in the control group, the magnitude of the letter-digit accuracy difference was greater in G.M. Similarly, in the matching task, G.M. was slower to match letters than digits, relative to the control group, although his response times to both item types were increased. These data suggest that letter-by-letter reading, at least in this case, results from a visuoperceptual encoding deficit that particularly affects letters, but also extends to processing of digits to a lesser extent. Results are consistent with the notion that a left occipitotemporal area is specialized for letter processing with greater bilaterality in the visual processing of digits.

Buzzwords

Electroencephalographic event-related brain potentials were recorded as subjects read, without further instruction, consecutively presented sequences of words. We varied the speed at which the sequences were presented (3 Hz and 1 Hz) and the words' emotional significance. Early event-related cortical responses during reading differentiated pleasant and unpleasant words from neutral words. Emotional words were associated with enhanced brain responses arising in predominantly left occipito-temporal areas 200 to 300 ms after presentation. Emotional words were also spontaneously better remembered than neutral words. The early cortical amplification was stable across 10 repetitions, providing evidence for robust enhancement of early visual processing of stimuli with learned emotional significance and underscoring the salience of emotional connotations during reading. During early processing stages, emotion-related enhancement of cortical activity along the dominant processing pathway is due to arousal, rather than valence of the stimuli. This enhancement may be driven by cortico-amygdaloid connections.

Oscillatory activity in the occipitotemporal area related to the visual perception of letters of a first/second language and pseudoletters

The objective of this study was to reveal the oscillatory activity in the occipitotemporal area related to the visual perception of the letters of first (L1) and second languages (L2) and pseudoletters. We recorded neuromagnetic signals while Korean native speakers were exposed to a phonogram of Korean, acquired at school age as their L1 ( Hangul), that of Japanese, learned in adulthood as a L2 ( Kana) and pseudoletter ( Pseudo), and quantified the event-related desynchronization (ERD) and synchronization (ERS). In all conditions, sustained ERDs in the alpha band were observed in both hemispheres. ERD for Pseudo was gradually attenuated after ∼400–500 ms after stimulus onset, whereas both Hangul and Kana produced stronger and longer-lasting ERD. ERD for Kana showed a broader alpha band than Hangul. Furthermore, transient ERSs in the gamma band around 70 Hz were observed between 100 and 400 ms in the bilateral occipitotemporal areas. In the left hemisphere, gamma band oscillations showed similar enhancement in all conditions, suggesting that gamma band activity in the left occipitotemporal area might be enhanced not only by the bottom-up process as visual perception but also by the top-down process as attention to prelexical visual stimuli. In the right hemisphere, gamma band ERS was stronger for Hangul than Pseudo and no differences were shown between Kana and Pseudo. The differences of oscillatory activity in the alpha and gamma bands suggest that neuronal networks, including the occipitotemporal area, are related to the visual perception of letters differing between L1 and L2.