Biology subjects

Kovacs, G.

Publications and source records attributed to Kovacs, G..

5 recordsLinked to original sources

bioRxiv2018

The neural dynamics of familiar face recognition

In real-life situations, the appearance of a persons face can vary substantially across different encounters, making face recognition a challenging task for the visual system. Recent fMRI decoding studies have suggested that face recognition is supported by identity representations located in regions of the occipito-temporal cortex. Here, we used EEG to elucidate the temporal emergence of these representations. Human participants (both sexes) viewed a set of highly variable face images of four highly familiar celebrities (two male, two female), while performing an orthogonal task. Univariate analyses of event-related EEG responses revealed a pronounced differentiation between male and female faces, but not between identities of the same sex. Using multivariate representational similarity analysis, we observed a gradual emergence of face identity representations, with an increasing degree of invariance. Face identity information emerged rapidly, starting shortly after 100ms from stimulus onset. From 400ms after onset and predominantly in the right hemisphere, identity representations showed two invariance properties: (1) they equally discriminated identities of opposite sexes and of the same sex, and (2) they were tolerant to image-based variations. These invariant representations may be a crucial prerequisite for successful face recognition in everyday situations, where the appearance of a familiar person can vary drastically.\n\nSignificance StatementRecognizing the face of a friend on the street is a task we effortlessly perform in our everyday lives. However, the necessary visual processing underlying familiar face recognition is highly complex. As the appearance of a given person varies drastically between encounters, for example across viewpoints or emotional expressions, the brain needs to extract identity information that is invariant to such changes. Using multivariate analyses of EEG data, we characterize how invariant representations of face identity emerge gradually over time. After 400ms of processing, cortical representations reliably differentiated two similar identities (e.g., two famous male actors), even across a set of highly variable images. These representations may support face recognition under challenging real-life conditions.

neuroscience↗

bioRxiv2017

When Less is More: Enhanced Statistical Learning After Disruption of Bilateral DLPFC

Brain networks related to human learning can interact in cooperative but also competitive ways to optimize performance. The investigation of such interactive processes is rare in research on learning and memory. Previous studies have shown that manipulations reducing the engagement of prefrontal cortical areas could lead to improved statistical learning performance. However, no study has investigated how disruption of the dorsolateral prefrontal cortex (DLPFC) affects the acquisition and consolidation of non-adjacent second-order dependencies. The present study aimed to test the role of the DLPFC, more specifically, the Brodmann 9 area in implicit temporal statistical learning of non-adjacent dependencies. We applied 1 Hz inhibitory transcranial magnetic stimulation or sham stimulation over both the left and right DLPFC intermittently during the learning. The DLPFC-stimulated group showed better performance compared to the sham group after a 24-hour consolidation period. This finding suggests that the disruption of DLPFC during learning induces qualitative changes in the consolidation of non-adjacent statistical regularities. A possible mechanism behind this result is that the stimulation of the DLPFC promotes a shift to model-free learning by weakening the access to model-based processes.

neuroscience↗

bioRxiv2017

Novel causative genes for heritable pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within components of the transforming growth factor-{beta} pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlie most heritable forms of PAH. Since the missing heritability likely involves genetic variation confined to small numbers of cases, we performed whole genome sequencing in 1038 PAH index cases and 6385 PAH-negative control subjects. Case-control analyses revealed significant overrepresentation of rare variants in novel genes, namely ATP13A3, AQP1 and SOX17, and provided independent validation of a critical role for GDF2 in PAH. We provide evidence for familial segregation of mutations in SOX17 and AQP1 with PAH. Mutations in GDF2, encoding a BMPR2 ligand, led to reduced secretion from transfected cells. In addition, we identified pathogenic mutations in the majority of previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings provide new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.

genetics↗

bioRxiv2017

TECPR2 a positive regulator of autophagy is implicated in healthy brain ageing

Understanding the healthy brain aging process is key to uncovering the mechanisms leading to pathological age-related neurodegeneration, including progression to Alzheimers disease (AD). Here, we report the first deep whole genome sequencing study aiming to identify variants that are associated specifically to healthy brain aging defined on both clinical and neuropathological level, thus tacking the issue of pathological heterogeneity that often underlies a clinical AD diagnosis. We studied samples from the VITA brain bank and followed an extreme phenotypic ends study design comparing neuropathologically \"healthy\" aging individuals above 80 years of age with pure AD patients of the same age. Focusing on the extreme ends of the phenotypic distribution, and potentially functional variants, we discover a single variant (rs10149146) carried by 53.6% of the \"healthy\" brain elderly individuals in our study (15/28 individuals) and none of the 12 AD cases. This variant lies on the autophagy and cell cycle associated TECPR2 gene. Autophagy dysfunction has been previously implicated in multiple progressive neurodegenerative diseases. An additional non-synonymous variant on the CINP gene (encoding a cell-cycle checkpoint protein) is also found in 46% of healthy controls and absent from all the AD cases. TECPR2 and CINP appear to be \"partner\" genes in terms of regulation and their associated transcription factors have been previously implicated in AD and neurodegeneration. Our study is the first to support the hypothesis that a TECPR2 non-synonymous variant carries a significant neuroprotective effect pointing to key molecules for the involvement of autophagy and cell cycle control in protection from neurodegeneration.

genomics↗

bioRxiv2017

Face inversion reveals holistic processing of peripheral faces

Face perception is accomplished by face-selective neural processes, involving holistic processing that enables highly efficient integration of facial features into a whole face representation. It has been shown that in face-selective regions of the ventral temporal cortex, neural resources involved in holistic processing are primarily dedicated to the central portion of the visual field. These findings raise the intriguing possibility that holistic processing might be the privilege of centrally presented faces and could be strongly diminished in the case of peripheral faces. We addressed this question using the face inversion effect, a well established marker of holistic face processing. The behavioral results revealed impaired identity discrimination performance for inverted peripheral faces scaled according to the V1 magnification factor, compared to upright presented faces. The size of peripheral face inversion effect (FIE) was comparable to that found for centrally displayed faces. Face inversion affected the early ERP responses to faces in two time intervals. The earliest FIE was most pronounced in the time window between 130-140 ms following stimulus presentation, for both centrally and peripherally displayed faces and in the latter case, it was present only over the contralateral hemisphere. The timing of the next component FIE corresponded closely with the temporal interval of the N170 ERP component and showed strong right hemisphere lateralization, both when faces were displayed in the left or right visual field. Furthermore, we also showed that centrally presented face masks impaired peripheral face identity discrimination performance, but did not reduce the magnitude of the FIE. These findings revealed robust behavioral and neural inversion effects for peripheral faces and thus suggest that faces are processed holistically throughout the visual field.\n\nHighlightsRobust behavioral and neural inversion effect was found for peripheral faces.\n\nP1 ERP component is modulated by inverted central and contralateral faces.\n\nN170 ERP component is modulated by centrally and peripherally presented faces.\n\nNeural face inversion effect shows strong right hemisphere lateralization.\n\nFaces are processed holistically throughout the visual field.

neuroscience↗