Temporal dynamics of face selection mechanism in the context of similar and dissimilar faces: ERP evidence for biased competition within the ventral occipito-temporal cortex using ICA

P1, N170, and N250 Event-related Potential Components Reflect Temporal Perception Processing in Face and Body Personal Identification

Human faces and bodies represent various socially important signals. Although adults encounter numerous new people in daily life, they can recognize hundreds to thousands of different individuals. However, the neural mechanisms that differentiate one person from another person are unclear. This study aimed to clarify the temporal dynamics of the cognitive processes of face and body personal identification using face-sensitive ERP components (P1, N170, and N250). The present study performed three blocks (face-face, face-body, and body-body) of different ERP adaptation paradigms. Furthermore, in the above three blocks, ERP components were used to compare brain biomarkers under three conditions (same person, different person of the same sex, and different person of the opposite sex). The results showed that the P1 amplitude for the face-face block was significantly greater than that for the body-body block, that the N170 amplitude for a different person of the same sex condition was greater than that for the same person condition in the right hemisphere only, and that the N250 amplitude gradually increased as the degree of face and body sex-social categorization grew closer (i.e., same person condition > different person of the same sex condition > different person of the opposite sex condition). These results suggest that early processing of the face and body processes the face and body separately and that structural encoding and personal identification of the face and body process the face and body collaboratively.

Role of line junctions in expert object recognition: The case of musical notation

Line junctions are well-known to be important for real-world object recognition, and sensitivity to line junctions is enhanced with perceptual experience with an object category. However, it remains unclear whether these very simple visual features are involved in expert object representations at the neural level, and if yes, at what level(s) they are involved. In this EEG study, 31 music reading experts and 31 novices performed a one-back task with intact musical notation, musical notation with line junctions removed and pseudo-letters. We observed more separable neural representations of musical notation from pseudo-letter for experts than for novices when line junctions were present and during 180-280 ms after stimulus onset. Also, the presence of line junctions was better decoded in experts than in novices during 320-580 ms, and the decoding accuracy in this time window predicted the behavioral recognition advantage of musical notation when line junctions were present. These suggest that, with perceptual expertise, line junctions are more involved in category selective representation of objects, and are more explicitly represented in later stages of processing to support expert recognition performance.

Electrophysiological evidence of inhibited orthographic regularity effect on the recognition of real Chinese characters

Orthographic regularity is important for processing Chinese characters. However, the issues how orthographic regularity influences the visual recognition of real Chinese characters and whether common processes related to the potential effect exist between successive (SUCC) and concurrent (CONC) conditions with asynchronous presentation of S1 and S2 are still unclear. In the current study, event-related potential (ERP) technique was adopted to investigate electrophysiological correlates of the orthographic regularity effect. Behaviorally, we found fewer errors and shorter response times for SUCC and CONC conditions compared to simultaneous (SIM) condition with synchronous presentation and disappearance of S1 and S2, which demonstrates similarities between SUCC and CONC and their differences from SIM. We found bilaterally smaller N170 responses for real Chinese characters preceded by false characters compared to real characters, demonstrating that orthographic regularity may inhibit the recognition of real Chinese characters. Additionally, the inhibition effect was present in SUCC and CONC rather than SIM, which shows that smaller N170 responses may have been due to asynchronous presentations of S1 and S2 and common inhibition processes in the SUCC and CONC conditions.

In search of biomarkers in psychiatry: EEG-based measures of brain function

Current clinical parameters used for diagnosis and phenotypic definitions of psychopathology are both highly variable and subjective. Intensive research efforts for specific and sensitive biological markers, or biomarkers, for psychopathology as objective alternatives to the current paradigm are ongoing. While biomarker research in psychiatry has focused largely on functional neuroimaging methods for identifying the neural functions that associate with psychopathology, scalp electroencephalography (EEG) has been viewed, historically, as offering little specific brain source information, as scalp appearance is only loosely correlated to its brain source dynamics. However, ongoing advances in signal processing of EEG data can now deliver functional EEG brain-imaging with distinctly improved spatial, as well as fine temporal, resolution. One computational approach proving particularly useful for EEG cortical brain imaging is independent component analysis (ICA). ICA decomposition can be used to identify distinct cortical source activities that are sensitive and specific to the pathophysiology of psychiatric disorders. Given its practical research advantages, relatively low cost, and ease of use, EEG-imaging is now both feasible and attractive, in particular for studies involving the large samples required by genetically informative designs to characterize causal pathways to psychopathology. The completely non-invasive nature of EEG data acquisition, coupled with ongoing advances in dry, wireless, and wearable EEG technology, makes EEG-imaging increasingly attractive and appropriate for psychiatric research, including the study of developmentally young samples. Applied to large genetically and developmentally informative samples, EEG imaging can advance the search for robust diagnostic biomarkers and phenotypes in psychiatry.

The quest for single trial correlations in multimodal EEG-fMRI data

In the past decade, technological advances have made it possible to reliably measure brain activity using simultaneous EEG-fMRI recordings inside an MR scanner. The main challenge then became to investigate the coupling between the EEG and fMRI signals in order to benefit from the simultaneously integrated temporal and spatial resolution. Although it is crucial to know when features in EEG and fMRI are expected to correlate with each other before the identification of common sources from multimodal data is possible, it is still a matter of debate. In this study, we address this question by analysing EEG and fMRI data separately from a face processing task. We show that we are able to reliably estimate single trial (ST) dynamics of face processing in EEG and fMRI data separately in four subjects. However, no correlation is found between the modalities. This implies that in this task modality-specific information is larger than the information that is shared by the modalities.