The encoding of race during face processing, an event-related potential study

It is well known that adults spontaneously classify people into social categories and this categorization in turn guides their cognition and behavior. A wealth of research has examined how people perceive race and investigated the effect of race on social behavior. But what about race encoding? Although considerable behavioral research has investigated the encoding of race, that is, the social categorization by race, the neural underpinning of it is largely underexplored. To investigate the time course of race encoding, the current study employed a modified category verification task and a multivariate analyzing approach. We found that racial information became decodable from event-related potential topographies as early as about 200 ms after stimulus onset. At this stage, the brain can differentiate different races in a task-relevant manner. Nonetheless, it is not until 100 ms later that racial information is encoded in a socially relevant manner (own- versus other-race). Importantly, perceptual differentiation not only occurs before the encoding of the race but actually influences it: the faces that are more easily perceptually categorized are actually encoded more readily. Together, we posit that the detection and the encoding of race are decoupled although they are not completely independent. Our results provide powerful constraints toward the theory-building of race.

Dissociable Neural Information Dynamics of Perceptual Integration and Differentiation during Bistable Perception

At any given moment, we experience a perceptual scene as a single whole and yet we may distinguish a variety of objects within it. This phenomenon instantiates two properties of conscious perception: integration and differentiation. Integration is the property of experiencing a collection of objects as a unitary percept and differentiation is the property of experiencing these objects as distinct from each other. Here, we evaluated the neural information dynamics underlying integration and differentiation of perceptual contents during bistable perception. Participants listened to a sequence of tones (auditory bistable stimuli) experienced either as a single stream (perceptual integration) or as two parallel streams (perceptual differentiation) of sounds. We computed neurophysiological indices of information integration and information differentiation with electroencephalographic and intracranial recordings. When perceptual alternations were endogenously driven, the integrated percept was associated with an increase in neural information integration and a decrease in neural differentiation across frontoparietal regions, whereas the opposite pattern was observed for the differentiated percept. However, when perception was exogenously driven by a change in the sound stream (no bistability), neural oscillatory power distinguished between percepts but information measures did not. We demonstrate that perceptual integration and differentiation can be mapped to theoretically motivated neural information signatures, suggesting a direct relationship between phenomenology and neurophysiology.

Dissociable neural information dynamics of perceptual integration and differentiation during bistable perception

ABSTRACTAt any given moment, we experience a perceptual scene as a single whole and yet we may distinguish a variety of objects within it. This phenomenon instantiates two properties of conscious perception: integration and differentiation. Integration to experience a collection of objects as a unitary percept, and differentiation to experience these objects as distinct from each other. Here we evaluated the neural information dynamics underlying integration and differentiation of perceptual contents during bistable perception. Participants listened to a sequence of tones (auditory bistable stimuli) experienced either as a single stream (perceptual integration) or as two parallel streams (perceptual differentiation) of sounds. We computed neurophysiological indices of information integration and information differentiation with electroencephalographic and intracranial recordings. When perceptual alternations were endogenously driven, the integrated percept was associated with an increase in neural information-integration and a decrease in neural differentiation across frontoparietal regions, whereas the opposite pattern was observed for the differentiated percept. However, when perception was exogenously driven by a change in the sound stream (no bistability) neural oscillatory power distinguished between percepts but information measures did not. We demonstrate that perceptual integration and differentiation can be mapped to theoretically-motivated neural information signatures, suggesting a direct relationship between phenomenology and neurophysiology.

Structural Similarity Exerts Opposing Effects on Perceptual Differentiation and Categorization: An fMRI Study

We manipulated the degree of structural similarity between objects that had to be matched either according to whether they represented the same object (perceptual matching) or belonged to the same category (conceptual matching). Behaviorally, performance improved as a linear function of increased structural similarity during conceptual matching but deteriorated as a linear function of increased structural similarity during perceptual matching. These effects were mirrored in fMRI recordings where activation in several ventral posterior areas exhibited a similar interaction between match type and structural similarity. Our findings provide direct support for the notion that structural similarity exerts opposing effects on classification depending on whether objects are to be perceptually differentiated or categorized—a notion that has been based on rather circumstantial evidence. In particular, the finding that structural similarity plays a major role in categorization of instances according to taxonomy challenges the view that the organization of superordinate categories is not driven by shared structural features.

Process and Domain Specificity in Regions Engaged for Face Processing: An fMRI Study of Perceptual Differentiation

The degree to which face-specific brain regions are specialized for different kinds of perceptual processing is debated. This study parametrically varied demands on featural, first-order configural, or second-order configural processing of faces and houses in a perceptual matching task to determine the extent to which the process of perceptual differentiation was selective for faces regardless of processing type (domain-specific account), specialized for specific types of perceptual processing regardless of category (process-specific account), engaged in category-optimized processing (i.e., configural face processing or featural house processing), or reflected generalized perceptual differentiation (i.e., differentiation that crosses category and processing type boundaries). ROIs were identified in a separate localizer run or with a similarity regressor in the face-matching runs. The predominant principle accounting for fMRI signal modulation in most regions was generalized perceptual differentiation. Nearly all regions showed perceptual differentiation for both faces and houses for more than one processing type, even if the region was identified as face-preferential in the localizer run. Consistent with process specificity, some regions showed perceptual differentiation for first-order processing of faces and houses (right fusiform face area and occipito-temporal cortex and right lateral occipital complex), but not for featural or second-order processing. Somewhat consistent with domain specificity, the right inferior frontal gyrus showed perceptual differentiation only for faces in the featural matching task. The present findings demonstrate that the majority of regions involved in perceptual differentiation of faces are also involved in differentiation of other visually homogenous categories.

Acoustic Correlates of Prosodic Abnormality in Acquired Apraxia of Speech

Purpose: Prosodic abnormality is one of the primary characteristics used for the perceptual differentiation between acquired apraxia of speech (AOS) and phonemic paraphasias in the context of fluent aphasia. Acoustic measures of speech prosody are not frequently used in the clinical assessment of AOS, but would be useful as a method of quantifying prosodic abnormality. The purpose of this paper is to describe acoustic characteristics of prosodic abnormality in adult speakers with AOS. Method: Previous investigations of acoustic measures of speech prosody in AOS were reviewed, focusing on studies of duration, fundamental frequency (F0), and speech intensity. Results and Conclusions: Prosodic abnormality in adults with AOS is primarily characterized by articulatory prolongation. In some individuals, relational patterns among syllables are retained despite overall increased duration, while others produce syllables that are temporally isolated, giving the impression that speech is programmed one syllable at a time. Syllable segregation is also noted in F0 and intensity contours that lack continuity across syllables. Metrics are suggested for use in quantification of prosodic abnormality in AOS. The review of findings, particularly slowed speech rate, is interpreted in the context of theoretical models of speech including impaired or intact feedback mechanisms in speakers with AOS.