Biology subjects

Kveraga, K.

Publications and source records attributed to Kveraga, K..

5 recordsLinked to original sources

bioRxiv2017

Sex-related differences in behavioral and amygdalar responses to compound facial threat cues

During face perception, we integrate facial expression and eye gaze to take advantage of their shared signals. For example, fear with averted gaze provides a congruent avoidance cue, signaling both threat presence and its location, whereas fear with direct gaze sends an incongruent cue, leaving threat location ambiguous. It has been proposed that the processing of different combinations of threat cues is mediated by dual processing routes: reflexive processing via magnocellular (M) pathway and reflective processing via parvocellular (P) pathway. Because growing evidence has identified a variety of sex differences in emotional perception, here we also investigated how M and P processing of fear and eye gaze might be modulated by observers sex, focusing on the amygdala, a structure important to threat perception and affective appraisal. We adjusted luminance and color of face stimuli to selectively engage M or P processing and asked observers to identify emotion of the face. Female observers showed more accurate behavioral responses to faces with averted gaze and greater left amygdala reactivity both to fearful and neutral faces. Conversely, males showed greater right amygdala activation only for M-biased averted-gaze fear faces. In addition to functional reactivity differences, females had greater bilateral amygdala volumes, which positively correlated with behavioral accuracy for M-biased fear. Conversely, in males only the right amygdala volume was positively correlated with accuracy for M-biased fear faces. Our findings suggest that M and P processing of facial threat cues is modulated by functional and structural differences in the amygdalae associated with observers sex.

neuroscience↗

bioRxiv2017

Neurodynamics and connectivity during facial fear perception: The role of threat exposure and signal congruity

Fearful faces convey threat cues whose meaning is contextualized by eye gaze: While averted gaze is congruent with facial fear (both signal avoidance), direct gaze is incongruent with it, as direct gaze signals approach. We have previously shown using fMRI that the amygdala is engaged more strongly by fear with averted gaze, which has been found to be processed more efficiently, during brief exposures. However, the amygdala also responds more to fear with direct gaze during longer exposures. Here we examined previously unexplored brain oscillatory responses to characterize the neurodynamics and connectivity during brief ([~]250 ms) and longer ([~]883 ms) exposures of fearful faces with direct or averted eye gaze. We replicated the exposure time by gaze direction interaction in fMRI (N=23), and observed greater early phase locking to averted-gaze fear (congruent threat signal) with MEG (N=60) in a network of face processing regions, with both brief and longer exposures. Phase locking to direct-gaze fear (incongruent threat signal) then increased significantly for brief exposures at [~]350 ms, and at [~]700 ms for longer exposures. Our results characterize the stages of congruent and incongruent facial threat signal processing and show that stimulus exposure strongly affects the onset and duration of these stages.

neuroscience↗

bioRxiv2017

Anxiety Modulates Perception Of Facial Fear In A Pathway-Specific, Lateralized, Manner

Facial expression and eye gaze provide a shared signal about threats. While averted-gaze fear clearly points to the source of threat, direct-gaze fear renders the source of threat ambiguous. Dual processing routes have been proposed to mediate these processes: reflexive processing via magnocellular (M-) pathway and reflective processing via parvocellular (P-) pathway. We investigated how observers trait anxiety modulates Mand P-pathway processing of clear and ambiguous threat cues. We performed fMRI on a large cohort (N=108) widely ranging in trait anxiety while they viewed fearful or neutral faces with averted or directed gaze. We adjusted luminance and color of the stimuli to selectively engage M- or P-pathway processing. We found that higher anxiety facilitated processing of averted-gaze fear projected to M-pathway, but impaired perception of direct-gaze fear projected to P-pathway. Increased right amygdala reactivity was associated with higher anxiety, only for averted-gaze fear presented to M-pathway. Conversely, increased left amygdala reactivity was associated with higher anxiety for P-biased, direct-gaze fear. This lateralization was more pronounced with higher anxiety. Our findings suggest that trait anxiety has differential effects on perception of clear and ambiguous facial threat cues via selective engagement of M and P pathways and lateralization of amygdala reactivity.

neuroscience↗

bioRxiv2017

Cross-Cultural Effects On Ensemble Coding Of Emotion In Facial Crowds

In many social situations, we make a snap judgment about crowds of people relying on their overall mood (termed \"crowd emotion\"). Although reading crowd emotion is critical for interpersonal dynamics, the sociocultural aspects of this process have not been explored. The current study examined how culture modulates the processing of crowd emotion in Korean and American observers. Korean and American participants were briefly presented with two groups of faces that were individually varying in emotional expressions and asked to choose which group between the two they would rather avoid. We found that Korean participants were more accurate than American participants overall, in line with the framework on cultural viewpoints: Holistic versus analytic processing in East Asians versus Westerners. Moreover, we found a speed advantage for other-race crowds in both cultural groups. Finally, we found different hemispheric lateralization patterns: American participants were more accurate for angry crowds presented in the left visual field and happy crowds presented in the right visual field, replicating previous studies, whereas Korean participants did not show an interaction between emotional valence and visual field. This work suggests that culture plays a role in modulating our crowd emotion perception of groups of faces and responses to them.

neuroscience↗

bioRxiv2017

Differential hemispheric and visual stream involvement in ensemble coding of emotion in facial crowds

The visual system takes advantage of redundancies in the scene by extracting summary statistics from a set of items. Similarly, in many social situations where scrutinizing each individuals expression is inefficient, human observers make snap judgments of crowds of people by reading \"crowd emotion\" to avoid danger (e.g., mass panic or violent mobs) or to seek help. However, how the brain accomplishes this feat remains unaddressed. Here we report a set of behavioral and fMRI studies in which participants made avoidance or approach decisions by choosing between two facial crowds presented in the left and right visual fields (LVF/RVF). Participants were most accurate for crowds containing task-relevant cues: avoiding angry crowds and approaching happy crowds. This effect was amplified by sex-linked facial cues (angry male/happy female crowds) and highly lateralized, with better recognition of the task-congruent facial crowd when presented in LVF. fMRI results showed that the dorsal visual stream was preferentially activated in crowd emotion processing, with intraparietal sulcus and superior frontal gyrus predicting behavioral crowd emotion efficiency, whereas the ventral visual stream showed greater involvement in individual face emotion processing, with fusiform cortex activity predicting the accuracy of decisions about individual face emotion. Our results shed new light on the distinction between global vs. local processing of face stimuli, revealing differential involvement of the left and right hemispheres and the dorsal and ventral pathways in reading crowd vs. individual emotion.

neuroscience↗