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1.
Front Neurol ; 12: 723677, 2021.
Article in English | MEDLINE | ID: mdl-34867714

ABSTRACT

Visual snow syndrome, characterized by persistent flickering dots throughout the visual field, has been hypothesized to arise from abnormal neuronal responsiveness in visual processing regions. Previous research has reported a lack of typical VEP habituation to repeated stimulus presentation in patients with visual snow. Yet these studies generally used pattern-reversal paradigms, which are suboptimal for measuring cortical responses to the onset of foveal stimulation. Instead, these responses are better indexed by the C2, a pattern-onset VEP peaking 100-120 ms after stimulus onset. In this case study, we analyzed the C2 and its adaptation profile in data previously collected from a single patient with visual snow using a "double-pulse" presentation paradigm. In controls, shorter intervals between stimulus pairs were associated with greater attenuation of the C2 VEP, with recovery from adaptation at longer stimulus onset asynchronies (SOAs). However, the visual snow patient showed the opposite pattern, with reduced C2 amplitude at longer SOAs despite distinct C2 peaks at the shortest SOAs. These results stand in contrast not only to the pattern of C2 VEP attenuation in controls, but also to a lack of adaptation previously reported for the pattern-onset P1 VEP in this patient. Exploratory source localization using equivalent current dipole fitting further suggested that P1 and C2 VEPs in the visual snow patient arose from distinct sources in extrastriate visual cortex. While preliminary, these results support differential patterns of VEP attenuation and potentiation within the same individual, potentially pointing toward multiple mechanisms of abnormal neuronal responsiveness in visual snow syndrome.

2.
Soc Cogn Affect Neurosci ; 13(12): 1269-1279, 2018 12 04.
Article in English | MEDLINE | ID: mdl-30351422

ABSTRACT

Both when actions are executed and observed, electroencephalography (EEG) has shown reduced alpha-band (8-12 Hz) oscillations over sensorimotor cortex. This 'µ-alpha' suppression is thought to reflect mental simulation of action, which has been argued to support internal representation of others' emotional states. Despite the proposed role of simulation in emotion perception, little is known about the effect of emotional content on µ-suppression. We recorded high-density EEG while participants viewed point-light displays of emotional vs neutral body movements in 'coherent' biologically plausible and 'scrambled' configurations. Although coherent relative to scrambled stimuli elicited µ-alpha suppression, the comparison of emotional and neutral movement, controlling for basic visual input, revealed suppression effects in both alpha and beta bands. Whereas alpha-band activity reflected reduced power for emotional stimuli in central and occipital sensors, beta power at frontocentral sites was driven by enhancement for neutral relative to emotional actions. A median-split by autism-spectrum quotient score revealed weaker µ-alpha suppression and beta enhancement in participants with autistic tendencies, suggesting that sensorimotor simulation may be differentially engaged depending on social capabilities. Consistent with theories of embodied emotion, these data support a link between simulation and social perception while more firmly connecting emotional processing to the activity of sensorimotor systems.


Subject(s)
Emotions/physiology , Movement/physiology , Adult , Autistic Disorder , Beta Rhythm , Electroencephalography , Female , Humans , Male , Young Adult
3.
Front Psychol ; 8: 1708, 2017.
Article in English | MEDLINE | ID: mdl-29066987

ABSTRACT

Defined as increased sensitivity to losses, loss aversion is often conceptualized as a cognitive bias. However, findings that loss aversion has an attentional or emotional regulation component suggest that it may instead reflect differences in information processing. To distinguish these alternatives, we applied the drift-diffusion model (DDM) to choice and response time (RT) data in a card gambling task with unknown risk distributions. Loss aversion was measured separately for each participant. Dividing the participants into terciles based on loss aversion estimates, we found that the most loss-averse group showed a significantly lower drift rate than the other two groups, indicating overall slower uptake of information. In contrast, neither the starting bias nor the threshold separation (barrier) varied by group, suggesting that decision thresholds are not affected by loss aversion. These results shed new light on the cognitive mechanisms underlying loss aversion, consistent with an account based on information accumulation.

4.
J Vis ; 10(10): 12, 2010 Aug 16.
Article in English | MEDLINE | ID: mdl-20884477

ABSTRACT

Psychological models suggest that perceptual similarity can be divided into geometric effects, such as metric distance in stimulus space, and non-geometric effects, such as stimulus-specific biases. We investigated the neural and temporal separability of these effects in a carry-over, event-related potential (ERP) study of facial similarity. By testing this dual effects model against a temporal framework of visual evoked components, we demonstrate that the behavioral distinction between geometric and non-geometric similarity effects is consistent with dissociable neural responses across the time course of face perception. We find an ERP component between the "face-selective" N170 and N250 responses (the "P200") that is modulated by transitions of face appearance, consistent with neural adaptation to the geometric similarity of face transitions. In contrast, the N170 and N250 reflect non-geometric stimulus bias, with different degrees of neural adaptation dependent upon the direction of transition within the stimulus space. These results suggest that the neural coding of perceptual similarity, in terms of both geometric and non-geometric representations, occurs rapidly and from relatively early in the perceptual processing stream.


Subject(s)
Adaptation, Physiological/physiology , Evoked Potentials, Visual/physiology , Neurons/physiology , Pattern Recognition, Visual/physiology , Reaction Time/physiology , Space Perception/physiology , Adult , Bias , Electroencephalography , Female , Humans , Male , Photic Stimulation , Young Adult
5.
J Vis ; 8(10): 4.1-12, 2008 Aug 01.
Article in English | MEDLINE | ID: mdl-19146346

ABSTRACT

Although face perception is commonly characterized as holistic, as opposed to part-based, we have recently shown that both face parts and wholes are represented in "face-selective" cortical regions, with greater adaptation of holistic representations for familiar faces (A. Harris & G. K. Aguirre, 2008). Here we investigate the time course of these holistic and part-based face processing effects using magnetoencephalography (MEG). We examined "face-selective" components at early (approximately 170-200 ms) and later (approximately 250-450 ms) latencies in occipitotemporal sensors. While both "M170" and "M400" components showed significantly larger responses for familiar versus unfamiliar faces, neither exhibited a main effect of holistic versus part-based processing. These data affirm the existence of part-based "face-selective" representations, and additionally demonstrate that such representations are present from relatively early stages of face processing. However, only the later M400 component showed a modulatory effect of familiarity similar to that previously seen with fMRI, with a larger response to familiar faces in the holistic condition. Likewise, behavioral recognition was significantly correlated with the M400, not the M170, and only in the holistic condition. Together, these data suggest that, while face parts are represented from the earliest stages of face perception, modulatory effects of familiarity occur later in the face processing stream.


Subject(s)
Field Dependence-Independence , Pattern Recognition, Visual/physiology , Recognition, Psychology/physiology , Adolescent , Adult , Cues , Face , Humans , Magnetoencephalography , Photic Stimulation , Time Factors , Vision Disparity , Visual Cortex/physiology
7.
Neuropsychologia ; 43(14): 2125-36, 2005.
Article in English | MEDLINE | ID: mdl-16243056

ABSTRACT

Developmental prosopagnosia is a lifelong impairment in face recognition despite normal low-level visual processing. Here we used magnetoencephalography (MEG) to examine the M170 response, a component occurring approximately 170 ms after stimulus onset, in a group of five developmental prosopagnosics. In normal subjects, the M170 is "face-selective", with a consistently higher amplitude to faces than to a wide variety of other visual stimulus categories; the N170, a component recorded using event-related potentials (ERP) and thought to be analogous to the M170, also shows this "face selectivity". Two previous ERP studies with developmental prosopagnosics have found attenuation or absence of face selectivity in the N170 response of these subjects [Bentin, S., Deouell, L. Y., and Soroker, N. (1999). Selective visual streaming in face recognition: Evidence from developmental prosopagnosia. Neuroreport, 10, 823-827; Kress, T., and Daum, I. (2003). Event-related potentials reflect impaired face recognition in patients with congenital prosopagnosia. Neuroscience Letters, 352, 133-136]. Three of our developmental prosopagnosic group showed this non-selective pattern at the M170 while the remaining two prosopagnosics were indistinguishable from normal controls. Thus, impaired face recognition is not necessarily correlated with an absence of the "face-selective" M170. Furthermore, ERP recordings collected simultaneously in the two developmental prosopagnosics with seemingly selective M170s also showed N170s within the same normal selective range, demonstrating that the face-selective signals found with MEG are not due to differences between MEG and ERP. While the presence of face selectivity at these neurophysiological markers is insufficient for predicting normal behavioral performance with faces, it could help to distinguish different classes of face recognition deficits.


Subject(s)
Evoked Potentials, Visual/physiology , Face , Prosopagnosia/physiopathology , Recognition, Psychology/physiology , Visual Perception/physiology , Adult , Analysis of Variance , Brain Mapping , Discrimination Learning/physiology , Electroencephalography/methods , Female , Functional Laterality/physiology , Humans , Linear Models , Magnetoencephalography/methods , Male , Middle Aged , Psychomotor Performance/physiology
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