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L. Forest Gruss, Margaret Bradley, Andreas Keil; Fear memories in visual cortex: inter-individual differences related to reflex physiology and genetic variants. Journal of Vision 2014;14(10):669. doi: 10.1167/14.10.669.
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© ARVO (1962-2015); The Authors (2016-present)
Classical fear conditioning is a widely used laboratory model of how humans acquire a fear response. In the present study, we used electroencephalography (EEG), heart rate, skin conductance, the startle response, as well as self-report measures to study inter-individual differences in differential fear conditioning. Additionally, we collected saliva samples to relate genetic polymorphisms (8 selected SNPs implicated in brain plasticity) to cortical and physiological indices of fear learning. We adopted a paradigm with visual grating stimuli that have differential capability to engage luminance versus chromatic pathways of the human visual system. Grating orientation served as the discriminant feature in this conditioning paradigm. A loud (96dB) noise served as the unconditioned stimulus (US). Gratings were presented in a flickering fashion (14Hz) to evoke steady state visually evoked potentials (ssVEPs). We predicted that heart rate (HR) accelerators versus decelerators (Hodes et al, 1985) would show an electrocortical increase to the aversively conditioned stimulus (CS+) during the acquisition phase, solely for the stimulus engaging the luminance pathway. Results revealed three distinct groups of HR responders: accelerators, decelerators and moderate decelerators. As expected, preliminary results show that HR accelerators have significant ssVEP amplitude increase to the CS+ during acquisition. The HR decelerators on the other hand showed the reverse pattern, with a marked decrease of the ssVEP signal to the CS+. These data suggest that although both groups learn the association of the CS+ to the US as per their self-report, the HR accelerators may engage their fear system more strongly, reflected in reflex physiology as well as in visual cortex. Further analyses of how the genetic polymorphisms relate to conditioning effects in the visual cortex, may illuminate the underlying inter-individual differences observed in fear learning.
Meeting abstract presented at VSS 2014
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