Poster A120, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Evaluation of the N1 as an Electrophysiological Marker of Surround Suppression in Healthy Adults
Lisa Levinson1, Lauren C. Shuffrey1,2,3,4, Heather L Green1, Dayna Moya Sepulveda1, Grace Pak1, Alexis Becerra1, Karen Froud1; 1Teachers College, Columbia University, 2Columbia University Medical Center, 3New York State Psychiatric Institute, 4Center for Autism and the Developing Brain
Surround suppression is thought to reflect inhibitory neuronal mechanisms in the visual cortex. Behavioral direction discrimination performance in healthy adults is poor when presenting large, high-contrast moving visual stimuli, thought to reflect surround suppression of motion-selective neurons outside a neuron’s classical receptive field. This suppression of activity is suspected to be driven by the brain’s primary inhibitory neurotransmitter, γ-Aminobutyric acid (GABA) (Tadin et al., 2003; Aaen-Stockdale et al., 2009). To our knowledge, no prior studies have investigated an event-related potential (ERP) marker of surround suppression. We investigated surround suppression in 10 healthy adults 21–33 years of age, using a visual motion-processing task during electroencephalography (EEG) recording to derive the N1 ERP. Stimuli were generated using Psykinematix. They consisted of four, 1 cycle/degree vertical sine wave gratings featuring a center presentation Gaussian envelope drifting either right or left at a speed of 2°/sec. Stimulus size was either 5.0° (large) or 0.7° (small), and stimulus contrast was either 92% (bright) or 2.8% (faint). Participants manifested delayed processing, thought to reflect surround suppression, of large, high-contrast stimuli, indexed by N1 ERP latency (p=.013). Because surround suppression is contrast dependent, processing differences between stimuli sizes having low contrast were neither expected nor observed. The experimental paradigm required no participant response, making it readily implementable for various clinical populations in which surround suppression is potentially compromised due to an imbalance between excitatory and inhibitory neurotransmission.
Topic Area: PERCEPTION & ACTION: Vision