9/11/25 Geoff Woodman: Decoding the comparison process during visual search
CCN brown bag
Geoff Woodman, PhD
Professor of Psychology
E. Bronson Ingram Chair of Neuroscience, Director of National Eye Institute T32
Date: Thursday, September 11, 2025
Time: 12:10- 1:00pm
Location: Wilson Hall 316
Decoding the comparison process during visual search
For centuries theorists have proposed that attention shifts between interesting perceptual inputs (e.g., a shiny red car) as they are compared with a memory representation of the target (i.e., is that my red car?). Here we show that the comparison process can be tracked using the precise temporal resolution of human electrophysiology. We placed target cues and search elements at unique spatial locations and trained pattern classifiers to decoded when subjects were attending to items in the search array versus reactivating the searched-for-target representation in memory. We were first able to decode the attentional selection of the candidate target object and reactivation of the memory of the target, both on individual trials and the group average. When we made the task for difficult by making difficult to discriminate nontarget objects, we found that this modulated the dynamics of the comparison process. Further we show that the timing of this comparison process was tightly related to the speed of subjects’ responses, unlike the time when we could first decode attention selected the possible target object. Thus, the present findings demonstrate how we can use electrical brain activity to measure the long-hypothesized comparison between memories and new inputs to our visual systems.
Acknowledgements
Grants were provided by the National Science Foundation (BCS-2147064), and NEI (P30-EY08126), the E. Bronson Ingram Family, and the G. Forrest Woodman Foundation for the Advancement of Neuroscience.