Perceptual Codes 2 3

31 Working memory representations serve as templates that guide behavior, but the neural 32 basis of these templates remains elusive. We tested the hypothesis that working memory 33 templates are maintained by biasing activity in sensoriperceptual neurons that code for 34 features of items being held in memory. Neural activity was recorded using event-related 35 potentials (ERPs) as participants viewed a series of faces and responded when a face 36 matched a Target face held in working memory. Our prediction was that if activity in 37 neurons coding for the features of the Target is preferentially weighted during 38 maintenance of the Target, then ERP activity evoked by a non-Target Probe face should 39 be commensurate with the visual similarity between Target and Probe. Visual similarity 40 was operationalized as the degree of overlap in visual features between Target and Probe. 41 A face-sensitive ERP response was modulated by Target-Probe similarity. Amplitude 42 was largest for Probes that were similar to the Target, and decreased monotonically as a 43 function of decreasing Target-Probe similarity. These results indicate that neural activity 44 is weighted in favor of visual features that comprise an actively held memory 45 representation. As such, our findings support the notion that working memory templates 46 rely on neural populations involved in forming percepts of memory items. 47 48