Neuronal Correlates of Tactile Working Memory in Prefrontal and Vibrissal Somatosensory Cortex

Abstract

Summary: Tactile working memory engages a broad network of cortical regions in primates. To assess whether the conclusions drawn from primates apply to rodents, we examined the vibrissal primary somatosensory cortex (vS1) and the prelimbic cortex (PL) in a delayed comparison task. Rats compared the speeds of two vibrissal vibrations, stimulus1 and stimulus2, separated by a delay of 2 s. Neuronal firing rates in vS1 and PL encode both stimuli in real time. Across the delay, the stimulus1 representation declines more precipitously in vS1 than in PL. Theta-band local field potential (LFP) coherence between vS1 and PL peaks at trial onset and remains elevated during the interstimulus interval; simultaneously, vS1 spikes become phase locked to PL LFP. Phase locking is stronger on correct (versus error) trials. Tactile working memory in rats appears to be mediated by a posterior (vS1) to anterior (PL) flow of information, with performance facilitated through coherent LFP oscillation. : Esmaeili and Diamond show that tactile working memory in rats engages neuronal firing in the primary somatosensory cortex (vS1) and prelimbic cortex (PL), both in real-time stimulus coding and in the short-term memory trace. Theta-band local field potential oscillations become coherent between vS1 and PL at trial onset. Keywords: tactile, vibrissae, whiskers, rats, working memory, neuronal coding, barrel cortex, somatosensory cortex, prelimbic cortex, medial prefrontal cortex