Cortical feedback loops bind distributed representations of working memory

Abstract

Working memory—the brain’s ability to internalize information and use it flexibly to guide behaviour—is an essential component of cognition. Although activity related to working memory has been observed in several brain regions1–3, how neural populations actually represent working memory4–7 and the mechanisms by which this activity is maintained8–12 remain unclear13–15. Here we describe the neural implementation of visual working memory in mice alternating between a delayed non-match-to-sample task and a simple discrimination task that does not require working memory but has identical stimulus, movement and reward statistics. Transient optogenetic inactivations revealed that distributed areas of the neocortex were required selectively for the maintenance of working memory. Population activity in visual area AM and premotor area M2 during the delay period was dominated by orderly low-dimensional dynamics16,17 that were, however, independent of working memory. Instead, working memory representations were embedded in high-dimensional population activity, present in both cortical areas, persisted throughout the inter-stimulus delay period, and predicted behavioural responses during the working memory task. To test whether the distributed nature of working memory was dependent on reciprocal interactions between cortical regions18–20, we silenced one cortical area (AM or M2) while recording the feedback it received from the other. Transient inactivation of either area led to the selective disruption of inter-areal communication of working memory. Therefore, reciprocally interconnected cortical areas maintain bound high-dimensional representations of working memory.

Independent response modulation of visual cortical neurons by attentional and behavioral states

“…In some sessions, grating stimuli of lower contrast were used to make the task more difficult. All visual stimuli were generated with a custom written UDP-interfaced visual stimulus presentation program (Voitov and Mrsic-Flogel, 2022).…”

The direct and indirect pathways of the basal ganglia antagonistically influence cortical activity and perceptual decisions

“…The present results support that immediate and delayed visuomotor transformations are, in part, mediated by the loop between the cortex and the basal ganglia, although the loops from cortex to cerebellum to the thalamus and then back to the cortex may also play a role (Gao et al, 2019). Persistent neuronal activity related to working memories appear to be an emergent property of distributed networks (Christophel et al, 2017; Voitov and Mrsic-flogel, 2022) where the striatal pathways can orchestrate cortical activity by integrating sensory and motivational inputs to support adaptive behavior.…”

“…The finding that persistent activity occurs in many brain regions suggests that it may be an emergent property of distributed brain networks (Christophel et al, 2017; Dotson et al, 2018; Voitov and Mrsic-flogel, 2022). Interestingly, brain regions that are of importance in tasks that rely on working memory are often also involved in simpler decision-making tasks.…”

Like friends, brain regions depend on each other to make good memories

“…A recent study published in Nature on mice revealed that their visual working memory is maintained by the interconnection between different brain regions [1]. One of the authors of the study said: "By recording from and manipulating long-range circuits in the cerebral cortex, we uncovered that working memory resides within co-dependent activity patterns in cortical areas that are interconnected, thereby maintaining working memory through instantaneous reciprocal communication" [2].…”

“…Like friends, brain regions depend on each other to make good memories https://mindsponge.info/posts/38 1 of 3 7/30/2022, 12:24 AM Inactivation of either involved cortical area leads to disruption in the mice's ability to retain working memory [1]. In other words, to have a working memory, different brain regions were shown to be instantaneously co-dependent on each other.…”