Prospective representations in rat orbitofrontal ensembles.

Abstract

The orbitofrontal cortex (OFC) has been proposed to encode expected outcomes, which is thought to be important for outcome-directed behavior. However, such neural encoding can also often be explained by the recall of information about the recent past. To dissociate the retrospective and prospective aspects of encoding in the OFC, we designed a nonspatial, continuous, alternating odor-sequence task that mimicked a continuous T-maze. The task consisted of two alternating sequences of four odor-guided trials (2 sequences × 4 positions). In each trial, rats were asked to make a "go" or "no-go" action based on a fixed odor-reward contingency. Odors at both the first and last positions were distinct across the two sequences, such that they resembled unique paths in the past and future, respectively; odors at positions in between were the same and thus resembled a common path. We trained classifiers using neural activity to distinguish between either sequences or positions and asked whether the neural activity patterns in the common path were more like the ones in the past or the future. We found a proximal prospective code for sequence information as well as a distal perspective code for positional information, the latter of which was closely associated with rats' ability to predict future outcomes. This study demonstrates a behaviorally relevant predictive code in rat OFC.

Approaches and considerations of studying neuronal ensembles: a brief review

“…Single neurons photoconverted functionally in vivo were sorted by fluorescence using FACS for RNA-seq analysis ( O’Toole et al, 2023 ) demonstrating an enrichment in specific neuronal cell types within the CaMPARI2-tagged neuronal ensemble. While these calcium-based approaches are related to firing activity and offer many benefits to studying neuronal ensembles in vivo and ex vivo , they may overestimate the number of neuronal ensembles by tagging cells that, while active, are not explicitly responding to the specific stimuli ( Liang et al, 2018 ; Tsuda, 2020 ; Zhou et al, 2021 ).…”