Neural Subspace Research Articles

The Transition from Evaluation to Selection Involves Neural Subspace Reorganization in Core Reward Regions

Economic choice proceeds from evaluation, in which we contemplate options, to selection, in which we weigh options and choose one. These stages must be differentiated so that decision makers do not proceed to selection before evaluation is complete. We examined responses of neurons in two core reward regions, orbitofrontal (OFC) and ventromedial prefrontal cortex (vmPFC), during two-option choice with asynchronous offer presentation. Our data suggest that neurons selective during the first (presumed evaluation) and second (presumed comparison and selection) offer epochs come from a single pool. Stage transition is accompanied by a shift toward orthogonality in the low-dimensional population response manifold. Nonetheless, the relative position of each option in driving responses in the population subspace is preserved. The orthogonalization we observe supports the hypothesis that the transition from evaluation to selection leads to reorganization of response subspace and suggests a mechanism by which value-related signals are prevented from prematurely driving choice.

Shaping Reality through Mental Rehearsal

Previous research has shown that mental rehearsal can improve performance. A new study by Vyas etal. (2018) reveals that direct modulation of neural dynamics using a brain-computer interface can also modify physical movements. The study further demonstrates that "mental practice" and physical movements share a common neural subspace.

Better Risk Management

<h3>Abstract</h3> Cortical neurons show distinct firing patterns across multiple task-epochs characterized by distinct computational aspects. Recent studies suggest that such distinct patterns underly dynamic population code achieving computational flexibility, whereas neurons in some cortical areas often show coherent firing patterns across epochs. To understand how such coherent single-neuron code contribute to dynamic population code, we analyzed neural responses in the perirhinal cortex (PRC) during cue and reward epochs of a two-alternative forced-choice task. We found that the PRC neurons often encoded the opposite choice-directions between those epochs. By using principal component analysis as population-level analysis, we identified neural subspaces associated with each epoch, which reflected coordinated patterns across the neurons. The cue and reward epochs shared neural dimensions where the choice directions were consistently discriminated. Interestingly, those dimensions were supported by dynamically changing contributions of individual neurons. These results indicated heterogeneity of coherent single-neuron responses in their contribution to population code.