Tang W*, Shin JD*, Jadhav SP (2021), “Multiple time-scales of decision making in the hippocampus and prefrontal cortex”, eLife, 10, e66227.
In this study, we establish neural population sequences at multiple timescales in the hippocampus and prefrontal cortex, and determine their complementary roles in memory-guided decision making. We demonstrate neural population sequences at multiple timescales in the hippocampus and prefrontal cortex, with fast timescales on the order of ~100ms for theta sequences and sharp-wave ripple replay events, and slow timescales on the order of ~seconds for trajectory-dependent firing sequences or “splitter” sequences during behavior. These choice-specific sequences at the behavioral timescale, i.e. trajectory-dependent firing in both CA1 and PFC predicted future choices throughout learning, as expected. In addition, we found compressed theta sequences in both CA1 and PFC nested within behavioral timescale sequences during navigation. We establish PFC theta sequences, PFC theta cycle skipping, and also memory-dependent look ahead of PFC theta sequences, similar to CA1. CA1 theta sequences encoded both actual and alternative choices during decision making, but could not predict upcoming choice. In contrast, PFC theta sequences and coherent CA1-PFC theta sequences predicted actual choice. Thus, theta sequences can support vicarious memory recall. Behavioral timescale or theta sequences could not predict errors. Rather, compressed timescale replay sequences during sharp-wave ripples in inter-trial periods prior to trajectory onset prime decisions, and errors in CA1-PFC replay predict incorrect decisions.
We thus integrate hippocampal and prefrontal behavioral sequences, theta sequences and replay sequences in a unified framework for memory-guided decision making. These results show that transient dynamics at fast, cognitive timescales can support decisions, and establish cooperative interaction of sequences at multiple timescales for decision making.
We have some neat theta sequence decoding videos for the paper:
Theta Sequence Videos.