Task-stage-specific modes of beta frequency coordination in the hippocampal-prefrontal network.

Cognitive tasks typically consist of multiple stages with distinct computations. Yet, how oscillatory dynamics across distributed brain networks switch to support the computations required for each task stage remains poorly understood. The hippocampal-neocortical networks show prominent beta oscillations (15-30 Hz), which are hypothesized to facilitate long-range interactions required for a range of spatial, operant, and cue-based tasks. However, it is unknown how beta oscillations differentially modulate the hippocampal-neocortical networks to support specific cognitive processes for each task stage. To characterize beta oscillatory dynamics in hippocampal-neocortical networks, we recorded local field potential and single-unit activity in the CA1 region of the hippocampus and the prefrontal cortex (PFC) of the neocortex while rats performed an odor-guided two-alternative forced-choice task. We focused on two task stages requiring different cognitive processes: cue sampling and goal attainment. We found that these two stages showed unique patterns of beta-frequency coordination between the CA1 and PFC, including beta-subband-specific differences. Furthermore, we found that ensemble spiking activity patterns in the CA1 and PFC distinguished between the two task stages, with the CA1 expressing spatial and the PFC expressing nonspatial task correlates. Beta oscillations also showed task-stage-specific phase modulation of subsets of the CA1 and PFC populations. Our findings demonstrate that beta-frequency coordination in hippocampal-neocortical networks switches between functional modes, reconfiguring these networks to support the computational requirements for distinct stages within a cognitive task.NEW & NOTEWORTHY Our results demonstrate that beta-frequency dynamics in hippocampal-neocortical networks switch between distinct functional modes to support different cognitive processes within a task. These findings support the hypothesis that the hippocampus and neocortex may be members of different functional brain networks during different cognitive processes modulated by beta oscillations.