Biology subjects

Zutshi, I.

Publications and source records attributed to Zutshi, I..

3 recordsLinked to original sources

bioRxiv2026

Hippocampal and prefrontal contributions to memory-guided navigation depend on task epoch

The hippocampus and medial prefrontal cortex (mPFC) are required for delayed working-memory tasks, but when in the task their engagement becomes necessary remains an open question. We trained mice on a delayed cue-guided T-maze navigation task and used transient optogenetic silencing to test the contribution of the mPFC and hippocampus during distinct task epochs. Surprisingly, silencing during the delay period did not impair performance. In contrast, perturbation during the early phase of the central arm traversal produced robust deficits. Mice made more perseverative choices, slowed their speed and ran farther down the track before turning towards the selected arm. Control experiments showed that these effects could not be explained by the manipulation targeting elapsed time and were rather specific to task phase. These results indicate that hippocampal and prefrontal contributions to memory-guided behavior are not uniform across the trial, but instead depend on task epoch. More broadly, they suggest that the functional engagement of these circuits is gated by behavioral state or context.

neuroscience↗

bioRxiv2025

From labels to latents: revealing state-dependent hippocampal computations with Jump Latent Variable Model

Neural activity is usually interpreted by imposing external labels (e.g., stimuli or position during locomotion) and decoding within that space (e.g. replay). While powerful, such supervision can mask structure in the data that do not correspond to the label. Unsupervised methods, in turn, often assume smooth latent dynamics and miss genuine discontinuities. We introduce a conceptually simple, computationally efficient latent variable model that infers both (i) the latent variables organizing population activity and (ii) whether their dynamics are continuous or fragmented in time. Fitting reduces to an expectation-maximization (EM) procedure that alternates two operations familiar to systems neuroscience--tuning-curve estimation and label decoding--without requiring external labels. Applied to rodent hippocampal spike recordings, the model reveals distinct population patterns at the same physical position that supervised spatial decoding fails to detect. While learned latents exhibit place-field-like tuning, their reactivation patterns are better distinguished by behavioral states. The model further identifies a continuity-fragmentation axis that characterizes population activities across sleep-wake brain states that is modulated by cholinergic inputs. By not relying on externally imposed spatial labels, our approach exposes structure that supervised approaches obscure and provides a powerful tool for datasets lacking behavioral tracking.

neuroscience↗

bioRxiv2024

Hippocampal neuronal activity is aligned with action plans

Neurons in the hippocampus are correlated with different variables, including space, time, sensory cues, rewards, and actions, where the extent of tuning depends on ongoing task demands. However, it remains uncertain whether such diverse tuning corresponds to distinct functions within the hippocampal network or if a more generic computation can account for these observations. To disentangle the contribution of externally driven cues versus internal computation, we developed a task in mice where space, auditory tones, rewards, and context were juxtaposed with changing relevance. High-density electrophysiological recordings revealed that neurons were tuned to each of these modalities. By comparing movement paths and action sequences, we observed that external variables had limited direct influence on hippocampal firing. Instead, spiking was influenced by online action plans modulated by goal uncertainty. Our results suggest that internally generated cell assembly sequences are selected and updated by action plans toward deliberate goals. The apparent tuning of hippocampal neuronal spiking to different sensory modalities might emerge due to alignment to the afforded action progression within a task rather than representation of external cues.

neuroscience↗