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Tanaka, K. Z.

Publications and source records attributed to Tanaka, K. Z..

3 recordsLinked to original sources

Artificial hibernation uncovers distinct interaction dynamics in functional and pathological state change

Neural population activity can reorganize without disrupting function, but how such changes differ from those associated with pathology remains unknown. Artificial hibernation, Q-neuron-induced hypothermia and hypometabolism (QIH), causes extensive synaptic remodeling in the hippocampus without erasing established memories, allowing us to examine how extensive network reorganization can occur without lasting functional impairment. Longitudinal calcium imaging showed that hippocampal activity recovered after QIH without returning to its pre-hibernation population configuration. Instead, QIH reorganized neuronal activity patterns and coactivity beyond representational drift. Electrophysiological recordings revealed that this reorganization of neuronal interactions depended on the preceding network state. In mice subjected to kainic acid-induced status epilepticus, QIH reduced seizure-associated increases in neuronal interactions and spike coactivity during sharp-wave ripples. Over the following 50 days, the divergence of hippocampal LFP trajectories was constrained, and the progressive development of electrophysiological and histological pathology was attenuated. These findings suggest that controlled, extensive reorganization of neural population activity can prevent the progression toward pathological network states, with changes in neuronal interactions, particularly sharp-wave ripple-associated coactivity, accompanying this process.

neuroscience↗

Artificial hibernation uncovers distinct synaptic engram architecture for memory retention

The memory trace at the neuronal and synaptic levels remains controversial. Stable, larger spines are thought to support memory, but the high turnover of dendritic spines and the drifting of neuronal representations following memory formation suggest alternative possibilities. To elucidate a structural trace underlying memory retention, we utilize a mouse model of artificial hibernation. During hibernation, hippocampal neurons exhibited a substantial reduction in their activity and an extensive elimination of dendritic spines and synapses. Despite these changes, their memory and associated hippocampal neuronal representations are intact after arousal. We find that a subset of spines is maintained during hibernation. These spatially clustered engram-engram synapses are exclusively protected from elimination and characterized by synaptic contacts with multi-synaptic boutons. These findings suggest that synaptic engram architecture, rather than larger spines per se, is resilient to network remodeling and underlies long-term memory retention.

neuroscience↗

Dentate neurogenesis mediates cognitive flexibility via modulation of the hippocampal longitudinal-axis network

Adult neurogenesis endows the hippocampus with unparalleled neural plasticity, essential for intricate cognitive functions. However, the manner in which sparse newborn neurons (NBNs) modulate neural activities and subsequently shape behavior remains enigmatic. Utilizing a newly engineered NBN-Tetanus Toxin mouse model, we non-invasively silenced NBNs and confirmed their crucial role in cognitive flexibility, as demonstrated through reversal learning in the Morris water maze and the Go/Nogo task in operant learning. Pairing task-based functional MRI (tb-fMRI) with operant learning revealed a dorsal hippocampal hyperactivation during Nogo task, implying that hippocampal hyperexcitability might underlie the observed behavioral deficits. Notably, resting-state fMRI (rs-fMRI) revealed enhanced functional connectivity between the dorsal and ventral dentate gyrus following NBN silencing. Further exploration of PV+ interneurons and mossy cells activities highlighted NBNs integral part in preserving the excitation/inhibition balance within the hippocampus. Our findings emphasize how the neural plasticity driven by NBNs extensively modulates the hippocampus, sculpting cognitive flexibility.

neuroscience↗