Poster Z12 - Alterations in Neuronal Stochasticity in the Fischer 344 Rats Model of Somatosensory Processing by Ultra High-density Neuropixels Electrode

Introduction: Advanced recording tools such as Neuropixels probes have transformed the monitoring of brain activity via electrophysiology. These next-generation electrodes can record from larger neuronal populations across multiple brain regions to deepen our understanding of brain function in health and disease.
As the global population ages, the prevalence of dementia and its impact on families, society, and healthcare systems is mounting. Notwithstanding, some elderly individuals retain exceptional cognitive performance well into their eighth decade of life. A factor underlying such brain resilience could be the stochasticity in individual neuronal involvement during network activation.
Recent studies indicate that healthy brain function undergoes continuous remodeling of neuronal properties even under stable environmental and behavioral conditions. This basal plasticity likely leads to ongoing, activity-independent synaptic changes contributing to the stochastic responsiveness of neurons to stimulation. In the current study, we hypothesize that lower trial-dependent variation in the neurons activated by repetitive stimuli leads to greater impairment with aging. To test this hypothesis, we leveraged Neuropixels probes to record the activity of hundreds of neurons in the brain with high spatial and temporal resolution.

Materials and

Methods: At 11.5 months of age, Fischer 344 rats were trained on the Barnes maze and their spatial memory task and cognitive flexibility subsequently tested (1 day of probe trial, 5 days of reversal trials). At 12 months of age, the neuronal stochasticity in the somatosensory cortex and hippocampus was evaluated via Neuropixels recordings. A 1-minute baseline of pre-stimulation activity was recorded. Then repetitive electrical stimulation was administered to the contralateral forepaw. This consisted of 10 trials, each lasting 1 minute and containing 187 stimuli per trial (3 mA, 333 µs pulse duration, 3 Hz). This stimulation aimed to elevate neuronal activity in the targeted brain regions.

Results, Conclusions, and Discussions: Our findings indicate that cognitively impaired rats display altered across-trial neuronal response rate, reduced number of responsive neurons, and diminished high-frequency oscillatory activity in the hippocampus compared to their non-transgenic littermates. In the next steps, we aim to provide a detailed spatial characterization of neuronal volatility over the course of aging in Fischer 344 rats and determine the role of neuronal volatility in cognitive decline associated with aging. The final results will help our understanding of age-related cognitive changes and contribute to interventions aimed at preserving cognitive function in elders, helping them maintain functional independence and effective communication with others.

Acknowledgements (Optional):