Environmental enrichment mitigates stroke-induced change in sharp-wave associated ripple characteristics

Cognitive and memory impairments are common sequelae after stroke, yet it is not well understood how middle cerebral artery (MCA) stroke chronically affects the neural activity of the hippocampus, a brain region critical for memory function but remote from the stroke epicenter. Environmental enrichment (EE) has been shown to improve cognition following stroke; however, the electrophysiology that underlies this behavioral intervention is still elusive. We recorded local field potentials simultaneously from sensorimotor cortex and hippocampus in rats following MCA occlusion and subsequent EE treatment. We found that stroke increased duration and power of sharp-wave associated ripples (SPW-Rs), altered brain state, and disrupted phase amplitude coupling (PAC) within the hippocampus and between the cortex and hippocampus. EE counteracted stroke-induced increase in SPW-R characteristics but did not restore hippocampal brain state or PAC. Our results suggest that these brain oscillatory changes are novel biomarkers underlying stroke-induced cognitive impairment and the recovery from EE.