EXPRESS: Normal Aging Limits Cortical Network Reorganization and Behavioral Recovery after Experimental Stroke.

Background: Although advancing age is associated with worse recovery after stroke, little is known about how aging influences post-stroke reorganization of neuronal circuits and networks.

Methods: We used wide-field calcium imaging to compare cortical network dynamics and behavioral recovery after focal photothrombotic stroke in forepaw somatosensory cortex in young (3-month-old) and aged (18-month-old) Thy1-GCaMP6f mice.

Results: Both young and aged mice developed significant somatomotor deficits after stroke, but only young mice exhibited substantial behavioral recovery. While young and aged mice showed differences in baseline forepaw-evoked response amplitudes and their trajectories after stroke, the temporal dynamics of these circuits were comparable both before and after stroke between young and aged mice. Relative to aged mice, young mice demonstrated superior baseline measures of hemispheric stimulus-locked fidelity, bilateral coherence, and cortical entrainment, that declined significantly after stroke; this trend was absent in aged mice. Finally, only young mice showed significant recovery of somatosensory and somatomotor functional connectivity after stroke.

Conclusions: These results suggest similarities in neuronal network degradation caused by aging and stroke and highlight the vulnerability of neuronal networks in both processes. Our findings also indicate a potential network-level basis for chronic deficits in stroke survivors.