Enriched Rehabilitative Training Promotes Improved Forelimb Motor Function and Enhanced Dendritic Growth after Focal Ischemic Injury

TLDR

Forelimb and digit motor deficits after stroke are common and persist despite therapy, although environmental enrichment alone improves behavioral outcomes but not fine motor function. The study aimed to determine whether combining environmental enrichment with daily skilled‑reach training enhances long‑term forelimb function after focal ischemia. Adult rats received endothelin‑1–induced focal ischemia or sham surgery, then were assigned to enriched‑rehabilitation or standard housing starting 15 days post‑injury, with forelimb performance and dendritic arborization of layer V pyramidal cells assessed. Enriched‑rehabilitation produced a ~30 % improvement on the staircase‑reaching task and restored beam‑traversal performance to sham levels, while also increasing dendritic complexity in the undamaged motor cortex, indicating that task‑specific training combined with enrichment promotes functional recovery and neuronal plasticity.

Abstract

Chronic impairment of forelimb and digit movement is a common problem after stroke that is resistant to therapy. Previous studies have demonstrated that enrichment improves behavioral outcome after focal ischemia; however, postischemic enrichment alone is not capable of enhancing fine digit and forelimb function. Therefore, we combined environmental enrichment with daily skilled-reach training to assess the effect of intensive task-specific rehabilitation on long-term functional outcome. Rats were subjected to either endothelin-1-induced focal ischemia or sham surgery and subsequently designated to enriched-rehabilitation or standard-housing treatment groups starting 15 d after ischemia. Functional assessment of the affected forelimb at 4 and 9 weeks after treatment revealed that ischemic plus enrichment (IE) animals had improved ∼30% on the staircase-reaching task and were indistinguishable from sham animals for both latency and foot faults in a beam-traversing task. In contrast, ischemic plus standard (IS) animals remained significantly impaired on both tasks. Interestingly, both ischemic groups (IE and IS) relied on the nonaffected forelimb during upright weight-bearing movements, a pattern that persisted for the duration of the experiment. Dendritic arborization of layer V pyramidal cells within the undamaged motor cortex was examined using a Golgi–Cox procedure. IE animals showed enhanced dendritic complexity and length compared with both IS and sham groups. These results suggest that enrichment combined with task-specific rehabilitative therapy is capable of augmenting intrinsic neuronal plasticity within noninjured, functionally connected brain regions, as well as promoting enhanced functional outcome.