A method for monitoring intra-cortical motor cortex responses in an animal model of ischemic stroke

Neuroplasticity is believed to play a key role in functional recovery after stroke. Neuroplastic effects can be monitored at the cellular level via e.g. neurotransmitter assessment, but these studies require sacrifice of the animal. FMRI can be used to assess functional neuronal performance, but the spatial and temporal resolution is far from the single cell level. The objective was to establish an effective method for short-term analysis of single and multi-unit electrophysiological function before, during and after stroke. We instrumented one rat with a 16-ch array in the primary motor cortex (100 mum wire diameter) to monitor cortical activity. A bipolar cuff electrode was implanted around the Ulnar nerve in the contralateral forelimb to provide a controlled electrical stimulus input to the sensory-motor system. A 3 mm diameter ischemic infarct was created immediately posterior to the electrode array by light activation of a photosensitive dye (Rose Bengal, 1.3 mg/100 mg body weight) at the cortical surface. M1 activity in response to the peripheral electrical stimulus was recorded before, during and after the cortical ischemic infarct. At 425 min following ischemic infarct the peak peri-stimulus time response had decreased to 30plusmn11% (electrodes placed 1.5 mm from the infarct core) of the activity before the ischemic onset. The mean response latency increased from 30.1plusmn4.5 ms (before infarct) to 40.6plusmn8.5 ms (at 425 min). This dynamic view of neuroplasticity may eventually assist in optimizing acute stroke therapies and optimize functional recovery further