Cortical Stimulation Improves Skilled Forelimb Use Following a Focal Ischemic Infarct in the Rat Campbell Teskey et al, 2003

Background Brain plasticity may explain recovery of impaired function Rehabilitative training has shown clear benefits for functional recovery Electrical stimulation: –In humans there is anecdotal evidence that motor cortex stimulation improves motor performance –In nonhumans it has shown to be effective at potentiating and depressing synaptic strength in the neocortex –In nonhumans it also alters movement representations that have shifted due to focal ischemic lesions Pulsed electrical stimulation has been shown to facilitate peripheral neuronal growth

Purpose To determine if a combination of rehabilitative training with cortical electrical stimulation will augment brain plasticity, therefore improving functional recovery

Methods 75 male, Long-Evans Behavioral Training: Pasta Matrix Task Surgery: Rats underwent a craniotomy and received a cortical stimulation electrode Evoked Potential Cortical Surface Stimulation Histology Statistical Analysis

Results Figure A: –100Hz displayed significantly greater reaching success than no stimulation on all test days –250 Hz –no stimulation group displayed significantly reduced performance on all 10 assessment days Figure B: –Performance on pasta matrix task

Results Figure A1 and B1: –Rats switched back and forth between preferred and non-preferred to retrieve more distal pieces during pre-infarct training Figure A2 and B2: –A2: 0 Hz rat on first test day –B2: 50 Hz rat on first test day Figure A3 and B3: –A3: 0 Hz rat on 10 th test day –B3: 50 Hz rat on 10 th test day

Results Figure A : –Rats receiving no electrical stimulation Figure B : –Rats receiving 50 Hz stimulation

Results Polysynaptic Potentiation Figure A: –Neocortical evoked response –Shows synapses are taking longer to stop firing…so more synapses recruited Figure B: –10 days of cortical stimulation –Animals with 50 Hz or greater had larger polysynaptic potentiation

Results Movement Thresholds : –After 10 days of cortical stimulation the movement threshold of rats that received cortical stimulation was significantly reduced –Time and frequency are important

Kleim et al Findings Examined the behavioral and physiological effects of cortical stimulation in combination with motor rehabilitation NS= no stimulation BCS= Bipolar Cathodal Stimulation MCS= Monopolar Cathodal Stimulation MAS= Monopolar Anodal Stimulation

Conclusions Shows that 20 minutes of continuous cortical stimulation concurrent with skilled forelimb usage results in superior reaching performance In the pasta reaching task the animals that received no cortical stimulation had use of both forelimbs drastically decreased Rats with stimulation also shifted to their non-preferred limb and showed same amount of persistence and energy as they did with their previous preferred limb Movement thresholds were significantly reduced in rats that received Hz stimulation

Future Directions Look at the relationship between frequency of cortical stimulation, neocortical polysynaptic potentiation and a long- term superior skilled performance Optimize the electrical parameters of the cortical stimulation Look at the cortical stimulation phenomenon in other brain regions Examine the persistence of recovery