To evaluate the effects of electric cortical stimulation in the experimentally induced focal traumatic brain injury (TBI) rat model on motor recovery and plasticity of the injured brain.
Twenty male Sprague-Dawley rats were pre-trained on a single pellet reaching task (SPRT) and on a Rotarod task (RRT) for 14 days. Then, the TBI model was induced by a weight drop device (40 g in weight, 25 cm in height) on the dominant motor cortex, and the electrode was implanted over the perilesional cortical surface. All rats were divided into two groups as follows: Electrical stimulation (ES) group with anodal continuous stimulation (50 Hz and 194 µs duration) or Sham-operated control (SOC) group with no electrical stimulation. The rats were trained SPRT and RRT for 14 days for rehabilitation and measured Garcia's neurologic examination. Histopathological and immunostaining evaluations were performed after the experiment.
There were no differences in the slice number in the histological analysis. Garcia's neurologic scores & SPRT were significantly increased in the ES group (p<0.05), yet, there was no difference in RRT in both groups. The ES group showed more expression of c-Fos around the brain injured area than the SOC group.
Electric cortical stimulation with rehabilitation is considered to be one of the trial methods for motor recovery in TBI. However, more studies should be conducted for the TBI model in order to establish better stimulation methods.
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To evaluate motor excitability and hand function on the non-dominant side according to the polarity of transcranial direct current stimulation (tDCS) on the motor cortex in a healthy person.
tDCS was applied to the hand motor cortex for 15 minutes at an intensity of 1 mA in 28 healthy right-handed adults. Subjects were divided randomly into four groups: an anodal tDCS of the non-dominant hemisphere group, a cathodal tDCS of the non-dominant hemisphere group, an anodal tDCS of the dominant hemisphere group, and a sham group. We measured the motor evoked potential (MEP) in the abductor pollicis brevis and Jabsen-Taylor hand function test (JTT) in the non-dominant hand prior to and following tDCS. All study procedures were done under double-blind design.
There was a significant increase in the MEP amplitude and a significant improvement in the JTT in the non-dominant hand following anodal tDCS of the non-dominant hemisphere (p<0.05). But there was no change in JTT and a significant decrease in the MEP amplitude in the non-dominant hand following cathodal tDCS on the non-dominant hemisphere and anodal tDCS of the dominant hemisphere.
Non-dominant hand function is improved by increased excitability of the motor cortex. Although motor cortex excitability is decreased in a healthy person, non-dominant hand function is maintained. A homeostatic mechanism in the brain might therefore be involved in preserving this function. Further studies are warranted to examine brain functions to clarify this mechanism.
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