Nitsche et al. (2003) sought to build on previous research pointing to the idea that the primary motor cortex plays a direct role in motor learning by way of acquisition and early consolidation learning (Müllbacher et al., 2002; Nudo, Milliken, Jenkins, & Merzenich, 1996; Jacobs & Donoghue, 1991). Specifically, implicit motor learning, where the subject has no awareness of learning taking place, was studied when subjects were given Transcranial Direct Current Stimulation (tDCS) (2003). Transcranial Direct Current Stimulation may be described as implanting electrodes in a subject’s brain and sending a current of electricity through the electrodes in an attempt to change the brain activity in the region of the implanted electrodes (2003). This …show more content…
Each participant participated in only one electrode position condition (primary motor, premotor, or prefrontal cortices), however each subject received anodal, cathodal, and noncurrent stimulation, each at different times separated by at least a week (2003). Nitsche et al. (2003) used a serial reaction time task to measure the level of motor learning (faster times relative to previous block reaction time performance meant evidence of implicit motor learning) while introducing tDCS in subjects’ primary motor, premotor, or prefrontal cortices (2003). Subjects were asked to perform finger movement tasks repetitively on a computer, and afterward were asked if they noticed an order in the tasks and then, if so, what it was (2003). Response time was measured from when the directional “go” signal appeared to when the subject first pushed the corresponding button over 8 blocks of 120 trials (2003). The tDCS was applied during the finger tasks (2003). A control experiment with random sequences was performed as well to control for a threat to internal validity that may have been present in the study; specifically within the order of the finger movement tasks (2003). Random assignment was used for the assignment of region of cortex stimulated, the order of stimulation conditions and the handedness of subjects within each group (2003). The method used was appropriate based on the hypotheses …show more content…
Subjects were not aware of any repeated sequences during the experiment, as well (2003). The primary motor cortex was also the only brain region during the study that presented results which suggested anodal stimulation increased performance (2003). These results infer strong support for the original hypotheses of the study for a few reasons. First, anodal stimulation led to increased performance in the acquisition and early consolidation phase of motor learning (2003) through the reaction time test, thereby modulating implicit learning, as predicted in the first hypothesis (a) by the researchers. Second, the fact that no participant was able to identify any sequences during the experiment indicates that only implicit learning was occurring, firmly supporting the second hypothesis (b) that the frontal cortices are directly involved with implicit motor