been trained in. additionally, the control, non-dancers, showed significantly less brain activation in the mirror motor neurons when watching either type of dance. this research provides insight into how the brain responds to movements you have personally learned to do. this may provide a way to allow professionals to maintain a skill without actually performing the movement. or it may provide an outlet for mental rehabilitation to those with impaired motor skills. simple observation of the movement allows the same type of brain stimulation as the actual physical movement. preparatory changes in neuronal activity execution of certain motor tasks requires an instructed delay. this delay period occurs in between the instructed cue and the subsequently triggered movement. during these delay periods preparatory changes occur in neuronal activity. the primary motor cortex, the pre-motor cortex, the supplementary motor area, parietal cortex, and the basal ganglia all may experience these preparatory delay periods. these activities coordinate during the delay periods and reflect movement planning in accordance with the instructional cue and the subsequent movement but occur prior to muscle activity. the movement planning may be anything from the direction of the movement to the extent of the movement. short lead changes vs. long lead changes premovement neuronal activity has been widely experimented upon in three major motor fields of the frontal cortex. the goal of this experimentation is to compare the neuronal activity which comes from visual signals, versus neuronal activity which comes from non-triggered or self-paced movements. from this comparison, two changes were identified, occurring at different time scales in relation to the onset of movement. these changes are the short lead and long lead changes. the short lead changes are observed about 480ms before the movement, whereas the long lead changes occur about 1–2 seconds earlier. the short lead changes are exhibited in the sma (supplementary motor area) and the pm (pre-motor area) during both the visual signal trials and the non-triggered/self-paced trials. the pre-central motor cortex was also identified in this study as having similar neuronal activities as in the pm and sma. experimentation found that approximately 61% of the neurons in the pm were preferentially related to the triggered (visual) movements. the long lead neuronal changes were more frequently active during the self paced stimuli than before the triggered movements. these long lead changes are particularly abundant among the sma neurons. in summation, these experiments challenged the idea that the sma primarily takes part in self-paced movements and the pm is only involved in visually triggered movements. although the pm neurons showed more preference for the visual trigger signals and the sma neurons are intimately related to initiation of self paced movements, both are involved with premovement for both types of stimuli. link between the cortex and basal ganglia a subcortical loop exists within the brain linking upper motor neurons originating in the primary motor and pre-motor cortices and the brainstem, with the basal ganglia. these upper motor neurons eventually initiate movement by controlling the activity of lower motor neurons, located in the brainstem and spinal cord, and project out to innervate the muscles in the body. upper motor neurons also modulate activity of local circuit neurons, whose synapses are a large input to these lower motor neurons, in turn affecting subsequent movement. thus, the basal ganglia indirectly influence movement via regulation of the activity of the upper motor neurons, which ultimately determine activity of the lower motor neurons. areas of basal ganglia affect movement the basal ganglia include groups of motor nuclei located deep within the cerebral hemispheres, including the corpus striatum, which contains two nuclei named the caudate and putamen, and also the pallidum, which contains the globus pallidus and substantia nigra pars reticulate. the corpus striatum is the main input center of the basal ganglia, specifically upper neurons of motor areas in the frontal lobe that control eye movement link to neurons in the caudate, while upper neurons from pre-motor and motor cortices in the frontal lobe connect to neurons in the putamen. the main neurons found within these structures are named medium spiny neurons. activation of medium spiny neurons the activation of medium spiny neurons is generally associated with the occurrence of a movement. extracellular recording have shown that these specific neurons increase their rate of discharge before an impending movement. such anticipatory discharges seem to be involved in a movement selection process, can precede a movement by several seconds, and vary according to location in space of the destination of the movement. processing movement signals by the basal ganglia the neurons present in the global pallidus and substantia nigra are the main output areas of the basal ganglia. these efferent neurons influence activity of the upper motor neurons. neurons in these areas are gabaergic, and thus the main output of the basal ganglia is inhibitory, and spontaneous activation of these neurons consistently prevents unwanted movement. the input of medium spiny neurons to these output areas of the basal ganglia are also gabaergic and therefore inhibitory. the net effect of excitatory inputs to the basal ganglia from the cortex is inhibition (via the medium spiny neurons) of the persistently active inhibitory cells in the output center of the basal ganglia. this double inhibitory effect leads to activation of upper motor neurons, which causes subsequent signaling of local-circuit and lower motor neurons to initiate movement. this pathway is defined as the direct pathway through the basal ganglia. there is another indirect pathway present between the corpus striatum and part of the globus pallidus. this indirect pathway also involves the subthalamic nucleus (a part of the thalamus), which receives signals from the cerebral cortex. excitatory signals from the cortex will activate subthalamic neurons, which are excitatory also. thus, this indirect pathway serves to reinforce inhibition by excitatory signals to the gabaergic cells present in the globus pallidus. in effect, this pathway regulates the direct pathway by feeding back onto the output centers of the basal ganglia. the balance between these two pathways processes movement signals and influences the initiation of an impending movement. movement disorders and future research the bereitschaftspotential has also been found to be influenced by movement disorders such as parkinson's disease (pd), cerebellar lesions, and degenerative diseases of the dentate nucleus. since at least some part of the bp originates from the sma, "which receives main dopaminergic input from the basal ganglia via thalamus", many are conducting studies of bp in patients with parkinson's disease (pd). it has also been found that people with cerebellar lesions have clear abnormalities in their bp. in patients with degenerative diseases of dentate nucleus there is virtually a complete lack of bp. in patients with cerebellar hemispheric lesions the bp is much smaller again or even absent. of all the movement disorders studied, parkinson's is by far the most investigated. most experiments have studied the effects of lesions on the bp in patients with parkinson's disease. it was observed that the amplitude of bp in many parkinson's patients was significantly reduced. a bp with a more positive polarity was observed compared to the bp in control patients without the disease. other research shows the same reduction in amplitude of movement-related cortical potentials, which is consistent with other studies showing a decrease in the activation of the sma in parkinson's patients. a decreased ability to terminate premovement preparatory activity has been observed in parkinson's patients, reflected by prolonged activity in the sma . this prolonged activity may have to do with impaired function of the basal ganglia, which is thought to send a termination signal to the sma. while changes in preparatory movement activity are present in pd patients, executed-movement processes in the brain seem to be unaffected, suggesting that premovement activity abnormality may underlie the difficulty in movement prevalent in parkinson's disease. more research studying the effects of the disease on mrcps (like the bp) and premovement preparatory activity in pd patients is ongoing.