In the motor system, several studies have used DCM to detect causal information flow from secondary to primary motor areas during simple movements and bimanual coordination (Grefkes et al., Neuroimage, 2008).
The results of this study both extend those of Eisenberg et. al. (2010), to demonstrate direction encoding throughout the motor system (consistent with neuophysiological studies in non-human primates), and further support the use of fMRI-A as a valuable tool for studying the information encoded by sensorimotor regions of the central nervous system.
Over the last two decades, transcranial magnetic stimulation (TMS) has proven to be an appropriate tool to study motor system excitability in neurological disorders [ 2] and psychiatric disorders [ 3, 4] but also to study the effects of CNS active drugs [ 5].
The motor system has been intensively studied using the emerging neuroimaging technologies over the last twenty years.
We believe that the selective compendium we provide can supplement calls arguing for renewed interest in studying the motor system in schizophrenia.
For that reason, time series residuals in connectivity measurement may more appropriately stand in for the steady-state data which has been used to study the motor system [25] and the visual system [26], though this has not been tested directly.
Motor system excitability cannot only be studied with subjects at rest, but also while performing a motor control task [ 1].
In fact, facial nerve axotomy in rodents has been widely used for studying vibrissal motor system plasticity at different levels [ 10].
RS paradigms have recently been used in combination with functional magnetic resonance imaging (fMRI) to study the motor system during observation of goal-directed movements (Hamilton and Grafton 2006, 2007, 2008; Kable and Chatterjee 2006).
Therefore, since EEG phase estimation is very sensitive to noise, instantaneous EEG beta phase will be more reliable when amplitude is high (e.g., during rest) than when beta is suppressed (i.e., during motor activity), highlighting the importance of studying the motor system during rest to be able to reliably detect basic mechanisms.
