Neurophysiological and behavioral concomitants of mild brain injury in collegiate athletes

Objectives: There is still limited understanding regarding the effect of mild brain injury (MBI) on normal functioning of the human brain with respect to motor control and coordination. To our knowledge, no research exists on how both the accuracy of force production and underlying neurophysiological concomitants are interactively affected by MBI. The aim of this study is to provide empirical evidence that there are at least transient functional changes in the brain associated with motor control and coordination in collegiate athletes suffering from MBI as reflected in alterations of force trajectory patterns and electroencephalogram (EEG) potentials both in time and frequency domains. Methods: Comparisons of the performance and concomitant EEG waveforms both in time and frequency domains of 6 collegiate athletes with MBI and 6 normal subjects in a series of isometric force production tasks were made. The traditional averaging techniques to obtain the slow-wave movement-related potentials (MRP) and Morlet wavelet transform to obtain EEG time-frequency (TF) profiles associated with task performance were used. Subjects performed isometric force production tasks when the level of nominal force was experimentally manipulated. EEG recordings from the frontal-central areas were analyzed with respect to the accuracy of force production during the ramp phase. Results: Behaviorally, the accuracy of force trajectory performance was considerably impaired in MBI subjects even when the amount of task force was only increased from 25 to 50% maximum voluntary contraction (MVC) within a given subject. Electro-cortically, impaired performance in MBI subjects was associated with alterations in EEG waveforms, amplitude of MRP and TF profiles of EEG. Conclusions: Both behavioral and electro-cortical data of control subjects generally were comparable with those from subjects with MBI when small amounts of force were regulated. However, differences become apparent as the amount of task force production was increased. Overall our findings identify the presence of transient functional changes in the brain associated with motor control and coordination in subjects suffering from MBI.