RESUMEN
It has been demonstrated that during motor responses, the activation of the motor cortical regions emerges in close association with the activation of the medial frontal cortex implicated with performance monitoring and cognitive control. The present study explored the oscillatory neurodynamics of response-related potentials during correct and error responses to test the hypothesis that such continuous communication would modify the characteristics of motor potentials during performance errors. Electroencephalogram (EEG) was recorded at 64 electrodes in a four-choice reaction task and response-related potentials (RRPs) of correct and error responses were analysed. Oscillatory RRP components at extended motor areas were analysed in the theta (3.5-7 Hz) and delta (1-3 Hz) frequency bands with respect to power, temporal synchronization (phase-locking factor, PLF), and spatial synchronization (phase-locking value, PLV). Major results demonstrated that motor oscillations differed between correct and error responses. Error-related changes (1) were frequency-specific, engaging delta and theta frequency bands, (2) emerged already before response production, and (3) had specific regional topographies at posterior sensorimotor and anterior (premotor and medial frontal) areas. Specifically, the connectedness of motor and sensorimotor areas contra-lateral to the response supported by delta networks was substantially reduced during errors. Also, there was an error-related suppression of the phase stability of delta and theta oscillations at these areas. This synchronization reduction was accompanied by increased temporal synchronization of motor theta oscillations at bi-lateral premotor regions and by two distinctive error-related effects at medial frontal regions: (1) a focused fronto-central enhancement of theta power and (2) a separable enhancement of the temporal synchronization of delta oscillations with a localized medial frontal focus. Together, these observations indicate that the electrophysiological signatures of performance errors are not limited to the medial frontal signals, but they also involve the dynamics of oscillatory motor networks at extended cortical regions generating the movement. Also, they provide a more detailed picture of the medial frontal processes activated in relation to error processing.
Asunto(s)
Electroencefalografía , Corteza Motora , Humanos , Encéfalo , Corteza Motora/fisiología , Potenciales Evocados , Movimiento , Ritmo Teta/fisiologíaRESUMEN
It has been suggested that a distributed oscillatory system in the brain operating in the theta (3.5-7 Hz) frequency range plays a major role in coordinating motor actions. The major objective of the present study was to explore the effects of human aging on the neurodynamics of motor-related EEG theta activity during correct motor response generation. Response-related potentials of young and older adults elicited in auditory and visual four-choice sensorimotor tasks were analyzed in the time-frequency domain. The phase-locking factor and total power were computed at motor cortical regions contra- and ipsilateral to the movement and at the midline to reflect phase synchronization and power of motor theta oscillations. Major results demonstrated that in both young and older adults, a pronounced response-locked theta activity (3.5-7 Hz) was generated at premotor, motor and sensorimotor cortical regions contra-lateral to the responding hand. Aging was associated with a decreased lateral asymmetry in the phase synchronization of only the left-hand responses. Also, there was a strong aging-related suppression of theta power at the medial fronto-central region that was specifically enhanced and correlated with response speed only in young adults. These results confirm the involvement of theta oscillations in movement generation in relation to action coordination in humans. Also, they show that aging is associated with a dysfunction of the oscillatory theta system for motor action regulation due to a strong suppression of a medial frontal integrating mechanism and an impaired balance in the functional control of responses with the right and the left hand.