Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Field dependence/independence (FD/FI) is an important dimension of personality and cognitive styles. Different ability in mobilizing and/or allocating mental-attentional capacity was considered to be the most possible explanation for the FDI cognitive style. Many studies on characterizing the functional neuroanatomy of attentional control indicated the existence of a dissociable sub-process of conflict-monitoring and "cognitive control" system. ⋯ ERP was measured while the subjects performed the stimulus-matching tasks by categorizing two figures that were presented sequentially either as a match (same shape) or as a conflict (different shape) conditions. The results showed that the mean amplitude of N270 in FI group was higher relative to that in FD group at nearly all centrofrontal areas in the conflict condition. We conclude that the FDI cognitive styles could influence the conflict processing by the "cognitive control" system due to the different abilities of FD and FI subjects in mobilizing and/or allocating attentional resources, which can be indexed by N270.
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Transcranial magnetic stimulation has been used to study changes in central excitability associated with motor tasks. Recently, we reported that a finger flexion-extension task performed at a maximal voluntary rate (MVR) could not be sustained and that this was not due to muscle fatigue, but was more likely a breakdown in central motor control. To determine the central changes that accompany this type of movement task, we tracked motor-evoked potential (MEP) amplitude from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles of the dominant hand in normal subjects for 20 min after a 10 sec index finger flexion-extension task performed at MVR and at a moderate sustainable rate (MSR) and half the MSR (MSR(/2)). ⋯ Measurements of short-interval cortical inhibition revealed an increase in inhibition after all of the finger flexion-extension tasks, with the MSR task being associated with the greatest degree of inhibition. These findings indicate that a demanding MVR finger movement task is followed by a period of reduced corticomotor excitability and increased intracortical inhibition. However, these changes also occur with and are greater with slower rates of movement and are not specific for motor demand, but may be indicative of adaptive changes in the central motor pathway after a period of repetitive movement.
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To investigate the effects of homotopic and heterotopic conditioning pain modulation (CPM) on short-term cortical plasticity. Glutamate (tonic pain) or isotonic saline (sham) was injected in the upper trapezius (homotopic) and in the thenar (heterotopic) muscles. Intramuscular electrical stimulation was applied to the trapezius at pain threshold intensities, and somatosensory evoked potentials were recorded with 128 channel EEG. ⋯ A positive correlation at P300 between pain ratings to glutamate injection and the x coordinate during tonic pain (P = 0.016) was found for heterotopic CPM. Heterotopic CPM caused short-term cortical plasticity within the cingulate that was correlated to subjective pain ratings. The degree of long-term depressive effect to homotopic CPM was correlated to the change in location of the P200 dipole.