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Phase-locked oscillatory approximately 15- to 30-Hz response to transient visual contrast stimulation: neuromagnetic evidence for cortical origin in humans.
No full textPlasma concentration and CNS effects of Ca antagonists darodipine and nimodipine after single-dose oral administration to healthy volunteers.
No full textInteraction between finger opposition movements and after effects of 1Hz-rTMS on ipsilateral motor cortex
No full textOne-hertz repetitive transcranial magnetic stimulation (1Hz-rTMS) over ipsilateral motor cortex is able to modify up to 30 min the motor performance of repetitive finger opposition movements paced with a metronome at 2 Hz. We investigated whether the long-lasting rTMS effect on motor behavior can be modulated by subsequent engagement of the contralateral sensorimotor system. Motor task was performed in different experimental conditions: immediately after rTMS, 30 min after rTMS, or when real rTMS was substituted with sham rTMS. Subjects performing the motor task immediately after rTMS showed modifications in motor behavior <= 30 min after rTMS. On the other hand, when real rTMS was substituted with sham stimulation or when subjects performed the motor task 30 min after the rTMS session, the effect was no longer present. These findings suggest that the combination of ipsilateral 1Hz-rTMS and voluntary movement is crucial to endure the effect of rTMS on the movement itself, probably acting on synaptic plasticity-like mechanism. This finding might provide some useful hints for neurorehabilitation protocols
1-Hz repetitive TMS over ipsilateral motor cortex influences the performance of sequential finger movements of different complexity
No full textTo elucidate the role of ipsilateral motor cortex (M1) in the control of unilateral finger movements (UFMs) in humans we used a conditioning protocol of 1-Hz repetitive transcranial magnetic stimulation (1-Hz rTMS) over M1 in 11 right-handed healthy subjects. We analysed the effects of conditioning rTMS on UFMs of different complexity (simple vs sequential finger movements), and performed with a different modality (internally vs externally paced movements). UFMs were monitored with a sensor-engineered glove, and a quantitative evaluation of the following parameters was performed: touch duration (TD); inter-tapping interval (ITI); timing error (TE); and number of errors (NE). 1-Hz rTMS over ipsilateral M1 was able to affect the performance of a sequence of finger opposition movements in a metronome-paced condition, significantly increasing TD and reducing ITI without TE changes. The effects on motor behaviour had a different magnitude as a function of the sequence complexity. Further, we found a different effect of the ipsilateral 1-Hz rTMS on externally paced movements with respect to an internally paced condition. All these findings indicate that ipsilateral M1 plays an important role in the execution of sequential UFMs. Interestingly, NE did not change in any experimental condition, suggesting that ipsilateral M1 influences only the temporal and not the spatial accuracy of UFMs. Finally, the duration (up to 30 min) of 1-Hz rTMS effects on ipsilateral M1 can indicate its direct action on the mechanisms of cortical plasticity, suggesting that rTMS can be used to modulate the communication between the two hemispheres in rehabilitative protocols
Narrow band (approximately 17-46 Hz) oscillatory response to pattern stimulation and the visual P300 of healthy subjects.
No full textFactor structure and ammonia-related modulation of the human retinal oscillatory potentials.
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Electroretinographic (ERG) assessment in Major Depressive Disorder (MDD) patients receiving duloxetine: might differences between responders and non-responders indicate a differential biological background?
No full textThe cerebellum predicts the temporal consequences of observed motor acts.
No full textIt is increasingly clear that we extract patterns of temporal regularity between events to optimize information processing. The ability to extract temporal patterns and regularity of events is referred as temporal expectation. Temporal expectation activates the same cerebral network usually engaged in action selection, comprising cerebellum. However, it is unclear whether the cerebellum is directly involved in temporal expectation, when timing information is processed to make predictions on the outcome of a motor act. Healthy volunteers received one session of either active (inhibitory, 1 Hz) or sham repetitive transcranial magnetic stimulation covering the right lateral cerebellum prior the execution of a temporal expectation task. Subjects were asked to predict the end of a visually perceived human body motion (right hand handwriting) and of an inanimate object motion (a moving circle reaching a target). Videos representing movements were shown in full; the actual tasks consisted of watching the same videos, but interrupted after a variable interval from its onset by a dark interval of variable duration. During the 'dark' interval, subjects were asked to indicate when the movement represented in the video reached its end by clicking on the spacebar of the keyboard. Performance on the timing task was analyzed measuring the absolute value of timing error, the coefficient of variability and the percentage of anticipation responses. The active group exhibited greater absolute timing error compared with the sham group only in the human body motion task. Our findings suggest that the cerebellum is engaged in cognitive and perceptual domains that are strictly connected to motor control
Time dynamics of stimulus- and event-related gamma band activity: contrast VEPs and the visual P300 in man
No full textObjectives: To investigate the time dynamics and phase relationship with the stimulus of the onset/offset visual evoked potentials (VEPs), P300 and gamma band oscillatory responses to visual (contrast) stimulation. Gamma band oscillatory activity mediates in sensory and cognitive operations, with a role in stimulus-related cortical synchronization, but is reportedly reduced in the time window of the P300 response.
Methods: Ten healthy volunteers were studied. VEPs and P300 were obtained in a stimulus condition combining standard contrast stimulation and a visual odd-ball paradigm. Visual stimuli were gratings with a sinusoidal luminance profile (9.0 degrees central retina; 1.3 cycles/degree; 70% contrast) that were presented monocularly in onset/offset mode, with vertical orientation (frequent stimulus; 80%) or with a 15 degrees rotation to the right (infrequent, target stimulus). The total signal activity (temporal spectral evolution), the activity phase-locked to the stimulus onset (rectified integrated average), and the 'locking index' (ratio of the activity phase-locked to the stimulus to the total signal activity) were computed over time and across frequencies on the signals recorded at occipital (visual responses) and central locations (P300).
Results: Oscillatory activity centered around approximately 20.0-35.0 Hz and phase-locked to the stimulus was recorded at occipital locations with time dynamics anticipating the conventional VEPs. Phase-locking was higher after frequent than in response to target stimuli and after the stimulus offset compared to onset, while the phase-locking of the VEP frequency components was higher after the stimulus onset. The low frequency components of the P300 recorded at Cz (below approximately 8.0-10.0 Hz) were almost totally phase-locked to the stimulus, while the gamma band activity at the P300 location did not vary over time in amplitude or phase-locking and was mostly non-locked to the target stimulus.
Conclusions: These observations add to the evidence of a role of the gamma band oscillatory responses (centered at approximately 20.0-35.0 Hz) in visual information processing and suggest that the increment in gamma band activity during cognitive operations also depends on task characteristics, vigilance or selective attention, and brain functional state. The visual P300 appears to reflect low frequency synchronization mechanisms
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