1,721,168 research outputs found
Transcranial Magnetic Stimulation and Cortical Evoked Potentials: a TMS/EEG co-registration study.
No full textObjective: In recent years, a promising tool has been introduced which allows the co-registration of electroencephalographic (EEG) activity
during brain transcranial magnetic stimulation (TMS). The aims of the present study are to identify eventual stimulus-related artefacts, and to
confirm and extend previous EEG/TMS findings about the possible networks generating EEG responses evoked by TMS.
Methods: Focal TMS was delivered to the left primary motor cortex (MI), with different coils (real and sham) and orientations (45 and 1358 in
respect to the sagittal plane), in six healthy subjects. EEG and motor evoked potentials (MEPs) were simultaneously recorded from 19 scalp
electrodes.
Results: TMS, with coil oriented at 458, induced EEG responses characterized by a sequence of positive deflections peaking at approximately
14, 30, 60 and 190 ms and negative deflections peaking at approximately 10, 18, 40 and 100 ms post-TMS. The negative components were
recorded at the recording electrode corresponding with the stimulation site (N10, N18), as well as at recording electrodes over the frontal
region of the contralateral, unstimulated, hemisphere (N40) and bilaterally over the central hemispheres with its maximal representation at
the stimulation site (N100). The positive components were instead detected at the frontal region of the right, unstimulated, hemisphere (P14),
over the central electrodes Cz, Fz and the frontal region of the right hemisphere (P30), at the stimulation site (P60), and over the frontal
regions of both hemispheres. When TMS was delivered with the coil oriented at 1358, no MEPs were recorded from the right target muscle.
Nonetheless, all the TMS-induced EEG components were still evoked apart from the N20–P30. Finally, TMS with the sham coil over left MI
did not induce either significant EEG responses or MEPs.
Conclusions: In conclusion, the TMS evoked components we have obtained by recording in continuous mode strikingly fit with those already
described by other authors for both their latencies and the spatio-temporal pattern of scalp distribution.
Significance: This experiment is a farther validation of the combined EEG/TMS recording technique as a promising tool for experimental and
clinical purposes
Transcranical Brain stimulation
No full textSince the discovery of transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES), these non-invasive brain stimulation (NIBS) techniques have been used to investigate the state of cortical excitability, and the excitability of the cortico-cortical and corticospinal pathways. In addition, these techniques have been found to induce neuroplasticity-a significant breakthrough in our understanding of the brain at work. Transcranial Brain Stimulation presents a wide range of possible brain stimulation applications and discusses what new information can be gained from using this technique on the dynamics of brain functions, hierarchical organization, and effective connectivity. Implications of recent findings related to the therapeutic application are discussed by an international group of leading experts, who present practical guidance on the use of each technique, and catalog the results of numerous TMS and tES studies on biological and behavioral effects
Platicity effects in visual perception learning: a transcranical electrical stimulation (tES) study
No full textModulation of cortical oscillatory activity during Transcranial Magnetic Stimulation.
No full textTranscranial magnetic stimulation (TMS) can transiently modulate cortical excitability, with a net effect depending on the stimulation frequency ( or =5 Hz facilitation, at least for the motor cortex). This possibility has generated interest in experiments aiming to improve deficits in clinical settings, as well as deficits in the cognitive domain. The aim of the present study was to investigate the on-line effects of low frequency (1 Hz) TMS on the EEG oscillatory activity in the healthy human brain, focusing particularly on the outcome of these modulatory effects in relation to the duration of the TMS stimulation. To this end, we used the event-related desynchronization/synchronization (ERD/ERS) approach to determine the patterns of oscillatory activity during two consecutive trains of sham and real TMS. Each train of stimulation was delivered to the left primary motor cortex (MI) of healthy subjects over a period of 10 min, while EEG rhythms were simultaneously recorded. Results indicated that TMS induced an increase in the power of brain rhythms that was related to the period of the stimulation, i.e. the synchronization of the alpha band increased with the duration of the stimulation, and this increase was inversely correlated with motor-evoked potentials (MEPs) amplitude. In conclusion, low frequency TMS over primary motor cortex induces a synchronization of the background oscillatory activity on the stimulated region. This induced modulation in brain oscillations seems to increase coherently with the duration of stimulation, suggesting that TMS effects may involve short-term modification of the neural circuitry sustaining MEPs characteristics
The role of prefrontal cortex in sentence comprehension: a rTMS study
No full textUsing repetitive transcranial magnetic stimulation (rTMS), we investigated the role of the
left and right dorsolateral prefrontal cortex (DLPFC) in sentence comprehension. Subjects
were required to judge which of the two pictures correctly matched the meaning of active
and passive semantically reversible sentences (subject–verb–object); the incorrect picture
did not match the sentence in term of lexical items (semantic task) or agent–patient structure
(syntactic task). The subjects performed the task while a series of magnetic stimuli
were applied to the left or right DLPFC. When rTMS was applied to the left DLPFC, the subjects’
performance was delayed only for the semantic task, while rTMS applied to the right
DLPFC slowed the processing of syntactic information. The results of this experiment provide
direct evidence of a double dissociation between the rTMS effects and the type of task,
which may reflect a differential hemispheric involvement of working memory resources
during sentence comprehension
Spontaneous and activity-dependent modulation of human motor cortex excitability to Transcranial Magnetic Stimulation: normative data in healthy subjects and possible applications in neuropsychiatric diseases
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Lateralized Contribution of Prefrontal Cortex in Controlling Task-Irrelevant Information during Verbal and Spatial Working Memory Tasks: rTMS Evidence
No full textThe functional organization of working memory (WM) in the human prefrontal cortex remains unclear. The present study used repetitive transcranial magnetic stimulation (rTMS) to clarify the role of the dorsolateral prefrontal cortex (dlPFC) both in the types of information (verbal vs. spatial), and the types of processes (maintenance vs. manipulation). Subjects performed three independent experiments (1-back and 2-back tasks) while rTMS was applied over dlPFC for 500 ms in the last period of the delay. In two experiments (1 and 2) physically identical stimuli (letters shown at different locations on a screen) under different domain conditions (letters or locations) were employed. Under these conditions, we discovered a double dissociation only in the 2-back task: during the letter condition, when applied to the right dlPFC, rTMS significantly delayed task performance, whereas, the same result was present during the location condition, but only when rTMS was applied to the left dlPFC. The other 2-back task (experiment 3), in which we had eliminated the task-irrelevant information (i.e. we used stimuli that varied only in one domain), did not show significant results. We propose that the functional dichotomy of the hemispheres may be due to mechanisms of cognitive control on interference, which resolve conflict through the inhibition of task-irrelevant information only during high WM load. In conclusion, these findings confirm the role of dlPFC in implementing top-down attentional control, and provide evidence for the theoretical suggestion that working memory serves to control selective attention in the normal human brain
The differential involvement of inferior parietal lobule in number comparison: a rTMS study.
No full textNumber processing is known to involve several sites within the posterior regions of parietal cortex. Here, we investigated whether neural
activity in the inferior parietal lobule (IPL) is essential for number processing, by observing the effects of interfering with its activity
during the execution of a standard number comparison task. Subjects performance on the task was significantly slowed down when we
delivered trains of repetitive transcranial magnetic stimuli (rTMS) to the posterior parietal scalp site overlying the left IPL, while rTMS
did not affect the number comparison task if delivered to homologous, contralateral (right) IPL. In conclusion, the present findings add
support to a growing body of evidence from neuropsychology and neuroimaging studies that the left inferior parietal lobule is an important
component of the networks subserving the representation of quantity
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