Weak cathodal transcranial direct current stimulation (tDCS) of the human hand area modulates corticospinal excitability with a suppression of motor-evoked potentials (MEPs) evoked by transcranial ...magnetic stimulation (TMS). The changes in excitability persist beyond the time of stimulation if tDCS is given for several minutes and can remain stable for an hour or more. The aim of present study was to evaluate whether a long-lasting suppression of cortical excitability could be induced by prolonged cathodal tDCS (20 min of stimulation). We also explored the impact of brain-derived neurotrophic factor (BDNF) gene polymorphisms, on tDCS after-effects. Cortical excitability to single and paired-pulse TMS was evaluated both for the stimulated and contralateral hemisphere, before and up to 24 h after 20 min of cathodal tDCS. We evaluated threshold and amplitude of MEPs, short interval intracortical inhibition (SICI), and intracortical facilitation (ICF). tDCS produced a pronounced suppression of MEP amplitude that was still significant at 3 h after the end of stimulation. The BDNF genotype had not influence on tDCS after-effects. Thresholds for MEPs, SICI and ICF were not affected. No significant effect was observed in the contralateral hemisphere. Twenty minutes of cathodal tDCS is capable of inducing a long-lasting suppression of the excitability of the human motor cortex.
1 Institute of Neurology, Università Cattolica, Rome, Italy; 2 Unidad de Neurologia Funcional, Hospital Nacional de Paraplejicos, Finca la Peraleda, Toledo, Spain; 3 Neurochirurgia CTO, and 4 ...Neurofisiologia CTO, and 5 Fondazione Don C Gnocchi, Rome, Italy; and 6 Sobell Department of Neurophysiology, Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
Submitted 6 April 2006;
accepted in final form 22 May 2006
A magnetic transcranial conditioning stimulus given over the motor cortex at intensities below active threshold for obtaining motor-evoked potentials (MEPs) facilitates EMG responses evoked at rest in hand muscles by a suprathreshold magnetic stimulus given 1025 ms later. This is known as intracortical facilitation (ICF). We recorded descending volleys produced by single and paired magnetic motor cortex stimulation through high cervical epidural electrodes implanted for pain relief in six conscious patients. At interstimulus intervals (ISIs) of 10 and 15 ms, although MEP was facilitated, there was no change in the amplitude or number of descending volleys. An additional I wave sometimes was observed at 25 ms ISI. In one subject, we also evaluated the effects of reversing the direction of the induced current in the brain. At 10 ms ISI, the facilitation of the MEPs disappeared and was replaced by slight suppression; at 2 ms ISI, there was a pronounced facilitation of epidural volleys. Subsequent experiments on healthy subjects showed that a conditioning stimulus capable of producing ICF of MEPs had no effect on the EMG response evoked by transmastoidal electrical stimulation of corticospinal tract. We conclude that ICF occurs because either 1 ) the conditioning stimulus has a (thus far undetected) effect on spinal cord excitability that increases its response to the same amplitude test volley or 2 ) that it can alter the composition (but not the amplitude) of the descending volleys set up by the test stimulus such that a larger proportion of the activity is destined for the target muscle.
Address for reprint requests and other correspondence: V. Di Lazzaro, Inst. of Neurology, Univ. Cattolica, L.go A. Gemelli 8, 00168 Rome, Italy (E-mail: vdilazzaro{at}rm.unicatt.it )
Abstract Objective Changes in cerebral cortex excitability have been demonstrated after a stroke and are considered relevant for recovery. Repetitive transcranial magnetic stimulation (rTMS) of the ...brain can modulate cerebral cortex excitability and, when rTMS is given as theta burst stimulation (TBS), LTP- or LTD-like changes can be induced. The aim of present study was to evaluate the effects of TBS on cortical excitability in acute stroke. Methods In 12 acute stroke patients, we explored the effects of facilitatory TBS of the affected hemisphere and of inhibitory TBS of the unaffected hemisphere on cortical excitability to single-pulse transcranial magnetic stimulation (TMS) on both sides. The effects produced by TBS in patients were compared with those observed in a control group of age-matched healthy individuals. Results In patients, both the facilitatory TBS of the affected motor cortex and the inhibitory TBS of the unaffected motor cortex produced a significant increase of the amplitude of MEPs evoked by stimulation of the affected hemisphere. The effects observed in patients were comparable to those observed in controls. Conclusions Facilitatory TBS over the stroke hemisphere and inhibitory TBS over the intact hemisphere in acute phase enhance the excitability of the lesioned motor cortex. Significance TBS might be useful to promote cortical plasticity in stroke patients.
The purpose of this study was to evaluate a STIR sequence with an optimized inversion pulse that entails use of increased receiver bandwidth for metal artifact reduction.
Image distortion, artifacts, ...insufficient fat suppression, and detection of relevant findings improved with the STIR optimized inversion pulse, which was associated with significant artifact reduction.
Previous studies have shown that paired associative stimulation (PAS) protocol, in which peripheral nerve stimuli are followed by transcranial magnetic stimulation (TMS) of the motor cortex at ...intervals that produce an approximately synchronous activation of cortical networks, enhances the amplitude of motor evoked potentials (MEPs) evoked by cortical stimulation. Indirect data support the hypothesis that the enhancement of MEPs produced by PAS involves long-term potentiation like changes in cortical synapses. The aim of present paper was to investigate the central nervous system level at which PAS produces its effects. We recorded corticospinal descending volleys evoked by single pulse TMS of the motor cortex before and after PAS in 4 conscious subjects who had an electrode implanted in the cervical epidural space for the control of pain. The descending volleys evoked by TMS represent postsynaptic activity of corticospinal neurones that can provide indirect information about the effectiveness of synaptic inputs to these neurones. PAS significantly enhanced the amplitude of later descending waves, whereas the earliest descending wave was not significantly modified by PAS. The present results show that PAS may increase the amplitude of later corticospinal volleys, consistent with a cortical origin of the effect of PAS.
Previous studies have shown that low-frequency repetitive transcranial magnetic stimulation (rTMS) suppresses motor-evoked
potentials (MEPs) evoked by single pulse TMS. The aim of the present paper ...was to investigate the central nervous system level
at which rTMS produces a suppression of MEP amplitude. We recorded corticospinal volleys evoked by single pulse TMS of the
motor cortex before and after 1 Hz rTMS in five conscious subjects who had an electrode implanted in the cervical epidural
space for the control of pain. One of the patients had Parkinson's disease and was studied on medication. Repetitive TMS significantly
suppressed the amplitude of later I-waves, and reduced the amplitude of concomitantly recorded MEPs. The earliest I-wave was
not significantly modified by rTMS. The present results show that 1 Hz rTMS may decrease the amplitude of later descending
waves, consistent with a cortical origin of the effect of 1 Hz rTMS on MEPs.
Abstract Objective Central cholinergic circuits of human brain can be tested non-invasively by coupling peripheral nerve stimulation with transcranial magnetic stimulation of motor cortex. This test, ...named short latency afferent inhibition (SAI) has been shown in healthy subjects to be sensitive to the blockage of muscarinic acetylcholine receptors and it is impaired in Alzheimer disease (AD) patients, a cholinergic form of dementia, while it is normal in non-cholinergic forms of dementia such as fronto-temporal dementia. The objective of present study was to evaluate central cholinergic circuits in patients with Vascular Dementia (VaD). Methods We evaluated SAI in a group of patients with VaD and compared the data with those from a group of AD patients and a control group of age-matched healthy individuals. Results Mean SAI was normal in VaD patients while it was significantly reduced in AD patients. The analysis of individual data showed abnormal SAI in 75% of AD and in only 25% of VaD. Conclusions SAI is normal in most of VaD patients in contrast with AD patients. This test might be used for the functional evaluation of central cholinergic circuits in VaD patients. Significance SAI testing may represent a useful additional tool for the evaluation of patients with VaD however, further studies are required in order to evaluate whether this method can be used for the differential diagnosis between pure VaD and different forms of dementia.
Paired associative stimulation (PAS), in which peripheral nerve stimuli are followed by transcranial magnetic stimulation (TMS) of the motor cortex, may produce a long lasting change in cortical ...excitability. At an interstimulus interval slightly shorter than the time needed for the afferent inputs to reach cerebral cortex (10 ms), motor cortex excitability decreases. Indirect data support the hypothesis that PAS at this interval (PAS10) involves LTD like-changes in cortical synapses. The aim of present paper was to investigate more directly PAS10 effects. We recorded corticospinal descending volleys evoked by single pulse TMS before and after PAS10 in two conscious subjects who had a high cervical epidural electrode implanted for pain control. These synchronous volleys provide a measure of cortical synaptic activity. PAS10 significantly reduced the amplitude of later descending waves while the earliest descending wave was not modified. Present results confirm the cortical origin of the effect of PAS10.
Introduction For some adolescents surfing the web can turn into a psychological defense and to be in contrast with a healthy mental development. It happen if the internet surfing becomes a compulsive ...need (Drusian, 2005). Massive use of the internet can promote the development of behavioral addictions such as pathological gambling (Cantelmi, D’Andrea, 2000). Objectives and Aims The study investigates the correlation between social introversion, modality of the internet surfing and propensity to pathological gambling in a sample of Italian adolescents. Methods The research used a questionnaire divided into four areas: school performance, use of the internet, social introversion (SI scale of the MMPI-A); experiences of gambling (LIE/BET Questionnaire). 583 adolescents (45% males and 54% females, mean age 17 years) responded to the questionnaire. Results Adolescents with high social introversion (high scores on Si scale) are 7.4% of the sample. These teenagers use the Internet many hours per day. They state that surfing the internet is a way to drive away negative thoughts about their lives. They think that life would be boring without the internet. Many adolescents with social introversion have high scores to LIE/BET Questionnaire. The study does not show a correlation between school performance and the others variables (social introversion, use of internet and propensity to pathological gambling). Conclusions Social introversion seems to be a predictor of psychological disease such as internet addiction and pathological gambling.
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