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Biomedical subjects

A Pascual-Leone

Publications and source records attributed to A Pascual-Leone.

At least 19 recordsLinked to original sources
PubMed1999

Low-frequency repetitive transcranial magnetic stimulation of the motor cortex in writer's cramp.

OBJECTIVE: To study the short-term effects of slow repetitive transcranial magnetic stimulation (rTMS) of the motor cortex on cortical excitability and handwriting in patients with writer's cramp. BACKGROUND: Cortical excitability of the primary motor cortex is abnormally enhanced in patients with writer's cramp. Therefore, reducing cortical excitability by low-frequency rTMS of the motor cortex might result in beneficial effects on handwriting in writer's cramp. DESIGN/METHODS: We studied the effects of subthreshold 1-Hz rTMS on motor threshold and cortico-cortical excitability using the paired-pulse technique in seven patients and seven controls. In another 16 patients and 11 age-matched controls we evaluated changes in cortical excitability by measuring the stimulus-response curve and the postexcitatory silent period before and after subthreshold 1-Hz rTMS. In addition, we analyzed the handwriting before and 20 minutes after 1-Hz rTMS. RESULTS: In the first experiment, low-frequency rTMS resulted in a normalization of the deficient cortico-cortical inhibition in the patients without affecting motor threshold. In the second experiment, 1-Hz rTMS resulted in a significant prolongation of the postexcitatory silent period without affecting the stimulus-response curve in the patient group. Moreover, the dystonic patients showed a significant reduction of mean writing pressure after subthreshold 1-Hz rTMS that was associated with clear but transient improvement in six patients. CONCLUSIONS: In some patients 1-Hz rTMS can reinforce deficient intracortical inhibition and may improve handwriting temporarily. Our data support the notion that reduced intracortical inhibition plays a part in the pathophysiology of focal dystonia.

Adult↗
PubMed1998

The effect of repetitive magnetic stimulation on localized musculoskeletal pain.

Current magnetic coil stimulators can efficiently activate neural structures without deep electrode placement and the local discomfort associated with transcutaneous electrical stimulation used in pain control. We tested the possibility of reducing pain in patients with localized musculoskeletal processes by applying repetitive magnetic stimulation on the tender body region. Thirty patients were randomized to receive 40 min of real or sham magnetic stimulation. After a single session, real magnetic stimulation significantly exceeded the sham effect: a 101-point pain score decreased by 59% in the treated group and 14% in sham-treated patients (z = -3.26, p = 0.001). The pain relief attained regularly persisted for several days. Results indicate that powerful magnetic coil stimulation can efficiently reduce pain originating from localized musculoskeletal injuries.

Adult↗
PubMed1998

Effect of focal cerebellar lesions on procedural learning in the serial reaction time task.

Prior studies have shown that procedural learning is severely impaired in patients with diffuse cerebellar damage (cortical degeneration) as measured by the serial reaction time task (SRTT). We hypothesize that focal cerebellar lesions can also have lateralized effects on procedural learning. Our objective was to assess the effects of focal cerebellar lesions in procedural learning as measured by the SRTT. We studied 14 patients with single, unilateral vascular lesions in the territory of the posterior-inferior or superior cerebellar artery, who were compared with ten age- and sex-matched controls in a one-handed version of the SRTT. Patients with lesions at any other level of the brain or posterior fossa were excluded by cranial magnetic resonance imaging. Our results show that patients do not acquire procedural knowledge when performing the task with the hand ipsilateral to the lesion, but show normal learning with the contralateral hand. No correlation was found with the side, size, or vascular territory of the lesion. We conclude that procedural learning is impaired in hemispheric cerebellar lesions and involves only the hand ipsilateral to the lesion, which suggests a critical role for the cerebellum and/or crossed cerebellar-prefrontal connections in this type of learning.

Adult↗
PubMed1998

Dynamic cortical involvement in implicit and explicit motor sequence learning. A PET study.

We examined the dynamic involvement of different brain regions in implicit and explicit motor sequence learning using PET. In a serial reaction time task, subjects pressed each of four buttons with a different finger of the right hand in response to a visually presented number. Test sessions consisted of 10 cycles of the same 10-item sequence. The effects of explicit and implicit learning were assessed separately using a different behavioural parameter for each type of learning: correct recall of the test sequence for explicit learning and improvement of reaction time before the successful recall of any component of the test sequence for implicit learning. Regional cerebral blood flow was measured repeatedly during the task, and a parametric analysis was performed to identify brain regions in which activity was significantly correlated with subjects' performances: i.e. with correct recall of the test sequence or with reaction time. Explicit learning, shown as a positive correlation with the correct recall of the sequence, was associated with increased activity in the posterior parietal cortex, precuneus and premotor cortex bilaterally, also in the supplementary motor area (SMA) predominantly in the left anterior part, left thalamus, and right dorsolateral prefrontal cortex. In contrast, the reaction time showed a different pattern of correlation during different learning phases. During the implicit learning phase, when the subjects were not aware of the sequence, improvement of the reaction time was associated with increased activity in the contralateral primary sensorimotor cortex (SM1). During the explicit learning phase, the reaction time was significantly correlated with activity in a part of the frontoparietal network. During the post-learning phase, when the subjects achieved all components of the sequence explicitly, the reaction time was correlated with the activity in the ipsilateral SM1 and posterior part of the SMA. These results show that different sets of cortical regions are dynamically involved in implicit and explicit motor sequence learning.

Adult↗
PubMed1998

Neural networks for Braille reading by the blind.

To explore the neural networks used for Braille reading, we measured regional cerebral blood flow with PET during tactile tasks performed both by Braille readers blinded early in life and by sighted subjects. Eight proficient Braille readers were studied during Braille reading with both right and left index fingers. Eight-character, non-contracted Braille-letter strings were used, and subjects were asked to discriminate between words and non-words. To compare the behaviour of the brain of the blind and the sighted directly, non-Braille tactile tasks were performed by six different blind subjects and 10 sighted control subjects using the right index finger. The tasks included a non-discrimination task and three discrimination tasks (angle, width and character). Irrespective of reading finger (right or left), Braille reading by the blind activated the inferior parietal lobule, primary visual cortex, superior occipital gyri, fusiform gyri, ventral premotor area, superior parietal lobule, cerebellum and primary sensorimotor area bilaterally, also the right dorsal premotor cortex, right middle occipital gyrus and right prefrontal area. During non-Braille discrimination tasks, in blind subjects, the ventral occipital regions, including the primary visual cortex and fusiform gyri bilaterally were activated while the secondary somatosensory area was deactivated. The reverse pattern was found in sighted subjects where the secondary somatosensory area was activated while the ventral occipital regions were suppressed. These findings suggest that the tactile processing pathways usually linked in the secondary somatosensory area are rerouted in blind subjects to the ventral occipital cortical regions originally reserved for visual shape discrimination.

Adult↗
PubMed1998

Study and modulation of human cortical excitability with transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) can be applied in different paradigms to obtain a measure of various aspects of cortical excitability. These different TMS paradigms provide information about different neurotransmitter systems, enhance our understanding about the pathophysiology of neuropsychiatric conditions, and in the future may be helpful as a guide for pharmacological interventions. In addition, repetitive TMS (rTMS) modulates cortical excitability beyond the duration of the rTMS trains themselves. Depending on rTMS parameters, a lasting inhibition or facilitation of cortical excitability can be induced. These effects can be demonstrated neurophysiologically or by combining rTMS with neuroimaging techniques. The effects do not remain limited to the cortical area directly targeted by rTMS, but affect a wider neural network transynaptically. Modulation of cortical excitability by rTMS may in the future be useful not only as a research tool but also as a therapeutic intervention in neurology, psychiatry, and neurorehabilitation.

Cerebral Cortex↗
PubMed1998

Linguistic processing during repetitive transcranial magnetic stimulation.

To determine if linguistic processing could be selectively disrupted with repetitive transcranial magnetic stimulation (rTMS), rTMS was performed during a picture-word verification task. Seven right-handed subjects were trained in two conditions: picture-word verification, which required the subject to verify whether the picture of an object matched the subtitle name on the same page, and frame verification, which required subjects to verify whether there was a rectangular frame around the combined object picture and subtitle. Half of the trials were performed during rTMS. The effects of rTMS on performance were evaluated at the following four scalp positions: left anterior (the area where rTMS produced speech arrest), a mirror site on the right, and two positions in the left and right parietal region. Stimulation over the left deltoid muscle served as a control. Subjects had less difficulty in making picture-word matching decisions during unstimulated compared with stimulated trials at the left anterior and posterior positions. No significant difference in accuracy was detected in the frame verification condition, but response times in the frame verification condition were longer with stimulation at the left anterior position. Because rTMS of the dominant hemisphere affected linguistic processing independent of speech motor output, we confirm that rTMS may be used to investigate language and other cognitive functions.

Adult↗
PubMed1998

Finger movements induced by transcranial magnetic stimulation change with hand posture, but not with coil position.

We attempted to map the representations of movements in 2 normal subjects by delivering five transcranial magnetic stimuli (TMS) with a focal coil to each of a grid of positions over the primary motor area (M1). Isometric forces were recorded from the contralateral index finger. Maps were made with the hand in a semiflexed "neutral" position, and with the thumb and index finger opposed in a "pincer" grip. The electromyogram (EMG) was monitored to ensure relaxation. The wrist was immobilized. In the neutral position, TMS at almost all positions produced abduction. Flexion was produced in the pincer position. Thus, while sensitive to changes in posture, TMS mapping may not be sensitive to the topographical organization of the M1 by movements as detected with direct cortical stimulation.

Adult↗
PubMed1997

Functional relevance of cross-modal plasticity in blind humans.

Functional imaging studies of people who were blind from an early age have revealed that their primary visual cortex can be activated by Braille reading and other tactile discrimination tasks. Other studies have also shown that visual cortical areas can be activated by somatosensory input in blind subjects but not those with sight. The significance of this cross-modal plasticity is unclear, however, as it is not known whether the visual cortex can process somatosensory information in a functionally relevant way. To address this issue, we used transcranial magnetic stimulation to disrupt the function of different cortical areas in people who were blind from an early age as they identified Braille or embossed Roman letters. Transient stimulation of the occipital (visual) cortex induced errors in both tasks and distorted the tactile perceptions of blind subjects. In contrast, occipital stimulation had no effect on tactile performance in normal-sighted subjects, whereas similar stimulation is known to disrupt their visual performance. We conclude that blindness from an early age can cause the visual cortex to be recruited to a role in somatosensory processing. We propose that this cross-modal plasticity may account in part for the superior tactile perceptual abilities of blind subjects.

Adult↗
PubMed1997

Lateralized effects of self-induced sadness and happiness on corticospinal excitability.

We studied the changes in excitability of the corticospinal projection evoked by self-induced sad and happy thoughts. Corticospinal excitability was probed using focal, single-pulse transcranial magnetic stimulation (TMS) applied to the optimal scalp position for evoking motor potentials in the contralateral first dorsal interosseus muscle. Fourteen right-handed subjects were studied while counting mentally, thinking sad thoughts, or thinking happy thoughts. In each of these three conditions TMS was applied in each subject randomly, 20 times to the right and 20 times to the left hemisphere. Sad thoughts resulted in a significant facilitation of the motor potentials evoked by left-hemispheric stimulation, while happy thoughts facilitated motor potentials evoked by right-hemispheric TMS, but decreased the amplitude of those evoked by left-hemispheric TMS. In two subjects an additional experiment using H-reflex measurements suggests that these changes are caused by changes in cortical rather than spinal excitability. These results further illustrate the lateralized control of mood in normal volunteers.

Adult↗
PubMed1997

Transcranial magnetic stimulation as therapy for depression and other disorders.

OBJECTIVE: To provide an overview of the progress and prospects of transcranial magnetic stimulation as a psychiatric therapy for depression. METHOD: Published and unpublished studies of the usefulness of transcranial magnetic stimulation as a therapy for depression were assessed, and characterised in terms of a consistent measure of dosage. Additional information was obtained through correspondence, personal meetings and visits to facilities. RESULTS: Transcranial magnetic stimulation, a means for inducing small regional currents in the brain, has been used in clinical neurology for some time, and can be used on conscious subjects with minimal side-effects. Early researchers noticed transient mood effects on people receiving this treatment, which prompted several inconclusive investigations of its effects on depressed patients. More recently, knowledge of functional abnormalities associated with depression has led to trials using repetitive transcranial magnetic stimulation to stimulate underactive left prefrontal regions, an approach which has produced short-term benefits for some subjects. The higher dosage delivered by high-frequency repetitive transcranial magnetic stimulation appears to produce greater benefits; scope exists for more conclusive studies based on extended treatment periods. CONCLUSIONS: Repetitive transcranial magnetic stimulation is a promising technology. The reviewed evidence indicates that it may be useful in the treatment of depression, and perhaps other disorders which are associated with regional hypometabolism. Should repetitive transcranial magnetic stimulation prove an effective, non-invasive, drug-free treatment for depression, a range of disorders could be similarly treatable.

Depressive Disorder↗
PubMed1996

Reorganization of human cortical motor output maps following traumatic forearm amputation.

We report the results of serial transcranial magnetic stimulation mapping of cortical motor outputs to the face and upper extremity in a subject studied before and repeatedly after traumatic amputation of the right arm immediately below the elbow. The results of the mapping studies illustrate the time course of plastic changes in the motor cortical representation in humans following a traumatic amputation and allow the correlation of subjective perceptions of phantom limbs with the reorganization of cortical outputs.

Accidents, Traffic↗
PubMed1996

Rapid-rate transcranial magnetic stimulation of left dorsolateral prefrontal cortex in drug-resistant depression.

BACKGROUND: Lesion and neuroimaging studies suggest that left prefrontal lobe dysfunction is pathophysiologically linked to depression. Rapid-rate transcranial magnetic stimulation (rTMS) to prefrontal structures has a lateralised effect on mood in normal volunteers, and several preliminary studies suggest a beneficial effect of rTMS on depression. However, adequately controlled studies have not been conducted. METHODS: We have studied the effects of focal rTMS on the depressive symptoms in 17 patients with medication-resistant depression of psychotic subtype. The study was designed as a multiple cross-over, randomised placebo-controlled trial. Sham rTMS and stimulation of different cortical areas were used as controls. FINDINGS: Left dorsolateral prefrontal cortex rTMS resulted in a significant decrease in scores on the Hamilton depression rating scale HDRS (from 25.2 to 13.8) and the self-rated Beck questionnaire BQ (from 47.9 to 25.7). 11 of the 17 patients showed pronounced improvement that lasted for about 2 weeks after 5 days of daily rTMS sessions. No patient experienced any significant undesirable side-effects. INTERPRETATION: Our findings emphasise the role of the left dorsolateral prefrontal cortex in depression, and suggest that rTMS of the left dorsolateral prefrontal cortex might become a safe, non-convulsive alternative to electroconvulsive treatment in depression.

Adult↗
PubMed1996

Activation of the primary visual cortex by Braille reading in blind subjects.

Primary visual cortex receives visual input from the eyes through the lateral geniculate nuclei, but is not known to receive input from other sensory modalities. Its level of activity, both at rest and during auditory or tactile tasks, is higher in blind subjects than in normal controls, suggesting that it can subserve nonvisual functions; however, a direct effect of non-visual tasks on activation has not been demonstrated. To determine whether the visual cortex receives input from the somatosensory system we used positron emission tomography (PET) to measure activation during tactile discrimination tasks in normal subjects and in Braille readers blinded in early life. Blind subjects showed activation of primary and secondary visual cortical areas during tactile tasks, whereas normal controls showed deactivation. A simple tactile stimulus that did not require discrimination produced no activation of visual areas in either group. Thus in blind subjects, cortical areas normally reserved for vision may be activated by other sensory modalities.

Blindness↗
PubMed1996

Locating the motor cortex on the MRI with transcranial magnetic stimulation and PET.

Transcranial magnetic stimulation with a focal coil was used to map the cortical representation of a hand muscle in four healthy subjects. In each subject, the three-dimensional locations of the magnetic stimulation positions and about 400 positions on the surface of the head were digitized. The amplitude-weighted center of gravity of each subject's map was found, and a line perpendicular to the local head surface was projected inward. The digitized heads were registered with the subjects' MRIs using the scalp contours. The coordinate transformations yielded by this process were used to map the stimulation positions and the perpendicular line into the MRIs. Brain areas imaged with positron emission tomography (PET) and 15O-labeled water, activated by movement of the same muscle, were registered with the MRIs using the brain contours. In all cases, the magnetic stimulation lines encountered the surface of the brain at the anterior lip of the central sulcus and ran along the precentral gyrus a few millimeters anterior to the central sulcus, coming within 5-22 mm of all the PET activation maxima. This technique demonstrates the accuracy of transcranial magnetic stimulation for locating the primary motor area.

Adult↗
PubMed1996

The role of the dorsolateral prefrontal cortex in implicit procedural learning.

We studied the role of the dorsolateral prefrontal cortex in procedural learning. Normal subjects completed several blocks of a serial reaction time task using only one hand without or with concurrent non-invasive repetitive transcranial magnetic stimulation. To disrupt their function transiently, stimulation was applied at low intensity over the supplementary motor area or over the dorsolateral prefrontal cortex contralateral or ipsilateral to the hand used for the test. Stimulation to the contralateral dorsolateral prefrontal cortex markedly impaired procedural implicit learning, as documented by the lack of significant change in response times during the task. Stimulation over the other areas did not interfere with learning. These results support the notion of a critical role of contralateral dorsolateral prefrontal structures in learning of motor sequences.

Adult↗
PubMed1996

Changes in mood and hormone levels after rapid-rate transcranial magnetic stimulation (rTMS) of the prefrontal cortex.

Rapid-rate transcranial magnetic stimulation (rTMS) was administered to 10 healthy volunteers on different days over the right or left prefrontal cortex, midfrontal cortex, occipital cortex, or cerebellum. Mood (self-rated), reaction time, and hormone levels were serially measured. Consistent with a previous study, comparison of hemispheres revealed significant associations with decreased happiness after left prefrontal rTMS and decreased sadness after right prefrontal rTMS. Stimulation of all three prefrontal regions, but not the occipital or cerebellar regions, was associated with increases in serum thyroid-stimulating hormone. There was no effect on serum prolactin. rTMS applied to prefrontal cortex is safe and well tolerated and produces regionally and laterally specific changes in mood and neuroendocrine measures in healthy adults. rTMS is a promising tool for investigating prefrontal cortex functions.

Adult↗