Biomedical subjects

J M Tormos

Publications and source records attributed to J M Tormos.

17 recordsLinked to original sources

PubMed2006

Neuropsychological profile of persons with anoxic brain injury: differences regarding physiopathological mechanism.

PRIMARY OBJECTIVE: To determine the neuropsychological profile of persons with anoxic brain injury. METHODS AND PROCEDURES: A retrospective study on a population of persons with anoxic brain injury admitted to a Brain Injury Unit (Institut Guttmann, Spain) from 1995-2003. The sample was divided according to physiopathological mechanisms in two sub-groups: ischemic anoxia (21 cases) and hypoxemic anoxia (11 cases). Functions assessed included orientation, attention, language, visuo-perceptive and visuo-constructive processing and verbal memory. RESULTS: Neuropsychological assessment showed diffuse cognitive impairment in all assessed functions. Episodes of ischemic anoxia caused more severe verbal memory and learning problems than episodes of hypoxemic anoxia. CONCLUSIONS: This study shows that memory problems are the most prominent and relevant impairment, although all other cognitive functions are also impaired, affecting both memory itself and general behaviour. Statistical analysis also provides preliminary evidence on the different profile of memory impairment whether cerebral anoxia had hypoxic or ischemic origin.

Adult↗

PubMed2002

Mapping of the human visual cortex using image-guided transcranial magnetic stimulation.

We describe a protocol using transcranial magnetic stimulation (TMS) to systematically map the visual sensations induced by focal and non-invasive stimulation of the human occipital cortex. TMS is applied with a figure of eight coil to 28 positions arranged in a 2x2-cm grid over the occipital area. A digitizing tablet connected to a PC computer running customized software, and audio and video recording are used for detailed and accurate data collection and analysis of evoked phosphenes. A frameless image-guided neuronavigational device is used to describe the position of the actual sites of the stimulation coils relative to the cortical surface. Our results show that TMS is able to elicit phosphenes in almost all sighted subjects and in a proportion of blind subjects. Evoked phosphenes are topographically organized. Despite minor inter-individual variations, the mapping results are reproducible and show good congruence among different subjects. This procedure has potential to improve our understanding of physiologic organization and plastic changes in the human visual system and to establish the degree of remaining functional visual cortex in blind subjects. Such a non-invasive method is critical for selection of suitable subjects for a cortical visual prosthesis.

Blindness↗

PubMed2001

Transcranial magnetic stimulation in young persons: a review of known cases.

There are no published data about transcranial magnetic stimulation (TMS) as a treatment for psychiatric disorders in young persons. The aim of this article is to collate available information about TMS in this population. Information was sought, by placing a message on the TMS Listserver, from investigators who had used TMS in patients 18 years of age or younger. Only one group reported experience in this area; it had treated seven patients, ages 16-18 years. Three patients had unipolar depression, three had schizophrenia, and one had bipolar disorder. Five of the seven patients had improved by the conclusion of the TMS course. Adverse events were reported in one patient. Further studies are needed first to investigate systematically the safety of TMS in children and adolescents and second to examine its potential therapeutic effects in this population.

Adolescent↗

PubMed2001

The role of the dorsolateral prefrontal cortex during sequence learning is specific for spatial information.

Many studies have implicated the dorsolateral prefrontal cortex in the acquisition of skill, including procedural sequence learning. However, the specific role it performs in sequence learning has remained uncertain. This type of skill has been intensively studied using the serial reaction time task. We used three versions of this task: a standard task where the position of the stimulus cued the response; a non-standard task where the color of the stimulus was related to the correct response; and a combined task where both the color and position simultaneously cued the response. We refer to each of these tasks based upon the cues available for guiding learning as position, color and combined tasks. The combined task usually shows an enhancement of skill acquisition, a result of being driven by two simultaneous and congruent cues. Prior to the performance of each of these tasks the function of the dorsolateral prefrontal cortex was disrupted using repetitive transcranial magnetic stimulation. This completely prevented learning within the position task, while sequence learning occurred to a similar extent in both the color and combined tasks. So, following prefrontal stimulation the expected learning enhancement in the combined task was lost, consistent with only a color cue being available to guide sequence learning in the combined task. Neither of these effects was observed following stimulation at the parietal cortex. Hence the critical role played by the dorsolateral prefrontal cortex in sequence learning is related exclusively to spatial cues. We suggest that the dorsolateral prefrontal cortex operates over the short term to retain and manipulate spatial information to allow cortical and subcortical structures to learn a predictable sequence of actions. Such functions may emerge from the broader role the dorsolateral prefrontal cortex has in spatial working memory. These results argue against the dorsolateral prefrontal cortex constituting part of the neuronal substrate responsible for general aspects of implicit or explicit sequence learning.

Adult↗

PubMed2001

Prefrontal repetitive transcranial magnetic stimulation as add on treatment in depression.

A growing number of studies report antidepressant effects of repetitive transcranial magnetic stimulation (rTMS) in patients with major depression. The hypothesis that high frequency (20 Hz) rTMS (HF-rTMS) may speed up and strengthen the therapeutic response to sertraline in MD was tested. Twenty eight patients who had not yet received medication for the present depressive episode (n=12) or had failed a single trial of an antidepressant medication (n=16) were started on sertraline and randomised to receive either real of sham HF-rTMS. HF-rTMS was applied to the left dorsolateral prefrontal area in daily sessions (30 trains of 2 s, 20-40 s intertrain interval, at 90% motor threshold) on 10 consecutive working days. The results suggest that in this patient population, HF-rTMS does not add efficacy over the use of standard antidepressant medication.

Adult↗

PubMed2000

Interindividual variability of the modulatory effects of repetitive transcranial magnetic stimulation on cortical excitability.

Repetitive transcranial magnetic stimulation (rTMS) appears to have effects on cortical excitability that extend beyond the train of rTMS itself. These effects may be inhibitory or facilitatory and appear to depend on the frequency, intensity, duration and intertrain interval of the rTMS. Many studies assume facilitatory effects of high-frequency rTMS and inhibitory effects of low-frequency rTMS. Nevertheless, the interindividual variability of this modulation of cortical excitability by rTMS has not been systematically investigated. In this study, we applied 240 pulses of rTMS at 90% of the subjects' motor threshold to their motor cortex at different frequencies (1, 10, 15 and 20 Hz) and examined the effects on motor evoked potentials (frequency tuning curve). Although the averaged group data showed a frequency-dependent increase in cortical excitability, each subject had a different pattern of frequency tuning curve, i.e. a different modulatory effect on cortical excitability at different rTMS frequencies. The interindividual variability of these modulatory effects was still high, though less so, when the number of rTMS pulses was increased to 1,600. These findings illustrate the degree of variability of the rTMS effects in the human brain.

Cerebral Cortex↗

PubMed2000

Modulation of corticospinal excitability by repetitive transcranial magnetic stimulation.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) is able to modulate the corticospinal excitability and the effects appear to last beyond the duration of the rTMS itself. Different studies, employing different rTMS parameters, report different modulation of corticospinal excitability ranging from inhibition to facilitation. Intraindividual variability of these effects and their reproducibility are unclear. METHODS: We examined the modulatory effects of rTMS to the motor cortex at various frequencies (1, 10, 20 Hz) and at different time-points in twenty healthy volunteers. RESULTS: We observed significant inhibition of MEPs following 1 Hz rTMS and significant facilitation of MEPs following 20 Hz rTMS for both day1 and day 2. Interestingly, at 1 Hz and 20 Hz rTMS, the modulatory effect produced by rTMS was greater on day 2. However, there was no significant change in corticospinal excitability following 10 Hz rTMS neither on day 1 nor day 2. CONCLUSION: Our findings raise questions as to how stimulation parameters should be determined when conducting studies applying rTMS on multiple days, and in particular, studies exploring rTMS as a treatment modality in neuropsychiatric disorders.

Adult↗

PubMed1999

Transcranial magnetic stimulation and neuroplasticity.

We review past results and present novel data to illustrate different ways in which TMS can be used to study neural plasticity. Procedural learning during the serial reaction time task (SRTT) is used as a model of neural plasticity to illustrate the applications of TMS. These different applications of TMS represent principles of use that we believe are applicable to studies of cognitive neuroscience in general and exemplify the great potential of TMS in the study of brain and behavior. We review the use of TMS for (1) cortical output mapping using focal, single-pulse TMS; (2) identification of the mechanisms underlying neuroplasticity using paired-pulse TMS techniques; (3) enhancement of the information of other neuroimaging techniques by transient disruption of cortical function using repetitive TMS; and finally (4) modulation of cortical function with repetitive TMS to influence behavior and guide plasticity.

Electromagnetic Phenomena↗

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

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

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

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↗

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↗

PubMedDate not supplied

Melatonin levels in Parkinson's disease: drug therapy versus electrical stimulation of the internal globus pallidus.

The objective of our work was to measure plasma melatonin levels in patients with Parkinson's Disease (PD) following electrical stimulation of the internal globus pallidus (GPi), and to compare these levels with groups of PD patients under drug therapy and healthy controls. The levels of melatonin were measured twice daily at 1000 and 1200. The GPi stimulation at 130 Hz lowered melatonin levels, while no changes were observed in the absence of stimulation. The melatonin levels from healthy subjects were lower than those observed in PD patients. The melatonin levels from PD patients under drug therapy were also measured during the night (2000-2400-0400) and at 0800 in order to observe their circadian changes. The Internal Globus Pallidus (GPi) stimulation was effective in lowering the melatonin levels during the day and, therefore returned these levels to those observed in normal subjects.

Antiparkinson Agents↗

PubMedDate not supplied

[Transcranial magnetic stimulation].

INTRODUCTION: Transcranial magnetic stimulation (TMS) permits stimulation of the cerebral cortex in humans without requiring open access to the brain and is one of the newest tools available in neuroscience. There are two main types of application: single-pulse TMS and repetitive TMS. DEVELOPMENT: The magnetic stimulator is composed of a series of capacitors that store the voltage necessary to generate a stimulus of the sufficient intensity of generate an electric field in the stimulation coil. The safety of TMS is supported by the considerable experience derived from studies involving electrical stimulation of the cortex in animals and humans, and also specific studies on the safety of TMS in humans. CONCLUSIONS: In this article we review historical and technical aspects of TMS, describe its adverse effects and how to avoid them, summarize the applications of TMS in the investigation of different cerebral functions, and discuss the possibility of using TMS for the treatment of neuropsychiatric disorders.

Cerebral Cortex↗

PubMedDate not supplied

[The application of transcranial magnetic stimulation in neuropsychological investigation].

OBJECTIVE: In this review we describe the main studies in which transcranial magnetic stimulation (TMS) has been used in the study of superior cognitive function. DEVELOPMENT: The various studies published in the literature show that TMS can modulate neuropsychological processes such as attention, different types of memory such as working memory, declarative memory, memory of procedures and language. In most cases TMS acts on the different cognitive abilities blocking or making them difficult. Thus TMS may be used as a method of causing transient lesions bringing the relationship brain-conduct to a dimension of cause and avoiding certain limitations of the classical method for creating lesions. The positive effects of TMS in certain tasks involving language and memory has also been shown. The latter offer new possibilities of future application in cognitive rehabilitation. CONCLUSIONS: TMS has an obvious effect on neuropsychological functions. Over the past ten years studies in this field have increased progressively. At the present time the results obtained by using TMS in cognitive neuroscience are of a basic type, limited to experimental laboratory work. It has mainly been used on normal persons. However, it cannot be long before it is used clinically in neuropsychological patients.

Attention↗

PubMedDate not supplied

[Transcranial magnetic stimulation: contribution to psychiatry and to the study of brain-behavior relationship].

Transcranial Magnetic Stimulation (TMS) is a safe noninvasive technique to modulate cortical excitability. The introduction of repetitive TMS (rTMS) provides a new tool for studying psychopathologic disorders and higher cognitive functions. One of the most salient potential effects of rTMS is its possible therapeutic effect on different psychiatric disorders like depression, mania, obsessive compulsive disorder, post-traumatic stress disorder and schizophrenia. The mechanisms by which exerts its therapeutic effects are still unknown. However, the combination of this new methodology with functional neuroimaging techniques may help clarify what cerebral dysfunctions underly certain psychiatric conditions at the same time that it provides novel insights into brain cortico-cortical and cortico-subcortical connectivity.

Brain↗