Prism adaptation in patients with unilateral lesion of the parietal or cerebellar cortex: A pilot study on two single cases using a concurrent exposure procedure

Neuroimaging studies showed that prism adaptation (PA), a widely used tool for the rehabilitation of neglect, involves a wide network of brain regions including the parietal cortex and the cerebellum. In particular, the parietal cortex has been suggested to mediate the initial stage of PA through conscious compensatory mechanisms as a reaction to the deviation induced by PA. The cerebellum, on the other side, intervenes in sensory errors prediction to update internal models in later stages. It has been suggested that two mechanisms may underlie PA effects: recalibration, a strategic cognitive process occurring in the initial stages of PA, and realignment, a fully automatic reorganization of spatial maps emerging later and more slowly in time. The parietal lobe has been proposed to be involved mainly in the recalibration whereas the realignment would be carried over by the cerebellum. Previous studies have investigated the effects of a lesion involving either the cerebellum or the parietal lobe in PA taking into account both realignment and recalibration processes. Conversely, no studies have compared the performance of a patient with a cerebellar lesion to that of a patient with a parietal lesion. In the present study, we used a recently developed technique for digital PA to test differences in visuomotor learning after a single session of PA in a patient with parietal and a patient with cerebellar lesions, respectively. The PA procedure, in this case, includes a digital pointing task based on a concurrent exposure technique, which allows patients to fully see their arm during the pointing task. This procedure has been shown to be as effective as the terminal exposure condition in neglect rehabilitation albeit different processes take place during concurrent exposure condition compared to the most used terminal exposure (allowing to see only the final part of the movement). Patients' performances were compared to that of a control group. A single session of PA was administered to 1) a patient (BC) with left parieto-occipital lesion involving SPL and IPL, 2) a patient (TGM) with a stroke in the territory sub-served by the SCA in the cerebellum, and 3) 14 healthy controls (HC). The task included three conditions: before wearing prismatic goggles (pre-exposure), while wearing prisms (exposure) and after removing the goggles (post-exposure). Mean deviations were calculated for the following phases: pre-exposure, early-exposure, late-exposure, post-exposure. The presence of after-effect was calculated as the difference between pre-exposure and post-exposure conditions. For each of these conditions, patients' performance was compared to that of the control group by using a modified Crawford t-test. We found that the patient with the parietal lesion had a significantly different performance in the late-exposure and in the post-exposure compared to both HC and the patient with the cerebellar lesion. Conversely, no differences were observed between TGM and HC across all the conditions. Our results show an increase in the magnitude of the adaptation during the late stage of PA in the patient with the parietal lesion whereas no differences in the performance between the cerebellar patient and the controls were found. These results confirm previous studies suggesting that the parietal cortex is an important node of a wider network involved in PA effect. Furthermore, results in the cerebellar patient suggest that visuomotor learning is not affected by lesions of the SCA territory when a concurrent exposure is used as, in such case, it less relies on sensory errors prediction to update internal models. Results are discussed considering the novelty of the applied PA technique.

Functional Role of Cerebellar Gamma Frequency in Motor Sequences Learning: a tACS Study

Although the role of the cerebellum in motor sequences learning is widely established, the specific function of its gamma oscillatory activity still remains unclear. In the present study, gamma (50 Hz)-or delta (1 Hz)-transcranial alternating current stimulation (tACS) was applied to the right cerebellar cortex while participants performed an implicit serial reaction time task (SRTT) with their right hand. The task required the execution of motor sequences simultaneously with the presentation of a series of visual stimuli. The same sequence was repeated across multiple task blocks (from blocks 2 to 5 and from blocks 7 to 8), whereas in other blocks, new/pseudorandom sequences were reproduced (blocks 1 and 6). Task performance was examined before and during tACS. To test possible after-effects of cerebellar tACS on the contralateral primary motor cortex (M1), corticospinal excitability was assessed by examining the amplitude of motor potentials (MEP) evoked by single-pulse transcranial magnetic stimulation (TMS). Compared with delta stimulation, gamma-tACS applied during the SRTT impaired participants' performance in blocks where the same motor sequence was repeated but not in blocks where the new pseudorandom sequences were presented. Noteworthy, the later assessed corticospinal excitability was not affected. These results suggest that cerebellar gamma oscillations mediate the implicit acquisition of motor sequences but do not affect task execution itself. Overall, this study provides evidence of a specific role of cerebellar gamma oscillatory activity in implicit motor learning.

Nutritional strategies for psoriasis: current scientific evidence in clinical trials

OBJECTIVE

Several nutritional strategies for the management of psoriasis are promising. Even if recent data support that nutrition may play a pivotal role in prevention and co-treatment and despite patient's concerns regarding the best nutritional habits, the consensus regarding the nutritional strategies to be adopted lacks in clinical settings. In this manuscript, the effects of several nutritional strategies for psoriasis patients such as hypocaloric diet, vitamin D, fish oil, selenium, and zinc supplementation were systematically reviewed. Randomized controlled trials (RCTs) on beneficial botanical oral supplements were also included in the analysis.

MATERIALS AND METHODS

For each topic, a search was conducted in MEDLINE electronic databases for articles published in English between January 1, 1990 and September 2018. Two independent reviewers assessed and extracted the data. Only controlled clinical trials were selected.

RESULTS

The evidence regarding the current nutritional strategies for psoriasis patients were summarized and translated into a global, comprehensible recommendation.

CONCLUSIONS

Weight loss combined with a healthy lifestyle was shown to be very beneficial for patients with moderate to severe disease with a significant reduction of the Psoriasis Area and Severity Index (PASI) score. Currently, oral vitamin D supplementation for prevention or treatment of psoriasis in adults with normal vitamin D levels is not recommended; however, psoriasis patients with a deficit in plasma vitamin D levels are advised to complement with oral supplements to prevent psoriasis-related comorbidities. Instead of zinc, selenium, and omega 3 supplements have been proven beneficial for psoriasis patients. Among botanical species, Dunaliella bardawil (D. bardawil), Tripterygium wilfordii (T. wilfordii), Azadirachta indica (A. indica), Curcuma longa (C. longa), and HESA-A are the most beneficial. In conclusion, a close cooperation between nutritionists and dermatologists may be useful for the management of psoriasis.

Cerebellar magnetic stimulation decreases levodopa-induced dyskinesias in Parkinson disease

BACKGROUND

The neural mechanisms and the circuitry involved in levodopa-induced dyskinesia (LID) are still partially obscure. LID can be considered the consequence of an abnormal pattern or code of activity that originates and is conveyed from the basal ganglia to the thalamus and the cortical motor areas. However, not only striatothalamocortical motor circuits but also other interconnected pathways could be implicated in its pathogenesis.

METHODS

In a series of experiments, we applied repetitive transcranial magnetic stimulation (rTMS) over the lateral cerebellum in a group of patients with advanced Parkinson disease, to investigate whether modulation of cerebellothalamocortical circuits by means of rTMS may result in a modification of a dyskinetic state induced by levodopa ingestion.

RESULTS

We found that a single session of cerebellar continuous theta burst stimulation (cTBS) was capable of transiently reducing LID. In the same patients, we observed that cerebellar cTBS changed the profile of activation of intracortical circuits in the contralateral primary motor cortex. Cerebellar cTBS reduced short intracortical inhibition and increased long intracortical inhibition, inducing a cortical reorganization that is associated with a reduction of LID. Furthermore, in another experiment, we observed that a 2-week course of bilateral cerebellar cTBS induced persistent clinical beneficial effects, reducing peak-dose LID for up to 4 weeks after the end of the daily stimulation period.

CONCLUSIONS

Our study demonstrates that cerebellar continuous theta burst stimulation has an antidyskinetic effect in Parkinson disease patients with levodopa-induced dyskinesia, possibly due to modulation of cerebellothalamocortical pathways.

The time course of idiom processing

Recent neuropsychological and neurophysiological studies have suggested that the neural correlates of idiom processing are predominantly located in the left Brodmann's area (BA) 22 and, to some extent, in the prefrontal cortex. The present study explores the temporal dynamics of left prefrontal and temporal cortex in idiom processing by using repetitive transcranial magnetic stimulation (rTMS) in normal subjects. Forty-five opaque highly familiar idioms and 45 literal sentences were used. Forty-three subjects completed 5 blocks of 18 trials (9 idioms, 9 literal sentences) corresponding to 4 stimulation conditions (left prefrontal, left temporal, vertex, no-stimulation baseline). Each subject was assigned to one of three groups, which differed in the timing of stimulation delivery. A selective impairment in accuracy for idioms was found when rTMS was applied to the prefrontal and temporal cortex 80ms after picture presentation, confirming the role of these regions in this task. Moreover, rTMS to the prefrontal cortex, but not to the temporal cortex, continued to affect the performance with idiomatic sentences at the later time of 120ms. The results seem to suggest that the prefrontal region is involved in both the retrieval of the figurative meaning from semantic memory and the monitoring of the response by inhibiting alternative interpretations when a picture-matching task is used.

High prevalence of secondary hyperparathyroidism due to hypovitaminosis D in hospitalized elderly with and without hip fracture

OBJECTIVES

To determine and compare the prevalence of secondary hyperparathyroidism (HPTH) in a population of community-dwelling and institutionalized older adults hospitalized with and without hip fracture, and to evaluate factors correlated with secondary HPTH in this population.

METHODS

Circulating concentrations of serum intact PTH, 25-hydroxyvitamin D [25(OH)D] total serum calcium and albumin were measured in 160 subjects with an osteoporotic fracture of the proximal femur and in 160 matched controls hospitalized for a disease unrelated to bone status. Patients with secondary causes of bone loss and taking medications affecting bone metabolism were excluded. Age, sex, place of residence and the ability to perform basic activities of daily living (BADL) two weeks before hospital admission were recorded at baseline.

RESULTS

Patients were comparable with regard to the baseline demographic, biochemical and functional characteristics. The overall prevalence of secondary hyperparathyroidism was 51.2%, without significant differences between hip fractured patients and controls (50.6 vs 51.9%, p=0.911). In bivariate analysis only the age and functional status (BADL) demonstrated a significant relationship with secondary HPTH, while sex and place of residence were not significant. These results were also confirmed in multivariate analysis. Particularly, the risk of secondary HPTH increased with age and with the number of functions lost in BADL: patients fully dependent showed a 3 times as high risk (odd ratio 3.07, 95% confidence interval 1.73 to 5.46, p=0.000) compared to patients independent in BADL, and subject aged >88 yr had a twice as high risk of developing secondary HPTH compared to younger ones (odd ratio 2.28, 95% confidence interval 1.20 to 4.32, p=0.012).

CONCLUSION

These results show that secondary HPTH due to hypovitaminosis D is a frequent disorder in hospitalized elderly, strongly correlated with the functional status, irrespective of sex and place of residence.

rTMS of supplementary motor area modulates therapy-induced dyskinesias in Parkinson disease

The neural mechanisms and circuitry involved in levodopa-induced dyskinesia are unclear. Using repetitive transcranial magnetic stimulation (rTMS) over the supplementary motor area (SMA) in a group of patients with advanced Parkinson disease, the authors investigated whether modulation of SMA excitability may result in a modification of a dyskinetic state induced by continuous apomorphine infusion. rTMS at 1 Hz was observed to markedly reduce drug-induced dyskinesias, whereas 5-Hz rTMS induced a slight but not significant increase.

IFN-γ Low Production Capacity in Type 1 Diabetes Mellitus Patients at Onset of Disease

In type 1 diabetes mellitus (T1DM), cytokines can be directly cytotoxic to beta-cells, and/or play an indirect role influencing some cells of the immune system. Since several factors could impair cytokine serum levels, the purpose of our study was to longitudinally evaluate intracellular cytokines, in T1DM patients, and in subject at risk, by flow cytometry analysis. At T1DM onset we observed significantly lower percentage of peripheral CD4 + and CD8 + cells producing IFN-gamma in patients compared to controls and subjects at risk. The 15-month follow-up patients showed significantly lower percentage of CD4 + and CD8 + cells producing IFN-gamma compared to the other groups. At 8-year follow-up no significant differences were observed among the groups in the percentage of cells producing cytokines. We could have considered "exhausted cells" or these T cell subsets may be migrated from peripheral blood to pancreas. On the other hand, our results are in agreement with those reported in literature: in animal model the absence of IFN-gamma production makes beta-cells highly susceptible to viral infection and subsequent attack by natural killer cells, which lead to hyperglycaemia and diabetes mellitus.

High-frequency rTMS improves time perception in Parkinson disease

Patients with Parkinson disease (PD) are impaired in time processing. The authors investigated the effects of high-frequency (5 Hz) repetitive transcranial magnetic stimulation (rTMS) in patients with PD performing a time reproduction task. The authors found significant improvement in time processing induced by rTMS when trains were applied over the right dorsolateral prefrontal cortex (DLPFC) but not over the supplementary motor area, suggesting that the circuit involving the basal ganglia and the DLPFC might constitute the neural network subserving time perception.

Overestimation of numerical distances in the left side of space

Normal subjects presented with a middle number and two left- and right-sided outer numbers overestimate the numerical distance between the middle number and that positioned at its left side. Repetitive transcranial magnetic stimulation (rTMS) of the right posterior parietal cortex specifically counteracts this bias, suggesting that the mental representation of space defined by numbers is shifted toward the left side depending on a greater activity of the right hemisphere.

Increased visual cortical excitability in ecstasy users: a transcranial magnetic stimulation study

OBJECTIVES

To test the presence of abnormalities of visual cortical excitability in people using ecstasy as a recreational drug.

METHODS

Ecstasy users and control subjects underwent single pulse transcranial magnetic stimulation (TMS) of the occipital cortex. The phosphene threshold was analysed and compared in the two groups.

RESULTS

Phosphene thresholds were significantly lower in ecstasy users compared with control subjects, and were correlated negatively with frequency of ecstasy use. Frequency of use was positively correlated with the presence of visual hallucinations. The phosphene threshold of subjects with hallucinations was significantly lower than that of subjects without hallucinations.

CONCLUSIONS

The use of ecstasy as a recreational drug is associated with an increased excitability of the visual cortex, possibly linked with massive serotonin release, followed by serotonin depletion, in this cortical area.

Influence of the supplementary motor area on primary motor cortex excitability during movements triggered by neutral or emotionally unpleasant visual cues

The stronger anatomo-functional connections of the supplementary motor area (SMA), as compared with premotor area (PM), with regions of the limbic system, suggest that SMA could play a role in the control of movements triggered by visual stimuli with emotional content. We addressed this issue by analysing the modifications of the excitability of the primary motor area (M1) in a group of seven healthy subjects, studied with transcranial magnetic stimulation (TMS), after conditioning TMS of SMA, during emotional and non-emotional visually cued movements. Conditioning TMS of the PM or of contralateral primary motor cortex (cM1) were tested as control conditions. Single-pulse TMS over the left M1 was randomly intermingled with paired TMS, in which a conditioning stimulation of the left SMA, left PM or right M1 preceded test stimulation over the left M1. The subjects carried out movements in response to computerised visual cues (neutral pictures and pictures with negative emotional content). The amplitudes of motor-evoked potentials (MEPs) recorded from the right first dorsal interosseous muscle after paired TMS were measured and compared with those obtained after single-pulse TMS of the left M1 under the various experimental conditions. Conditioning TMS of the SMA in the paired-pulse paradigm selectively enhanced MEP amplitudes in the visual-emotional triggered movement condition, compared with single-pulse TMS of M1 alone or with paired TMS during presentation of neutral visual cues. On the other hand, conditioning TMS of the PM or cM1 did not differentially influence MEP amplitudes under visual-emotional triggered movement conditions. This pattern of effects was related to the intensity of the conditioning TMS over the SMA, being most evident with intensities ranging from 110% to 80% of motor threshold. These results suggest that the SMA in humans could interface the limbic and the motor systems in the transformation of emotional experiences into motor actions.

1 Hz repetitive transcranial magnetic stimulation of the unaffected hemisphere ameliorates contralesional visuospatial neglect in humans

The aim of the study was to investigate whether low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected hemisphere can ameliorate visuospatial neglect. We treated three right brain damaged patients with left neglect. 900 pulses (1 Hz frequency) were given over left posterior parietal cortex every other day for 2 weeks. Patients performed a computerized task requiring length judgement of prebisected lines, tachistoscopically presented for 150 ms. With respect to rTMS the task was given 15 days before, at the beginning, at the end and 15 days after. At these times patients performed also line bisection and clock drawing tasks. rTMS induced a significant improvement of visuo-spatial performance that remained quite unchanged 15 days after. Patients performance at Time 3 and 4 improved also as concerns line bisection and clock drawing tasks.

Modulation of spinal cord excitability by subthreshold repetitive transcranial magnetic stimulation of the primary motor cortex in humans

Repetitive transcranial magnetic stimulation (rTMS) allows the modulation of intra-cortical excitability and may therefore affect the descending control of spinal excitability. We applied rTMS at subthreshold intensity and 1 Hz frequency for 10 min to the left primary motor cortex representation of the flexor carpi radialis muscle (FCR) in 10 subjects and assessed the H and M responses to median nerve stimulation before and after the rTMS. Following rTMS, H wave thresholds significantly reduced by approximately 20%. Maximal H but not M wave amplitude significantly increased over the baseline, so that H/M amplitude ratio was increased by 41%. Sham stimulation did not induce any noticeable change in M or H waves. Slow rTMS might facilitate monosynaptic spinal cord reflexes by inhibiting the cortico-spinal projections modulating spinal excitability.

Effect of IL-6 on IGF binding protein-3: a study in IL-6 transgenic mice and in patients with systemic juvenile idiopathic arthritis

Stunted growth is a common complication of childhood diseases characterized by chronic inflammation or infections. We previously demonstrated that NSE/hIL-6 transgenic mice, overexpressing the inflammatory cytokine IL-6 since early phase of life, showed a marked growth defect associated with decreased IGF-I levels, suggesting that IL-6 is one of the factors involved in stunted growth complicating chronic inflammation in childhood. Here we show that NSE/hIL-6 mice have normal liver IGF-I production, decreased levels of IGF binding protein-3 (IGFBP-3) and increased serum IGFBP-3 proteolysis. Reduced IGFBP-3 levels results in a marked decrease in the circulating 150-kDa ternary complex, even in the presence of normally functional acid labile subunit. Pharmacokinetic studies showed that NSE/hIL-6 mice have accelerated IGF-I clearance. Patients with systemic juvenile idiopathic arthritis (s-JIA), a chronic inflammatory disease characterized by prominent IL-6 production and complicated by stunted growth associated with low IGF-I levels, have markedly decreased IGFBP-3 levels, increased serum IGFBP-3 proteolysis and normal acid labile subunit levels. Our data show that chronic overproduction of IL-6 causes decreased IGFBP-3 levels, resulting in a decreased association of IGF-I in the 150-kDa complex. Decreased levels of IGF-I appear to be secondary to increased clearance.

rTMS of the unaffected hemisphere transiently reduces contralesional visuospatial hemineglect

To verify the role of interhemispheric influences on manifestations of neglect, the authors investigated the effects of a transient repetitive transcranial magnetic stimulation (rTMS)-induced disruption of the unaffected hemisphere on contralesional visuospatial neglect in two left- and five right-brain-damaged patients. Parietal rTMS of the unaffected hemisphere during the execution of a computerized task of bisected line's length judgment transiently decreased the magnitude of neglect as expressed in the number of errors.

Timing of right parietal and frontal cortex activity in visuo-spatial perception: a TMS study in normal individuals

In a recent study we showed that repetitive transcranial magnetic stimulation (rTMS) with train duration of 400 ms over right frontal and right posterior parietal cortices gives rise to transitory contralateral visuo-spatial neglect in normal subjects. In the present experiment we investigated whether using single-pulse TMS it is possible to obtain information about the timing of cortical activity related to spatial cognition. Nine healthy subjects performed in baseline condition and during TMS a tachistoscopic task, requiring a forced-choice estimation of the length of the two segments of prebisected horizontal lines. Single-pulse TMS was triggered at various time intervals (150 ms, 225 ms, 300 ms) after visual stimulus onset with a focal coil over P6 and F4 (according to 10/20 EEG system). Relative transitory rightward bias was observed only when parietal TMS was delivered 150 ms after visual stimulus presentation. Frontal stimulation induced no effect on visuo-spatial perception with the time intervals explored.

Effects of motor imagery on motor cortical output topography in Parkinson's disease

BACKGROUND

The motor impairment in Parkinson's disease (PD) could partly reflect a failure to activate processes of motor imagery.

OBJECTIVE

To verify any selective changes of motor output during motor imagery, lateralized to the hemisphere contralateral to the clinically affected side of hemiparkinsonian patients.

METHODS

Transcranial magnetic stimulation (TMS) was used to map the cortical representations of the contralateral abductor digiti minimi muscle (ADM) during rest, contraction, and motor imagery in a group of patients with hemi-PD and in a group of healthy volunteers. Seven patients with hemi-PD and seven healthy subjects were examined. Focal TMS was applied over a grid of 20 scalp positions on each hemiscalp. Maps were characterized by area (number of excitable positions), volume (the sum of motor evoked potential amplitudes at all scalp positions), and center of gravity (a map position representing an amplitude-weighted calculation of the excitable area).

RESULTS

In healthy control subjects, the area of cortical representation of ADM was symmetrically increased in both hemispheres by mental simulation of movement and real muscle contraction. In patients with hemi-PD, there was a hemispheric asymmetry in the area of cortical representation elicited by motor imagery. The area was reduced in the clinically affected hemisphere. The volume of cortical representation was increased under all conditions and in both hemispheres in patients with PD. However, largely because the volume was so high at rest in patients, the increment in volume associated with contraction was smaller than in control subjects.

CONCLUSION

This study demonstrates the presence of a tonic hyperactivation of motor cortical circuitry in PD in conjunction with an abnormality of either motor imagery or the process by which motor imagery engages the sensorimotor cortices in the clinically affected hemisphere.

Parieto-frontal interactions in visual-object and visual-spatial working memory: evidence from transcranial magnetic stimulation

This study aimed to investigate whether transcranial magnetic stimulation (TMS) can induce selective working memory (WM) deficits of visual-object versus visual-spatial information in normal humans. Thirty-five healthy subjects performed two computerized visual n-back tasks, in which they were required to memorize spatial locations or abstract patterns. In a first series of experiments, unilateral or bilateral TMS was delivered on posterior parietal and middle temporal regions of both hemispheres after various delays during the WM task. Bilateral temporal TMS increased reaction times (RTs) in the visual-object, whereas bilateral parietal TMS selectively increased RTs in the visual-spatial WM task. These effects were evident at a delay of 300 ms. Response accuracy was not affected by bilateral or unilateral TMS of either cortical region. In a second group of experiments, bilateral TMS was applied over the superior frontal gyrus (SFG) or the dorsolateral prefrontal cortex (DLPFC). TMS of the SFG selectively increased RTs in the visual-spatial WM task, whereas TMS of the DLPFC interfered with both WM tasks, in terms of both accuracy and RTs. These effects were evident when TMS was applied after a delay of 600 ms, but not one of 300 ms. These findings confirm the segregation of WM buffers for object and spatial information in the posterior cortical regions. In the frontal cortex, the DLPFC appears to be necessary for WM computations regardless of the stimulus material.

Modulation of intracortical inhibition induced by low- and high-frequency repetitive transcranial magnetic stimulation

We studied the changes of duration of subsequent silent periods (SPs) during repetitive magnetic stimulation (rTMS) trains of ten stimuli delivered at low (1 Hz) and high (7 Hz) frequencies. The effects at different intensities of stimulation (motor threshold, MT, 115% and 130% above the MT) were also evaluated. rTMS was performed in eight healthy subjects with a figure-of-eight coil placed over the hand motor area. The SP was recorded from abductor pollicis brevis (APB) muscle during a voluntary contraction of 30% of maximum effort. rTMS at 1-Hz frequency progressively decreased the duration of SP, whereas an alternating pattern of smaller and larger values was observed during trains at 7-Hz frequency and higher stimulus intensity. The findings show that rTMS changes the duration of cortical SPs; the effect is probably due to the modulation of intracortical inhibitory interneurons depending on the frequency and intensity of stimulation.

Patterns of cognitive impairment in secondary progressive stable phase of multiple sclerosis: correlations with MRI findings

Cognitive impairment is commonly described in multiple sclerosis (MS), but conflicting results have been reported about its pattern by previous studies focused on heterogeneous patient groups. The aim of this study was to investigate the cognitive skills of a homogeneous group of secondary progressive MS patients, and to examine the relationship of this impairment to MRI parameters. Forty-four MS patients underwent a series of neuropsychological tests devised to explore the main cognitive domains, and T1- and T2-weighted brain MRI. Results showed the presence of deficits of attention, memory, planning abilities, problem-solving and conceptual reasoning (frontal functions) in a subgroup of MS patients. Correlations between the performance in some 'frontal' tests and the extent of frontal lobe MRI lesional area were present, but rather unspecific, the same performance being also correlated with the nonfrontal lesional area. These findings suggest that in MS, overall macroscopic and microscopic brain damage is more important than the corresponding focal brain disease, even in determining deficits of selective cognitive domains.

DNase I mediates internucleosomal DNA degradation in human cells undergoing drug-induced apoptosis

Internucleosomal DNA fragmentation following the activation of endonucleases is the common end point of apoptosis. DNase I, a Ca(2+) / Mg(2+)-dependent endonuclease ubiquitously expressed in mammalian tissues, is believed to play a role in this process. To analyze the in vivo function of this enzyme in human cells, we have generated a cell line with targeted disruption of the DNase I gene, as well as several stable cell lines which overexpress the DNase I gene. Inactivation of the human DNase I gene was obtained in the Jurkat T cell clone JA3, characterized by high susceptibility to apoptotic cell death induced by pharmacological stimuli. JA3 cells, after disruption of the DNase I gene, became resistant to apoptotic stimuli. DNase I was overexpressed in the human cell lines JA3, K562 (erythroleukemia), M 14 (melanoma) and CEM (T cell lymphoma). Remarkably, stable overexpression of DNase I gene resulted in accelerated apoptosis in JA3 cells and induced apoptosis in K562, CEM and M14 cell lines, which are otherwise resistant to internucleosomal DNA degradation following pharmacological stimuli. Our study provides the first in vivo evidence that DNase I mediates internucleosomal DNA degradation in human cells undergoing drug-induced apoptosis.

Paired transcranial magnetic stimulation protocols reveal a pattern of inhibition and facilitation in the human parietal cortex

Intracortical inhibition (ICI) and facilitation (ICF) of the human motor cortex can be induced by paired transcranial magnetic stimulation (TMS). Although demonstrated in experimental animals, the existence of intracortical inhibitory and excitatory circuits in parietal sensory cortex has not been documented in humans. The aim of this study was to investigate the effects of paired TMS of the parietal cortex on contralateral tactile perception. Fifteen healthy subjects were involved in a task of discrimination of electrical stimuli delivered at near-threshold intensity of sensory perception over the left thumb. Paired TMS was delivered with a focal coil on the right posterior parietal lobe after various delays from the presentation of finger stimuli. The effects of different interstimulus intervals (ISI: 1, 3, 5, 7, 10 and 15 1 1 Bms1B) between the conditioning and the test TMS stimulus on tactile perception were studied. The conditioning stimulus intensity was set at 70 % of motor threshold, while test TMS intensity was 130 % of motor threshold. Single pulse suprathreshold TMS interfered with the perception of finger stimuli, while subthreshold stimuli such as the 'conditioning' stimuli had no effect on sensory perception. Paired TMS differentially influenced the performance depending on the ISI. At an ISI of 1 1 1 Bms1B, paired TMS stimuli induced a significant worsening of the performance compared with single pulse TMS; at an ISI of 5 1 1 Bms1B, paired TMS stimuli induced a significant facilitation of the performance compared with single pulse TMS, restoring baseline performance levels. These results suggest that paired TMS can reveal a selective pattern of ICI and ICF in the human parietal cortex.

Are autonomic signals influencing cortico-spinal motor excitability? A study with transcranial magnetic stimulation

In order to investigate the role of visceral afferent inputs flowing along autonomic fibers on corticospinal tract excitability, the variability of Motor Evoked Potentials (MEPs), elicited by Transcranial Magnetic Stimulation (TMS), was analysed during simultaneous monitoring of electrocardiogram (EKG) phases, breathing phases and sudomotor skin responses (SSRs) in a group of 10 healthy subjects. A cascade of at least 60 consecutive magnetic stimuli, with an interstimulus interval randomly varying between 20 and 40 s, was acquired. At the end of the recording session, the subject was asked to make at random five not consecutive self-paced forced inspirations. TMS was carried out at an intensity 10% above motor threshold excitability via a circular coil placed over the motor area of the right hemisphere. MEPs were recorded from the contralateral abductor digiti minimi muscle (ADM). Sudomotor Skin Responses (SSRs) were recorded on both hand palms. MEPs latency and amplitude did not show significant correlation with any of the EKG and respiratory phases. During forced inspiration, a significant latency shortening was found. TMS elicited SSRs, whose amplitudes were not correlated with MEP parameters. During forced inspiration a significant SSR amplitude increment, not correlated with MEP latency shortening, was also observed. These results assign a minor if any role to the considered autonomic parameters in modulating corticospinal motor excitability.

Time-dependent activation of parieto-frontal networks for directing attention to tactile space. A study with paired transcranial magnetic stimulation pulses in right-brain-damaged patients with extinction

Tactile extinction has been interpreted as an attentional disorder, closely related to hemineglect, due to hyperactivation of the unaffected hemisphere, resulting in an ipsilesional attentional bias. Paired transcranial magnetic stimulation (TMS) techniques, with a subthreshold conditioning stimulus (CS) followed at various interstimulus intervals (ISIs) by a suprathreshold test stimulus (TS), are useful for investigating intracortical inhibition and facilitation in the human motor cortex. In the present work, we investigated the effects of paired TMS over the posterior parietal and frontal cortex of the unaffected hemisphere in a group of eight right-brain-damaged patients with tactile extinction who were carrying out a bimanual tactile discrimination task. The aim of the study was to verify if paired TMS could induce selective inhibition or facilitation of the unaffected hemisphere depending on the ISI, resulting, respectively, in an improvement and a worsening of contralesional extinction. In addition, we wanted to investigate if the effects of parietal and frontal TMS on contralesional extinction appeared at different intervals, suggesting time-dependent activation in the cortical network for the processing of tactile spatial information. Paired TMS stimuli with a CS and a TS, separated by two ISIs of 1 and 10 ms, were applied over the left parietal and frontal cortex after various intervals from the presentation of bimanual cutaneous stimuli. Single-test parietal TMS stimuli improved the patients' performance, whereas paired TMS had distinct effects depending on the ISI: at ISI = 1 ms the improvement in extinction was greater than that induced by single-pulse TMS; at ISI = 10 ms we observed worsening of extinction, with complete reversal of the effects of single-pulse TMS. Compared with TMS delivered over the frontal cortex, parietal TMS improved the extinction rate in a time window that began earlier. These findings shed further light on the mechanism of tactile extinction, suggesting relative hyperexcitability of the parieto-frontal network in the unaffected hemisphere, which is amenable to study and modulation by paired TMS pulses. In addition, the results show time-dependent processing of tactile spatial information in the parietal and frontal cortices, with a bimodal distribution of activity, at least in the attentional network of the unaffected hemisphere.

Circulating levels of soluble E-selectin, P-selectin and intercellular adhesion molecule-1 in patients with juvenile idiopathic arthritis

OBJECTIVE

To measure circulating levels of soluble E-selectin (sE-selectin), sP-selectin, and soluble intercellular adhesion molecule-1 (sICAM-1) in patients with active juvenile idiopathic arthritides (JIA), and to evaluate their correlation with disease activity variables and cytokine levels.

METHODS

Serum levels of sE-selectin, sP-selectin, and sICAM-1 were measured by ELISA in 42 patients with JIA and in 15 healthy controls.

RESULTS

Circulating levels of sE-selectin and sICAM-1, but not sP-selectin, were significantly elevated in patients with active systemic JIA. In patients with active polyarticular or pauciarticular JIA serum levels of sE-selectin. sP-selectin, and sICAM-1 were comparable to those of controls. In patients with systemic JIA, levels of sE-selectin and sICAM-1 were significantly correlated with levels of soluble tumor necrosis factor receptor 2 (sTNFR2), but not with those of interleukin 6 (IL-6) or IL-1beta.

CONCLUSION

Patients with active systemic JIA have elevated circulating levels of sE-selectin and sICAM-1. The correlation with sTNFR2, together with previous data on the TNF system in systemic JIA. suggests that TNF activated endothelial cells are the source of sE-selectin and sICAM-1 in this disease.

Neurophysiological follow-up of motor cortical output in stroke patients

BACKGROUND AND PURPOSE

Transcranial magnetic stimulation (TMS) has been employed in following up a population of 20 stroke patients in a post-acute, apparently stabilized stage. Neurophysiological and clinical data were recorded in 5 different recording sessions, from the beginning of a neuro-rehabilitation treatment (T0, at about 5 weeks from the ictal event.), followed up for about 4 months (T4), with the purpose to study any modification of the cortical motor output in the course of a neuro-rehabilitation treatment.

METHODS

Motor evoked potentials (MEPs) were simultaneously recorded from 10 muscles of both upper limbs (affected and not-affected); meanwhile, clinical and functional scores were gathered. Spinal responsiveness was investigated via H-reflex and F-wave recordings.

RESULTS

We describe a pattern of improving changes still taking place four months after the stroke, even if the maximal amelioration burden was concentrated between T0 and T1 and T1 and T2 recording sessions (T0/admission to T2/42 days from T0=about 80 days from stroke occurrence). In particular, the excitability threshold (ETh) was progressively decreasing in the affected hemisphere (AH; P<0.001 between T0 and T4), while MEPs amplitude and latency tended toward normality, more in the resting state than during voluntary contraction. Slopes of neurophysiological and clinical data evolution were taken and trends of amelioration described.

CONCLUSIONS

These findings suggest that rearrangements of motor cortical neural circuitries are still operating after several months from an acute vascular monohemispheric insult, coupled with a clinical improvement in disability and neurological scores. The steepest part of the slopes were evident in the first 80 days, suggesting that this period is the one in which plastic changes of cortical motor areas are mainly active.

Intracortical excitatory and inhibitory phenomena to paired transcranial magnetic stimulation in healthy human subjects: differences between the right and left hemisphere

Intracortical inhibition (ICI) and facilitation (ICF) to paired magnetic stimuli reflect the activation of interneuronal circuits within the motor cortex. Intersubjects physiological variability of these phenomena, partly limits the usefulness of such method. Therefore, interhemispheric ICI/ICF differences might represent a more sensitive and less variable neurophysiological parameter to test the motor cortex excitability. Motor evoked potentials from the hand muscles were recorded in ten healthy subjects in a paired-pulse paradigm. Interstimulus intervals (ISIs) from 1 to 50 ms were used. The time course of ICI and ICF in the two hemispheres is consistent with minimal interhemispheric asymmetries. The interhemispheric differences of ICI and ICF could be a valuable neurophysiological marker for the diagnosis, prognosis and follow-up of neurological diseases characterized by monohemispheric damage and lateralized motor deficits.

Contralateral neglect induced by right posterior parietal rTMS in healthy subjects

We applied repetitive transcranial magnetic stimulation (rTMS) in order to induce interference on visuo-spatial perception in 11 healthy subjects. Subjects performed a visuo-spatial task requiring judgements about the symmetry of prebisected lines. Visual stimuli consisted of symmetrically or asymmetrically transected lines, tachystoscopically presented for 50 ms on a computer-monitor. Performance was examined in basal condition and during rTMS trains of 10 stimuli at 25 Hz, delivered through a focal coil over right or left posterior parietal cortex (P5 and P6 sites) and triggered synchronously with visual stimulus. Randomly intermixed sham rTMS trains were employed to control for non-specific effects. Right parietal rTMS induced a significant rightward bias in symmetry judgements as compared with basal and sham rTMS conditions. No differences emerged between other conditions.

Glycine-rich cell wall proteins act as specific antigen targets in autoimmune and food allergic disorders

Our objective was to investigate the presence of a B and T cell immune response directed against the glycine-rich cell wall protein (GRP) in patients with different autoimmune disorders and with food allergy. GRP is an ubiquitous food protein that has high homology with cytokeratins and other self proteins [Epstein-Barr virus nuclear antigen-1 (EBNA-I), heterogeneous nuclear ribonucleoprotein, fibrillar collagen] which are common targets in autoimmune disorders. A peptide (GGYGDGGAHGGGYGG) derived from GRP was used to screen human sera in direct and competitive ELISA assay. Anti-GRP-specific IgG were analyzed for their ability to cross-react with autoantigens. The intracellular cytokine profiles of the peptide-specific T cell clones obtained from representative patients have been studied. BALB/c mice were immunized with the peptide coupled to the carrier protein keyhole limpet hemocyanin (KLH). Serum IgG antibodies directed against the GRP peptide were detected in several autoimmune disorders and in food allergic patients, and were able to cross-react with autoantigens including keratin, collagen and EBNA-I. Twenty-five T cell clones showed a specific proliferative response to the GRP peptide and were of the T(h)0 phenotype. Eight of the 10 BALB/c mice immunized with the peptide coupled to KLH developed an autoimmune response. Our data suggest that phylogenetically highly conserved epitopes in plants, viruses and humans may be responsible for an autoimmune response in susceptible individuals. They also indicate that the antigen spreading of a particular sequence among apparently divergent proteins may participate to initiate or amplify an immune response.

Magnetic stimulation study during observation of motor tasks

The aim of the study was to assess if the observation of single or more complex muscle movements activates the premotor cortex in man. We stimulated by transcranial magnetic stimulation the right and left motor cortex recording from the abductor pollicis brevis of eight normal subjects, during observation of different movements performed by the examiner: (1) single movements: thumb abduction, arm elevation; (2) motor sequences: finger opposing movements performed in an ordinate sequence: 1-2, 1-3, 1-4, 1-5, 1-2ellipsis, and in a non-consecutive non-repetitive order: 1-3, 1-5, 1-4, 1-2, 1-5, 1-2ellipsis We found an increased excitability of the right cortex during observation of isolated muscle movement regardless of which muscle is moved. At the stimulation of the left cortex, MEPs were significantly increased during observation of complex muscular synergies.

Multievoked potentials in type I diabetic patients: one year follow-up study

A neurophysiological (SEP, VEP) follow-up study was carried out in 30 diabetic patients with type I diabetes mellitus of ten or more years duration. This in order to investigate whether one year of improved glucoregulation may influence the progression of central damage. In our series, patients showed a significant decrement of HbA1C levels (p < 0.05) in the one-year follow-up. In the same period the frequency of SEP and VEP abnormalities varied from 10/30 (33%) to 16/30 (53%) and from 8/30 (26%) to 5/30 (16%) respectively. This finding would suggest that prevailing glycaemic control would be a major determinant for the outcome of VEP measurements. SEP alterations, in contrast, tend to progress in a 12 months period despite a considerable improvement in glycaemic control. However, by dividing patients in two groups according mean one year HbA1C less than 8% and more than 8%, the latter group only showed a significant increasing of absolute latencies of each median and tibial SEP components. Our results suggest that VEP abnormalities are still reversible in diabetic patients with improved metabolic control. The acquired abnormalities of somatosensory pathways persist longer, but a strict glycaemic control may influence and retard the progression of central conduction involvement.

Interhemispheric asymmetries in the perception of unimanual and bimanual cutaneous stimuli. A study using transcranial magnetic stimulation

Previous studies have shown that transcranial magnetic stimulation (TMS) of the sensorimotor cortex can induce a suppression of cutaneous perception from the fingers of the contralateral hand. In this work, 17 normal subjects were submitted to focal TMS of frontal and parietal scalp sites of each hemisphere. TMS was delivered at two interstimulus intervals (20 and 40 ms) following a cutaneous electrical stimulation of the first, third and fifth digits of either hand or both hands near the subjective threshold of perception. The aim of our study was to investigate whether TMS could detect an asymmetrical hemispheric specialization in the sensory perception of unimanual and bimanual, ipsilateral and contralateral sensory stimuli. At each interpulse interval, the right parietal cortex was significantly more sensitive to TMS interference with stimulus detection for both contralateral and ipsilateral stimuli compared with the left parietal cortex. These effects were mainly evident during bimanual discrimination tasks. Our results are indicative of an interhemispheric difference in the detection of cutaneous sensation, showing right hemispheric prevalence in the perception of contralateral as well as of ipsilateral stimuli. They provide neurophysiological support in normal humans to the clinical evidence which indicates that right hemisphere lesions can indeed produce deficits in the perception of ipsilateral sensory stimuli.

Left frontal transcranial magnetic stimulation reduces contralesional extinction in patients with unilateral right brain damage

It has been demonstrated previously that transcranial magnetic stimulation (TMS) of the sensorimotor cortex can induce transient suppression of the perception of cutaneous near-threshold stimuli from fingers of the contralateral hand in normal individuals. One explanation accounting for deficits in the exploration of contralateral space following a unilateral hemispheric lesion refers to a loss of the normal interhemispheric balance, with a resultant hyperactivation of the unaffected hemisphere due to the release of reciprocal inhibition by the affected one. In order to verify this hypothesis, we investigated the effects of a TMS-induced transient dysfunction of the normal hemisphere upon contralateral tactile extinctions in two groups: (i) 14 right brain-damaged patients and (ii) 14 left brain-damaged control patients. Single-pulse TMS was delivered to frontal and parietal scalp sites of the unaffected hemisphere after an interval of 40 ms from an electrical unimanual or bimanual digit stimulation. In right brain-damaged patients, left frontal TMS significantly reduced the rate of contralateral extinctions compared with controls. After left parietal TMS, the number of extinctions was comparable to the baseline. This pattern of increased sensitivity to cutaneous stimulation ipsilateral to TMS was not observed in left brain-damaged control patients. In this group, right hemisphere TMS did not significantly alter the recognition of bimanual stimuli delivered to the space contralateral to the lesion. The suggestion is made that extinctions produced by right brain damage may be dependent on a breakdown in the balance of hemispheric rivalry in directing spatial attention to contralateral hemispace, so that the unaffected hemisphere generates an unopposed orienting response to the side of the lesion. The mechanisms whereby the left frontal TMS transiently ameliorates these deficits may involve stimulus-induced removal of a left frontal-right parietal transcallosal inhibitory flow, although interactions at subcortical levels cannot be excluded.

Effect of paired transcranial magnetic stimulation on the cortical silent period

OBJECTIVE

To investigate the behaviour of silent period (SP) during paired magnetic cortical stimulation.

BACKGROUND

Paired cortical magnetic stimulation is known to inhibit or facilitate motor evoked potentials (MEPs), but no attention has been paid to its effect on SP.

METHODS

SP was measured in the contracted first dorsal interosseus muscle after paired cortical stimuli at given interstimulus intervals (ISIs) in eight healthy subjects. Test stimulus intensity was fixed at 110% of resting threshold (RT), while three levels of conditioning stimulus intensities at 40%, 65% and 90% RT were separately employed. We also examined the effect of progressively increasing the test stimulus intensity (120-150 RT) on SP while maintaining stable conditioning stimulus intensity.

RESULTS

65% RT conditioning stimulus shortened the SP at 1-3 ms ISIs with MEP size reduction, and prolonged the SP at 15-20 ms ISIs without affecting MEP size. 90% RT conditioning stimulus showed only SP prolongation, while 40% RT showed only SP shortening at 1 ms ISI. The SP shortening at 2 ms ISI was the most evident with 120% RT test stimulus, but without correlation with the MEP size. The SP prolongation at 15 ms ISI was maximal with 110% RT test stimulus and then almost abolished with 150% RT. The SP shortening at short intervals might be due not only to spinal but also to suprasegmental mechanisms, conceivably mediating cortical excitatory drive to the corticospinal tract. The SP prolongation at intermediate intervals might be due to activation of slowly conducting, intra- or sub-cortical polysynaptic pathways exerting a facilitatory drive on the cortical inhibitory interneurons.

P300 and respiratory findings in myotonic muscular dystrophy

Ten patients with myotonic muscular dystrophy (MD) were examined by auditory event-related potentials (P300 ERPs), spirometric and blood gas analyses: arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2) and arterial oxygen saturation (SaO2). The aim of the study was to analyse the frequency of ERP abnormalities in this disease and to determine whether the neurophysiological evidence of cognitive impairment might be related to the ventilatory function abnormalities frequently described in MD. The mean P300 latency was significantly altered in MD patients compared with controls; P300 latencies did not correlate with spirometric parameters, blood gas values or with age, age at onset, duration or clinical status of the disease. This study provides neurophysiological evidence of cognitive impairment in MD patients. The cognitive deficits are not related to alveolar hypoventilation and appear to be a non progressive feature of the disease.

Evoked potential study and radiological findings in patients with systemic lupus erythematosus

We performed clinical, radiological (MRI) and neurophysiological (NCV, SEPs, and BAEPs) investigations in 36 unselected patients affected by Systemic Lupus Erythematosus (SLE). Fifteen patients (42%) presented clear neurological events and were considered as definite neuropsychiatric lupus (NPLE); 21 (58%) presented minor subjective complaints or no neurological problems referable to SLE and were considered as no-NPLE. Twenty-three patients (64%) showed neurophysiological abnormalities: 21 (58%) presented central abnormal neurophysiological measurements (including SEP and BAEP values), while 17 (47%) has slowed peripheral nerve conduction. Twenty-six out of 36 patients executed brain MRI examination. High intensity spots (HIS) in deep or subcortical white matter were the most common abnormalities and were present in 19 of the 26 patients (73%). We found that the incidence of neurophysiological and radiological abnormalities did not significantly differ in neurologically symptomatic and asymptomatic patients. Central nervous system impairment evidenced by abnormal N13-20 interpeak intervals (p = 0.05) and HIS (p = 0.01) findings was significantly associated with the presence of cutaneous vasculitis; while peripheral nerve involvement was significantly more frequent in patients with renal failure (p = 0.006).

Reorganization of cortical motor area in prior polio patients

OBJECTIVE

Focal transcranial magnetic stimulation (TMS) was used to study the motor maps of upper limb muscles in 7 adult patients with a history of paralytic poliomyelitis. The aim of the study was to verify the potential for long-term cortical reorganization of a selective peripheral motor neuron lesion suffered early in life.

METHODS

Patient selection was based on the prevalent involvement of proximal muscles in only one of the upper limbs. Motor evoked potentials (MEPs) were recorded from deltoid and abductor pollicis brevis (APB) muscles. Each muscle map was characterized by area (no. of excitable positions), volume (the sum of MEP amplitudes at all scalp positions), maximal amplitude (the highest MEP recorded).

RESULTS

In the patients, the mean area, volume and maximal amplitude were significantly greater in affected vs. contralateral deltoid (P<0.05) and vs. controls (P<0.01). No significant differences were found in APB map parameters. The APB/deltoid ratio for area was lower in the affected compared with the unaffected side and controls (P = 0.06). Cortical reorganization was not significantly correlated with motor performance.

CONCLUSION

These findings are consistent with a rearrangement in human motor pathways targeting muscles affected by a lower motor neuron lesion.

Superior thyroid artery lesion after US-guided chemical parathyroidectomy: angiographic diagnosis and treatment by embolization

A 71-year-old woman presented with a life-threatening thyroid hemorrhage after US-guided chemical parathyroidectomy. The diagnosis was made by angiography followed by immediate embolization of a pseudoaneurysm of the left superior thyroid artery. Embolization controlled the hemorrhage, obviating the need for surgery. The patient made a full recovery with no evidence of further hemorrhage. Pseudoaneurysm of the superior thyroid artery is a rare cause of hemorrhage and percutaneous embolization is an effective method of treatment.

A method to monitor motor cortical excitability in human stroke through motor evoked potentials

We describe a procedure aimed to analyse Motor Evoked Potentials (MEPs) interhemispheric differences in motor excitability in a monohemispheric subacute stroke population. This protocol has specifically been oriented to scan for any differences in MEPs amplitude at rest and during contractions from a hand muscle, Abductor Digiti Minimi (ADM), after focal Transcranial Magnetic Stimulation (TMS) in both Affected (AH) and Unaffected (UH) Hemispheres. Stroke patients can be included in the protocol if they have suffered acute stroke during the two to four month period to the admission in our rehabilitation hospital. The purpose of this protocol is to establish whether any clear pattern of interhemispheric responsiveness exists and/or to define any possible correlation between MEPs and clinical data. Disability and neurological scores are evaluated to allow a numerical comparison with electrophysiological data. Two recording sessions are planned: the first when the selected patient is admitted (T1) and the second after 8 weeks (T2). Such a period has been arbitrarily chosen because it represents a reliable time after the first recording in order to observe clinical amelioration if present. Criteria for reproducibility of experimental conditions are illustrated.

Prognostic value of somatosensory evoked potentials in stroke

Median and tibial somatosensory evoked potentials (SEPs) were performed on 12 patients at three and twelve weeks after a first acute stroke, the relationship with motor and functional outcome as measured by British Medical Scale and Barthel Index was searched. Results indicated that the amplitude abnormalities of cortical potentials performed about three weeks after stroke are a good indicator of a poor motor and functional impairment after three months. Moreover changes in amplitude appeared more frequent and permanent than the latency abnormalities.

Modulation of intracortical excitability for different muscles in the upper extremity: paired magnetic stimulation study with focal versus non-focal coils

OBJECTIVE

Intracortical excitability was studied for 4 muscles in the upper extremity by paired transcranial magnetic stimulation on the motor cortex, using focal and non-focal coils.

METHODS

Surface EMG responses of two hand and two forearm muscles were simultaneously recorded in 13 healthy subjects, after delivering paired stimuli at interstimulus intervals (ISIs) of 1-50 ms using circular and figure-of-8 (focal) coils. The intensities of conditioning and test stimuli were submotor and supramotor thresholds, respectively.

RESULTS

Paired stimulation using a circular coil showed constant inhibition at 2 ms ISI for all muscles, but not at 5 ms ISI, and induced facilitation at 10 ms ISI. The results using a focal coil were similar to those with a circular coil at all ISIs except at 5 ms ISI, where the former showed inhibition. At 20 and 30 ms ISIs, there was interindividual variability for both coils, some subjects showing inhibition and others facilitation.

CONCLUSIONS

The difference of the inhibition at 5 ms ISI between using circular and focal coils could be attributed to the cortical mechanism. The inhibitory effect at 2 ms ISI, consistently observed for the 4 muscles with both types of coil, could be easily applied to assess the inhibitory intracortical function in patients with neurological diseases.