Emotional processing in RRMS patients: Dissociation between behavioural and neurophysiological response.

BACKGROUNG: Multiple sclerosis (MS) results in a broad range of symptoms, including motor, visual, cognitive, and neuropsychiatric deficits. Some studies, considering affective facial expressions to study emotion processing, demonstrated emotion recognition difficulties in MS patients. OBJECTIVE: We investigated the impact of MS on the emotional-behaviour rating and neurophysiological response (Event Related Potentials-ERP) through a battery of affective visual stimuli selected from the International Affective Picture System (IAPS). METHODS: Twenty patients with diagnosis of Relapsing Remitting MS (RRMS) and 20 Healthy Controls (HC) matched by age, gender and education were enrolled. Each of them, after a neuropsychological assessment, were asked to evaluate arousal and valence of affective visual stimuli. RESULTS: Our results showed higher P300 amplitudes in RRMS patients than HC group for pleasant and unpleasant images. Moreover, RRMS patients showed lower Reaction Time (RT) respect HC in valence rating. No other effect did emerge between groups. CONCLUSION: Our study shows early compensatory cerebral mechanisms in RRMS patients throughout emotional information processing, particularly for unpleasant and pleasant stimuli. We hypothesize that this compensatory cerebral mechanism reduces the behavioural dissimilarity between patients and HC.

Cognitive Impairment in Relapsing-Remitting Multiple Sclerosis Patients with Very Mild Clinical Disability.

Cognitive dysfunction affects 40-65% of multiple sclerosis (MS) patients and can occur in the early stages of the disease. This study aimed to explore cognitive functions by means of the Italian version of the minimal assessment of cognitive function in MS (MACFIMS) in relapsing-remitting MS (RRMS) patients with very mild clinical disability to identify the primarily involved cognitive functions. Ninety-two consecutive RRMS patients with Expanded Disability Status Scale (EDSS) scores ≤ 2.5 and forty-two healthy controls (HC) were investigated. Our results show that 51.1% of MS patients have cognitive dysfunction compared to HC. An impairment of verbal and visual memory, working memory, and executive functions was found in the RRMS group. After subgrouping RRMS by EDSS, group 1 (EDSS ≤ 1.5) showed involvement of verbal memory and executive functions; moreover, group 2 (2 ≤ EDSS ≤ 2.5) patients were also impaired in information processing speed and visual memory. Our results show that utilizing a comprehensive neuropsychological assessment, approximately half of MS patients with very mild physical disability exhibit cognitive impairment with a primary involvement of prefrontal cognitive functions. Detecting impairment of executive functions at an early clinical stage of disease could be useful to promptly enroll MS patients in targeted rehabilitation.

White matter reduced streamline coherence in young men with autism and mental retardation.

BACKGROUND AND PURPOSE: It has been proposed that white matter alterations might play a role in autistic disorders; however, published data are mainly limited to high-functioning autism. The goal of this study was to apply diffusion tensor imaging (DTI) and fiber tractography (FT) to study white matter in low-functioning autism and the relationship between white matter and cognitive impairment. METHODS: Ten low-functioning males with autism (mean age: 19.7 +/- 2.83 years) and 10 age-matched healthy males (mean age: 19.9 +/- 2.64 years) underwent DTI-MRI scanning. fractional anisotropy (FA) maps were analyzed with whole brain voxel-wise and tract-of-interest statistics. Using FT algorithms, white matter tracts connecting the orbitofrontal cortex (OFC) with other brain regions were identified and compared between the two groups. FA mean values of the autistic group were correlated with intelligence quotient (IQ) scores. RESULTS: Low-functioning autistic subjects showed a reduced tract volume and lower mean FA values in the left OFC network compared with controls. In the autistic group, lower FA values were associated with lower IQ scores. CONCLUSIONS: We showed evidence of OFC white matter network abnormalities in low-functioning autistic individuals. Our results point to a relationship between the severity of the intellectual impairment and the extent of white matter alterations.

Integrating drivers influencing the detection of plant pests carried in the international cut flower trade.

This paper analyses the cut flower market as an example of an invasion pathway along which species of non-indigenous plant pests can travel to reach new areas. The paper examines the probability of pest detection by assessing information on pest detection and detection effort associated with the import of cut flowers. We test the link between the probability of plant pest arrivals, as a precursor to potential invasion, and volume of traded flowers using count data regression models. The analysis is applied to the UK import of specific genera of cut flowers from Kenya between 1996 and 2004. There is a link between pest detection and the Genus of cut flower imported. Hence, pest detection efforts should focus on identifying and targeting those imported plants with a high risk of carrying pest species. For most of the plants studied, efforts allocated to inspection have a significant influence on the probability of pest detection. However, by better targeting inspection efforts, it is shown that plant inspection effort could be reduced without increasing the risk of pest entry. Similarly, for most of the plants analysed, an increase in volume traded will not necessarily lead to an increase in the number of pests entering the UK. For some species, such as Carthamus and Veronica, the volume of flowers traded has a significant and positive impact on the likelihood of pest detection. We conclude that analysis at the rank of plant Genus is important both to understand the effectiveness of plant pest detection efforts and consequently to manage the risk of introduction of non-indigenous species.

CSF from MS patients can induce acute conduction block in the isolated optic nerve.

In the present in vitro electrophysiological study, the acute effects of the cerebrospinal fluid (CSF) from multiple sclerosis (MS) and control subjects were measured on the axonal conduction of rat optic nerve, a central tract that is commonly affected in MS. Optic nerve compound action potential (CAP) amplitude was insensitive to the application of CSF obtained from the whole population of non-MS patients and from seven of 15 MS CSF. In the remaining eight MS cases, conversely, a time-dependent depression of CAP amplitude was observed. The reversible blockade of ion channels by soluble substances might account, at least in part, for the transient symptoms often seen in MS patients.

Different TMS patterns of intracortical inhibition in early onset Alzheimer dementia and frontotemporal dementia.

OBJECTIVE: To investigate putative changes in cortical excitability of patients affected by early-onset mild dementia by means of transcranial magnetic stimulation (TMS) and to verify whether a peculiar neurophysiological profile may contribute to characterise Alzheimer's disease (AD) vs frontotemporal dementia (FTD). METHODS: Motor threshold and intracortical inhibition (ICI) and facilitation (ICF) after paired-pulse TMS (inter-stimulus intervals from 1 to 20 ms) were studied in two groups of early-onset demented patients with a neuropsychological profile suggestive of AD (n = 12) and FTD (n = 8). Twelve age-matched healthy subjects were considered as control group. In both patient groups, recordings were performed before and after a single oral dose of 4 mg galantamine. RESULTS: No significant difference in motor threshold was observed among the three studied groups. On the contrary, early-onset AD showed a significant reduction of ICI compared to control group, no changes were detected in FTD patients. No significant changes in ICF were found between both patient groups and healthy subjects. The acute administration of galantamine reversed the modified ICI in AD group. CONCLUSIONS: The differential pattern of ICI exhibited by early-onset AD vs FTD in the early stage of disease may represent a non-invasive, reproducible electrophysiological tool, which may contribute to early differential diagnosis and, possibly, to monitor therapeutic effectiveness. SIGNIFICANCE: The present results support the possibility that subtle, early modifications in intracortical circuitry features AD, but not FTD patients.

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.

Deep brain stimulation of both subthalamic nucleus and internal globus pallidus restores intracortical inhibition in Parkinson's disease paralleling apomorphine effects: a paired magnetic stimulation study.

OBJECTIVE: We investigated the effect of bilateral subthalamic nucleus (STN) and internal globus pallidus (GPi) deep brain stimulation (DBS) on intracortical inhibition (ICI) in patients with advanced Parkinson's disease (PD). METHODS: The activity of intracortical inhibitory circuits was studied in 4 PD patients implanted with stimulating electrodes both in STN and GPi by means of paired-pulse transcranial magnetic stimulation, delivered in a conditioning-test design at short (1-6 ms) interstimulus intervals (ISI). The effect of apomorphine on the same PD patients was also investigated. RESULTS: We observed that implanted PD patients showed a significant increase in ICI during either bilateral STN or GPi DBS at 3 ms ISI, and during bilateral STN DBS at 2 ms ISI in comparison to their off DBS condition. The same statistical improvement was observed during apomorphine infusion at 3 and 2 ms ISI. In each condition, the electrophysiological changes were associated with a significant clinical improvement as measured by the Unified Parkinson's Disease Rating Scale motor examination. CONCLUSIONS: These results are consistent with the hypothesis that basal ganglia DBS can mimic the effects of pharmacological dopaminergic therapy on PD patients cortical activity. We propose that in PD patients, the basal ganglia DBS-induced improvement of ICI may be related to a recovery in modulation of thalamo-cortical motor pathway.

Factor V Leiden mutation and patent foramen ovale in ischemic stroke.

We report a 47-years-old male with ischemic stroke, whose arteriographic and echocardiographic investigations did not reveal any steno-occlusive arterial disease or embolic source from the left cardiac chambers. A transesophageal echocardiogram showed a patent foramen ovale (PFO), whilst laboratory screening for coagulation abnormalities showed heterozygosity for factor V Leiden mutation. The significance of the association of PFO with factor V Leiden mutation is discussed as a possible cause of ischemic stroke through paradoxical embolism from a venous source. The high prevalence of these two conditions in the general population is emphasized and the indication for anticoagulant therapy is discussed.

Effect of apomorphine on cortical inhibition in Parkinson's disease patients: a transcranial magnetic stimulation study.

In this study, transcranial magnetic stimulation (TMS) of the primary motor hand area was used to test cortical excitability in Parkinson's disease (PD) patients. Motor evoked potentials (MEPs) to TMS were studied at rest by utilising distinct paired-pulse TMS protocols. Out of 29 untreated PD patients and 29 healthy subjects, early cortical inhibition (1-6 ms) was studied in a first subgroup of 17 PD patients and 15 healthy subjects, whereas late cortical inhibition (20-200 ms) was studied in a second subgroup of 21 PD patients and 19 healthy subjects. In all PD patients the same TMS protocols were performed before and after 3 h of apomorphine infusion. In comparison to healthy subjects, untreated PD patients showed a significant reduction of both early and late cortical inhibition, which was maximal at 2-3 ms, and at 80-100 ms, respectively. Apomorphine administration consistently reversed all the MEP abnormalities found in PD patients. The lack of TMS effects on the Hoffman's reflex (HR), at those intervals revealing the reduced inhibition in PD patients, is compatible with a supraspinal origin of the observed MEP abnormalities. Our data suggest that the cortical and/or subcortical loss of dopaminergic transmission in PD patients is associated with impaired motor cortical inhibitory mechanisms, as tested by a decreased early and late MEP inhibition.

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.

Ipsilateral activation of the unaffected motor cortex in patients with hemiparetic stroke.

BACKGROUND AND PURPOSE: Recent research has shown that following stroke patients can display ipsilateral activity reflecting a functional link between the undamaged hemisphere and the affected upper limb on the same side of the body. In the present study the capacity for ipsilateral activation is documented during recovery by using transcranial magnetic stimulation (TMS) and transcranial Doppler (TCD). METHODS: Fourteen patients affected by hemispheric stroke were examined with TMS and TCD within 48 h of onset, and again 6 months later. Neurological signs were scored with reference to the NIHSS, and patients executed a thumb to finger opposition task so as to further estimate the motor deficit. Twenty healthy volunteers represented the control population. RESULTS: (1) Both TMS and TCD yielded homogeneous results showing ipsilateral activity between affected hands and undamaged hemispheres. On stimulating the motor cortex 3 cm anterior and 3 cm lateral to Cz, a scalp site remote from the primary motor area, ipsilateral motor evoked potentials (iMEPs) from hand muscles were found in recovered patients. (2) In 8 controls iMEPs with smaller amplitudes than patients could be obtained by stimulating only the left hemisphere. (3) TCD revealed increased blood flow velocity in the ipsilateral MCA by activating the recovering hand (10.5+/-3.3%; P<0.001). CONCLUSION: TMS reveals a specific area in the motor cortex from which ipsilateral MEPs can be elicited and both TMS and TCD indicate that an ipsilateral corticospinal tract can be accessible in some adult controls or becomes unmasked after cerebral damage.

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.

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.

Pharmacologic reversal of cortical hyperexcitability in patients with ALS.

OBJECTIVE: To reverse the profile of abnormal intracortical excitability in patients with ALS by administering drugs that promote GABAergic transmission. BACKGROUND: Transcranial magnetic stimulation (TMS) has revealed abnormalities of cortical inhibition in ALS, a reduction of the silent period, and the absence of intracortical inhibition normally occurring in response to paired TMS. Impaired inhibitory transmission could play a role in the physiopathology of this illness. METHODS: Using paired TMS with conditioning stimuli from 1-to-6-msec-interstimulus intervals, we investigated 16 patients with ALS. The protocol included: (1) the "drug-free" profile of paired TMS; (2) paired TMS 30 minutes after the intake of diazepam (3.5 mg); (3) paired TMS after 3 weeks' treatment with gabapentin (GBP) (600 mg/day) or riluzole (50 mg/twice a day). RESULTS: Intracortical inhibition is lost in patients with ALS, and this abnormal profile is reversed by diazepam or sustained treatment with GBP. We also noted that motor-evoked potential amplitudes to single stimuli increased (p<0.01) after diazepam and GBP. CONCLUSIONS: The demonstration of pharmacologic reversal of hyperexcitability in patients with ALS makes a potentially significant contribution toward understanding the pathophysiology of a disease that has so far eluded an effective cure.

The effect of riluzole in amyotrophic lateral sclerosis: a study with cortical stimulation.

A population of 31 patients with sporadic amyotrophic lateral sclerosis (ALS) was selected for a prospective open study based on treatment with riluzole. A neurophysiological evaluation was performed by means of single and paired transcranial magnetic stimulation (TMS). The examined parameters, excitability threshold, motor evoked potential (MEP) duration, silent period (SP) duration and time course of intracortical inhibition to paired TMS after 6 months treatment, were matched against those recorded from the patients themselves before the beginning of treatment and from 20 (single TMS) or 10 (paired TMS) age-matched control subjects. Normal behaviour of the SP in response to increasing TMS was found in the treated patients; they showed a significant linear correlation between these two parameters (r=0.96) comparable to that calculated for controls (r=0.98), and significantly different with respect to drug-free patients (r=0.8, P=0.014). A significant reduced size of the 'conditioned' MEPs to paired stimulation was documented in the treated patients compared with the untreated patients (P=0.002). Our neurophysiological contribution to the assessment of the effect of riluzole on the motor cortical inhibitory property in ALS may be considered a setting for controlled trials in extended patient series, even in a pre-clinical phase.

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.

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.

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.

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.