Biomedical subjects

M Oliveri

Publications and source records attributed to M Oliveri.

At least 37 records · Page 2Linked to original sources

PubMed2000

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.

Adult↗

PubMed2000

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.

Cerebral Cortex↗

PubMed2000

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.

Adult↗

PubMed2000

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.

Adult↗

PubMed2000

Neurophysiological evaluation of tactile space perception deficits through transcranial magnetic stimulation.

We describe a procedure useful to investigate the contralateral space perception deficits frequently encountered in patients with unilateral right brain damage. In particular, we focused on the phenomenon of extinction, i.e., the failure to perceive a contralesional stimulus only when a symmetrical contralateral stimulus is simultaneously applied. Fifteen right brain- and 15 left brain-damaged patients were examined. Somatosensory perception was evaluated by using a dedicated electronic device able to provide electrical stimuli of variable intensity to digits of one or both hands. The electrical stimulator was able to trigger a magnetic brain stimulator connected with a focal figure of eight coil. Threshold electrical stimuli were delivered to one or both hands of the patients, who were asked to indicate whether they perceived the stimulus (i) and to localise it (them). The electrical stimulator was connected with a magnetic stimulator with an interstimulus interval (ISI) of 40 msec (electrical stimulation preceding the transcranial one). Focal threshold transcranial magnetic stimulation (TMS) was applied to frontal and parietal scalp sites of the unaffected hemisphere. At each interpulse interval we found that TMS of the unaffected hemisphere was associated to a decrease in the level of contralesional extinction. Our method demonstrates that a basic deficit underlying neglect and extinction of contralateral space in unilaterally brain damaged patients is the interhemispheric imbalance between the two hemispheres in directing contralateral attention. A transient interference with the function of the unaffected hemisphere can improve these deficits, suggesting a possible application of TMS in the daily clinical practice for speeding up recovery from neglect.

Cognition↗

PubMed2000

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.

Female↗

PubMed2000

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.

Aged↗

PubMed2000

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.

Amino Acid Sequence↗

PubMed2000

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.

Adolescent↗

PubMed1999

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.

Adult↗

PubMed1999

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.

Cerebrovascular Disorders↗

PubMed1999

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.

Adult↗

PubMed1999

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.

Adult↗

PubMed1999

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.

Adult↗

PubMed1999

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.

Aged↗

PubMed1999

Repeat tear of postoperative meniscus: potential MR imaging signs.

PURPOSE: To determine the usefulness of five magnetic resonance (MR) signs of repeat tears of the postoperative meniscus. MATERIALS AND METHODS: Fat-saturated proton-density-weighted and T2-weighted MR images in 20 patients who had undergone at least two knee surgeries were reviewed. Second-look arthroscopic confirmation of meniscal status was available in all patients. MR images of 39 menisci (10 repeat tears, 11 postoperative menisci without repeat tears, three tears in previously normal menisci, and 15 normal menisci) were evaluated for (a) a linear area of abnormal signal intensity extending to an articular surface on intermediate-weighted images, (b) abnormal meniscal morphology, (c) likelihood of a typical postoperative appearance, (d) fluid extending into the linear area on T2-weighted images, and (e) cartilage defects. Two radiologists rated their confidence on a five-point scale for the presence of these signs and were compared for level of agreement. RESULTS: The intraclass correlation coefficient (range, 0.75-0.91) indicated a high level of agreement. Areas under the receiver operating characteristic curves were large (range, 0.70-0.87) for all five signs, with a line (grade 3 signal intensity) and fluid within a line having the highest areas. These two signs also had the highest statistical scores (chi 2 = 14.12 and 13.30; P < .002; odds ratio, 1.588 and 1.599 for the line and the fluid within the line, respectively). CONCLUSION: The two best MR signs of repeat tear of the postoperative meniscus were the presence of a line and fluid within the line extending to an articular surface.

Adult↗

PubMed1999

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.

Adolescent↗

PubMed1998

Neurophysiological and radiological findings in myotonic dystrophy patients.

Somatosensory evoked potentials (SEPs) and brainstem auditory evoked potentials (BAEPs) were recorded in 10 patients with myotonic dystrophy and in 20 sex and age-matched healthy controls. In all patients a brain MRI examination was also performed. In our results, the significantly longer absolute peak latencies of the SEPs and the abnormal increasing of the later components of the BAEPs suggest an involvement of the afferent sensory and central auditory pathways. Brain MRI showed white matter hyperintense lesions (WMHL) in eight patients (80%). No correlations were found between individual abnormal electrophysiological parameters or severity of WMHL and age, age at onset, disease duration or muscular impairment. The total number (SEP + BAEP) of electrophysiological abnormalities significantly correlated with muscular impairment (p < 0.05) and MRI changes (p < 0.005), suggesting a strict pathogenetic linkage between muscular and nervous system alterations in this disease.

Journal Article↗