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Biomedical subjects

P Pasqualetti

Publications and source records attributed to P Pasqualetti.

At least 73 records · Page 4Linked to original sources
PubMed1999

Word-list learning in normally developing children: effects of semantic organization and retention interval.

Immediate and 15-min delayed recall of semantically related or unrelated word lists was investigated in 144 normally developing children ranging from 5 to 10 years of age. Immediate recall for the related and unrelated lists increased in a parallel fashion as a function of age. The ability to cluster semantically related items during immediate recall also improved with age. However, in no age class recall scores and clustering indexes were significantly associated. Forgetting rate passing from the last immediate to the delayed recall trial increased for the unrelated list but decreased for the related list of words as a function of age. Results of regression analyses revealed that a developmental increase in forgetting on the unrelated list was actually due to the higher number of words recalled in the last immediate trial by older children. As for the related list, instead, the larger reliance on the clustering strategy of recall by older children was responsible for the progressive reduction of forgetting.

Aging↗
PubMed1999

Italian multicentre study of carpal tunnel syndrome: clinical-neurophysiological picture and diagnostic pathway in 461 patients and differences between the populations enrolled in the northern, central and southern centres. Italian CTS Study Group.

The economic trend in our country, as in other countries, now requires us to pay more attention to the social and economic aspects of health. Therefore, it is important to evaluate the diagnostic pathway and the socioeconomic aspects of pathologies. The Italian CTS Study Group performed a wide multicentre and multidimensional study (through a patient-, physician- and neurophysiologically oriented evaluation) on 461 idiopathic CTS patients to evaluate the clinical-neurophysiological picture and the diagnostic pathway. The whole population and the differences between the populations enrolled in the neurophysiological centres of the northern, central and southern parts of Italy were analysed. This study provided new and interesting information. As concerns the whole population, we observed different diagnostic pathways in relation to the level of schooling. As concerns the comparison of the populations, the southern centres have a population of CTS patients with higher frequency of hand stress and more severe nerve impairment.

Adult↗
PubMed1999

Recovery of LV contractility in man is enhanced by preischemic administration of enflurane.

BACKGROUND: Volatile anesthetics enhance postischemic functional recovery in animal models; this effect has not been investigated in man. METHODS: Twenty-two patients undergoing coronary surgery were randomized to enflurane administration (0.5% to 2%) for 5 minutes to reduce systolic blood pressure by 20% to 25% immediately before cardioplegic arrest. Left ventricular contractility was assessed by pressure-area relations using echocardiographic automated border detection during inflow occlusion before and after cardiopulmonary bypass. Linear regression analysis in 16 patients with paired data sets assessed changes in contractility. RESULTS: The relation was highly linear (r = 0.95+/-0.02). A change of slope versus the change in x intercept was detected in controls (mean difference, 16.1 mm Hg/cm2, 95% confidence limits, 5.9 to 26.3; 2.2 cm2, 95% confidence limits, -1.1 to 5.5; p = 0.007), which was different from those of treated patients (mean difference, 0.7 mm Hg/cm2, 95% confidence limits, -2.2 to 3.7; -0.06 cm2, 95% confidence limits, -1.6 to 1.5; p > 0.2). Analysis of covariance in the overall group confirmed a significant effect of treatment (p = 0.002). CONCLUSIONS: Enflurane enhances postischemic functional recovery, possibly through pharmacologic preconditioning of myocardium.

Aged↗
PubMed1999

Parallel processing of sensory inputs: an evoked potentials study in Parkinsonian patients implanted with thalamic stimulators.

In two drug-resistant Parkinsonian subjects, who underwent thalamic chronic stimulation for extrapyramidal symptoms relief, median nerve somatosensory evoked potentials (SEPs) were recorded before and at different times following the thalamic lead implant. In both subjects, a transient obliteration of post-rolandic SEPs components was detected; pre-rolandic waves' amplitude was preserved or showed a tendency to increase after the beginning of chronic stimulation. Parietal waves' amplitude totally recovered pre-surgical values after 1 month. Latency of both pre- and post-central components remained stable. The 'dissociate behaviour' of the examined waves following the thalamic implant reinforces the hypothesis that short-latency sensory inputs are processed by separate and independent routes which are functionally segregated at subcortical level.

Aged↗
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

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

Corticospinal excitability modulation to hand muscles during movement imagery.

Motor evoked potentials (MEPs) to magnetic transcranial stimulation (TCS) were recorded from right abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles, sharing the same peripheral innervation but engaged in two different motor demands. In seven healthy and trained subjects, the latencies, amplitudes and variability of MEPs were investigated under the following, randomly intermingled, conditions: full muscular and mental relaxation; mental simulation of selective index finger or little finger abduction; mental non-motor activity (arithmetical calculation); and real motor task (little and index finger abduction). The whole procedure was performed by continuous audiovisual monitoring of electromyographic 'silence' in the tested muscles. The maximal facilitatory effects (= latency shortening and amplitude increase) on MEPs were induced by the real motor task. An amplitude potentiation of MEPs in both tested muscles was present during non-motor mental activity, in comparison to basal values. A further amplitude potentiation, without latency shifts, was confined to the muscle acting as 'prime mover' for the mentally simulated movement, according to the motor program dispatched but not executed by the subject. Similar results were also found in the F-wave, showing that mental simulation affects spinal motoneuronal excitability as well, although -- due to the lack of MEP and F-wave latency shift -- the main effect takes place at cortical level. The study shows that movement imagery can focus specific facilitation on the prime-mover muscle for the mentally simulated movement. This is mainly evident on FDI muscle, which controls fingers (i.e. the index) with highly corticalized motor representation.

Adult↗
PubMed1999

Insight in dementia: when does it occur? Evidence for a nonlinear relationship between insight and cognitive status.

Lack of insight or impaired awareness of deficits in patients with dementia is a relatively neglected area of study. The aim of this study was to evaluate insight in a group of demented patients with two assessment scales and to assess their relationship with the cognitive level of disease severity. Sixty-nine consecutive patients affected by Alzheimer's disease (n = 37) and vascular dementia (n = 32) with a wide range of cognitive impairment (MMSE = 17.0 +/- 6.4) were recruited. Insight was evaluated with the Guidelines for the Rating of Awareness Deficits (GRAD)--specifically targeted to memory deficits--and the Clinical Insight Rating scale (CIR), evaluating a broader spectrum of insight (reason for the visit, cognitive deficits, functional deficits, and perception of the progression of the disease). In the whole sample, GRAD and CIR were significantly associated with MMSE (Spearman's coefficient = .51, p < .001; and r = -.55, p < .001) and with Clinical Dementia Rating scale (-.57, p < .001; and r = .57, p < .001) respectively. The shape of the relationship of MMSE with CIR and GRAD scales was assessed with spline smoothers suggesting that the relationship follows a trilinear pattern and is similar for both scales. Insight was uniformly high for MMSE scores > or = 24, showed a linear decrease between MMSE scores of 23 and 13, and was uniformly low for MMSE scores < or = 12. The trilinear model of the association between insight and cognitive status reflects more closely the observable decline of insight and can provide estimates of when the decline of insight begins and ends.

Activities of Daily Living↗
PubMed1999

Cerebrovascular reactivity in carotid artery occlusion: possible implications for surgical management of selected groups of patients.

OBJECTIVES: The aim of this study was to use transcranial Doppler ultrasonography to investigate cerebrovascular reactivity to hypercapnia in the middle cerebral arteries of patients with carotid occlusion with different outcomes. PATIENTS AND METHODS: Cerebrovascular reactivity to hypercapnia was calculated with the breath-holding index (BHI). Patients with unilateral carotid occlusion were divided as follows: asymptomatic (20 patients), transient ischemic attack (TIA) (20 patients), minor (20 patients) and major stroke (14 patients). Values of BHI homolateral to the carotid occlusion were compared with those of 25 healthy subjects and 34 stroke patients without significant carotid stenosis. RESULTS: BHI values were comparable in healthy controls, non stenotic stroke patients and asymptomatic occluded patients. BHI values of patients with symptomatic occlusion were significantly lower than those of the above-mentioned groups (P<0.0001). Moreover, the reduction of BHI was significantly associated with the extent of the neurological impairment. In fact, BHI values were significantly higher in TIA than in minor and major stroke (P<0.0001) and in minor than in major stroke patients (P<0.02). Finally, we found that a BHI value homolateral to carotid occlusion of 0.69 can be considered the cut-point for distinguishing between symptomatic and asymptomatic patients. CONCLUSION: Prospective studies are needed to demonstrate if the presence of this threshold value may help in selecting a subset of patients with asymptomatic carotid occlusion or with transient or mild neurological deficit with the highest probability of benefiting from surgical therapy.

Analysis of Variance↗
PubMed1999

Outcome of carotid artery occlusion is predicted by cerebrovascular reactivity.

BACKGROUND AND PURPOSE: The purpose of this study was to investigate the possibility of obtaining prognostic indications in patients with internal carotid occlusion on the basis of intracranial hemodynamic status, presence of previous symptoms of cerebrovascular failure, and baseline characteristics. METHODS: Cerebral hemodynamics were studied with transcranial Doppler ultrasonography. Cerebrovascular reactivity to apnea was calculated by means of the breath-holding index (BHI) in the middle cerebral arteries. Sixty-five patients with internal carotid artery occlusion were followed-up prospectively (median, 24 months), 23 patients were asymptomatic and 42 symptomatic (20 with transient ischemic attack and 22 with stroke). RESULTS: During the follow-up period, 11 symptomatic patients and 1 asymptomatic patient had another ischemic event ipsilateral to carotid occlusion. Among factors considered, only lower BHI values in the middle cerebral arteries ipsilateral to carotid occlusion and older age were significantly associated with the risk of developing symptoms (P=0.002 and P=0.003, respectively; Cox regression multivariate analysis). Based on our data, a cut point of the BHI value for distinguishing between pathological and normal cerebrovascular reactivity was determined to be 0.69. All patients except one, who developed TIA or stroke during the follow-up period, had BHI values ipsilateral to carotid occlusion of <0.69. CONCLUSIONS: These data suggest that impaired cerebrovascular reactivity is predictive for cerebral ischemic events in patients with carotid occlusion.

Aged↗
PubMed1998

Follow-up of interhemispheric differences of motor evoked potentials from the 'affected' and 'unaffected' hemispheres in human stroke.

We analysed motor-evoked potentials (MEPs) from the hand muscles during focal transcranial magnetic stimulation (TCS) in both the affected (AH) and the unaffected (UH) hemispheres of 17 monohemispheric stroke patients followed-up in subacute stage. Recording sessions were performed at 2 (T1 session) and 4 (T2 session) months from acute stroke. Clinical and functional scores were evaluated. An age-sex matched group of 20 healthy subjects have been referenced. In T1, relaxed MEPs from AH were smaller than UH (p<0.001) and normals (p<0.001). In T2, an increase of AH relaxed-MEPs amplitude was observed, combined with an improvement of clinical and functional scores (p<0.001). On the other hand, the amplitude of contracted MEPs from the AH in T1 was larger than in the normal group. This parameter decreased toward normal limits in T2, provided that the amplitude of the MEPs from the AH improved, while it further increased when TCS of the AH continued to fail in eliciting MEPs. This phenomenon was statistically combined with clinical improvement of disability and neurological scores. Recovery of the excitability AH threshold with progressive 'balancing' of the UH hyperresponsiveness represents a good prognostic parameter for clinical outcome of hand motor function.

Adult↗
PubMed1998

Corticospinal excitability modulation during mental simulation of wrist movements in human subjects.

Motor evoked potentials (MEPs) to magnetic transcranial stimulation (TCS) were simultaneously and bilaterally recorded from flexor carpi radialis (FCR) and extensor communis digitorum (ECD) muscles in seven healthy and trained subjects. Latencies and amplitudes characteristics of MEPs were investigated under the following randomised conditions: muscular and mental relaxation; mental simulation, during absolute muscular relaxation, selective flexion or extension of the right or left wrist muscles; arithmetical calculation with muscular relaxation. Unspecific, diffuse facilitatory effects on MEPs amplitude were induced by mental non motor activity (arithmetical calculation). A further specific and lateralised amplitude potentiation on the agonist muscle acting as 'prime mover' for the mentally simulated movement was consistently found in all the subjects, without significant latency changes. Inhibitory effects on antagonists were evident only in two subjects.

Adult↗
PubMed1998

On the reorganization of sensory hand areas after mono-hemispheric lesion: a functional (MEG)/anatomical (MRI) integrative study.

The topography of primary sensory cortical hand area following a monohemispheric lesion (sudden = stroke; progressive = neoplasm) was investigated in relationship with clinical recovery of sensorimotor deficits. Twenty seven patients with monohemispheric lesions were studied in a clinically stabilized condition. Functional informations from magnetoencephalography (MEG) were integrated with anatomical data from magnetic resonance imaging (MRI). MEG localizations of the neurons firing at early latencies in primary sensory cortex after separate stimulation of median nerve, thumb and little fingers of each hand were carried out. Characteristics of cerebral equivalent current dipoles (ECDs) activated by each contralateral stimulation, the 'hand extension' (i.e., the distance in millimetres between ECDs of first and fifth digits), as well as interhemispheric differences of the tested parameters were investigated. Finally, ECDs' locations were integrated with MRI. Lesions involving cortical (C) or subcortical (s.c.) areas receiving sensory input from the hand were often combined to increase interhemispheric asymmetry of the tested parameters (22% for C and 49% for s.c. lesions). This might be due to an activation of neuronal districts which in the affected hemisphere (AH) differ from those normally activated in the unaffected hemisphere (UH) and in the control population. Moreover, the 'hand extension' was enlarged on the AH--more frequently after a SC lesion--mainly due to a medial shift of the little finger ECD, combined to a tendency of both finger ECDs to shift frontally. After a C lesion, responses from the AH were often stronger than normal. Spatial reorganizations were also seen in the UH (7% of C and 14% of SC lesions). 'Hand extension' in the UH was selectively enlarged for the P30m only when combined with a similar enlargement in the AH. Significant interhemispheric asymmetries due to neuronal reorganization in the AH were associated with worse clinical outcomes compared to patients without asymmetries.

Adult↗