Biomedical subjects

M Oliveri

Publications and source records attributed to M Oliveri.

At least 19 recordsLinked to original sources

PubMed2003

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.

Adult↗

PubMed2003

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.

Aged↗

PubMed2003

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.

Adult↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Aged↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Brain Mapping↗

PubMed2001

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.

Apoptosis↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Adolescent↗

PubMed2000

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.

Adult↗

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↗