Biomedical subjects

Paolo Maria Rossini

Publications and source records attributed to Paolo Maria Rossini.

At least 19 recordsLinked to original sources

PubMed2007

Event-related power modulations of brain activity preceding visually guided saccades.

To analyze the characteristics of the event-related desynchronization (ERD) and synchronization (ERS) of cortical rhythms during the preparation and execution of a lateralized eye movement, EEG was recorded in normal subjects during a visually guided task. Alpha and beta bands were investigated in three temporal intervals: a sensory period, a delay period and a saccade preparation period time locked with saccade onset. Modulations of ERD/ERS power, coupled with the task, reached the largest amplitudes over the frontal and parieto-occipital regions. Differences of oscillatory activity in the alpha bands revealed an intriguing pattern of asymmetry in parieto-occipital areas. Rightward saccades induced a larger desynchronization with respect to the leftward saccades in the left hemisphere, but not in the right. If representative, these findings are congruent to the established right-hemisphere dominance of the brain areas that direct attention. Moreover differences between the two alpha types emerged in the frontal areas before and during the saccade preparation periods, indicative of differential engagement of these areas depending on the task demands. In conclusion, the present approach shows that planning eye movements is linked with covert orienting of spatial attention and may supply a useful method for studying eye movements and selective attention-related processes.

Adult↗

PubMed2007

Cortical brain responses during passive nonpainful median nerve stimulation at low frequencies (0.5-4 Hz): an fMRI study.

Previous findings have shown that the human somatosensory cortical systems that are activated by passive nonpainful electrical stimulation include the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), and bilateral insula. The present study tested the hypothesis that these areas have different sensitivities to stimulation frequency in the condition of passive stimulation. Functional MRI (fMRI) was recorded in 24 normal volunteers during nonpainful electrical median nerve stimulations at 0.5, 1, 2, and 4 Hz repetition rates in separate recording blocks in pseudorandom order. Results of the blood oxygen level-dependent (BOLD) effect showed that the contralateral SI, the bilateral SII, and the bilateral insula were active during these stimulations. As a major finding, only the contralateral SI increased its activation with the increase of the stimulus frequency at the mentioned range. The fact that nonpainful median-nerve electrical stimuli at 4 Hz induces a larger BOLD response is of interest both for basic research and clinical applications in subjects unable to perform cognitive tasks in the fMRI scanner.

Adult↗

PubMed2006

Temporal dynamics of plastic changes in human primary somatosensory cortex after finger webbing.

The primary somatosensory cortex (SI) exhibits a detailed topographic organization of the hand and fingers, which has been found to undergo plastic changes following modifications of the sensory input. Although the spatial properties of these changes have been extensively investigated, little is known about their temporal dynamics. In this study, we adapted the paradigm of finger webbing, in which 4 fingers are temporarily webbed together, hence modifying their sensory feedback. We used magnetoencephalography, to measure changes in the hand representation in SI, before, during, and after finger webbing for about 5 h. Our results showed a decrease in the Euclidean distance (ED) between cortical sources activated by electrical stimuli to the index and small finger 30 min after webbing, followed by an increase lasting for about 2 h after webbing, which was followed by a return toward baseline values. These results provide a unique frame in which the different representational changes occur, merging previous findings that were only apparently controversial, in which either increases or decreases in ED were reported after sensory manipulation for relatively long or short duration, respectively. Moreover, these observations further confirm that the mechanisms that underlie cortical reorganization are extremely rapid in their expression and, for the first time, show how brain reorganization occurs over time.

Adult↗

PubMed2006

Directional information flows between brain hemispheres during presleep wake and early sleep stages.

Neuroscientists' efforts to better understand the underlying processes of human consciousness are growing in a variety of multidisciplinary approaches. Relevant within these are the studies aimed at exploring the physiological substratum of the propagation and reduction of cerebral-namely, corticocortical-communication flows. However, the preferential direction of the information flow between brain hemispheres is as yet largely unknown. It is the aim of the present research to study the communication flows between brain hemispheres, their directionality, and their regional variations across wake-sleep states. A second aim is to investigate the possibility of an association between different brain rhythms and different preferred directions of the information flow. Scalp electroencephalograms (EEGs) were recorded in 10 normal volunteers from wakefulness to early sleep stages (viz., resting wakefulness, sleep stages 2 and 4, and rapid eye movement [REM] of the first sleep cycle). EEG rhythms of interest were delta (1-4 Hz), theta (5-7 Hz), alpha (8-11 Hz), sigma (12-15 Hz), and beta (16-30 Hz). The direction of the interhemispheric information flow was evaluated by computing directed transformation function from these EEG rhythms. Interhemispheric directional flows varied as a function of the state of consciousness (wake and early sleep stages) and in relation to different cerebral areas. Across wake to sleep states, we found that delta and beta rhythms convey interhemispheric signals with opposite directions: preferred right to left hemisphere direction for delta and left to right for beta rhythms. A log correlation confirmed that the trend of low to high EEG frequencies-traditionally associated with an increasing state of vigilance-was significantly related to the direction of the communication flow from the left to right hemisphere. This evidence might open the way for a variety of research lines on different psychophysiological and pathological conditions.

Adult↗

PubMed2006

Modulation of corticospinal excitability by paired associative stimulation: reproducibility of effects and intraindividual reliability.

OBJECTIVE: Electrical stimulation of the median nerve followed by a magnetic pulse on the primary motor cortex (M1) is effective to cause an increase in the amplitude of motor evoked potential (MEP) registered in the target muscle with the interstimulus interval (ISI) at 25ms (paired associative stimulation, PAS). The aim of this study is to evaluate the reproducibility of PAS with ISI 25 (PAS25), assessed in two separate sessions. Intraindividual reliability of TMS measures was also evaluated. METHODS: Motor threshold of abductor pollicis brevis (APB), assessed at rest, and MEP amplitude of APB and abductor digiti minimi (ADM) were assessed before and after PAS25 in 18 healthy volunteers (nine males and nine females). RESULTS: Data showed a significant increase of MEP amplitude in the target muscle (APB) after PAS25 and a reproducibility of group effect in the two sessions, as assessed by ANOVA, but a lack of intraindividual reliability, as assessed by intraclass correlation coefficients (ICC). CONCLUSIONS: The results underline the reproducibility of mean effects and the need to be careful when comparing the same subject on different days. SIGNIFICANCE: Electrical stimulation of the median nerve followed by a magnetic pulse delivered on M1 after 25ms causes a reproducible increase in MEP amplitude, without showing an acceptable intraindividual reliability.

Abducens Nerve↗

PubMed2006

Human ventral parietal cortex plays a functional role on visuospatial attention and primary consciousness. A repetitive transcranial magnetic stimulation study.

In this paper, we used repetitive transcranial magnetic stimulation (rTMS) in 18 normal subjects to investigate whether the ventral posterior parietal cortex (PPC) plays a causal role on visuospatial attention and primary consciousness and whether these 2 functions are linearly correlated with each other. Two distinct experimental conditions involved a similar visual stimuli recognition paradigm. In "Consciousness" experiment, number of consciously perceived visual stimuli was lower by about 10% after rTMS (300 ms, 20 Hz, motor threshold intensity) on left or right PPC than after sham (pseudo) rTMS. In "Attentional" Posner's experiment, these stimuli were always consciously perceived. Compared with sham condition, parietal rTMS slowed of about 25 ms reaction time to go stimuli, thus disclosing effects on endogenous covert spatial attention. No linear correlation was observed between the rTMS-induced impairment on attention and conscious perception. Results suggest that PPC plays a slight but significant causal role in both visuospatial attention and primary consciousness. Furthermore, these high-level cognitive functions, as modulated by parietal rTMS, do not seem to share either linear or simple relationships.

Adult↗

PubMed2006

Brain plasticity in recovery from stroke: an MEG assessment.

The aim of this paper was to deepen understanding about the role played by brain plasticity in obtaining clinical recovery. Eighteen patients, who had recovered partially or totally from dysfunctions due to a monohemispheric infarction within the middle cerebral artery territory, underwent magnetoencephalographic (MEG) recordings of rolandic areas cerebral activity both in rest state (spectral power properties) and in response to the electrical stimulation of the contralateral median nerve (M20 and M30 cortical sources). MEG evaluation was performed in acute (T0: mean 5 days from ischemic attach) and post-acute phase (T1: median 6 months). At T1, all the inter-hemispheric asymmetries were reduced for both spontaneous and evoked activity parameters with respect to T0. In post-acute phase, lower cortical excitability, higher delta and theta power and lower spectral entropy were associated to a worse clinical state. An unusual recruitment-as revealed by an excessive inter-hemispheric asymmetry of M20 cortical source position-correlated with higher level of clinical amelioration in the patients who showed a partial recovery. In addition to confirmative evidence that "normalization" of neural activity in both the affected and unaffected hemispheres subtends best clinical recovery, present data provide support to the positive role of cerebral plasticity phenomena--i.e. unusual neural recruitments--to regain lost functions in those patients unable to achieve total recovery.

Adult↗

PubMed2006

Hemoglobin oxygen saturation as a marker of cerebral hemodynamics in carotid artery occlusion: an integrated transcranial doppler and near-infrared spectroscopy study.

Cerebral hemodynamics play a pivotal role in stroke pathogenesis. Transcranial Doppler (TCD) studies demonstrated the importance of cerebral vasomotor reactivity (VMR) on the outcome of carotid artery occlusion (CAO). So far, positron emission tomography represents the best technique for detecting both hemodynamic and metabolic aspects of cerebral perfusion adaptive processes in cerebrovascular patients. Near-infrared spectroscopy (NIRS) is a new method allowing for a non-invasive assessment of cerebral blood flow and hemoglobin (Hb) oxygenation parameters.A recent TCD and NIRS study demonstrated that patients with symptomatic CAO had lower VMR values measured by TCD and lower oxygen saturation (oxygen%) increases detected by NIRS than asymptomatic ones. The parameters were obtained simultaneously after CO(2) inhalation. The present study aims to investigate if Hb oxygen % could represent also at rest a marker of hemodynamic status in carotid disease.Thirty-five symptomatic and 17 asymptomatic patients with CAO underwent a simultaneous examination by means of TCD and NIRS at rest condition and during CO(2) reactivity test. Symptomatic patients presented with oxygen% values at rest higher (p = 0.001) and VMR values lower (p < 0.001) than asymptomatic subjects. According to a logistic model, for each unitary VMR increase, the odds of being symptomatic decreases of about 10% (OR = 0.9, p = 0.001); for each unitary increase of oxygen% at baseline, this odd increases of about 23% (OR = 1.23, p = 0.031). In addition to TCD VMR values, oxygen hemoglobin saturation at rest detected by NIRS can discriminate symptomatic from asymptomatic patients with CAO. NIRS can add an important contribution to explain pathophysiological mechanisms of stroke occurrence.

Aged↗

PubMed2006

Fetal auditory responses to external sounds and mother's heart beat: detection improved by Independent Component Analysis.

In this paper, we present a magnetoencephalographic study of the fetal auditory response to external stimuli and to the sound of the mother's heartbeat. We describe how an ad hoc functional selection procedure allowed us to isolate the sources in the fetal brain responding to sounds only, after the application to the recorded data of a standard Independent Component Analysis algorithm. In our experiment, acoustic stimuli were delivered to twelve healthy women with uncomplicated pregnancies at a time between 36 and 40 weeks gestational age, with their fetuses in breech presentation. Ultrasound images allowed determination of the region over the women's abdomen nearest to the fetal head, over which both the acoustic stimulator and the MEG sensors were subsequently placed. In 8 out of the 12 cases, our analysis provided consistent evidence of a fetal response both to the mother's heartbeat and to the external auditory stimulation; both were characterized by a clear prominent component at around 200 ms latency, which is widely accepted as the marker of the fetal response to auditory stimuli.

Acoustic Stimulation↗

PubMed2006

The role of prefrontal cortex in visuo-spatial planning: A repetitive TMS study.

The visuo-spatial planning process is based on an "opportunistic" combination of heuristics and strategies, carried out in small units during the execution of plans. In order to investigate the functional role of the prefrontal cortex in heuristic switching, 42 healthy controls performed a labyrinth crossing task (the Maps Test). During this computerized version of the Travelling Salesperson Problem, subjects had to decide which order of locations optimizes total travel time and distance. This task was performed with and without 1 Hz repetitive transcranial magnetic stimulation (rTMS), which exerts an inhibitory action on the targeted area, applied during the task over bilateral frontal sites (active stimulation) and parieto-occipital site (sham stimulation). Only repetitive bilateral rTMS over F3 and F4 significantly decreased the number of strategies with changes of heuristics, and increased the number of movements required to solve the task. This behaviour contrasts with the performance of healthy subjects in the planning task, but is consistent with the performance of frontal traumatic brain injury patients. The results indicate that, in a visuo-spatial problem-solving task, the prefrontal cortex is involved in the switching between heuristics during the execution of a plan.

Adult↗

PubMed2006

Cortical short-term fatigue effects assessed via rhythmic brain-muscle coherence.

This study is aimed at assessing the short-term effects of muscular fatigue on the sensorimotor areas organization in the left and right hemispheres. Magnetoencephalographic (MEG) and electromyographic (EMG) activities were simultaneously recorded during the execution of a non-fatiguing motor task, performed before and after a task known to induce muscle fatigue (Fatigue). Coherence between cerebral and muscular rhythms as well as cerebral and muscular rhythms spectral densities were estimated during this non-fatiguing task and at rest. The MEG-EMG coherence in the beta band (13-32 Hz) was higher after than before Fatigue. The background activity reduction during contraction with respect to rest (i.e. the cerebral reactivity) was less evident after than before Fatigue in the gamma (33-45 Hz) and beta bands. When differentiating subjects on the base of Fatigue endurance times, while a huge inter-subject variability was found, an evident intra-subject similarity was observed for left and right arms, suggesting that resistance to fatigue is more an individual ability than a motor skill differentiated for the dominant and non-dominant side. In conclusion, signs of a more selective neural recruitment, more coupled with muscular activity, appeared as short-term effects of muscular fatigue in primary sensorimotor cortical areas. Evidence suggested that the reduction of cortical recruitment and the increased cortico-muscular coupling are distinct mechanisms.

Adult↗

PubMed2006

Distraction affects frontal alpha rhythms related to expectancy of pain: an EEG study.

Previous electroencephalographic (EEG) evidence has shown event-related desynchronization (ERD) of alpha rhythms before predictable painful stimuli, as a possible neural concomitant of attentional preparatory processes (Babiloni, C., Brancucci, A., Babiloni, F., Capotosto, P., Carducci, F., Cincotti, F., Arendt-Nielsen, L., Chen, A.C., Rossini, P.M., 2003. Anticipatory cortical responses during the expectancy of a predictable painful stimulation. A high-resolution electroencephalography study. Eur. J. Neurosci. 18 (6) 1692-700). This study tested the hypothesis that alpha ERD before predictable painful stimuli is reduced as an effect of distraction. A visual warning stimulus preceded a laser painful stimulation, which was strictly followed by visual imperative stimuli. In the Pain (control) condition, no task was required after the imperative stimuli. In the Pain + Movement condition, subjects had to perform a movement of the right index finger. In the Pain + Cognition condition, they had to mentally perform an arithmetical task. EEG data were recorded in 10 subjects from 30 electrodes. Artifact-free recordings were spatially enhanced by surface Laplacian transformation. Alpha ERD was computed at three alpha sub-bands according to subjects' individual alpha frequency peak (i.e., about 6-8 Hz, 8-10 Hz, 10-12 Hz). Compared to the control condition, the subjects reported a significantly lower stimulus intensity perception and unpleasantness in the Pain + Movement and Pain + Cognition conditions. In addition, there was a cancellation of the alpha 3 ERD (i.e., about 10-12 Hz) in Pain + Cognition condition and even a generation of a statistically significant alpha 3 ERS in Pain + Movement condition. These effects were maximum over fronto-central midline. These results suggest that distraction during the expectancy of pain is related to a reduced neural desynchronization of fronto-central midline alpha rhythms (i.e., reduced cortical activation) towards an overt hyper-synchronization (cortical idling).

Adult↗

PubMed2006

Effect of repetitive transcranial magnetic stimulation on serum brain derived neurotrophic factor in drug resistant depressed patients.

BACKGROUND: Depression has been associated with low brain-derived neurotrophic factor (BDNF) serum levels, while antidepressant drugs appear to mend this alteration. The purpose of this study was to assess BDNF serum levels in drug resistant depressed patients before and after repetitive Transcranial Magnetic Stimulation (rTMS) antidepressant treatment. METHODS: BDNF levels were measured in serum of 16 resistant depressed patients using the ELISA technique. RESULTS: BDNF baseline levels showed a negative correlation with illness severity measured by HDRS scores (R = -0.517, p = 0.04) and a significant increase of serum BDNF was found after rTMS treatment (t = -2.549, df = 15, p = 0.022). CONCLUSIONS: Our findings support the relationship between decreased serum BDNF and depression symptomatology and suggest a normalizing effect of rTMS antidepressant treatment. Further replications in larger samples will help to clarify the relevance of this preliminary data in the rTMS mechanism of action.

Adult↗

PubMed2006

Mobile phone emissions and human brain excitability.

OBJECTIVE: To test-via Transcranial Magnetic Stimulation (TMS)-the excitability of each brain hemisphere after 'real' or 'sham' exposure to the electromagnetic field (EMF) generated by a mobile phone operating in the Global System for Mobile Communication (GSM). METHODS: Fifteen male volunteers attended two experimental sessions, one week apart, in a cross-over, double-blind paradigm. In one session the signal was turned ON (EMF-on, real exposure), in the other it was turned OFF (EMF-off, sham exposure), for 45 minutes. Motor Evoked Potentials (MEPs) were recorded using a paired-pulse paradigm (testing intracortical excitability with 1 to 17 ms interstimulus intervals), both before and at different times after exposure to the EMF. Short Intracortical Inhibition (SICI) and Facilitation (ICF) curves were evaluated both on the exposed and non-exposed hemispheres. Tympanic temperature was collected during each session. RESULTS: The intracortical excitability curve becomes significantly modified during real exposure, with SICI being reduced and ICF enhanced in the acutely exposed brain hemisphere as compared to the contralateral, non-exposed hemisphere or to sham exposure. Tympanic temperature showed no significant main effect or interactions. INTERPRETATION: These results demonstrate that GSM-EMFs modify brain excitability. Possible implications and applications are discussed.

Adult↗

PubMed2006

Use of an Italian version of the telephone interview for cognitive status in Alzheimer's disease.

OBJECTIVES: Validation of an Italian version of the Telephone Interview for Cognitive Status (I-TICS). METHODS: Telephone administration of the I-TICS within 6 weeks of face-to-face testing with the Mini Mental State Examination (MMSE), in Probable Alzheimer's disease (AD) patients and healthy controls. Two hundred and seven consecutive outpatients with cognitive impairment were recruited from Dementia Clinic of University Campus BioMedico. Of these, 45 probable AD patients with complete data were analyzed. Other dementias, Mild Cognitive Impairment (MCI), and patients with incomplete data were excluded. The control sample consisted of 64 age- and sex-matched healthy subjects. For diagnosis, an extensive clinical evaluation, laboratory testing, brain imaging, EEG, neuropsychological battery and a depression scale were used. For I-TICS validation, telephone I-TICS and face-to-face MMSE were administered. RESULTS: The I-TICS correlated highly and linearly with the MMSE (Pearson's r=0.904). Conversion equations are provided. Sensitivity and specificity were similar between tests (area under curve=0.894 for the I-TICS; 0.966 for the MMSE). I-TICS sensitivity was 84% and specificity 86% at a cut-off score of 28. No significant difference in accuracy with the MMSE was present. Total agreement between I-TICS and MMSE was 'substantial' at 86% (Cohen's K=0.717). Repeated testing in a subset of patients showed a disease progression related decrease of 4.2 points/year (t=2.664; p=0.018) in I-TICS scores. CONCLUSION: The I-TICS is a valid instrument in clinical and research screening and monitoring of AD. Potential applications in other dementias and MCI are worth further studies.

Aged↗

PubMed2006

Functional source separation from magnetoencephalographic signals.

We propose a novel cerebral source extraction method (functional source separation, FSS) starting from extra-cephalic magnetoencephalographic (MEG) signals in humans. It is obtained by adding a functional constraint to the cost function of a basic independent component analysis (ICA) model, defined according to the specific experiment under study, and removing the orthogonality constraint, (i.e., in a single-unit approach, skipping decorrelation of each new component from the subspace generated by the components already found). Source activity was obtained all along processing of a simple separate sensory stimulation of thumb, little finger, and median nerve. Being the sources obtained one by one in each stage applying different criteria, the a posteriori "interesting sources selection" step is avoided. The obtained solutions were in agreement with the homuncular organization in all subjects, neurophysiologically reacting properly and with negligible residual activity. On this basis, the separated sources were interpreted as satisfactorily describing highly superimposed and interconnected neural networks devoted to cortical finger representation. The proposed procedure significantly improves the quality of the extraction with respect to a standard BSS algorithm. Moreover, it is very flexible in including different functional constraints, providing a promising tool to identify neuronal networks in very general cerebral processing.

Adult↗

PubMed2006

Somatosensory evoked potentials of inferior alveolar nerve.

PURPOSE: The use of inferior alveolar nerve somatosensory evoked potentials may represent an objective means of evaluating sensory nerve function in the maxillofacial region. The aim of this work was to confirm the existence of a standard sequence of prominent events in the trigeminal somatosensory evoked potentials (TSEPs) of inferior alveolar nerve (IAN) waveform, examine those components and their normal variability by statistical analysis, and discuss TSEPs' nervous origin and some patterns of TSEPs' abnormalities due to dysfunctional nerves. MATERIALS AND METHODS: TSEPs were obtained following electrical stimulation (square wave pulses 0.2 millisecond [ms] in duration, 4 to 6.5 mA, 0.7/second repetition rate, 200 averages) of the gum at the mental foramen level via intraoral surface electrodes and recorded from the contralateral central scalp sites. RESULTS: We successfully recognized steady waveforms of sufficient quality and consistently recorded a "W"-shaped response: latency onset and peak of the initial deflection of positive polarity were approximately 12 ms and 20 ms, respectively. Negative and positive deflections followed with respective peak latencies at around 26 ms and 36 ms. One side of the lower lip can be compared with the contralateral side and patients may serve as their own control in cases of unilateral nerve injury. The anaesthetic block showed the total abolition of responses. Reproducible TSEP waveform was only obtained during nerve stimulation and not during masseter muscle stimulation. CONCLUSIONS: TSEPs, obtained with the present technique, may represent an objective, low-invasive, and reliable way of testing sensory nerve function in the maxillofacial region.

Adolescent↗

PubMed2006

Anticipatory electroencephalography alpha rhythm predicts subjective perception of pain intensity.

UNLABELLED: This high-resolution electroencephalography (EEG) study tested the hypothesis that the suppression of rolandic alpha power before predictable painful stimulation affects the subject's subsequent evaluation of pain intensity, as a reflection of the influence of expectancy processes on painful stimulus processing. High-resolution EEG data were recorded (126 channels) from 10 healthy adult volunteers during the expectancy of a painful CO(2)-laser stimulation at the right wrist. Surface laplacian estimation enhanced the EEG spatial information content over 6 scalp regions of interest (left frontal, right frontal, left central, right central, left parietal, and right parietal areas). Spectral power was computed for 3 alpha sub-bands with reference to the individual alpha frequency peak (about 5-7 Hz for alpha 1, 7-9 Hz for alpha 2, and 9-11 Hz for alpha 3). The suppression of the alpha power before the painful stimulation [as reflected by the event-related desynchronization (ERD)] indexed the anticipatory cortical processes. Results showed maximum (negative) correlations between the alpha 2 and alpha 3 ERD amplitude at the left central area and the subjective evaluation of pain intensity (P < .001). The stronger the anticipatory alpha 2 and alpha 3 ERD, the higher the subjective evaluation of pain intensity. For alpha 3, that correlation was confirmed even when the effect of habituation across the recording session was taken into account. These results suggest that the anticipatory suppression of the alpha rhythms over the contralateral primary sensorimotor cortex predicts subsequent subjects' evaluation of pain intensity, in line with its crucial role for the discrimination of that intensity. PERSPECTIVE: This electroencephalographic study showed that anticipatory activation/deactivation of sensorimotor cortex roughly predicts subjective evaluation of pain. This motivates further investigation on possible implications for the understanding of central chronic pain. Chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli.

Adult↗