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Biomedical subjects

G A Chiarenza

Publications and source records attributed to G A Chiarenza.

At least 19 recordsLinked to original sources
PubMed1994

Analysis of single trial movement-related brain macropotential.

A parametric method of identification of movement-related brain macropotentials on a single trial basis through an ARX (autoregressive with exogenous inputs) algorithm is presented. The basic estimation of the information contained in the single trial is taken from an average carried out on a sufficient number of trials, while the noise sources, EEG and EOG are characterized as exogenous inputs in the model. The simulations as well as the experimental results confirm the capability of the model to drastically improve the signal/noise ratio in each single trial and to satisfactorily identify the contributions of signal and noise in the overall recording. This way, using the same algorithm, a particularly efficient reduction of ocular artifacts is also achieved. The movement-related brain macropotentials recorded in three subjects show a high degree of variability from trial and this effect seems to be related to programming processes and evaluation of errors.

Adult↗
PubMed1994

Development of gestalt-reading processes in children: assessment using the Boder test.

According to Boder, there are two processes involved in reading: visual-gestalt and analytic-phonetic. The gestalt process is activated for known words, forming part of the child's "sight vocabulary", and it enables him/her to recognize words even when they are exposed for a very short time. The analytic-phonetic process involves the auditory channel when the words are not part of the "sight vocabulary" and require a spelling process. At first, neither the English version nor the Italian adaptation of the Boder test included a control of word exposition time (ET) and reading time (RT). Both parameters are necessary for a check of the gestalt and phonetic processes. The aim of this paper was the assessment of minimum ET for the words belonging to the "sight vocabulary" and of RT for a word read through a gestalt process. Seventy-five primary schoolchildren from the first to the fifth class were presented with 100 meaningful words (MF) and 100 meaningless (ML) words, using ETs ranging from 150 to 650 ms. The results showed that, at the age of 7 years, the gestalt process was completely developed. Of MF words, 95% were correctly read and it did not change significantly with longer ETs. The RT for MF words did not change with different ETs and remained stable after the age of 7 years. Finally, the RT for ML words was always longer than the RT for MF words, and the difference was significant in 8-, 9- and 10-year-old children.

Child↗
PubMed1993

Movement-related brain macropotentials of persons with Down syndrome during skilled performance.

Motor performances and movement-related brain macropotentials of nine 23-year-old males with Down syndrome whose mean MA was 10.2 years were compared to those of two control groups whose members were matched to the experimental subjects on CA or MA. A self-paced, voluntary, goal-directed task, which consisted of calculating a time interval of 40 to 60 msec by pressing two buttons, was employed. Subjects with Down syndrome had great difficulty in organizing and timing a correct temporal sequence of ballistic movements. They were much slower, less accurate, and achieved a smaller number of target performances. These behavioral patterns were associated with movement-related brain macropotentials altered in amplitude and latency. The potentials related to programming movements and processing reafferent sensory information were absent, and those involved in the evaluation of the outcome of the performance were reduced.

Adult↗
PubMed1991

Brain activity associated with skilled finger movements: multichannel magnetic recordings.

We recorded with a 24-channel SQUID magnetometer cerebral activity preceding and following self-paced voluntary 'skilled' movements in four healthy adults. The subject pressed buttons successively with the right index and middle fingers aiming at a time difference of 40-60 ms; on-line feedback on performance was given after each movement. Slow magnetic readiness fields (RFs) preceded the movements by 0.5 s and culminated about 20 ms after the electromyogram (EMG) onset. Movement-evoked fields, MEFs, opposite in polarity to RFs, were observed 90-120 ms after the EMG onset. They were followed by an additional 'skilled-performance field', SPF, 400-500 ms after the EMG onset. The source locations of RF, MEF, and SPF were within 2 cm from sources of the somatosensory evoked responses, which were situated in the posterior wall of the Rolandic fissure; the sources of MEF were closest to the midline. Neural generators of these deflections and of the corresponding electric potentials are discussed.

Adult↗
PubMed1991

A critical review of physiological and clinical aspects of movement related brain macropotentials in humans.

The methodological, developmental and clinical aspects of movement related brain macropotentials (MRBMs) are reviewed. The physiological differences between unskilled and skilled movements are described and the importance of interactive paradigms in studying movement organization from childhood to adulthood is emphasized. The developmental characteristics of the MRBMs in 119 normal males using a skilled motor perceptual task are presented together with a few clinical applications. This test has been performed by children with learning disabilities, boys with Down syndrome, subjects with chronic schizophrenia and patients with Parkinson syndrome. The results of the MRBMs are discussed for their relevance for our understanding of the cognitive processes and for their therapeutic implications.

Adult↗
PubMed1991

Developmental course of brain-stem auditory evoked potentials in the first days of full term infants.

Modifications of brain-stem acoustic evoked potentials (BAEPs) in the first 5 days of life of normal full-term infants are reported. BAEPs were recorded using rarefaction clicks at 70, 60, 40, 20 dB HL. Multiple linear regression analysis was performed to evaluate chronological and gestational age differences for all positive and negative peaks, interpeak latencies, amplitudes and amplitude ratios. The percentage of newborn infants with auditory threshold of 20 dB HL increased with the number of days. At all intensities the latency of PIII and PV decreased significantly between the 2nd and 3rd day, while the latency of PI decreased significantly between the 3rd and the 4th day; PIII and PV latencies decreased also between the 4th and the 5th day. The longer the period of gestation the longer was the PI latency recorded between the 2nd and 5th day after birth. The anatomical and physiological changes developing shortly after birth are probably responsible for the above findings. These changes most probably appear firstly in the cochlear and trapezoid nuclei and later on in the organ of Corti.

Age Factors↗
PubMed1990

The acute and chronic administrations of piracetam affect the movement-related brain macropotentials.

Neurophysiological and neurochemical studies have demonstrated that piracetam improves learning and memory both in animals and humans. In recent years it has been shown that when a subject is engaged in a motor perceptual task, some psychomotor functions are correlated with a consistent pattern of brain electrical activity. Given the relationship between the movement-related brain macropotentials (MRBMs) and the cognitive processes associated with them, we considered the MRBMs particularly suitable for the neurophysiological assessment of the efficacy of piracetam in man. The aim of this study was to test the acute and chronic effect of piracetam administration on the MRBMs in normal children during the performance of a motor perceptual task. The design was a triple-blind study, during which the subjects took either placebo or piracetam in random sequence, with a washout period of 3 weeks. The dose was 170 mg/kg for the acute treatment and 140 mg/kg/day for chronic treatment. No side-effects were reported by the children during or after acute or chronic treatment with piracetam. There was no statistically significant difference between placebo or piracetam treatment with regard to 'performance', which was already optimal at baseline, and to electromyographic activity. On the contrary, the MRBMs were significantly modified by treatment. In particular the Bereitschaftspotential was present as a positive shift during acute treatment with piracetam and increased after chronic treatment. Skilled performance positivity (SPP) amplitudes were significantly increased and SPP latency reduced by chronic treatment with piracetam. piracetam appears to act on the catecholaminergic and cholinergic systems via an increase of the inhibitory hyperpolarizing processes.

Adolescent↗
PubMed1990

Goal or near miss! Movement potential differences between adults and children in skilled performance.

In this study, the performances and the movement-related brain macropotentials of a group of adults and 10-year-old children were analyzed to test whether and how they were correlated to the success or failure in the performance. Bereitschaftspotential (BP), motor cortex potential (MCP) and skilled performance positivity (SPP) related to preparation, execution and evaluation of performance respectively showed a significant relationship to the performance outcome. The BP area in the left precentral decreased significantly with increasing performance time. The amplitude of the MCP was maximum during target performances and decreased with increasing range of error of performance. There was a difference in trend between adults and children in the SPP latency. During target performances, SPP latency in Pz was maximum in children and minimum in adults. In children, the SPP amplitude was greater in frontal and precentral areas during target performance and decreased with increasing inaccuracy of performance. This trend was not evident in adults. The results seem to indicate that the SPP latency does not seem to depend on the performance time but on the evaluation of information conveyed by the stimulus. How this evaluation takes place seems to be different in children and adults; this evaluation process is also reflected in the SPP amplitude of children during target performances. For the adults who have already developed formal thinking, the probability that any outcome is possible exists and so the significant relationship between SPP amplitude and performance is not seen.

Adolescent↗
PubMed1990

The skilled performance positivity after learning a skilled task.

The effect of an intensive training period and that of a time-distributed training on skilled performance positivity (SPP) have been studied. SPP is a potential associated with knowledge and evaluation of the results of a goal-directed bimanual self-paced task requiring particular ability. Nine subjects with average intelligence but with some difficulties in the motor-perceptive sphere were studied. The task consisted of initiating the sweep of an oscilloscope with a self-paced movement and terminating it within 50 msec +/- 10 msec. The subjects had to repeat this task several times at various time intervals. The electrical activity was recorded from Fpz, Fz, Cz, Pz, P4, P3 and the right/left precentral areas. For each performance, performance time, performance shift taken as the accuracy index, as well as the percentage of target performances were evaluated. Motor performances improved with both distributed and intensive practice. Only distributed practice had a significant effect on SPP latency and amplitude. SPP latency decreased in all brain areas, whereas amplitude increased in the prefrontal, frontal and left precentral areas. These results seem to suggest that the performance evaluation processes take place more quickly and efficiently through distributed practice.

Adolescent↗
PubMed1986

Electrophysiology of skilled performances in children.

Skilled performance is a result of appropriate integration of sensorimotor, cognitive and motivational functions. When Piaget was asked about the nature of reality and our knowledge of it, he answered: "I know an object only when I can act on it; before this action I cannot say anything about it". It has been proposed that motor actions are the source from which mental operations emerge. The intellectual growth of a child goes through stages during which actions, perceptions and ability for concrete or abstract thought hold in turn a predominant role. On the grounds of this theoretical framework it could be argued that neuropsychophysiological investigations of skilled performance in children which incorporate the study of performance-related brain electrical activity could contribute unique information with theoretical and clinical implications. A pattern of slow and phasic brain electrical activity is consistently associated with the execution of skilled ballistic tasks. The slow potentials of the preparatory period (Bereitschfts Potential-BP) are of low amplitude in low demand tasks and in young children. The potentials closely associated with the execution of the act and reflecting sensory feedback activity (Motor Cortex Potential-MCP) are constantly present in children of all ages. The potential associated with knowledge of results (Skilled Performance Positivity-SPP) is only present if task relevant exteroceptive information is expected and occurs. The SPP is independent of the action itself and of the existence of non-informative exteroceptive stimulation. The SPP is absent in unskilled tasks and in young children. The motor performance related with the execution of the motor act improves with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1985

Neurophysiological correlates of psychomotor activity in chronic schizophrenics.

The movement-related brain macropotentials (MRBMs) of 13 chronic schizophrenics (7 paranoid and 6 hebephrenic) were recorded during a motor perceptual task and compared to those of 13 normal subjects matched by age, sex and IQ. The cerebral activity was recorded from Fpz, Fz, Cz, Pz, and right and left precentral areas and the electromyographic activities from the left and right forearm flexor muscle groups. Analysis of variance was performed to test the correlation between the MRBMs and groups, sets and performances. The results indicate that the performance considered in tests of 'performance time,' as 'performance shift' and as number of 'target performances' was poorer in chronic schizophrenics than it was in the control group. In parallel with the performance, the MRBMs of chronic schizophrenics were also significantly different in comparison to the normal subjects. In particular, the BP amplitude was reduced in all areas; the MCP and P200 were also abnormally reduced. The SPP was present but it had a small amplitude in the parietal region. These differences in chronic schizophrenics could be explained as multidimensional biopsychological deficits: the disturbed performance is the result of impairment in developing appropriate changes of set, defective inhibition of sensory information, and reduced utilization of the outcome data.

Adolescent↗
PubMed1983

Movement-related brain macropotentials during skilled performances. A developmental study.

A developmental study of movement-related brain macropotentials (MRBMs) during a self-paced bimanual skilled performance task (Papakostopoulos 1980) was carried out. MRBMs were obtained from Fpz, Cz and right and left pre-central and electromyograms were recorded from the left and right flexor muscles of the forearms in 30 normal children ranging from 8 to 13 years of age. A consistent Bereitschaftspotential appeared in children of 10 years; in the younger children it was absent or it was positive at precentral and central locations. The motor cortex potential and P200 were present in all children. The skilled performance positivity (SPP), absent at 8 and 9 years, appeared at 11 years of age and was present in older children. The latency of P200 and SPP decreased with age. ANOVA tests showed a statistically significant age effect on performance, EMG rise time and MRBMs; MRBMs were not statistically influenced by time in the experiment: MCP and P200 increased in amplitude with improvement of performance. The results indicate different rates of maturation of the neuronal systems underlying the genesis of the various movement-related brain macropotentials.

Adolescent↗
PubMedDate not supplied

Sex and ear differences of brain-stem acoustic evoked potentials in a sample of normal full-term newborns. Normative study.

The present paper reports a normative study of the BAEPs recorded from 80 normal full-term newborns by using a rarefaction click at 70, 60, 40, 20 dB HL. Positive, negative peaks and the relative amplitudes were measured. Means, standard deviations and 95% and 99% confidence limits were calculated for each component, for positive and negative IPLs and amplitude ratios. A normality test distribution showed that each component had normal distribution except for wave PIII at 70 dB and at 60 dB HL because of its index of kurtosis and for IPLs PII-PIII and NII-NIII at 70 and 60 dB HL. MLRA was performed and significant statistical differences were found for sex, ears and intensities. Females had the latencies of waves PIII, PIV, PV, NII and NIV shorter than males. The BAEPs obtained from the left ear had shorter latencies for positive and negative peaks. Latencies, amplitude and morphology of the BAEPs vary with variations of the intensity. The IPLs PII-PV, PIII-PV and PIV-PV were not affected by changes of intensity.

Auditory Perception↗
PubMedDate not supplied

Motor-perceptual function in children with developmental reading disorders: neuropsychophysiological analysis.

The aim of this paper is to compare the motor performances and the movement-related macropotentials of 8 male children aged 10 years with developmental reading disorders with those of 9 nondisabled male children of the same age. The task employed consisted of initiating the sweep of an oscilloscope with a self-paced movement and terminating it within 50 +/- 10 msec. The children with reading disorders were slower, less accurate, and achieved a smaller number of target performances. Their brain macropotentials associated with motor programming, processing of sensory information, and evaluation of the results were altered in amplitude and latency. In the children with reading disorders, the systems involved in planning strategies and processing of sensory information are inadequate and those involved in the correction of errors are less efficient. Therefore, reading disorders could express defective integration and dysfunction of numerous processes occurring at different levels and times.

Arousal↗