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F Ferlazzo

Publications and source records attributed to F Ferlazzo.

17 recordsLinked to original sources
PubMed2001

Auditory evoked responses upon awakening from sleep in human subjects.

The hypothesis that a state of hypoarousal upon awakening should lead to a decrease in amplitude and an increase in latency of the N1-P2 components of the Auditory Evoked Potentials (AEPs) as compared to presleep wakefulness levels, was evaluated after two nocturnal awakenings and after the final morning awakening from a 7.5-h night of sleep. The amplitude of the N1-P2 complex was reduced upon awakening as compared to presleep wakefulness levels, but only following the first nocturnal awakening, scheduled after the first 2 h of sleep. This result is interpreted as indicating a link between slow wave sleep amount, mainly present during the first part of the night, and lowered levels of brain activation upon awakening. The reaction times, recorded concomitantly to AEPs, were more sensitive to the negative effects of sleep inertia.

Adult↗
PubMed2001

Upper/lower visual field asymmetry on a spatial relocation memory task.

The purpose of this study was to investigate whether the lower visual field advantage reported on a number of visual tasks depends on the activity of neural systems which process information from different spaces. To this end, a double dissociation logic was followed by observing the effects of visual and spatial interference on a relocation memory task performed by 80 volunteers. Results showed that participants were better at relocating stimuli presented in the lower than in the upper visual field. Moreover, a concurrent spatial task, but not a concurrent visual task, disrupted the visual field vertical asymmetry. Those findings confirm that the vertical asymmetry of visual field depends on the spatial processing of incoming stimuli.

Adult↗
PubMed2001

G theory and the reliability of psychophysiological measures: a tutorial.

For some years, the limits of classic reliability theory have been recognized in favor of the Generalizability Theory, which deals simultaneously with multiple sources of error. This measurement model can be particularly useful when applied to research in cognitive psychophysiology. Indeed, studies in this field often deal with estimated measures whose reliability is rarely taken into account. In this paper, we report two generalizability studies in order to investigate the usefulness of G theory in providing information about the reliability of experimental results. The first was carried out on P300 measured during an oddball task, and the second was carried out on ERPs recorded during a recognition memory task. As expected, results showed that P300 modulation was more reliable than ERP memory modulation. This suggests that G theory can be a useful tool to estimate the reliability of psychophysiological findings, complementing and extending results from conventional analyses.

Acoustic Stimulation↗
PubMed2000

Slow eye movements and EEG power spectra during wake-sleep transition.

OBJECTIVE: The aim of the present study was to assess the relationship between slow eye movements (SEMs) and quantitative EEG measures during the wake-sleep transition. METHODS: Individual distributions were aligned with respect to the onset of stage 2 to provide an unequivocal hallmark of the beginning of sleep and to reduce the sources of variability in this transition. The relationship between EEG spectral powers and EOG changes was assessed by means of product-moment correlations and bootstrap analyses for individual time series, and by means of a multiple regression analysis for the entire sample. RESULTS: Results on the individual distributions as well as on averaged data showed a tight relationship between SEMs and EEG changes, negative across the 1-14 Hz frequency range and positive across the 15-30 Hz one. Spectral power in the sigma EEG band, that corresponds to the frequency at the phasic sleep spindles, resulted as the best predictor of SEM variations, being negatively correlated to the EOG changes. With respect to the other EEG frequency bands, the split half of the distributions with respect to stage 2 onset indicated a positive correlation of delta power with the increase of SEM activity before sleep onset, and of beta power with the decrease of SEMs after sleep onset. CONCLUSIONS: These results seem to suggest that sleep spindles could trigger the reduction and the final disappearance of slow eye movements in the late part of the wake-sleep transition.

Adult↗
PubMed2000

Resampling approach to statistical inference: bootstrapping from event-related potentials data.

We propose the use of the bootstrap resampling technique as a tool to assess the within-subject reliability of experimental modulation effects on event-related potentials (ERPs). The assessment of the within-subject reliability is relevant in all those cases when the subject score is obtained by some estimation procedure, such as averaging. In these cases, possible deviations from the assumptions on which the estimation procedure relies may lead to severely biased results and, consequently, to incorrect functional inferences. In this study, we applied bootstrap analysis to data from an experiment aimed at investigating the relationship between ERPs and memory processes. ERPs were recorded from two groups of subjects engaged in a recognition memory task. During the study phase, subjects in Group A were required to make an orthographic judgment on 160 visually presented words, whereas subjects in Group B were only required to pay attention to the words. During the test phase all subjects were presented with the 160 previously studied words along with 160 new words and were required to decide whether the current word was "old" or "new." To assess the effect of word imagery value, half of the words had a high imagery value and half a low imagery value. Analyses of variance performed on ERPs showed that an imagery-induced modulation of the old/new effect was evident only for subjects who were not engaged in the orthographic task during the study phase. This result supports the hypothesis that this modulation is due to some aspect of the recognition memory process and not to the stimulus encoding operations that occur during the recognition memory task. However, bootstrap analysis on the same data showed that the old/new effect on ERPs was not reliable for all the subjects. This result suggests that only a cautious inference can be made from these data.

Adult↗
PubMed1995

Ultradian rhythms in the N1-P2 amplitude of the visual evoked potential in two inbred strains of mice: DBA/2J and C57BL/6.

Ultradian rhythmicity has been showed in many behavioural parameters in animals as well as in humans. We investigated the existence of a Basic Rest-Activity Cycle (BRAC) rhythm in amplitude fluctuations of mice's visual evoked potential (VEP) primary component. Two inbred strains of mice, C57BL/6 and DBA/2J, were used to verify the influence of genetics on biological rhythm as well. Results revealed the existence of an evident rhythm in the parameter under study and confirm previous reports of a 20 min. BRAC in avoidance behavior in DBA mice. This rhythm shows similar period within each strain, but significatively different periods between strains. Observed periods are near to species-specific reported BRAC cycle. Genetic hypothesys is suggested to explain differences between strains in expression of ultradian rhythm.

Animals↗
PubMed1995

Ultradian rhythms of reaction times in performance in vigilance tasks.

This study examined the presence of rhythmic fluctuations in vigilance tasks. The hypothesis was that individual attentional performance is subject to rhythmic variation beyond a linear decrease over time. In the first study the reaction times to an acoustic stimulus were recorded. The analysis of the individual periodograms indicated a rhythm in attentional capacity with periods ranging from 5 to 30 min. These findings indicate that considerable individual variation can be accounted for by considering individual periodicity in performance. Although marked individual differences between subjects are present, the rhythmic fluctuations are stable within each subject and between experimental sessions.

Activity Cycles↗
PubMed1995

Rhythmic variations in reaction times and evoked potentials.

The present work aimed to assess the existence of a regular ultradian cyclicity underlying the variations in amplitude of the N1-P2 component of acoustic EP during a relatively long recording session and investigate its relationship with behavioral measure as RT to the same stimulus. 128 tones were presented to each subject; 128 RTs and the associated EPs to target stimuli were recorded. N1-P2 amplitude has been measured at a single trial level through Woody adaptive filter modified by Wastell. Results showed that there are ultradian rhythmic variations of N1-P2 and RT, with a periodicity from about 5 to 40 min and these variations have similar patterns in the two measures in most of the subjects.

Activity Cycles↗
PubMed1994

Ultradian rhythms in avoidance behavior of DBA mice.

This study investigates ultradian rhythm in avoidance behavior of mice, which may constitute a basic rest activity cycle (BRAC). Reaction times (RTs) of an avoidance response to a visual warning stimulus that preceded an electric shock were measured by the use of a computer-controlled shuttle box. The male naive DBA mice were brought to a criterion of 98% correct responses in numerous training sessions. For each subject, all the temporal sequences of the RTs in the trials following achievement of the criterion were examined with discrete Fourier transform. Periodograms were obtained from three sessions for each of the two animals in the first experiment and from 15 subjects in the second experiment. Analysis of the periodograms reveals a stable rhythm in avoidance behavior of mice, with a period of about 14 min. The presence of these periodicities could show the existence, also in small rodents, of a BRAC rhythm.

Activity Cycles↗
PubMed1993

Event-related potentials and recognition memory: the effects of word imagery value.

Event-related potentials (ERPs) were recorded from 11 subjects during a recognition memory task. Subjects were auditorily presented with 160 target words and, after about 10 min, they were engaged in a recognition task. Subjects were required to determine on each of 320 trials if the word was 'new' (never before presented) or 'old' (heard previously). In the recognition test, 160 target words and 160 non-target words were used as stimuli. To assess the effect of word imagery value, 160 stimuli (80 target and 80 non-target) were high imagery words (HI) and the remaining 160 stimuli were low imagery words (LI). Word frequency was balanced across target and non-target words. Results showed that the old/new effect was reflected by a negative component (belonging to the N400 family, Cz maximum) which was larger for new words in the 400-700 ms range. The imagery effect was also present in the 250-550 ms range of the N400, which was larger for HI stimuli. The imagery effect was present at 400-550 ms only for target words. These results confirmed the hypothesis that negative components as N400, could reflect processes occurring during the memory retrieval of items.

Adult↗
PubMed1993

Event-related potentials and recognition memory within the 'levels of processing' framework.

Event-related potentials (ERPs) were recorded from nine subjects during an incidental memory paradigm. During the study phase subjects were engaged in two tasks requiring semantic and rhyming decisions. During the test phase, subjects were required to decide on each of 320 trials if the word was 'new' (never before presented) or 'old' (seen previously). Results showed that semantic old words were more often recognized than rhyming ones. ERPs to new words were more negative than ERPs to old words in the 400-800 latency range. ERPs to semantic old words were more positive than ERPs to rhyming ones in the same latency range. The difference between ERPs to semantic and rhyming old words confirms a relationship between ERPs and memory.

Adult↗
PubMed1980

[Experimental research on the effect of electro-acupuncture on reparative processes].

With a view to clarifying the mechanism whereby electroacupuncture aids teh repair of trophic ulcers, including inveterate forms resistant to ordinary treatments, reference is made to histochemical findings and histological findings in periulcerous tissues and experimental research into wound healing. Preliminary work showed that electroacupuncture improves the blood supply to ulcerous tissue and the local biochemistry, and accelerates the repair process. Experimental work also made it clear that the method, when use on alternate days with the modalities employed in clinical practice, accelerates the healing of wounds in the experimental animal.

Acupuncture Therapy↗
PubMed1980

[Electro-acupuncture and trophic ulcer].

Electroacupuncture was used in the treatment of 50 cases of tropic ulcer of the lower extremities, including 34 following phlebitis, by stimulation with a Roccia VTM apparatus at voltages and frequencies up to the patient's tolerance threshold. The needles stimulation was maintained for a maximum of 7 hr. A cure was obtained in all cases, including those where the ulcers were inveterate and resistant to routine forms of management.

Acupuncture Therapy↗
PubMedDate not supplied

Rhythmic variations of P100 component of pattern-reversal visual evoked potentials.

Pattern-reversal visual evoked potentials (EPs) were recorded in seven adult subjects to assess the existence of rhythmic variations in processing visual information at a primary stage. During a session of two hours, sixty EPs were recorded on the left and right cerebral hemispheres. The amplitude of N75-P100 component was measured. Remarkable variations were found with a periodicity from 15 to 60 min in six out of seven subjects. No hemispheric differences were found in the rhythmic variations. The results are in agreement with the behavioral data which show ultradian variations in visual performance depending on a general activation oscillator.

Activity Cycles↗