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Biomedical subjects

C Escera

Publications and source records attributed to C Escera.

29 records · Page 2Linked to original sources
PubMed1997

Effects of involuntary auditory attention on visual task performance and brain activity.

Involuntary attention to auditory stimulus changes during a visual discrimination task was studied with event-related potentials (ERPs) recorded from the human scalp. A repetitive standard tone or an infrequent, slightly higher deviant tone preceded each visual target stimulus. Deviant tones elicited the mismatch negativity and P3a ERP components and caused increases in reaction time and error rate in the visual task indicating involuntary attention to an auditory stimulus change. These effects were observed even when the tones occurred simultaneously with a visual warning stimulus introduced to keep attention focused on the visual task. In the latter condition, involuntary switching of attention away from the visual task also attenuated the N1 ERP component to visual target stimuli preceded by the deviant tone.

Acoustic Stimulation↗
PubMed1996

The H1-receptor antagonist chlorpheniramine decreases the ending phase of the mismatch negativity of the human auditory event-related potentials.

Auditory event-related potentials (ERPs) were recorded in 20 healthy male humans, who received either a single 4 mg dose of d-chlorpheniramine or a placebo, according to a double-blind design. Subjects were instructed to read a book and to ignore random sequences of 90% standard (1000 Hz) and 10% deviant (1100 Hz) tones, presented with stimulus-onset asynchrony (SOA) of 480 ms. Deviant tones elicited the mismatch negativity (MMN) response, which was smaller at its ending phase in the chlorpheniramine group. The auditory exogenous components (N1 and P2) were similar in both groups. Results demonstrate that the antihistamine chlorpheniramine selectively affects the automatic stimulus-change detector associated with MMN, and suggest an involvement of the histamine H1-receptor in the genesis of the MMN.

Acoustic Stimulation↗
PubMed1996

Short-term replicability of the mismatch negativity.

The short-term replicability of the mismatch negativity (MMN) between two recording sessions spaced 2 h apart was evaluated at individual and group levels in a sample of 11 healthy adults. Subjects were presented with a random sequence of 1000 Hz standard (92%) and 1100 Hz deviant (8%) tones while they were reading a book. The N1 and P2 exogenous components to standard tones showed a fairly good individual and group replicability. There were no significant differences in the MMN amplitude and latency between the two sessions in the group of subjects as a whole. The individual replicability of the MMN was not as good as for the N1 to standards, reaching significance in only some of the electrodes. This result was, however, similar to that obtained for the N1 after deviant tones. The results indicate that the MMN has good replicability at the group level, and further that at the individual level, MMN replicability is similar to that of the N1 to deviants. This suggests that the number of summations should be increased in order to improve the clinical usefulness of the MMN.

Acoustic Stimulation↗
PubMed1995

Ultradian rhythms in gross motor activity of adult humans.

During waking h, the existence of ultradian rhythms in gross motor activity has been described in nonprimates, nonhuman primates and newborn humans, but not in adult humans. Some of the previous studies suggested that the appearance of these rhythms could be favored by conditions of isolation and low environmental demands. To confirm the existence of ultradian rhythmicity in the gross motor activity of adult humans and to describe their characteristics, an actimeter was used to record the mobility of 13 adults who remained alone and isolated for 5 h (15:00-20:00) in a monotonous environment with nothing to do. Least squares rhythmometry analysis showed that the gross motor activity of 12 out of 13 subjects had significant rhythms (p < 0.05) within the ultradian band, with periods of between 0.5 and 2.5 h. There were important individual differences between the dominant periods and the same subject might show more than one significant period. These rhythms were stable and they tended to appear immediately the experiment began. The results suggest that a philogenetically old mechanism that organizes gross motor activity in ultradian rhythms exists in adult humans.

Activity Cycles↗
PubMed1994

Ultradian rhythms in selective auditory attention performance.

In order to study the existence of ultradian rhythms in human performance, reaction times and omissions of responses to signal stimuli were registered from 17 subjects performing a selective auditory attention task, at 15-minute intervals from 9:00 am to 3:00 pm. The task consisted of selectively focusing attention, first to the left and then to the right ear, and pressing a button every time a signal stimulus was detected. Rhythmometric analysis showed the existence of significant (p < .05) ultradian rhythms both in the temporal course of the reaction time and in the number of omissions of responses to signal stimuli. Results are discussed in terms of the level of difficulty of the task and the processing resources involved.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of ethanol and auditory distraction on forced choice reaction time.

Effects of ethanol (0.55 g/kg) and auditory distraction on visual forced choice reaction time (RT) were investigated in 10 healthy social drinkers, using a single-blind, placebo-controlled, crossover design. Subjects were to respond by pressing a button either with their right-hand index or middle finger, depending on whether an odd or an even digit was presented on a PC screen. In control blocks, the digits were presented alone, whereas in distraction blocks they were shortly preceded by either a frequent "standard" tone of 600 Hz, or an infrequent tone that was either a 660 Hz "deviant" tone or a "novel" sound (e.g., telephone ringing). Alcohol reduced the hit rate by increasing the amount of errors, but had no effect on the RT, thus supporting the previous observations. In the placebo condition, the RT was prolonged by the deviant and novel sounds, and the hit rate was reduced by the deviant tones. During ethanol intoxication, however, the reduction in hit rate caused by the deviant tones was significantly smaller. This suggests that the attention-capturing effects of the deviant sounds were suppressed by ethanol, thus demonstrating a detrimental effect of ethanol on involuntary attention.

Acoustic Stimulation↗
PubMedDate not supplied

Mismatch negativity: clinical and other applications.

The perspectives of application of the mismatch negativity (MMN), generated by the brain's automatic response to change in auditory stimulation, are discussed. In light of the fact that the MMN (and its magnetic equivalent MMNm) currently provides the only objective measure of the accuracy of the central auditory function, these perspectives appear very promising. The MMN can be measured in the absence of attention and task requirements, which makes it particularly suitable for testing different clinical populations and infants. Furthermore, the MMN enables one to evaluate the accuracy of auditory discrimination separately for any acoustic feature, such as frequency, intensity and duration, and for learned categories, such as the phonemes of a particular language. In addition, by measuring the decay of the MMN amplitude as a function of the interstimulus interval, it is possible to estimate the duration of sensory (echoic) memory.

Adult↗
PubMedDate not supplied

Involuntary attention and distractibility as evaluated with event-related brain potentials.

This article reviews recent event-related brain potential (ERP) studies of involuntary attention and distractibility in response to novelty and change in the acoustic environment. These studies show that the mismatch negativity, N(1) and P(3a) ERP components elicited by deviant or novel sounds in an unattended sequence of repetitive stimuli index different processes along the course to involuntary attention switch to distracting stimuli. These studies used new auditory-auditory and auditory-visual distraction paradigms, which enable one to assess objectively abnormal distractibility in several clinical patient groups, such as those suffering from closed-head injuries or chronic alcoholism.

Attention↗
PubMedDate not supplied

Acute and chronic effects of alcohol on preattentive auditory processing as reflected by mismatch negativity.

Chronic alcoholism, a major worldwide health problem, is associated with a variety of neurocognitive changes in the afflicted individuals. The precise neurophysiological basis of these changes is not yet understood. Mismatch negativity (MMN) is a preattentive event-related potential component indexing cortical auditory memory traces and automatic change detection in the brain that can be used to study the neural basis of cognitive impairments in various neurodegenerative diseases. MMN studies have revealed that even a low dose of acute alcohol significantly impairs automatic change detection and involuntary attention shifting. Recent MMN results on chronic alcoholism in turn suggest that auditory sensory traces decay slightly faster and are substantially more vulnerable to the distracting effect of backward masking in alcoholics than in healthy subjects. Furthermore, chronic alcohol abuse might accelerate the age-related impairment of automatic change detection. There is also evidence that the MMN changes might predict impaired performance in behavioral memory and attention tasks in alcoholics. In MMN studies of detoxified alcoholics, however, many confounding factors have to be taken into account. For instance, postwithdrawal brain hyperexcitability might be associated with a slightly enhanced or accelerated MMN/MMNm (the magnetic equivalent of MMN). In sum, MMN and MMNm provide an objective noninvasive tool for exploring the neurophysiological functional deficits related to both acute alcohol intoxication and chronic alcoholism.

Acute Disease↗
PubMedDate not supplied

[The potential P300 in the evaluation of the side effects of dexchlorpheniramine].

INTRODUCTION: The antihistamine chlorpheniramine presents multiple adverse side effects on the central nervous system. In earlier work it has been observed that a dose equal to the one used in this study alters the evoked potentials PN (processing negativity) and MMN (mismatch negativity), which are, respectively, indicators of selective attention and of an automatic mechanism for detecting changes in auditory stimulation. AIMS. The aim of the present study was to evaluate the effects of a single 4 mg dose of dexchlorpheniramine on the evoked potential P300, to enable us to better define its effects on the central nervous system. Subjects and methods. Using the double blind procedure, half a sample consisting in 20 subjects was administered 4 mg of dexchlorpheniramine and the other 10 received placebo. 150 minutes after ingestion the potential P300 was recorded using an active oddball paradigm. Likewise, efficiency in detecting target stimuli was also evaluated. RESULTS: results show that a single 4 mg dose of dexchlorpheniramine does not alter P300 nor efficiency in detecting target stimuli. CONCLUSIONS: Results show that the dose used has no effect on voluntary processes involving the categorization of target stimuli nor on their detection. However, the alteration of other attentional mechanisms observed in previous work using the same doses suggests that it would be advisable to employ different evoked potential paradigms in the evaluation of the side effects other active principles or psychoactive substances have on auditory attention.

Adult↗