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Biomedical subjects

C Alain

Publications and source records attributed to C Alain.

15 recordsLinked to original sources
PubMed1995

Middle latency auditory evoked potentials to tones of different frequency.

The scalp distributions of middle latency auditory evoked potentials (MAEPs) elicited by tone bursts of 250 and 4000 Hz were compared in two experiments. Na (19.9 ms), Pa (29.8 ms), and Pb (51.4 ms) components elicited by tones of either frequency had fronto-central distributions, whereas the Nb component (38.4 ms) was maximal at parietal sites. Although the distributions of MAEP components varied as a function of the ear of stimulation, no significant differences were found as a function of tone frequency. The results are consistent with suggestions that MAEPs reflect activation of non-tonotopically organized generators.

Acoustic Stimulation↗
PubMed1994

Brain indices of automatic pattern processing.

The extent to which the auditory system automatically encodes simple auditory patterns was investigated by recording event-related brain potentials (ERPs) to non-attended sounds in subjects reading a book. ERPs were recorded to tones alternating regularly in pitch and to rare breaks in the alternating sequence. In all conditions, breaks in the pattern elicited a right hemisphere dominant fronto-central mismatch negativity (MNN) at a latency of 140-220 ms. The MMN increased in amplitude and decreased in latency with increasing pitch separation and stimulus rate. The results suggest that the processing of auditory patterns occurs automatically and depends on a rapidly fading short-term acoustic memory.

Acoustic Stimulation↗
PubMed1994

The effects of the amount and variability of practice on the learning of a multi-segmented motor task.

Since the Shea, J.B. and Morgan (1979) study, investigators have repeatedly shown that the learning of a set of movement patterns (as evaluated in a retention test) is enhanced when acquisition occurred under a random rather than a blocked schedule of practice. Supposedly, this is the case because a random schedule of practice necessitates more elaborate cognitive activities than a blocked schedule before each acquisition trial can be initiated. Our main objective was to determine whether the advantage for learning found for random practice increases as a function of the number of acquisition trials. During acquisition, the results indicated a general tendency for smaller movement reproduction errors under a blocked rather than a random schedule of practice. However, this effect disappeared with larger amount of acquisition trials. In retention, larger errors were observed when acquisition occurred under a blocked rather than a random schedule of practice. Finally, the disadvantage for learning observed for the blocked schedule of practice disappeared under a block-repeated condition in which each movement pattern was first practiced under a blocked schedule which was then repeated a second time. The results are discussed in terms of the so-called contextual interference effect and indicates some of its limitations.

Humans↗
PubMed1994

Signal clustering modulates auditory cortical activity in humans.

Auditory streaming and its relevance to attentional processing was examined using event-related brain potentials (ERPs) in situations facilitating perception of one or two streams of sounds. Subjects listened to sequences of brief tones of three different frequencies presented in random order. In evenly spaced (ES) conditions, the three frequencies were equidistant on the musical scale. In clustered, easy (CE) conditions, the attended frequency was distinct, while the middle and extreme distractor tones were clustered together. In clustered, hard (CH) conditions, the attended frequency was clustered with one of the distractors. The subjects pressed a button in response to occasional target tones of longer duration at a prespecified frequency. The subjects were faster and more accurate in CE conditions than they were in ES conditions, and ERP attention effects were enhanced in amplitude in CE conditions. Conversely, the subjects were slower and less accurate in CH conditions and ERP attention effects were delayed in latency and decreased in amplitude. Clustering effects suggest that the processing of stimuli belonging to the attended stream was promoted and the processing of those falling outside the stream was inhibited. The timing and scalp distribution of clustering-related changes in ERPs suggest that clustering modulates early sensory processing in auditory cortex.

Adult↗
PubMed1993

Frequency-related differences in the speed of human auditory processing.

Three experiments were performed, two comparing the peak latencies of auditory evoked potentials (AEPs) elicited by 250 Hz and 4000 Hz tone pips and a third comparing simple reaction times (RTs) to the same stimuli. In the AEP experiments, the latencies of brainstem, middle and long-latency components were delayed following 250 Hz tone pips in comparison with the latencies of the same components evoked by loudness-matched 4000 Hz tones. Frequency-related latency differences increased with component latency, ranging from less than 1.0 ms for wave V of the brainstem AEP, to more than 20.0 ms for the cortical N1 component. Interpeak latency differences were also significantly lengthened following the 250 Hz tone pips. In the behavioral study, RTs were 14.6 ms slower following 250 than 4000 Hz tone pips. The results suggest that the time required for the sensory analysis of auditory signals varies inversely with their frequency.

Acoustic Stimulation↗
PubMed1993

Perceptual context and the selective attention effect on auditory event-related brain potentials.

Two experiments examined the effect of the perceptual context established through tonal grouping on neuroelectric responses during selective listening. Subjects monitored one of the extreme pitches in four-pitch tone sequences and detected rare longer tones of the designated pitch. In the first study, tonal grouping was manipulated by changing the tonal separation between the extreme pitches and their nearest neighbor, keeping the extreme pitches constant. Grouping increased the negativity of the attended-unattended difference potential. A second study examined the effect of grouping on the attention-related negativity when it opposed the effect of physical similarity. The proximity of extreme pitches varied, keeping the middle pitches constant. The effect of grouping on event-related potentials (ERPs) for the middle pitches was varied according to the tone being attended. ERPs for the middle tone adjacent to the attended tone became more negative with grouping, whereas ERPs for the distant middle tone became less negative with grouping. These effects suggest that the attention-related negativity is sensitive to contextual information.

Adult↗
PubMed1993

Feature processing during high-rate auditory selective attention.

Auditory event-related brain potentials (ERPs) and reaction times were analyzed in a selective attention task in which subjects attended to tone pips presented at high rates (interstimulus intervals [ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 250-350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110-120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feature conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.

Acoustic Stimulation↗
PubMed1993

Distractor clustering enhances detection speed and accuracy during selective listening.

The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times. Similar effects were found at fixed and variable SOAs. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.

Adult↗
PubMed1990

Additive latency effects of selective and nonselective restricted priming types.

The purpose of this investigation was to examine further the contention of Alain et al. (1988) that a third priming type exists, called nonselective restricted (NSR) and controlled by response probability, which is distinct from those types influenced by foreperiod duration (nonselective general priming) and prediction probability (selective priming). In a four-choice reaction time (RT) task, prediction probability (.5, .7, & .9, indicating the likelihood of a particular response) and response probability (.5, .9, denoting the likelihood that a response would be needed at all) exerted significant but noninteractive effects on RTs for prepared responses (most probable), suggesting that each of these probabilities influence different priming types (Sternberg, 1969; selective and NSR, respectively). This was further indicated by the fact that prediction probability, but not response probability, significantly altered RTs for the unprepared (lesser probable) responses. Finally, the hypothesized nonselective character of NSR priming (i.e., all outputs controlled by response probability are equally affected by its value changes) was supported when responses were equiprobable, and, while the null effect of response probability just mentioned seemingly argued against this property when selective priming took place, the interpretation provided herein negated this opposition.

Adult↗
PubMed1990

Study of decision-making in squash competition: a computer simulation approach.

This paper describes how a computer simulation approach was used to specify some of the cognitive processes underlying decision-making in squash competition. The work presented in this article focused on the cognitive strategy of the defending player when choosing among three categories of preparation. (Total preparation for one particular event, partial preparation in favor of one event, and absence of biased preparation.) The defending player is viewed as in information processing system (IPS) placed in a problem-solving situation, the problem being what decision to reach. There are four steps inherent to the computer simulation approach: (a) obtaining the verbal protocol, (2) analyzing the protocol, (3) computer simulation, and (4) validation. This paper describes how each of those steps have been completed, with a special emphasis being placed on the first step of the procedure, that of obtaining the verbal protocol.

Cognition↗
PubMed1989

Human intracerebral potentials associated with target, novel, and omitted auditory stimuli.

We recorded late auditory potentials from lateral and medial regions in the frontal, temporal and parietal lobes of patients with temporal lobe epilepsy implanted with horizontal depth electrodes. Tone sequences were presented in three tasks: 1) auditory target detection in a tone sequence, 2) target detection with interspersed novel stimuli, and 3) detection of stimulus omissions. At frontal sites, potentials to targets showed a triphasic response with peak latencies around 200, 270 and 350 ms. At temporal sites, potentials consisted of a generally positive 285 ms peak which was sometimes accompanied by a negative peak at 200 ms or at 400 ms. At parietal sites, potentials were generally triphasic with latencies of about 230, 300, and 370 ms. At most sites, potentials evoked by novel stimuli had shorter latencies than those evoked by targets. The frontal and parietal potentials were either absent or strongly attenuated during stimulus omissions. The results lend further support to the multiple generator hypothesis of late potentials and suggest that some of the cerebral sources of the late potentials are stimulus dependent while others are not.

Acoustic Stimulation↗
PubMed1983

[Decision strategy as a function of uncertainty of the result: I. Latency of the decision].

Until now, the decision strategy used by human beings faced with a dichotomous situation was studied considering that speed of reaction was the main dependent variable. It was found that, in a two choice reaction time (CRT) task, subjects used a very conservative decision strategy. That is, when compared with events of 0.5 probability, only those events with a probability of no less than 0.9 caused a significant decrease in CRT. In real sport situations however, the tennis player can not only increase his speed of response but can also change his position on the court in order to defend more appropriately the area of the court which appears more likely to be attacked. Two experiments were conducted in order to verify this hypothesis. In both experiments, a two CRT task was used; the independent variables being: (a) event probability and (b) time allotted to complete the appropriate response (TA). Results indicate that as soon as the probability of an attack reached 0.7, subjects started initiating defensive responses closer to the most probable area of attack. It thus appears that subjects were not as conservative as that reported in studies where CRT measures only were considered. On the other hand, subjects used a strategy which enabled them to reduce their total response time without increasing choice errors. In fact it seems that, when facing event uncertainty, the main concern of the human being is to keep his error rate as low as possible even if this is not the best strategy to use.

Analysis of Variance↗
PubMedDate not supplied

Intracerebral amplitude distributions of the auditory evoked potential.

Intracerebral auditory evoked potentials were recorded from multi-contact electrodes chronically implanted in frontal, temporal, and parietal regions of the brains of 10 epileptic patients. Binaurally presented tones produced a large widely distributed biphasic potential with a close latency correspondence to the scalp vertex response. In each hemisphere, this intracerebral response inverted in polarity from posterior temporal to frontal sites. This response also showed large amplitude changes in the inferior parietal lobe. The distribution of this response is compatible with bilateral posterior temporal sources with a dorso-frontal orientation.

Adult↗