Biomedical subjects

P Perruchet

Publications and source records attributed to P Perruchet.

At least 19 recordsLinked to original sources

PubMed2001

Implicit learning out of the lab: the case of orthographic regularities.

Children's (Grades 1 to 5) implicit learning of French orthographic regularities was investigated through nonword judgment (Experiments 1 and 2) and completion (Experiments 3a and 3b) tasks. Children were increasingly sensitive to (a) the frequency of double consonants (Experiments 1, 2, and 3a), (b) the fact that vowels can never be doubled (Experiment 2), and (c) the legal position of double consonants (Experiments 2 and 3b). The latter effect transferred to never doubled consonants but with a decrement in performance. Moreover, this decrement persisted without any trend toward fading, even after the massive amounts of experience provided by years of practice. This result runs against the idea that transfer to novel material is indicative of abstract rule-based knowledge and suggests instead the action of mechanisms sensitive to the statistical properties of the material. A connectionist model is proposed as an instantiation of such mechanisms.

Child↗

PubMed2000

Context-dependent information processing in patients with schizophrenia.

Thirty schizophrenic patients fulfilling the Diagnostic and Statistical Manual of Mental Disorders IV criteria for schizophrenia and 30 control participants were shown a set of incomplete sentences, and were asked to complete them with the first word(s) that came to mind. Target sentences included an ambiguous word, the ambiguity of which was not resolved within the clause. However, completion necessarily required participants to select one specific meaning. Each target sentence was preceded by another sentence playing the role of context, which was designed to prime the less frequent meaning of the ambiguous word. The results showed that schizophrenic patients, especially those with thought disorder [on the basis of their TLC scores (Thought, Language and Communication Scale; Andreasen, N.C., 1979. Thought, language and communication disorders. Clinical assessment, definition of terms and evaluation of their reliability. Diagnostic significance. Arch. Gen. Psychiatry 39, 778-782)], used the most common meaning of the ambiguous word more frequently than controls, thus revealing a specific deficit in context use. The deficit was observed whether or not the relation between context and target sentences was made explicit. These results are in line with the cognitive models of schizophrenia that postulate a decreased ability to use context information. However, when considered in the light of prior studies (e.g., Bazin, N., Perruchet, P., 1996. Implicit and explicit memory in patients with schizophrenia. Schizophr. Res. 22, 241-248), they suggest that the deficit in processing contextual information is limited to what Baddeley (Baddeley, A.D., 1982. Domains of recollection. Psychol. Rev. 98, 708-729) called the interactive context (which affects the meaning, or the interpretation, of the target event) in contrast to the independent context (which does not interfere with the meaning-based interpretation of the target event).

Adult↗

PubMed1999

Is there a negative correlation between explicit memory and hippocampal volume?

The aim of this research was to study the relationship between explicit memory and hippocampal volume. Seventy healthy adults were administered one implicit memory test and one explicit memory (EM) test and underwent magnetic resonance imaging. The major finding was a negative correlation between the EM test and the right hippocampus/brain volume ratio (t = -0.25, P = 0.03) and the left hippocampus/brain volume ratio (t = -0.27, P = 0.02). This finding is not consistent with pathologic findings, which tend to show a relationship between decrease in memory performance and hippocampal atrophy. This discrepancy is discussed.

Adolescent↗

PubMed1999

Isolating unconscious influences: the neutral parameter procedure.

Earlier demonstrations of unconscious learning have been regularly challenged. In this paper, we suggest that earlier demonstrations were not compelling due to certain properties of the experimental situations, and notably that conscious exploitation of explicit knowledge, if present, would coincide or conflict with the results of unconscious processing. We designed a method consisting of inducing a neutral behavioural change in the way subjects drew geometric figures. Two experiments showed that important and long-lasting modifications of drawing behaviour were obtained following specially devised practice, although these modifications could not be expected from deliberate adaptive strategies. In addition, we showed that subjects were unaware of the manipulation to which they had been exposed. The study provides striking evidence for unconscious learning and offers insights for the design of suitable new tools to investigate unconscious cognition.

Adolescent↗

PubMed1998

Implicit sequence learning in children.

The main purpose of the present study was to examine whether implicit learning abilities, assessed by means of a serial reaction time task, are present to the same extent in 6- and 10-year-old children as in adults. We also wondered whether the knowledge acquired after one learning session is retained after a 1-week delay. And finally, we studied the explicit knowledge developed by the children in this task. Our results show no age-related difference in the serial reaction time performance, which is consistent with the idea that implicit learning abilities may be efficient early in development.

Adolescent↗

PubMed1998

The effect of attentional load on the breathing pattern in children.

Experiments designed to establish the effects of video games on breathing patterns have led to contradictory results. Several authors reported that video games tended to increase breathing frequency (i.e. to reduce breath duration), whereas others reported the opposite. We postulated that video games contain different psychophysiological components which may have opposite effects on breathing pattern. On the one hand, arousal and emotion may tend to stimulate breathing. On the other, focusing attention on the game may prompt subject to inhibit any movement--including breathing--which might be a potential nuisance variable. The aim of this study was to assess the specific effects of the attentional load in an experimental environment characterized by its low emotional impact. We measured breathing variables, cardiac frequency and cortisol levels in 10 healthy children (mean age = 9.2 +/- 1.5 years) who were familiar with the environment, the experimenter and the video game. Breath duration rose significantly, from 2.56 to 3.16 s, as a function of game difficulty. Cortisol levels, heart rate and the thoracic contribution to breathing displayed no significant changes. Taken together, these data suggest that focusing attention on the game tended to inhibit breathing and that previous contradictory reports in this respect were due to the confounding effects of emotion.

Attention↗

PubMed1998

Effects of voluntary changes in breathing frequency on respiratory comfort.

Previous experiments on voluntary breathing have suggested that spontaneous breathing is partly determined by the minimization of respiratory sensations. However, during instructed breathing, respiratory sensations may be confounded with difficulty in achieving the prescribed pattern. In the present experiment, we tested the hypothesis that the subjective assessment of respiratory comfort and the difficulty in following breathing instructions are closely related. A total of 15 subjects adjusted breathing frequency to prescribed values ranging from 40 to 250% of individual spontaneous levels. Then, they scored the difficulty of this task and the discomfort associated with the target frequency. Difficulty scores sharply increased above 100% (spontaneous level) and discomfort scores displayed a similar shape. A significant positive correlation between discomfort and difficulty was found, thus suggesting a possible influence of the difficulty to follow ventilatory instructions on respiratory sensation scores.

Adult↗

PubMed1998

Classical conditioning to hypoxia using odors as conditioned stimuli in rats.

The authors performed a differential conditioning experiment in 30 rats, using 2 odors as the conditioned stimuli (CS+ and CS-) and hypoxia (8% O2) as the unconditioned stimulus. Vanillin was the CS+ and rose the CS- in half of the rats, and vice versa in the other half. Fifteen paired CS+/hypoxia trials and 15 CS- only trials were performed in random order, followed by 3 CS+ only and 3 CS- only trials to test for conditioning. The increase in ventilation from prestimulus levels averaged 116 +/- 85% in response to CS+ versus 55 +/- 36% in response to CS-. This effect was supported by the significant Pre-Post Stimulus x CS Type interaction for this variable (p < .003). The data confirm the sensitivity of breathing to conditioning processes and also indirectly support the hypothesis that feedforward responses may complement feedback reflex pathways in respiratory homeostasis.

Animals↗

PubMed1997

Classic conditioning of the ventilatory responses in rats.

Recent authors have stressed the role of conditioning in the control of breathing, but experimental evidence of this role is still sparse and contradictory. To establish that classic conditioning of the ventilatory responses can occur in rats, we performed a controlled experiment in which a 1-min tone [conditioned stimulus (CS)] was paired with a hypercapnic stimulus [8.5% CO2, unconditioned stimulus (US)]. The experimental group (n = 9) received five paired CS-US presentations, followed by one CS alone to test conditioning. This sequence was repeated six times. The control group (n = 7) received the same number of CS and US, but each US was delivered 3 min after the CS. We observed that after the CS alone, breath duration was significantly longer in the experimental than in the control group and mean ventilation was significantly lower, thus showing inhibitory conditioning. This conditioning may have resulted from the association between the CS and the inhibitory and aversive effects of CO2. The present results confirmed the high sensitivity of the respiratory controller to conditioning processes.

Acoustic Stimulation↗

PubMed1996

Implicit and explicit associative memory in patients with schizophrenia.

Control and Schizophrenic subjects performed memory tests under conditions in which performance is influenced by newly acquired information about associations between pairs of normatively unrelated words (a 'context' word and a target word). In Experiment 1, the associative memory test was implicit. Control and schizophrenic subjects reached the same level of performance and, more importantly, both groups used contextual information to the same extent. In Experiment 2, subjects were submitted to an explicit and an implicit memory test in succession. Overall performance of schizophrenic patients was impaired in the explicit memory test. But, as in Experiment 1, the two groups did not differ in the overall level of implicit memory, and context improved performance to the same extent in both tests. These results run counter to the widespread idea that schizophrenic patients exhibit a deficit in processing all types of contexts, and suggest that the deficit may be limited to the processing of what Baddeley (1982) calls 'interactive' context.

Adult↗

PubMed1996

Ventilatory responses to imagined exercise.

We studied whether the ventilatory responses to imagined exercise are influenced by automatic processes. Twentynine athletes produced mental images of a sport event with successive focus on the environment, the preparation, and the exercise. Mean breathing frequency increased from 15 to 22 breaths/min. Five participants reported having voluntarily controlled breathing, two of them during preparation. Twenty participants reported that their breathing pattern changed during the experiment: 11 participants were unable to correctly report on the direction of changes in frequency, and 13 incorrectly reported changes in amplitude. This finding suggests that these changes were not voluntary in most participants and may therefore reveal automatic forebrain influences on exercise hyperpnea. However, these changes may also reflect nonspecific processes (e.g., arousal) different from those occurring during actual exercise.

Adult↗

PubMed1995

Conceptual implicit memory: a developmental study.

The widely accepted standpoint that implicit memory emerges earlier in development than explicit memory, and is more stable from childhood to adult age, is based on experimental data essentially collected in perceptual tasks. The present study was aimed at investigating whether these findings still hold when a more conceptual task is used. We compared the performance of children at two age levels (2nd and 4th grades) on a category-exemplar generation task. Results showed that performances of the two groups were comparable when the target items were typical of their categories, as in Experiment 2, and for a subset of the items in Experiment 1. However, the older children outperformed the younger children in Experiment 1 when the items selected were atypical of their categories. Interpretations of these findings are discussed.

Child↗

PubMed1994

Ventilatory conditioning by self-stimulation in rats: a pilot study.

This article describes an experimental attempt to condition breathing pattern in rats. In this experiment, a freely moving rat was first rewarded by an electrical stimulation of the medial forebrain bundle whenever inspiratory duration (TI) exceeded 300 ms. A bidirectional control was then used: TIs longer than 400 ms were rewarded, and then TIs shorter than 300 ms were rewarded. The frequency of TIs longer than 300 ms increased when this event was rewarded, further increased when TIs above 400 ms were rewarded, and decreased during reversal conditioning (TI < 300 ms). At the beginning of the experiment, stimulation caused increased arousal and motor activity, but after prolonged conditioning, the brain stimulation was associated with quiet wakefulness. Although the general procedure appears to be well-suited to the experimental study of voluntary breathing, some possible improvements are suggested for further, more extensive investigations.

Animals↗

PubMed1994

The dissociation of explicit and implicit memory in depressed patients.

Twenty-three in-patients fulfilling DSM-III-R criteria for major depressive disorder were submitted to a standard cued recall test, and to a word-stem completion test devised to assess the effect of the initial presentation without the explicit retrieval of the words being necessary. Results show that depressed patients are impaired on the cued recall task in comparison with controls matched for sex, age, and educational level. However, the two groups do not differ in the word-stem completion task. This dissociation between explicit and implicit expressions of memory disappeared when patients recovered, although they were still hospitalized and under psychotropic medication. These results are examined in the light of the distinction between effortful and automatic processes.

Adult↗

PubMed1993

The effect of voluntary breathing on reaction time.

The effect of voluntary changes in inspiratory duration on reaction time was studied in 17 normal subjects. All received a visual feedback on inspiratory duration and successively adjusted this variable to two target values which were respectively higher and slightly lower than resting level. The order of the two tasks was counterbalanced across subjects. Reaction times to auditory stimuli were measured during a key-pressing task immediately after voluntary breathing. Voluntary control of inspiration induced concomitant changes in breathing period and minute ventilation. Per cent changes in these breathing variables and in reaction times under the two conditions were analysed. Correlations were significant for period not for minute ventilation. This effect was probably due to neuromuscular rather than humoral factors.

Adolescent↗

PubMed1993

Abstraction of covariation in category learning: a critical note on K. Richardson's studies.

Several studies directed by K. Richardson (Richardson, 1986, 1987; Richardson & Carthy, 1989, 1990) claimed that people are able to abstract imperfect covariations among feature variables defining artificial categories, and to use that information in various subsequent tasks. We challenge this claim on a twofold basis. First, a large part of the performance variance Richardson attributed to covariation knowledge may be accounted for by a very simple exemplar model, which assumes no abstractive processes. Second, the residual influence of relational information on performance may be attributed to the knowledge subjects have acquired in real-world situations before their training with the study exemplars.

Analysis of Variance↗

PubMed1992

Conscious knowledge and changes in performance in sequence learning: evidence against dissociation.

Two experiments examined the relation between explicit knowledge and motor performance on the serial reaction time task developed by Nissen and Bullemer (1987). Tests of free recall and recognition of sequence components revealed that reliable explicit knowledge was acquired after an amount of practice that was hardly sufficient to improve mean motor performance. In addition, reaction time improvement was limited to the ending trials of the 3- and 4-trial sequence components that Ss recalled or recognized. These results were replicated in Experiment 3, in which Ss were trained under attentional distraction in the task developed by Cohen, Ivry, and Keele (1990). Overall, these findings undermine the most direct experimental support for the widespread view that conscious knowledge and performance in sequence-learning tasks tap 2 independent knowledge bases in normal Ss.

Adult↗

PubMed1991

Effect of practice on the voluntary control of a learned breathing pattern.

Changes in orientation of attention and ventilatory data were examined in three normal volunteers who practiced a learned ventilatory pattern over eight training sessions. The breathing task was a voluntary increase of inspiratory duration up to a given target with the aid of informative feedback on this variable. The orientation of attention was investigated through reaction time (RT) to auditory stimuli presented at different points in inspiration and expiration, during either automatic or voluntary control of breathing. Findings show that RTs are longer during voluntary than automatic breathing throughout the experiment, and that they decrease across sessions in both conditions. In the first sessions, RTs were longer during expiration than inspiration but this difference cancels out in the last sessions. The results are discussed in terms of attentional demands of control of breathing, automatization, and the connection between automatic and voluntary control of breathing. This work shows that after eight practice sessions, the orientation of attention displays significant changes; however, the control of breathing remains attention demanding.

Animals↗