Biomedical subjects

J Requin

Publications and source records attributed to J Requin.

At least 19 recordsLinked to original sources

PubMed1995

Neural correlates of partial transmission of sensorimotor information in the cerebral cortex.

Using single neuron recordings in monkey primary motor (MI) cortex, two series of experiments were conducted in order to know whether response preparation can begin before perceptual processing finishes, thus providing evidence for a temporal overlap of perceptual and motor processes. In Experiment 1, a "left/right, Go/No-Go" reaction time (RT) task was used. One monkey was trained to perform wrist flexion/extension movements to align a pointer with visual targets. The visual display was organized to provide a two-dimensional stimulus: side (an easy discrimination between left and right targets) which determined movement direction, and distance (a difficult discrimination between distal and proximal targets) which determined whether or not the movement was to be made. Changes in neuronal activity, when they were time-locked to the stimulus, were almost similar in the Go and No-Go trials, and when they were time-locked to movement onset, were markedly reduced in No-Go as compared to Go trials. In Experiment 2, a stimulus-response compatibility (SRC) task was used. Two monkeys were trained to align a pointer with visual targets, on either left or right. In the spatially "compatible" trials, they had to point at the stimulus position, whereas in the "incompatible" trials, they had to point at the target located in the opposite side. For 12.5% of neurons, changes in activity associated with incompatible trials looked like changes in activity associated with movements performed in the opposite direction during compatible trials, thus suggesting the hypothesis of an automatic activation of the congruent, but incorrect response. Results of both experiments provide evidence for a partial transmission of information from visual to motor cortical areas: that is, in the No-Go trials of the first task, information about movement direction, before the decision to perform or not this movement was made, and, in the incompatible trials of the SRC task, information about the congruent, but incorrect response, before the incongruent, but correct response was programmed.

Animals↗

PubMed1995

Neuronal correlates of the specification of movement direction and force in four cortical areas of the monkey.

Single-neuron activity was recorded in several areas of the cerebral cortex when monkeys performed a movement-precueing reaction time task. In such a task, information provided by a first signal ('preparatory signal', PS) refers to what has to be done in response to a second signal ('response signal', RS). Two monkeys were trained to rotate a handle by performing wrist flexion/extension movements while two levels of frictional resistance were applied to the manipulandum. The PS provided complete, partial or no prior information about movement direction (flexion or extension) and/or the level of the frictional force (weak or strong). Since providing partial prior information about either movement parameter shortened reaction time (RT)--RT being shorter when movement direction than movement force was precued--, as compared to the condition in which no prior information was provided, the analysis of changes in neuronal activity during the preparatory period (PP), i.e., the instructed delay between PS and RS, makes the study of the neuronal mechanism underlying the specification of movement parameters possible. The activity of 411 neurons of the primary motor (MI), premotor (PM), somatosensory (SI) and parietal (PA) cortex was recorded during task performance. Many more neurons changed selectively their activity in relation to movement direction than in relation to movement force, not only during PP, but also during RT and movement time (MT). The number of purely direction-related neurons increased, whereas the number of purely force-related neurons decreased from SI to PA, then to MI and finally to PM. During PP, selective activity changes were related only to one movement parameter, whereas during RT and MT, a large population of neurons changed its activity in relation to both movement direction and force, especially in MI. These data provide further evidence for the clustering of distinct neuronal populations responsible for programming movement direction and force.

Animals↗

PubMed1995

Modulation of spinal reflexes: arousal, pleasure, action.

The human startle reflex is reliably modulated by the affective valence of foreground pictures, with larger reflexes elicited when viewing unpleasant relative to pleasant scenes. If this modulation is due to priming of the defensive startle reflex by an aversive foreground, a different pattern should occur for a reflex that is not inherently defensive in nature. In the current study, affective modulation was investigated using the spinal tendinous (T) reflex, which is well documented as sensitive to differences in arousal and is involved in actions that are both appetitively defensively motivated. As such, T reflexes elicited during unpleasant pictures were not expected to be augmented relative to those elicited in the context of pleasant pictures. Results showed that T reflexes were facilitated during processing of arousing stimuli-either pleasant or unpleasant relative to low-arousal neutral materials. These effects of emotional stimuli on T-reflex amplitude are consistent with hypothesis that motivational priming underlies affective reflex modulation.

Adult↗

PubMed1994

Neuronal coding of stimulus-response association rules in the motor cortex.

Two monkeys were trained to perform wrist movements to align a pointer with visual targets. In the spatially 'compatible' condition, monkeys had to point at the target position (left/right), whereas in the 'incompatible' condition, they had to point at the position opposite to the target. A large proportion of neurones recorded in the primary motor cortex showed changes in activity according to either the side of the target or the side of the movement. However, more than 40% of neurones changed their activity as a function of the stimulus-response mapping rule. Some of these neurones, being sensitive only to the stimulus-response compatibility effect, must therefore be viewed as specifically involved in the neural mechanisms that control the association process between sensory inputs and motor outputs.

Animals↗

PubMed1994

Brain waves associated with musical incongruities differ for musicians and non-musicians.

Musicians and non-musicians were presented with short musical phrases that were either selected from the classical musical repertoire or composed for the experiment. The phrases terminated either in a congruous or a 'harmonically', 'melodically', or 'rhythmically' incongruous note. The brain waves produced by the end-notes differed greatly between musicians and non-musicians, and as a function of the subject's familiarity with the melodies and the type of incongruity. The timing of these brain waves revealed that musicians are faster than non-musicians in detecting incongruities. This study provides further neurophysiological evidence concerning the mechanisms underlying music perception and the differences between musical and linguistic processing.

Brain↗

PubMed1994

Are extent and force independent movement parameters? Preparation- and movement-related neuronal activity in the monkey cortex.

Movement extent and movement force can be independently controlled in motor performance. Therefore, independent representations of extent and force should exist in the central nervous system (CNS). To test this hypothesis, microelectrode recordings were made in sensorimotor cortex of monkeys trained to perform visually cued wrist flexion movements of two extents, against two levels of frictional resistance. An initial preparatory signal (PS) provided complete, partial or no information about extent and/or force of the movement, which had to be performed in response to a second, response signal (RS). The activity of 511 neurons of the primary motor cortex (MI), the premotor cortex (PM), the postcentral cortex (PC), and the posterior parietal cortex (PA) was recorded in two monkeys. Both reaction time (RT) and neuronal data suggest that there exist independent neuronal mechanisms responsible for the programming of either parameter. On the one hand, partial information about either movement parameter shortened RT when compared with the condition of no prior information. On the other hand, there were, among others, two discrete populations of neurons, one related only to extent, the other only to force. Preparatory changes in activity related to either movement parameter were mainly located in the frontal cortex, especially in the PM. After occurrence of the RS, the percentage of selective changes in activity increased and tended to extend to the parietal cortex. In particular during the movement, force-related changes in activity have been encountered in PA. Furthermore, we conducted trial-by-trial correlation analyses between RT and preparatory neuronal activity for all conditions of prior information. The mean correlation coefficient was significantly higher in the condition of information about movement extent than of information about movement force and it was significantly higher in MI/PM than in PC/PA.

Animals↗

PubMed1993

The predictive value for performance speed of preparatory changes in neuronal activity of the monkey motor and premotor cortex.

Three monkeys were trained in a precued reaction time (RT) paradigm. An initial preparatory signal (PS) provided complete, partial or no information about direction and extent of a wrist flexion/extension movement which was executed after the second, response signal (RS). A PS providing information about direction shortened the RT much more than a PS indicating movement extent. The activity of 464 task-related neurons was recorded in the primary motor (MI) and premotor (PM) cortex. Not only the timing and amplitude of mean activity changes were analyzed, but also trial-by-trial correlation analyses between RT and discharge frequency during the PS-RS interval were conducted. Correlations were stronger in the condition of information about direction than in conditions of information about extent or no information. Considering directionally selective neurons, correlations were stronger when the neuron's preferred direction than the opposite direction was precued. Correlation distributions were similar for MI and PM. Correlations were negative when preparatory activity increased during the PS-RS interval, and positive when activity decreased. Correlation analyses between behavioral performance and neuronal activity can thus be considered as a powerful tool to obtain a deeper insight into the functional mechanism of motor preparation.

Animals↗

PubMed1992

Effects of preliminary perceptual output on neuronal activity of the primary motor cortex.

Observations of single neurons in the primary motor cortex of 1 monkey provided evidence that preliminary perceptual information reaches the motor system before perceptual analysis is complete. Neurons were recorded during a task in which 1 stimulus was assigned to a wrist flexion response and another was assigned to wrist extension. Two stimuli were assigned to a no-go response; each was visually similar to either the flexion or the extension stimulus. When a no-go stimulus was presented, neurons responded with weaker versions of the discharge patterns exhibited to the visually similar stimulus requiring a movement, suggesting that neurons receive partial perceptual information favoring that movement. Functionally separable neuronal populations were identified, and differences in the activations of these provide evidence about the functional effects of preliminary perceptual output on movement control processes.

Animals↗

PubMed1991

Changes in electromyographic responses to muscle stretch, related to the programming of movement parameters.

Three experiments are reported that used the advance information paradigm which consists of providing subjects with either no or partial information about an upcoming movement. Subjects moved handles to control the vertical displacements of CRT beams, to point to eight targets. The illumination of different combinations of these targets prior to movement execution provided advance information about which hand, movement direction, or movement extent would be required. Reaction time (RT), integrated EMG activity in the forearm extensor and flexor muscles, and M1, M2, and M3 components of the stretch reflex responses triggered in these muscles were analysed as a function of the precued movement parameter. Compared to the no-information condition, RT decreased in all precue conditions; however, the reduction was greater when direction than when hand was precued, and greater when hand than extent was precued. The EMG activity of forearm muscles increased during the preparatory period in all precue conditions, but generally did not differ among them. An overall facilitation of the stretch reflex components was observed in all precue conditions. This facilitation: (1) was greater for flexor than extensor muscles, (2) was similar regardless of the degree of extent precued, (3) differed for the M2 and M3 components depending on whether the responding hand precued was ipsilateral or contralateral. When the precued movement direction was considered, similar changes in the M3 component were found in extensor and flexor muscles. M3 was facilitated when the muscle was precued as an agonist and was inhibited when it was precued as an antagonist. Collectively these data provide support for a motor programming conception of movement organization.

Adolescent↗

PubMed1990

A comparison of preparation-related neuronal activity changes in the prefrontal, premotor, primary motor and posterior parietal areas of the monkey cortex: preliminary results.

Single-unit activity of prefrontal (PF), premotor (PM), primary motor (MI) and posterior parietal (PP) cortical areas was analysed from 3 monkeys trained to perform visually guided arm movements in a between-arms choice reaction time (RT) task. Percentages of preparation-related units, i.e. units whose change in activity during the preparatory period was correlated with RT, were 19% in PF, 31% in MI, 46% in PM and 68% in PP, respectively. These data support the hypothesis that neural pathways connecting PP association areas to MI, via PM, are involved mainly in movement planning.

Animals↗

PubMed1989

Monkey primary motor and premotor cortex: single-cell activity related to prior information about direction and extent of an intended movement.

1. This study was devoted to the neuronal processes underlying the construction of the motor program. Two monkeys were trained in a choice reaction time task to perform precise wrist flexion and extension movements of small and large extent. During a trial, the first visual signal, the preparatory signal (PS), informed the animal completely, partially, or not at all about direction and/or extent of the forthcoming movement. After a constant waiting period, a second visual signal, the response signal (RS), was illuminated calling for execution of the requested movement. 2. Reaction time (RT) and movement time (MT) measurements during the training as well as the recording sessions revealed that providing prior information about movement parameters strongly affected RT, but only slightly affected MT. Reaction time decreased in relation to the amount (number of movement parameters precued) and the type of prior information. Providing information about movement direction shortened RT much more than providing information about movement extent. Behavioral data support a parametric conception of motor programming, i.e., that the programming of the different movement parameters results from assembling separate processes of different duration. These results are compatible with the model in which programming processes are serially and hierachically ordered, movement direction being processed before movement extent. 3. Single-cell recording techniques were used to study neuronal activity of the primary motor (MI) and the premotor (PM) cortex, contralateral to the active arm. The activity of 155 neurons of MI and 158 neurons of PM was recorded during performance of the task. Of these 313 neurons, only 14 neurons did not change their activity during execution of the task. Two hundred and seven neurons whose activity changes were related to movement direction and/or movement extent have been selected for the further study. They were classified into three main groups: 1) execution-related neurons (49 in MI, 27 in PM), 2) preparation- and execution-related neurons (48 in MI, 54 in PM), and 3) preparation-related neurons (8 in MI, 21 in PM). 4. Directionally selective, execution-related neurons were found to be more frequently located within MI (81/105, 77.1%) than within PM (55/102, 53.9%), whereas directionally selective, preparation-related neurons appeared to be more frequently located within PM (47/102, 46.1%) than within MI (24/105, 22.9%).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Neuronal activity and information processing in motor control: from stages to continuous flow.

Some years ago, we proposed, along with others, that the isomorphism between models of information processing by stages and the organization of neural pathways connecting functionally specialized neuronal networks was a guideline for conducting experiments in which the integration of methods and concepts of cognitive psychology and of neurophysiology was a promising approach to increase our knowledge of the processes responsible for motor control. At a time when models of serially organized information processing stages are being increasingly challenged, the deciphering of the underlying brain processes increasingly suggests that current views about the linkage between neural structures and behavioural functions must be reconsidered. First, at the "molar" level, the notion of a functional specialization of neuronal networks as, for example, being "sensory", "sensorimotor" or "motor", has to be viewed as a quantitative and not as a qualitative concept. Second, at the "molecular" level, the notion of a clear-cut functional differentiation between neuronal units, or between small sets of neurons, must similarly be revised: a neuron may be more or less "sensory" or "motor" and, moreover, may share both these functional properties to varying degrees. When the brain processes responsible for movement control are reconsidered in the light of these two concepts--that is a functional heterogeneity of structurally defined neuronal networks, as well as a continuum in functional specification of isolated neuronal units--data collected by using single-cell recording of neuronal activity fit well into the model of a continuous flow of information processing: neural pathways from the cortical parietal association areas to the corticospinal apparatus appear as a privileged sensorimotor information stream along which the amount of neuronal activity responsible for movement planning progressively decreases, while the amount of neuronal activity involved in movement execution progressively increases.

Animals↗

PubMed1986

Changes in neuronal activity of the monkey precentral cortex during preparation for movement.

The aim of this study was to analyze the changes in neuronal activity of the motor cortex associated with preparation for movement. Monkeys were trained to perform a between-hands choice-reaction time (RT) task. They pressed upon two levers with both hands and, after a preparatory period of 1-s duration initiated by a warning tone, they must point at either a left- or right-located target, when illuminated as a response signal, with either the left or right hand. The level of preparation for performing either sided movement was changed by manipulating, across block of trials, the relative probabilities for the left and right hands to point at the corresponding target. When considering behavioral data averaged over daily sessions, it was found that RT significantly decreased as response probability increased, whereas movement time (MT) was not affected. However, large changes in this rule were observed when data collected within a single session were considered. Response probability manipulation was acting on RT alone in 27% of sessions, on MT alone in 19% of sessions, and on both RT and MT in 17% of sessions. Statistically significant trial-by-trial correlations between RT and MT were found; of positive sign for 34% of sessions and of negative sign for 12% of sessions. Electromyographic recordings from the biceps and triceps brachii showed that muscle activity remained stable during the preparatory period, both muscles of the performing arm began to be coactivated about 70-130 ms before the lever release, biceps activation being progressively larger than that of the triceps, and the rising slope of biceps activation was steeper for short than for long RTs. Single-cell recording techniques were used to study the neuronal activity of primary motor cortex during the performance of the task. One hundred and fifteen units in area 4, whose activity was recorded during a whole experimental session, were selected for further analysis. Disregarding 4% of units which did not exhibit any movement-related change in activity, it was found that twenty-one percent of units were related to contralateral movements only, 2% to ipsilateral movements only, and 73% to both sided movements. Among this last subset, 27% of units exhibited reciprocal movement-related changes in activity, the most often an excitation for contralateral movements and an inhibition for ipsilateral movements, and 50% of units exhibited a movement-related change in activity in the same direction for both movements, the most often an excitation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1984

On controlling force and time in rhythmic movement sequences: the effect of stress location.

Accentuation involves modulation of motor intensity. It differentiates a movement from others within a motor sequence. Does the serial position of the accent characterize the whole sequence as a particular response? How are the control of time and force coordinated in the motor sequence? Subjects produced sequences of four fingertaps on a key. Time of onset and force of each tap were recorded. Tapping rate was imposed by a string of four clicks delivered at 180-msec intervals before each trial. A flashed digit served as go signal. It indicated to the subject which of the four taps had to be tapped stronger (stress +) or weaker (stress -) than all the others. These conditions were run in separate series. Reaction time (RT) of the sequence increased when the number of equally likely locations of the stress increased from 2 to 4. RT was also longer under the stress - than under the stress + condition. Tapping intervals were longer before and after the stressed tap than elsewhere in the series. The first and last intervals tended to be longer than the second one. These effects were the same under both stress conditions. The RT data indicate that the motor sequence is identified as a particular response before it starts. Timing is partly force-independent, but is modulated by central processes that control force.

Attention↗

PubMed1982