Les bases neurales de la perception du temps et de la régulation temporelle de l'action

Adaptation to environment requires that temporal characteristics of events and actions are taken into account. The neural bases of temporal encoding and memory mechanisms raise core questions. Interesting information is provided by the recording of slow brain potential changes, thanks to the excellent temporal resolution of this method. The recording of metabolic activity changes enables identification of several cortical and subcortical structures which subtend temporal mechanisms. Current data enlighten the involvement of the basal ganglia and the frontal cortex (in particular the supplementary motor area) in time processing.     

Younger apes and human children plan their moves in a maze task

Planning defined as the predetermination of a sequence of actions towards some goal is crucial for complex problem solving. To shed light on the evolution of executive functions, we investigated the ontogenetic and phylogenetic origins of planning. Therefore, we presented all four great apes species (N = 12) as well as 4- and 5-year-old human preschoolers (N = 24) with a vertical maze task. To gain a reward placed on the uppermost level of the maze, subjects had to move the reward to the bottom through open gaps situated at each level of the maze. In total, there were ten gaps located over three of the maze’s levels, and free passage through these gaps could be flexibly blocked using multiple traps. Due to the decision tree design of the maze, the subjects had to plan their actions depending on the trap configuration up to two steps ahead to successfully retrieve the reward. We found that (1) our measure of planning was negatively correlated with age in nonhuman apes, (2) younger apes as well as 5-year-old children planned their moves up to two steps ahead whereas 4-year-olds were limited to plan one step ahead, and (3) similar performance but different underlying limitations between apes and children. Namely, while all species of nonhuman apes were limited by a lack of motor control, human children exhibited a shortage in shifting their attention across a sequence of subgoals.     

Frustration and stereotyped behaviour in human subjects

The investigation was designed to show the effects upon behaviour of three different durations of frustration, and two degrees of motivation during the frustrating period. Frustration was induced in 144 subjects by setting them the task of “learning” an insoluble temporal maze; they had to record their responses by pressing on one or other of two morse-type keys. Its effect was measured in terms of:

(1) The time taken to learn a soluble maze introduced, without the subjects' knowing it, by changing the system of “rewarding” responses from one based on chance to one based on the constant repetition of a pattern requiring the responses: Left—Right—Right, for its solution.

(2) The tendency for the subjects to show stereotypy of behaviour by responding on the same key for a number of trials in succession without reaching a solution.

(3) The pressure exerted on the response keys, which was taken to be a measure of vacillation.

Predictions that the time taken to learn the soluble task, and the stereotypy, would increase in direct relation to the duration of the frustrating period and the degree of motivation were tested.

It was found that, while there was an immediate increase in both the time taken to learn the soluble task and the stereotypy after a short period of frustration, a point was reached under conditions of prolonged frustration after which no further increase occurred and some adjustment to the situation was shown.

Some confirmation of the effect of increase in motivation in the direction predicted was obtained in all cases, but the differences were not statistically significant. The rankings of the subjects according to the time taken to learn the soluble task and the degree of stereotypy were found to be closely correlated. A definite tendency towards increased vacillation of response was seen in many of the records during the period when frustration might have been expected to have been at its peak.

These findings are discussed in relation to Maier's theory of frustration and to Selye's concept of a “general adaptation syndrome.” The latter theory is more suitable for the interpretation of the results of the present investigation.     

Développement de la précision temporo-motrice et cadences spontanées de jeunes enfants

Fifty children (six to ten years old) were asked to tap a flat surface as regularly as possible with their finger at different semi-spontaneous tempi. Their chosen tapping speed was estimated by each sequence's mean inter-tap interval. The range of chosen speeds widens with age. The just tenable difference (JTD) between inter-tap intervals is proportional to their reference, the mean. The motor-timing precision, estimated through the standard-deviation/mean ratio, clearly improves with age. Children are more precise at faster tempi, not around their “normal” tempo as adults. Our simple semi-spontaneous finger-tapping task could be applied to the clinical evaluation of age-dependent explicit and implicit timing components in motor performance.     

Radial arm maze performance of mice: acquisition and atropine effects

CD-1 mice were successfully trained in a six-arm radial maze in which half of the arms were baited, a procedure which had been used to differentiate between reference and working memory. Stable performance was achieved following eight daily training sessions, as measured by decreasing running time and number of errors. This finding strengthens the foraging hypothesis as a basis for the performance of rodents in the radial maze. Acute subcutaneous administration of the cholinergic antagonist atropine sulfate (1-6 mg/kg) to trained mice produced dose-related increases in running time and working memory errors, with a slight decrease in reference memory errors. This is in agreement with other studies on the role of the cholinergic system in memory processes. The peripheral cholinergic blocker, atropine methyl nitrate (4 mg/kg), somewhat increased running time without decreasing performance accuracy. In contrast to the prolonged pharmacological and physiological effects of atropine, behavioral decrements disappeared within 3 hr. It is concluded that mice trained in the radial arm maze may be used for screening of the effects of drugs on cognitive function.     

Performance of normal and neurological mutant mice on radial arm maze and active avoidance tasks

The objectives of the present study are to assess the import of gene-imposed structural alterations on behavioral performance and obtain performance data preliminary to studies of experimental mouse chimera behavior. Reeler, staggerer, and weaver neurological mutant, and control B6C3 and ichthyosis mice were tested on radial arm maze and active avoidance tasks. Weaver mice had incapacitating seizures while performing the radial arm maze task and were, therefore, removed from further testing. Staggerer mice displayed a significant deficit on both tasks compared to control mice. Homozygous reeler mice (rl/rl) also had a significant deficit on the active avoidance task compared to +/rl control mice but not significantly poorer than ichthyosis mice. However, their performance on the radial arm maze task, while initially poor, improved so that they performed the task similar to wild-type controls. Three of the reeler mice reached criterion for solving the radial arm maze task. None of the staggerer mice reached criterion. These data are discussed in terms of the value of using neurologically mutant mice in dissecting structural-functional relationships. It is suggested that the behavior of these mutants might point toward specific components of cerebellar involvement in behavioral acts.     

Acetylcholine release in the hippocampus and striatum during place and response training

These experiments examined the release of acetylcholine in the hippocampus and striatum when rats were trained, within single sessions, on place or response versions of food-rewarded mazes. Microdialysis samples of extra-cellular fluid were collected from the hippocampus and striatum at 5-min increments before, during, and after training. These samples were later analyzed for ACh content using HPLC methods. In Experiment 1, ACh release in both the hippocampus and striatum increased during training on both the place and response tasks. The magnitude of increase of training-related ACh release in the striatum was greater in rats trained on the response task than in rats trained on the place task, while the magnitude of ACh release in the hippocampus was comparable in the two tasks. Experiment 2 tested the possibility that the hippocampus was engaged and participated in learning the response task, as well as the place task, because of the availability of extra-maze cues. Rats were trained on a response version of a maze under either cue-rich or cue-poor conditions. The findings indicate that ACh release in the hippocampus increased similarly under both cue conditions, but declined during training on the cue-poor condition, when spatial processing by the hippocampus would not be suitable for solving the maze. In addition, high baseline levels of ACh release in the hippocampus predicted rapid learning in the cue-rich condition and slow learning in the cue-poor condition. These findings suggest that ACh release in the hippocampus augments response learning when extra-maze cues can be used to solve the maze but impairs response learning when extra-maze cues are not available for use in solving the maze.     

Spatial and nonspatial escape strategies in the Barnes maze

The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either with or without a discrete visible cue marking the location of the escape hole, which was either in a fixed or variable location across trials. In Experiment 2, all mice were trained with the discrete visible cue marking the target hole location. Two groups were identical to the cued-target groups from Experiment 1, with either fixed or variable escape locations. For these mice, the discrete cue either was the sole predictor of the target location or was perfectly confounded with the spatial extra-maze cues. The third group also used a cued variable target, but a curtain was drawn around the maze to prevent the use of spatial cues to guide navigation. Probe trials with all escape holes blocked were conducted to dissociate the use of spatial and discrete proximal cues. We conclude that the Barnes maze can be solved efficiently using spatial, visual cue, or serial-search strategies. However, mice showed a strong preference for using the distal room cues, even when a discrete visible cue clearly marked the escape location. Importantly, these data show that the cued-target control version of the Barnes maze as typically conducted does not dissociate spatial from nonspatial abilities.     

Landmark-based but not vestibular-based orientation elicits mossy fiber synaptogenesis in the mouse hippocampus

This study tries to shed light on the paradoxical finding that two inbred strains of mice C57BL/6 (C57) and DBA/2 (DBA), with differences in hippocampal function, perform similarly in the water maze (WM). Mice from both strains were trained on WM protocols permitting or preventing the use of vestibular signals. Hippocampal involvement in performance was then assessed by estimation of post-training mossy fiber (MF) synaptogenesis. We found that C57 and DBA mice performed similarly when both visual and vestibular information were available but only C57 mice exhibited new MF synapses. Disruption of vestibular inputs impaired performance in DBA mice but not in C57 mice which still exhibited a post-training increase of hippocampal MF synaptic terminals. This strain-specific dissociation indicates that DBA mice can navigate successfully by relying on vestibular signals without engaging their hippocampus. In contrast, vestibular signals are irrelevant for C57 mice since their suppression neither disrupts their behavior nor prevents the formation of new hippocampal synapses. These findings suggest some caution is required in considering performance on standard WM protocols as an index of hippocampus-based learning. Estimating the extent of post-training mossy fiber synaptogenesis would be helpful in solving this issue.     

Psychologie sociale et perception du temps : l'estimation temporelle des stimuli sociaux et émotionnels

Two experiments using a temporal bisection task investigated the influence of the social meaning of stimuli on the estimation of their duration. The results showed that: a) the duration of faces expressing diverse emotional states was overestimated relative to the duration of neutral faces; b) the duration of faces representing elderly people was underestimated relative to the duration of faces representing young people. In both cases, this influence was found to appear at the earliest stage of the estimation process, modulating the rhythm of the estimator's internal clock. In the discussion, we suggest three different perspectives to account for the observed link between social and temporal perception.     

Intraseptal Flumazenil Enhances, while Diazepam Binding Inhibitor Impairs, Performance in a Working Memory Task

GABA_A/benzodiazepine receptors in the medial septum modulate the activity of cholinergic neurons that innervate the hippocampus. Injection of benzodiazepine (BDZ) agonists into the medial septum impairs working memory performance and decreases high-affinity choline transport (HAChT) in the hippocampus. In contrast, intraseptal injection of the BDZ antagonist flumazenil increases HAChT and prevents the memory deficits induced by systemic BDZs. The present studies attempted to further characterize the behavioral effects of medial septal injections of flumazenil to an endogenous negative modulator of the GABA_A/BDZ receptor complex, diazepam binding inhibitor (DBI). Male Sprague–Dawley rats were cannulated to study the effects of intraseptal injections of these BDZ ligands on spatial working memory, anxiety-related behaviors in the elevated plus maze, and on general locomotor activity. Intraseptal flumazenil (10 nmol/0.5 μl) produced a delay-dependent enhancement of DNMTS performance after an 8-h, but not a 4-h, delay interval. This promnestic dose of flumazenil had no effect on locomotor activity and did not produce changes in measures of anxiety on the plus maze. Intraseptal injection of DBI had no effect (8 nmol/0.5 μl) or slightly impaired (4 nmol/0.5 μl) DNMTS radial maze performance following an 8-h delay, without producing changes in locomotion or plus maze behavior. These data demonstrate that flumazenil has a unique profile of activity in enhancing working memory following intraseptal injection.     

Sequential training in separate paradigms impairs second task consolidation and learning-associated modulations of hippocampal NCAM polysialylation.

As transient and time-dependent modulations of neural cell adhesion molecule polysialylation (NCAM PSA) are associated with morphofunctional change and required for the consolidation of spatial and nonspatial forms of learning, we determined the demands imposed on this system by sequential training in the Morris water maze followed by the passive avoidance paradigm. Animals trained in this manner had recall of the water maze but not the passive avoidance response as judged by their escape and avoidance latencies, respectively. Activation of NCAM PSA on dentate neurons at the 12-h post-training time suggested information processing; however, this was significantly less than that predicted for coincident acquisition of both tasks. When sequential training was separated by an interparadigm period of 2 h, an enduring NCAM PSA activation was observed which was indistinguishable from the sum of the expected activations for each individual task. These observations suggest that the NCAM PSA response may become saturated when alternate tasks are presented without an intervening period.     

Immediate reproduction of temporal information under four cognitive strategies

The main purpose was to determine the retention characteristics of temporal information when subjects experienced time under a retention interval of immediate reproduction and various cognitive strategies for time estimation. Four levels of cognitive strategy were used, viz., conscious, mental counting, counting aloud without auditory cues, and counting aloud with auditory cues. The latter three cognitive strategies were experimenter-defined, time-aiding techniques. Subjects were instructed to refrain from employing time-aiding techniques under a conscious cognitive strategy for time estimation. Visual durations of 1, 2, and 4 sec. were estimated by 12 subjects under the method of reproduction. Two measures of performance were computed, viz., variable and constant errors. The general conclusions were: (a) the effectiveness of mental counting, counting aloud without auditory cues, and counting aloud with auditory cues as cognitive strategies over conscious cognitive strategy in terms of variability depends on the duration used, and (b) in terms of accuracy and variability an increase in the number of cues under time-aiding techniques does not necessarily produce better performance.     

Within-trial dynamics of radial arm maze performance in rats

The behavior of rats while solving a 12-arm radial maze was investigated using measures of response bias, choice latencies, and behavioral organization. Response bias decreased as a function of choice number, while the amount of time spent on the center platform between choices increased substantially during the last few choices. This increase in time between choices was largely accounted for by increases in investigatory behavior in the area of the doors leading to the arms. These data indicate that the processes involved in radial maze performance change over the course of each trial. As the choice sequence progresses, there is an increasing reliance on the use of information in memory, and a corresponding decrease in the use of response algorithms. In addition, the mean time taken to run down the chosen arm was shorter for correct choices than for incorrect choices, suggesting that arms are sometimes chosen despite a lowered expectation of finding food.     

Spatial Learning by Rats across Visually Disconnected Environments

Two spatial tasks were designed to test specific properties of spatial representation in rats. In the first task, rats were trained to locate an escape hole at a fixed position in a visually homogeneous arena. This arena was connected with a periphery where a full view of the room environment existed. Therefore, rats were dependent on their memory trace of the previous position in the periphery to discriminate a position within the central region. Under these experimental conditions, the test animals showed a significant discrimination of the training position without a specific local view. In the second task, rats were trained in a radial maze consisting of tunnels that were transparent at their distal ends only. Because the central part of the maze was non-transparent, rats had to plan and execute appropriate trajectories without specific visual feedback from the environment. This situation was intended to encourage the reliance on prospective memory of the non-visited arms in selecting the following move. Our results show that acquisition performance was only slightly decreased compared to that shown in a completely transparent maze and considerably higher than in a translucent maze or in darkness. These two series of experiments indicate (1) that rats can learn about the relative position of different places with no common visual panorama, and (2) that they are able to plan and execute a sequence of visits to several places without direct visual feed-back about their relative position.     

Stimulus perseveration in a water maze following exposure to controllable and uncontrollable shock

When placed in a water-filled maze, mice display a pronounced preference for the illuminated over the nonilluminated arm of the maze. Exposure to inescapable shock increased the time spent in the illuminated arm of the maze, and decreased the frequency of entries into the nonilluminated arm. When animals that had received shock entered the nonilluminated arm they exhibited more activity per second than nonstressed animals. Controllability over the stressor enhanced the preference for the illuminated arm; however, the contribution of this variable was dependent on the number of shock trials mice received. Following 180 escapable or inescapable shock presentations the preference for the illuminated arm was enhanced. The propensity to approach the illuminated arm declined following a greater number (360) of escapable shock trials, while the preference for the illuminated arm did not decline in mice that received inescapable shock. Both escapable and inescapable shock were also found to produce a transient disruption of discrimination performance in a task where animals were required to emit a contraprepared response (swim to dark), whereas these treatments were without effect on performance of the highly prepared response of approaching the illuminated arm. It is provisionally suggested that enhancement of the perseveration represents an innate response to stressful stimuli, but as animals learn mastery over the response contingencies, the persistence in adopting such a response strategy wanes. Moreover, despite the differential effects of escapable and inescapable shock on the perseverative tendency, discrimination accuracy may not be differentially affected by these treatments in a task where acquisition progresses quickly and where explicit cues are associated with the correct and incorrect arms of the maze.     

Continuity in Representation Between Children and Adults: Arithmetic Knowledge Hinders Undergraduates' Algebraic Problem Solving

This study examined if solving arithmetic problems hinders undergraduates' accuracy on algebra problems. The hypothesis was that solving arithmetic problems would hinder accuracy because it activates an operational view of equations, even in educated adults who have years of experience with algebra. In three experiments, undergraduates (N = 184) solved addition facts or participated in one of several control conditions. Those who solved addition facts were less likely to solve prealgebra equations (e.g., 6 + 8 +4 = 7 + __) correctly under speeded conditions. In a fourth experiment, the negative effects of solving arithmetic problems extended to undergraduates (N = 74) solving algebra problems with no time pressure. Taken together, results suggest that arithmetic activates knowledge that hinders performance on algebra problems. Thus, an operational view of equations, which is prevalent in children, does not seem to be revised or abandoned, even after years of experience with algebra.     

Preserved spatial memory in old rats survives 10 months without training

Aged rats with extensive prior training on the radial maze retain the capacity for accurate spatial working memory (WM) for at least 3 months without practice. To investigate the temporal limits of this influence of prior experience we compared the reacquisition of spatial WM by a group of experienced 21.5-month-old rats to the original acquisition by naive 3-month-old rats. The aged rats had received 225 radial maze tests between 3 and 11 months of age. Despite 10 months without practice the old rats rapidly reacquired critical performance. Their reacquisition was markedly superior to original learning by the young rats, even when delays as long as 5 h were imposed between the rats' fourth and fifth choices during the daily tests in the eight-arm maze. Additional tests showed that neither young nor old rats employed a response strategy to maintain accurate spatial WM performance. Experience clearly confers long-lived protection against the otherwise deleterious effects of aging on spatial WM, but the mechanism by which this influence arises is unknown.     

心理性应激的时间加工进程:来自ERP的证据*

采用有时间压力的算术题目诱发被试的心理性应激体验,并用事件相关电位技术(ERP)探讨心理性应激发生时大脑神经活动的时程变化。行为数据结果发现有时间压力下被试的反应时更短;脑电数据结果发现有时间压力组的容易题目比无时间压力组的容易题目诱发出更大的N1峰值、更长的P2潜伏期和更大的P300波幅;有时间压力组的困难题目比无时间压力组的困难题目同样诱发出更大的N1峰值、更长的P2潜伏期和更大的P300波幅,但这种组别主效应仅表现在部分电极点上。该研究结果表明心理性应激增加了早期知觉加工的负载,导致知觉加工速度减慢,在信息加工后期阶段需要占用更多的认知资源。     

Effects of time pressure on strategy selection and strategy execution in forced choice tests

We examined the effects of cognitive load on the strategy selection in the forced choice test (FCT) when used to detect hidden crime knowledge. Examinees (N = 120) with and without concealed knowledge from a mock crime were subjected to an FCT either under standard circumstances or cognitive load. Cognitive load was implemented through time pressure. The FCT distinguished examinees with concealed knowledge from those without better than chance in both conditions, but the counterstrategies did not differ between conditions. Further investigation revealed that time pressure did affect examinees' ability to follow their intended counterstrategy to produce randomized test patterns, which constitutes an effective counterstrategy in the FCT. Hence, time pressure lowered the success rate of effective counterstrategies, but not their incident rates. Further disambiguation of various cognitive load manipulations and their effects on strategy selection and execution is needed.