Cédric A. Bouquet

Processing speed and executive functions in cognitive aging: How to disentangle their mutual relationship?

The processing-speedtheory and the prefrontal-executivetheory are competing theories of cognitive aging. Here we used a theoretically and methodologically-driven framework to investigate the relationships among measures classically used to assess these two theoretical constructs. Twenty-eight young adults (18-32 years) and 39 healthy older adults (65-80 years) performed a battery of nine neuropsychological and experimental tasks assessing three executive function (EF) components: Inhibition, Updating, and Shifting. Rate of information processing was evaluated via three different experimental and psychometric tests. Partial correlations analyses suggested that 2-Choice Reaction Time (CRT) performance is a more pure measure of processing speed than Digit Symbol Substitution Test (DSST) performance in the elderly. Hierarchical regression analyses showed that, although measures of processing speed and EF components share mutual variance, each measure was independently affected by chronological age. The unique adverse effect of age was more important for processing speed than for EF. The processing-speed theory and the prefrontal-executive theory of cognitive aging were shown not to be mutually exclusive but share mutual variance. This implies the need to control for their mutual relationship before examining their unique potential role in the explanation of age-related cognitive declines. Caution has still to be taken concerning the tasks used to evaluate these theoretical constructs.

Investigation of Supervisory Attentional System Functions in Patients With Parkinson’s Disease Using the Hayling Task

The study explored executive dysfunction in Parkinson’s disease (PD) by using the Hayling test (Burgess & Shallice, 1996) and verbal fluency tasks (VFTs). PD patients showed longer response latencies than controls in both parts of the Hayling test (Section A/automatic and Section B/inhibition). Patients and controls did not differ in the proportion of errors or number of responses that revealed the use of strategies. PD patients also showed verbal fluency deficits in semantic, phonemic, and alternating fluency tasks. These impairments on tests known to be sensitive to frontal lobe dysfunction confirm executive or Supervisory Attentional System (Norman & Shallice, 1986) deficits and further indicate suppression skills impairments in PD.

Long-lasting effects of performance-contingent unconscious and conscious reward incentives during cued task-switching

Motivation is often thought to interact consciously with executive control, although recent studies have indicated that motivation can also be unconscious. To date, however, the effects of unconscious motivation on high-order executive control functions have not been explored. Only a few studies using subliminal stimuli (i.e., those not related to motivation, such as an arrow to prime a response) have reported short-lived effects on high-order executive control functions. Here, building on research on unconscious motivation, in which a behavior of perseverance is induced to attain a goal, we hypothesized that subliminal motivation can have long-lasting effects on executive control processes. We investigated the impact of unconscious/conscious monetary reward incentives on evoked potentials and neural activity dynamics during cued task-switching performance. Participants performed long runs of task-switching. At the beginning of each run, a reward (50 cents or 1 cent) was displayed, either subliminally or supraliminally. Participants earned the reward contingent upon their correct responses to each trial of the run. A higher percentage of runs was achieved with higher (conscious and unconscious) than lower rewards, indicating that unconscious high rewards have long-lasting behavioral effects. Event-related potential (ERP) results indicated that unconscious and conscious rewards influenced preparatory effort in task preparation, as suggested by a greater fronto-central contingent negative variation (CNV) starting at cue-onset. However, a greater parietal P3 associated with better reaction times (RTs) was observed only under conditions of conscious high reward, suggesting a larger amount of working memory invested during task performance. Together, these results indicate that unconscious and conscious motivations are similar at early stages of task-switching preparation but differ during task performance.

The Intention Superiority Effect in Motor Skill Learning.

Three experiments were conducted to determine if the intention to perform motor sequences in the future results in similar patterns of activation and inhibition as observed for verbal scripts. In Experiments 1 and 2, intention was induced by informing one group that they would be tested on the tasks following acquisition; the other group was not informed of the retention test. Recognition tests administered prior to and after the retention test indicated a strong intention superiority effect. However, intention instructions provided either at the end of acquisition (Experiment 1) or before acquisition (Experiment 2) failed to impact acquisition or retention performance of the motor sequences, but did influence the latency of responding on the retention test. Experiment 3 was designed to replicate the results of Experiments 1 and 2 using a within-subjects design and extend these findings to observation. The results indicated that intention instructions resulted in a strong intention superiority effect for both the physical and observational practice participants, but the performance on the intentional tasks was enhanced only for the observational practice group.

Motor Contagion Goal-Directed Actions Are More Contagious than Non-Goal-Directed Actions

Recent theories posit a mirror-matching system mapping observed actions onto ones own motor system. Determining whether this system makes a distinction between goal-directed and non-goal-directed actions is crucial for the understanding of its function. The present study tested whether motor interference between observed and executed actions, which is thought to be an index of perceptual-motor matching, depends on the presence of goals in the observed action. Participants executed sinusoidal arm movements while observing a video of another person making similar or different movements. In certain conditions, elements representing goals for the observed movement were superimposed on the video displays. Overall, observing an incongruent movement interfered with movement execution. This interference was markedly increased when the observed incongruent movement was directed toward a visible goal, suggesting a greater perceptual-motor matching during observation of goal-directed versus non-goal-directed actions. This finding supports an action-reconstruction model of mirror system function rather than the traditional direct-matching model.

Number generation bias after action observation

Recent studies have demonstrated that conceptual and abstract knowledge could rely on and could be influenced by sensory-motor processing of usual goal-directed actions. In line with this, interactions have been reported between number magnitude and finger grip with, for example, small-magnitude numbers priming grip closure and large-magnitude numbers priming grip aperture. Here, we assessed whether observing a closing or opening grip was able to influence the magnitude of the numbers produced in a random number generation task, and we tested whether this effect was specific to biological hand actions by using non-biological fake hands with the same closure or aperture amplitude. The participants were asked to produce as randomly as possible numbers between 1 and 10 after they observed a change in posture (i.e. grip closing or grip opening) or in colour (i.e. red or blue hand). The results revealed that the participants produced more often small numbers than large ones after observing a grip closing, whereas they produced equally often small and large numbers after observing a grip opening or colour changes. Importantly, this effect was only present for the biological hands but not for the non-biological fake hands. This finding demonstrates that observing a biological grip closing conveys small-magnitude information, which, in turn, influences the mental selection of a numerical response. We discuss our results in the light of the internal random generator process proposed in the domain of numerical cognition and argue that number semantics is stored with a code governed by sensory-motor mechanisms.

Experience with novel actions modulates frontal alpha EEG desynchronization

There is growing interest in the effects of experience on the neural processes linking action execution and action perception. We tested whether experience with unfamiliar actions can alter desynchronization of alpha-range power in the EEG upon re-observation of those actions. In a training session, participants (N=21) watched videos of novel drawing movements. Half of the movements were imitated after each viewing, and half of the movements were seen but not imitated, thus forming two training conditions: visual plus motor experience (V+M), and visual experience only (VO). In a testing session the next day, participants were shown the same videos of both sets of movements, and were also shown a third, completely novel, set of movements. Imitative performance was better for both training conditions than for novel actions. Event-related EEG desynchronization in the upper alpha band during action observation differed between conditions at frontal electrode sites, with novel actions being associated with less frontal desynchronization compared to V+M and VO actions. Differences between conditions were not noted over other regions. This suggests that moderate amounts of initial experience with novel actions can alter the neural processing of these actions when viewed again, particularly over frontal regions.

2010 Special Issue: Motor contagion in young children: Exploring social influences on perception-action coupling

Human development occurs in a social environment in which learning is tightly coupled to the behavior of other supportive humans. One aspect of this coupling may occur through motor contagion, in which observing the actions of other people is associated with the activation of related motor representations. In order to explore the overlap between action observation and action execution in early childhood, a novel task was developed in which 4-year-old children were instructed to move a stylus on a graphics tablet in the presence of a background video which showed a model moving her arm in a direction that was either congruent or incongruent with the instructed axis of the childs stylus movements. The presence of incongruent background movements was associated with a significant interference effect on childrens stylus movements. This interference effect was stronger when the background movements were performed by a same-age peer rather than by an adult. It is suggested that early childhood is a particularly interesting age period to study motor contagion, since the transition from infancy to childhood involves concurrent changes in cognitive control and in the ability to flexibly decouple perception and action. The examination of motor contagion provides an important consideration of social influences on cognitive control in early childhood--influences that have been somewhat neglected in the developmental literature on the related construct of executive functioning.

Does motor interference arise from mirror system activation? The effect of prior visuo-motor practice on automatic imitation

Action perception may involve a mirror-matching system, such that observed actions are mapped onto the observer’s own motor representations. The strength of such mirror system activation should depend on an individual’s experience with the observed action. The motor interference effect, where an observed action interferes with a concurrently executed incongruent action, is thought to arise from mirror system activation. However, this view was recently challenged. If motor interference arises from mirror system activation, this effect should be sensitive to prior sensorimotor experience with the observed action. To test this prediction, we measured motor interference in two groups of participants observing the same incongruent movements. One group had received brief visuo-motor practice with the observed incongruent action, but not the other group. Action observation induced a larger motor interference in participants who had practiced the observed action. This result thus supports a mirror system account of motor interference.

Somatosensory experiences with action modulate alpha and beta power during subsequent action observation

How does prior experience with action change how we perceive a similar action performed by someone else? Previous research has examined the role of sensorimotor and visual experiences in action mirroring during subsequent observation, but the contribution of somatosensory experiences to this effect has not been adequately examined. The current study tests whether prior somatosensory stimulation experienced during action production modulates brain activity during observation of similar actions being performed by others. Specifically, changes in alpha- and beta-range oscillations in the electroencephalogram (EEG) during observation of reaching actions were examined in relation to the observers own prior experience of somatosensory stimulation while carrying out similar actions. Analyses revealed that alpha power over central electrodes was significantly decreased during observation of an action expected to result in somatosensory stimulation. Conversely, beta power was increased when an observed action was expected to result in somatosensory stimulation. These results suggest that somatosensory experiences may uniquely contribute to the way in which we process other peoples actions.