Un exercice de repérage de signaux discontinus a été employé pour évaluer le processus de planification du mouvement (relié aux paramètres de direction et d'amplitude) comme source du ralentissement de l'initiation et de la production du mouvement chez les personnes âgées. Les personnes âgées ont démontré des temps de réaction et de mouvement plus lents, cette lenteur variant en fonction de la quantité d'informations traitées pour accomplir le mouvement. Cependant, les personnes âgées ont semblé aussi capables que des individus plus jeunes de corriger des erreurs imprévues de mouvement. Les données suggèrent que, bien que le processus de sélection du mouvement puisse constituer un facteur qui contribue au ralentissement chez les personnes âgées, l'identification de paramètres spécifiques du mouvement peut s'avérer plus importante dans l'accomplissement de certains mouvements que les quelques déficits généralisés associés au vieillissement.

The ingestion of a glucose-containing drink has been shown to improve cognitive performance, particularly memory functioning. However, it remains unclear as to the extent to which task domain and task difficulty moderate the glucose enhancement effect. The aim of this research was to determine whether boosts in performance are restricted to particular classes of memory (episodic v. semantic) or to tasks of considerable cognitive load. A repeated measures (25g glucose v saccharin), counterbalanced, double-blind design was used with younger and older adults. Participants performed a battery of episodic (e.g. paired associate learning) and semantic memory (e.g. category verification) tasks under low and high cognitive load. Electrophysiological measures (heart rate and galvanic skin response) of arousal and mental effort were also gathered. The results indicated that whilst glucose appeared to aid episodic remembering, cognitive load did not exaggerate the facilitative effect. For semantic memory, there was little evidence to suggest that glucose can boost semantic memory retrieval even when the load was manipulated. One exception was that glucose facilitated performance during the difficult category fluency task. Regardless, the present findings are consistent with the domain-specific account in which glucose acts primarily on the hippocampal region, which is known to support episodic memory. The possible contribution of the hippocampus in semantic memory processing is also discussed.

The present review focuses on the utility of the amplitude of P3 of as a measure of processing capacity and mental workload. The paper starts with a brief outline of the conceptual framework underlying the relationship between P3 amplitude and task demands, and the cognitive task manipulations that determine demands on capacity. P3 amplitude results are then discussed on the basis of an extensive review of the relevant literature. It is concluded that although it has often been assumed that P3 amplitude depends on the capacity for processing task relevant stimuli, the utility of P3 amplitude as a sensitive and diagnostic measure of processing capacity remains limited. The major factor that prompts this conclusion is that the two principal task variables that have been used to manipulate capacity allocation, namely task difficulty and task emphasis, have opposite effects on the amplitude of P3. I suggest that this is because, in many tasks, an increase in difficulty transforms the structure or actual content of the flow of information in the processing systems, thereby interfering with the very processes that underlie P3 generation. Finally, in an attempt to theoretically integrate the results of the reviewed studies, it is proposed that P3 amplitude reflects activation of elements in a event-categorization network that is controlled by the joint operation of attention and working memory.

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female participants (n = 20/group) with both auditory and visual stimulus discrimination tasks that varied systematically in difficulty. P300 amplitude was larger across all task conditions for left- than for right-handed participants at anterior and central electrode sites. P300 latency was shorter across all task conditions for left- than for right-handers. Task difficulty did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males than for females. When considered in the context of corpus callosal size differences for left- versus right-handed and male versus female participants, the findings suggest that the P300 reflects callosal size and interhemispheric transmission efficacy.

P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.