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Effects of caffeine on task switching were studied using ERPs in a cued task-switch paradigm. The need for advance preparation was manipulated by varying the number of task-set aspects that required switching. In a double-blind, within-subjects experiment, caffeine reduced shift costs compared to placebo. ERPs revealed a negative deflection developing within the preparatory interval, which was larger for shift than for repeat trials. Caffeine increased this shift-induced difference. Furthermore, shift costs increased as a function of the number of task-set features to be switched, but this pattern was not modulated by caffeine. The results suggest that caffeine improves task-switching performance by increasing general effects on task switching, related to task-nonspecific (rather than task-specific) anticipatory processes. Caffeine's actions may be mediated by dopaminergic changes in the striatum or anterior cingulate cortex. [ABSTRACT FROM AUTHOR]

Event-related potentials were recorded from 7- to 18-year-old children of alcoholics (COAs, n= 50) and age- and sex-matched control children ( n= 50) while they performed a visual selective attention task. The task was to attend selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. COAs manifested a smaller P3b amplitude to attended-target stimuli over the parietal and occipital scalp than did the controls. A more specific analysis indicated that both the attentional relevance and the target properties of the eliciting stimulus determined the observed P3b amplitude differences between COAs and controls. In contrast, no significant group differences were observed in attention-related earlier occurring event-related potential components, referred to as frontal selection positivfty, selection negativity, and N2b. These results represent neurophysiological evidence that COAs suffer from deficits at a late (semantic) level of visual selective information processing that are unlikely a consequence of deficits at earlier (sensory) levels of selective processing. The findings support the notion that a reduced visual P3b amplitude in COAs represents a high-level processing dysfunction indicating their increased vulnerability to alcoholism. [ABSTRACT FROM AUTHOR]

The mismatch negativity (MMN) event-related potential (ERP) component is an automatic, attention-independent brain response to auditory stimulus change, which has been reported to be smaller in alcoholics relative to nonalcoholic controls. To determine whether MMN decrements might be a trait marker of alcoholism that is also present in nonalcoholic individuals at high risk for developing alcoholism, we investigated MMN in 9-to 18-year-old children of alcoholics ( n= 20) and control children ( n= 20) in three different stimulus conditions using a passive auditory oddball paradigm. There were no statistically significant between-group differences observed in amplitude, scalp topography, and peak latency of MMN. These findings, if replicated, suggest that reported MMN decrements in alcoholics most likely represent a state marker, and not a trait marker, of alcoholism. Also, inasmuch as another ERP component, the P300, is attention-dependent and reported to be smaller in children of alcoholics, the present results implicate that deviations in attentive, but not in automatic, information processing are associated with alcoholism vulnerability. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effects of moderate amounts of caffeine on task switching and task maintenance using mixed-task (AABB) blocks, in which participants alternated predictably between two tasks, and single-task (AAAA, BBBB) blocks. Switch costs refer to longer reaction times (RT) on task switch trials (e.g. AB) compared to task-repeat trials (e.g. BB); mixing costs refer to longer RTs in task-repeat trials compared to single-task trials. In a double-blind, within-subjects experiment, two caffeine doses (3 and 5mg/kg body weight) and a placebo were administered to 18 coffee drinkers. Both caffeine doses reduced switch costs compared to placebo. Event-related brain potentials revealed a negative deflection developing within the preparatory interval, which was larger for switch than for repeat trials. Caffeine increased this switch-related difference. These results suggest that coffee consumption improves task-switching performance by enhancing anticipatory processing such as task set updating, presumably through the neurochemical effects of caffeine on the dopamine system. [Copyright &y& Elsevier]

Abstract: This study investigated the electrophysiological correlates of shifting, maintaining, and relaxing the focus of attention, using a symbolic cuing task. Cues and imperative stimuli were presented in rapid succession, and the ADJAR procedure was used to remove the contribution of event-related potential (ERP) activity associated with the imperative stimulus from the cue-related ERP waveforms. Initial analyses, comparing left and right attention-directing cues, replicated previous findings of early directing attention negativity (EDAN) and anterior directing attention negativity (ADAN) effects. To isolate ERP activity that is common to leftward and rightward attention shifts, the combined ERP activity elicited by attention-directing cues was compared to the ERP activity elicited by non-informative cues. This analysis revealed a strong and broadly distributed early positivity followed by a sustained central negativity, possibly reflecting the controlled orienting and subsequent maintenance of attentional focus. Finally, imperative stimuli preceded by non-informative cues were characterized by an enhanced posterior P2 effect, with a scalp distribution indicative of generators in visual areas. This result suggests a relatively late (re)activation in visual areas associated with the processing of stimuli that had not been cued in advance. [Copyright &y& Elsevier]

The medial frontal cortex, especially the anterior cingulate cortex (ACC), is involved in action monitoring. We studied the role of moderate amounts of caffeine in action monitoring as expressed by the error-related negativity (ERN), an event-related brain component that reflects ACC activity. In a double-blind, placebo-controlled, within-subjects experiment, two caffeine doses (3 and 5 mg/kg body weight) and a placebo were administered to habitual coffee drinkers. Compared with placebo, both caffeine doses enlarged the ERN. Amplitudes of the P2 and P3 components were not affected by caffeine. Thus, the enlarged ERN after caffeine reflects a specific effect on action monitoring. We conclude that consumption of a few cups of coffee strengthens central information processing, specifically the monitoring of ongoing cognitive processes for signs of erroneous outcomes. Brain areas related to action monitoring such as the ACC presumably mediate these caffeine effects. [Copyright &y& Elsevier]