Event-related potentials elicited by automatic targets: a dual-task analysis.

The role of limited capacity processes in the detection of automatic targets was investigated in a dual-task paradigm using both behavioral and event-related brain potential (ERP) measures. An automatic detection task was paired with another concurrent discrimination while the relative importance of each task was systematically varied. The resulting performance operating characteristic (POC) showed that both the speed and accuracy of automatic detection responses were affected by the allocation of attention. Reductions in the accuracy of each task were accompanied by reductions in the amplitude of a late-positive component of the ERP (P300). In addition, the latency of the P300 component elicited by automatic targets was increased in dual-task conditions. A comparison of behavioral and ERP measures suggested the involvement of two separate limited-capacity processes in automatic detection: one concerned with the formation of an episodic representation of target occurrence and the other with the execution of rapid motor responses.

The component structure of event-related slow potentials: task, ISI, and warning stimulus effects on the 'E' wave.

Two experiments were conducted to investigate the role of task variables and ISI length on the late component of the event-related slow potential (ERSP) recorded during various two-stimulus anticipation tasks. In the first experiment, a two-component ERSP was observed during short (1 sec) and long (4 sec) ISI conditions. The first component was generally Fz dominant and independent of task variables. The second component was generally Cz dominant and most prominent when an immediate motor response was required. A second experiment was successful in eliciting large second ERSP components even in the absence of response requirements. In this experiment, the topography of the second component was not exclusively Cz dominant; rather, it was task dependent, and achieved Fz dominance under delayed-response conditions. Heart rate, monitored concurrently with the EEG, also reflected the change in experimental conditions by the enhancement of a mid-ISI acceleratory component. The data are discussed with respect to a multiple-component model of slow potential activity during periods in which subjects anticipate significant events.

Anticipatory pleasure deficit in subjects reporting physical anhedonia: slow cortical evidence.

Slow cortical and heart rate responses were recorded from anhedonic and normal control subjects during a two-stimulus anticipation paradigm. Subjects were chosen for participation in the experiment based on their scores on the Physical Anhedonia Scale developed by Chapman, Chapman and Raulin (1976). During the procedure, auditory warning stimuli were delivered which informed subjects that a visual stimulus (color slide) would follow shortly and specified the category of the slide (neutral or high-interest) which was to be presented. Results of this investigation revealed that anhedonic subjects showed less differential physiological responsivity while anticipating high and low interest stimuli than did normal controls. This was most striking in the slow cortical response (CNV) which appears particularly sensitive to such motivational and/or attentional manipulations. The data are discussed with respect to emotion and psychopathology.