P300 and allocation of attention in dual-tasks.

P300 in dual-tasks has been reported to be distributed reciprocally across the tasks, i.e. larger P300 associated with one task implies smaller P300 associated with the other (Wickens et al., 1983; Sirevääg et al., 1989). In these studies, however, the dual-tasks stimuli were either presented simultaneously, precluding a direct, within-trial assessment of relative magnitudes of P300, or they were separated by intervals of 1 s or more, thereby minimizing overlap of the ERP epochs, but at the cost of reduced competition for shared processing resources. The present experiment used an inter-stimulus interval of 400 ms between the auditory (tones) and visual (colored LEDs) stimuli that defined the dual-task and found that, when deviant tones elicited a prominent auditory P300, they were followed by a greatly reduced P300 for the deviant LED. The findings were interpreted from viewpoints that considered the effects of neural inhibition versus neural recovery cycles on the amplitude of P300.

Patient satisfaction and the LoFric catheter for clean intermittent catheterization.

A pilot study was initiated to determine patient satisfaction with the use of a newly available pre-lubricated, hydrophilic, disposable LoFric* catheter for clean intermittent catheterization. The study population consisted of 16 new patients and 25 experienced with clean intermittent catheterization. Patients were asked questions regarding convenience, ease of handling, comfort and general opinion of the catheters. Four new and 8 experienced patients dropped out of the study. Of the new patients who completed the study 75% found clean intermittent catheterization less troublesome than expected and all wish to continue using the catheter. Of the experienced patients 81% had a more favorable general opinion of the disposable than of the previous catheter, 81% found the disposable catheter to be more convenient and 88% thought it was easier to handle. It appears that most people will be satisfied with the disposable catheter and will prefer it as an alternative to a plastic catheter with lubrication applied by the patient.

Frequency and phase characteristics of slow cortical potentials preceding bimanual coordination.

The aim of the present study was to derive quantities which relate behavioral and neurophysiological levels of observation during a bimanual coordination task. We recorded the scalp electroencephalographic (EEG) signal preceding a sequence of 4 bimanual finger flexions of varying response rates in 12 subjects. A slow negative-going Bereitschaftspotential (BP) displayed larger mean amplitudes and earlier onset times for the faster required response rates. The amplitude of the BP was also larger for electrode locations contralateral to the side initiating the behavioral response. A Fourier transform showed two predominant frequencies (0.5 and 2.0 Hz) to be amplitude modulated as a function of the required response rate in addition to increased power on the contralateral side of the finger initiating the response. A measure of the phase relationship between the left (C3) and right (C4) hemispheres of the fronto-central cortex at each of these spectral frequencies was calculated as well as the variance in this measure and found to correspond closely to the variance in inter-response times derived from the subjects' movements. These findings indicate that changes in the stability and rate of a patterned movement are generally preceded by similar changes in the stability and amplitude of components observed on the neurophysiological level.

Effects of preparatory set and task demands on auditory event-related potentials.

Different instructional sets for moderate vs. high response speeds were given in a visual letter-matching task. On 50 percent of the trials an auditory probe requiring a simple RT response was presented in one of four temporal locations within the ongoing visual task. Probe locations were selected to maximize differences in the processing demands of the dual, auditory-visual task (see Posner and Boies, 1971). The N100 of the event-related potential associated with the auditory probe was larger under the high response speed set than under the moderate set, regardless of probe location. P300 amplitude was also greater under the high speed set relative to the moderate set but only when the task demands were high. The results were interpreted in terms of the interaction between arousal and task demands and a neural inhibition model of the P300 was discussed.