Auditory evoked potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips in the other ear. The negative component of the evoked potential peaking at 80 to 110 milliseconds was substantially larger for the attended tones. This negative component indexed a stimulus set mode of selective attention toward the tone pips in one ear. A late positive component peaking at 250 to 400 milliseconds reflected the response set established to recognize infrequent, higher pitched tone pips in the attended series.

We measured digit span (DS) in two experiments that used computerized presentation of randomized auditory digits with performance-adapted list length adjustment. A new mean span (MS) metric of DS was developed that showed reduced variance, improved test-retest reliability, and higher correlations with the results of other neuropsychological test results when compared to traditional DS measures. The MS metric also enhanced the sensitivity of forward versus backward span comparisons, enabled the development of normative performance criteria with sub-digit precision, and elucidated changes in DS performance with age- and education level. Computerized stimulus delivery and improved scoring metrics significantly enhance the precision of DS assessments of short-term verbal memory.

The sensitivity of the scalp-recorded, auditory evoked potential to selective attention was examined while subjects monitored one of two dichotically presented speech passages for content. Evoked potentials were elicited to irrelevant probe stimuli (vowel sounds) embedded in both the right-and the leftear's message. The amplitude of the evoked potential was larger to probe stimuli embedded in the attended message than to probe stimuli in the unattended message. Recall performance was unaffected by the presence of the probes. The results are interpreted as supporting the hypothesis that this evoked potential sensitivity reflects an initial "input selection" stage of attention.

We used an event-related brain potential (ERP) technique developed by Hillyard et al. (1973) to test abilities to attenuate irrelevant stimuli and to detect target stimuli. Subjects, 12 healthy old (80.3 years) and 12 healthy young adults (22.0 years), heard 1500 Hz tones in one ear and 800 Hz tones in the other ear. Infrequently, the pitch of either tone was raised. During one run, infrequent tones in the right ear were targets, and in the other run those in the left ear were targets. Subjects counted targets. For both groups, an early component of the ERP (N1) was larger to tones in the attended ear than in the unattended ear, and a later component (P3) was largest to the target. This suggests that both groups can attenuate irrelevant stimuli and can use stimulus probability information in this task. That P3 was later for old subjects suggests that they take longer to decide stimulus relevance.

No abstract