Age-related changes in processing auditory stimuli during visual attention: evidence for deficits in inhibitory control and sensory memory.

Age-related declines in attention and cognition have been associated with a difficulty in inhibiting the processing of task-irrelevant information (i.e., the inhibitory deficit hypothesis). However, evidence supporting the inhibitory deficit hypothesis remains equivocal, in part because of complexities in examining the processing of irrelevant stimuli using purely behavioral techniques. The effects of age on the processing of task-irrelevant stimuli were examined using scalp-recorded event-related brain potentials. Participants performed a visual discrimination task while standard and deviant auditory stimuli were presented in the background. Deviant auditory stimuli generated a mismatch negativity (MMN) wave that decreased with age, in part because of an age-related enhancement in sensory-evoked responses. The age-related changes in processing task-irrelevant auditory stimuli are consistent with the inhibitory deficit hypothesis and suggest that impaired inhibitory control of sensory input may play a role in the age-related declines in performance during selective attention tasks.     

Concurrent performances: reinforcement by different doses of intravenous cocaine in rhesus monkeys

Different doses of intravenous cocaine reinforced the lever pressing of rhesus monkeys under two-lever concurrent or concurrent-chain schedules. Under the concurrent procedure, responding produced drug reinforcers arranged according to independent variable-interval 1-min schedules. Under the concurrent-chain procedure, responding in the variable-interval link led to one of two mutually exclusive, equal-valued, fixed-ratio links; completion of the ratio produced a drug reinforcer. Under both procedures, responding on one lever produced a constant dose of 0.05 or 0.1 mg/kg/injection, while on the other lever, dose was systematically varied within a range of 0.013 to 0.8 mg/kg/injection. Preference, indicated by relative response frequency on the variable-dose lever during the variable-interval link, was always for the larger of the doses. Relative response frequencies on the variable-dose lever roughly matched relative drug intake (mg/kg of drug obtained on variable lever divided by mg/kg of drug obtained on both levers). For many dose comparisons, responding occurred and reinforcers were obtained almost exclusively on the preferred lever. Overall variable-interval rates generally were lower than with other reinforcers, and these low rates, under the experimental conditions, may have occasioned the exclusive preferences.     

Repression-sensitization and nonverbal expressiveness

Investigated the relationship of status on Byrne's repression-sensitization dimension to novel measures of nonverbal' expressiveness under stress and nonstress conditions, where subjects' perceptions of the purpose of the dependent measures were varied. Forty subjects were divided into sensitizer and repressor groups on the basis of Repression-Sensitization (R-S) scores. Subjects viewed either an anxiety-producing industrial accident film or a control film. Subjects were then told that the purpose of subsequent testing was either the assessment of creativity or of personality, as measured by a new projective test. The 2 X 2 X 2 factorial design enabled the investigation of predictions based on ego-defensive interpretations of repression-sensitization and Lefcourt's "attitude towards emotionality" view. Although the study failed to provide strong support for either interpretation in full, the data were viewed as reconcilable with Lefcourt's theory where repressors, but not sensitizers, are-concerned.     

Maintenance of fluency: A review

Three purposes for writing this paper are: to review specific work done on the maintenance of fluency in the post-treatment environment, to abstract and discuss pertinent issues in maintenance, and to present several speculative positions which might account for the relapse phenomenon and stimulate further research.     

Association between dyads and correct responses on the Paced Auditory Serial Addition Task (PASAT)

The sensitivity of the Paced Auditory Serial Addition Task (PASAT) to working memory deficits may be enhanced by examining "dyads" (i.e., correct responses immediately preceded by a correct response) as a complement to the traditional total correct summary score. In a sample of 397 mostly African American (79%) healthy adults, total dyad and total correct scores were highly correlated (r = .96, p < .001); however, the magnitude of this association diminished in faster stimulus presentation trials, particularly among participants with impaired working memory abilities.