Search PubMed⌕ Search

Biomedical subjects

R Parasuraman

Publications and source records attributed to R Parasuraman.

50 records · Page 3Linked to original sources
PubMed1983

Visual sustained attention: image degradation produces rapid sensitivity decrement over time.

Perceptual sensitivity to a visual target presented in a random continuous sequence of targets and nontargets decreased rapidly over time when stimuli were highly degraded visually but not when moderately degraded or undegraded. Large declines in sensitivity, independent of changes in response criterion, were found after only 5 minutes of observation. These rapid decrements of sensitivity to degraded targets seem to result from demands on the limited capacity of visual attention.

Adolescent↗
PubMed1980

Brain events underlying detection and recognition of weak sensory signals.

Through the use of a quantitative extension of signal detection theory, the brain events associated with the detection and recognition of weak acoustic signals were examined by recording brain event-related potentials. The early N100 componenet of the event-related potential varied only with detection, whereas the late P300 component varied with both detection and recognition. P300 amplitude accurately predicted recognition performance on a trial-by-trial basis. The results suggest that detection and recognition are partially concurrent processes in perception and demonstrate that the electrocortical events occurring during the perception of sensory stimuli are closely associated with both detection and recognition of these stimuli by the nervous system.

Acoustic Stimulation↗
PubMed1979

Memory load and event rate control sensitivity decrements in sustained attention.

The capacity to sustain attention at an efficient level deteriorates over time in discrimination and monitoring tasks. This "vigilance decrement" results from a decrement in perceptual sensitivity only if (i) target discrimination loads memory and (ii) stimulus events occur rapidly; otherwise, the decrement reflects temporal changes in response criteria. These results provide a basis for distinguishing between the perceptual and response processes underlying the vigilance decrement that may be generalized across a range of tasks.

Attention↗
PubMed1976

Decision theory analysis of response latencies in vigilance.

In two separate experiments, the latencies associated with all four categories of response (correct detections, false alarms, correct rejections, and omissions) were recorded during the performance of a 45-min. visual monitoring task. In the first experiment, concerned primarily with criterion changes in vigilance, signal probability was manipulated. The second experiment was concerned with sensitivity changes resulting from changes in event rate. In the first experiment, latencies associated with correct detections and false alarms increased, whereas those associated with correct rejections and omission errors decreased, with an increase in criterion. In the second experiment, a reduction in sensitivity associated with an increased event rate exerted significant and opposing effects on latencies of responses to signals (correct detections and omissions) while leaving the latencies of responses to nonsignals (correct rejections and false alarms) unchanged. In both experiments, it was observed that while the latencies associated with positive responses increased with time on task, the latencies of negative responses decreased with time. These results are consistent with the predictions of a decision theory model for response latency extended from signal detection theory, which assumes an inverse relation between response latency and distance from the criterion; A decision theory analysis thus enables the interpretation of both detectability and latency measures of vigilance performance within the same theoretical framework.

Adolescent↗
PubMed1975

Response bias and physiological reactivity.

Sixteen Ss were selected from a group of 30 adult males for low and high levels of physiological reactivity, as defined by several measures of electrodermal activity (EDA). They were subsequently tested on two occasions on a tone discrimination task in which confidence ratings were required. High EDA Ss discriminated a significantly greater number of tones, but this apparent superiority was not due to their superior sensitivity, but to a greater bias towards responding positively to signals. The results were discussed in relation to possible mechanisms mediating individual differences in response bias and physiological reactivity.

Arousal↗
PubMedDate not supplied

Effects of information processing demands on slow negative shift latencies and N100 amplitude in selective and divided attention.

The influence of information processing demands on auditory event-related potentials (ERPs) in selective and divided attention was examined by varying the stimulation rate and target difficulty in a two-channel discrimination task. Subjects were required to detect targets in either one or both ears (channels) in a series of tones presented randomly to both ears. The amplitude of the N100 component (latency 80-140 msec) of the ERP to all stimuli in an attended channel was greater if attention was focused on that channel that if it was directed to the opposite channel. N100 amplitude was also reduced in divided attention compared to focused attention. In general, these effects were obtained only if the stimulation rate was high and/or targets were difficult to detect. However, these effects of attention modulated an underlying slow negative shift (SNS) rather than N100 directly. The onset and peak latencies of the SNS were strongly dependent on the processing demands of the task. The results show that the temporal relationship of the SNS to the N100 component is the principal factor responsible for variations in the effects of attention on the ERP with changes in information processing demands. The relationship between these ERP components and resource allocation theories of attention is discussed.

Adolescent↗
PubMedDate not supplied

Dose-related effects of ethanol on visual sustained attention and event-related potentials.

The effects of acute ethanol intoxication on visual sustained attention were investigated in male social drinkers. Four doses ranging from 0 (placebo) to 1.05 g/kg lean body weight, with periodic maintenance dosing of 0.12 g/kg, were given in separate sessions. The task required subjects to monitor a series of blurred digits presented singly at a rate of one per sec and to respond to occasional (p = 0.25) target digits with a speeded button press. Detection performance deteriorated as a function of both dose and time on task. In addition, the factors of dose and time on task interacted to produce a more rapid performance decrement under the higher doses. Early event-related potential (ERP) components (N1 and P2) were not greatly affected, suggesting that the performance decrement reflects central rather than peripheral factors. Later components related to cognitive appraisal processes (N2, P3), in contrast, varied in both amplitude and latency. Ethanol yielded dose-related delays in N2 and P3 latencies, which paralleled reaction time increases. The amplitude of N2 also decreased over time on task, and P3 amplitude decreased both as a function of dose and time on task. ERP and performance data were interpreted as demonstrating an adverse effect of ethanol on central processing capacity.

Adult↗
PubMedDate not supplied

Overall vigilance and sustained attention decrements in healthy aging.

Age differences in sustained attention were investigated using a high-event rate digit-discrimination task at 6 levels of stimulus degradation (lasting 8.1 min each). Twenty-one young, 21 middle-aged, and 20 old healthy subjects were studied. Overall sensitivity (d') was equivalent in all groups. Although all subjects showed a sensitivity decrement over blocks, there were no age-related differences in sustained attention capacity. All subjects had larger decrements in d' over blocks at higher degradation levels. However, the performance decrement at higher degradation levels was equivalent in all groups, indicating similar decrement rates in sensitivity with increasing demands on effortful processing. These results indicate that overall levels of vigilance and the ability to sustain attention over time are equivalent in all groups under conditions requiring both automatic (low-degradation) and effortful (high-degradation) stimulus processing.

Adult↗
PubMedDate not supplied

Aging and cognitive vigilance: effects of spatial uncertainty and event rate.

Age-related differences in cognitive vigilance were examined in a task requiring identification of a target (a lowercase letter) presented at three levels of spatial uncertainty (low, moderate, and high) and in the context of a low or high event rate. Thirty-six young (18-24 years) and 36 older (60-74 years) adults participated in 30-min vigilance sessions. Increased spatial uncertainty decreased target detection rate and d' to a greater extent in older adults than in young adults. No age differences were obtained for the low-spatial-uncertainty condition. The vigilance decrement--the decline in detection rate over time--was magnified when event rate was high and when spatial uncertainty was high. The results suggest that cognitive vigilance is age sensitive when demands on visual attention capacity are increased by high event rate or spatial uncertainty.

Adolescent↗