Stimulus Detection Task Research Articles

Human Auditory Steady-State Response During General Anesthesia

The 40-Hz auditory steady-state evoked response (ASSR) is a sinusoidal electrical response of the brain to periodically presented auditory stimuli. It was recorded during anesthesia in 10 elective surgical patients to evaluate its usefulness as a measure of the level of consciousness. The anesthetic agents used were thiopental, fentanyl, and isoflurane with or without nitrous oxide. Recordings were carried out during the period before induction and during induction, surgical anesthesia, emergence, and recovery from anesthesia. The level of consciousness was measured with an auditory stimulus detection task. The electroencephalogram (EEG) was also recorded for comparison with the ASSR. The following indices were analyzed: total EEG power, relative power in the beta, alpha, theta, and delta frequency bands, and the median and spectral edge frequency. The amplitude of the ASSR was reduced significantly at the end of the induction period and decreased below noise levels during surgical anesthesia. It increased significantly during emergence and recovery. The amplitude during recovery remained significantly smaller than the preinduction values. The changes of the ASSR paralleled those of the level of consciousness. The EEG measurements were distorted by the presence of muscle artifacts that were prominent during emergence and recovery. The amplitude of the ASSR appears to provide a more reliable indicator of the level of consciousness than the EEG.

Parafoveal attention in congenitally deaf and hearing young adults

This reaction-time study compared the performance of 20 congenitally and profoundly deaf, and 20 hearing college students on a parafoveal stimulus detection task in which centrally presented prior cues varied in their informativeness about stimulus location. In one condition, subjects detected a parafoveally presented circle with no other information being present in the visual field. In another condition, spatially complex and task-irrelevant foveal information was present which the subjects were instructed to ignore. The results showed that although both deaf and hearing people utilized cues to direct attention to specific locations and had difficulty in ignoring foveal information, deaf people were more proficient in redirecting attention from one spatial location to another in the presence of irrelevant foveal information. These results suggest that differences exist in the development of attentional mechanisms in deaf and hearing people. Both groups showed an overall right visual-field advantage in stimulus detection which was attenuated when the irrelevant foveal information was present. These results suggest a left-hemisphere superiority for detection of parafoveally presented stimuli independent of cue informativeness for both groups.

Electrophysiological correlates of visual detection in the cat

Average evoked responses to near-threshold visual stimuli were recorded from 9 cats as they performed a stimulus detection task. The amplitude of response components in the optic tract and striate cortex was a logarithmic function of stimulus intensity. The amplitude of early response components in the lateral geniculate nucleus (LGN) and mesencephalic reticular formation (MRF) was predominantly a function of probability-of-seeing. Day to day variations in stimulus detectability were accompanied by corresponding changes in early response components at the LGN and MRF but not in responses in the optic tract and striate cortex. This indicates that a cat performing a stimulus detection task uses an early subcortical detecting system.