Biomedical subjects

A Kingstone

Publications and source records attributed to A Kingstone.

21 records · Page 2Linked to original sources

PubMed1993

Visual offsets facilitate saccadic latency: does predisengagement of visuospatial attention mediate this gap effect?

Saccadic reaction time (RT) is reduced when a fixation stimulus is extinguished 200 ms before a target appears. An attentional predisengagement theory (APT) may explain this gap effect: When covert attention is engaged (e.g., on fixation), the saccadic system is inhibited and RT is delayed; when the attended stimulus is extinguished, attention is disengaged, the inhibition is removed, and RT is facilitated. In 3 experiments covert attention was endogenously or exogenously cued to an object on the vertical meridian. Onset of a saccadic target on the horizontal meridian could be preceded by the offset of an attended or unattended object. Contrary to APT, RTs were identical after attended and unattended offsets. Results suggest that the gap effect has 2 components, and covert visual attention plays no role. One component is motor system preparation; the other is a fixation offset effect specific to the oculomotor system.

Attention↗

PubMed1993

What are human express saccades?

When a fixation point is removed 200 msec prior to target onset (the gap condition), human subjects are said to produce eye movements that have a short latency (80-120 msec), that form the early peak of a bimodal latency distribution, and that have been labeled "human express saccades" (see, e.g., Fischer, 1987; Fischer & Breitmeyer, 1987; Fischer & Ramsperger, 1984, 1986). In three experiments, we sought to obtain this express saccade diagnostic pattern in the gap condition. We orthogonally combined target location predictability with the presence versus absence of catch trials (Experiment 1). When target location was fixed and catch trials were not used, we found mostly anticipations. In the remaining conditions, where responses were under stimulus control, bimodality was not frequently observed, and, whether it was or not, latencies were not in the express saccade range. Using random target locations, we then varied stimulus luminance and the mode of stimulus presentation (LEDs vs. oscilloscope) in the gap and overlap (fixation is not removed) conditions (Experiment 2). Bimodality was rarely observed, the gap effect (overlap minus gap reaction time) was additive with luminance, and only the brightest targets elicited saccades in the express range. When fixed locations and no catch trials were combined with latency feedback (Experiment 3), we observed many responses in the express saccade range and some evidence for bimodality, but the sudden introduction of catch trials revealed that many early responses were not under stimulus control. Humans can make stimulus-controlled saccades that are initiated very rapidly (80-120 msec), but unless catch trials or choice reaction time is used, it is not possible to distinguish such saccades from anticipatory responses that are prepared in advance and timed to occur shortly after target onset. Because the express saccade diagnostic pattern is not a characteristic feature of human saccadic performance, we urge investigators to focus their attention on the robust gap effect.

Attention↗

PubMed1987

Effects of alcohol on word categorization and recognition memory.

Thirty-six subjects were given no alcohol on one day and 1 ml alcohol/kg body weight on another (the order of administration being counterbalanced across subjects). In both sessions, they performed a word categorization task involving surface and semantic processing of lists of 50 words followed by a recognition task (the presentation of those words in addition to an equal number of new words for speeded recognition). For categorization, subjects were slower and less accurate with alcohol than without. For recognition, alcohol resulted in a decrease in d' and an increase in beta. Categorization was slower and recognition more accurate for semantic processing than for surface processing. There was no evidence that the detrimental effects of alcohol on recognition memory can be reduced by deeper processing of the to-be-remembered items.

Adolescent↗