Performance on the Iowa Gambling Task (IGT) in clinical populations can be interpreted only in relation to established baseline performance in normal populations. As in all comparisons of assessment tools, the normal baseline must reflect performance under conditions in which subjects can function at their best levels. In this review, we show that a number of variables enhance IGT performance in non-clinical participants. First, optimal performance is produced by having participants turn over real cards while viewing virtual cards on a computer screen. The use of only virtual cards results in significantly lower performance than the combination of real + virtual cards. Secondly, administration of more than 100 trials also enhances performance. When using the real/virtual card procedure, performance is shown to significantly increase from early adolescence through young adulthood. Under these conditions young (mean age 19 years) and older (mean age 59 years) adults perform equally. Females, as a group, score lower than males because females tend to choose cards from high-frequency-of-gain Deck B. Groups of females with high or low gonadal hormones perform equally. Concurrent tasks, e.g., presentation of aromas, decrease performance in males. Age and gender effects are discussed in terms of a dynamic between testosterone and orbital prefrontal cortex.

No abstract

Inhibition of return (IOR) is typically described as an inhibitory bias against returning attention to a recently attended location as a means of promoting efficient visual search. Most studies examining IOR, however, either do not use visual search paradigms or do not effectively isolate attentional processes, making it difficult to conclusively link IOR to a bias in attention. Here, we recorded ERPs during a simple visual search task designed to isolate the attentional component of IOR to examine whether an inhibitory bias of attention is observed and, if so, how it influences visual search behavior. Across successive visual search displays, we found evidence of both a broad, hemisphere-wide inhibitory bias of attention along with a focal, target location-specific facilitation. When the target appeared in the same visual hemifield in successive searches, responses were slower and the N2pc component was reduced, reflecting a bias of attention away from the previously attended side of space. When the target occurred at the same location in successive searches, responses were facilitated and the P1 component was enhanced, likely reflecting spatial priming of the target. These two effects are combined in the response times, leading to a reduction in the IOR effect for repeated target locations. Using ERPs, however, these two opposing effects can be isolated in time, demonstrating that the inhibitory biasing of attention still occurs even when response-time slowing is ameliorated by spatial priming.

No abstract

Accurate integration of auditory and visual information is essential for our ability to communicate with others. Previous studies have shown that the temporal discrepancies over which audiovisual speech stimuli will be integrated into a coherent percept are much wider than those typically observed for simple stimuli like beeps and flashes of light. However, our sensitivity to the low-level features of simple stimuli is not constant. We hypothesized that part of the enhanced integration of audiovisual speech may be due to it consisting predominantly of the sound frequencies and visual spatial frequencies that humans are most sensitive to. Here, we examined integration behaviors for pure tones across the sound frequency spectrum and visual gratings across the spatial frequency spectrum to examine how these low-level features modulate integration. The temporal window of integration was modulated by both sound frequency and visual spatial frequency, with the widest integration window occurring when both stimuli fell within their respective peak sensitivity ranges. These results suggest that part of the increased tolerance for temporal asynchrony typically observed for audiovisual speech may be due to the differential integration of low-level stimulus features that are dominant within complex audiovisual speech.