Felicity D. A. Wolohan

Cultural diversity and saccade similarities: culture does not explain saccade latency differences between Chinese and Caucasian participants.

A central claim of cultural neuroscience is that the culture to which an individual belongs plays a key role in shaping basic cognitive processes and behaviours, including eye movement behaviour. We previously reported a robust difference in saccade behaviour between Chinese and Caucasian participants; Chinese participants are much more likely to execute low latency express saccades, in circumstances in which these are normally discouraged. To assess the extent to which this is the product of culture we compared a group of 70 Chinese overseas students (whose primary cultural exposure was that of mainland China), a group of 45 participants whose parents were Chinese but who themselves were brought up in the UK (whose primary cultural exposure was western European) and a group of 70 Caucasian participants. Results from the Schwartz Value Survey confirmed that the UK-Chinese group were culturally similar to the Caucasian group. However, their patterns of saccade latency were identical to the mainland Chinese group, and different to the Caucasian group. We conclude that at least for the relatively simple reflexive saccade behaviour we have investigated, culture cannot explain the observed differences in behaviour.

Temporal Stability and the Effects of Training on Saccade Latency in "Express Saccade Makers"

The temporal stability of saccade latency, and the effects of training, particularly in “express saccade makers” (ESMs), has received little attention. ESMs are healthy, naïve, adults, who persist in executing very many low latency “express saccades” (ES; saccades with latency of 80 ms to 130 ms), in conditions designed to suppress such responses. We investigated the stability of ES production (%ES) in 59 ESM and 54 non-ESM participants in overlap tasks. Within a single session, the intraclass correlation coefficient (ICC) for %ES in two runs of 200 trials was 0.97 (p<0.001); participants in whom >30% of saccades over the two runs were ES, were classified as ESMs. For 60 participants tested over two sessions 12 weeks apart, and 30 participants tested in three sessions over approximately six months, the ICC for %ES was uniformly high (0.95, p<0.001 and 0.97, p<0.001 respectively) and participants behaved consistently with their initial classification. Fourteen participants (7 ESMs) were then exposed to training consisting of either gap or overlap tasks. Training increased %ES in both groups. However, when tested in overlap tasks, it was not sufficient to transform Normal participants into ESMs. We conclude that the pattern of saccade behaviour exhibited by ESMs constitutes a stable and distinct oculomotor phenotype.

Top-down contributions to attention shifting and disengagement: a template model of visual attention

Two separate systems are involved in the control of spatial attention; one that is driven by a goal, and the other that is driven by stimuli. While the goal- and stimulus-driven systems follow different general principles, they also interplay with each other. However, the mechanism by which the goal-driven system influences the stimulus-driven system is still debated. The present study examined top-down contributions to two components of attention orienting, shifting and disengagement, with an experimental paradigm in which participants held a visual item in short-term memory (STM) and performed a prosaccade task with a manipulation of the gap between fixation offset and target onset. Four experiments showed that the STM content accelerated shifting and impaired disengagement, but the influence on disengagement depended on the utility of STM in guiding attention toward the target. Thus, the use of STM was strategic. Computational models of visual attention were fitted to the experimental data, which suggested that the top-down contributions to shifting was more prominent than those to disengagement. The results indicate that the current modeling framework was particularly useful when examining the contributions of theoretical constructs for the control of visual attention, but it also suggests limitations.

The capture of visual attention using auditory cues in schizophrenia

Background: One cognitive feature of schizophrenia (SZ) is a deficit in the ability to disengage attention from salient events in peripheral vision (Maruff et al., 1998). We investigated whether an analogous attention deficit might occur in SZ in the auditory sensory modality; i.e., whether individuals with SZ may experience a difficulty shifting attention away from the location of a sound. Methods: We used a technique similar to Posners (1980) spatial cueing paradigm, but with peripheral auditory cues and visual targets. The target could be presented either same side or contralateral to the spatial location from which the cue had sounded 200 ms prior, and participants executed a saccadic eye movement to the target. Three conditions varied the probability of the target appearing on the same side as the cue (20%, 50%, and 80% target-at-cue conditions). Saccadic latencies were subjected to an ANOVA with 2 repeated measures factors (Congruency and Condition), and with Group (SZ vs. Controls) as a between-groups measure. Results: The ANOVA revealed a sig. Congruency effect (i.e., latency advantage for visual targets same side vs. opposite side to the auditory cue), F = 108.9, p < .001, and a sig. Congruency x Condition interaction, F = 18.31, p < .001; post hoc contrasts revealed a greater Congruency effect in the 80% target-at-cue condition. The only significant interaction involving Group was Group x Congruency, F = 9.94, p < .005, indicating a larger Congruency effect for SZ. Discussion: In both healthy individuals and patients with SZ, visual attention is reflexively drawn to the spatial location of an auditory stimulus, even if the target visual event is unlikely to occur at that location. The magnitude of this effect is larger in SZ, however, suggesting that, on congruent trials the visual attention of individuals with SZ is more readily captured by an auditory stimulus, and they may also be slower to disengage attention from an auditory signal.