Overt Visual Attention as a Causal Factor of Perceptual Awareness

Our everyday conscious experience of the visual world is fundamentally shaped by the interaction of overt visual attention and object awareness. Although the principal impact of both components is undisputed, it is still unclear how they interact. Here we recorded eye-movements preceding and following conscious object recognition, collected during the free inspection of ambiguous and corresponding unambiguous stimuli. Using this paradigm, we demonstrate that fixations recorded prior to object awareness predict the later recognized object identity, and that subjects accumulate more evidence that is consistent with their later percept than for the alternative. The timing of reached awareness was verified by a reaction-time based correction method and also based on changes in pupil dilation. Control experiments, in which we manipulated the initial locus of visual attention, confirm a causal influence of overt attention on the subsequent result of object perception. The current study thus demonstrates that distinct patterns of overt attentional selection precede object awareness and thereby directly builds on recent electrophysiological findings suggesting two distinct neuronal mechanisms underlying the two phenomena. Our results emphasize the crucial importance of overt visual attention in the formation of our conscious experience of the visual world

Precisely timed oculomotor and parietal EEG activity in perceptual switching

Blinks and saccades cause transient interruptions of visual input. To investigate how such effects influence our perceptual state, we analyzed the time courses of blink and saccade rates in relation to perceptual switching in the Necker cube. Both time courses of blink and saccade rates showed peaks at different moments along the switching process. A peak in blinking rate appeared 1,000 ms prior to the switching responses. Blinks occurring around this peak were associated with subsequent switching to the preferred interpretation of the Necker cube. Saccade rates showed a peak 150 ms prior to the switching response. The direction of saccades around this peak was predictive of the perceived orientation of the Necker cube afterwards. Peak blinks were followed and peak saccades were preceded by transient parietal theta band activity indicating the changing of the perceptual interpretation. Precisely-timed blinks, therefore, can initiate perceptual switching, and precisely-timed saccades can facilitate an ongoing change of interpretation

Electrical Brain Stimulation During a Retrieval-Based Learning Task Can Impair Long-Term Memory

Anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) has been shown to improve performance on a multitude of cognitive tasks. These are, however, often simple tasks, testing only one cognitive domain at a time. Therefore, the efficacy of brain stimulation for complex tasks has yet to be understood. Using a task designed to increase learning efficiency, this study investigates whether anodal tDCS over the left DLPFC can modulate both learning ability and subsequent long-term memory retention. Using a within-subject design, participants (N = 25) took part in 6 training sessions over consecutive days in which active or sham stimulation was administered randomly (3 of each). A computer-based task was used, containing flags from countries unknown to the participants. Each training session consisted of the repetition of 8 pairs of flag/country names. Subsequently, in three testing sessions, free, cued, and timed cued recall, participants were assessed on all 48 flags they had learnt. No difference in learning speed between active and sham tDCS was found. Furthermore, in the timed cued recall phase, flags learnt in the sham tDCS sessions were recalled significantly better than flags learnt in the active tDCS sessions. This effect was stronger in the second testing session. It was also found that for the flags answered incorrectly; thus, meaning they were presented more frequently, subsequent long-term retention was improved. These results suggest that for a complex task, anodal tDCS is ineffective at improving learning speed and potentially detrimental to long-term retention when employed during encoding. This serves to highlight the complex nature of brain stimulation, providing a greater understanding of its limitations and drawbacks

Supporting Patients Treated for Prostate Cancer: A Video Vignette Study With an Email-Based Educational Program in General Practice

Background: Men who have been treated for prostate cancer in Australia can consult their general practitioner (GP) for advice about symptoms or side effects at any time following treatment. However, there is no evidence that such men are consistently advised by GPs and patients experience substantial unmet need for reassurance and advice. Objective: The intent of the study was to evaluate a brief, email-based educational program for GPs to manage standardized patients presenting with symptoms or side effects months or years after prostate cancer treatment. Methods: GPs viewed six pairs of video vignettes of actor-patients depicting men who had been treated for prostate cancer. The actor-patients presented problems that were attributable to the treatment of cancer. In Phase 1, GPs indicated their diagnosis and stated if they would prescribe, refer, or order tests based on that diagnosis. These responses were compared to the management decisions for those vignettes as recommended by a team of experts in prostate cancer. After Phase 1, all the GPs were invited to participate in an email-based education program (Spaced Education) focused on prostate cancer. Participants received feedback and could compare their progress and their performance with other participants in the study. In Phase 2, all GPs, regardless of whether they had completed the program, were invited to view another set of six video vignettes with men presenting similar problems to Phase 1. They again offered a diagnosis and stated if they would prescribe, refer, or order tests based on that diagnosis.Results: In total, 64 general practitioners participated in the project, 57 GPs participated in Phase 1, and 45 in Phase 2. The Phase 1 education program was completed by 38 of the 57 (59%) participants. There were no significant differences in demographics between those who completed the program and those who did not. Factors determining whether management of cases was consistent with expert opinion were number of sessions worked per week (OR 0.78, 95% CI 0.67-0.90), site of clinical practice (remote practice, OR 2.25, 95% CI 1.01-5.03), number of patients seen per week (150 patients or more per week, OR 10.66, 95% CI 3.40-33.48), and type of case viewed. Completion of the Spaced Education did impact whether patient management was consistent with expert opinion (not completed, OR 0.88, 95% CI 0.5-1.56).Conclusions: The management of standardized patients by GPs was particularly unlikely to be consistent with expert opinion in the management of impotence and bony metastasis. There was no evidence from this standardized patient study that Spaced Education had an impact on the management of patients in this context. However, the program was not completed by all participants. Practitioners with a greater clinical load were more likely to manage cases as per expert opinion