A choice reaction time index of callosal anatomical homotopy

Tachistoscopically presented bilateral stimulus pairs not parallel to the meridian produced significantly longer RTs on a task requiring discrimination of shapes (Go/no-Go) than pairs emplaced symmetrically on each side of the meridian in Desjardins and Braun [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121,  125–136]. This was explained by the fact that there are more homotopic than heterotopic fibers in the corpus callosum. However: (1) different parts of the visual field were not equiprobably stimulated, possibly causing subtle biases, (2) the predicted cost of vertical asymmetry was tested only with bilateral stimuli, and (3) interstimulus distance was at the outer limit of callosal midline fusion (10.6°). Here, a tachistoscopic experiment with 24 normal participants replicated the between-field vertical symmetry advantage [Desjardins, S., & Braun, C. M. J. (2006). Homotopy and heterotopy and the bilateral field advantage in the Dimond paradigm. Acta Psychologica, 121, 125–136.], but without irrelevant stimulation conditions and with more proximal stimuli. In addition, a significant specific cost of vertical asymmetry of 7 ms was found for between-field integration over within-field integration. As far as we know, this is the first demonstration of an effect of callosal anatomical homotopy with reaction time.     

“You and your best friend Suzy put Slime in Ms. Smollett’s desk”: Producing false memories with self-relevant details

Rates of false memory reports vary markedly in the published literature. In an effort to explain these differences, the present study investigated the effects of including different types of details in a false narrative upon subsequent false memory formation. Participants were assigned to one of four conditions in which the inclusion of self-relevant and/or specific details in a false event (putting a toy in a teacher's desk) was manipulated. Participants engaged in a standard memory recovery procedure over three interviews, involving recall for three true and one false event Upon completion, 68.2% of participants in self-relevant groups were judged as having created memories or images about the false event, as compared with 36.4% in non-self-relevant groups. Subjective ratings of memory intensity were higher for self-relevant groups, and self-relevant participants were less likely to correctly guess the false event. These findings indicate that including self-relevant details in suggested childhood events increases the likelihood that such events will be accepted as false memories.     

How to launch a national Internet-based panel study quickly: lessons from studying how American are coping with the tragedy of September 11, 2001?

This article reports on the planning, development, and implementation of a large national Internet-based panel study of how Americans are coping with the terrorist attacks of September 11, 2001. The study was designed to determine predictors and correlates of risk and resilience, both cross-sectionally and longitudinally. In order to acquire timely and meaningful data, we developed/adapted an extensive set of measures, obtained human subjects approval, and posted a research Web site just 17 days after the attacks. This article describes the major hurdles we confronted and the guidelines we recommend regarding these topics, including the methodological trade-offs inherent in Internet-based research, information technology requirements and tribulations, human subjects issues, selection of measures and securing permission for their use, and the challenges of participant recruitment. We also discuss issues that we did not anticipate, including the survey intervention. We focus not on findings, but on the concrete procedural, administrative, technical, and scientific challenges we encountered and the solutions we devised under considerable time and resource pressures.     

Effects of stress and motivation on performing a spatial task

Learning is ubiquitous in the animal kingdom but has been studied extensively in only a handful of species. Moreover, learning studied under laboratory conditions is typically unrelated to the animal's natural environment or life history. Here, we designed a task relevant to the natural behavior of male African cichlid fish (Astatotilapia burtoni), to determine if they could be trained on a spatial task to gain access to females and shelter. We measured both how successfully animals completed this task over time and whether and how immediate early gene and hormone expression profiles were related to success. While training fish in a maze, we measured time to task completion, circulating levels of three key hormones (cortisol, 11-ketotestosterone, and testosterone) and mRNA abundance of seven target genes including three immediate early genes (that served proxies for brain activity) in nine brain regions. Data from our subjects fell naturally into three phenotypes: fish that could be trained (learners), fish that could not be trained (non-learners) and fish that never attempted the task (non-attempters). Learners and non-learners had lower levels of circulating cortisol compared to fish that never attempted the task. Learners had the highest immediate early gene mRNA levels in the homologue of the hippocampus (dorsolateral telencephalon; Dl), lower cortisol (stress) levels and were more motivated to accomplish the task as measured by behavioral observations. Fish that never attempted the task showed the lowest activity within the Dl, high stress levels and little to no apparent motivation. Data from non-learners fell between these two extremes in behavior, stress, and motivation.