Interhemispheric EEG coherence during sleep and wakefulness in left- and right-handed subjects

REM sleep is associated with the production of complex imagery sequences. Yet research is divided as to whether different brain regions are more or less coordinated in their functioning at this time. Some research suggests that there may occur a functional disconnection of the left and right cerebral hemispheres during REM sleep which is similar to the disconnection syndrome seen after corpus callosotomy. Other research suggests that an increase in interhemispheric coordination occurs. On the assumption that hemispheric coordination is reflected in the EEG coherence measure, we explored differences in interhemispheric coherence recorded in six left- and six right-handed normal subjects during periods of wakefulness, stage REM, stage 2, and stage 3/4 sleep. Strong evidence was found that mean EEG coherence values are larger during sleep than during waking and that they are approximately equal for the different stages of sleep. Frontal electrode placements demonstrated a slightly different pattern of coherence than central, parietal, or occipital placements. Furthermore, coherence values were larger for left-handed subjects over the occipital region during wakefulness, stage 2, and stage REM sleep, but not during stage 3/4 sleep. Coherence was not different for male and female subjects. These findings oppose the interpretation that a functional disconnection of hemispheres occurs during REM sleep and favor the interpretation that sleep in general is a state of heightened cortical coordination. Moreover, greater interhemispheric coherence over occipital brain regions in left-handed subjects suggests possible differences in the cognitive processes of these subjects during waking and dreaming states.     

Sex differences in cerebral laterality of language and visuospatial processing

Sex differences on language and visuospatial tasks are of great interest, with differences in hemispheric laterality hypothesized to exist between males and females. Some functional imaging studies examining sex differences have shown that males are more left lateralized on language tasks and females are more right lateralized on visuospatial tasks; however, findings are inconsistent. Here we used functional magnetic resonance imaging to study thirty participants, matched on task performance, during phonological and visuospatial tasks. For each task, region-of-interest analyses were used to test differences in cerebral laterality. Results indicate that lateralization differences exist, with males more left lateralized during the phonological task and showing greater bilateral activity during the visuospatial task, whereas females showed greater bilateral activity during the phonological task and were more right lateralized during the visuospatial task. Our data provide clear evidence for differences in laterality between males and females when processing language versus visuospatial information.     

Selective inhibition in children with attention-deficit hyperactivity disorder off and on stimulant medication

Selective inhibition requires discrimination between auditory signals and is assessed using a modification of the stop-signal task. Selective inhibition was assessed in a group of 59 clinic-referred, DSM-IV-diagnosed children with attention-deficit hyperactivity disorder (ADHD) and compared to that of a community sample of 59 children. Methylphenidate (MPH) effects on selective inhibition were assessed in a subset of the ADHD sample that participated in an acute, randomized, placebo-controlled, crossover trial with 3 fixed doses of MPH. Children with ADHD performed more poorly than controls on the majority of selective stop-signal task parameters: they exhibited more anticipatory (invalid) responses, with less accurate and more variable responses on the response execution task, as well as a slower selective inhibition process. MPH improved speed of both inhibition and response execution processes; it also reduced variability of response execution and decreased nonselective inhibition. On the one hand, findings are consistent with purported inhibition deficit in ADHD, but on the other hand, suggest that neither the impairment itself, nor MPH effects, were restricted to inhibition.     

A Comparison of Within- and Across-Activity Choices for Reducing Challenging Behavior in Children with Autism Spectrum Disorders

Offering children with autism spectrum disorders (ASD) choices between activities (e.g., working on math or English), instructional materials (e.g., using a pen or pencil), or environmental arrangements (e.g., where to sit) has been shown to reduce challenging behavior maintained by escape from task demands. However, the majority of research investigating choice-based interventions for challenging behavior has examined across-activity choices (i.e., choosing between activities) and relatively few studies have examined within-activity choice (i.e., choosing between instructional materials or environmental arrangements). The purpose of this study is to replicate and extend previous research on choice-based challenging behavior interventions by comparing the effects of across-activity choices and within-activity choices on the escape-maintained challenging behavior of 4 children with ASD. An alternating treatment design was embedded within the “B” phase of an ABAB design in which the “A” phase represented a no-choice baseline condition. Both choice formats resulted in less challenging behavior than the baseline condition for all participants. Across-activity choice resulted in less challenging behavior than within-activity choice for 3 participants. Implications for research and practice are discussed.     

Cross-modal attentional entrainment: Insights from magicians

Recently, performance magic has become a source of insight into the processes underlying awareness. Magicians have highlighted a set of variables that can create moments of visual attentional suppression, which they call “off-beats.” One of these variables is akin to the phenomenon psychologists know as attentional entrainment. The current experiments, inspired by performance magic, explore the extent to which entrainment can occur across sensory modalities. Across two experiments using a difficult dot probe detection task, we find that the mere presence of an auditory rhythm can bias when visual attention is deployed, speeding responses to stimuli appearing in phase with the rhythm. However, the extent of this cross-modal influence is moderated by factors such as the speed of the entrainers and whether their frequency is increasing or decreasing. In Experiment 1, entrainment occurred for rhythms presented at .67 Hz, but not at 1.5 Hz. In Experiment 2, entrainment only occurred for rhythms that were slowing from 1.5 Hz to .67 Hz, not speeding. The results of these experiments challenge current models of temporal attention.     

Global Zimbabweans: Diaspora Engagement and Disengagement

Since 2000, migration from crisis-ridden Zimbabwe has led to almost one million people leaving the country. The majority migrate to neighbouring South Africa and Botswana, and most of the research on the Zimbabwean diaspora to date has focused on South Africa and the UK. However, the Zimbabwean diaspora is now truly global in its distribution. This paper argues that more attention should therefore be paid to Zimbabweans in other jurisdictions in the Global South and North. Zimbabweans began migrating to Canada in increasing numbers after 2000, most as refugees but also as immigrants and students. Based on a survey of the Zimbabwean diaspora in Canada, this paper focuses on their migration history, demographic characteristics and backward linkages with Zimbabwe. Given the interest in diaspora engagement in the global migration and development literature, it is important to understand the nature of these linkages in order to assess the potential for diaspora involvement in Zimbabwean development. The paper argues that under current economic and political conditions in Zimbabwe, this potential remains weak.     

Rorschach Comprehensive System data for a sample of 309 adult nonpatients from Portugal

Three hundred and nine nonpatient adults, evenly distributed according to sex, age, educational level, and residence, took part in the Rorschach test study carried out in Portugal. The sample was drawn from selected regions of the country and was balanced for population density in urban and rural areas. Test administration was controlled through the services of psychologists familiar with the Rorschach Comprehensive System (CS; Exner, 1993). Results indicate that, in Portugal (Pires, 2000), level of education is the variable that seems to have the largest effect on Rorschach responding.