J.W. Van Strien

Distinct brain systems underlie the processing of valence and arousal of affective pictures.

Valence and arousal are thought to be the primary dimensions of human emotion. However, the degree to which valence and arousal interact in determining brain responses to emotional pictures is still elusive. This functional MRI study aimed to delineate neural systems responding to valence and arousal, and their interaction. We measured neural activation in healthy females (N=23) to affective pictures using a 2 (Valence) x 2 (Arousal) design. Results show that arousal was preferentially processed by middle temporal gyrus, hippocampus and ventrolateral prefrontal cortex. Regions responding to negative valence included visual and lateral prefrontal regions, positive valence activated middle temporal and orbitofrontal areas. Importantly, distinct arousal-by-valence interactions were present in anterior insula (negative pictures), and in occipital cortex, parahippocampal gyrus and posterior cingulate (positive pictures). These data demonstrate that the brain not only differentiates between valence and arousal but also responds to specific combinations of these two, thereby highlighting the sophisticated nature of emotion processing in (female) human subjects.

Corpus callosum size correlates with asymmetric performance on a dichotic listening task in healthy aging but not in Alzheimer's disease

Alzheimers disease (AD) involves not only gray matter but also white matter pathology, as reflected by atrophy of the corpus callosum (CC). Since decreased CC size may indicate reduced functional interhemispheric connectivity, differences in callosal size may have cognitive consequences that may become specifically apparent in neuropsychological tasks that tap hemispheric laterality. In the present study, we examined callosal functioning with a dichotic listening task in 25 Alzheimer patients, 20 healthy elderly and 20 healthy elderly with subjective memory complaints. We found decreased performance, increased ear asymmetry, and decreased callosal size in the AD group compared to healthy elderly. As expected, in the healthy elderly, we found significant negative correlations between ear asymmetry and callosal size, specifically in the anterior and posterior callosal subareas. While the association with the posterior subareas (isthmus and splenium) points at involvement of temporal areas mediating language processing, the association with the anterior subarea (the rostrum and genu) points at involvement of frontal areas mediating attention and executive functions. Remarkably however, in contrast to the healthy elderly, callosal size was not related to ear asymmetry in the AD group. The absence of an association between callosal atrophy and ear asymmetry implies that other pathological processes, next to reduced callosal functioning, attribute to ear asymmetry in AD. Difficulties to attend specifically to the left ear during dichotic listening in some of the AD patients, points at decreased attention and executive functions and suggests that pathology of specifically the frontal areas is involved.

Increased prevalences of left-handedness and left-eye sighting dominance in individuals with Williams-Beuren syndrome.

Handedness and eye sighting dominance were assessed in a sample of 50 individuals (25 male, 25 female; aged 5–38 years) with Williams-Beuren syndrome (WBS). The prevalences of left-handedness and left-eyedness were compared to the normative prevalences in the general population. We found significantly higher prevalences of left-handedness and left-eyedness in the WBS sample. The higher prevalences were more salient in younger than in older individuals and in male than in female individuals. We suggest that the increased prevalence of left-handedness in WBS is a consequence of a slower maturation rate, which allows deviation from a predetermined laterality pattern. The authors are grateful to the patients with Williams-Beuren Syndrome and their families for participating in this study. M.A. Frens was supported by NWO-VIDI. J.N. van der Geest was supported by grants from NWO (903-68-394) and the Revolving Fund of the Erasmus MC.

Snake pictures draw more early attention than spider pictures in non- phobic women: Evidence from event-related brain potentials

Snakes were probably the first predators of mammals and may have been important agents of evolutionary changes in the primate visual system allowing rapid visual detection of fearful stimuli (Isbell, 2006). By means of early and late attention-related brain potentials, we examined the hypothesis that more early visual attention is automatically allocated to snakes than to spiders. To measure the early posterior negativity (EPN), 24 healthy, non-phobic women watched the random rapid serial presentation of 600 snake pictures, 600 spider pictures, and 600 bird pictures (three pictures per second). To measure the late positive potential (LPP), they also watched similar pictures (30 pictures per stimulus category) in a non-speeded presentation. The EPN amplitude was largest for snake pictures, intermediate for spider pictures and smallest for bird pictures. The LPP was significantly larger for both snake and spider pictures when compared to bird pictures. Interestingly, spider fear (as measured by a questionnaire) was associated with EPN amplitude for spider pictures, whereas snake fear was not associated with EPN amplitude for snake pictures. The results suggest that ancestral priorities modulate the early capture of visual attention and that early attention to snakes is more innate and independent of reported fear.

Parametric event-related fMRI of word encoding and retrieval

Introduction In block designs, the parametric variation of one parameter of a task has proven to be a strong tool to study cognitive processes. Event-related fMIU designs have more recently also improved our understanding of different cognitive processes (see for example (l-3)). In this study we combined an event-related and a parametric design to study verbal learning as function of word repetition. The goal of this experiment is to study the stimulus-response curve of brain activation upon word repetition.