The influence of aging on poststroke depression using a rat model via middle cerebral artery occlusion

Poststroke depression (PSD) is the most frequent psychological sequela following stroke. While previous studies describe the impact of age on brain infarct volume, brain edema, and blood–brain barrier (BBB) breakdown following ischemia, the role of age on PSD has yet to be described. Here, we examine the influence of age on PSD progression in a rat model of PSD by middle cerebral artery occlusion (MCAO). One hundred forty-three rats were divided into three groups. 48 rats 20 weeks of age underwent a sham procedure, 51 rats 20 weeks of age had MCAO, and 44 rats 22–26 months of age had MCAO. Groups were further divided into two subgroups. The first subgroup was used to measure infarct lesion volume, brain edema, and BBB breakdown at 24 h. In the second subgroup at 3 weeks after MCAO, rats were subjected to a sucrose preference test, two-way shuttle avoidance task, forced swimming test, and a brain-derived neurotrophic factor (BDNF) protein level measurement. Total and striatal infarct volume, brain edema, and BBB breakdown in the striatum were increased in older rats, as compared with younger rats. While both old and young rats exhibited depressive-like behaviors on each of the behavioral tests and lower BDNF levels post-MCAO, as compared with control rats, there were no differences between old and young rats. Although older rats suffered from larger infarct volumes, increased brain edema and more BBB disruption following MCAO, the lack of behavioral differences between young and old rats suggests that there was no effect of rat age on the incidence of PSD.     

Sudden Unexpected Versus Violent Death and PTSD Symptom Development

Changes to posttraumatic stress disorder (PTSD) trauma criterion in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM–5) have been an area of much scrutiny and debate. One of the proposed changes included removing sudden unexpected death (SUD) from the list of potentially traumatic events. This study tested the extent to which unexpected death differed from violent death and other traumas as measured by PTSD symptoms. Our results indicated a significant difference in symptom development between those experiencing sudden violent death and sudden unexpected, but nonviolent, death. Additional analyses at the DSM–IV symptom cluster level, as well as with Simms, Watson, and Doebbeling’s (2002) factor structure of PTSD symptoms, suggested further distinctions between event types and symptom development. The extent to which SUD should be included in the trauma criterion is considered.     

Learned prediction affects body perception

Learning to recognize objects appears to depend critically on extended observation of appearance over time. Specifically, temporal association between dissimilar views of an object has been proposed as a tool for learning invariant representations for recognition. We examined heretofore untested aspects of the temporal association hypothesis using a familiar dynamic object, the human body. Specifically, we examined the role of appearance prediction (temporal asymmetry) in temporal association. In our task, observers performed a change detection task using upright and inverted images of a walking body either with or without previous exposure to a motion stimulus depicting an upright walker. Observers who were exposed to the dynamic stimulus were further divided into two groups dependent on whether the observed motion depicted forward or backward walking. We find that the effect of the motion stimulus on sensitivity is highly dependent on whether the observed motion is consistent with past experience.     

“Filling-in” colour in natural scenes

Our subjective experience of the world as being in full colour across the entire visual field is at odds with the highly fovea-biased distribution of cones in the retina. It is unclear how this percept of “pan-field colour” comes about. We use novel stimuli—“colour chimeras”—to demonstrate a related visual phenomenon in which observers perceive rich colour throughout images with large achromatic regions. This percept appears to critically depend on natural scene statistics. By separately manipulating chromatic and structural content in such images, we demonstrate that both the spatial distribution of colour and the presence of recognizable scene structure contribute to the experience of pan-field colour in these stimuli. Our results suggest that this percept is unlikely to be due to a low-level colour spreading process. Instead, we suggest that mechanisms dependent on natural scenes’ chromatic and luminance statistics provide the basis for the phenomenon.     

Exploring the atheist personality: well-being,awe, and magical thinking in atheists,Buddhists, and Christians

Atheists are America’s least trusted group, and stereotypes about them abound: Atheists are non-conformist, sceptical, cynical, and joyless, rarely experiencing awe. Atheists (N?=?42) were recruited from the American atheist website and compared to Christians (N?=?22) and Buddhists (N?=?18). Groups were highly similar in their reported well-being, empathy, and other personality scales, but differed strongly on scales assessing Spirituality and Magical Ideation, where atheists rejected the concepts of spirituality and magical beliefs. Responding to the question, “Have you ever felt wonderment or felt as if you were part of something greater than yourself?,” 71% said “yes,” citing Nature (54%), Science, (30%), Music/Art (12%), and Human cooperation (8%). Respondents explained their lack of belief as deriving from a preference for logic and rationality, suggesting an intellectual component to atheism. Findings thus support the stereotype of atheists as logical, sceptical, and non-conformist, but not as cynical and joyless.