Roles for Drosophila mushroom body neurons in olfactory learning and memory

Olfactory learning assays in Drosophila have revealed that distinct brain structures known as mushroom bodies (MBs) are critical for the associative learning and memory of olfactory stimuli. However, the precise roles of the different neurons comprising the MBs are still under debate. The confusion surrounding the roles of the different neurons may be due, in part, to the use of different odors as conditioned stimuli in previous studies. We investigated the requirements for the different MB neurons, specifically the alpha/beta versus the gamma neurons, and whether olfactory learning is supported by different subsets of MB neurons irrespective of the odors used as conditioned stimuli. We expressed the rutabaga (rut)-encoded adenylyl cyclase in either the gamma or alpha/beta neurons and examined the effects on restoring olfactory associative learning and memory of rut mutant flies. We also expressed a temperature-sensitive shibire (shi) transgene in these neuron sets and examined the effects of disrupting synaptic vesicle recycling on Drosophila olfactory learning. Our results indicate that although we did not detect odor-pair-specific learning using GAL4 drivers that primarily express in gamma neurons, expression of the transgenes in a subset of alpha/beta neurons resulted in both odor-pair-specific rescue of the rut defect as well as odor-pair-specific disruption of learning using shi(ts1).     

Risk factors for nonsuicidal self‐injury in Japanese college students: The moderating role of mood regulation expectancies

Self‐injurious behavior is increasing among college students, and is common in both psychiatric and nonclinical populations. People's engaging in self‐injury is associated with childhood maltreatment, poor negative mood regulation expectancies, and depression. During times of distress, maltreated children without healthy coping strategies tend to have impairment in mood regulation, which contributes to engaging in self‐injury. This study investigated differences between nonsuicidal self‐injury (NSSI) and non‐self‐injury groups in history of childhood maltreatment, negative mood regulation expectancies, and depression in a sample of Japanese college students. We also assessed risk factors for self‐injurious behavior, including mood regulation expectancies as a moderator of the relationship between childhood maltreatment and NSSI. Participants were 313 undergraduate students, who completed anonymous self‐report questionnaires—Deliberate Self‐Harm Inventory, Child Abuse and Trauma Scale, Negative Mood Regulation Scale, and short version of the Center for Epidemiological Studies–Depression Scale. Ten percent (n = 31) of all participants had injured themselves. Consistent with past literature, participants with self‐injury history reported more severe childhood maltreatment, poorer mood regulation expectancies, and more depression, compared to non‐self‐injurers. Frequency of NSSI positively correlated with childhood maltreatment and depression, and negatively correlated with negative mood regulation expectancies. Regression analysis revealed that stronger expectancies for negative mood regulation interacted with maltreatment to predict self‐injury: More maltreatment was associated with more self‐injury, particularly among those with weaker expectancies. Results suggested childhood maltreatment, low expectancies for negative mood regulation, and depression predicted self‐injury. Consistent with our moderation hypothesis, strong expectancies for negative mood regulation buffered the effects of childhood maltreatment, reducing the risk for self‐injury.     

Inconsistent locomotion inhibits vection

We measured the strength of illusory self-motion perception (vection) with and without locomotion on a treadmill. The results revealed that vection was inhibited by inconsistent locomotion, but facilitated by consistent locomotion.     

Halt and recovery of illusory motion perception from peripherally viewed static images

We quantitatively investigated the halt and recovery of illusory motion perception in static images. With steady fixation, participants viewed images causing four different motion illusions. The results showed that the time courses of the Fraser-Wilcox illusion and the modified Fraser-Wilcox illusion (i.e., "Rotating Snakes") were very similar, while the Ouchi and Enigma illusions showed quite a different trend. When participants viewed images causing the Fraser-Wilcox illusion and the modified Fraser-Wilcox illusion, they typically experienced disappearance of the illusory motion within several seconds. After a variable interstimulus interval (ISI), the images were presented again in the same retinal position. The magnitude of the illusory motion from the second image presentation increased as the ISI became longer. This suggests that the same adaptation process either directly causes or attenuates both the Fraser-Wilcox illusion and the modified Fraser-Wilcox illusion.     

Illusory three-dimensional rotation of horizontal lines: a new motion-depth illusion.

A new motion--depth illusion is reported. When a curved aperture translates vertically and stationary horizontal lines can be seen through it, the line lengths on the retina change continuously because of the occlusion. Instead of seeing the aperture translate, subjects sometimes see the lines rotate in depth around a vertical axis. This is a rare kind of illusion: an ambiguous motion which can be seen as either stationary in two dimensions or rotating in three dimensions. Three-dimensional rotation was more often observed when the luminance difference between the horizontal lines and the background was larger than that between the aperture and the background. This illusion demonstrates that motion detection and the structure-from-motion process correlate with figure--ground segregation, depth stratification, and figural-completion processes based on luminance contrast.     

Effects of angularity of the figures with sharp and round corners on visual evoked potentials

Following a study in which equilateral triangles elicited larger visual evoked potentials (VEPs) than either squares or circles, we examined the effect of single-line angular figures with a sharp or a round corner at angles of 45°, 90°, 135° or 180°. VEPs were recorded monopolarly at four locations on the midline of scalp for 10 subjects, while the figure was tachiscopically presented to the lower visual field. Subtracted waves were obtained between figure and control (blank) conditions. N1 (peak latency 135–142 ms) and P2 (235–237 ms) waves were identifiable. N1 amplitude tended to decrease as a function of angularity, irrespective of orientation (angle pointing up or down). The effect of the sharpness/roundness of the corner was much smaller than that of its angularity. These findings suggest that the greater VEP response with triangles than with squares and circles may be attributable to the acute angularity of triangles. Related cortical processes and VEP components are also discussed.