Object representations for multiple visual categories overlap in lateral occipital and medial fusiform cortex

How representations of visual objects are maintained across changes in viewpoint is a central issue in visual perception. Whether neural processes underlying view-invariant recognition involve distinct subregions within extrastriate visual cortex for distinct categories of visual objects remains unresolved. We used event-related functional magnetic resonance imaging in 16 healthy volunteers to map visual cortical areas responding to a large set (156) of exemplars from 3 object categories (faces, houses, and chairs), each repeated once after a variable time lag (3-7 intervening stimuli). Exemplars were repeated with the same viewpoint (but different retinal size) or with different viewpoint and size. The task was kept constant across object categories (judging items as "young" vs. "old"). We identified object-selective adaptation effects by comparing neural responses to the first presentation versus repetition of each individual exemplar. We found that exemplar-specific adaptation effects partly overlapped with regions showing category-selective responses (as identified using a separate localizer scan). These included the lateral fusiform gyrus (FG) for faces, parahippocampal gyrus for houses, and lateral occipital complex (LOC) for chairs. In face-selective fusiform gyrus (FG), adaptation effects occurred only for faces repeated with the same viewpoint, but not with a different viewpoint, confirming previous studies using faces only. By contrast, a region in right medial FG, adjacent to but nonoverlapping with the more lateral and face-selective FG, showed repetition effects for faces and to a lesser extent for other objects, regardless of changes in viewpoint or in retinal image-size. Category- and viewpoint-independent repetition effects were also found in bilateral LOC. Our results reveal a common neural substrate in bilateral LOC and right medial FG underlying view-invariant and category-independent recognition for multiple object identities, with only a relative preference for faces in medial FG but no selectivity in LOC

Impaired activation of face processing networks revealed by functional magnetic resonance imaging in 22q11.2 deletion syndrome

BACKGROUND: 22q11.2 deletion syndrome (22q11DS) is a neurogenetic syndrome associated with a high rate of psychiatric disorders. Previous research has revealed distinctive cognitive deficits, including impaired face processing. However, the neuro-functional substrates underlying these deficits have not been explored. Our aim was to investigate facial and emotional processing in 22q11DS. METHODS: During event-related functional magnetic resonance imaging, 15 individuals with 22q11DS were compared with age- and gender-matched healthy control subjects on a simple visual categorization task (faces or houses). Each stimulus was presented twice, and faces had either neutral or emotional (fearful) expressions. RESULTS: Abnormal responses to faces were observed in 22q11DS, including a lack of normal face-selectivity in fusiform gyrus. By contrast, responses to houses were comparable across groups, with preserved selectivity in parahippocampal gyrus. Results also revealed a repetition-suppression effect for fearful faces in the right amygdala, which arose in healthy control subjects only, suggesting a lack of amygdala modulation by fear expression in 22q11DS. CONCLUSIONS: Our results demonstrate selective anomalies in several brain regions critically implicated in visual and social function in 22q11DS. These findings suggest important new avenues for studying emotional processing and social deficits frequently observed in psychotic patients and establishing their relation to specific phenotypic manifestations in 22q11DS

Reducing the use of screen electronic devices in the evening is associated with improved sleep and daytime vigilance in adolescents

The use of screen electronic devices in the evening negatively affects sleep. Yet, sleep is known to be essential for brain maturation and a key factor for good academic performance, and thus is particularly critical during childhood and adolescence. Although previous studies reported associations between screen time and sleep impairment, their causal relationship in adolescents remains unclear. Using actigraphy and daily questionnaires in a large sample of students (12 to 19 years old), we assessed screen time in the evening and sleep habits over 1 month. This included a 2 week baseline phase, followed by a 40 min sleep education workshop and a 2 week interventional phase, in which participants were asked to stop using screen devices after 9 pm during school nights. During the interventional phase, we found that the reduction of screen time after 9 pm correlated with earlier sleep onset time and increased total sleep duration. The latter led to improved daytime vigilance. These findings provide evidence that restricting screen use in the evening represents a valid and promising approach for improving sleep duration in adolescents, with potential implications for daytime functioning and health