Helen Clery

fMRI investigation of visual change detection in adults with autism.

People with autism spectrum disorders (ASD) may show unusual reactions to unexpected changes that appear in their environment. Although several studies have highlighted atypical auditory change processing in ASD, little is known in this disorder about the brain processes involved in visual automatic change detection. The present fMRI study was designed to localize brain activity elicited by unexpected visual changing stimuli in adults with ASD compared to controls. Twelve patients with ASD and 17 healthy adults participated in the experiment in which subjects were presented with a visual oddball sequence while performing a concurrent target detection task. Combined results across participants highlight the involvement of both occipital (BA 18/19) and frontal (BA 6/8) regions during visual change detection. However, adults with ASD display greater activity in the bilateral occipital cortex and in the anterior cingulate cortex (ACC) associated with smaller activation in the superior and middle frontal gyri than controls. A psychophysiological interaction (PPI) analysis was performed with ACC as the seed region and revealed greater functionally connectivity to sensory regions in ASD than in controls, but less connectivity to prefrontal and orbito-frontal cortices. Thus, compared to controls, larger sensory activation associated with reduced frontal activation was seen in ASD during automatic visual change detection. Atypical psychophysiological interactions between frontal and occipital regions were also found, congruent with the idea of atypical connectivity between these regions in ASD. The atypical involvement of the ACC in visual change detection can be related to abnormalities previously observed in the auditory modality, thus supporting the hypothesis of an altered general mechanism of change detection in patients with ASD that would underlie their unusual reaction to change.

Electrophysiological correlates of automatic visual change detection in school-age children

Automatic stimulus-change detection is usually investigated in the auditory modality by studying Mismatch Negativity (MMN). Although the change-detection process occurs in all sensory modalities, little is known about visual deviance detection, particularly regarding the development of this brain function throughout childhood. The aim of the present study was to examine the maturation of the electrophysiological response to unattended deviant visual stimuli in 11-year-old children. Twelve children and 12 adults were presented with a passive visual oddball paradigm using dynamic stimuli involving changes in form and motion. Visual Mismatch responses were identified over occipito-parietal sites in both groups but they displayed several differences. In adults the response clearly culminated at around 210 ms whereas in children three successive negative deflections were evidenced between 150 and 330 ms. Moreover, the main mismatch response in children was characterized by a positive component peaking over occipito-parieto-temporal regions around 450 ms after deviant stimulus onset. The findings showed that the organization of the vMMN response is not mature in 11-year-old children and that a longer time is still necessary to process simple visual deviancy at this late stage of child development.

Electrophysiological evidence of atypical visual change detection in adults with autism

Although atypical change detection processes have been highlighted in the auditory modality in autism spectrum disorder (ASD), little is known about these processes in the visual modality. The aim of the present study was therefore to investigate visual change detection in adults with ASD, taking into account the salience of change, in order to determine whether this ability is affected in this disorder. Thirteen adults with ASD and 13 controls were presented with a passive visual three stimuli oddball paradigm. The findings revealed atypical visual change processing in ASD. Whereas controls displayed a vMMN in response to deviant and a novelty P3 in response to novel stimuli, patients with ASD displayed a novelty P3 in response to both deviant and novel stimuli. These results thus suggested atypical orientation of attention toward unattended minor changes in ASD that might contribute to the intolerance of change.

Facial Expression Related vMMN: Disentangling Emotional from Neutral Change Detection

Detection of changes in facial emotional expressions is crucial to communicate and to rapidly and automatically process possible threats in the environment. Recent studies suggest that expression-related visual mismatch negativity (vMMN) reflects automatic processing of emotional changes. In the present study we used a controlled paradigm to investigate the specificity of emotional change-detection. In order to disentangle specific responses to emotional deviants from that of neutral deviants, we presented neutral expression as standard stimulus (p = 0.80) and both angry and neutral expressions as deviants (p = 0.10, each). In addition to an oddball sequence, an equiprobable sequence was presented, to control for refractoriness and low-level differences. Our results showed that in an early time window (100–200 ms), the controlled vMMN was greater than the oddball vMMN only for the angry deviant, suggesting the importance of controlling for refractoriness and stimulus physical features in emotion related studies. Within the controlled vMMN, angry and neutral deviants both elicited early and late peaks occurring at 140 and 310 ms, respectively, but only the emotional vMMN presented sustained amplitude after each peak. By directly comparing responses to emotional and neutral deviants, our study provides evidence of specific activity reflecting the automatic detection of emotional change. This differs from broader “visual” change processing, and suggests the involvement of two partially-distinct pre-attentional systems in the detection of changes in facial expressions.

Neurocognitive, emotional and neuroendocrine correlates of exposure to sexual assault in women

BACKGROUND Survivors of sexual assault are vulnerable to long-term negative psychological and physical health outcomes, but few studies have investigated changes in cognition, emotional processing and brain function in the early stages after sexual assault. We used a multimodal approach to identify the cognitive and emotional correlates associated with sexual assault in women. METHODS Twenty-seven female survivors of sexual assault were included within 4 weeks of the traumatic event, and they were compared with 20 age-matched controls. Participants underwent functional MRI while performing cognitive/emotional tasks (n-back, emotional go/no-go, mental imagery). We also measured diurnal salivary cortisol and conducted neuropsychological assessments of attention and memory abilities. RESULTS Relative to the control group, the survivors group had lower levels of morning cortisol and showed attentional deficits. We observed no between-group differences in brain activation during the n-back or mental imagery tasks. During the emotional go/no-go task, however, the survivors group showed a lack of deactivation in the dorsal anterior cingulate cortex when processing emotional material, relative to neutral material. Exploratory analyses in the survivors group indicated that symptom severity was negatively associated with cerebellar activation when positive emotional (happy) content interfered with response inhibition, and positively associated with cerebellar activation when thinking of positive (happy) memories. LIMITATIONS The small sample size was the main limitation of this study. CONCLUSION Dysfunctions in the dorsal anterior cingulate cortex and the cerebellum may represent early functional brain modifications that alter higher cognitive processes when emotional material is involved.

Sex‐specific effects of COMT Val158Met polymorphism on corpus callosum structure: A whole‐brain diffusion‐weighted imaging study

Genetic polymorphisms play a significant role in determining brain morphology, including white matter structure and may thus influence the development of brain functions. The main objective of this study was to examine the effect of Val158Met (rs4680) polymorphism of Catechol‐O‐Methyltransferase (COMT) gene on white matter connectivity in healthy adults.

Smaller hippocampal volume following sexual assault in women is associated with post-traumatic stress disorder

Exposure to sexual assault is a significant risk factor to develop post‐traumatic stress disorder (PTSD) in females. The early neurobiological changes leading to the development of PTSD remain understudied and unclear in this population.