Thomas E. Powell

Repetition Suppression in Ventral Visual Cortex Is Diminished as a Function of Increasing Autistic Traits

Repeated viewing of a stimulus causes a change in perceptual sensitivity, known as a visual aftereffect. Similarly, in neuroimaging, repetitions of the same stimulus result in a reduction in the neural response, known as repetition suppression (RS). Previous research shows that aftereffects for faces are reduced in both children with autism and in first-degree relatives. With functional magnetic resonance imaging, we found that the magnitude of RS to faces in neurotypical participants was negatively correlated with individual differences in autistic traits. We replicated this finding in a second experiment, while additional experiments showed that autistic traits also negatively predicted RS to images of scenes and simple geometric shapes. These findings suggest that a core aspect of neural function—the brains response to repetition—is modulated by autistic traits.

Repetition suppression and memory for faces is reduced in adults with autism spectrum conditions

Abstract Autism spectrum conditions (ASC) are associated with a number of atypicalities in face processing, including difficulties in face memory. However, the neural mechanisms underlying this difficulty are unclear. In neurotypical individuals, repeated presentation of the same face is associated with a reduction in activity, known as repetition suppression (RS), in the fusiform face area (FFA). However, to date, no studies have investigated RS to faces in individuals with ASC, or the relationship between RS and face memory. Here, we measured RS to faces and geometric shapes in individuals with a clinical diagnosis of an ASC and in age and IQ matched controls. Relative to controls, the ASC group showed reduced RS to faces in bilateral FFA and reduced performance on a standardized test of face memory. By contrast, RS to shapes in object‐selective regions and object memory did not differ between groups. Individual variation in face‐memory performance was positively correlated with RS in regions of left parietal and prefrontal cortex. These findings suggest difficulties in face memory in ASC may be a consequence of differences in the way faces are stored and/or maintained across a network of regions involved in both visual perception and short‐term/working memory.

Microscopy Analysis of Breast Implant Rupture Caused by Surgical Instrument Damage

BACKGROUND The mechanism of breast implant rupture has continued to be an important topic throughout the plastic surgery community and regulatory agencies, such as the US Food and Drug Administration. Retrieved ruptured implants returned to Allergan (Santa Barbara, CA; formerly Inamed Corporation) for analysis exhibit various modes of failure, which can include a small pinhole (approximately 1 to 2 mm in size) in the shell, a ruptured shell, or a severely fragmented shell. OBJECTIVE The failure mechanisms and associated morphologic features for the modes of implant failure can be quite different. The objective of this study is to analyze and describe the rupture characteristics of silicone gel-filled implants that failed because of surgical instrument damage. METHODS There are several types of diagnostic techniques available to analyze ruptured implants. Visual inspection, physical examination, and photographic analysis provided an overall description of the implant shape and gross features of the shell failure region. These techniques allowed categorization and documentation of the mode of failure and were quite useful as a supplemental tool in the diagnosis of implant failure mechanisms. Microscopy techniques provided details of the ruptured shell region and could be used to determine the cause of breast implant failure. This study involved the use of optical microscopy and scanning electron microscopy in the analysis of ruptured breast implants. RESULTS Details of the geometry of ruptured shell regions are described. Illustrations are also presented in which 35-mm photography is used to assist in substantiating the cause of failure. Many of the ruptured regions exhibit striations across the thickness of the shell. Micrographs are presented that clearly show that the striations are due to lines in the cutting surface of the surgical instrument that were formed during the manufacturing process. CONCLUSIONS This article demonstrates that, with the proper background and experience in analyzing ruptured breast implant shells, the features at the failure site can be correctly interpreted and the corresponding failure mechanisms can be diagnosed. Breast implants are subject to surgical instrument damage during implantation, and this damage can develop into a shell rupture, with the failure mode identifiable via microscopy analysis.

The effect of perceptual expectation on repetition suppression to faces is not modulated by variation in autistic traits

There is substantial variation in the magnitude of the repetition suppression (RS) effects across individuals; however the causes of this variation remain unclear. In a recent study, we found that RS in occipitotemporal cortex was negatively related to individual variation in autistic traits in a neurotypical population. Recent proposals have considered autistic behaviours within a Bayesian framework, suggesting that individuals with autism may have ‘attenuated priors’ (i.e., their perception is less influenced by prior information). Predictive coding represents a neural instantiation of Bayesian inference, and characterises RS as reduction in prediction error between ‘top-down’ (prior beliefs) and ‘bottom-up’ (stimulus related) inputs. In accordance with this, evidence shows that RS is greater when repetition of a stimulus is expected relative to when it is unexpected. Here, using an established paradigm which manipulates the probability of stimulus repetition, we investigated the effect of perceptual expectation on RS in a group of neurotypical individuals varying on a measure of autistic traits. We predicted that the magnitude of the perceptual expectation effect would be negatively related to individual differences in autistic traits. We found a significant effect of perceptual expectation on RS in face-selective regions (i.e., greater RS when repetitions were expected relative to unexpected). However, there was no evidence of a relationship between autistic traits and the magnitude of this effect in any face-selective region of interest (ROI). These findings provide a challenge for the proposal that autism spectrum conditions (ASC) may be associated with the attenuated influence of prior information.

Algorithms in the newsroom? News readers’ perceived credibility and selection of automated journalism:

Automated journalism, the autonomous production of journalistic content through computer algorithms, is increasingly prominent in newsrooms. This enables the production of numerous articles, both r...

Reduced repetition suppression to faces in the fusiform face area of adults with autism spectrum conditions.

In neuroimaging studies, repetitions of the same stimulus typically result in a reduction in neural activity, known as repetition suppression (RS). Repeated presentation of the same face is associated with RS in core regions of the face processing network, including the fusiform face area (FFA). At a behavioural level, repeated viewing of the same stimulus causes a change in perceptual sensitivity, known as a visual aftereffect. Evidence indicates that visual aftereffects for faces are attenuated in children and adolescents with autism spectrum conditions (ASC), leading to the proposal that atypical adaptive coding in face processing networks may underlie difficulties in face learning and memory found in ASC. However, whether individuals with ASC show reduced RS to faces remains to be addressed. Here, we used functional MRI to investigate RS to faces and non-faces (simple geometric shapes) in adults with a clinical diagnosis of ASC. We measured activity in face- and object-selective regions of occipitotemporal cortex while participants viewed blocks of images comprising repetitions of the same face/shape or images of different faces/shapes. Participants also completed standardized behavioural tests of face and car memory. Relative to age and IQ matched controls, individuals with ASC showed diminished RS to faces in right FFA. By contrast, RS to shapes in object-selective regions did not differ between groups. This finding could not be explained by differences in gaze fixations or face-selectivity in FFA. In addition, behavioural data revealed that individuals with ASC showed a significant impairment in face memory (compared to controls) but not car memory. These findings suggest reduced RS in FFA as a possible neural mechanism underlying attenuated facial aftereffects found in ASC, and suggest that differences in the adaptive properties of the face-processing network may underlie difficulties in face learning and memory associated with this condition. Meeting abstract presented at VSS 2015.

Framing fast and slow: a dual processing account of multimodal framing effects

ABSTRACT Human reasoning can be characterized by a continuum anchored by two extremes: fast, automatic, and emotional processing on the one side; versus slow, controlled and rational processing on the other. Despite theoretical linkages, no studies have empirically connected these types of information processing with the mechanisms of multimodal (visual and textual) media effects. We employ tools from dual processing theories in a framing effects paradigm to test whether the effects of news visuals and text take place via relatively more automatic and controlled information processing, respectively. To do so, we combine experimental manipulations and individual differences data collected across two experiments using different political issues. Results from experimental manipulations provide converging evidence for the distinct processing of visuals and text. Individual differences data paint a more nuanced picture, suggesting that the processing of multimodal news frames does not always conform to a simple automatic-controlled dichotomy.