Repetition Suppression and Memory for Faces is Reduced in Adults with Autism Spectrum Conditions.

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.

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 brain's response to repetition--is modulated by autistic traits.

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.

Morphology of breast implant fold flaw failure.

The percent of modern silicone gel breast implants that fail due to shell rupture is quite low, amounting to less than 1% per year. Nonetheless, extensive retrieval and analysis studies are being conducted on failed devices returned to Allergan Medical (formerly Inamed Corporation) in order to determine the modes and causes of failure. With the modes and causes known, solutions can be implemented to eliminate the failure mechanisms. Analyses conducted thus far have demonstrated that there are several causes of breast implant failure. The focus of this paper is on one type of silicone gel breast implant failure, i.e., a failure associated with a fold or wrinkle, which is termed "fold flaw failure." Although fold flaw failure is not a dominant mode of failure for silicone gel breast implants, its failure characteristics must be understood in order for this type of shell rupture to be detected and eventually eliminated. In this study, optical microscopy and scanning electron microscopy are used to describe the morphology of fold flaw failure for explanted silicone gel breast implants with smooth shells. The microscopy analysis demonstrates that there are several different types of shell failure patterns that can be produced by a fold or wrinkle in a silicone gel breast implant.

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.