Kate Humphreys

Seeing it differently: Visual processing in autism.

Several recent behavioral and neuroimaging studies have documented an impairment in face processing in individuals with Autism Spectrum Disorder (ASD). It remains unknown, however, what underlying mechanism gives rise to this face processing difficulty. One theory suggests that the difficulty derives from a pervasive problem in social interaction and/or motivation. An alternative view proposes that the face-processing problem is not entirely social in nature and that a visual perceptual impairment might also contribute. The focus of this review is on this latter, perceptual perspective, documenting the psychological and neural alterations that might account for the face processing impairment. The available evidence suggests that perceptual alterations are present in ASD, independent of social function.

Configural processing in autism and its relationship to face processing

Studies of the perceptual performance of individuals with autism have focused, to a large extent, on two domains of visual behavior, one associated with face processing and the other associated with global or holistic processing. Whether autistic individuals differ from neurotypical individuals in these domains is debatable and, moreover, the relationship between the behaviors in these two domains remains unclear. We first compared the face processing ability of 14 adult individuals with autism with that of neurotypical controls and showed that the autistic individuals were slowed in their speed of face discrimination. We then showed that the two groups differed in their ability to derive the global whole in two different tasks, one using hierarchical compound letters and the other using a microgenetic primed matching task with geometric shapes, with the autistic group showing a bias in favor of local information. A significant correlation was also observed between performance on the face task and the configural tasks. We then confirmed the prediction that the ability to derive the global whole is not only critical for faces but also for other objects as well, as the autistic individuals performed more slowly than the control group in discriminating between objects. Taken together, the results suggest that the bias for local processing seen in autistic individuals might have an adverse impact on their ability to process faces and objects.

Reduced structural connectivity in ventral visual cortex in congenital prosopagnosia

Using diffusion tensor imaging and tractography, we found that a disruption in structural connectivity in ventral occipito-temporal cortex may be the neurobiological basis for the lifelong impairment in face recognition that is experienced by individuals who suffer from congenital prosopagnosia. Our findings suggest that white-matter fibers in ventral occipito-temporal cortex support the integrated function of a distributed cortical network that subserves normal face processing.

Normal Movement Selectivity in Autism

It has been proposed that individuals with autism have difficulties understanding the goals and intentions of others because of a fundamental dysfunction in the mirror neuron system. Here, however, we show that individuals with autism exhibited not only normal fMRI responses in mirror system areas during observation and execution of hand movements but also exhibited typical movement-selective adaptation (repetition suppression) when observing or executing the same movement repeatedly. Movement selectivity is a defining characteristic of neurons involved in movement perception, including mirror neurons, and, as such, these findings argue against a mirror system dysfunction in autism.

A detailed investigation of facial expression processing in congenital prosopagnosia as compared to acquired prosopagnosia.

Whether the ability to recognize facial expression can be preserved in the absence of the recognition of facial identity remains controversial. The current study reports the results of a detailed investigation of facial expression recognition in three congenital prosopagnosic (CP) participants, in comparison with two patients with acquired prosopagnosia (AP) and a large group of 30 neurologically normal participants, including individually age- and gender-matched controls. Participants completed a fine-grained expression recognition paradigm requiring a six-alternative forced-choice response to continua of morphs of six different basic facial expressions (e.g. happiness and surprise). Accuracy, sensitivity and reaction times were measured. The performance of all three CP individuals was indistinguishable from that of controls, even for the most subtle expressions. In contrast, both individuals with AP displayed pronounced difficulties with the majority of expressions. The results from the CP participants attest to the dissociability of the processing of facial identity and of facial expression. Whether this remarkably good expression recognition is achieved through normal, or compensatory, mechanisms remains to be determined. Either way, this normal level of performance does not extend to include facial identity.

The anatomy of the callosal and visual-association pathways in high-functioning autism: A DTI tractography study

There is increasing recognition that many of the core behavioral impairments that characterize autism potentially emerge from poor neural synchronization across nodes comprising dispersed cortical networks. A likely candidate for the source of this atypical functional connectivity in autism is an alteration in the structural integrity of intra- and inter-hemispheric white matter (WM) tracts that form large-scale cortical networks. To test this hypothesis, in a group of adults with high-functioning autism (HFA) and matched control participants, we used diffusion tensor tractography to compare the structural integrity of three intra-hemispheric visual-association WM tracts, the inferior longitudinal fasciculus (ILF), the inferior fronto-occipito fasciculus (IFOF) and the uncinate fasciculus (UF), with the integrity of three sub-portions of the major inter-hemispheric fiber tract, the corpus callosum. Compared with the control group, the HFA group evinced an increase in the volume of the intra-hemispheric fibers, particularly in the left hemisphere, and a reduction in the volume of the forceps minor (F-Mi) and body of the corpus callosum. The reduction in the volume of the F-Mi also correlated with an increase in repetitive and stereotypical behavior as measured by the Autism Diagnostic Interview. These findings suggest that the abnormalities in the integrity of key inter- and intra-hemispheric WM tracts may underlie the atypical information processing observed in these individuals.

Cortical patterns of category-selective activation for faces, places and objects in adults with autism.

Autism is associated with widespread atypicalities in perception, cognition and social behavior. A crucial question concerns how these atypicalities are reflected in the underlying brain activation. One way to examine possible perturbations of cortical organization in autism is to analyze the activation of category‐selective ventral visual cortex, already clearly delineated in typical populations. We mapped out the neural correlates of face, place and common object processing, using functional magnetic resonance imaging (fMRI), in a group of high‐functioning adults with autism and a typical comparison group, under both controlled and more naturalistic, viewing conditions. There were no consistent group differences in place‐related regions. Although there were no significant differences in the extent of the object‐related regions, there was more variability for these regions in the autism group. The most marked group differences were in face‐selective cortex, with individuals with autism evincing reduced activation, not only in fusiform face area but also in superior temporal sulcus and occipital face area. Ventral visual cortex appears to be organized differently in high‐functioning adults with autism, at least for face‐selective regions, although subtle differences may also exist for other categories. We propose that cascading developmental effects of low‐level differences in neuronal connectivity result in a much more pronounced effect on later developing cortical systems, such as that for face‐processing, than earlier maturing systems (those for objects and places).

mHealth and memory aids: levels of smartphone ownership in patients

Abstract Background: The use of mobile devices to deliver healthcare has not yet been exploited in neuropsychological rehabilitation. Smartphones have the potential to serve as multi-functional memory aids. Aims: To investigate whether patients attending a clinic for mixed memory problems own smartphones, to determine whether this could be a widely applicable medium to use as a memory aids device. Methods: A questionnaire on smartphone ownership was given to an opportunity sample of consecutive patients attending a neuropsychiatry and memory disorders outpatient clinic. Data were collected in 2012 and repeated 12 months later in 2013 to assess changes over time. Results: Ownership of mobile phones was stable between 2012 (81%) and 2013 (85%), but ownership of smartphones showed a significant increase (from 26% to 40%). Age negatively predicted smartphone ownership. Conclusion: Despite cognitive or psychiatric problems, our patient group are as likely to own a mobile phone as a member of the general population. Ownership levels are at 40% and likely to increase in the future. Exploring how smartphones and their apps could function as memory aids is likely to be useful for a large enough number of patients to be clinically worthwhile.

The development of face-space in infancy

Valentine (1991) proposed that faces are encoded in a multidimensional “face-space”. Here, we apply this framework to the development of face processing in infancy. It is thought that faces are encoded as “regions” in the face-space, such that variations in the face input are recognized as the same face identity. In a set of studies with 4-month-olds, 7-month-olds, and adults, we addressed the question of how these “identity regions” develop. The findings indicated that they are initially broad and become narrowed with development. Our results suggest that the face-space model can usefully be applied to face processing in infancy.

Psychogenic amnesia: syndromes, outcome, and patterns of retrograde amnesia

&NA; There are very few case series of patients with acute psychogenic memory loss (also known as dissociative/functional amnesia), and still fewer studies of outcome, or comparisons with neurological memory‐disordered patients. Consequently, the literature on psychogenic amnesia is somewhat fragmented and offers little prognostic value for individual patients. In the present study, we reviewed the case records and neuropsychological findings in 53 psychogenic amnesia cases (ratio of 3:1, males:females), in comparison with 21 consecutively recruited neurological memory‐disordered patients and 14 healthy control subjects. In particular, we examined the pattern of retrograde amnesia on an assessment of autobiographical memory (the Autobiographical Memory Interview). We found that our patients with psychogenic memory loss fell into four distinct groups, which we categorized as: (i) fugue state; (ii) fugue‐to‐focal retrograde amnesia; (iii) psychogenic focal retrograde amnesia following a minor neurological episode; and (iv) patients with gaps in their memories. While neurological cases were characterized by relevant neurological symptoms, a history of a past head injury was actually more common in our psychogenic cases (P = 0.012), perhaps reflecting a ‘learning episode’ predisposing to later psychological amnesia. As anticipated, loss of the sense of personal identity was confined to the psychogenic group. However, clinical depression, family/relationship problems, financial/employment problems, and failure to recognize the family were also statistically more common in that group. The pattern of autobiographical memory loss differed between the psychogenic groups: fugue cases showed a severe and uniform loss of memories for both facts and events across all time periods, whereas the two focal retrograde amnesia groups showed a ‘reversed’ temporal gradient with relative sparing of recent memories. After 3–6 months, the fugue patients had improved to normal scores for facts and near‐normal scores for events. By contrast, the two focal retrograde amnesia groups showed less improvement and continued to show a reversed temporal gradient. In conclusion, the outcome in psychogenic amnesia, particularly those characterized by fugue, is better than generally supposed. Findings are interpreted in terms of Markowitschs and Kopelmans models of psychogenic amnesia, and with respect to Andersons neuroimaging findings in memory inhibition.