Midbrain dysfunction in anorexia nervosa

A biomarker and endophenotype for anorexia nervosa?

OBJECTIVE

Recent research has suggested that a type of atypical eye movement, called square wave jerks, together with anxiety, may distinguish individuals with anorexia nervosa from those without anorexia nervosa and may represent a biomarker and endophenotype for the illness. The aim of this study was to identify the presence of this proposed marker in individuals currently with anorexia nervosa relative to healthy controls, and to identify the state independence and heritability of this putative marker by exploring whether it also exists in individuals who are weight-restored from anorexia nervosa and first-degree relatives (i.e. sisters of people with anorexia nervosa).

METHODS

Data from 80 female participants (20/group: current anorexia nervosa, weight-restored from anorexia nervosa, sisters of people with anorexia nervosa and healthy controls) were analysed. Square wave jerk rate was acquired during a fixation task, and anxiety was measured with the State Trait Anxiety Inventory.

RESULTS

Current anorexia nervosa, weight-restored from anorexia nervosa and sisters of people with anorexia nervosa groups made significantly more square wave jerks than healthy controls, but did not differ from one another. Square wave jerk rate and anxiety were found to discriminate groups with exceptionally high accuracy (current anorexia nervosa vs healthy control = 92.5%; weight-restored from anorexia nervosa vs healthy control = 77.5%; sisters of people with anorexia nervosa vs healthy control = 77.5%; p < .001).

CONCLUSION

The combination of square wave jerk rate and anxiety was found to be a promising two-element marker for anorexia nervosa, and has the potential to be used as a biomarker or endophenotype to identify people at risk of anorexia nervosa and inform future treatments.

Eye movements in anorexia nervosa: State or trait markers?

OBJECTIVE

Differences in saccadic eye movements are widely reported in mental illnesses, and can indirectly inform our understanding of neurobiological and cognitive underpinnings of psychiatric conditions, including anorexia nervosa (AN). Preliminary research has suggested that individuals with AN may show specific eye movement abnormalities; whether these deficits are representative of state or trait effects is, however, unclear. The aim of this study was to identify whether there are demonstrable differences in performance on saccadic eye movement tasks in individuals with current AN (c-AN), those who are weight-restored from AN (wr-AN), biological sisters of individuals with AN (AN-sis), and healthy controls (HC).

METHODS

Eighty participants took part in the study (n = 20/group). A set of saccadic eye movement tasks was administered, including prosaccade, antisaccade, memory-guided saccade, and visual scanpath tasks.

RESULTS

The c-AN group showed an increased rate of inhibitory errors to 10° targets on the memory-guided saccade task.

DISCUSSION

The results are discussed in terms of the potential role of the superior colliculus in AN, and that the findings may reflect a state measure of AN.

High-definition transcranial direct current stimulation in anorexia nervosa: A pilot study

OBJECTIVE

Anorexia nervosa (AN) is a serious psychiatric condition often associated with poor outcomes. Biologically informed treatments for AN, such as brain stimulation, are lacking, in part due to the unclear nature of the neurobiological contributions to the illness. However, recent research has suggested a specific neurobiological target for the treatment of AN, namely stimulation of the inferior parietal lobe (IPL). The aim of this study was to stimulate-noninvasively-the left IPL in individuals with AN using high-definition transcranial direct current stimulation (HD-tDCS).

METHOD

Twenty participants will be randomized to receive 10 daily sessions of HD-tDCS or sham HD-tDCS (placebo). Assessments will be carried out at baseline and end point, as well as 4- and 12-week follow-ups.

DISCUSSION

This pilot investigation will primarily determine the feasibility and acceptability of this intervention.

An Overlooked Brain Region in the Aetiology of Anorexia Nervosa: The Importance of Behaviourally Driven Neuroimaging Analysis

The neurobiological contributions to anorexia nervosa (AN) remain poorly understood, hindering the development of effective neurobiological treatments such as medications and brain stimulation. A large number of studies have been undertaken utilising neuroimaging techniques, such as magnetic resonance imaging (MRI), to gain a better understanding of the brain mechanisms involved in the illness. However, the analyses undertaken by many studies have utilised a whole-brain analytical approach as much of this research has been exploratory in nature. This is, however, problematic as small brain regions that differ between groups may not have the statistical power to produce statistically significant results. This is highlighted in a recent study undertaken by our group utilising diffusion-weighted imaging. In this research, we identified widespread white matter microstructural differences in individuals with AN, but only showed differences in a small brain region (the superior colliculus) when a region-of-interest approach that was driven by behavioural findings was utilised. The importance of hypothesis-driven neuroimaging analyses is discussed in this article.