1. HOW DO MENTAL STATE INFERENCES SHAPE THE SOCIAL WORLD IN HUNTINGTON’S DISEASE?
Clare M. Eddy1,2 & Hugh E. Rickards1,2
1 Department of Neuropsychiatry, BSMHFT The Barberry, National Centre for Mental Health - Birmingham, UK
2 School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham - Birmingham, UK
BACKGROUND AND AIMS:
Huntington’s disease (HD) can be associated with deficits in Theory of Mind (ToM): reasoning about mental states such as beliefs and emotions. Manifest patients show difficulties in reading mental states from peoples’ eyes and recognising socially inappropriate behaviour, as well as reduced perspective taking in everyday life [1-5]. ToM deficits have the potential to impact everyday functioning and affect social interaction and quality of life [6]. However, few studies have investigated ToM in pre-manifest HD. This study investigated the tendency of patients with manifest and pre-manifest HD to attribute mental states to ambiguous stimuli in the form of a series of video-clips involving animated shapes. We also explored relationships between ToM, executive functions and alexithymia: the tendency to reflect on and interpret one’s own emotional experience.
SAMPLE:
Participants were 40 patients with a positive gene test (20 males; mean age 50.1 years, SD=11.7; mean education 13.3 years, SD=2.4) and 20 healthy controls (10 males; mean age 48.0 years, SD=13.5; mean education 13.7 years, SD=2.1). Mini Mental State Examination [7] scores were at least 27/30. Fourteen patients reported depression and/or anxiety. Twenty-three were taking medication (atypical antipsychotic, SSRI or benzodiazepine). The pre-manifest subgroup (n=15) showed no equivocal motor symptoms (DCI=0/1, mean UHDRS [8] score =3.33, SD=3.81) whereas the manifest subgroup exhibited early to mid-stage motor symptoms (n=25, mean UHDRS score=33.28, SD=11.38).
TASKS:
Executive tasks assessing verbal fluency, working memory, inhibition and set-shifting
Toronto Alexithymia Scale [9]: Participants rate agreement with items such as “when I cry I always know why”, “I sometimes don’t know why I am angry” and “it is difficult for me to find the right words for my feelings”.
The ToM animations task [10] involved short video-clips featuring two triangles (Fig 1). Some clips showed random movements, while others depicted simple (e.g. dancing, chasing) or complex social interactions (e.g. mocking, persuading) prompting the inference of mental states. Participants were asked to describe what was happening. Responses were scored for accuracy and degree of intention attributed to the triangles.
FIGURE 1. SCENES FROM THE ANIMATIONS TASK
RESULTS:
Manifest HD was associated with alexithymia (p<.001) and executive deficits (p<.001).
Pre-manifest HD was associated with alexithymia (p=.009) but no executive deficits.
Both groups with HD (Fig 2 & 3) exhibited a deficit in spontaneous attribution of mental states on the animations task (p<.001).
Scores on the animations task were correlated with motor symptoms (p=.003) and alexithymia (p=.003) in manifest HD.
FIGURE 2. ACCURACY ACROSS VIDEO-CLIP TYPE
FIGURE 3. INTENTION RATINGS ACROSS VIDEO-CLIP TYPE
CONCLUSIONS:
Regardless of disease stage, HD is likely to be associated with changes in the interpretation and experience of emotions, frequently resulting in alexithymia. This could reflect a psychological reaction to diagnostic awareness or neurological changes.
Individuals with HD exhibit a reduced tendency to infer mental states, and intentions in particular, during observation of animated non-human stimuli whose movements imply social interaction. Patients explained depictions of social interactions on a more concrete basis than controls, implying a deficit in adopting the intentional stance. This could reflect poor integration of visuo-spatial information with cognitive or emotional processes required to draw ToM based inferences from action.
Subtle changes in ToM can be detected prior to motor onset. As deficits on the animations task were seen in the absence of executive dysfunction, changes in ToM per se may be present in pre-manifest HD. The ambiguity of the animations task, which offers few clues about the purpose of assessment, make this a sensitive measure to alterations in spontaneous mentalizing.
REFERENCES
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This study is taken from a project funded by a seed grant from EHDN