Abstract
The present study aims at clarifying the nature of the Theory of Mind (ToM) deficits associated with Amyotrophic Lateral Sclerosis (ALS). ToM is the ability to attribute mental states such as intentions and beliefs to others in order to understand and predict their behaviour and to behave accordingly. Several neuroimaging studies reported the prefrontal cortices as the brain region underlying a key ToM ability, i.e. the comprehension of social intentions. Dysfunction of the prefrontal cortices in patients with ALS has been indicated by a range of neuroimaging studies. The frontal syndrome that appears to characterize up to 50% of ALS has been noted to be similar to the profile that characterizes patients with frontotemporal dementia (FTD), a neurodegenerative condition characterised by ToM deficits. In the present paper, we hypothesize that the performance of patients with ALS is significantly worse than healthy controls' performance on tasks requiring the comprehension of social contexts, whereas patients' performance is comparable to healthy controls' performance on tasks not requiring the comprehension of social contexts. To this end, we tested 15 patients with ALS with an experimental protocol that distinguishes between private (non-social) intentions and social intentions. The pattern of results followed the experimental hypothesis: the performance of patients with ALS and healthy controls significantly differed on the comprehension of social context only, with an impairment in patients with ALS. Single case analysis confirmed the findings at an individual level. The present study is the first which has examined and compared the understanding of social and non-social contexts in patients with ALS and shown a specific and selective deficit in the former only. The current findings further support the notion of a continuum of cognitive dysfunction ranging from ALS to FTD, with parallel cognitive profiles in both disorders.
Highlights
Amyotrophic Lateral Sclerosis (ALS) involves the progressive degeneration of upper and lower motor neurones
The qualitative analysis of the results showed that the errors made by the patients with ALS were similar to the ones made by patients with frontotemporal dementia (FTD) [28] due to the demanding nature of the tasks used, it is possible that executive dysfunction may have been at the root of the reported deficit
The present study was aimed at investigating a specific Theory of Mind (ToM) ability, i.e. the ability of correctly interpreting social situations by attributing intentions to others appropriately, and demonstrated that ALS patients showed a specific deficit in understanding social intentions
Summary
Amyotrophic Lateral Sclerosis (ALS) involves the progressive degeneration of upper and lower motor neurones. ALS has traditionally been considered as a neurodegenerative condition affecting exclusively the motor system, with no repercussions on the cognitive domain. Structural and functional neuroimaging has demonstrated that ALS is associated with abnormalities localized mainly in the frontal lobes [6,7,8,9,10], and neuropathological investigations have shown the pathological involvement of prefrontal cortices [11]. The frontal syndrome that appears to characterize up to 50% of ALS has been noted to be similar to the profile that characterizes patients with frontotemporal dementia (FTD). A link has been established between ALS and FTD on neuropathological [14,15,16], neuroimaging [10,17] and cognitive [18] grounds. It has been proposed that ALS may represent a point on a clinical continuum ranging from ALS, ALS/FTD through to FTD [10,19]
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