Anosognosia for theory of mind deficits: A single case study and a review of the literature

Abstract

Being aware of one's own ability to interact socially is crucial to everyday life. After a brain injury, patients may lose their capacity to understand others' intentions and beliefs, that is, the Theory of Mind (ToM). To date, the debate on the association between ToM and other cognitive deficits (in particular executive functions and behavioural disorders) remains open and data regarding awareness of ToM deficits are meagre. By means of an ad-hoc neuropsychological battery of tests, we report on a patient who suffers from ToM deficits and is not aware of these disorders, although aware of his other symptoms. The study is accompanied by a review of the literature (PRISMA guidelines) demonstrating that ToM deficits are independent of executive functions. Furthermore, an advanced lesion analysis including tractography was executed. The results indicate that: i) ToM deficits can be specific and independent of other cognitive symptoms; ii) unawareness may be specific for ToM impairment and not involve other disorders and iii) the medial structures of the limbic, monitoring and attentional systems may be involved in anosognosia for ToM impairment.

Keywords: Anosognosia; Awareness; DTI; Frontal lesion; Theory of mind.

Figure 1

a) Patient Competency Rating Scale. All scores > 5 were transformed into 1 = presence of problems, while 0 = absence of problems were divided per evaluator and component of competency. b) Dysexecutive Questionnaire. Mean and standard deviation of the dichotomised scores for the Dysexecutive Questionnaire divided by evaluator and component. All scores >0 were transformed into 1 = presence of dysexecutive behaviours, while 0 = absence of dysexecutive behaviours. c) Comparison of pre- and post-task judgements. The patient's self-evaluations before and after the execution of each of the ToM/Emotion Attribution and Cognitive tasks, divided in Correct/Incorrect responses, and Tom/Cognitive tasks. * = p<0.05.

Figure 2

The image and delineation relating to AP's lesion. a) Axial view of the CT scan showing the left hemisphere damage, the last slice (on the extreme top right) represent the dorsal limit of the lesion in the left hemisphere. b) Axial (up), sagittal (middle) and coronal (bottom) view of the left hemisphere lesion drawing (on the coronal sections, also the right lesion is appreciable) registered onto the MNI152 template. The table on the right half of the figure describes the number of voxels (N>0) and the percentage volume (%N>0) affected by the lesion for each left hemisphere grey matter structure. c) Axial view of the CT scan showing the right hemisphere damage. d) Axial (up) and sagittal (bottom) view of the right hemisphere lesion drawing registered onto the MNI 152 template. The table on the right describes the number of voxels (%N>0) and the percentage volume (N>0) affected by the lesion for each right hemisphere grey matter structure.

Figure 3

White matter disconnections in AToM. a) On the left, lateral and medial view of the left hemisphere and its damaged tracts. Cing. = cingulum; IFOF = inferior fronto occipital fasciculus; ILF = inferior longitudinal fasciculus; FOP = fronto-orbitopolar tract; FST = fronto striatal tract; SLF III = third (ventral) branch of the superior longitudinal fasciculus; FMT = fronto marginal tract; Unc = uncinate. In the centre, ventral view of the left (up) and right (bottom) hemispheres and the damaged association fibres. CC = corpus callosum. On the right, lateral and medial view of the right hemisphere and its damaged tracts. SLF I = first branch (dorsal) of the superior longitudinal fasciculus; FAT = frontal aslant tract; FSL = frontal superior longitudinal tract. b) Tract reconstruction from the patient's Diffusion Weighted Imaging. The colour bar represents the Fractional Anisotropy level. dFornix = dorsal Fornix; aFornix = anterior Fornix. c) Map of the probability of tract disconnection computed for the patient's lesion. The colour bar represents the disconnection probability ranging from 80% to 100%.