Mapping levels of theory of mind in Alzheimer's disease: a preliminary study.

BACKGROUND: Research on Theory of Mind (ToM), the ability to understand behaviour based on mental state representation, has shifted towards a life span perspective in typical and atypical conditions (dementia). OBJECTIVES: The aim of this study is to investigate the presence and the features of ToM decay in early Alzheimer's disease (AD) patients compared to healthy controls adopting a neurodevelopmental stance. METHOD: Sixteen AD patients and 16 healthy controls were submitted to an increasing complexity ToM battery, tapping ToM precursors, standard first- and second-order false beliefs and advanced ToM tasks (Eyes Test and strange stories). RESULTS: The results underline a similar pattern of increasing difficulty of the tasks that explore ToM abilities in both the groups. They also confirm the presence of a strong gap in performance between the CTR and the AD groups, especially in the more complex ToM tasks, whereas there is no significant difference between the two groups in the first level of reasoning about beliefs (first-order false belief). The impairment in specific cognitive functions (i.e. memory and executive functions) seems to correlate with the decline in the most complex mentalistic abilities. CONCLUSION: This study identifies a specific pattern of deterioration in ToM abilities in AD patients, following backwards developmental steps typical of the acquisition of mentalizing abilities, where the most complex ToM levels are impaired, whereas the intermediate and the simplest ones are preserved.

Effects of aging on mindreading ability through the eyes: an fMRI study.

Theory of Mind--ToM, the capacity to understand one's own and other people's mental states and to refer to them to foresee and explain the behaviour--relies upon a circumscribed neural system: the posterior end of the superior temporal sulcus (pSTS), the adjacent temporo-parietal junction (TPJ), the temporal pole (TP), the medial prefrontal cortex (mPFC) and the adjacent paracingulate cortex. To our knowledge, the neural basis of mentalizing has not yet been studied in a developmental perspective covering old age, so the aim of this work is to compare the neural basis of a specific aspect of ToM, the mindreading ability through the eyes, in healthy young and old subjects. Two groups of healthy adults (young: 25.2 years; old: 65.2 years) were submitted to an fMRI scanning while performing the Reading the Mind in the Eyes test, which requires the attribution of a mental state to the other person focussing only on the eye-gaze. There was no difference in the behavioural performances between young and old and both groups of subjects activated the pSTS and the TP, thus indicating that old people show no impairment of mentalizing circuits. However, a relevant shifting of the neural circuit implied in each group to solve the task emerged. Old subjects showed a more bilateral activation of frontal areas and a stronger involvement of the linguistic components of the mirror neuron system (i.e. area 44), as compared to young. Both young and old participants activated the non-linguistic components of the mirror neuron system, such as area 6. These findings are discussed taking into account the recent literature dealing with cognitive functions during normal aging.