Study of Repetitive Behaviors in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by anterograde amnesia, the inability to memorize and remember events occurring after the cerebral lesion. Among the most frequently reported psycho-behavioural symptoms are repetitive behaviours (RB), defined as actions or statements repeated in an inappropriate and non-functional way.

The most commonly used tool to assess repetitive behaviours is the Stereotypy Rating Inventory (SRI). It is a questionnaire that evaluates five types of stereotypical behaviour: eating, wandering, speech, movements, and daily routines. The frequency and severity of the behaviours are reported, and a total score can be calculated.

There is no consensus on the types of repetitive behaviours observed specifically in AD, their frequency, or their cognitive correlates, nor is there a hypothesis explaining why this symptomatology does not occur in all AD patients. Furthermore, certain parameters, such as anosognosia (lack of awareness of the disorders), have not been linked to RB in the literature. We propose to evaluate patients with anterograde amnesia in terms of cognition and behaviour-specifically, the presence or absence of both RB and anosognosia-to examine possible links between cognitive performance, anosognosia, and RB.

Moreover, there is no theoretical framework explaining the emergence of RB in amnesia. We suggest that CRs are linked to the lack of memory updating in the cognitive system. Since episodic memory no longer provides mnemonic feedback, previously encountered stimuli may trigger repeated behaviour.

To test this hypothesis, we decided to conduct a multicenter, cross-sectional, case-control study. Patients with AD, with or without RB, as well as healthy subjects, were repeatedly presented with sentence starters to complete freely, with the aim of studying the similarity of responses across sessions for each participant. We also included a patient with pure anterograde amnesia from a previously submitted case study protocol, who exhibited pronounced RB symptomatology following neurosurgery (non-AD patient), to examine the phenomenon in a non-Alzheimer's context.