Neural correlates of memory deficits in premanifest -repeat expansions.

Background: The premanifest stage in carriers of hexanucleotide repeat expansions in the gene (C9RE) is associated with memory impairment. The present study examines whether the impairment is general across domains or disproportionately affects specific stimulus categories such as socioemotional events, and its underlying functional neuroanatomy.

Methods: This task-based fMRI-study included 21 premanifest C9RE (preC9RE) carriers and 24 controls. Participants encoded stimuli of (emotional and neutral) faces and houses, followed by a recognition task. Using univariate and multivoxel pattern analyses at whole-brain level and region-of-interest level, we investigated the neural change during encoding and retrieval processes, as well as the neural pattern similarity between encoding and retrieval.

Results: Compared with controls, the preC9RE group demonstrated poorer performance in memorising faces (U=104, p=0.002), while their ability to memorise houses remained intact. The preC9RE group exhibited distinct neural patterns in the anterior insula during face encoding compared with the controls (accuracy>0.765, p<0.05). During face retrieval, the preC9RE group showed an increased neural response to encoded faces versus new faces in the right anterior insula (U=394, p=0.015). Individuals with preC9RE exhibited reduced encoding-retrieval neural similarity in the salience network specifically related to face stimuli (U=120, p=0.023).

Conclusions: The findings reveal functional changes in the salience network related to impaired social memory at the premanifest stage of C9RE. The findings further underscore the high potential of multidimensional neural response patterns as a sensitive biomarker for neurodegenerative functional changes, and the salience network as biomarker for C9RE disease staging.