Oculomotor behaviours and integrative memory functions in the Alzheimer's Clinical Syndrome

Fernández, Gerardo and Parra, Mario A. (2021) Oculomotor behaviours and integrative memory functions in the Alzheimer's Clinical Syndrome. Journal of Alzheimer's Disease. ISSN 1875-8908 (In Press)

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Background. Biological information drawn from eye-tracking metrics is providing evidence regarding drivers of cognitive decline in Alzheimer disease. In particular, pupil size has proved useful to investigate cognitive performance during online activities. Objective. To investigate the oculomotor correlates of impaired performance of patients with mild Alzheimer’s Clinical Syndrome (ACS) on a recently developed memory paradigm, namely the Short-Term Memory Binding Test (STMBT). Methods. We assessed a sample of eighteen healthy controls (HC) and eighteen patients with a diagnosis of mild ACS with the STMBT while we recorded their oculomotor behaviours using pupillometry and eye-tracking. The STMBT assessed the ability to detected changes across two consecutive visual arrays, study and test, presenting 2 bicolored objects. In one condition, changes consisted of new colours in test objects replacing colours presented in the study objects (i.e., Unbound Colours - UC). In the other condition, changes consisted of two studied colours swapping between objects at test (i.e., Bound Colours - BC). We assessed recognition of such changes. Results. As expected, a group (healthy controls vs Alzheimer’s Clinical Syndrome) by condition (Unbound Colours vs Bound Colours) interaction was found whereby behavioural group differences were paramount in the Bound Colours condition. Healthy control’s pupil dilated significantly more in the Bound Colours than in the Unbound Colours condition, discrepancy not observed in Alzheimer’s Clinical Syndrome patients. Furthermore, ROC analysis revealed the abnormal pupil behaviours distinguished Alzheimer’s Clinical Syndrome patients from healthy controls with values of sensitivity and specify of 100%, thus outperforming both recognition scores and gaze duration. Conclusions. The biological correlates of Short-Term Memory Binding impairments appear to involve a network much wider than we have thought to date, which expands across cortical and subcortical structures. We discuss these findings focusing on their implications for our understanding of neurocognitive phenotypes in the preclinical stages of Alzheimer Disease and potential development of cognitive biomarkers that can support ongoing initiatives to prevent dementia.


Fernández, Gerardo and Parra, Mario A. ORCID logoORCID: https://orcid.org/0000-0002-2412-648X;