OCULOMOTOR RESPONSES PROVIDE EVIDENCE OF NEURODEGENERATIVE MECHANISMS UNDERPINNING MEMORY BINDING IMPAIRMENTS IN ALZHEIMER?S DISEASE

FERNANDEZ GERARDO; PARRA MARIO; OROZCO DAVID; AGAMENNONI OSVALDO

ALZHEIMERS & DEMENTIA

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2018 vol. 14 p. 399 - 400

1552-5260

Pupil behaviours informabout cognitive load and performanceduring online activities (Laeng et al., 2012). Contrary to otherocular responses such as Gazing, which heavily relies on cortical networks,pupil behaviour is thought to rely on neurotransmitter systemslocated in the brainstem(Alnaes et al., 2014).We have recently shownthat Gazing can inform about underpinnings of memory binding deficitsin patients with Alzheimer?s disease (Fernandez et al., 2018). Asa cortical response, Gazing is more prompted to cognitive biaswhereas pupil behaviour, might provide an unbiased biological measureof cognitive performance during a task known to be a marker forAD (the short-term memory binding task ? STMBT). This studyinvestigated if the combined analysis of pupil behaviour during theSTMBT test could enhance the sensitivity to detect AD. Methods:Data were collected from 13 controls and 13 age and educationmatched patients with AD. Patients were diagnosed based onDSM-IV criteria.We used EyeLink 1000 eyetracker to collect oculomotordata during STMB performance. The STMBT assesses theability to recognise changes in two consecutive arrays of bicoloredobjects which had to be remember as wholes (bound colours - BC)or as parts (unbound colours - UC). We compared behavioural andocular data across Groups, Task Conditions, and Memory Stages. Results:Mean pupil behaviour significantly increased in controls fromUC to BC condition a change not observed in AD patients(t¼1.97). Controls? and AD patients? pupil behaviour did not differduring the UC condition (t¼0.63) but it did during the BC condition(t¼-5.19). ROC analyses revealed that pupil behaviour during performance on the BC condition achieved 100% sensitivity andspecificity (See Figure 1). Conclusions:Binding colours into bicoloredobjects is known to be a cognitive demanding task. Such demands aretaxed by pupil behaviour only in controls, thus indicating that themechanisms responsible for extracting such a cost are impaired byAD neurodegeneration and that was true for 100% of our patients.A few AD makers have achieved such a classification power.We suggestthat combining VSTMB performance and pupil behaviour wouldoffer biomarker evidence of AD pathology.