Pupillary responses and memory-guided visual search reveal age-related and Alzheimer's-related memory decline.
Episodic memory - composed of memory for unique spatiotemporal experiences - is known to decline with aging, and even more severely in Alzheimer 's disease (AD). Memory for trial-unique objects in spatial scenes depends on the integrity of the hippocampus and interconnected structures that are among the first areas affected in AD. We reasoned that memory for objects-in-scenes would be impaired with aging, and that further impairments would be observed in AD. We asked younger adults, healthy older adults, older adults at-risk for developing cognitive impairments, and older adults with probable early AD to find changing items ('targets') within images of natural scenes, measuring repeated-trial changes in search efficiency and pupil diameter. Compared to younger adults, older adults took longer to detect target objects in repeated scenes, they required more fixations and those fixations were more dispersed. Whereas individuals with AD showed some benefit of memory in this task, they had substantially longer detection times, and more numerous, dispersed fixations on repeated scenes compared to age-matched older adults. Correspondingly, pupillary responses to novel and repeated scenes were diminished with aging and further in AD, and the memory-related changes were weaker with aging and absent in AD. Our results suggest that several nonverbal measures from memory-guided visual search tasks can index aging and Alzheimer's disease status, including pupillary dynamics. The task measurements are sensitive to the integrity of brain structures that are associated with Alzheimer's-related neurodegeneration, the task is well tolerated across a range of abilities, and thus, it may prove useful in early diagnostics and longitudinal tracking of memory decline.
Department of Biology, Centre for Vision Research, York University, Toronto, ON, Canada. Electronic address: mishelle.dr@gmail.com.
Michelle C
MC
Dragan
Department of Psychology, Centre for Vision Research, York University, Toronto, ON, Canada. Electronic address: tsk@yorku.ca.
Timothy K
TK
Leonard
Toronto Western Hospital, University of Toronto, Toronto, ON, Canada. Electronic address: lozano@uhnresearch.ca.
Andres M
AM
Lozano
Toronto Western Hospital, University of Toronto, Toronto, ON, Canada. Electronic address: Mary.McAndrews@uhn.ca.
Mary Pat
MP
McAndrews
Toronto Western Hospital, University of Toronto, Toronto, ON, Canada. Electronic address: karenwy.ng@uhnresearch.ca.
Karen
K
Ng
Rotman Research Institute, Baycrest, University of Toronto, Toronto, ON, Canada. Electronic address: jryan@research.baycrest.org.
Jennifer D
JD
Ryan
Toronto Western Hospital, University of Toronto, Toronto, ON, Canada. Electronic address: David.Tang-Wai@uhn.ca.
David F
DF
Tang-Wai
Rotman Research Institute, Baycrest, University of Toronto, Toronto, ON, Canada. Electronic address: jwynn@research.baycrest.org.
Jordana S
JS
Wynn
Department of Psychology, Department of Biology, Centre for Vision Research, Toronto, ON, M3J 1P3, Canada. Electronic address: khoffman@yorku.ca.
Kari L
KL
Hoffman
D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000523:psychology*; D000066492:Cognitive Aging; D005260:Female; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D008875:Middle Aged; D009483:Neuropsychological Tests; D011680:Pupil; D013997:Time Factors; D014796:Visual Perception; D055815:Young Adult
DBS; Fornix; Pupillometry; Relational memory; Scan path