Visual search and the aging brain: discerning the effects of age-related brain volume shrinkage on alertness, feature binding, and attentional control.
OBJECTIVE
Decline in visuospatial abilities with advancing age has been attributed to a demise of bottom-up and top-down functions involving sensory processing, selective attention, and executive control. These functions may be differentially affected by age-related volume shrinkage of subcortical and cortical nodes subserving the dorsal and ventral processing streams and the corpus callosum mediating interhemispheric information exchange.


METHODS
Fifty-five healthy adults (25-84 years) underwent structural MRI and performed a visual search task to test perceptual and attentional demands by combining feature-conjunction searches with "gestalt" grouping and attentional cueing paradigms.


RESULTS
Poorer conjunction, but not feature, search performance was related to older age and volume shrinkage of nodes in the dorsolateral processing stream. When displays allowed perceptual grouping through distractor homogeneity, poorer conjunction-search performance correlated with smaller ventrolateral prefrontal cortical and callosal volumes. An alerting cue attenuated age effects on conjunction search, and the alertness benefit was associated with thalamic, callosal, and temporal cortex volumes.


CONCLUSIONS
Our results indicate that older adults can capitalize on early parallel stages of visual information processing, whereas age-related limitations arise at later serial processing stages requiring self-guided selective attention and executive control. These limitations are explained in part by age-related brain volume shrinkage and can be mitigated by external cues.
Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, and Neuroscience Program, SRI International, Menlo Park, California 94305-5723, USA. evamoe@stanford.edu
Eva M
EM
Müller-Oehring
Tilman
T
Schulte
Torsten
T
Rohlfing
Adolf
A
Pfefferbaum
Edith V
EV
Sullivan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000473:pathology*; D016009:Chi-Square Distribution; D003463:Cues; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011601:Psychophysics; D011930:Reaction Time; D014796:Visual Perception / Q000502:physiology*