title: Visual search patterns in semantic dementia show paradoxical facilitation of binding processes.
abstract: While patients with Alzheimer's disease (AD) show deficits in attention, manifested by inefficient performance on visual search, new visual talents can emerge in patients with frontotemporal lobar degeneration (FTLD), suggesting that, at least in some of the patients, visual attention is spared, if not enhanced. To investigate the underlying mechanisms for visual talent in FTLD (behavioral variant FTD [bvFTD] and semantic dementia [SD]) patients, we measured performance on a visual search paradigm that includes both feature and conjunction search, while simultaneously monitoring saccadic eye movements. AD patients were impaired relative to healthy controls (NC) and FTLD patients on both feature and conjunction search. BvFTD patients showed less accurate performance only on the conjunction search task, but slower response times than NC on all three tasks. In contrast, SD patients were as accurate as controls and had faster response times when faced with the largest number of distracters in the conjunction search task. Measurement of saccades during visual search showed that AD patients explored more of the image, whereas SD patients explored less of the image before making a decision as to whether the target was present. Performance on the conjunction search task positively correlated with gray matter volume in the superior parietal lobe, precuneus, middle frontal gyrus and superior temporal gyrus. These data suggest that despite the presence of extensive temporal lobe degeneration, visual talent in SD may be facilitated by more efficient visual search under distracting conditions due to enhanced function in the dorsal frontoparietal attention network.
authors.affiliation: Memory and Aging Center, Department of Neurology, University of California, San Francisco, 350 Parnassus Ave., Ste. 905, San Francisco, CA 94143, USA. iviskontas@memory.ucsf.edu
authors.forename: Indre V
authors.initials: IV
authors.lastname: Viskontas
authors.forename: Adam L
authors.initials: AL
authors.lastname: Boxer
authors.forename: John
authors.initials: J
authors.lastname: Fesenko
authors.forename: Alisa
authors.initials: A
authors.lastname: Matlin
authors.forename: Hilary W
authors.initials: HW
authors.lastname: Heuer
authors.forename: Jacob
authors.initials: J
authors.lastname: Mirsky
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Miller
mesh_terms: D000368:Aged; D000465:Algorithms; D000544:Alzheimer Disease / Q000473:pathology / Q000523:psychology; D001288:Attention / Q000502:physiology; D003116:Color; D005133:Eye Movements / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular; D057174:Frontotemporal Lobar Degeneration / Q000473:pathology / Q000523:psychology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D009801:Oculomotor Muscles / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D011932:Reading; D012438:Saccades / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*