OBJECTIVE: Visual-processing abnormalities commonly contribute to typical Alzheimer's disease symptoms, but their detailed pathophysiology remains unknown. To investigate why patients with Alzheimer's disease have greater difficulty performing visuoconstructive (magnocellular-dominated) tasks than face- or color-perception (parvocellular-dominated) tasks, the authors measured brain activation in response to a temporally graded visual stimulus (neural stress test) during positron emission tomography. METHOD: The stress test measured regional cerebral blood flow (CBF) in response to a patterned flash stimulus in the resting state (0 Hz in the dark) and at frequencies of 1, 2, 4, 7, and 14 Hz. Ten patients with Alzheimer's disease and 12 age- and sex-matched comparison subjects were studied. RESULTS: The striate response at 7 Hz and 14 Hz (the degree of regional CBF increase from that at 0 Hz) was significantly less in the patients than in the comparison subjects, whereas the change in regional CBF at the lower frequencies did not differ between groups. In bilateral middle temporal association areas activated by motion and dominated by magnocellular input, regional CBF at 1 Hz (the frequency with maximal apparent motion) was significantly greater than at 0 Hz in the comparison subjects but not in the patients. CONCLUSIONS: The magnocellular visual system normally responds to high-frequency input and motion; the failure of response in the striate cortex at high but not low frequencies in the Alzheimer's patients suggests greater magnocellular than parvocellular dysfunction at these levels. Activation failure in the middle temporal areas in the patients supports magnocellular dysfunction. The finding that the Alzheimer's disease group had abnormal visual cortical function emphasizes the importance of clinical visuospatial evaluation of patients with Alzheimer's disease to fully understand symptom production and to plan interventions.
OBJECTIVE:Visual-processing abnormalities commonly contribute to typical Alzheimer's disease symptoms, but their detailed pathophysiology remains unknown. To investigate why patients with Alzheimer's disease have greater difficulty performing visuoconstructive (magnocellular-dominated) tasks than face- or color-perception (parvocellular-dominated) tasks, the authors measured brain activation in response to a temporally graded visual stimulus (neural stress test) during positron emission tomography. METHOD: The stress test measured regional cerebral blood flow (CBF) in response to a patterned flash stimulus in the resting state (0 Hz in the dark) and at frequencies of 1, 2, 4, 7, and 14 Hz. Ten patients with Alzheimer's disease and 12 age- and sex-matched comparison subjects were studied. RESULTS: The striate response at 7 Hz and 14 Hz (the degree of regional CBF increase from that at 0 Hz) was significantly less in the patients than in the comparison subjects, whereas the change in regional CBF at the lower frequencies did not differ between groups. In bilateral middle temporal association areas activated by motion and dominated by magnocellular input, regional CBF at 1 Hz (the frequency with maximal apparent motion) was significantly greater than at 0 Hz in the comparison subjects but not in the patients. CONCLUSIONS: The magnocellular visual system normally responds to high-frequency input and motion; the failure of response in the striate cortex at high but not low frequencies in the Alzheimer'spatients suggests greater magnocellular than parvocellular dysfunction at these levels. Activation failure in the middle temporal areas in the patients supports magnocellular dysfunction. The finding that the Alzheimer's disease group had abnormal visual cortical function emphasizes the importance of clinical visuospatial evaluation of patients with Alzheimer's disease to fully understand symptom production and to plan interventions.
Authors: Mark W Albers; Grover C Gilmore; Jeffrey Kaye; Claire Murphy; Arthur Wingfield; David A Bennett; Adam L Boxer; Aron S Buchman; Karen J Cruickshanks; Davangere P Devanand; Charles J Duffy; Christine M Gall; George A Gates; Ann-Charlotte Granholm; Takao Hensch; Roee Holtzer; Bradley T Hyman; Frank R Lin; Ann C McKee; John C Morris; Ronald C Petersen; Lisa C Silbert; Robert G Struble; John Q Trojanowski; Joe Verghese; Donald A Wilson; Shunbin Xu; Li I Zhang Journal: Alzheimers Dement Date: 2014-07-09 Impact factor: 21.566
Authors: Giuseppe Esposito; Giampiero Giovacchini; Margaret Der; Jeih-San Liow; Abesh K Bhattacharjee; Kaizong Ma; Peter Herscovitch; Michael Channing; William C Eckelman; Mark Hallett; Richard E Carson; Stanley I Rapoport Journal: Neuroimage Date: 2006-12-29 Impact factor: 6.556
Authors: Harald Hampel; Nicola Toschi; Claudio Babiloni; Filippo Baldacci; Keith L Black; Arun L W Bokde; René S Bun; Francesco Cacciola; Enrica Cavedo; Patrizia A Chiesa; Olivier Colliot; Cristina-Maria Coman; Bruno Dubois; Andrea Duggento; Stanley Durrleman; Maria-Teresa Ferretti; Nathalie George; Remy Genthon; Marie-Odile Habert; Karl Herholz; Yosef Koronyo; Maya Koronyo-Hamaoui; Foudil Lamari; Todd Langevin; Stéphane Lehéricy; Jean Lorenceau; Christian Neri; Robert Nisticò; Francis Nyasse-Messene; Craig Ritchie; Simone Rossi; Emiliano Santarnecchi; Olaf Sporns; Steven R Verdooner; Andrea Vergallo; Nicolas Villain; Erfan Younesi; Francesco Garaci; Simone Lista Journal: J Alzheimers Dis Date: 2018 Impact factor: 4.472