Mapping the “What” and “Where” Visual Cortices and Their Atrophy in Alzheimer's Disease: Combined Activation Likelihood Estimation with Voxel-Based Morphometry

Abstract

The human cortical regions for processing high-level visual (HLV) functions of different categories remain ambiguous, especially in terms of their conjunctions and specifications. Moreover, the neurobiology of declined HLV functions in patients with Alzheimer's disease (AD) has not been fully investigated. This study provides a functionally sorted overview of HLV cortices for processing “what” and “where” visual perceptions and it investigates their atrophy in AD and MCI patients. Based upon activation likelihood estimation (ALE), brain regions responsible for processing five categories of visual perceptions included in “what” and “where” visions (i.e., object, face, word, motion, and spatial visions) were analyzed, and subsequent contrast analyses were performed to show regions with conjunctive and specific activations for processing these visual functions. Next, based on the resulting ALE maps, the atrophy of HLV cortices in AD and MCI patients was evaluated using voxel-based morphometry. Our ALE results showed brain regions for processing visual perception across the five categories, as well as areas of conjunction and specification. Our comparisons of gray matter (GM) volume demonstrated atrophy of three “where” visual cortices in late MCI group and extensive atrophy of HLV cortices (25 regions in both “what” and “where” visual cortices) in AD group. In addition, the GM volume of atrophied visual cortices in AD and MCI subjects was found to be correlated to the deterioration of overall cognitive status and to the cognitive performances related to memory, execution, and object recognition functions. In summary, these findings may add to our understanding of HLV network organization and of the evolution of visual perceptual dysfunction in AD as the disease progresses.

Identifying the Alteration Patterns of Brain Functional Connectivity in Progressive Mild Cognitive Impairment Patients: A Longitudinal Whole-Brain Voxel-Wise Degree Analysis

“…These observations may underlie a relationship between the connectivity change in the right middle occipital gyrus and the disease progression in MCI individuals. Further, as previously mentioned, the rapid FC decrease in the middle occipital gyrus may also emphasize the role of visual cortex disruption in AD progression and is in line with previous evidence of impaired visual perception cortices and related dysfunction ( Cronin-Golomb et al, 1995 ; Mandal et al, 2012 ; Deng et al, 2016 ).…”

Color and contrast vision in mouse models of aging and Alzheimer’s disease using a novel visual-stimuli four-arm maze

“…www.nature.com/scientificreports/ monitoring patients with acquired blue color blindness; however, to our knowledge there are no studies of blue color blindness acquired early in life and AD diagnosis. We cannot preclude the primary visual cortex from being involved in the visual deficiencies in AD, since AD pathologies are detected in these regions as well 68,130,131 . However, the presence of retinal Aβ plaques together with degeneration of RGCs 17,31,132,133 , including melanopsin-containing intrinsically photosensitive RGCs (ipRGCs) 11 , and optic nerve atrophy 134 make the retina a prime candidate in the blue hue distinction defect of AD patients.…”

Structural Brain Correlations of Visuospatial and Visuoperceptual Tests in Parkinson’s Disease

“…Moreover, a recent meta-analysis on the functional MRI studies of normal subjects performing tasks specific to the “what” and “where” streams has identified specific regions according to stimulus type, and also several conjunctive regions in medial and lateral temporal cortices (Deng et al, 2016 ). The lack of retinotopic mapping in our sample hinders the interpretations about higher visual processing regions related to the visual tests.…”