Imagine a mind like a complex maze, where multiple circuits intertwine and connect to determine how we perceive and navigate through the world. In the case of visuospatial tests and the cognitive decline seen in behavioral variant frontotemporal dementia (bvFTD), unraveling these circuits becomes crucial. Recent research has shed light on three main pathways that emerge from the dorsal ‘where’ route in our brain, each playing a role in visuospatial functioning: the parieto-prefrontal pathway, parieto-premotor circuit, and parieto-medial temporal connection. However, understanding the neural basis of these cognitive tasks and why bvFTD spares visuospatial abilities remains a mystery. This study set out to explore the differences in cognitive and neural mechanisms underlying visuospatial performance between bvFTD and Alzheimer’s disease (AD) patients. Through a comprehensive assessment of neuropsychological tests, brain imaging techniques, and extensive participant enrollment, the researchers discovered distinct patterns. Interestingly, patients with AD struggled more in visuospatial tasks during the mild dementia stage rather than in the prodromal phase. Executive functioning tests showed stronger correlations with visuospatial abilities in bvFTD, particularly in relation to a complex figure-recognition test called ROCF. Moreover, the researchers identified specific regions in the frontal cortex, including the superior and medial frontal gyri, supplementary motor area, insula, and middle cingulate gyrus, that were associated with visuospatial performance in bvFTD patients. By connecting these findings with existing knowledge on brain anatomy and function, we gain deeper insights into how prefrontal and premotor regions are involved in processing visuospatial information through their connections with the posterior parietal cortex and other posterior cortical regions. These results highlight the importance of interpreting visuospatial deficits cautiously when evaluating bvFTD patients, as they may not necessarily indicate dysfunction solely in the posterior cortical areas. To dive even deeper into the fascinating world of visuospatial cognitive processes and their impact on dementia, be sure to explore the full research article!

BackgroundRecent models of visuospatial functioning suggest the existence of three main circuits emerging from the dorsal (“where”) route: parieto-prefrontal pathway, parieto-premotor, and parieto-medial temporal. Neural underpinnings of visuospatial task performance and the sparing of visuospatial functioning in bvFTD are unclear. We hypothesized different neural and cognitive mechanisms in visuospatial tasks performance in bvFTD and AD.MethodsTwo hundred and sixteen participants were enrolled for this study: 72 patients with bvFTD dementia and 144 patients with AD. Visual Object and Space Perception Battery Position Discrimination and Number Location (VOSP-PD and VOSP-NL) and Rey-Osterrieth Complex Figure (ROCF) were administered to examine visuospatial functioning, together with a comprehensive neuropsychological battery. FDG-PET was acquired to evaluate brain metabolism. Voxel-based brain mapping analyses were conducted to evaluate the brain regions associated with visuospatial function in bvFTD and AD.ResultsPatients with AD performed worst in visuospatial tasks in mild dementia, but not at prodromal stage. Attention and executive functioning tests showed higher correlations in bvFTD than AD with ROCF, but not VOSP subtests. Visuospatial performance in patients with bvFTD was associated with bilateral frontal regions, including the superior and medial frontal gyri, supplementary motor area, insula and middle cingulate gyrus.ConclusionThese findings support the role of prefrontal and premotor regions in visuospatial processing through the connection with the posterior parietal cortex and other posterior cortical regions. Visuospatial deficits should be interpreted with caution in patients with bvFTD, and should not be regarded as hallmarks of posterior cortical dysfunction.

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