Imagine your brain as a bustling city with different neighborhoods and highways connecting them. In Parkinson’s disease, the roads that support spatial cognition start to crumble, leaving residents confused and disoriented. But how does this affect other cognitive abilities and motor skills? A recent study used functional MRI to explore the abnormal connections in the brains of cognitively normal individuals with Parkinson’s disease. They discovered two distinct patterns: one of decreased connectivity with other brain regions as spatial demands increased, and another of increased connectivity in unconventional areas. These patterns had a significant impact on cognitive and motor progression. Those who showed the control pattern experienced greater cognitive decline, while those with the unconventional pattern had less decline and potentially used alternative brain areas. Interestingly, certain patterns also predicted changes in motor disability, such as postural instability and gait disturbance. The findings highlight the importance of functional connectivity in understanding cognitive and motor impairment in Parkinson’s disease. To learn more about this fascinating research, check out the original article.

BackgroundSpatial cognition deteriorates in Parkinson’s disease (PD), but the neural substrates are not understood, despite the risk for future dementia. It is also unclear whether deteriorating spatial cognition relates to changes in other cognitive domains or contributes to motor dysfunction.ObjectiveThis study aimed to identify functional connectivity abnormalities in cognitively normal PD (PDCN) in regions that support spatial cognition to determine their relationship to interfacing cognitive functions and motor disability, and to determine if they predict cognitive and motor progression 2 years later in a PDCN subsample.MethodsSixty-three PDCN and 43 controls underwent functional MRI while judging whether pictures, rotated at various angles, depicted the left or right hand. The task activates systems that respond to increases in rotation angle, a proxy for visuospatial difficulty. Angle-modulated functional connectivity was analyzed for frontal cortex, posterior cortex, and basal ganglia regions.ResultsTwo aberrant connectivity patterns were found in PDCN, which were condensed into principal components that characterized the strength and topology of angle-modulated connectivity. One topology related to a marked failure to amplify frontal, posterior, and basal ganglia connectivity with other brain areas as visuospatial demands increased, unlike the control group (control features). Another topology related to functional reorganization whereby regional connectivity was strengthened with brain areas not recruited by the control group (PDCN features). Functional topologies correlated with diverse cognitive domains at baseline, underscoring their influences on spatial cognition. In PDCN, expression of topologies that were control features predicted greater cognitive progression longitudinally, suggesting inefficient communications within circuitry normally recruited to handle spatial demands. Conversely, stronger expression of topologies that were PDCN features predicted less longitudinal cognitive decline, suggesting functional reorganization was compensatory. Parieto-occipital topologies (control features) had different prognostic implications for longitudinal changes in motor disability. Expression of one topology predicted less motor decline, whereas expression of another predicted increased postural instability and gait disturbance (PIGD) feature severity. Concurrently, greater longitudinal decline in spatial cognition predicted greater motor and PIGD feature progression, suggesting deterioration in shared substrates.ConclusionThese novel discoveries elucidate functional mechanisms of visuospatial cognition in PDCN, which foreshadow future cognitive and motor disability.

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