Connelly, W. | Search bioRxiv

bioRxiv2026

Large-scale Visuomotor Reaction Time Self-Testing Reveals Subtle Motor Changes in Older Adults with Subjective Cognitive Impairment

IntroductionAffordable tools for early Alzheimers disease (AD) detection could support drug development and early intervention. Subtle motor changes may indicate preclinical AD, but hand response selection and initiation speeds are understudied. This study assessed whether unsupervised, online visuomotor reaction time (RT) tests relate to subjective cognitive impairment (SCI), a validated high risk state for future conversion to AD MethodsA total of 910 participants (age 66.3{+/-}7.5, 70.8% female) completed assessments of simple and choice visuomotor RT tests at home as part of the online TAS Test protocol; they also completed the Cambridge Neuropsychological Test Automated Battery (CANTAB) episodic memory and executive function tests. Among them, 142 participants reported SCI. ResultsOn the TAS Test visuomotor tests, SCI was associated with 8.4% [1.4%, 15.4%] longer RT ( (p = .008; adjusted for task complexity), greater odds of time-out failure (OR = 1.35 [1.01, 1.81]; p = .037), and greater variance in RT (log-variance (SCI - comparison) = .094 [.028, .159]; p < .001). There were no significant differences between the SCI and comparison groups on any of the CANTAB tests. After adjusting for SCI status, none of the CANTAB tests were significantly associated with RT. DiscussionSCI was associated with longer and more variable visuomotor RT, and greater odds of time-out failure, while not being associated with tests of memory and executive function. Cognitive test scores did not explain a significant amount of variance in visuomotor RT. Taken together, these results support a hypothesis that people with SCI may be experiencing earlier visuomotor deficits that are distinct from (or precede) decline in episodic memory and executive function. Visuomotor tasks that record RT may be more sensitive to preclinical manifestations of cognitive decline than more traditional tests of cognitive function.

bioinformatics↗

bioRxiv2025

The functional organization of retrosplenial feedback to V1

Cortical feedback from higher frontal and association areas to early sensory cortex is thought to contribute to a range of cognitive processes in which sensory signals are processed in a context sensitive manner. Despite the ubiquity of feedback circuitry in the cortex, the information carried by feedback connections, and the principles governing how it is targeted from area to area remains poorly understood. Here we characterized the functional properties of a prominent feedback circuit which links retrosplenial cortex (RSC) and primary visual cortex (V1). We found that RSC[->]V1 axons relay retinotopically selective signals to V1 which at a coarse scale match the region of the V1 retinotopic map innervated, were tuned for spatial and temporal frequency, but not tuned for orientation. Two-color imaging of RSC[->]V1 boutons and local L2/3 V1 neurons further revealed that at a finer scale RSC[->]V1 bouton receptive fields are systematically offset relative to those of V1 in the nasal direction, consistent with RSC[->]V1 boutons conveying signals predictive of upcoming V1 activity in the retinotopic region innervated during forward movement.

neuroscience↗