B – 116 Impact of Processing Speed on Verbal Learning: A Comparative Analysis Across Neurodiagnostic Groups

Abstract Objective To examine the impact of processing speed (PS) on verbal learning and memory in individuals across neurodiagnostic groups. Method This retrospective study analyzed data from 1,073 individuals seen in an outpatient neuropsychology clinic diagnosed with multiple sclerosis (MS; n=120), Parkinson’s disease (PD; n=124), mild cognitive impairment (MCI; n=373), or no cognitive impairment (NCI; n=456). Records with invalid performance or major comorbidities were excluded. All participants completed the California Verbal Learning Test–II (CVLT-II), Trails A (TMTA), and Wechsler Adult Intelligence Scale–Coding subtest (CD). Words recalled across CVLT-II learning trials were modeled using a first-order transfer function estimated via Bayesian mixed non-linear regression. Trial scores were modeled as a non-linear function of attention span (AS) and learning rate (LR), which are estimated using age, education, sex, diagnosis, TMTA raw score, CD scaled score, and diagnosis-by-TMTA and diagnosis-by-CD interactions. Results The model explained 86.62% (95%CI: 86.13-87.09) of the variance in CVLT-II recall. AS was negatively associated with age (β=-0.28), male sex (β=-0.46), MCI (β=-0.90), MS (β=-0.46), PD (β=-0.62), and TMTA (β=-0.14), while education was positively associated with AS (β=0.20) and LR (β=0.09). Unique effects of CD (AS; β=0.42) and TMTA (LR; β=-0.16) emerged only in PD and MS groups. See Figure 1. Conclusion PS affected verbal learning overall but uniquely impacted patients with subcortical profiles (MS, PD). MS or PD patients with intact PS had unimpaired learning curves, but when PS was impaired, they performed similarly to MCI peers. Findings indicate that verbal learning performance is impacted by PS but that these effects meaningfully differ between neurocognitive disorders.