Motor Sequence Learning and Consolidation in Unilateral <i>De Novo</i> Patients with Parkinson’s Disease

<div><p>Previous research investigating motor sequence learning (MSL) and consolidation in patients with Parkinson’s disease (PD) has predominantly included heterogeneous participant samples with early and advanced disease stages; thus, little is known about the onset of potential behavioral impairments. We employed a multisession MSL paradigm to investigate whether behavioral deficits in learning and consolidation appear immediately after or prior to the detection of clinical symptoms in the tested (left) hand. Specifically, our patient sample was limited to recently diagnosed patients with pure unilateral PD. The left hand symptomatic (LH-S) patients provided an assessment of performance following the onset of clinical symptoms in the tested hand. Conversely, right hand affected (left hand asymptomatic, LH-A) patients served to investigate whether MSL impairments appear before symptoms in the tested hand. LH-S patients demonstrated impaired learning during the initial training session and both LH-S and LH-A patients demonstrated decreased performance compared to controls during the next-day retest. Critically, the impairments in later learning stages in the LH-A patients were evident even before the appearance of traditional clinical symptoms in the tested hand. Results may be explained by the progression of disease-related alterations in relevant corticostriatal networks.</p></div

Block Duration in Session 1 (A) and Session 2 (B).

<p>Data points represent group means for each block and error bars depict standard errors. Black squares = healthy controls; blue circles = left hand asymptomatic (LH-A) patients with PD; red crosses = left hand symptomatic patients (LH-S) with PD. Thick solid lines represent group-averaged trajectories based on a single exponential fit.</p

Performance Index (PI) in Session 1 (A) and Session 2 (B).

<p>Data points represent group means for each block and error bars depict standard errors. Black squares = healthy controls; blue circles = left hand asymptomatic (LH-A) patients with PD; red crosses = left hand symptomatic patients (LH-S) with PD. Thick solid lines represent group-averaged trajectories based on a single exponential fit.</p

Experimental Design.

<p>See text for details of each phase. W/U = warm-up.</p

Participant characteristics.

<p>Values are means ± SD. MMSE = Mini Mental State Examination; GDS = Geriatric Depression Scale; UPDRS = Unified Parkinson’s Disease Rating Scale. L-UPDRS III = left side scores of UPDRS part III; R-UPDRS III = right side scores of UPDRS part III. PIGD = postural instability—gait difficulty. PD-dominance was based on method employed in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134291#pone.0134291.ref044" target="_blank">44</a>].</p><p>Participant characteristics.</p