Investigating the Effects of Cognitive Dual-Task on Gait in Individuals With Parkinson's Disease

Global Cognition Assessed by the Montreal Cognitive Assessment

Time Frame: Day 1

The assessment of cognitive functions will begin with the evaluation of global cognition. Global cognition will be evaluated using the Montreal Cognitive Assessment (MoCA). The Montreal Cognitive Assessment is a validated scale designed to assess multiple cognitive functions, including attention, concentration, executive functions, memory, language, visuospatial skills, abstract reasoning, calculation, and orientation. The instrument has a maximum total score of 30 points. According to the original validation study, scores of 26 and above are generally considered to represent normal cognitive function, whereas scores below 26 are reported to indicate potential cognitive impairment. For the purpose of this study, an inclusion criterion of a MoCA score ≥ 21 has been established.

Language Function Assessed by the Boston Naming Test

Time Frame: Day 1

The short form of the Boston Naming Test (BNT), consisting of 15 items (BNT-15), will be used to assess language function. The test comprises images ranging from commonly recognized objects to those that are progressively more difficult to identify. Participants are asked to name the object depicted in each image. If the participant is unable to provide the correct name (e.g., "pelican"), semantic or phonemic cues (e.g., "it is a bird," "pe…") may be provided. The examiner records the type and number of cues required and whether they lead to a correct response. Each correct response is scored as 1 point. The maximum possible score is 15 points, with higher scores indicating better language performance.

Memory Assessed by the Rey Auditory Verbal Learning Test

Time Frame: Day 1

The Rey Auditory Verbal Learning Test (RAVLT) will be used to assess memory. This test evaluates verbal learning, immediate verbal memory, susceptibility to interference, free recall, and recognition memory. Scoring is based on the number of correctly recalled words in each trial, delayed recall performance, and the number of correctly rejected distractor items during the recognition phase. Higher scores across all indices indicate superior verbal learning and memory capacity, while significant discrepancies between immediate and delayed recall may suggest retrieval or storage deficits.

Visuospatial Function Assessed by the Benton Judgment of Line Orientation Test

Time Frame: Day 1

The Benton Judgment of Line Orientation Test (JLOT), will be used to assess visuospatial function. The primary aim of the test is to evaluate the individual's ability to perceive, organize, and relate elements within a visual stimulus according to their spatial orientation. The test consists of 30 items, and task difficulty increases progressively as the line segments are shortened from the top or bottom. Scoring is based on paired responses; a point is awarded only if both lines in a pair are correctly identified. Higher scores indicate superior visuospatial perception and spatial relation skills, whereas lower scores may reflect impairments in right-hemisphere mediated spatial organization.

Executive Function Assessed by the Stroop Test (Çapa Version)

Time Frame: Day 1

The Stroop Test (Çapa Version) will be used to assess executive functions. This test evaluates selective attention, response inhibition, cognitive flexibility, and information processing speed. The test consists of two stimulus cards. The first card includes 60 colored rectangles (red, green, and blue) arranged in six rows of ten items each. The second card contains color words printed in incongruent ink colors in the same format. For each stage, completion time is recorded in seconds using a digital stopwatch, while the number of errors and self-corrections is recorded as counts. The "interference resistance" time (Stroop D) is calculated in seconds using the formula: Stroop D = Stroop C - Stroop B

Attention Assessed by the Digit Span Test

Time Frame: Day 1

The Digit Span Test, a subtest of the Wechsler Memory Scale-Revised, is used to assess attention and concentration. It consists of two components: forward digit span and backward digit span, each associated with different cognitive processes. The scoring was determined by the longest sequence of digits correctly repeated in at least one of the two trials for each level. The maximum attainable span length was 7 for the forward condition and 6 for the backward condition. Based on established norms, the lower limits for normal function were defined as a span of 6 for forward and 4 for backward sequences. The difference between forward and backward digit span should not exceed two digits. Higher scores represent superior working memory and attentional performance.

Analysis of Spatiotemporal Gait Parameters Under Dual-Task Conditions

Time Frame: Day 2

Spatiotemporal gait parameters and variability measures will be assessed using the SensorMedica FreeMed baropodometric platform. Within the scope of gait analysis, each participant will first be asked to walk at a self-selected comfortable speed without any dual-task condition, and baseline spatiotemporal parameters will be recorded. Subsequently, gait will be assessed under predefined cognitive dual-task conditions. In this study, participants will be instructed to walk continuously on the platform without stopping, completing at least 40 steps. To ensure a detailed gait analysis, the following parameters will be recorded and reported independently: Step length (cm), step width (cm), cadence (steps/min), step cycle duration (s), stance and swing phase durations (% of gait cycle), single and double support times (s), and gait variability (CV%). Multiple units will be reported for each specific gait sub-parameter as detailed in the description.

Cognitive Dual-Task Gait Protocol

Time Frame: Day 2

This study evaluates gait performance under five cognitive dual-task conditions targeting language, memory, attention, visuospatial, and executive functions in Parkinson's disease (PD). Tasks were developed based on standardized neuropsychological tests, including the Boston Naming Test, Rey Auditory Verbal Learning Test, Benton Judgment of Line Orientation, Digit Span, MoCA, and Stroop Test. Participants walk at a self-selected pace on a gait platform under seven conditions: single-task, five cognitive dual-tasks, and a motor dual-task. In the single-task condition, participants walk at a comfortable speed. Language tasks involve naming images; memory tasks require recalling word lists; visuospatial tasks involve identifying line orientations; executive tasks require naming ink color of incongruent words; attention tasks involve repeating digit sequences. In the motor task, participants walk while carrying a glass of water.