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.

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

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.

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.

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.

Since anxiety and mood status may influence gait performance, these factors will be evaluated. For this purpose, the Hospital Anxiety and Depression Scale (HADS) will be used. The HADS consists of 14 items and includes two subscales: anxiety (HADS-A) and depression (HADS-D). Each subscale yields scores ranging from 0 to 21. The cut-off points for the Turkish version are 10 for the anxiety subscale (HADS-A) and 7 for the depression subscale (HADS-D).

Static balance analysis will be performed using the SensorMedica FreeMed (FreeMed, SensorMedica, Rome, Italy) device. The system will be calibrated prior to each assessment. Before testing, participants will be informed about the test procedures. All assessments will be conducted with participants barefoot. Prior to the measurements, participants will be instructed to stand upright, look at a fixed point in front of them, and distribute their body weight evenly on both feet in order to align their center of mass along the midline. For this purpose, participants will be asked to position the point representing their center of pressure, displayed on the device screen, within the marked central cross area on the platform. During the tests, participants will be instructed not to lift or move their feet. Measurements will be performed twice under both eyes-open and eyes-closed conditions, and the mean values will be used for analysis.

An individual's capacity to perform a dual task is defined as dual-task performance. To determine the impact of dual-task conditions on performance, dual-task cost is calculated using measures such as task accuracy and the time required to complete the dual task. Dual-task cost is expressed using the following formula: Dual-Task Cost = [(Dual-Task Performance - Single-Task Performance) / Single-Task Performance] × 100