Parkinson's patients delay fixations when circumventing an obstacle and performing a dual cognitive task.

BACKGROUND: People with Parkinson's disease (PD) do not differ from neurologically healthy individuals in obstacle circumvention during walking, therefore they are able to use visual feedback adequately to control motor behavior in this task. However, individuals are often distracted by the secondary task when circumventing an obstacle. An increased cognitive load can require prolonged gaze fixation time on a location of interest to compensate for longer information processing duration. RESEARCH QUESTION: To investigate the effects of cognitive dual tasking (DT) on gaze behavior during waking with obstacle circumvention in people with PD and control group, and to determine the impact of gaze behavior on motor strategy. METHODS: Fifteen individuals with PD (PD-group) and 15 neurologically healthy individuals walked at a self-selected speed over a walkway and circumvented an obstacle centered in the walkway. The experimental conditions (5 trials each one) included obstacle circumvention without DT (OC) and obstacle circumvention with DT (OCDT). In the cognitive task, the participant mentally counted the number of times a target number appeared in an audio recording. We analyzed gaze behavior (i.e. number of gaze fixations and duration on the ground and obstacle), standard gait measures and DT cost. Two-way ANOVAs were completed for gait parameters and moment of fixation. RESULTS: There was no significant difference in DT cost between groups and no obstacle contacts. The participants performed a longer mean duration of fixations on the ground during OCDT compared to OC. Group x condition interactions indicated that the PD-group delayed the obstacle fixation relative to the NHI for OCDT (p < 0.001) and presented greater medial-lateral body clearance (p < 0.001) and longer double support time (p < 0.001) during OCDT compared to OC. SIGNIFICANCE: The results of this study suggest that deficits in locomotion during DT in PD-group may be caused, at least in part, by a reduced ability to fixate gaze at appropriate times during walking.

Gaze position interferes in body sway in young adults.

Postural control is influenced by eye movements. Gaze fixation, which comprises a component of ocular vergence, is important in the acquisition of highly specific task information, but its relation to postural control is little investigated. The aim of the study was to investigate the effects of gaze fixation position (central and lateral fixations) on postural sway in young adults. Forty young adults with ages ranging from 20 to 35 years were invited to participate in the study. Postural sway was measured in quiet stance in bipedal support in three 60-s trials under the following conditions: gaze fixation on a target positioned in front of participant, gaze fixation on a target positioned on right side of participant, and gaze fixation on a target positioned on left side of participant. The following center of pressure parameters (COP) in the anteroposterior (AP) and mediolateral directions (ML) were analyzed for each of the trials: body sway displacement, mean velocity of sway, root mean square (RMS) of sway, and median frequency. In addition, detrended fluctuation analysis (DFA) exponent, in anteroposterior and medio-lateral directions, was calculated. The COP presented greater AP and ML displacement (p<0.03, effect size=1.37; and p<0.03, effect size=1.64, respectively) and RMS AP and ML (p<0.04, effect size=1.66; and p<0.02, effect size=2.50, respectively) for lateral gaze fixation compared to central gaze fixation. These results suggest that gaze fixation on a laterally positioned target increases body sway in anteroposterior and mediolateral directions.

The motor deficits caused by parkinson's disease are not able to block adjustments for a safe strategy during obstacle crossing in individuals with moderate disease / O déficit motor causado pela doença de parkinson não é capaz de bloquear os ajustes para uma estratégia segura durante a travessia de obstáculos em indivíduos com doença moderada / El déficit motor causados por la enfermedad de parkinson no es capaces de bloquear los ajustes para una estrategia de seguridad durante la travesía del obstáculo en individuos con enfermedad moderada

The aim of this study was to verify whether patients with Parkinson's disease (PD) are able to adjust their motor behavior according to restrictions imposed by the task instruction during walking with obstacle crossing. Eighteen elderly people (moderate motor compromise) with a diagnosis of PD walked on a pathway and cross an obstacle according to the following conditions: walking at preferred velocity; walking at maximum vertical elevation of the feet to cross the obstacle; walking at maximum step length to cross the obstacle; walking at maximum velocity. The modulations were directly related to the instructions provided to patients with PD before performing each task, which seems to indicate that attentional cues can influence and benefit strategies during obstacle crossing. In conclusion, patients with PD are able to adjust walking during obstacle crossing according to instructions given to them, which increases their safety.

O objetivo deste estudo foi verificar se pacientes com doença de Parkinson (DP) são capazes de modular o comportamento motor de acordo com restrições impostas pela instrução na tarefa de ultrapassagem de obstáculo. Dezoito idosos com diagnóstico de DP (comprometimento motor moderado) andaram sobre uma passarela e ultrapassaram um obstáculo de acordo com as seguintes instruções: velocidade preferida; elevação máxima do pé para ultrapassagem do obstáculo; máximo comprimento do passo de ultrapassagem; ultrapassagem em máxima velocidade. As modulações realizadas estão diretamente relacionadas às instruções dadas aos pacientes antes da realização de cada tarefa, o que indica que dicas auditivas podem influenciar e beneficiar as estratégias utilizadas. Através deste estudo é possível concluir que pacientes com DP são capazes de modular a ultrapassagem de obstáculo de acordo com a instrução que lhes é dada, o que aumenta a segurança na tarefa.

El objetivo de este estudio fue verificar se los pacientes con enfermedad de Parkinson (EP) son capaces de modular el comportamiento motor de acuerdo con restricciones impuestas por la instrucción en la tarea de sobrepasar un obstáculo. Dieciocho adultos mayores con diagnóstico de EP (con deficiencia motora moderada) caminaran sobre una pasarela e sobrepasaran un obstáculo de acuerdo con las siguientes instrucciones: velocidad preferida; elevación máxima del pie para sobrepasar el obstáculo, máxima distancia del paso para sobrepasar el obstáculo; sobre pasada máxima velocidad. Las modulaciones realizadas están directamente relacionadas a las instrucciones dadas a los pacientes antes de la realización de cada tarea, lo que indica que pautas auditivas pueden influenciar e beneficiar las estrategias utilizadas. A través de este estudio se puede concluir que pacientes con EP son capaces de modular la sobrepasada de obstáculo de acuerdo con la instrucción que les es dada, lo que aumenta la seguridad en la tarea.