Biomechanical and cognitive interactions during Visuo Motor Targeting Task

Highlights

• A novel Visuo Motor Targeting Task (VMTT) evaluated cognitive-motor interference.

• VMTT versus target search while standing improved visual performance.

• Higher gait speed during VMTT did not affect the visual performance.

• Margin of stability (MoS) was improved as gait speed increased during VMTT.

• Gait speed, VMTT, their interaction significantly influenced MoS in ML direction.

Abstract

Background

Biomechanical analyses primarily focus on physical aspects of human movement; however, it is not understood how walking is affected while simultaneously performing a demanding cognitive task - a form of Cognitive-Motor Interference (CMI). CMI occurs when performance of a primary task (e.g. walking) is affected following the introduction of a cognitive task (e.g. visual search).

Research question

Would Visuo Motor Targeting Task (VMTT) impair visual search performance and reduce the margin of stability (MoS) at higher gait speeds?

Methods

A protocol was developed to investigate responses of the neuromuscular system while performing a complex visual search task. The Computer Assisted Rehabilitation ENvironment (CAREN, Motekforce Link, Netherlands) system was used for the experimental design. Twenty male participants (Age = 24.2 ± 2.5yrs, Weight = 70.3 ± 10.6 kg, Height = 178.0 ± 9.1 cm) located and pointed towards targets in complex scenes while walking at different gait speeds (0.55, 1.11 and 1.67 m/s.) or while stationary. The cost of visual search during a Visuo Motor Targeting Task (VMTT) was based on the pointing accuracy during the visual search task.

Results

A two-way repeated measure ANOVA showed that MoS in the ML direction significantly improved with increased gait speed and during the visual search task. There was also a significant interaction with MoS improvement being greater during the visual search task at high gait speeds. MoS in the AP was only affected by gait speed. Visual performance and cost of visual search were enhanced during walking versus standing up to 25 %.

Significance

This study investigated CMI at different gait speeds, which may have implications in postural control, falls and other neurological disorders.

Introduction

Gait performance may require some level of cognitive control when accompanied with another task and particularly among those with neuromuscular impairment [[1], [2], [3]]. The interaction between cognitive and motor performance has been studied using dual task paradigms that evaluate cognitive-motor interference (CMI) [1,4]. CMI occurs when the performance during a primary motor task such as gait is affected by a secondary task such as visual search of a target. Patterns of CMI show that performance during single versus dual-tasking can improve, worsen or stay unaffected [5].

The majority of dual tasking studies have focused on the effect of CMI on gait performance by describing the changes in step length, step frequency, joint kinematics and kinetics, and the margin of stability (MoS) [6]. Most previous dual-task studies have measured non-spatial working memory performance (e.g. The N-back, Stroop) at various gait speeds [7]. Such cognitive tasks are not likely to reflect the cognitive demands typically experienced during walking. More realistic tasks such visual search during walking and conscious hand movements (a.k.a eye-hand coordination which we consider as cognitive visual task in this study) are common in daily activities and sports [8,9]. It has been shown that postural control modification enhances visual performance [10] and vice versa [11]. Thus, to simulate more realistic environment of a daily activity, it is important to evaluate the effect of CMI on the cost of visual performance and a measure of gait stability such as margin of stability during complex scenarios such as dual tasking and/or Visuo Motor Targeting Task (VMTT) at various gait speeds [12]. VMTT is referred to as a target search while hand-eye and foot-eye coordination i.e. walking are also involved.

The effect of visual searching has been examined during standing and sitting [13,14]. In a seated scenario versus standing, target search performance has been shown to improve in a friend/foe discrimination task (i.e. Go/No-Go paradigm) [13,15]. However, less is known about the interaction between walking and visual search performance e.g. during VMTT, which has implications for activities of daily living, sport and the military [10,13,16]. Recently, it was observed that participants performed an aurally aided visual search faster (between 180−240 ms) while walking than standing, without any reduction in accuracy [13]. To quantify the degree of CMI, Patel and colleagues [17] developed a metric that calculates the cost of dual tasking by comparing dual- and single-task performances. To date the cost of dual tasking has not been calculated for a demanding visual search task performed while walking.

Thus, the purpose of this investigation was to determine the effect of performing a visual searching task while walking. The following hypotheses were tested i) visual search performance would decrease during Visuo Motor Targeting Task (walking + target search) compared to single tasking (target search while standing or when treadmill belt speed = 0) and ii) faster walking could decrease margin of stability (MoS) in all anatomical directions during VMTT.