Development of new task

The process of identification of a suitable secondary cognitive task for the dual-task protocol was driven by the following points, which are each discussed:

 Questionnaire results from Chapter 3

 Task that was measurable and a primary outcome  Avoidance of interference from a secondary motor task  Feasibility of the task application whilst walking

Importantly the focus was driven by the outcome of the questionnaire study (see section 3.8) which concluded that an appropriate task would require FES users in the planned study to walk without thinking about walking and/or look around whilst walking.

Secondly, an important point adopted for this thesis was the identification of a secondary task that could be measured and used as an outcome. The potential in adopting this approach would be to quantify the effect of FES on motor-cognitive interference, under dual-task conditions. Furthermore, from the literature reviewed there was a noted inconsistency in the outcomes of dual-task studies reported. Whilst gait parameters were reported by all studies, the performance of task was not always included as an outcome (Eckhardt et al., 2011, Canning et al., 2006). In some cases the tasks were purely utilised to create divided attention and hence there was a focus on ensuring that the task was completed correctly. In a recent review of dual-task studies of older people (Beurskens and Bock, 2012) this point was raised as a methodological issue noting that by ignoring outcomes related to either the task or gait, changes in dual-task performance cannot be distinguished from those due to task prioritisation.

Thirdly, the focus was also driven by avoidance of tasks that would require a verbal response whilst walking. Adopting this type of task would remove the potential interference of articulation on motor-cognitive processes. Thus the task could be described as ‘purely’ involving cognitive processes, without the inclusion of a secondary motor task to interfere with the primary motor task of walking. This type of task would require a response once walking finished, thus reliant upon neural processes involved in memory in order to execute them. This important point regarding task selection directed the choice to those tasks reliant upon memory.

Finally, as in dual-task studies, the feasibility of application of the task during walking was an important factor. This also included taking account of the environment in which the study could take place e.g. the available space within a gait laboratory. Furthermore, it was important to ensure that the creation of a cognitive load did not make the task so difficult that participants were unable to complete the task or that their walking ability was put under excessive duress as to make walking unsafe. The task also needed to be appropriate for a stroke population. These final points were addressed during piloting of the task chosen and the study protocol which is discussed later in the chapter.

These important points were taken into the process of task choice. The initial driver (i.e. questionnaire study outcomes) indicated that FES users would respond to a task that required them to look around whilst walking. By default this would avert their gaze from the walking surface and require a visual stimulus or input. From the review of the tasks used in the dual-task literature, those using visual stimulus tested reaction time (Sparrow et al., 2008) and discrimination (Heller et al., 2000) rather than memory. Thus, the decision was made to consider using an existing neuropsychological test as a task. The following describes the process by which neuropsychological tests were explored and considered, and the task was chosen.

a) Visual task

Existing visual memory tests required a visuomotor response which is typically drawing e.g. Complex Figure Test or Rey-Osterrieth Test (Lezak et al., 2004). In these tests the requirement is to replicate the figure after it is shown. Whilst this may have been appropriate to incorporate into a dual-task study, by projection of the figure onto a screen whilst walking, in a stroke group this type of testing would be

more difficult for those with upper limb effects of stroke and potentially create further participant exclusion criteria. As an alternative, visual recognition tests, which test short-term memory, negated the need for the participant to draw and also allowed figures to be projected on a screen whilst the participant walked. There are several examples of these in the literature, using variations on a format which shows the participant target figures at the beginning of the test and subsequently requires the participant to identify these from amongst a series of foils as the test progresses and further figures are shown e.g. Recurring Figures Test (Kimura, 1963), Continuous Recognition Memory Test (Hannay et al., 1979), Continuous Visual Memory Test (Trahan and Larrabee, 1988), Wechsler Memory Scale – III Faces (Wechsler, 1997).

b) Verbal task

The outcome of the questionnaire study also indicated that FES users would respond to a task that required them to walk without thinking about walking. Thus a cognitive task that diverted their attention from the task of walking would create a cognitive load suitable for a dual-task protocol. This would be achieved by a visual recognition task. But with tasks used in dual-task studies employing visual input in the minority, a decision was made to take forward two memory tasks to piloting. As the majority of tasks reviewed in the literature used a verbal input or stimulus, inclusion of a ‘verbal’ task was identified as appropriate in this context. Either a verbal or visual task would divert attention away from walking and thus potentially provide a measure of the degree to which participants need to think about walking. A ‘common sense’ assessment of both approaches indicates that tasks derived from this dual-focus would potentially be reflective of real life situations occurring whilst walking.

There were some examples from the dual-task literature of tasks requiring a response after walking was complete, drawing upon the cognitive processes involved in memory, and reliant upon verbal stimulus or input (Yogev et al., 2005, Springer et al., 2006, Hyndman et al., 2006). Alternatively, a verbal recognition test, to mirror the format of the visual task, offered a potentially more easily applied and measured verbal task. Amongst available verbal neuropsychological tests there are several recognition tests that expose the participant to target words and then require the participant to identify them when they are paired with another word e.g. Memory Test for Older Adults (Hubley and Tombaugh, 2002), Recognition Memory Test

(Warrington, 1984). Both of these examples of tests also include a visual recognition component that follows the same format of testing.

c) Task development

The format of the Memory Test for Older Adults and the Recognition Memory Test (RMT) were the most appropriate choice for the purposes of creating a cognitive load that tested short-term recognition and could be adjusted for difficulty to avoid excessive cognitive load. In fact Warrington’s Recognition Memory Test (RMT) had been incorporated into The Camden Memory Tests (Warrington, 1986) as a shortened version, indicating that it was possible to develop tests of differing lengths and thus tailor the task to the time spent walking.

Thus two tests were devised, based on the format of the RMT, which tested visual and verbal recognition and taken forward to piloting. The format required participants to walk whilst listening to words spoken (verbal) or looking at figures shown (visual) at two second intervals; this frequency is taken from the Continuous Visual Memory Test. Then, when seated, the participants heard the word paired with another word or saw the figure paired with another figure, in a different order to that in which they were previously heard or shown. They were asked to identify the word or figure that they had heard or seen previously.

In order to be able to score the results in a consistent manner across participants it was important to ensure that similar cognitive processes were involved for all participants when committing the target word or figure to their short-term memory. Words can introduce a number of dimensions into a memory task that can affect test performance e.g. imagery, familiarity, emotion (Lezak et al., 2004). Thus, words of low imagery and of three syllables or less were chosen using a database of words (Wilson, 1988) which could be searched based on these criteria. Similarly, figures that are of familiar objects, flora or fauna would affect test performance. Participants could potentially translate the image into its verbal form, rather than remember it in its image form, resulting in a test of verbal rather than visual memory. Thus, figures were chosen that were abstract and indeterminable using those from the Continuous Visual Memory Test (Trahan and Larrabee, 1988) supplemented by abstract figures drawn by the researcher.

For the piloting process several visual and verbal tests were produced. The words and figures were not repeated during the course of a single gait laboratory session, neither as targets nor as paired foils. Appendices B.2 and B.3 provides examples of the word lists that were played as pre-recorded lists and the figures that were projected on a screen, both at two second intervals. Examples of the paired words and figures, that tested the participants’ memory, are also included.