Wednesday, 24 August 2011

Performing and learning 90° in older adults

Despite a wealth of knowledge regarding coordinated rhythmic movements in a healthy population of adolescents and younger adults this is not the case for their older counterparts. Following a review of the minimal literature the understanding of older adult populations appears inconclusive. From reviewing the main two papers similarities between the elderly and young populations are present. Firstly the elderly possess the ability to perform 0° and 180° at relative ease with little to no difference to the younger populations. With both populations able to learn the least stable phase of 90° when exposed to specific training.
However this is where the similarities cease and the differences begin. Despite both groups fully understanding the movement demands of a 90° phase the ability to produce this is diminished in older adults. Firstly older adults are more sensitive to different feedback types than younger adults. For example older adults did not improve when using augmented terminal feedback when the younger adults did. Furthermore, older adults show a greater improvement and retention of 90° when using concurrent augmented feedback when compared to other feedback methods used during training. Additionally learning 90° occurs at a slower rate in older adults, with the elderly initially drawn to perform at 180°; consequently leading to higher error rates during learning 90° in older adults. These error rates exist in variable movement frequencies, amplitudes and reduced accuracy with a 70° variation from the desired movement patterns. Therefore 90° cannot be considered stable but does become more so throughout training. However, the performance difference between the younger participants and the elderly becomes more pronounced with training.
So with poor performance by the elderly present in both papers when compared to the younger participants the question is, why? This may be explained through exploration of the feedback methods. Throughout training both terminal and concurrent augmented feedback was provided using a Lissajous display. In both papers subjects were tested at baseline and post training with differing perceptual information available. They were exposed to normal visual conditions, no vision of the hands and augmented feedback. The greatest performance in retention tests within older adults occurred under augmented concurrent feedback conditions. This was coupled with no significant difference between the no vision of the hands and normal vision conditions. Consequently this suggests that the perception of 90° or the requisite movement information is impeded in older adults. However, in slight contradiction to this, Swinnen et al. (1998) suggest that augmented visual feedback yields greater stability in retention under normal visual conditions. This may still suggest that older adults have improved their perceptual ability and are more able to gain the required requisite information due to training with augmented visual feedback.
In conclusion, by increasing the perceptual information available to older adults, novel coordinated rhythmic movements can be learnt. This may not result in movement stability on a par with younger populations, but yields improved performance when the augmented feedback is removed. However the research remains inconclusive and underwhelming in its amount and requires greater exploration within older adults.
Swinnen, S.P., S.M.P. Verschueren., H. Bogaerts., N. Dounskaia. (1998). Age-related deficits in motor learning and differences in feedback processing during the production of a bimanual coordination pattern. Cognitive neuropsycholocy, 15(5), 439-466.
Wishart, L.R., T.D. Lee., S.J. Cunningham., J.E. Murdoch. (2002). Age-related differences and the role of augmented visual feedback in learning a bimanual coordination pattern. Acta psychological, 110, 247-263.

Tuesday, 9 August 2011

Overloading the system in everyday life

When studying perception-action systems in motor control, coordinated rhythmic movements are frequently used. With difficulty in performing non-0° movements sometimes viewed as a bottleneck in the ability to control movement. Whereby the control of movement is overloaded and consequently successful performance is prevented. However during the study of coordinated rhythmic movements, the tasks employed are often simple and small scale movements. When in reality much more complicated movements are successfully performed frequently and by almost everyone.
To most if not all able bodied people the task of walking could not be considered in any way shape or form intimidating, complicated or challenging. Walking is simply done with very little conscious effort until something perturbs the usual rhythm of walking; such as the need to adapt gait for traversing steps, ice or many different changing terrains for example. However even under these altered conditions walking is rarely considered difficult and successful gait is achieved the vast majority of the time. Furthermore the number of muscles that must be controlled in the off-phase rhythm of walking is far in excess of that used when simply coordinating the movement of a joystick to some external timing source. Therefore it seems irrational to suggest that during simple coordinated rhythmic movements such as controlling a dot on a computer screen the motor control systems of the body become overloaded.
Furthermore on that basis, in typing this, the precise movements of each of my digits with the accuracy required to successfully type letters in specific sequences to construct words would be near impossible. However, despite the lack of a strictly rhythmic nature of the movement it is most certainly coordinated. Whereby the timing of each finger movement may potentially be considered as dictated by the accuracy and timing of the previous finger. Consequently for both novice and expert typers the movement of up to 10 digits in sync with each other should overload the system. However typing on a keyboard and walking have remarkably high success rates. Therefore begging the question, why?
The ability to perform both these tasks may lie in the availability and usefulness of the required feedback. Typing and walking success may be considered examples of successful feedback in line with work by Wilson and Colleagues. In which the use of feedback and changing feedback conditions yields differing movement stability. This may be present in typing as the appearance of the letters and words on the screen is effectively instantaneous feedback, where a comparison of desired movements may be compared to the appearance of a word be it spelt correctly or not; Therefore providing feedback about the movement of the digits used during typing.
Wilson, A.D., W. Snapp-Childs., & G.P. Bingham. (2010). Perceptual Learning Immediately Yields New Stable Motor Coordination. Journal of Experimental Psychology: Human Perception and Performance. 36(6), 1508-1514.
Wilson, A.D., W. Snapp-Childs., R. Coats., & G.P. Bingham. (2010). Learning a Coordinated Rhythmic Movement With Task-appropriate Coordination Feedback. Experimental Brain Research. 205, 513-520.

Monday, 8 August 2011

Perception and coordinated rhythmic movements

When performing or learning skilled behaviour such as coordinated rhythmic movement’s perception and action go hand in hand. However to understand which of these is limiting performance the isolation of either perception or action is required. To achieve this Wilson, Snapp-Childs and Bingham (2010) used two- alternative forced choice judgements (2AFC) and coordinated rhythmic movement performance during their study.
Assessments were performed at baseline and post training. They involved judgement at 90° and 180° and movement at 0° 90° 180°. Further retention tests were performed a week after post training in which just the movement trials were performed. However to assess the role of perception no movement trials were performed during training. Therefore improved movement performance would be due to improved perception. The training consisted of judgement at 90° with up to 14 training sessions or to the point when performance plateaued. A control group did the assessment but no training.
Judgement assessments involved 2AFC at 90° and 180° with no feedback. This consisted of a pair of 2 moving dots with 1 of the pair moving at the target relative phase whilst the other was moving at the same or a different phase. Different phases were +/- 9°, 18°, 27°, 36°, 45°, producing 21 different trial types in randomised order. An additional 1 example assessment was given at the start of the trial
Judgement training was performed at 90°. There was 12 blocks of 2AFC 90° trials per training session. Each block compared 90° to 4 other phases 2 less than and 2 greater than 90°. Trial 1 and 4 were 90° +/- 40° reducing by 10° between each set. Trial 2 and 3 were 90° +/- 20° reducing by 5° between each set. Each of the 4 trials appeared in random order in each block. Feedback was given following judgements. When subjects achieved 85% correct they progressed to the next discrimination set. Maximum of 4 training sessions per set with a maximum 6 received on the last set.

Wilson, A. D., W. Snapp-Childs., & G. P. Bingham. (2010), Perceptual Learning Immediately Yields New Stable Motor Coordination. Journal of Experimental Psychology: Human Perception and Performance. 36(6), 1508-1514.