| The purpose of this project was to examine limitations of human motor control during postural recovery. A dual task paradigm, the Psychological Refractory Period (PRP), was used to overload the attentional resources of a group of young (20--35 yrs.) and older (70--85 yrs.) adults. Specifically, the intention was to identify age-related differences associated with the selection of an appropriate rapid, discrete muscular response concurrent to the execution of an automatic (non-attention demanding) postural response. Subjects were required to respond as quickly and accurately to two closely presented stimuli; a precision grip force task (HHFT) and toes-up perturbation, respectively. Reaction time and the waveform integrals for each task were analyzed using a 3 (SOA) x 2 (conditions) x 2 (age-groups) mixed model repeated measures ANOVA. Participants apparently restructured the task requirements so posture could be equilibrated, but at a cost of reduced speed and accuracy of the primary task. Also, MLR and LLR amplitudes were greater as the SOA shortened. Data suggest that young and elderly grouped the griping response with the APR. The primary stimulus appeared to be a primer to prepare both responses for the platform rotation trigger. It was concluded that postural recovery is attentionally demanding. Moreover, this study reinforces the notion that postural recovery involves feedforward as well as feedback control mechanisms. Effects of the interference task on postural mechanisms may depend upon the underlying mechanisms of motor control rather than manipulation of sensory modalities. |
