Age-related loss of early grasp affordance when viewing a safety handle Author: D.W. McDannald1, , M. Mansour2, G. Rydalch3, D.A.E. Bolton1 Mere observation of objects in our surroundings can potentiate movement, a fact reflected by visually-primed activation of motor cortical networks. This mechanism holds potential value for reactive balance control where recovery actions of the arms or legs must be targeted to a new support base to avoid a fall. The present study was conducted to test if there was a difference in activation of motor cortical networks when viewing a wall-mounted safety handle in older adults versus young adults. Here, we used transcranial magnetic stimulation (TMS) to measure corticospinal excitability in hand muscles directly following access to vision while participants performed a seated reach-grasp task. Vision was controlled using liquid crystal lenses and TMS pulses were time-locked to occur shortly after the goggles opened but prior to any cue for movement. Between trials, the response environment was unpredictably altered to present either a handle or no handle (i.e. covered). We hypothesized that the modulation pattern of hand muscle activity following visual access to the safety handle would be attenuated in older adults when compared with young adults. Our results demonstrated that older adults failed to show an affordance effect when viewing the safety handle, in contrast to the clear affordance effect observed in young adults. These findings suggest that aging diminishes our ability to quickly put our visual world into automatic motor terms. If indeed the affordance effect does play a role in allowing for efficient, and timely postural responses to avoid a fall, this would suggest that older adults have a specific deficit in this regard. By failing to prepare arm reactions older adults may be less capable of adapting their actions to avoid a fall in complex, and cluttered (i.e. real-world) settings
