Impact of Cognitive Decay on the Ability to Operate Remote-Controlled Devices While Walking

he purpose of gerontechnology is to provide assistivedevices for elderly persons to improve their quality oflife and personal independence. Some of these devicesfunction automatically and thus reduce the cognitivedemand on the user. For example, emergency bracelets notifycaregivers, so there is no need to remember phone numbers oroperate a telephone set, and integrated home control systemsadjust the climate and illumination of rooms in a circadianrhythm without user intervention. In contrast, other assistivedevices are operated by remote control and thus build upontheusers’cognitiveabilities. Forexample, theusersmay haveto press the buttons on a personal digital assistant (PDA) orutter voice commands to operate a desired appliance, house-hold robot, or an entertainment system; this requires them tolearnandcorrectlyrememberwhichcommandoperateswhichdevice in which way, what the meaning of possible visual,acoustic, or tactile feedback messages from that particulardeviceis,andhowtorespondtosuchmessages.When designing assistive devices that depend on the users’cognition, one should bear in mind that cognitive abilitiesdecline in old age, and seniors, therefore, might experienceproblems when operating such devices. Different cognitivefunctions are differently sensitive to aging. For example, fluidintelligence (which reflects reasoning skills)starts todecline inthethirddecadeoflife,whereascrystallizedintelligence(whichreflects knowledge base) continues to increase until the sixthdecade [1]. Semantic memory (which encodes facts of generalknowledge) is largely preserved in old age, whereas episodicmemory (which encodes personal experience) declines dis-tinctlyinseniors [2]. Ofparticularinterestfor gerontechnologyisthe prominent age-related decay ofexecutive functions,suchasdecision-making,inhibitionofundesiredorrepetitivebehav-ior, and management of multiple tasks [3]–[7]. The neuroana-tomical basis of that decay is well established: executivefunctions reside inthe prefrontalcortexof the human brain [8],which is particularly vulnerable to age-related shrinkage [9],[10];accordingly,prefrontalshrinkageandexecutivedecayarewellcorrelatedinseniors[3]. To appreciate the impact of executive decay on gerontech-nology, consider the elderly inhabitant of a ‘‘smart house’’who walks from the living room toward the bedroom toundress for a bath while producing remote control commandstoopenthewatertap,setthevolumeandtemperatureofwater,and open the bedroom door. In this scenario, locomotion andremote control are two distinct but concurrent activities, andthe prefrontal cortex, therefore, will be heavily involved inscheduling and coordinating them and in distributing theavailable processing capacity among them. Because the pre-frontalfunctionsarediminishedinoldage,theinhabitantmaybe unable to adequately manage the two concurrent activitiessuch that the performance on one or both activities will suffer[11]. Theconsequences couldbesevereifwalkingisaffected:the elderly person may stumble, fall, and suffer injuries. If so,gerontechnology would defeat its own goal of improving theindependenceandqualityoflifeintheelderly.Indeed, the ability to manage concurrent tasks is degradedinoldage[6],[12],[13],butitisunclearyetwhetherthisdefi-cit also manifests when one of the two tasks is locomotion.Most available studies that combined a walking and a non-walking task suffer from a methodological flaw: they quanti-fied the subjects’ performance on only one of the two tasksand therefore confounded the deficits of task managementwithtaskpriorities.Forexample,whentheoldersubjectsslowdown more than the younger ones under dual-task conditions,this could reflect a cognitive impairment, but it could alsoindicate that seniors prioritized the nonregistered task at theexpense of the registered one. Three available studies quanti-fied the performance on both tasks: one combined walkingwith a simple button-press task in response to a tone [14], andthe other two with a highly complex word-memorizing task,whichhadtobepretrainedoverseveralsessions[15],[16]. Allthree studies found that under dual-task conditions, the walk-ing speed did not change, but the performance on the non-walking task decreased. The magnitude of this reduction wasindependent of age for the simple nonwalking task [14] butwas more pronounced in the elderly for the highly complexnonwalking task [15], [16]. These findings suggest that walk-ing under dual-task conditions is cognitively demanding, thatboth age groups prioritized walking over the second task, andthat the seniors are at a disadvantage only if the second task iscomplex. We reexamine this issue to increase the availabledatabaseandtoextendittosecondtasksofmoderatedifficulty