Lateralized Readiness Potentials Reveal Motor Slowing in the Aging Brain

Abstract

Older adults consistently show slower reaction times (RTs) to the onset of motion. Both cognitive slowing and motor slowing have been suggested as causes of this effect. The lateralized readiness potential (LRP) of the electroencephalogram can be used to separate perceptual and decision processes from motor programming and execution as causes of RT differences. We used the LRP to discern the origin of slowing in RT to motion onset that occurs in elderly individuals. After the onset of motion in a visual display, we asked participants to identify the direction of that motion (up or down) by pressing a button. Older participants showed significantly slower RTs than did younger participants. The LRP showed that the bulk of slowed response arose from slowed motor processes, rather than perceptual processing. We discuss the differences found in amplitude and onset latency of the LRP in the context of theories of motion processing and inhibition in the aging brain.

Prefrontal hyperactivity in older people during motor planning

“…The latter effect is known as "the complexity effect", which indicates that slowing is not constant across tasks but increases with task complexity (see Salthouse, 2000 for a review). Other studies have shown an increase of LRP amplitudes in older, compared to younger, adults despite a lack of difference between groups in the onset of the LRPs (Roggeveen et al, 2007;Sterr and Dean, 2008), supporting the idea that greater amplitudes might reflect more inhibitory failures.…”

“…The overall alpha level was fixed at 0.05 after the Geisser-Greenhouse correction. Furthermore, given the well-known age-related behavioral slowing (indexed by RTs; i.e., Vallesi et al, 2009) and the slowing of the cognitive processing required by the task (indexed by its electrophysiological marker, the P3 peak latency; i.e., Roggeveen et al, 2007), we explored the relationship between those variables and the BP peak latency, which we considered a sensitive index of executive functions. Thus, correlations (Pearson's r coefficients) were computed, separately for the SRT and the DRT tasks, between age and RT and between RT and P3 and BP latencies, with particular focus on the older group.…”

Age-related Differences in Corticomotor Excitability and Inhibitory Processes during a Visuomotor RT Task

“…Because RT is a good indicator of the functional integrity of the CNS, RT slowing has been associated with age-related decline in central information processing including sensorimotor integration and motor generation (Yordanova, Kolev, Hohnsbein, & Falkenstein, 2004). A number of recent studies have suggested that the major source of slowing with age may be the degradation of motor response generation processes, rather than delays in stimulus processing or response selection (Roggeveen, Prime, & Ward, 2007;Yordanova et al, 2004). In these studies motorrelated potentials of EEG indicated that the RT delay in older adults was associated with mechanisms relating to the activation of contralateral motor areas responsible for triggering the responding effector Yordanova et al, 2004).…”

Age-related differences in corticospinal excitability during a choice reaction time task

“…Recent EEG studies have shown that brain activity related to anticipation, preparation, and/or generation of motor responses is changed in healthy aging (Falkenstein et al 2006;Golob et al 2005;Roggeveen et al 2007;Sailer et al 2000;Sterr and Dean 2008;Yordanova et al 2004). More specifically, Sterr and Dean (2008) showed that increased negativity of contingent negative variations (CNVs) in younger individuals during the preparatory period of a precued choice reaction time (CRT) task was associated with higher recruitment of the frontal brain network and lateralized activation over motor regions, whereas these trends were not seen in older individuals.…”

“…More specifically, Sterr and Dean (2008) showed that increased negativity of contingent negative variations (CNVs) in younger individuals during the preparatory period of a precued choice reaction time (CRT) task was associated with higher recruitment of the frontal brain network and lateralized activation over motor regions, whereas these trends were not seen in older individuals. Observations from studies using lateralized readiness potentials (LRPs) and/or event-related potentials (ERPs) have suggested that behavioral slowing is mainly due to slower response generation, rather than response selection and stimulus processing (Falkenstein et al 2006;Roggeveen et al 2007;Yordanova et al 2004). Specifically, behavioral slowing in elderly individuals may be due to an enhanced and prolonged activity in the contralateral motor cortex during response generation (Falkenstein et al 2006;Yordanova et al 2004).…”