Abstract
Learning declines with age. Recent evidence indicates that the brainstem may play an important role in learning and motor skill acquisition. Our objective was to determine if delays in the reticular formation, measured via the startle reflex, correspond to age-related deficits in learning and retention. We hypothesized that delays in the startle reflex would be linearly correlated to learning and retention deficits in older adults. To determine if associations were unique to the reticulospinal system, we also evaluated corticospinal contributions with transcranial magnetic stimulation. Our results showed a linear relationship between startle onset latency and percent learning and retention but no relationship between active or passive motor-evoked potential onsets or peak-to-peak amplitude. These results lay the foundation for further study to evaluate if (1) the reticular formation is a subcortical facilitator of skill acquisition and (2) processing delays in the reticular formation contribute to age-related learning deficits.
Highlights
IntroductionOlder adults learn at a slower rate and to a lesser extent than younger adults (Gunning-Dixon et al, 2002; Seidler, 2007; Roig et al, 2014; King, 2016)
The objective of this study was to determine if delays in the startle reflex, which is mediated by the caudal pontine and medullary medullary portions of the reticular formation (Davis and Gendelman, 1977; Davis et al, 1982; Koch et al, 1992; Yeomans and Frankland, 1996), correspond to age-related deficits in learning and retention of a simulated feeding task which has been developed and validated for quantifying age-related deficits in learning and retention
Our results showing a linear relationship with startle onset latency and percent learning and retention lay the foundation for further study to evaluate if (1) the reticular formation is an important subcortical facilitator of skill acquisition and (2) processing in this structure may contribute to age-related learning deficits
Summary
Older adults learn at a slower rate and to a lesser extent than younger adults (Gunning-Dixon et al, 2002; Seidler, 2007; Roig et al, 2014; King, 2016). This population demonstrates a decreased ability to transfer learning from one skill to another (Walter et al, 2019). This is problematic for older adults who are at high risk for neurological disease (e.g., stroke) whose treatment requires significant amounts of therapy to return to daily life. A follow up study, in rodents, shows a disengagement of M1 following long-term training (Hwang et al, 2019) This disengagement is not isolated to rats. Nonhuman primates show dexterous movement following large, gray-matter cortical lesion and expert
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