P238 Working memory enhancement in young and older adults using rTMS

• Published in: Clinical neurophysiology 2017-03, Vol.128 (3), p.e131-e131
• Main Authors: Luber, B, Davis, S, Lisanby, S.H
• Format: Article
• Language: English
• Subjects: Neurology
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2016.10.354

Question A great deal of the cognitive decline due to aging can be explained by decline in working memory (WM). Our previous work has demonstrated a TMS paradigm which has enhanced WM performance in young adults and has remediated WM deficits in the context of sleep deprivation. Methods Here, following an initial fMRI session to obtain individual cortical targets, two groups, older adults ( N = 17) and younger adults ( N = 17), performed a delayed-match-to-sample WM task while 5 Hz rTMS was applied during the 7 s delay period in the task. As part of a repeated measures design, across four TMS sessions each subject received active or sham rTMS, targeted to either left lateral occipital complex (LOC) or left premotor cortex (PMC) using individualized fMRI targeting. Results There were Site × TMS interactions for both %Correct and reaction time (RT) ( p < 0.025 for both measures) across both groups. Both groups showed speeded RT relative to sham ( p < 0.05) with LOC stimulation, while showing slowed RT and lower accuracy with stimulation to PMC. In a second follow up experiment, rTMS was applied to PMC prior to task onset instead of during the delay period, using the same subjects, who were brought back for two sessions of active and sham TMS. This time, instead of disrupted performance, young but not older adults showed enhanced accuracy and RT (both p < 0.025) with PMC stimulation. Conclusions The opposing results of PMC stimulation prior to task onset or during the delay period demonstrate the sensitivity of task phase as to when to apply TMS to produce cognitive enhancement. Our interpretation of the results is that TMS to PMC during the delay period most likely disrupted ongoing verbal rehearsal, a phonological loop process known to rely on this region, while stimulation prior to such processing augmented that processing in young adults. For LOC, TMS during the delay period likely enhanced processing occurring during the test phase of the WM task in both age groups. Processing in the LOC may act as part of the visuo-spatial scratchpad, which, along with the phonological loop, are two components of WM suggested by Baddeley in his model of WM. These results encourage our continuing work to use TMS to remediate WM deficits found with aging.