RT Journal Article
SR Electronic
T1 Excitatory TMS Boosts Memory Representations
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 279547
DO 10.1101/279547
A1 Wei-Chun Wang
A1 Erik A. Wing
A1 David L.K. Murphy
A1 Bruce M. Luber
A1 Sarah H. Lisanby
A1 Roberto Cabeza
A1 Simon W. Davis
YR 2018
UL http://biorxiv.org/content/early/2018/03/10/279547.abstract
AB Brain stimulation technologies have seen increasing application in basic science investigations, specifically towards the goal of improving memory functioning. However, proposals concerning the neural mechanisms underlying cognitive enhancement often rely on simplified notions of excitation and, most applications examining the effects of transcranial magnetic stimulation (TMS) on functional neuroimaging measures have been limited to univariate analyses of brain activity. We present here analyses using representational similarity analysis (RSA) and encoding-retrieval similarity (ERS) analysis in order to quantify the effect of TMS on memory representations. To test whether an increase in local excitability in PFC can have measurable influences on upstream representations in earlier temporal memory regions, we compared 1Hz and 5Hz stimulation to the left dorsolateral PFC. We found that 10 minutes of 5Hz rTMS, relative to 1Hz, had multiple effects on neural representations: 1) greater RSA during both encoding and retrieval, 2) greater ERS across all items, and, critically, 3) increasing ERS in MTL with increasing univariate activity in DLPFC, and greater functional connectivity for hits than misses between these regions. These results provide the first evidence of rTMS enhancing semantic representations and strengthen the idea that rTMS may affect the reinstatement of previously experienced events in upstream regions.