Enhancement of Phonological Memory Following Transcranial Magnetic Stimulation (TMS)

Abstract

Phonologically similar items (mell, rell, gell) are more difficult to remember than dissimilar items (shen, floy, stap), likely because of mutual interference of the items in the phonological store. Low-frequency transcranial magnetic stimulation (TMS), guided by functional magnetic resonance imaging (fMRI) was used to disrupt this phonological confusion by stimulation of the left inferior parietal (LIP) lobule. Subjects received TMS or placebo stimulation while remembering sets of phonologically similar or dissimilar pseudo-words. Consistent with behavioral performance of patients with neurological damage, memory for phonologically similar, but not dissimilar, items was enhanced following TMS relative to placebo stimulation. Stimulation of a control region of the brain did not produce any changes in memory performance. These results provide new insights into how the brain processes verbal information by establishing the necessity of the inferior parietal region for optimal phonological storage. A mechanism is proposed for how TMS reduces phonological confusion and leads to facilitation of phonological memory.

On the role of the supramarginal gyrus in phonological processing and verbal working memory: Evidence from rTMS studies

“…Price, Moore, Humphreys, & Wise, 1997) underlie much of the support for the SMG as a major contributor to phonological processing. Similar results documenting the involvement of the SMG in phonological processing using different tasks and stimuli (serial recall with visually presented pseudowords (Kirschen, Davis-Ratner, Jerde, Schraedley-Desmond, & Desmond, 2006), homophone judgments with visually presented words (Stoeckel, Gough, Watkins, & Devlin, 2009), syllable counting with visual and auditorily presented words and, rhyming judgment with visually presented words (Sliwinska, Khadilkar, Campbell-Ratcliffe, Quevenco, & Devlin, 2012)), have been reported in TMS experiments although the type of effect (inhibitory, facilitatory) varied depending on stimulation parameters (rTMS versus single pulse).…”

“…J. Price, et al, 1997) and verbal working memory (Awh, et al, 1996;Barch & Csernansky, 2007;Jonides, et al, 1998;Kirschen, et al, 2006;Koelsch, et al, 2009;McKenna, et al, 2013;Paulesu, Frith, & Frackowiak, 1993;Paulesu, et al, 1996;Salmon, et al, 1996;Smith & Jonides, 1999;Smith, et al, 1996), while TMS studies have provided evidence regarding the involvement of the left and right SMG during phonological processing Romero, et al, 2006;Stoeckel, et al, 2009), but based on these studies, the possibility that the experimental tasks used also recruited verbal working memory processes cannot be discounted. To gain a better understanding of the role of the left and right SMG in both verbal WM and phonological processing, we conducted two TMS experiments to test hypotheses regarding the contribution of the left and the right SMG to phonological encoding and verbal WM separately.…”

“…Interestingly, apart from the evidence regarding the involvement of the SMG in tasks targeting phonological processing, there is also accumulating evidence from brain imaging studies that suggests that the SMG is also recruited during verbal working memory tasks (VWM) (for a review, please refer to Awh, Jonides, Shumacher, Koppe, & Katz, 1996;Barch & Csernansky, 2007;Jonides, et al, 1998;Kirschen, et al, 2006;Koelsch, et al, 2009;McKenna, Brown, Drummond, Turner, & Mano, 2013;Paulesu, et al, 1996;Salmon, et al, 1996;Smith & Jonides, 1999;Smith, Jonides, & Koeppe, 1996).…”

Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex enhances working memory

“…Transcranial magnetic stimulation (TMS), introduced nearly 20 years ago, offers a promising alternative for cognitive enhancement in healthy individuals (Luber and Lisanby 2014). While most TMS protocols were originally developed for therapeutic purposes in psychiatry and neurology (Hoy and Fitzgerald 2010;McKinley et al 2012), studies on healthy individuals have demonstrated success in facilitating visual spatial attention (Hilgetag et al 2001;Thut et al 2005), visual search (Hodsoll et al 2009), mental rotation (Klimesch et al 2003), analogical reasoning (Boroojerdi et al 2001), phonological recall (Kirschen et al 2006), and abilities in drawing Young et al 2004), and mathematics, calendar calculating and proofreading (Young et al 2004).…”

Enhancing Warfighter Cognitive Abilities with Transcranial Magnetic Stimulation: A Feasibility Analysis

“…Researchers at Stanford demonstrated enhancement of phonological memory following TMS (Kirschen et al, 2006). Based on the premise that phonologically similar items (i.e., "mell, rell, gell) are more difficult to remember than dissimilar items (i.e., "shen, floy, stap"), Kirschen and colleagues applied low-frequency TMS, guided by functional magnetic resonance imaging (fMRI), to the left inferior parietal (LIP) lobule.…”