Phonological Working Memory Representations in the Left Inferior Parietal Lobe in the Face of Distraction and Neural Stimulation

Abstract

The neural basis of phonological working memory (WM) was investigated through an examination of the effects of irrelevant speech distractors and disruptive neural stimulation from transcranial magnetic stimulation (TMS). Embedded processes models argue that the same regions involved in speech perception are used to support phonological WM whereas buffer models assume that a region separate from speech perception regions is used to support WM. Thus, according to the embedded processes approach but not the buffer approach, irrelevant speech and TMS to the speech perception region should disrupt the decoding of phonological WM representations. According to the buffer account, decoding of WM items should be possible in the buffer region despite distraction and should be disrupted with TMS to this region. Experiment 1 used fMRI and representational similarity analyses (RSA) with a delayed recognition memory paradigm using nonword stimuli. Results showed that decoding of memory items in the speech perception regions (superior temporal gyrus, STG) was possible in the absence of distractors. However, the decoding evidence in the left STG was susceptible to interference from distractors presented during the delay period whereas decoding in the proposed buffer region (supramarginal gyrus, SMG) persisted. Experiment 2 examined the causal roles of the speech processing region and the buffer region in phonological WM performance using TMS. TMS to the SMG during the early delay period caused a disruption in recognition performance for the memory nonwords, whereas stimulations at the STG and an occipital control region did not affect WM performance. Taken together, results from the two experiments are consistent with predictions of a buffer model of phonological WM, pointing to a critical role of the left SMG in maintaining phonological representations.

Is working memory domain-general or domain-specific? Implications for theory and practice

“…3d), whereas in the SMG, the opposite was the case (Fig. 3e; see also [74,76] for similar evidence using multi-voxel pattern analysis (MVPA) and transcranial magnetic stimulation (TMS)). On the other hand, semantic representations could not be decoded in either STG or SMG during either encoding or maintenance, showing the specificity of these regions for phonological WM.…”

“…Although parietal regions have been implicated in both visual and verbal WM, different parts of the parietal lobe have been identified in these two domains. Specifically, the bulk of evidence in visual WM points to posterior parietal and intraparietal sulcus (IPS), whereas verbal WM studies often implicate the supramarginal gyrus (SMG) [67][68][69][70][71][72][73][74][75][76]. Even within the domain of language processing, researchers have identified separable neural correlates for semantic and phonological WM [77].…”

Precision of phonological errors in aphasia supports resource models of phonological working memory in language production

“…Critically, decoding was still possible in SMG. In a second experiment, the authors showed that transcranial magnetic stimulation to SMG, but not STG, disrupted phonological working memory (Yue & Martin, 2022). These results provide support for the buffer account.…”

Increased brain activation and functional connectivity after working memory training in patients with ischemic stroke: an fMRI study

“…The MFG has been recognized to be crucial for maintaining information and supporting executive function during WM, especially high-load WM tasks (Volle et al, 2008;Bokde et al, 2010). The IPL was believed to play a critical role in maintaining phonological representations during phonological WM (Yue and Martin, 2022). It has been demonstrated that the cerebellum was included in the WM network and played a relevant role in subvocal rehearsal (Pleger and Timmann, 2018).…”