Continuous Theta Burst Stimulation of Angular Gyrus Reduces Subjective Recollection

Abstract

The contribution of lateral parietal regions such as the angular gyrus to human episodic memory has been the subject of much debate following widespread observations of left parietal activity in healthy volunteers during functional neuroimaging studies of memory retrieval. Patients with lateral parietal lesions are not amnesic, but recent evidence indicates that their memory abilities may not be entirely preserved. Whereas recollection appears intact when objective measures such as source accuracy are used, patients often exhibit reduced subjective confidence in their accurate recollections. When asked to recall autobiographical memories, they may produce spontaneous narratives that lack richness and specificity, but can remember specific details when prompted. Two distinct theoretical accounts have been proposed to explain these results: that the patients have a deficit in the bottom-up capturing of attention by retrieval output, or that they have an impairment in the subjective experience of recollection. The present study aimed to differentiate between these accounts using continuous theta burst stimulation (cTBS) in healthy participants to disrupt function of specific left parietal subregions, including angular gyrus. Inconsistent with predictions of the attentional theory, angular gyrus cTBS did not result in greater impairment of free recall than cued recall. Supporting predictions of the subjective recollection account, temporary disruption of angular gyrus was associated with highly accurate source recollection accuracy but a selective reduction in participants’ rated source confidence. The findings are consistent with a role for angular gyrus in the integration of memory features into a conscious representation that enables the subjective experience of remembering.

Parietal lesion effects on cued recall following pair associate learnin g

“…Indeed, an rTMS study by Sestieri et al, (2013) is in agreement with the neuropsychological evidence limiting the role of PPC to subjective aspects of recollection. Similarly, Yazar et al (2014), have shown that continuous theta burst stimulation (cTBS) on the angular gyrus was related to reduction in participants' source confidence. However, recognition and cued recall confidence were unimpaired.…”

“…In contrast, the account that views VPC retrieval related activations as reflecting post-retrieval capture of attention by retrieved representations (e.g., Cabeza et al, 2011), and the expectation and salience accounts (Buchsbaum et al, 2011;O'Connor et al, 2010), which do not assign a causal recollective role to VPC, predict in principle that VPC damage would yield no cued recall deficits. Similarly, approaches which view the VPC contribution to retrieval primarily as related to subjective recollective experience (e.g., Ally et al, 2008;Simons et al, 2010;Yazar et al, 2014) would also generally predict that lesions should not impair objective cued recall performance.…”

Source memory performance is modulated by transcranial direct current stimulation over the left posterior parietal cortex

“…Instead, the criteria or the confidence levels associated with the source judgments or the false alarms to semantically related lures were affected by stimulating the LPPC (e.g., Pergolizzi & Chua, 2015;Sestieri et al, 2013;Yazar et al, 2014). The inconsistent findings could result from a number of factors, including the different Sestieri et al (2013) and the fact that the theta burst TMS was delivered prior to the test phase in Yazar et al (2014) all led to difficulties in the comparison with the current findings.…”

“…The inconsistent findings could result from a number of factors, including the different Sestieri et al (2013) and the fact that the theta burst TMS was delivered prior to the test phase in Yazar et al (2014) all led to difficulties in the comparison with the current findings.…”

“…Without the comparisons to stimulation on a control site and sham on the target site, the interpretation of the different recognition performance is equivocal because the effect could be due to stimulating the AG or the SPL or both. Yazar, Bergström, & Simons (2014) delivered continuous theta-bust stimulation (cTBS) to the vertex, the AG, or the intra-parietal sulcus (IPS) of three separate groups of participants after the study phase. The participants then engaged in a series of memory tests, including free recall, cued recall, old/new recognition, and source memory tests with confidence judgments for the study items.…”