Contribution of left supramarginal and angular gyri to episodic memory encoding: An intracranial EEG study

• Published in: NeuroImage (Orlando, Fla.) Vol. 225; p. 117514
• Main Authors: Rubinstein, Daniel Y., Camarillo-Rodriguez, Liliana, Serruya, Mijail D., Herweg, Nora A., Waldman, Zachary J., Wanda, Paul A., Sharan, Ashwini D., Weiss, Shennan A., Sperling, Michael R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.01.2021; Elsevier Limited; Elsevier
• Subjects: Attention - physiology; Convulsions & seizures; Cortex (parietal); Drug Resistant Epilepsy; EEG; Electrocorticography; Electrodes; Electrodes, Implanted; Electroencephalography; Epilepsy; Episodic memory; Humans; iEEG; Memory; Memory - physiology; Memory, Episodic; Mental Recall - physiology; Parietal Lobe - physiology; Patients; Spectral tilt; Subsequent memory effect; Ventral parietal cortex; HFA; VAN; DMN; LFA; Spectral tilt; VPC; SME; SmG; iEEG; Subsequent memory effect; AnG; Ventral parietal cortex; Episodic memory
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2020.117514

The role of the left ventral lateral parietal cortex (VPC) in episodic memory is hypothesized to include bottom-up attentional orienting to recalled items, according to the dual-attention model (Cabeza et al., 2008). However, its role in memory encoding could be further clarified, with studies showing both positive and negative subsequent memory effects (SMEs). Furthermore, few studies have compared the relative contributions of sub-regions in this functionally heterogeneous area, specifically the anterior VPC (supramarginal gyrus/BA40) and the posterior VPC (angular gyrus/BA39), on a within-subject basis. To elucidate the role of the VPC in episodic encoding, we compared SMEs in the intracranial EEG across multiple frequency bands in the supramarginal gyrus (SmG) and angular gyrus (AnG), as twenty-four epilepsy patients with indwelling electrodes performed a free recall task. We found a significant SME of decreased theta power and increased high gamma power in the VPC overall, and specifically in the SmG. Furthermore, SmG exhibited significantly greater spectral tilt SME from 0.5 to 1.6 s post-stimulus, in which power spectra slope differences between recalled and unrecalled words were greater than in the AnG (p = 0.04). These results affirm the contribution of VPC to episodic memory encoding, and suggest an anterior-posterior dissociation within VPC with respect to its electrophysiological underpinnings. [Display omitted]