Poster A76, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
The Role of the Posterior Parietal Cortex in Episodic Retrieval
Marty Fiati1, Peter Bright1; 1Anglia Ruskin University
Increasingly findings from the memory literature have implicated the posterior parietal cortex (PPC) in the memory operations which occur at the time of episodic retrieval. Involvement of the PPC has been found to support binding of the fine multisensory features in an episode. In the current study, participants performed a multisensory episodic retrieval task in which they first identified previously studied faces, and subsequently made based source judgements denoting the spatial location (left/right), voice (male/female), and study task (pleasantness rating/celebrity judgement) that they had associated with each face at study. Recorded ERPs associated accuracy of source recollection with a late positivity over the PPC. In order to evaluate the causal role of this activity with retrieval, transcranial direct current stimulation (tDCS) was employed at the site of maximal activity in the left PPC (P3) before performing the task. The performance of 30 participants following excitatory anodal tDCS, or inhibitory cathodal tDCS, was compared to sham tDCS. Excitatory stimulation was not found to lead to greater retrieval of multimodal contexts than sham stimulation overall. Inhibitory stimulation however was found to decrease retrieval of multimodal episodic contexts compared to sham stimulation. The specificity of these changes to PPC stimulation was further verified in a sample of participants who underwent the same tDCS protocol to the left motor area (M1), but did not exhibit this change in task performance. The findings indicate that the binding of different sensory features of an episode at retrieval is decreased by reductions in activation of the PPC.
Topic Area: LONG-TERM MEMORY: Episodic