Neural correlates of auditory working memory precision: an intracranial EEG study
Poster No:
1127
Submission Type:
Abstract Submission
Authors:
Joel Berger1, Alexander Billig2, Phillip Gander3, Meher Lad4, Sukhbinder Kumar5, Kirill Nourski1, Christopher Kovach6, Ariane Rhone1, Christopher Garcia5, Hiroto Kawasaki1, Brian Dlouhy5, Matthew Howard1, Timothy Griffiths4
Institutions:
1The University of Iowa, Iowa City, IA, 2University College London, London, United Kingdom, 3University of Iowa, Iowa City, IA, 4Biosciences Institute, Newcastle, United Kingdom, 5University of Iowa, IOWA CITY, IA, 6University of Nebraska, Omaha, NE
First Author:
Co-Author(s):
Introduction:
Working memory is the capacity to hold and manipulate behaviorally relevant information in mind in the absence of ongoing sensory input. Utilizing intracranial EEG in a recent paper (Kumar et al., 2021), we demonstrated oscillatory correlates of auditory working memory (AWM) during maintenance of a tone in various structures, including the hippocampus. Here, we extend this work further by developing a paradigm that accounts for a precision model of working memory, allowing for measurement of error on a single trial basis and enabling a clear distinction of the retrieval period from the maintenance period, whilst simultaneously recording single units and local field potentials (LFPs).
Methods:
We simultaneously recorded behavioral responses to the task and LFPs from the hippocampi of five human subjects undergoing invasive monitoring for presurgical localization of epileptic foci [wherein the hippocampus was subsequently found to be not a seizure focus]; in three patients, single units were also recorded in the hippocampus and Heschl's gyrus. For the AWM task (Figure 1), participants were presented with a short tone, followed by a 3-second retention period. They were instructed that they then had 5 seconds to alter a repeated tone to match it as close in frequency as they could to the target tone ("tuning/retrieval" period), for a total of 60 trials. We carried out time-frequency analysis using wavelet transforms for the LFP data, whilst single units were isolated with an automated spike sorting procedure and examined with trial raster plots and peri-stimulus time histograms. Behaviorally, working memory precision was calculated as the reciprocal of the standard deviation of response error.
·Figure 1. Task structure for the AWM paradigm.
Results:
Patients performed the task similarly to previously observed non-epileptic populations. Across all hippocampal contacts, we observed low frequency activity (< 8 Hz) that was persistent throughout the retention period and was particularly striking at the onset of the tuning period, as well as following the offset of this period, concurrent with high gamma suppression (70-150 Hz). Trials were concluded with a significant desynchronization of theta-alpha (4-15 Hz) hippocampal activity (for all time-frequency data, see Figure 2). In two patients with simultaneous HG and hippocampus contacts, we additionally observed an increase in phase locking between the two regions at the onset of the retention period and the offset of the retrieval period. Clear single unit modulation was evident at various phases of the task in HG and hippocampus. In hippocampus, this modulation most commonly manifested as suppression.
·Figure 2. Time-frequency data averaged across all hippocampal contacts (n = 24).
Conclusions:
Overall, these data highlight neural correlates of precision of AWM and implicate the hippocampus in maintenance, retrieval and response monitoring of non-verbal AWM. The combined LFP and single unit data enable development of a model of AWM involving the hippocampus communicating to auditory cortex at various key phases.
Higher Cognitive Functions:
Executive Function, Cognitive Control and Decision Making 2
Learning and Memory:
Working Memory 1
Perception, Attention and Motor Behavior:
Perception: Auditory/ Vestibular
Keywords:
Cognition
ELECTROCORTICOGRAPHY
ELECTROPHYSIOLOGY
Memory
Neuron
Perception
1|2Indicates the priority used for review