Gamma-band Synchronization in the Macaque Hippocampus and Memory Formation

• Authors: Michael J. Jutras, Emory University; Pascal Fries, Radboud University Nijmegen; Elizabeth Buffalo, Emory University
• Journal Title: Journal of Neuroscience Nursing
• Volume: Volume 29, Number 40
• Publisher: Lippincott, Williams & Wilkins | 2009-10-07, Pages 12521-12531
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1523/JNEUROSCI.0640-09.2009
• Subjects: Biology, Neuroscience; Health Sciences, General
• Keywords: hippocampus; memory; gamma; oscillation; synchronization; coherence

Abstract

Increasing evidence suggests that neuronal synchronization in the gamma band (30–100 Hz) may play an important role in mediating cognitive processes. Gamma-band synchronization provides for the optimal temporal relationship between two signals to produce the long-term synaptic changes that have been theorized to underlie memory formation. While neuronal populations in the hippocampus oscillate in the gamma range, the role of these oscillations in memory formation is still unclear. In order to address this issue, we recorded neuronal activity in the hippocampus while macaque monkeys performed a visual recognition memory task. During the encoding phase of this task, hippocampal neurons displayed gamma-band synchronization. Additionally, enhanced gamma-band synchronization during encoding predicted greater subsequent recognition memory performance. These changes in synchronization reflect enhanced coordination among hippocampal neurons and may facilitate synaptic changes necessary for successful memory encoding.