Human Medial Temporal Lobe Neuron Responses to Direct Amygdala Stimulation Öffentlichkeit

Abstract

Forgetting memories is a common part of day to day life. In fact, the majority of memories we develop are forgotten within just a week as shown by Ebbinghaus in 1885. However, which memories are forgotten versus prioritized for long-term storage is not as obvious. Years of research have shown that emotionally arousing events are often remembered better compared to neutral events. The amygdala is one of the key structures involved in this prioritization of hippocampal-dependent declarative memory. Specifically, the basolateral amygdala (BLA) appears to be key in the enhancement of emotional memories. Moreover, recent studies in rodents and in humans have demonstrated that direct electrical stimulation of the amygdala can enhance recognition memory for neutral objects one day later without inducing subjective emotional arousal. Using a valuable data set from epilepsy patients who have depth electrodes implanted for clinical purposes, we conducted a novel analysis on medial temporal lobe single- neuron responses to amygdala stimulation. For most stimulation parameters, no significant changes to medial temporal lobe neuron firing rate occurred which parallels previous rodent experiments conducted by Bass and Manns (2015). However, an extended duration stimulation of three seconds did appear to result in an increase in firing rate at most levels of analysis. These significant differences did appear to be trivial modulations and likely non-meaningful. This study did not analyze synchronization of single neuron firing rate to low gamma oscillations as previously seen in rodent studies which will a future analysis to be conducted in human subjects.

Table of Contents

Table of Contents

INTRODUCTION AND BACKGROUND............................................................................................1

Introduction....................................................................................................................................1 

The Medial Temporal Lobe and Declarative Memory......................................................................2 

Emotional Memory and the Amygdala............................................................................................2

Memory Enhancement through Direct Stimulation of the Basolateral Amygdala..........................3 

Physiological Effects of BLA Electrical Stimulation........................................................................3 

Study Goals and Hypotheses...........................................................................................................4

METHODS.......................................................................................................................................6

Experimental Paradigm...................................................................................................................6

Pre-Processing of the Data..............................................................................................................9 

Spike Sorting.................................................................................................................................10

Single Unit Classification Procedure.............................................................................................11 

Example Single Unit isolated through Combinato........................................................................12

Analysis and Statistics..................................................................................................................13

RESULTS.......................................................................................................................................18

Example of a single unit responding to image presentation........................................................18

Example of a single unit responding to direct amygdala stimulation..........................................19

Raw Firing Rates Analysis During and Post-Stimulation.............................................................20

Change in Firing Rates Analysis During and Post-Stimulation....................................................22

Percent Change in Firing Rates Analysis During and Post-Stimulation.......................................24

Change in Firing Rates Across Stimulation Timeline...................................................................26

DISCUSSION.................................................................................................................................29

CONCLUSION AND FUTURE DIRECTIONS..................................................................................32 REFERENCES................................................................................................................................33 APPENDIX....................................................................................................................................38

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience Health Sciences, Surgery
Stichwort	Emotional Memory Amygdala Medial Temporal Lobe Human Single Neurons Declarative Memory
Committee Chair / Thesis Advisor	Willie, Jon, Emory University
Committee Members	Manns, Joseph, Emory University Scott, Tracy, Emory University

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