• The single switch paradigm produced a

significant dose-dependent impairment in

memory encoding for task rules demonstrated

by decreased overall accuracy in the post-switch

session.

• In awake behaving rats we observed local field

potentials that showed high activity in the theta

band frequency (4-10 Hz).

• The overall power of the theta rhythm was

reduced in a dose-dependent manner.

• In the encoding phase of the task when

waveform averages were gated to the light

onset, we found clear and consistent synchrony

across the EC, DG, and ACC.

• There were significant differences in the pre-

stimulus vs. post-stimulus waveform, potentially

indicating an encoding-stimulus evoked

enhancement of the overall theta rhythm.

• In the retrieval phase of the task when

waveform averages were gated to the onset of

the tone, we found preliminary evidence

indicating that synchronization between the DG

and the ACC increases preferentially during

retrieval events.

EFFECTS OF ACUTE ETHANOL ON

MEMORY ENCODING, RETRIEVAL, AND THE THETA RHYTHMK.S. Edwards, J.N. Gaines, D. Task, B. Givens

Department of Psychology, The Ohio State University, Columbus, OH 43210 469.12/FF2

Overview of Operant Task

Representative Histology Effects of Ethanol on Within-Session AccuracyHypothesized Memory Circuit INTRODUCTION

METHODS

REFERENCES &

ACKNOWLEDGMENTS

SUMMARY

Experimental Timeline

• Subjects: Adult male Long-Evans rats

• Operant Task Rule Contingencies:

• Delayed match to sample (DMTS)

• Delayed non-match to sample (DNMTS)

• Rules were counterbalanced

• Performance Criterion before switch:

• >70% accuracy for 3 sessions

• Single Rule Switch

• Day 1: Pre-Switch = Rule A

• Day 2: Injection 10 min pre-switch=Rule B

• Day 3: Post Switch = Rule B

• Electrode Construction and Implantation

• Recording Wires: stainless steel coated

with Teflon (3 microns diameter)

• Implanted into three sites:

• Anterior Cingulate

• Dentate Gyrus

• Entorhinal Cortex

• Intraperitoneal Ethanol Injections (10 min

pre switch):

• 0.0, 0.25, 0.50, 0.75, or 1.0 g/kg ethanol

(10% w/v)

• Physiology Recording and Analysis

• Spike 2 Software (CED)

• Filtered for theta range (5-12 Hz)

Acute exposure to low doses of ethanol

(EtOH) affects many cognitive functions

including memory (White et al, 2000). The

purpose of this study was to adapt a well-

validated (Dudchenko, 2004) model of

episodic-like memory into a serial rule

switching paradigm to assess the effects of

EtOH on memory encoding and retrieval

for specific task rules while performing

simultaneous in vivo recordings of the

ongoing theta rhythm in the entorhinal

cortex (EC), dentate gyrus of the

hippocampus (DG), and anterior cingulate

cortex (ACC). The theta rhythm in these

regions has been implicated in both the

encoding and the retrieval of memories

(Hasselmo et al, 2002). We hypothesized

that EtOH would disrupt memory encoding

more so than retrieval, measured by

impaired accuracy in the post-switch

session. Furthermore, we hypothesized

that disruption of theta rhythm synchrony

between the anatomical regions would

correlate with this memory impairment.

Dudchenko, P. A. (2004). An overview of the tasks used to test working memory

in rodents. Neuroscience and Biobehavioral Reviews, 24, 699-709.

Hasselmo, M.E., Bodelón, C., Wyble, B.P. (2002). A proposed function for

hippocampal theta rhythm: Separate phases of encoding and retrieval

enhance reveral of prior learning. Neural Computation, 14, 793-817

White, A. M., Matthews, D. B., & Best, P. J. (2000). Ethanol, memory, and

hippocampal function: A review of recent findings. Hippocampus, 10, 88-93.

We would like to acknowledge the assistance of R. Mills, B. Morgan, and J.D.

Tucker.

This research was supported by NIAAA grant

1 R03 AA018214-01A1

Synchronization of mean waveform Averages by dose around light onset (Encoding) and tone onset

(Retrieval) by recording location (Anterior Cingulate, Dentate Gyrus, Entorhinal Cortex)

on area under power spectrum Dose-Dependent effects on area under power spectrum

curve in theta-band frequency

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