Purpose

This study was conducted to determine hippocampal outputs by using a gene gun to apply multiple dyes in order to explore interneuronal connections at the systematic level.

Tracing Hippocampal Memory Formation in the European Starling Daniel Katz

Devoogd Lab, Department of Neurobiology/Psychology, Cornell University

AcknowledgementsThe author acknowledges Cornell University and the Rawlings Cornell Presidential Scholarship (RCPRS) program for funding this research. This work was possible thanks to Timothy Devoogd and L. Matthew Law for their continued guidance and assistance throughout this project.

• Identifying hippocampal outputs can yield functional homologs to cortex, as well as the limbic system and other networks with hippocampal involvement.

• Because the labeling is rapid (within several minutes), this can also be used to preselect targets for physiological recording in vivo, or for targeted treatments.

Why the European Starling?

Picture by Sam Crowe, Cornell Lab of Ornithology

What do we mean by memory?

Introduction

Methods – Gene Gun

• Colored dyes are attached to tungsten particles, and then shot into the desired region by a “gene gun”.

• The application of the dye can be controlled by using various filters, which also protect the cell from being damaged during bombardment of the particles.

• Episodic memory is the autobiographical context of a memory – essentially the “when” and “where” (such as remembering the specific time and place that you ate breakfast).

• In humans, episodic memories are formed in the hippocampus, part of the medial temporal lobe of the brain. Once formed, memories are then ‘shipped out’ and stored somewhere in the cortex.

• The starling shows remarkable episodic memory in food storage – it remembers not only what type of food it stores in which location, but also when it stored it (for hundreds of locations!)

• Starlings have a functional hippocampus, but like all birds do not have cortex.

• Using the three lipophilic dyes in multiple combinations, up to seven individual neuronal circuits can be labeled (this number increases as more dyes are introduced).

• Data for the avian hippocampus is still being gathered to determine a neuronal network for memory formation.

Potential Results

Discussion

Hippocampus

Diagram drawn by Timothy Devoogd.

Bio-Rad's portable Helios Gene Gun

This image shows an example of the individual types of neurons targeted by the specific dye combinations (left), and a region where multiple cells of different types are present and visually distinguishable (right).

Image taken from Gan et al., 2000, published in Neuron.

• Lipophilic dyes such as DiO, Dil, and DiD (DiOlistic labeling) allow labeling of individual neurons, making it a useful tool for studying interneuronal interactions.

• By combining multiple dyes, a network of neurons can be labeled in many different colors, with similar neurons labeled the same color.

Introduction

Methods – Gene Gun

Methods – Neuronal Labeling

Temporallobe

Hippocampus

Structure of Lipophilic carbo-cyanine dyes Dil and DiO.

Diagram showing the mechanism of the gene gun delivery system. Particles are propelled towards the cell by helium pulses, which then disperse as the particles penetrate the cell. The low pressure needed to propel the particles and the filter prevent damage to the cell. Picture taken from O’brien & Lumis, Trends in Biotechnology.

Picture by Sam Crowe, Cornell Lab of Ornithology

Diagram drawn by Timothy Devoogd