Killian, Nathaniel J.
Bioelectrical dynamics of the entorhinal cortex.
Degree: PhD, Biomedical Engineering (Joint GT/Emory Department), 2013, Georgia Tech
The entorhinal cortex (EC) in the medial temporal lobe plays a critical role in memory formation and is implicated in several neurological diseases including temporal lobe epilepsy and Alzheimer’s disease. Despite the known importance of this brain region, little is known about the normal bioelectrical activity patterns of the EC in awake, behaving primates. In order to develop effective therapies for diseases affecting the EC, we must first understand its normal properties. To contribute to our understanding of the EC, I monitored the activity of individual neurons and populations of neurons in the EC of rhesus macaque monkeys during free-viewing of photographs using electrophysiological techniques. The results of these experiments help to explain how primates can form memories of, and navigate through, the visual world.
These experiments revealed neurons in the EC that represent visual space with triangular grid receptive fields and other neurons that prefer to fire near image borders. These properties are similar to those previously described in the rodent EC, but here the neuronal responses relate to viewing of remote space as opposed to representing the physical location of the animal. The representation of visual space may be aided by another EC neuron type that was discovered, free-viewing saccade direction cells, neurons that signaled the direction of upcoming saccades. Such a signal could be used by other cells to prepare to fire according to the future gaze location. Many of these spatially-responsive neurons also represented memory for images, suggesting that they may be useful for associating items with their locations.
I also examined the neuronal circuitry of recognition memory for visual stimuli in the EC, and I found that population synchronization within the gamma-band (30-140 Hz) in superficial layers of the EC was modulated by stimulus novelty, while the strength of memory formation modulated gamma-band synchronization in the deep layers and in layer III. Furthermore, the strength of connectivity in the gamma-band between different layers was correlated with the strength of memory formation, with deep to superficial power transfer being correlated with stronger memory formation and superficial to deep transfer correlated with weaker memory formation. These findings support several previous investigations of hippocampal-entorhinal connectivity in the rodent and advance our understanding of the functional circuitry of the medial temporal lobe memory system.
Finally, I explored the design of a device that could be used to investigate properties of brain tissue in vitro, potentially aiding in the development of treatments for disorders of the EC and other brain structures. We designed, fabricated, and validated a novel device for long-term maintenance of thick brain slices and 3-dimensional dissociated cell cultures on a perforated multi-electrode array. To date, most electrical recordings of thick tissue preparations have been performed by manually inserting electrode arrays. This work demonstrates a…
Advisors/Committee Members: Potter, Steve M. (advisor), Buffalo, Elizabeth A. (advisor), LaPlaca, Michelle C. (committee member), Liu, Robert C. (committee member), Stanley, Garrett B. (committee member).
Subjects/Keywords: Spatial representation; Primate; Medial temporal lob; Entorhinal cortex; Hippocampus; Grid cell; Border cell; Memory; Saccade; Fixation; Visual; Stimulus; Saccade-direction cell; Encoding; Recognition; Macaque; Monkey; MTL; Perfusion; Perforated microelectrode array; Neurons; Brain slice; Three-dimensional culture; MEA
to Zotero / EndNote / Reference
APA (6th Edition):
Killian, N. J. (2013). Bioelectrical dynamics of the entorhinal cortex. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52148
Chicago Manual of Style (16th Edition):
Killian, Nathaniel J. “Bioelectrical dynamics of the entorhinal cortex.” 2013. Doctoral Dissertation, Georgia Tech. Accessed October 28, 2020.
MLA Handbook (7th Edition):
Killian, Nathaniel J. “Bioelectrical dynamics of the entorhinal cortex.” 2013. Web. 28 Oct 2020.
Killian NJ. Bioelectrical dynamics of the entorhinal cortex. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2020 Oct 28].
Available from: http://hdl.handle.net/1853/52148.
Council of Science Editors:
Killian NJ. Bioelectrical dynamics of the entorhinal cortex. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52148