A novel developmental rodent model to investigate the neural basis of episodic memory

Abstract

Episodic memory is the recollection of unique autobiographical events, including rich detail of times, places and associated contextual information. In neurodegenerative diseases, such as Alzheimer’s disease, episodic memory is greatly impaired. The ability to recall episodic memories is thought to develop later in childhood than other types of memory such as novelty recognition, however this ontogeny in animals is so far unconfirmed due to a lack of suitable behavioral tests. The aim of this thesis was to develop a protocol suitable for testing the development of memory in juvenile rats, and to understand if rats show a similar ontogenic profile of memory as humans.
A novel protocol was developed and first tested in adult rats. The protocol was compressed into two days of testing using a battery of spontaneous object recognition tasks to allow testing of narrow critical developmental time windows. The tasks were then used to assess the ontogeny of different types of memory in rats from p25 to adulthood. The Object Place Context (OPC) task was used as a model of episodic memory and used alongside the Novel Object Recognition (NOR), Object Context (OC) and Object Place (OP) tasks, all of which were tested in two days.
It was discovered that all ages tested could perform basic object recognition (NOR task). Associative contextual memory (OC task) developed between p38 and 42 and both spatial (OP task) and episodic memory (OPC task) developed between p46 and 48. Further investigations pinpointed this spatial and episodic memory development to overnight between p47 and p48. Immunohistochemistry allowed the investigation of the anatomical locus of the episodic memory task, and showed subtle increases in the CA3 in p48 rats. It was concluded that rats do show a similar ontogenic profile of memory as humans, with recognition memory developing before episodic memory. This information will be invaluable when studying disease during development, and may also be extrapolated to understand disease of old age.

Date of Award	2015
Original language	English
Awarding Institution	University of Dundee
Supervisor	Ros Langston (Supervisor)