This thesis characterises the head direction system in pre-weanling rats around the time of eye-opening. Head direction (HD) cells are neurons in a distributed network of brain areas that fire action potentials as a function of the animal’s directional orientation relative to its environment. Environmental sensory information and self-motion cues are used to update the directional signal, with visual landmarks being particularly salient in controlling the preferred firing directions of HD cells. HD cells have previously been shown to be adult-like as early as postnatal day 16 (P16) in the rat pup (Wills et al 2010, Langston et al 2010), just after its eyelids come unfused and coinciding with the first spontaneous exploration of its environment. To determine if the HD cell circuit can organise before the onset of patterned vision, I recorded from the postsubiculum (PoS) before eye-opening in pre-weanling rats. The earliest instance of HD cells is found at P12, three days before eye opening. This early HD signal carries low directional information content and lacks stability both within and across trials. However, once the eyes of the rats are open, the HD system matures rapidly, with a dramatic increase in the number of directional cells and the quality and reliability of their directional signal. A prominent visual landmark is also able to exert control over HD responses within 24 hr of eye-opening. The data suggest that the directional circuit can be organised in the absence of visual spatial information, while patterned vision is rapidly integrated once it becomes available, for accurate and reliable orientation in space.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:668488 |
| Date | January 2015 |
| Creators | Tan, H. M. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1469477/ |
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