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Title: Context dependent processing in the mouse olfactory bulb
Author: Jordan, R.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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Optimal behavioural strategies necessitate the ability to flexibly respond to sensory stimuli according to behavioural context. Contextual information can be defined as internally generated information that gives behavioural meaning to primary sensory stimuli, for example: hunger state, reward associations and other learned information. The olfactory bulb (OB) is the very first site of odour information processing, yet a large variety of contextual information has been described in its activity. To investigate the mechanistic basis of this, I used whole cell patch recordings from identified mitral and tufted cells in the olfactory bulb of the behaving mouse in vivo to measure how odour responses are shaped across rapid olfactory go/no-go learning episodes. While basic physiological properties do not differ between passively exposed and learning mice, I find that a variety of response changes occur specifically in the learning mouse within the very first sniff cycle. Mice acquire active sniffing behaviours during the odour stimulus across learning, a strategy associated with high motivation and fast reaction times. Responses can be tightly modulated on a trial by trial basis by the active sampling state of the mouse, though some inhibitory response changes occur independent of sniffing behaviour. Response changes due to active sampling appear to enhance both the discriminability and detectability of OB odour representation across the olfactory bulb, and exceed that predicted from feed-forward input alone, suggesting the involvement of top-down mechanisms. Response changes are highly correlated in tufted cells, but not mitral cells, indicating that mitral cell response changes may selectively increase discriminability of odourants. Altogether, active sampling overtly shapes odour responses on rapid timescales, likely enhancing odour representation to facilitate rapid olfactory behaviour. Finally, I explore how perception and coding for odour intensity remain robust despite variance in sniffing, and suggest that the olfactory bulb encodes sniffing parameters to allow sniff-independent perception of stimulus features. This dissertation thus begins to demonstrate the functional impact of active sampling on early sensory processing, and provides new perspectives on olfactory bulb function.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available