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Title: A functional role for hippocampal non-local activity and a method to interfere with functional circuits
Author: Olafsdottir, H. F.
ISNI:       0000 0004 5358 3633
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2014
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The hippocampus has been implicated in spatial cognition. Pyramidal cells in the rodent hippocampus show a spatial correlate in their activity, such that they increase their activity when an animal enters their principal firing field (‘place field’). However, behavioural state and task demands have been found to influence place cell activity when cells are outside their place field. This thesis will report findings implying a functional role for ‘out-of-field’ activity. The first experimental chapter will show ensemble place cell activity is highest at the start of a goal-directed trajectory, and that such enhanced activity is related to navigational performance. These findings accord with hippocampal activity patterns observed in human studies. Moreover, we speculate the enhanced activity may relate to navigational planning. The second experimental chapter shows hippocampal place cell sequences during rest preplay a future, motivationally-relevant trajectory through unexplored space. This effect could not be explained by simple preconfiguration in the hippocampal circuitry. Thus, we conclude these findings show that preplay can be under the control of goal-directed influences and may represent the neural signature underlying navigational planning in novel environments. The aforementioned findings emphasise the importance of studying functional neural circuits. Consequently, the final study describes a method to perform targeted ablations of single-cells in the rodent brain, by means of laser irradiation. We show this lesioning method is spatially precise and has a depth limitation of ~400μm below brain surface. Moreover, we describe one experimental application of the method. We suggest this method is well suited for addressing the causal links between functional neural circuits and behaviour. The final chapter discusses the data in terms of how out-of-field hippocampal activity may be involved in future planning and the contribution the ablation method can make to the study of hippocampal function.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available