Distributed interactions across multiple brain circuits explain performance in a cued spatiovisual discrimination task

Thesis

Neurons transiently synchronise their spiking activity to form cell assemblies that can represent information about external sensory inputs and internal cognitive mechanisms in selective brain circuits. However, it remains poorly understood whether, and how, within-circuit spiking can be organised to form brain-wide assemblies at the service of optimal behaviour. The answer to this question, grounded in that everyday life experience is typically composed of a variety of stimuli and sensory modalities, remains elusive because population spike codes have not been investigated across multiple simultaneously recorded brain circuits.

Here we show that in a baseline period neurons in the dorsal hippocampal CA1 (CA1), the amygdala (Amy), the prefrontal cortex (PfC), the ventral tegmental area (VTA) and the nucleus accumbens (NAc) of mice can organise their activity over few tens of milliseconds to form constitutively expressed patterns of short timescale neuronal co-firing in the mouse brain. We found that in a cued discrimination task, where mice used LED-based visual cues to determine their behaviour in response to an auditory stimulus, these same brain-wide assemblies evolve with the successful translation of local sensory representations into behaviour. Moreover, their activity was predicted by a stereotyped, transient oscillatory state which appeared to facilitate the tight coordination of firing patterns between neurons in distal structures.

These insights were facilitated by state-of-the-art algorithms for spike-sorting and multivariate LFP segmentation which we were able to leverage using current best practices in software architecture. Our results thus support the notion of cell assemblies existing at the macro, inter-regional level of brain organisation and show how this may be critical for integrating disparate sources of information.

Authors: Morley, A

• DOI: 10.5287/ora-o87zmr0wy
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English