One of the great challenges of Systems Neuroscience is to understand how different types of neurones can become active together to encode important information in the brain. This is a question of the brain’s “chronocircuitry” – it concerns the timing of neurone activity in relation the behaviour of the animal, and the physical connectivity of neurones (their inputs and outputs) within the brain. What does the study of chronocircuitry look like in action?

My doctoral work focused on one key aspect of chronocircuitry research: in the rodent brain, different types of neurone have been characterised based on their anatomy, connectivity and patterns of activity (for example in relation to different frequency brain rhythms). Historically speaking, however, this work had been carried out through studying single neurones in the brain of an anaesthetised animal, and anaesthesia is known to alter brain activity compared to the non-anesthetized waking state. At this time, only information on location and activity – but not anatomy or connectivity – could be gathered from the same neurone in an awake animal. This meant that relating putative neurone types (classified exclusively on their activity) to animal behaviour was essentially impossible. My work asked how the activity of different neurones might be characterised in waking, sleeping, and anesthetised conditions, and the identity of single cells tracked between those different states. This work led to a better understanding of anaesthesia’s effects on brain activity, and the unique sensitivities of different neurone types to anaesthesia.

Publications

Huxter JR, Senior TJ, Allen K, Csicsvari J (2008). Theta phase-specific codes for two-dimensional position, trajectory and heading in the hippocampus. Nat Neurosci, 11(5):587-94

Senior TJ, Huxter JR, Allen K, O’Neill J, Csicsvari J (2008). Gamma oscillatory firing reveals distinct populations of pyramidal cells in the CA1 region of the hippocampus. J Neurosci, 28(9):2274-86

O’Neill J, Senior TJ, Allen K, Huxter JR, Csicsvari J (2008). Reactivation of experience-dependent cell assembly patterns in the hippocampus. Nat Neurosci, 11(2):209-15

Csicsvari J, O’Neill J, Allen K, Senior TJ (2007). Place-Selective Firing Contributes to the Reverse Order Reactivation of CA1 Pyramidal Cells during Sharp Waves in Open Field Exploration. Eur J Neurosci, 26:704-16

O’Neill J, Senior TJ & Csicsvari J (2006). Place-selective firing of CA1 pyramidal cells during sharp wave/ripple network patterns in exploratory behaviour. Neuron, 49:143-45