Research Associate
Department of Cell & Developmental Biology & Institute of Behavioural Neuroscience
| Research | Publications | CV | Contact |
My research focuses on the role of neuronal oscillations and oscillatory coding in memory and spatial cognition. I am also interested in using human neuroimaging techniques (EEG, MEG, fMRI) to investigate how the structure and dynamics of whole-brain networks support rapid and flexible task-dependent cognition. Following my PhD thesis submission in Sep 2011, I am continuing post-doctoral research for 6 months (Jan-Jun 2012) in the Space & Memory Group with Prof. John O'Keefe. If you would like to get in touch with me about job opportunities then please email:
Doctoral Research My doctoral research tested specific predictions of the oscillatory interference model, which models how the location-specific activity of place cells and grid cells arises from an interference of theta-band oscillations (Burgess, 2008).
The effects of cannabinoids and novelty on hippocampal electrophysiology Download my thesis:
Abstract: Exposure to novel environments alters hippocampal cell and theta local field potential activity to support the formation of new or updated spatial representations. It induces remapping of place cell fields, a reduction in CA1 theta frequency and an increase in the spatial scale of entorhinal grid cell fields. A recent model proposes that a reduction in the slope of the theta frequency-running speed relationship (TFRSR) can account for these effects (Burgess, 2008, Hippocampus). In contrast, the model proposes that the Y-axis intercept of the TFRSR is unaffected by novelty but instead correlates with anxiety/arousal. Thus, the theta frequency reduction elicited by a wide range of anxiolytic drugs (Gray & McNaughton, 2000) is suggested to result from a decrease in the intercept. Cannabinoids are anxiolytic at low doses, reduce theta frequency and disrupt the theta-timescale dynamics of place cell firing. In contrast, environmental novelty elicits a coordinated shift in CA1 place cell firing to a later theta-phase. This thesis examines the electrophysiological effects of environmental familiarity or novelty in combination with a low, intraperitoneal dose of the cannabinoid agonist O-2545, or its vehicle, saline. It was found that exposure to novel environments reduced the slope of the TFRSR whereas the cannabinoid reduced the intercept, in agreement with the model. These effects were not due to decreased body temperature or changes in behaviour. Combining novelty and drug reduced both slope and intercept. Furthermore, the extent of novelty-induced place cell remapping correlated with the reduction in slope. The mean theta-phase of place cell firing shifted later in novelty, but this was disrupted by the cannabinoid. In contrast, the mean theta-phase of the interneuron population was stable across conditions, but novelty increased the dispersion of interneuron theta-phase preferences. These results help to elucidate the mechanisms underlying novelty processing and cannabinoid action in the hippocampus.
See the thesis on UCL Discovery.
Theta local field potential (LFP) and place cell recording These figures illustrate some of the typical electrophysiological signals that can be recorded from the hippocampus:
The theta oscillation: These data were recorded during 4 10-minute trials (each trial colour-coded from blue through to red). The power spectrum (left) shows a prominent peak at the theta frequency (~8 Hz). The oscillatory theta wave can easily be seen on raw plots of the local field potential (LFP) from each of the 4 trials.
(A) The rate map shows that the cell is only active in one location in the environment (this plot shows an overhead view of the environment, a square box, with high firing rates in warm colours and low firing rates in cooler colours). (B) The second figure shows the waveform of the cell, which is distinctively broad for a pyramidal cell. (C, D) The next two figures show the autocorrelogram for 20ms (C) and 500ms (D) time periods. On the 20ms plot, a brief refractory period of silence is observed (indicated by a blank space in the middle of the histogram). This is flanked by large peaks due to the complex spiking of the place cell, whereby the cell fires bursts of action potentials at repeatable time intervals. The 500ms autocorrelogram shows a large central peak corresponding to this complex spiking, and a regular series of smaller peaks that indicate that the cell activity is strongly modulated by the theta oscillation. (E) Finally, the right-most figure shows the phase of cell firing relative to the theta oscillation - this once again illustrates the strong influence of the theta oscillation on the firing of this place cell. All of the spikes recorded from this cell are confined to a narrow range of theta phases.
Embodied Cognition I am also enthusiastic about the embodied cognition approach, which emphasises the importance of the environment in the ongoing action-perception cycle. I have been particularly inspired by the work of the late Francisco Varela, who made valuable contributions to our understanding of the processes of life and cognition. Of particular significance were his work on the theory of autopoiesis, which provides a framework for understanding how the autonomy of an organism emerges on the basis of the network of interactions within the organism and between the organism and its environment. Additionally, towards the end of his life, he championed the enactive approach to cognitive neuroscience, appreciating the importance of action and embodiment to cognition.
For more information about research into space, memory and navigation, you might like to visit the websites of the Institute of Behavioural Neuroscience, the Spiers Lab or the O'Keefe and Burgess Groups at UCL. Some additional information can be found on my academia.edu page. If you would like to get in contact with me, then please send an email to:
You can download my curriculum vitae here.
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