My research focuses on the neural processes that lie behind memory and learning.

I am particularly interested in the neural substrates of recognition memory. Differences in neuronal activity are detected electrophysiologically and by using immunocyotchemical markers such as Fos, a protein that is produced at higher levels in more active regions of the brain. By measuring activity differences after presenting stimuli that vary in familiarity - from a novel stimulus, which has never been previously encountered, to familiar stimuli, experienced many times before - it is possible to observe in which regions of the brain and under what circumstances the level of familiarity correlates with modulation of activity. These researches are conducted in close collaboration with Professor Zafar Bashir and Dr E Clea Warburton, and Professors John Aggleton and John Pearce in the Department of Psychology at the University of Wales, Cardiff.

We have found that the perirhinal cortex is differentially activated depending on stimulus familiarity; with repetition, a stimulus causes long-lasting depression of the neuronal responses. Computational modelling studies, performed in a collaboration with Dr Rafal Bogacz of the Department of Computer Science, have established that encoding familiarity in this manner can provide an efficient way to process and store information.

Our investigations have shown that different, distinct brain areas are involved in recognition memory, depending on the nature of the stimulus. A system centring on perirhinal cortex deals with the discrimination of individual item familiarity, whereas a system involving the hippocampus deals with assocational, spatial and recollective aspects of recognition memory. Thus, for example, viewing novel and familiar arrangements of items produces changes in the activity of the hippocampus.

To understand these processes we employ techniques from a range of neuroscientific disciplines, analysing at molecular, cellular, systems and behavioural levels. Thus we use pharmacological, molecular genetic and selective ablation techniques to test for consistencies and inconsistencies in the changes produced in behaviour, neuronal activity and cellular processes related to recognition memory.

Continued study of the system will allow us to characterise the basis of recognition more fully, enhancing our understanding of normal memory, the neural basis of education, and the deficits of memory in conditions such as Alzheimer's Disease.

Projects currently underway include:

• The neural substrates of familiarity and event memory;
  with ZI Bashir, and JP Aggleton and JM Pearce (Cardiff)
• Intracellular signalling pathways essential to recognition memory;
  with ZI Bashir, EC Warburton and J Uney.
• Temporal lobe neuronal activity and recognition memory mechanisms;
  with RU Muller (SUNY, New York)
• Development of neural network models of familiarity discrimination and recognition memory;
  with R Bogacz.

Selected publications:

MW Brown and JP Aggleton (2001) Recognition Memory: What are the roles of the perirhinal cortex and hippocampus? Nature Reviews Neuroscience 2: 51-61.

R Bogacz and MW Brown (2003) Comparison of computational models of familiarity discrimination in the perirhinal cortex. Hippocampus 13: 494-524.

EC Warburton, T Koder, K Cho, PV Massey, G Duguid, GRI Barker, JP Aggleton, ZI Bashir, MW Brown (2003) Cholinergic neurotransmission is essential for perirhinal cortical plasticity and recognition memory. Neuron 38: 987-996.

EC Warburton, CPJ Glover, PV Massey, H Wan, B Johnson, A Bienemann, U Deuschle, JNC Kew, JP Aggleton, ZI Bashir, J Uney, MW Brown (2005) CREB phosphorylation is necessary for perirhinal LTP and recognition memory. Journal of Neuroscience 25: 6296-6303.

GRI Barker, EC Warburton, T Koder, NP Dolman, JCA More, JP Aggleton, ZI Bashir, YP Auberson, DE Jane and MW Brown (2006) The different effects on recognition memory of perirhinal kainate and NMDA glutamate receptor antagonism: Implications for underlying plasticity mechanisms. Journal of Neuroscience 26: 3561-3566.