Have I been here before?
When we enter a new place a set of neurons called ‘place cells’ fire to provide a kind of blueprint for where we are. The next time we see that place those same neurons fire, thus we know when we’ve been somewhere before and don’t have to relearn our way around familiar territory. But similar places may activate overlapping neuronal blueprints, leaving room for confusion if the neurons are not fine-tuned. Dr Matt Jones in the Department of Physiology, working with a distinguished team at the Massachusetts Institute of Technology that included the Nobel Laureate, Professor Susumu Tonegawa, has identified a neuronal mechanism that our brains may use to rapidly distinguish similar, yet distinct, places.
Forming such memories of places and contexts engages a part of the brain called the hippocampus. The team has been exploring how each of the three hippocampal subregions – the dentate gyrus, CA1 and CA3 – uniquely contribute to different aspects of learning and memory. In the current study it was revealed that the learning in the dentate gyrus is crucial to rapidly recognising and amplifying the small differences that make each place unique.
The team’s findings, published in Science (6 July 2007), demonstrate that a particular protein signalling molecule (the NMDA receptor) found in a specific network of brain neurons (the dentate granule cells of the hippocampus) is essential for these rapid discrimination processes. The work could lead to treatments for memory-related disorders, as well as helping with the confusion and disorientation that plague elderly individuals who can have trouble distinguishing between separate but similar places and experiences.
www.bristol.ac.uk/Depts/Physiology
This research was supported by the National Institute for Mental Health and the National Institutes of Health.
SUMO wrestling in the brain
The brain contains about 100 million nerve cells, each having 10,000 connections to other nerve cells. These connections, called synapses, chemically transmit the information that controls all brain function via proteins called receptors. A major feature of a healthy brain is that the synapses can modify how efficiently they work, by increasing or decreasing the amount of information transmitted. In disorders such as epilepsy, for example, the synapses transmit too much information, resulting in over-excitation in the cells.
A research team, led by Professor Jeremy Henley in the Department of Anatomy, showed that increasing the amount of SUMO, a small protein found in the brain, could be a way of treating diseases such as epilepsy by preventing this over-excitation. When one type of receptor – the kainate receptor – receives a chemical signal, the SUMO protein becomes attached to it. SUMO pulls the kainate receptor out of the synapse, preventing it from receiving information from other cells, thus making the cell less excitable.
The discovery that SUMO proteins can regulate the way brain cells communicate may provide insight into the causes of, and treatments for, brain diseases that are characterised by too much synaptic activity. This discovery also provides new potential targets for drug development that could one day be used to treat a range of such disorders. The findings were published in Nature (17 May 2007).
This research was funded by the Medical Research Council, the Wellcome Trust and the European Union.