Brain scans under pressure

A fledgling project involving chemists and neuroscientists aims to uncover how the high pressures experienced by deep-sea divers affect the brain.

Paul McMillan at University College London, UK, is working with Susan Greenfield, professor of physiology at Oxford University. McMillan will use Greenfield’s brain-studying techniques, where voltage is passed through slices of brain to stimulate a neural response. McMillan has built a high-pressure cell to use see what happens to the brain responses under pressure.

The path of the electric signal is tracked with fluorescent dyes, which change colour as voltage goes through the brain. A microscope with fluorescence imaging tracks the voltage as it passes through neurons. The technique is standard, but has not been used at high pressure before, said McMillan. ’It’s the first time we can get direct visualisation of how high pressure affects physiological processes,’ he told Chemistry World.

Deep-sea divers can experience pressures up to 200 atmospheres. Physiological effects that McMillan has been studying include nitrogen narcosis; the sense of euphoria and loss of logical thought often experienced by divers; and the observation that the effects of anaesthesia can be reversed at high pressure.

The first images from the project have just been developed by post-doctoral researcher Agnieszka Wlodarcyck. ’We think we are seeing an increase in brain activity as we put on the first few atmospheres of pressure,’ McMillan said. 

Wlodarcyck’s first images also suggest that the excitation pathway gets longer and spreads out further as pressure increases. 

McMillan concedes that this work is at an ’incredibly early’ stage, but wants to plug what he sees as a gap between molecular-level knowledge of brain activity and larger scale observations - behaviour.

An MRI expert contacted by Chemistry World suggested that McMillan should start with very simple tightly controlled experiments, and perhaps could use MRI techniques in future. Whatever McMillan finds will be new, he said: ’It’s a project forged at the interface of two completely different research areas.’ 

Katharine Sanderson