The Neural Code

This article is taken from the Winter 2011 issue of I, Science.

Jo Poole talks brain cells, ‘roborats’, and how cutting-edge neurology may help us overcome Parkinson’s

Charles Scott Sherrington described the brain as “Biology’s final frontier”. The greatest differences between us and our closest relatives lie in the convoluted folds of a jelly-like organ that constitutes 2% of our body weight and requires 20% of our nutrition. Neuroscience has experienced a renaissance in the last few decades, bringing neurology to the forefront of science.

John Chapin ranks the neural code as one of science’s greatest mysteries, alongside the origin of the universe and life itself. We have nearly 100 billion brain cells, each connected to as many as 100,000 others; equivalent to the number of stars in the Milky Way. These cellular networks are continuously remodelling, even in adulthood. Thus any code is unique to a particular brain. There is, however, enough consistency to produce theories about higher thinking.

Mind Control
Last year The Economist said science was on the verge of “overturning the essential essence of humanity”, envisaging a cyberpunk dystopia where governments control our movements, thoughts, fears and emotions. Several years ago, there was a media storm about ‘roborats’; researchers could steer rats through a maze using remote controlled electrode implants. In the 1960s Delgado, a Yale neuroscientist, astonished and appalled onlookers as a finger on the button of a remote electrode caused a charging bull to stop and wander away.

Fortunately, these crude stimulations merely tap into primeval neural circuits; those for physical and instinctive habits like eating, drinking and feeling scared. When it comes to mimicking or manipulating higher thought we are still complete novices. But films like Inception have set us wondering if this science fiction will be realised in our lifetime.

Memory
The way memory works is one of our greatest fascinations. Its toolbox includes a small, coiled structure lying behind our temporal lobes; the hippocampus. Genetic ablation, or gene silencing, of this area, leads to devastating short-term memory loss and the inability to form new memories. Yet its destruction cannot displace long-term memories, fear memories generated in the amygdala or muscle memory in the motor cortices and cerebellum.

Recent studies show that the brain cells activated during memory formation are the same as those used during recall; we literally relive an experience. Interrupting this pathway prevents the memory being evoked. This does not work in reverse; we cannot imprint artificial memories. Accessing the right cells, with the right chemicals and acting on the nanosecond timescale required is far beyond our current capabilities.

However neuroscience has brought us considerable medical advancement. Already telepathic prosthetic devices are available for amputees. We will be able to slow, if not reverse, diseases of brain degeneration. Small-scale brain tissue transplants are underway, using foetal tissue, poststroke or for Parkinson’s disease. We know the genes responsible for diseases like fragile X syndrome, an X-linked disorder affecting the production of neurotransmitters, which causes severe mental retardation; treatments are now available as a direct result of research.

The brain may well be biology’s final frontier, but the last two decades shows rapid progress and, as The Art of War declares, all obstacles can be overcome with strategy.

Image: flickr | Fabrice de Nola

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