While there has been some work on a light therapy for Bipolar disorder, and specifically limiting exposure to blue light to keep the circadian clock in check; this time the effects of blue and yellow pulses of light , deep inside the brain, as investigated by an MIT team, have resulted in a promising treatment for epilepsy.

Epilepsy, as we all know , is caused by excitation of neurons at a focal point and the subsequent spreading of that activation, so that all or a majority of neurons get excited at the same time. The normal treatment , in case the epileptic fits become life threatening, is neurosurgery, or removing the brain area around the focal point.

This research has focused on the effects of yellow pulses of light, inside the brain , on neurons engineered to express the halorhodopsin gene, a gene that responds to yellow light by opening the chloride ion channels. This results in a hyperpolarisation of the cell and thus ensures that the neuron doesn’t fire easily. I believe they have performed the experiments in laboratory cultures (in vitro) and plan to replicate on transgenic mice containing this gene, so it is a long haul from here to some actual treatment options for epileptics. Still the possible applications are fascinating:

Many epilepsy patients have implanted electrodes that periodically give their brains an electric jolt, acting as a defibrillator to shut down overactive neurons. This new research opens up the possibility of an optical implant that could do the same thing, using light instead of electricity. The Media Lab neuroengineering group plans to start studying such devices in transgenic mice this year.

Thus we have a radically new treatment option for epilepsy. It is also pertinent to note that the same group had earlier identified a mechanism whereby blue pulses of light could lead to excitation of the brain. thus, with appropriate implants in the brain, one can , using light, control the excitation and inhibition of neuronal circuits. What advantages these offer over traditional electrode implants needs to be seen.

The group also plans to use the new method to study neural circuits. Last year, Boyden devised a technique to stimulate neurons by shining blue light on them, so with blue and yellow light the researchers can now exert exquisite control over the stimulation and inhibition of individual neurons.

Lets hope they succeed in their efforts, not only to help epileptics with non-surgical treatments, but also to more deeply ‘see’ the neural circuits and the neural codes.

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