to interrupt epileptiform stimulus-train-induced bursting. Figure 2 shows hyperpolarization
and interruption of neuronal firing by orange light in hippocampal neurons transfected by
halorhodopsin. In the lower traces epileptiform bursting induced by tetanic afferent
stimulation is blocked reversibly by orange light.
The ability to selectively activate or inactivate certain specific neuronal populations likely
will have game-changing impact on our understanding of functional neuroanatomy and
neurophysiology in health and disease. Whether it will lead to a practical treatment for
epilepsy is less clear. Barriers to applying optogenitic techniques for clinical epilepsy
include the need for a conveniently implantable light stimulation system, demonstration of
safety of viral transfection of these ion channels into human brain, and verification of long-term neural control, without producing unexpected changes in brain function.