A new study shows that a circuit in a brain structure called the thalamus acts like a radio, with different stations operating at different frequencies and appealing to different “listening” audiences.

Stanford researchers have used optogenetic lasers targeted at the thalamus to turn whole-brain activity on and off in rats.  They hope that this will lead to improved optogenetic therapy for humans, as the thalamus controls memory, attention, and sleep.  The study was led by Jin Hyung Lee,  Hyun Joo Lee, Jia Liu, Andrew Weitz andZhongnan Fang.

By flashing high-frequency optogenetic lasers at the thalamus, the team woke sleeping rats and cause widespread brain activity. When they flashed the laser at 10 pulses per second,  the activity of the brain’s sensory cortex was suppressed, and the and  rats entered a seizure-like state of unconsciousness.

A combination of optogenetics, fMRI, EEG and single-unit cell recordings  detected overall effects on the brain.

According to Lee,  “using targeted, temporally precise ontogenetic stimulation allowed us to selectively excite a single group of neuronal elements and identify their specific role in creating distinct modes of network function. ” This could not previously be achieved with conventional electrode stimulation.

The results suggest that the central thalamus can either power the brain to an “awake” state or promote a state of unconsciousness, depending on how rapidly its neurons are stimulated.