Okinawa researchers put mice into 48 hours of artificial hibernation; more than half of hippocampal synapses vanished, yet fear and maze memory held. A Pittsburgh team used a 50 to 80 hertz thalamic pulse to improve speech after brain injury.
In a peer-reviewed study in the journal Science, a team at the Okinawa Institute of Science and Technology put mice into a hibernation-like state for 48 hours by activating Q neurons in the hypothalamus. Once that state set in, more than half of the synapses in the hippocampus were gone. After the animals woke, they still matched never-cooled mice on fear-conditioning and maze tasks.[1]
After arousal, vanished synapses in the Okinawa mice came back to the same spot on the same dendrite. Engram synapses that stood alone on a dendrite were eliminated, while those packed into tight clusters survived, and some of the surviving clustered synapses sat on a rare multisynaptic bouton that holds more than one synapse. A group that lost a comparable share of synapses came out with impaired fear memory; the authors say this separates the clustering pattern from general synapse loss. The experiments were done in mice.[1]
Researchers at the University of Pittsburgh stimulated the motor thalamus at 50 to 80 hertz, well below the 130 hertz used in standard deep brain stimulation, and improved control of the facial and tongue muscles that speaking and swallowing use. One participant had severe dysarthria, a speech disorder, after traumatic brain injury; others had intact speech pathways. Speech did not worsen in the people whose pathways were intact.[2]
