Reacción a "Reactions: hibernation-like state induced in rats and mice by ultrasound"

There is a great deal of interest in the topic and research in this area is important. The possibility of human hibernation is obviously fascinating and has wide ranging implications - from clinical applications to space travel. For example, when metabolism is reduced, cells require less oxygen, and therefore in conditions such as stroke or heart failure hibernation can be neuroprotective. 

However, this study raises more questions than provides answers, in my opinion. First of all, the contribution of thermal stimulation must be controlled for and addressed. Perhaps stimulated neurons "feel" warmth induced by ultrasound stimulation and this is what induces compensatory hypothermia. Secondly, we know well that there are changes in body temperature in laboratory rodents occurring spontaneously, for example, hypothermia during sleep. I would be very interested to know whether ultrasound stimulation of the preoptic area of the hypothalamus induces altered state of arousal and awareness or may be even sleep? Overall, changes induced by stimulation in this study are rather modest.  

The key novelty is the attempt to use mechanical stimulation to induce hypometabolism, but given the caveat of thermal effects, which must be addressed, any conclusions from this study are preliminary. Generally it fits with evidence, but I would say, provocatively, that it is not particularly difficult to induce a state of hypometabolism in laboratory mice by a variety of pharmacological and non-pharmacological means. The question always remains whether we are inducing normal, physiological hibernation or an abnormal state. We need to be careful because it can have very negative consequences for the body and the brain if it is "enforced". I talk about this in my recent TED talk.  

While it is highly likely that humans can hibernate, in some way, the underlying neurophysiological and molecular mechanisms can be quite different from other animals. For example, daily torpor can be induced in mice by acute fasting, and this does not happen in humans, as far as we know. Seasonal hibernators initiate preparation to hibernation many weeks before hibernation occurs, and this may happen even without any external inputs. Humans are less seasonal, and therefore mechanisms and meaning of hibernation in humans may be very different. Still, hibernation is a really clever strategy used by so many species to deal with adverse environmental conditions, and could fundamentally be a default state of our physiology, very similar across organisms including humans.