The stimulation of hunger…causes mice to take in information more quickly, and to retain it better — basically, it makes them smarter. And that’s very likely to be true for humans as well.
Why? Because of ghrelin, “a hormone produced by the stomach lining, when the stomach is empty.”
To the scientists’ surprise, they found that ghrelin was binding to cells not just in the primitive part of the brain that registers hunger (the hypothalamus) but also in the region that plays a role in learning, memory and spatial analysis (the hippocampus).
How did they discover this connection?
The researchers…put mice injected with ghrelin and control mice through a maze and other intelligence tests. In each case, the biochemically “hungry” mice — mice infused with ghrelin — performed notably better than those with normal levels of the hormone. The finding was startling, but “it makes sense,” Horvath says. “When you are hungry, you need to focus your entire system on finding food in the environment.” In fact, some biologists believe that human intelligence itself evolved because it made early hominids more effective hunters, gathers and foragers.
What are the practical implications? Horvath doesn’t say but Christopher Shea in The New York Times Magazine speculates we should undertake cognitively demanding tasks
mildly hungry, not carbo-loaded for endurance, and snack to maintain that edgy state. Such advice, applied on a national scale, might help save our schools. Since overweight kids have suppressed ghrelin levels, Horvath theorizes that perhaps the obesity epidemic has contributed to declining test scores and other American educational woes.
The gut hormone and neuropeptide ghrelin affects energy balance and growth hormone release through hypothalamic action that involves synaptic plasticity in the melanocortin system. Ghrelin binding is also present in other brain areas, including the telencephalon, where its function remains elusive. Here we report that circulating ghrelin enters the hippocampus and binds to neurons of the hippocampal formation, where it promotes dendritic spine synapse formation and generation of long-term potentiation. These ghrelin-induced synaptic changes are paralleled by enhanced spatial learning and memory. Targeted disruption of the gene that encodes ghrelin resulted in decreased numbers of spine synapses in the CA1 region and impaired performance of mice in behavioral memory testing, both of which were rapidly reversed by ghrelin administration. Our observations reveal an endogenous function of ghrelin that links metabolic control with higher brain functions and suggest novel therapeutic strategies to enhance learning and memory processes.
There is, of course, another obvious take away. Faced with a mouse problem in your apartment, house or barn, feed those little guys. A lot. Then they’ll have a harder time outsmarting your cat, whom you should put on a diet. And if your cat complains about his meager diet, just explain (using meows, purring and raking various furniture) that circulating ghrelin enters the hippocampus and binds to neurons of the hippocampal formation, where it promotes dendritic spine synapse formation and generation of long-term potentiation.