Can It Make Your Child Smarter?
Choline is also in breastmilk
The implications for humans are profound, said the researchers, because the collective data on choline suggests that simply augmenting the diets of pregnant women with this one nutrient could affect their children's lifelong learning and memory. In theory, choline could boost cognitive function, diminish age-related memory decline, and reduce the brain's vulnerability toxic insults.
The Duke group is part of a national team of scientists who are exploring the benefits of prenatal choline supplementation on learning and memory. This ongoing research has been instrumental in the Institute of Medicine's decision to elevate choline to the status of an essential nutrient for humans -- particularly pregnant and nursing women, the scientists say.
Results of their study, led by Qiang Li, MD, of Duke and the Durham VAMC, were published in the April 2004 issue of Journal of Neurophysiology.
"Previous studies at Duke have shown that choline-supplemented animals are smarter and have a greater learning capacity, but we hadn't known until now whether the cells that make up memory-relevant brain circuits are changed by choline" says Li. "Choline didn't just change the general environment of the brain, it changed the fundamental building blocks of brain circuits -- the cells themselves."
Choline is a naturally occurring nutrient found in egg yolks, milk, nuts, fish, liver and other meats as well as in human breast milk. It is the essential building block for a memory-forming brain chemical called acetylcholine, and it plays a vital role in the formation of cell membranes throughout the body.
In the current study, the researchers explored the effects of choline on neurons in the hippocampus, a brain region that is critical for learning and memory. They fed pregnant rats extra amounts of choline during a brief but critical window of pregnancy, then studied how their hippocampal neurons differed from those of control rats.
The researchers found that hippocampal neurons were larger, and they possessed more tentacle-like "dendrites" that reach out and receive signals from neighboring neurons.
"Having more dendrites means that a neuron has more surface area to receive incoming signals," says Scott Swartzwelder, PhD, senior author of the study and a neuropsychologist at Duke and the Durham VA Medical Center. "This could make it easier to push the neuron to the threshold for firing its signal to another neuron." When a neuron fires a signal, it releases brain chemicals called "neurotransmitters" that trigger neighboring neurons to react. As neurons successively fire, one to the next, they create a neural circuit that can process new information, he says.
Not only were neurons structured with more dendrites, they also "fired" electrical signals more rapidly and sustained their firing for longer periods of time, the study showed. The neurons also rebounded more easily from their resting phase in between firing signals. These findings complement a previous study by this group showing that neurons from supplemented animals were less susceptible to insults from toxic drugs that are known to kill neurons.
Collectively, these behaviors should heighten the neurons' capacity to accept, transmit and integrate incoming information, says Swartzwelder.
"We've seen before that the brains of choline-supplemented rats have a greater plasticity -- or an ability to change and react to stimuli more readily than normal rats -- and now we are beginning to understand why," he says.
The researchers demonstrated these neuronal behaviors by placing tiny electrodes within the neurons. Then, they prompted neurons to fire signals by changing the electrical voltage across the cells, (called depolarization). As neurons began to fire, they measured their firing rates and the recovery interval between each firing. "Overall, we found that neurons in choline-exposed rats were more excitable, more robust in their physiologic response," says Wilkie Wilson, PhD, a Duke pharmacologist and member of the team at the Durham VAMC. "We've demonstrated a measurable change in brain cells prompted by moderate amounts of choline given during a narrow window of prenatal development."