Through neural connections, called synapses, the brain can process and store enormous amounts of information. Neuroscientist Gary Lynch at the University of California-Irvine explains how this incredibly complex communication process allows animals to learn and remember. "Mysteries of the Brain" is produced by NBC Learn in partnership with the National Science Foundation.
Mysteries of the Brain - Thinking Brain
TOM COSTELLO, reporting:
Learning from experience - in the animal kingdom it can mean the difference between life and death. From eagles to whales to humans, animals use the information they learn in their environment each day, changing their actions to aid in their survival. And it's all due to one of the most mysterious organs we all possess: the brain.
GARY LYNCH (University of California, Irvine): The brain is essential to all activities, of course. But the thing that separates it from all other organs is this incredible ability to absorb information from the world.
COSTELLO: Dr. Gary Lynch is a neuroscientist at the University of California, Irvine. With funding from the National Science Foundation, he is researching what lies behind the brain's ability to learn and remember.
LYNCH: Every instant of the waking day you're accumulating information.
COSTELLO: To process, organize, and store all the information, the brain employs cells called neurons. Neurons are basic to all brains, from roundworms to humans. When a puppy sniffs out a new playmate, or a panda discovers snow, the information, in the form of electro-chemical signals, is received by the neuron's antennae-like dendrites, processed in the cell body, and then passed along through the axon to the next cell in just a fraction of a second. In a human brain, the neuron connects to as many as 10,000 other neurons, which connect to thousands of other neurons, creating a vast communication network throughout the brain.
LYNCH: So when you think about the neuron, the big antenna and the long wire, you can begin to get the picture of the web being built.
COSTELLO: Neurons communicate with each other through a junction called a synapse, where information signals are transmitted and received. An electrical signal, called an action potential, travels down the axon of the "talking" neuron until it reaches the axon terminal, releasing chemical neurotransmitters into a minuscule gap. Spines on the dendrites of the “listening” neuron have special protein receptors that bind with the neurotransmitters. This complex messaging sequence is repeated by the thousands every second.
LYNCH: So just think of that. Twenty-four hours a day throughout your life, fifty billion of these things are doing this and you get an image of the complexity.
COSTELLO: If the same signal is repeated several times, as with training or practice, more synapses are affected and synaptic communication becomes stronger. So animals can recall which foods to eat, where to find water, and how to get home from work - everything animals learn from interaction with the environment.
LYNCH: And so your memory is becoming more and more secure because more and more neurons, more and more of the synapses have got that information.
COSTELLO: Not only can synapses get stronger, but they can also get weaker or even disappear, depending on how often the synapse is used. Communication between neurons is altered by changes in the amount of neurotransmitter released, the number and sensitivity of the neuro-receptors, and the number and shape of dendritic spines. This means that the brain is continually building, pruning, and reshaping the network of neurons. In his lab, Lynch demonstrates this by passing electrical impulses through the brain of a rat. When the signal travels through the synapse, he is able to measure and record the voltage the synapse receives. When the signal is repeated, it generates a larger voltage, signifying a stronger synaptic connection. Lynch explains that this is because the dendritic spines are changing shape, allowing for stronger synaptic communication.
LYNCH: When it sends that message, this spine, this dendritic receiver morphs and, if everything goes right, it will morph into a state that forever afterwards, when the message comes, it generates a bigger voltage.
COSTELLO: Much of the brain's dynamic synaptic structure still remains a mystery. But Lynch and his team are determined to unlock the secrets of learning and memory.
Thanks to scientists who have ventured outside the laboratory, we have learned that tight-knit groups of females experience synchronized menstrual periods over time, that cohesive groups engaged in decision-making discount dissenting viewpoints in the interests of consensus, and that couples who stay together long enough begin to look alike.
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