Despite the fact that we have yet to identify where certain memories are located in the brain, we have learned a lot about the brain's structures that are involved in memory. Moreover, we can now identify many neurotransmitters and hormones that are involved in memory functions, and pinpoint how neurons and synapses change as a result of learning. We have learned a lot about memory from patients suffering from memory-related problems, and studies conducted in young children also have revealed why we have such a hard time remembering the first few years of our lives.
Brain Structures Involved in Memory
When Dr. Karl Lashley began his now-classic studies in the 1920s, he believed that an area in the cerebral cortex was the home of long-term memory. He was mistaken. In his book "Brain Mechanisms and Intelligence," published in 1929, Lashley concluded that it was the amount of brain damage, not the location, that affected learning and memory the most.
Yet, other scientists after Lashley discovered that although the cortex works together as a whole, there are some cerebral areas that are more crucial for memory and learning than others. One of these areas is the hippocampus. As shown by Dr. Larry R. Squire and colleagues in "The Medial Temporal Region and Memory Consolidation" in 1984, the hippocampus is involved in moving recently learned information into a more permanent storage in a process called memory trace consolidation.
Another important area in these kinds of processes is the amygdale. This area is active especially if there are strong emotions involved in the learning process, as shown by Dr. Larry Cahill of the Center for the Neurobiology of Learning and Memory, in his many studies published in the 1990s.
When it comes to our memories about "how to do things" such as drive a car or type a sentence, the role of the basal ganglia is crucial.
Neurochemistry of Memories
It is known that some neurotransmitters, such as serotonin and acetylcholine, increase neural transmissions associated with your memory. Neurotransmitters are chemicals that help neurons to communicate with other cells. A study by by Dr. Nancy J. Woolf, published in the journal "Progress in Neurobiology" in 1998, suggests that some neurotransmitters may cause changes in a part of the neuron called the dendrite that sends information to other cells. Many drugs and alcohol interfere with neurotransmitter functions in strong ways, explaining the memory problems related to the abuse of these substances.
Neurophysiology of Memory
Memory is based on the firing and traveling of impulses from one neuron to another cell. Learning and memory affect both this process and the structure of the neurons. These changes, which represent the formation of a memory, are called memory traces. Repetition and recall of a memory further reinforce a memory trace, making it easier to access. These memory-related changes occur in neurons, synapses and neurotransmitters. For example, synapses tend to grow larger, and they tend to contain more neurotransmitters. It's also possible that the neurotransmitters are released more rapidly when the synapse is stimulated.
Patients with Memory-Related Problems
Alzheimer's patients suffer from severe memory dysfunctions. Many of these problems seem to be related to a significant loss of the brain tissue that secretes acetylcholine and norepinephrine. Cell damage in the hippocampus and the cerebral cortex may also explain the memory-related problems found in these patients. Korsakoff's syndrome is found commonly among extreme alcoholics. Researchers have found that the consumption of alcohol disrupts serotonin activity and, therefore, the formation of memories.
Infantile Amnesia
Infantile amnesia refers to the general inability of people to remember specific events from the early years of their lives. This infantile amnesia is likely because of the slow maturation rate of the hippocampus, and the frontal lobes that are crucial for long-term memory formation. After the intense maturation period of these areas later on, the memory functions typically also increase significantly.
References
- "Brain Mechanisms and Intelligence"; Dr. Karl Lashley; 1929
- "Memory Consolidation"; The Medial Temporal Lobe, the Hippocampus, and the Memory Systems of the Brain: A New Hypothesis.; Dr. Larry R. Squire, Neil J. Cohen, Lynn Nadel; 1984
- "Current Opinion in Neurobiology" ; Modulation of Memory Storage.; Dr. Larry Cahill, Dr. James L. McGaugh; vol. 6, 237-242, 1996
- "Progress in Neurobiology"; Structural Basis for Memory Storage; Dr. Nancy J. Woolf; 1998
