How mobile neuron dendritic spines create memory
Anatomy and physiology lectures present a broad array of audio and visual cues that are aimed at helping your brain remember specific aspects of these sciences. The actual mechanism underlying your memory of these stimuli is best illustrated by the physiology and anatomical plasticity of the spines on brain nerve dendrites. The flexible anatomy of these very tiny brain compartments allows you to create memories that can be recalled and manipulated to answer questions about learned facts on exams.
Major types of memory
There are two major types of memories. They are declarative memory and procedural memory and each uses different brain pathways. Declarative or explicit memory includes memories of facts and knowledge. Procedural memory is an unconscious memory of how to do something like ride a bike, drive a car, type on a keyboard, text on a cell phone.
The hippocampus is the area of the brain most important to formation and consolidation of declarative memory – the type of memory you are trying to enhance when you study anatomy and physiology.
It is in the hippocampus that dendritic spine plasticity has been studied most completely. Because the physiology of memory is conserved across species most basic science studies have been accomplished using rats and monkeys.
When sensory organ output pathways send excitatory electrical signals to hippocampus neurons, the incoming sensory nerve terminals search for spines on the dendrites where they can build specialized connections called synapses.
Neuroanatomy of memory
Brain dendritic spines with their synapses are in a constant state of turnover. New spines form on brain dendrites, mature, and are pruned away in both the adult brain and in the developing brain of children.
The number, shape, and size of dendritic spines varies in direct correlation with the magnitude of sensory input. Average spine turnover rates have been reported to be as high as 6-15% per day.
Dendrite spines in the brain were first observed in histological sections over 100 years ago by Ramon y Cajal, a neuroscientist who won the Nobel Prize in 1906. Yet, it has only been in the past 10 years that technological developments have permitted detailed study of the relationship between structure and function at dendritic spines. In particular developments in fluorescent microscopy of the brains of living animals have permitted demonstration of the autonomy of dendritic spines as functional compartments within neurons.
Synapses on dendritic spines that receive high frequency auditory or visual stimuli become stronger. Increased spine strength correlates with larger spine size. The enlargement of the spine is due to an increase in new protein synthesis by the nerve cell body to better manage excitatory incoming traffic.
This process is tightly linked to an increase in intracellular calcium concentration in the spine. Dendritic spines where calcium remains low due to lack of neuronal signaling are pruned from the dendrite by the scavenger cells of the brain, the microglia.
Increased calcium in the dendritic spine promotes synthesis of molecules that travel to the neuron’s nucleus and turn on synthesis of new proteins for the synapse. Entire dendrites with many inactive spines are also pruned from neurons.
Hippocampus and formation of new memory
Damage to the hippocampus can result in loss of the ability to form new memories. This is known as anterograde amnesia and confirms the importance of the hippocampus for encoding memories. Consolidating an encoded memory for long-term use is a relatively slow process. It involves hippocampus driven transfer of the anatomical memory configuration to the neurons of the frontal cortical lobes of the brain.
Long-term memories stored in the frontal cortex service our ability to pay attention to details and organize information. The frontal cortex records not only the memory of facts but the source of those facts. If the original input signal to the hippocampus is strong and well organized, then the efficiency of the memory process is quite good.
Why organization of learning facilitates recall
Human noninvasive brain imaging studies show that memory recall follows pathways that are the reverse of those used for memory formation and memory consolidation. If the pathway of memory formation is complex, the process of recall will be complex as well.
It is important to keep your study process as simple as possible. Stick to the basics that you must learn and organize them in a logical fashion.
I realize that anatomy and physiology are large fascinating subjects but trying to learn them in a random fashion is a mistake. If you keep your notes and study plan well organized and focused upon the goals of you instructor, you will get the good grade you need so that you can move forward with your career.
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Do you have questions?
Please put your questions in the comment box or send them to me by email at DrReece@MedicalScienceNavigator.com. I read and reply to all comments and email.
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Margaret Thompson Reece PhD, physiologist, former Senior Scientist and Laboratory Director at academic medical centers in California, New York and Massachusetts and CSO at Serometrix LLC is now CEO at Reece Biomedical Consulting LLC.
Dr. Reece is passionate about helping students, online and in person, pursue careers in life sciences. Her books “Physiology: Custom-Designed Chemistry” (2012), “Inside the Closed World of the Brain” (2015) and upcoming “Step-by-step Guide for Study of Physiology” (2016) are written for those new to life science.
Dr. Reece offers a free 30 minute “how-to-get-started” phone conference to students struggling with human anatomy and physiology. Appointments are scheduled by email at DrReece@MedicalScienceNavigator.com.by