Learning and memory
complex cognitive processes compared to sperm whales, though they have still proven to be highly intelligent. Instead, ‘ a combination of the number of cortical neurons, neuron packing density, interneuronal distance and axonal conduction velocity ’ 5 seems to be the key, which all contribute to a high information processing capacity (IPC). Another common factor between these is that these all impact action potentials, such as having a higher frequency of action potentials, shorter travel distance for action potentials and increased speed/susceptibility. Therefore, to fully understand and get a grasp upon the inner machinations of the brain and the key to our cognitive abilities, it is clear we must first understand action potentials and their importance. An action potential, essentially, is a temporary shift in a neuron membrane’s potential, from negative to positive, caused by the opening of sodium channel proteins in a section axon membrane, prompting a flow of sodium ions into the axon down an electrochemical gradient, depolarizing the axon membrane and triggering more sodium channels to open, further increasing depolarization (this is positive feedback). As potential difference increases and the threshold value is reached, an action potential is generated, where depolarization at this section of the axon membrane causes a current flow into the next section of axon membrane, depolarizing it in turn. This process continues down the axon. Meanwhile, shortly after the action potential is generated, a refractory period begins where potassium ion channels open while sodium ion channels close, prompting repolarization. The potassium ion channel proteins then close and the sodium ion channel proteins in this section of membrane become responsive to depolarization again, allowing for the generation of another action potential. This is the quintessential process by which electrochemical signals are generated and travel through neurons and the brain as a whole, and these electrochemical signals are what facilitate the flowing of information between cells of the nervous system, which of course includes the brain. Therefore, a higher frequency of action potentials results in increased communication, shorter travel distance results in faster communication, and increased axonal conduction results in axon sections being more easily stimulated and sensitive to the generation and passing of action potentials, increasing speed of communication. However, therein lies the problem: action potentials simply comprise a communication system. The difference between humans and other animals cannot solely lie in a more efficient communication system within our brains as the key to the human experience does not lie in our ability to think or act quickly. Instead, it is more realistic to say that the action potentials simply provide a foundation, a framework in which communication between neurons can be prioritized. This process of prioritization is known as neuroplasticity, and is the true basis for learning. Neuroplasticity is described more specifically as ‘ the biological process by which the brain reorganizes its synapses in response to stimuli ’ , ‘ making relevant neural networks stronger, and irrelevant ones weaker, supporting processes such as learning and memory ’ . 6 Very simply, as you learn information, neural circuits are altered in your brain by the strengthening of synapses. As the information in question is reinforced, such as repeating that information to yourself in order to embed it in your memory, the presynaptic neuron is more and more intensely stimulated, the amplitude of the postsynaptic neuron’s
5 Dicke, U. & Roth, G. (2016): see note 3. 6 Moore, S. (n.d.) https://www.news-medical.net/life-sciences/What-is-Neuronal-Plasticity-and-Why-Is-It- Important.aspx.
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