This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.
2000 First Web Report
In the world of science, the theory behind resting potentials and action potentials is widely known and accepted. But how does this lead to the hypothesis that electrical signals give rise to thoughts? The concept of learning and memory should probably be explored. Many studies have been done to determine the cause of making a memory and there are many evidences on the molecular level that may be able to link the phenomenal world with the noumenal world.
Memory is the process of storage/retrieval of information that results in a nearly permanent change in behavior -- creating new synapses between sensory and motor nerves, increasing the number of dendritic spines, and synthesizing new proteins. Information enters the brain in the form of a pattern of nerve cell activity. New memories stay in the hippocampus temporarily until they are transported to another part of the brain for permanent storage (1). The brain will permanently store this pattern of activity that may be recalled by permanently strengthening and weakening certain nerve cell connections. Memory is solidified in the temporal lobe of the brain - the hippocampus and the thalamus (2).
The memory model shows a linear representation of how experience is processed as memory. Stimulus --> Sensory Registration --> Attention --> Short Term Memory --> Consolidation - Retrieval --> Long Term Memory --> Remote Memory (3) At the stage of sensory registration, there is a matching/assigning of the pattern to a meaning. Short-term memory is temporary and is limited in space. If short-term memory is not repeated, the information is lost fairly quickly. Long term memory is consolidated and stored throughout the nervous system. Remote memory serves as groundwork for later memories - linking the new ones to the old.
There are many different types of memory and each is processed in different parts of the brain. Some examples are: long term memory is housed in the neocortex, "the amygdaloid nucleus contributes emotional amplifications to memory, the thalamic intralaminar nuclei and the activated brain stem reticular formation stimulate the imprinting of memories" (4), encoding pictures takes place in the right prefrontal and bilateral parahippocampus, encoding words takes place in left prefrontal and left parahippocampus, and memory consolidation takes place in the hippocampal system
There are two different types of memory. One is the non-declarative memory that allows one to remember skills and habits like brushing one's teeth or drawing a picture of a tree. This type of memory takes place in the basal ganglia, ventral thalamus, and premotor cortex circuit by the way of the neurotransmitter dopamine. The other is declarative memory where things like facts and figures (world knowledge and personal history) are explicitly recalled. These takes place in the medial temporal lobe, medial thalamus, and orbital prefrontal lobe circuit by the way of the neurotransmitter, acetylcholine (5).
Memory works on the basis of association. It links various pieces of information together and stores only what is necessary. The network of associations can change very quickly with new experiences. The brain is very efficient in that it has a filter system to decide what is necessary and what is not. Memory is very complex and is a system of associations and not just a single fact.
Amnesia can serve as evidence that the brain is the ultimate controller of one's thoughts. "Amnesia can result from diffuse cerebral impairment, bilateral lesions, or multifocal injuries that impair memory storage areas in the cerebral hemispheres" (4). Traumatic amnesia is when there is cerebral trauma, which can cause people to lose the ability to store new memories. Transient global amnesia is a short-lived amnesia that allows the person to register information but impedes the ability to retain and information during that period of the episode. There is a "temporary unifying spreading depression of electrical impulses in the brain" (6).
Evidence that shows that neurons lead to thoughts and emotions is that drugs can alter our thoughts as well as alter the physical neuron. There are many drugs that cause the loss of memory, such as tranquilizers, muscular relaxants, sleeping pills, and anti-anxiety drug (7). Piracetam and vasopressin help people with amnesia to remember (8). Some drugs like tabacco and alcohol affect our memory and in the latter, behavior.
Memory is an inconstant and impermanent pattern of neuronal connections. Experience shapes the neurons to retain memory. There seems to be an obvious understanding that every complex thought could be attributed to physical happenings of neurons. Therefore, from the empirical evidence presented so far, it can be loosely concluded that behavior does equal brain. It seems to me that the brain IS responsible for every thought, action, and emotion.
2)ZetaTalk: Multiple Personality
3)NEUROPSYCHOLOGY & BEHAVIORAL NEUROSCIENCE
6)Amnesia Enigma Solved (link no longer available)
7)Brain & Mind
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