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Nervous System


Types of Memory As shown in Figure 03a, the ability to modify our behaviour in response to life's experiences is shared by all animals including the bacteria E. coli. Such feat requires the brain's willingness to learn. Learning results in the formation of memories and in humans this process reaches its most sophisticated form, allowing us creatively to associate different reflections on the past, to generate new ideas, and most importantly to acquire language as a medium of expression and communication. Memory requires the brain to be physically altered by experience and it is this remarkable property that makes thought, consciousness, and language possible. The basic mechanism of memory formation is highly conservative over billion years of biological evolution. The difference in humans is that we have a lot more of the stuffs. There are about 100 trillion synaptic connections in our brain.

Figure 24a Memory Classification
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Memory There are many ways to classify the memory. The concept of explicit and implicit memory refers to whether or not the recollection is produced consciously and intentionally. While the scheme of declarative and nondeclarative memory depend on the retrieval that can be declared verbally or not. Associative memory is triggered by clues; nonassociative memory can be habitual or sensitive. There are also short term and long term memory. One of the classification schemes is shown in Figure 24a. Table 07 is an attempt to put them all together. In the table, the declarative, and the procedural memory are explicit with the rest of nondeclarative memories being implicit. Only the working memory belongs to the category of short term memory fading away in hours, while the others are long term, and available for retrieval in years. Figure 24b shows the components, locations, and pathways for many types of memory.

Figure 24b Types of Memory
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Type Location(s) Function Example(s)
Working Memory
Phonological Loop Left hemisphere Rehearsing verbal information to keep it in the short-term memory String of numerals and alphabets such as telephone numbers
Visual-spatial Scratch Pad Visual Cortex Controlling visual imagery Scanning text
Central Executive Frontal lobe Controlling awareness of the information in working memory Constructing sentence, comprehending speech
Non-declarative Memory
Procedural Memory Cerebellum, temporal lobes Managing "how to" Riding a bicycle, kungfu exercise
Classical Conditioning Cerebellum Forming habitual behaviour Coffee break, afternoon tea
Fear Memory Amygdala Emotional conditioning Phobias, flashbacks
Nonassociative Memory Spinal cord Habituation and Sensitization Decreased or increased responsiveness to stimulus
Remote Memory (Priming) Scattered around the cortex Foundation for new memories Childhood memory
Declarative Memory
Episodic Memory Cortex Remembering past experience Some enchanted evening
Semantic Memory Frontal lobe, temporal lobe Registering facts Meanings of words and symbols

Table 07 Types of Memory