Human Physiology/The Nervous System

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are attributed to changes in neuronal synapses, thought to be mediated by long-term potentiation and long-term

depression.

There are three basic types of memory:

1. Sensory Memory

2. Short Term Memory

3. Long Term Memory

Sensory Memory

The sensory memories act as a buffer for stimuli through senses. A sensory memory retains an exact copy of

what is seen or heard: 

iconic memory for visual, echoic memory for aural and haptic memory for touch.

Information is passed from sensory memory into short term memory. Some believe it lasts only 300

milliseconds, it has unlimited capacity. Selective attention determines what information moves from sensory

memory to short term memory.

Short Term Memory

Short Term Memory acts as a scratch pad for temporary recall of the information under process. For instance,

in order to understand this sentence you need to hold in your mind the beginning of the sentence as you read

the rest. Short term memory decays rapidly and also has a limited capacity. Chunking of information can lead

to an increase in the short term memory capacity, this is the reason why a hyphenated phone number is easier

to remember than a single long number. The successful formation of a chunk is known as 

closure. 

Interference

often causes disturbance in short term memory retention. This accounts for the desire to complete a task held

in short term memory as soon as possible.

Within short term memory there are three basic operations:

1. Iconic memory - the ability to hold visual images

2. Acoustic memory - the ability to hold sounds. Can be held longer than iconic.

3. Working memory - an active process to keep it until it is put to use. Note that the goal is not really to move the

information from short term memory to long term memory, but merely to put it to immediate use.

The process of transferring information from short term to long term memory involves the encoding or consolidation

of information. This is not a function of time, that is, the longer the memory stays in the short term the more likely it

is to be placed in the long term memory. On organizing complex information in short term before it can be encoded

into the long term memory, in this process the meaningfulness or emotional content of an item may play a greater

role in its retention in the long term memory. The limbic system sets up local reverberating circuits such as the

Papez's Circuit.

Long Term Memory

Long Term Memory is used for storage of information over a long time. Information from short to long term

memory is transferred after a short period. Unlike short term memory, long term memory has little decay.

Long term potential is an enhanced response at the synapse within the hippocampus. It is essential to memory

storage. The limbic system isn't directly involved in long term memory necessarily but it selects them from

short term memory, consolidates these memories by playing them like a continuous tape, and involves the

hippocampus and amygdala.

There are two types of long term memory:

1. Episodic Memory

2. Semantic Memory

Episodic memory represents our memory of events and experiences in a serial form. It is from this memory that we

can reconstruct the actual events that took place at a given point in our lives. Semantic memory, on the other hand, is