Page 64 - 84 human physiolofy part-1

Chapter 4

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 a structured record of facts, concepts, and skills that we have acquired.
The information in the semantic memory is derived from our own episode memory, such as that we can
learn new facts or concepts from experiences.

There are three main activities that are related to long term memory:

1. Storage
2. Deletion
3. Retrieval

Information for short term memory is stored in long term memory by rehearsal. The repeated
exposure to a stimulus or the rehearsal of a piece of information transfers it into long term memory.
Experiments also suggest that learning is most effective if it is distributed over time. Deletion is mainly
caused by decay and interference. Emotional factors also affect long term memory. However, it is
debatable whether we actually ever forget anything or whether it just sometimes becomes increasingly
difficult to retrieve it. Information may not be recalled sometimes but may be recognized, or may be
recalled only with prompting. This leads us to the third operation of memory, information retrieval.

There are two types of information retrieval:

1. Recall
2. Recognition

In recall, the information is reproduced from memory. In recognition the presentation of the
information provides the knowledge that the information has been seen before. Recognition is of lesser
complexity, as the information is provided as a cue. However, the recall may be assisted by the
provision of retrieval cues which enable the subject to quickly access the information in memory.

Language and Speech

Language depends on semantic memory so some of the same areas in the brain are involved in
both memory and language. Articulation, the forming of speech, is represented bilaterally in the motor
areas. However, language analysis and speech formation take place in most individuals in regions of
the left hemisphere only. The two regions involved are:

1. Broca's Area
2. Wernicke's Area

Broca's area is located just in front of the voice control area of the left motor cortex. This region
assembles the motor of speech and writing. For example, patients with lesions in this area:

1. Understand language perfectly
2. May be able to write perfectly
3. Seldom speak spontaneously

64 | Human Physiology