Memory

MEMORYpart one

Dr Mushtaq T Hashim M.B.Ch.B.-C.A.B.(Psych)

Introduction

Three major distinctions: Three stages of memory: encoding , storage & retrieval. Different memories for storing information for short and long periods: sensory ,working and long- term memory. Different memories being used to store different kinds of information : for example one system for facts and another for skills. There is evidence that these different entities are mediated by different structures in the brain.

Three stages of memory

There are three stages of memory : Encoding stage: environmental information is translated into and stored as meaningful entity. Storage stage : stored information is maintained over time. Retrieval stage :pulling from the memory information that was previously encoded and stored.

Three memory stores

The three stages of memory do not operate the same way in all situations. Memory processes differ between situations that requires us to store material for less than a second or for a matter of few seconds and for longer periods ranging from minutes to years. The Atkinson- Shiffrin theory: 1968 The basis for the distinction between different memories corresponding to different time intervals. Information arriving from the environment is first placed into what is termed sensory store, which has three main characteristics:


It contains all the information from the environment captured by the sense organs. It is transient. The small portion of information that is attended to is transferred to the next major component of the system, the short term (working) memory.


2- short- term store : has five main characteristics : a-can be roughly identified with consciousness. b-readily accessible. c-information decays over a period of approximately 20 seconds. d-decaying can be prevented by rehearsal. e-information can undergo other forms of processing ,collectively known as elaboration when it is transferred from short -term store into long term- store.



3- Long- term store : The large repository of information that we maintain of all information that is generally available to us. It has three main characteristics : a-information enters it via various kinds of elaborative processes, from the short- term store. b-the size of the long-term store is unlimited. c-information is acquired from the long term store via the process of retrieval and placed back into short term memory, where it can be manipulated and used to carry out the task at hand.

Different memories for different kinds of information

Evidence include many psychological and biological findings. Explicit memory: the person consciously recollects an event as occurring in a particular time and place. Implicit memory :the person unconsciously remembers information of various kinds (like information needed to carry out some physical tasks such as playing football ).

SENSORY MEMORY

The information initially acquired from the environment via sense organs. It holds large amount of information (faithfully represent the sensory information that enters the sense organs). It is short lasting. There are sensory memories corresponding to all sensory modalities. The most studied ones are vision (iconic memory) and audition (echoic memory).

Working memory

Short term store includes the information that has been attended to. Complicated more than what originally was postulated. Involves the three stages of encoding ,storage and retrieval. Encoding To encode you must attend. Selective attention. Phonological coding : encoding means entering information in a certain code or representation. We can use visual coding, or phonological coding, or semantic coding to enter information into working memory but the preferred one is the phonological. This is done by rehearsal .


Visual coding : Something like a photograph. When a patient must store non-verbal items (such as pictures ) that are difficult to describe and hence difficult to rehearse phonologically, the visual code become more important. Photographic clarity (children). eidetic imagery (rare).

Two working memory systems

Two distinct stores or buffers. Phonological buffer which store information in an acoustic code. Visual-spatial sketchpad which stores information in a visual or spatial code. Some studies indicate that the two buffers are mediated by different brain structures. Left hemisphere for acoustic buffer. Right hemisphere for visual-spatial buffer.

storage

retrieval
The more items in the working memory, the slower retrieval becomes. Retrieval needs a serial search. this search operates at a rate of 40 milliseconds per one item. The other possible way of retrieval is through an activation process. Working memory& thought Working memory plays an important role in thinking. Used in solving various kinds of problems, such as mental arithmetic ,geometric analogies, and answering questions about text.

Transfer from working memory to long- term memory

Working memory serves two important functions : It stores material that is needed for short term period. Serves as a work place for mental computations. Another possible function is serving as a way station to long term memory. The transfer may be done by several ways ,one of them is rehearsal. -rehearsal: is the conscious repetition of information in working memory : 1-maintenance rehearsal :holding information in working memory. 2-elaborative rehearsal :encoding information into long term memory.

Division of brain labor between working memory and long term memory

The hippocampus (a structure located near the middle of the brain beneath the cortex- in the middle of temporal lobe) is critical for long- term memory.Neurons in the prefrontal lobe, just behind the forehead, holds information for short term memory. These neurons act like a computer’s random access memory (RAM) chips.