Memory

Memory د.وليد عزيز العميدي

? Memory is the most critical mental facility we possess with regard to our ability to operate as human.
? We make almost all decisions about what to do based on memories of one sort or another.
? Three important distinctions :
1- Three stages of memories.
2- Different memories for storing information for short and long periods.
3- Different memories being used to store different kinds of information ( e.g. one system for facts and another for skills).
Three stages of memories
1- encoding stage : when environmental information is translated into and stored as a meaningful entity( physical input , sound waves “ name” ).
2- storage stage : when stored information is maintained overtime.
3- retrieval stage : ability to pull from memories information that previously encoded and stored there.
? Memories can fail at any of these 3 satges
? Recent studies suggest that the different stages of memories are mediated by different structures in the brain .
PET and FMRI ( measures of brain activity are recorded while participants are engaged in tasks:
? During encoding : left hemisphere mostly activated .
? During retrieval : right hemisphere mostly activated.
Three memory stores
? Memory processes differ between situations that requires us to store material :
1- for less than a second .
2- for a matter of second.
3- for longer interval ranging from minutes to year.

ATKINSON-SHIFFRIN theory (1968) : the basic tenets of this theory are as follows:
1) Informations arriving from environment is first placed into what is termed sensory store which has 3 main characteristics :
1-contains all the informations from the environment captured by the sense organs .
2-sensory store is transient (decays over a time few tenths of a second (visual store) to a few seconds (auditory store ).
3- the small proportion of informations in the sensory store that is attended to is transferred out of the sensory store into the next major component of the system (short term store)
2) short term store : 5 main characteristics :
1- contain informations that we are conscious of.
2- readily accessible( make decisions and carry out tasks).
3- will decay (forgotten) over a period of approximately 20 sec.
4- can be prevented from decaying if it is rehearsed .
5- informations in short term store can undergo other forms of processing , collectively known as elaboration( e.g. being transferred into a visual image). ?

3) long term store : is the large repository of informations that we maintained of all informations that is generally available to us.
3 main characterstics:
1- informations enters it via various kinds of elaborative processes , from short term store.
2-the size of long term store is unlimited.
3- informations is acquired from long term store via the process of retrieval and placed back into short term store , where it can be manipulated and used to carry out the task at hand. ?

Different memories for different kinds of informations
? Explicit memory (declerative) : in which the person consciously recollects an event as occuring in a particular time and place , 2 types :
1- episodic memory (personal informations).
2- semantic memory (facts and general truths).
? Implicit memory (procedural) ( nondeclerative) : in which a person unconsciously remember informations of various sorts , like skills , priming and conditioning .


- Sensory memory: information initially acquired from the environment via sense organs , so there are sens. Memory corresponding to all sens. Modalities : vision (iconic mem.) and audition (echoic mem.).

- Working memory : (short term mem.)
? Encoding :we are selective about we attend to , our working mem. Will contain only what has been selected , this means that much of what we are exposed to never even enters working mem.
Phonological coding : sounds of items(digits).
Visual coding .
? Storage : limited capacity , on average 7 +-2(5 – 9) , this no. determined by digit span tasks . ( showing people various sequences of unrelated items ( digits , letters or words ) and asking them to recall the item in order ).
Chunking : is recording new material into larger , more meaningful units and storing those units in working memory , such units are called chunks .
Chunking can occur with no. and letters .
The general principle is that we can boost our working mem. By regrouping sequences of letters and digits into units that can be found in long term memory.
? Retrieval : more items there are in working mem. , the slower retrieval becomes .
Causes of forgetting either decay over time or displaced by new items.

Transfer from working mem. To long term mem.
Working mem. Serves 2 important functions :
1- it stores material needed for short periods.
2- way station to long term mem.
Rehearsal is the conscious repeatition of information in working mem. , it helps the transfer of informations to long term mem.

Working mem. And long term mem.are implemented by different brain structures :
In particular the hippocampus ( located near the middle of brain beneath the cortex , is critical for long term mem. But not for working mem. , while neurons in prefrontal lobes , just behind the forehead hold information for short term use .

- Long term memory : is involved when information has to be retained for intervals as brief as a few min. or as long as a life time ( such as adults childhood mem.).
Informations in long term mem. Is usually encoded according to its meaning . If the items to be remembered are meaningful but the connection between them are not , mem. Can be improved by adding meaningful connection that provide retrieval paths .
Causes of forgetting : -retrieval failure which occur more likely when there is interference from items associated with the same retrieval cue.
- Loss from storage , particularly when there is disruption of the process that consolidate new mem.

? Emotional factors in forgetting : emotion can influence long term memory in 5 distinct ways :
1- rehearsal : we tend to think about emotionally charged situations , negative as well as positive more than we think about neutral ones.
2- flashbulb memory : is a vivid and relatively permanent record of the circumstances in which one learned of an emotionally charged significant event ( challenger 1986 ).
3- retrieval interference via anxiety .
4- context effect : memory is best when the context at the time of retrieval matches that at the time of encoding .
If the material we are learning makes us feel sad perhaps we can best retrieve that material when we are feel sad again.
5- repression : Freud proposed that some emotional experiences in childhood are so traumatic that allowing them to enter consciousness .
So some traumatic experiences are said to be repressed or stored in the unconsciousness .

? Childhood amnesia :
Virtually no one can recall events from the first year of life .
This curious phenomena was first discussed by Freud (1905) who called it childhood amnesia.
Freud discussed the phenomena by observing that his patient were generally unable to recall events from their first 3 to 5 y. of life .
What causes childhood amnesia? It is due to massive difference between how young child encode experience and how adult organize their memory .

? What causes the shift from early childhood to adulthood phenomena forms of memory ?
1- biological development : the hippocampus which is involved in consolidating mem. is not mature until roughly a y. or 2 after birth therefore events that take place in the first 2 y. of life cannot be sufficiently consolidated and consequently cannot be recalled later.
2- at psychological level : include cognitive factors , particularly development of language and the beginning of schooling .
Language peak at age of 3.
Schooling at age of 5.
So 3 – 5 y. childhood amnesia ends.