Lecturer: Dr. Benjamin Amponsah, Dept. of Psychology, UG, Legon Contact Information: bamponsah@ug.edu.gh College of Education School of Continuing and Distance Education 2014/2015 – 2016/2017
Session Overview • We introduce yet another process of memory – storage. Presumably, that is where the encoded information is stored in memory. We will look at the concept of storage and proceed to look at early attempts to locate the engram (the record left in memory by an experience). We will examine neuropsychological evidence of memory as well. Slide 2
Session Objectives • Appreciate the historical attempts to locate the engram • Examine the evidence from anterograde amnesia • Review neuropsychological literature concerning the location for storage of information Slide 3
Session Outline The key topics to be covered in the session are as follows: • Topic One: Historical Attempts to Locate the Engram • Topic Two: Evidence from Anterograde Amnesia • Topic Three: Neuropsychological evidence Slide 4
Reading List • Ashcraft, M. H. (2006). Cognition (4 th edn.), London: Pearson Education Int. • Galotti, K. M. (2004). Cognitive Psychology: In and out of the laboratory (3 rd Edn.). Belmont, CA: Wadsworth. • Hunt, R. R. & Ellis, H. C. (1999). Fundamentals of Cognitive Psychology (6 th edn.), New York: McGraw-Hill. • Willingham, D, B. (2001). Cognition: The thinking animal . NJ: Prentice-Hall. Slide 5
Topic One HISTORICAL ATTEMPTS TO LOCATE THE ENGRAM Slide 6
What is Storage? • What is Storage? – By storage, we are referring to the tendency to think that our memory is a vast warehouse into which we put or store things. – This is a metaphor , because physical traces of our experience cannot be seen in our brain, nevertheless, we believe our brains make some kind of neurological copy of our experiences and this copy is retained for use whenever we need it. Slide 7
What is Storage? • To complete the metaphor, it is also reasonable to believe that when we are remembering something, we direct some part of our brain to look for the neurological copy. • Brain Writing describes the idea that the brain makes a physical trace of our experiences (Dennett, 1981). Slide 8
What is Storage? • Researchers make a comparison between brain storage and computer storage . For example, if I store a picture on my computer, it leaves a physical trace in terms of codes when the information is saved. • With appropriate cues (file name etc.) the computer can “ re- experience ” this information when the appropriate cues are reinstated. • The same process is experienced when we consider human information processing. When we encode , we store the information and with appropriate cues we retrieve the information. Slide 9
Some Early Experimental Work • The Experimental Work of Karl Lashley • Karl Lashley, a zoologist born in 1890 studied in John Hopkins University in 1914. He studied there with J. B. Watson whose research on learning developed from the ideas of Ivan Pavlov – the classical conditionist. • Pavlov produced a fairly specific notion of the neurological changes underpinning learning and believed that learning was accompanied by certain structural changes in the brain. • Parts of the brain that had not communicated neurally prior to learning were associated ( coupled ) during learning and this association took the form of a physical, neural connection. Slide 10
An outline of the Structure of Neuron
Representation of Good and Poor Memory
Lashley’s Effort to Locate the Engram ● Once the association is formed, it could not be decoupled ; but the association depended upon the continued integrity of the neural connection. ● If the connections were destroyed by accident or disease, whatever had been learned through the association would be lost. ● How did Lashley prove this theory? ● First, he trained rats to run one of a set of mazes with different levels of difficulty from easy to hard. Slide 13
Lashley’s Effort to Locate the Engram • After the rats became proficient in running the mazes, he systematically cut the cortex (outer layer of the brain) of each rat; the cuts were made in different locations in each rat’s brain. • Lashleys assumption was that by such cuts, there should be interruption in the critical connections in the rats’ brains, and that the rats will show memory deficits on running the mazes. Slide 14
Lashley’s Effort to Locate the Engram • Lashleys expectations proved inaccurate. No matter where the cut was made, the rats still excelled. • Is it possible that he may have missed the critical connections in every animal? This seems remote. • What is likely is his conclusion that learning and memory don’t seem to involve specific connections in the brain. • Lashley repeated the experiment by removing more brain tissue of some of the rats as they run complicated mazes, but once again the location from which the tissue was removed proved irrelevant. Slide 15
Lashley’s Effort to Locate the Engram • At the end, the 30 year old search for the engram as a reification entity proved unsuccessful and currently, the term engram is used as a biological metaphor for what must in principle exist somewhere in the brain. Slide 16
Principles of Brain Organization • Lashley formulated two principles of brain organization: Mass Action - “The efficiency of performance of an entire complex function may be reduced in proportion to the extent of brain injury”. • Mass action means that the brain works en masse . If a small amount of brain tissue is removed, the brain can cope; but if a lot is removed, deficits will occur. Equipotentiality – means that all parts of the brain are created equal as far as learning and memory are concerned. No one part of the brain is more important than the other for memory storage. Slide 17
Principles of Brain Organization • We are not assuming that the location of damage in the brain is unimportant. A relatively small amount of damage to language or to vision centres can produce an irretrievable disability. • In other words, the principle of equipotentialilty may be true for humans up to a certain point because certain specialization within the brain also exist. If these areas are destroyed in an adult, complete recovery is almost impossible. Slide 18
Topic Two MEMORY STORAGE EVIDENCE FROM ANTEROGRADE AMNESIA Slide 19
Studies of Anterograde Amnesia – Karl Lashley’s approach to the understanding of memory storage was basically from experimental point of view. – His efforts failed to find any trace of memories in specific cerebral locations. In other experimental research (e.g., Mishkin, 1978) determined that various subcortical structures including the amygdala , thalamus and the hippocampus have been associated with memory loss in monkeys. Slide 20
Subcortical structures of a cross-section of the human brain implicated for memory function
The Case of HM • One often cited evidence by (Milner, 1959) is the study of H.M . (referred to this way to protect his privacy) who developed an incapacitating form of epilepsy, which was intractable to all forms of treatment, including the anti-epileptic drugs then in use. • His neurosurgeon William Beecher Stover (1953) performed surgery on him at the age of 27. Before the operation, H.M. was of normal intelligence, Stover removed many structures on the inner sector of the temporal lobes of both sides of H.M.’s brain, including most of the hippocampus, the amygdala and some adjacent areas. Slide 22
The Case of HM • This noticeably reduced H.M.’s seizures and his postoperative IQ actually rose about 10 points (Schacter, 1996). • However, a severe impairment resulted and he showed an inability to remember anything that had happed since his hippocampus was removed. Slide 23
The Case of HM • This form of memory loss is known as anterograde amnesia (after; inability to encode events after trauma) and can be distinguished from retrograde amnesia (before; retrieval failure prior to trauma). • H.M. showed little or no memory loss for events that had taken place prior to the operation. His working memory was not impaired (Milner, 1959). However, if H.M. was distracted during any short-term memory task, his performance was poor. Slide 24
The Case of HM • The following happened to H.M. The 29-year-old patient continued to give his age as 27 (two years after the operation). Reported that the operation had just taken place. His memory of events before the operation remained clear but could not form new long-term memories (anterograde amnesia). When his parents moved to a new house a few blocks away, he could not remember the new address. Slide 25
The Case of HM Month after month he read the same magazine over and over again without finding it familiar. His STM was fairly normal but if you left him and return 15 minutes later, he acted like he had not seen you before. His favourite uncle died years ago, but he suffered the same grief anew each time he was told of his uncle’s death. • H.M. was institutionalized for good because his life had no continuity. Slide 26
Summary • What we have learnt from his disability is that although we are unable to locate a specific location of memory, the substructures such as amygdala, hippocampus etc., are all important determinants of what has been stored. Slide 27
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