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April 03, 2025

[Brain Image]    

PSY 340 Brain and Behavior

Class 32 Learning, Memory, and Memory Loss

   

I. Localized Representations in Memory

Our experiences in life teach us things: putting our finger into a flame or an electrical socket will hurt, eating ice cream will usually taste really good, smiling at our boy- or girl-friend is more likely to keep them around than a frown, and failing to show up at work will usually get us fired. It seems as if learning connects one thing to another.

In the late 19th and first half of the 20th century, behavioral psychologists developed elaborate theories that we learn such connections because of our experiences.

[Karl
            S. Lashley]Karl Lashley's FAILED Search for the Engram

[Lashley's Search for the Engram]University of Chicago and, later, Harvard physiologist and psychologist, Karl Lashley, wanted to find where learning resided in the brain. In the period from roughly 1920 to 1955, Lashley searched after the "engram" -- the physical representation (or memory trace) in the brain of what has been learned.

To do so, Lashley performed two general types of experiments.

Cortical Cuts. First, he trained rats to learn how to find food in mazes. When they had learned this, he performed operation on the rats by cutting areas of the cortex. He theorized that, if there was a link between two areas of the brain as a result of learning, he might pinpoint that link by making the cuts. The diagram shows you the different places where he cut the rat brain. When each rat recovered from the operation and put back into the maze, they didn't show any evidence of loss of learning.

Tissue Ablation. The second experiments involved maze learning as well. When the rats had learned to manouver in the maze, he performed a "tissue ablation" -- that is, he cut different amounts of tissue from the rat's cortex. The rats later on did more poorly in running the maze. But, it appeared to Lashley to be the amount of lost brain tissue, not the place where the tissue was removed that was related to poorer performance.

Lashley's Principles for the Nervous System. Lashley rejected the notion of localized learning. Rather he proposed two principles:

We know that Lashley was wrong about both of these principles? Why? He assumed (1) the engram (memory trace) is only in the cortex and (2) all memories are the same physiologically.

  The Modern Search for the Engram: Conditioning & the Lateral Pontine Nucleus of the Cerebellum

[Lateral Pontine Nucleus] Richard Thompson

II. Types of Memory

[Donald O.
            Hebb]   Short- and Long-Term Memory

Donald O. Hebb proposed in the late 1940s a model of memory with two different components:

Changing Views of Consolidation

Earlier view: Consolidation is a general & simple process leading to a permanent long-term memory. But, this is no longer a viable option because

[Baddeley's
          Working Memory Model]   Alan Baddeley's "Working Memory": A Modern Advance
In the early 1990s, Alan Baddeley (U York, UK) and his colleagues proposed a newer model of memory: working memory. This was revised in 2000-2001 and now includes 4 elements:

Dorsolateral prefrontal cortexWe may also have working memory systems for the other senses (touch, taste, smell), but not much research has been done on them.

Testing the "working memory" model uses delayed response tasks = respond to a stimulus that was seen or heard a short time ago with a time delay inserted between the perception and the response.

What parts of the brain are active during the delay, that is, while the working memory is rehearsing or holding the memory? Most active appears to be the dorsolateral prefrontal cortex. However, multiple other areas of the prefrontal cortex are involved in other aspects of working memory besides rehearsal.


III. Memory Loss (Amnesia)

  A. Korsakoff's Syndrome & Other Prefrontal Damage

Wernicke's encephalopathy (WE) is an acute brain disorder in which a patient coming into a hospital has (1) profound global confusion, (2) difficulty in coordinating muscle movements (ataxia), and (3) problems using their eyes. It is fatal in 10-20% of cases coming to a hospital. It is caused by a deficiency of thiamine (vitamin B-1). 80% of patients surviving Wernicke's encephalopathy go on to develop Korsakoff's Syndrome (KS).

WE often develops in individuals with alcoholism. Other conditions that may result in WE include patients who have undergone bariatric surgery for permanent weight loss, other forms of gastrointestinal surgery, cancer, and pancreatitis (Kohnke & Meek, 2021).

WE is often under-diagnosed in living patients.

  Korsakoff's Syndrome (KS; also known as Korsakoff Psychosis)

[Mammillary bodies]  [dorsomedial
            nucleus]

The brain area damaged includes the mammillary bodies (beneath the hypothalamus) and the dorosmedial (or mediodorsal) thalamus (nucleus connected to pre-frontal cortex).

Patients with KS often show

Prevalence of KS. This condition is relatively rare. Consider what the number of cases might be in the US (which, in 2020, had a population of 331 million) Arts et al. (2017) note that there is very little data about the prevalence and what data there is show a range of values:

  B. Alzheimer's Disease

Go to full PowerPoint Presentation and/or

PowerPoint Slides (8 pp., pdf format)


References

Alzheimer’s Association. (2024). 2024 Alzheimer’s disease facts and figures. Alzheimer’s & Dementia, 20(5), 3708-3821.  https://doi.org/10.1002/alz.13809

Alzheimer's Genetics Factsheet. (2015, August). Washington, DC: National Institutes of Health, National Institute on Aging. https://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-genetics-fact-sheet

Arts, N. J. M., Walvoort, S. J. W., & Kessels, R. P. C. (2017). Korsakoff’s syndrome: A critical review. Neuropsychiatric Disease and Treatment, 13, 2875-2890. https://doi.org/10.2147/NDT.S130078

Carey, B. (2008, December 4). H.M., an unforgettable amnesiac, dies at 82. New York Times. [Obituary]

Couthard, E. J., & Love, S. (2018). A broader view of dementia: Multiple co-pathologies are the norm. Brain, 141(7), 1894-1897. doi: 10.1093/brain/awy153

Genoux, D., Haditsch. U., Knobloch, M., Michalon, A., Storm, D., & Mansuy, I. M. (2002). Protein phosphatase 1 is a molecular constraint on learning and memory. Nature, 418(6901), 970-975. [PubMed Abstract]

Hudomiet, P., Hurd, M. D., & Rohwedder, S. (2022) Trends in inequalities in the prevalence of dementia in the United States. PNAS, 119(46), e2212205119. https://doi.org/10.1073/pnas.2212205119

Jansen, I. E. et al. (2019) Genome-wide meta-analysis identifies new loci and functional pathways influencing Alzheimer’s disease risk. Nature Genetics, 51, 404-413. https://doi.org/10.1038/s41588-018-0311-9

Koknke, S., & Meek, C. L. (2021). Don’t seek, don’t find: The diagnostic challenge of Wernicke’s encephalopathy. Annals of Clinical Biochemistry, 58(1), 38-46. https://doi.org/10.1177/0004563220939604

Kolata, G. (2011, April 3). Vast gene study yields insights on Alzheimer's. New York Times. Retrieved from http://www.nytimes.com/2011/04/04/health/04alzheimer.html

Kolata, G. (2019, April 8). The diagnosis is Alzheimer's. But that's probably not the only problem. New York Times. Retrieved from https://www.nytimes.com/2019/04/08/health/alzheimers-dementia-stroke.html

Mendez, M. F. (2019) Early-onset Alzheimer disease and its variants. Continuum, 25(1), 34-51. https://dx.doi.org/0.1212/CON.0000000000000687

Mental Health: A Report of the Surgeon General
. (1999). Chapter 5. Older Adults and Mental Health: Alzheimer's Disease. Washington, DC. Downloaded 04/17/05 from the Web site: http://www.surgeongeneral.gov/library/mentalhealth/chapter5/sec4.html

Newhouse, B. (2007, Feb 24). H.M.'s brain and the history of memory. Weekend Edition Saturday, National Public Radio. [incudes audio recording].

Robinson, J. L., Lee, E. B., Xie, S. X., Rennert, L., et al (2018). Neurodegenerative disease concomitant proteinopathies are prevalent, age-related and APOE4-associated. Brain, 141, 2181-2193.

Scheltens, P. et al. (2021). Alzheimer’s disease. Lancet, 397, 1557-1590. https://doi.org/10.1016/S0140-6736(20)32205-4

Stallard, P. J. E., Ukraintseva, S. V., & Doraiswamy, M. (2025, March 12). Changing story of the demential epidemic. JAMA. Online. https://dx.doi.org/10.1001/jama.2025.1897

 

 
The first version of this page was posted on April 17, 2005