GSU NEUR 3000 - NEUR 3000 - Chapter 24 (50 pages)

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NEUR 3000 - Chapter 24



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NEUR 3000 - Chapter 24

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Pages:
50
School:
Georgia State University
Course:
Neur 3000 - Hon Principles of Neuroscience
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MEMORY SYSTEMS NEUR 3000 Dr Joseph J Normandin LEARNING MEMORY Learning is a lifelong adaptation to an organism s environment through acquisition of new information or knowledge Memory is the retention of learned information Experience shapes memories Memories range from stated facts to ingrained motor patterns Several brain regions are involved in learning and memory TYPES OF MEMORY AND LACK THEREOF Declarative memory The facts that we know and can communicate to each other What you had for breakfast What color the sky is The slowly setting sun as a backdrop for your first kiss Your awesome neuroscience lecturer Yeah Remember him What a weirdo Easily learned but easily forgotten No idea what I had for breakfast Um no don t remember that lecturer dude I was texting lolz TYPES OF MEMORY AND LACK THEREOF Nondeclarative memory Procedural memory Memories for skills and behaviors You never forget how to ride a bike Learned fear You get stung by a wasp when you are little at the beach and it scares you You are forever afraid of buzzing insects These memories are not easily forgotten TYPES OF MEMORY AND LACK THEREOF TYPES OF MEMORY AND LACK THEREOF Short and long term memory Short term memories last on the order of seconds to hours You may remember what you ate for dinner last night but a week from now you probably will not Long term memories may last a lifetime Not all memories become long term memories Because some short term memories become longterm memories one hypothesis of memory formation is that it is a serial process A competing hypothesis is that these processes happen in parallel TYPES OF MEMORY AND LACK THEREOF TYPES OF MEMORY AND LACK THEREOF Working memory Working memory is a temporary storage of information that is limited in capacity We keep such memories in our head as we are doing different tasks and then quickly forget them A memory that you are rehearsing in your mind is a working memory If rehearsed enough the memory can be consolidated into a longterm memory The capacity of working memory is known as a digit span and is 7 2 arbitrary units Most easily understood as a sequence of 7 numbers 6883314 7 units If divided into more units you can increase capacity 978 688 3314 3 units TYPES OF MEMORY AND LACK THEREOF Memory systems are diverse and may be dependent on the sensory modality Individuals with specific cortical lesions may remember a sequence of number if they see it but cannot remember the sequence if they hear it TYPES OF MEMORY AND LACK THEREOF Amnesia A loss of memory and or ability to learn beyond normal every day forgetting A consequence of disease or trauma Concussion Alcoholism Encephalitis Stroke Tumor The type of amnesia where a person has a trauma and completely forgets who they are as portrayed in movies is quite rare More commonly trauma or disease produced limited memory loss with other non memory deficits When memory problems are not associated with other deficits it is called dissociated amnesia and this state is useful for understanding memory systems TYPES OF MEMORY AND LACK THEREOF Amnesia Can be divided into two categories Retrograde amnesia Loss of memory of events before the trauma TYPES OF MEMORY AND LACK THEREOF Amnesia Can be divided into two categories Anterograde amnesia Inability to form new memories THE ENGRAM Engram A physical representation or location of a memory Where and how is information stored in the brain Different types of memory are stored differently THE ENGRAM LASHLEY S EXPERIMENTS Karl Lashley American psychologist 1920s Trained rats to find food in a maze Learning the maze took many trials but eventually rats will remember the direct path to food Lesions of cortex could produce deficits in learning the maze i e needed more trials to learn Lesions of cortex could produce deficits in remembering the maze i e would not go directly to food as before Effects correlate with the size of the lesion THE ENGRAM LASHLEY S EXPERIMENTS THE ENGRAM LASHLEY S EXPERIMENTS Karl Lashley American psychologist 1920s Lashley concluded that memories are stored throughout the cortex and that there is no specific place that memories are stored Because the lesion are so large they each might have encompassed the place s where memory is stored In fact memories are stored in specific locations but the locations are widely distributed THE ENGRAM HEBB S MODEL Donald Hebb American psychologist 1940 s Reasoned that the representation of an object consisted of all the cortical cells activated by that object Cell assembly Short term memory the cells in the assembly remain active Long term memory assembly activity persists and a growth process occurs that strengthens connections in the assembly At a later time if a fraction of the assembly was activated the entire assembly would be active because of strengthened connections This model as stood the test of time but we are still understanding the details and refining the model THE ENGRAM HEBB S MODEL THE ENGRAM IN THE NEOCORTEX One consequence of Hebb s model is that the engram is dependent on the modality of the experience We see a circle and so seeing cells should hold the engram Experiments in monkeys Monkeys can discriminate between two objects to get a reward Lesions of the inferotemporal IT cortex produce deficits in visual discrimination Other visual systems are intact and working IT both responds to visual information and stores it THE ENGRAM IN THE NEOCORTEX THE ENGRAM IN THE NEOCORTEX One consequence of Hebb s model is that the engram is dependent on the modality of the experience We see a circle and so seeing cells should hold the engram Experiments in humans fMRI can be used to explore activity of neurons that are related to a person s experience THE ENGRAM IN THE NEOCORTEX The temporal lobe appears to be important for multimodal declarative memories Wilder Penfield Canadian neurosurgeon 1950s 60s During his time The greatest living Canadian Electrical stimulation of brains of neurosurgery patients http www youtube com watch v kNdM9JhTPJw THE ENGRAM IN THE NEOCORTEX The temporal lobe appears to be important for multimodal declarative memories Wilder Penfield Canadian neurosurgeon 1950s 60s When he stimulated the temporal lobes people experienced memories Are memories located in the temporal lobe or does the temporal lobe act as a recall initiation system of memories stored in another region Removal of the stimulated part of the temporal lobe in some patients did not make the memory go away


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