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This 5 page Class Notes was uploaded by Maymie Gaylord on Monday September 21, 2015. The Class Notes belongs to BIOL 6102 at Georgia State University taught by Staff in Fall. Since its upload, it has received 20 views. For similar materials see /class/209920/biol-6102-georgia-state-university in Biology at Georgia State University.
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Date Created: 09/21/15
Biol 6102 Neurobiology 111108 Memory Systems Chapter 24 Definitions 0 Learning is the process of acquiring knowledge 0 Memory is the retention and storage of knowledge 0 Remembering is the act of retrieving stored knowledge 0 Forgetting the extinction of memory Qualitative Categories of Memory Declarative Explicit Memory Conscious event memory Autobiographical ual o NonDeclarative Procedural Implicit Memory Unconscious often involves learning skills motor learning Includes priming Temporal Categories of Memo Short term seconds to minutes includes working memory Can be disrupted easily Can be improved with practice Associations help memory Short term memory is consolidated into longterm memory 0 Long term days years Retrograde and Anterograde Amnesia reveal that memory has different stages 0 Retrograde amnesia is the loss of memory before traum o Anterograde amnesia is the inability to form new memories after trauma Localization of memory the Engram or memory trace 0 Broca determined that loss of language occurred when specific areas were damaged Language is learned But maybe the loss had to do with a mechanism for producing language not its memory Penfield stimulated the brains of patients and elicited memories of previous experiences Lashley looked at the effect of cortical lesions on maze runnin Found that large lesions disrupted learning more than small lesions Concluded that memory is broadly distributed But his lesions were so large that they disrupted many systems 0 Hebb s cell assembly model of memory proposed that groups of interconnected neurons stored memories by changing their strength of connectivity This concept is used by artificial neural networks to encode information Researchers are searching for this type of activity pattern in mammalian O O brains 0 Distributed memory systems can store information than nondistributed systems and are more robust to loss of cells p1 0 Brenda Milner39s work with patient HM showed that the hippocampus was essential for storage of declarative longterm memories HM had an operation to treat intractable epilepsy removed the medial portion ofthe temporal lobes on both sides including the hippocam us H M had very specific memory deficits that are typical of amnesiacs inability to form Declarative memories could acquire procedural memories Retained prior knowledge Had short term memory Could not form longterm memories of events Could learn motor tasks Could perform some perceptual tasks such as cued recall and other forms of recall that involve priming Hippocampus is interconnected with much of cerebral cortex 0 Declarative memories appear to be stored in cortex 0 Case of NA shows importance ofthalamus for memory Circuit goes through thalamus to cortex Animal models of amnesia o difficulty in finding a task that would test declarative memory and not procedural memory 0 Allow more specific testing of hypotheses regarding pathways 0 Primates Delayed nonmatch to sample DNMS Requires recognition memory 0 Rats Radial arm maze Rats with hippocampal lesion learn to avoid arms of maze with no food but repeatedly go down arms after having taken food 0 Neurons in the hippocampus that are active only when the rat is in a certain location in its environment are called place cells 0 Human functional mapping studies T scan while navigating through virtual environment shows strong activation of the right hippocampus Studies on London Taxi drivers suggest a role for the hippocampus in spatial learning Striatum is involved in procedural learning habits Parkinson s patient have difficulty with lmplicit learning inferred relationships Dopamine neurons from the midbrain Ventral Tegmental Area project nucleus accumbens and frontal cortex 0 act as novelty detectors that may be important for learning and memory Prefrontal Cortex is involved with Working memory p2 Biol 6102 Neurobiology 111308 Mechanisms of Learning and Memory Chapter 25 What are the changes in the nervous system that underlie learning and memory Types of Learning 0 NonAssociative Habituation Decrement of response to repeated benign stimulus Sensitization Increase in responsiveness after noxious stimulus o Associative Classical Pavlovian Conditioning a learned relationship between two stimuli o A conditioned stimulus CS can predict the occurrence of an unconditioned stimulus US 0 Extinction occurs when the CS stimulus is no longer a good predictor ofthe US involves a modification ofthe response to the CS Example eyeblink conditionin Instrumental Conditioning Operant Conditioning a learned relationship between a stimulus and the animal39s own behavior involves a modification of the frequency and context Cellular mechanisms of learning in the mollusc Aplysia Habituation is correlated with a decrease in synaptic strength 0 Sensitization involves enhancement of synaptic transmission Due to serotonergic enhancement oftransmitter release Serotonin acts on a receptor that activates adenylyl cyclase Produces cAMP which activates CAMPdependent Protein Kinase PKA PKA has at least 3 actions it phosphorylates K channels and causes them to close 0 causing spike broadening o it phosphorylates Ca2 channels causing them to open more easily in response to voltage allowing more calcium to enter for each action potential 0 it directly enhances exocytosis through an unknown mechanism 0 Classical Conditioning uses the same cellular machinery as sensitization is light siphon stimulus US is tall shock Adenylyl cyclase produces more cAMP when Ca2 is elevated Thus Adenylyl cyclase acts as a coincidence detector of Sensory neuron activity and serotonin p1 Synaptic plasticity in the cerebellum 0 Three layers in cerebellar cortex Granule cell layer ten billion granule cells 0 axons form the parallel fibers and some Golgi cells Purkinje cell layer single layer of large Purkinje cell bodies Purkinje cells are GABAergic and are the only output of the cerebellar cortex Molecular layer axons of granule cells parallel fibers stellate and basket cells dendrites of Purkinje neurons 0 receives input from 200000 granule cells 0 each parallel fiber has a small effect on Purkinje cell 0 Inputs to Cerebellum ossy fibers arise from brain stem nuclei and spinocerebellar tract synapse on granule cells Climbing fibers arise from the inferior olivary nucleus in the medulla make strong excitatory synapses on a small number of Purkinje cells always excite purkinje cell 0 The parallel fibers that are active at the same time as the climbing fiber exhibit Long Term Depression LTD Climbing fiber activation causes strong depolarization and influx of Ca2 Parallel fibers activate metabotropic glutamate receptors which activate PKC The coincidence of Ca2 and PKC leads to a decrease in synaptic strength Studies of Hippocampal Long Term Potentiation LTP 0 Brain slice preparation A3 to CA1 synapse Tetanic stimulation of the Schaffer collaterals potentiates only those syna ses that were stimulated o LTP exhibits features of Hebbian plasticity The Associative properties of LTP are reminiscent of Associative Learning Exhibits cooperativel Due in large part to the properties ofthe NMDA receptor lnflux of Ca2 activates CaMKll Due to insertion of AMPA receptors into synapse and phosphorylation of existing AM PA receptors 0 Long Term Depression LTD counterbalances LTP lf synapses could only strengthen then it would eventually saturate Could be due to relative Ca2 sensitivity of kinases and phosphatases BCM Theory says that plasticity is bidirectional p2 Mechanisms for encoding longterm memory 0 Kinases are active for as long as the second messenger is present Can be modified to be permanently activated Memory will last until kinases are replaced in cell Autophosphorylation can lead to Ca2 independent activation of CaMKll molecular switch hypothesis 0 Protein synthesis can lead to more stable changes 0 Changes in Gene transcription can lead to more permanent storage Phosphorylation of transcription factors such as cAMP response element binding protein CREB can lead to upregulation of particular genes Can lead to structural changes at synapse p3
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