BRAIN PLASTICITY Neuroplasticity: _________________________. Happens in at least 3 ways: - ________________________________________ __________________ - ______________________________ - ________________________________________ Recently, it was found that “new” neurons and glial cells are born _____________ in specific brain regions - reorganization. Brain plasticity occurs during: - _______________ - _______________________ - ______________________________ DEVELOPMENT OF NERVOUS SYSTEM: 1. Neural proliferation (neurogenesis - neuronal “birth”) 2. Migration and differentiation (neural cell precursors travel “home” and “grow up”) 3. Axon growth and synapse formation (growth cones and filopodia) 4. Neuron death and synaptic pruning: too many neurons and synapses produced - competition for neurotrophic factors (ex., NGF - ___________________) Examples of the effects of EXPERIENCE on NEURAL DEVELOPMENT and PLASTICITY Early visual experience - studies of early __________________________ found deprived eye to ______ ability to activate visual cortex - only occurs if other eye is open, not if it is also deprived - ____________________ - these are structural effects - ________________ - concept of _______________________________ Two eyes open One eye shut Environment and the cortex - studies of rat litters separated at birth into _______________________________________ - enriched environments produces: - ________________ - ______________________ - __________________ - more glial cells; - larger postsynaptic zones; - larger protein content. - some of these effects can be produced in adult animals by giving them extensive maze training LEARNING AND MEMORY Learning: ________________________________ _________________________________________ _________________________________________ ________________________________ Memory: _________________________________ability to recall or recognize previous ________________________________________experience in the form of behavioral change. If behavior at a later time B is different than at earlier time A, say that learning has taken place between time A and B TYPES OF LEARNING: NON-ASSOCIATIVE LEARNING: _________ _______________________________________ ________________________ A. Habituation: __________________________ ______________________________________ __________ B. Sensitization: __________________________ _______________________________________ ___________ Marine snail “Aplysia Californica” Tail Head Gill-withdrawal reflex used to study habituation and sensitization (Eric Kandel’s laboratory) Habituation - touch siphon repeatedly every 30 sec leads to short-term habituation of gill-withdrawal reflex - can lead to long___________________-term habituation if touch is repeated over days Sensitization - one electric shock to the tail can lead to short- term sensitization of gill-withdrawal reflex - several electric shocks can lead to sensitization that will be observed for weeks (long-term) ASSOCIATIVE LEARNING: _______________ _________________________________________ _______________ A. Classical conditioning (also called Pavlovian_________ conditioning____________): the__________________________ process by which a neutral stimulus________________________________________ acquires meaning through associations with___________________ another stimulus (often a biologically relevant stimulus) Terminology UCS = ____________________ (food, water, etc.) UCR = _____________________ (salivation, etc.) Examples: UCS - - - - - - - - - - - > UCR pinprick withdrawal food salivation sudden loud noise startle airpuff eyeblink CS = ________________________ (bell, light, etc.) CR = _____________________ (salivation to bell) so CR is the ____________ response Development of Classical Conditioning Example: conditioning of emotional responses - Pavlov’s dog) UCS - - - - - - - - - - - - - > UCR (food) (salivation) Initially CS - - - - - - - - - - > no response (bell - neutral stimulus) Repeated pairings of CS + UCS - - - - - - > UCR (bell) + (food) (salivation) Bell eventually comes to elicit salivation without the presentation of food CS - - - - - - - - - - - - - - - - > CR (bell) (salivation) Note that salivation here is called conditioned response (CR) because it is not elicited directly by food; classical conditioning has taken place Also conditioning of motor responses - example of eye blink conditioning CLASSICAL CONDITIONING: NEURAL BASIS Classical conditioning of emotional responses (freezing in rats - changes in heart rate/blood pressure or skin conductance in humans) is learned after only a few pairings Electric shocks produce “freezing” in rats and changes in heart rate/skin conductance in humans Repeatedly pair auditory stimulus (CS) with shocks (UCS). - the auditory CS come to elicit freezing and changes in heart rate/skin conductances - the ________________________ to produce classical conditioning of emotional responses Classical conditioning of motor responses, such as eyeblink in response to puffs of air is learned only after 100s of pairings of an auditory stimulus with puffs of air - the _______________ is necessary to produce classical conditioning of motor responses B. Instrumental Conditioning (also called _______ ______________): _________________________ ________________________________________ __________________________________ Terminology: Discriminative stimulus (SD): _______________cue that triggers the ___________________________________motor response (ex. sight of a lever bar). Favorable outcome: positive________________________ reinforcers (ex. food, __________________________________________water, etc) or termination of negative reinforcers _____________________________(termination of pain, isolation, etc). Example of instrumental conditioning: Cats have to learn to press a lever in order to obtain palatable food (Thorndike’s experiment) Neural Basis of Instrumental Conditioning: - _____________________________ necessary for instrumental motor response learning - ________________________________________ _______ necessary for “detection” of reinforcer. HUMAN MEMORY The various stages of memory: I. _______________Sensory registers (high capacity, low duration) With Attention - II. Short_________________-term memory (low capacity & duration) With Consolidation - III. Long________________-term memory (high capacity & duration) Retrieval - recall and recognition Implicit memory (similar to _________________): __________________________________________ ___________________________ Examples: - mirror drawing tasks - playing video games - riding a bicycle - word associates (define fall after different stories) Explicit memory (similar to _________________): ________________________________ Two types - _______________ (time and places) - _________ (facts and knowledge) NEUROBIOLOGICAL BASES OF MEMORY Karl Lashley (1920’s - 1950’s) and the search for the “engram” or memory trace: _________ __________________ He derived two principles from his studies: - ______________________= memories stored diffusely all over neocortex - _______________________= neocortex all over the brain plays an equal role in memory storage What was wrong with these interpretations? - task difficulty; - different “learning” systems/strategy used to solve problems. Donald Hebb (early 1950’s) and ______________ of short-term memories into long-term memories via ________________________________ - cell assemblies: ________________________ - reverberation: __________________________ _______________________________ ____________ LESSONS FROM HUMAN AMNESIAS Amnesia: _________________ Retrograde amnesia: forget events _______ brain trauma Anterograde amnesia: forget events _____ brain trauma The beginnings of Explicit Memory mechanisms Case of H.M.: ____________________________ ______________ because of severe epilepsy (removal of enthorinal and perirhinal cortex, part of amygdala and most of hippocampus) H.M. experienced: 1. No loss of intelligence (IQ) 2. Mild retrograde amnesia 3. Devastating anterograde amnesia What we learned from H.M.: 1. Supports________________________________________ short- & long-term memory processes 2. Existence____________________________________ of explicit vs. implicit memory 3. Existence________________________________ of consolidation process 4. Challenges_____________________________________ view of diffuse memory process 5. Implicates_______________________________________ discrete brain regions in memory Implicit memories: various forms of implicit knowledge. Amygdala: _______________________________ Cerebellum: _______________________________ Basal ganglia: _____________________________ __________________________.