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Rutsuko Ito

lec05 overview 1. learning and memory systems a. early studies b. neural circuitry of action and habit 2. relevance to addiction a. neurochemical and neural evidence for aberrant control over behavior learning and memory systems 1. there are many neural systems that mediate different types of associative learning mechanisms 2. these operate in parallel but also associate with one another organization of learning and memory systems 1. learning -- acquisition of information 2. memory -- storing of information a. two types of memory i. short term memory ii. long term memory 1. further division into a. declarative / explicit memory i. episodic memory 1. autobiographical memory ii. semantic memory 1. your knowledge of the world 2. facts 3. the way things are b. non declarative / implicit memory i. procedural learning 1. habit learning 2. muscle memory ii. emotional memory key players in long term memory 1. dorsal striatum a. procedural learning 2. amygdala a. emotional learning 3. hippocampus a. declarative learning empirical evidence - early studies 1. parkard, hirsh, white / mcdonald, white a. three radial maze tasks manipulating for three types of long term memory i. procedural ii. emotional iii. declarative b. lesions respectively in i. dorsal striatum ii. lateral amygdala iii. hippocampus (fornix) 1. fornix consists of all the output (cell body) fibers that come from the hippocampus c. by means of electrolytic / excitotoxic lesions win-shift 1. single food pellet placed at the end of each arm 2. free roaming 3. collect all rewards without reentering the arm again 4. for successful performance  must use spatial cues (HIPPOCAMPAL LEARNING) a. hippocampal dependent task 5. results a. fornix lesion i. most amount of errors b. dorsal striatum lesion c. lateral amygdala lesion i. least amount of errors than control task win-stay 1. light stimulus that signals availability of reward (in 4 of 8 arms) 2. collects 8 pellets by entering each lit arm twice 3. successful performance  stimulus response learning task (DORSAL STRIATUM) 4. results a. fornix lesion i. least amount of errors compared to control b. dorsal striatum lesion i. most errors c. amygdala lesion i. less errors than control relevance of various neural pathways 1. perhaps a role of neural pathways in inhibiting one another 2. therefore lesion of one neural pathway may result in better functioning of another neural pathway conditioned cue preference 1. two arms a. one with many rewards b. one with no rewards 2. test day a. rats allowed to explore two arms freely (in extinction) b. preference of arm previously associated with reward  indicative of learning c. successful learning  cue-preference (EMOTIONAL LEARNING) 3. results a. amygdala i. did not acquire cue-preference b. fornix i. better performance compared to control condition critique of early studies 1. electrolytic lesions a. destruction of structures within radius of lesion b. i.e. it is not a clean lesion 2. fornix lesions instead of hippocampus proper lesions a. fornix contains nerve bundles of hippocampal otuputs b. but fornix and HPC lesions can have different effects on behavior i. is fornix involved in working memory or spatial processes? 1. or both? human evidence 1. caudate nucleus vs hippocampus systems a. what did she say about this? competition among memory systems 2. lesion of a competitive inhibitor system allows for better performance of other system 3. where is the competition implemented? a. focus on cortico-striatal loops b. knowing they operate in parallel  they must have to converge at some area of the brain i. is it in the cortex (upstream) or in the striatum (downstream) goal vs habit learning 1. action outcome vs stimulus response a. are they in competition with one another? 2. which area of the brain is important in mediating these systems? a. medial prefrontal cortex i. important role in regulating these types of learning 3. killcross and coutureau study a. lesions in areas before learning occurred i. targeting 1. prelimbic cortex 2. infralimbic cortex training 1. two contexts a. A b. B 2. two levers in each chamber a. high level of training i. context A  pressing left lever  food b. low level of training i. context B  pressing right lever  sucrose injection 3. devaluation a. prefeed with outcome 1 or 2 (food or sucrose) b. devalues the value of the reward 4. measure lever presses on left and right levers in extinction 5. results a. are they sensitive to devaluation? i. low training condition (short training) 1. under control of action-outcome learning 2. sham group a. sensitive to devaluation 3. prelimbic lesion a. does not respond to devaluation b. THEREFORE: under normal circumstances, prelimbic area is important for action outcome learning ii. high training condition (e
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