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Lecture 4b.docx

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PSYC 2800
Amanda Helleman

Lecture 4b [final] The Frontal Lobe and Short-Term Memory All sensory systems project to the frontal lobes There are a lot of inputs going into the frontal lobe but little coming out of lobe. Location of working memory. During tasks in which monkeys must keep information in short-term memory over a delay, certain cells in the frontal cortex will fire throughout the delay Animals that have not learned the task show no such cell activity Delayed response task- same location as cue Delayed-alternation task: diff location than cue Delayed-matching-to-sample task: same color As cue If we do single cell recording, where were actually measuring the firing of the cells in the frontal lobe what happens is that we get very specific cells that fire throughout the delayed period. It is almost like these cells are saying it is in the left, it is in the left, it is in the left or its the green one its the green on its the green one animals that have not learned this task show no cell activity when presented with it initially. Reciprocal Connections for Explicit Memory The neocortex projects to the entorhinal cortex, which projects back to the neocortex Benefits: Signals from the medial temporal regions back to the cortical sensory regions keep the sensory experience alive in the brain: the idea that the neural record outlasts the experience. So you may walk by someone hello you have their face and their name, that person leaves but your frontal lobe and cortical regions are keeping that person alive in your memory. Pathway back to the neocortex means it is kept apprised of the information being processed in medial temporal regions Korsakoffs Syndrome (explicit memory) remember diagram Indirect cause of chronic alcohol consumption; direct cause of malnutrition Alcohol is not what is killing off the brain cells, it is malnutrition Poor diet: Lack of vitamin B1 (thiamine) Without a good varied diet, you will lack critical vitamins like vitamin B1, we require it for normal neuronal processing, we dont make it in our body. Chronic alcoholism compromises thiamine absorption from GI tract, impairs thiamine storage May also result from dietary deficiencies, prolonged vomiting, or eating disorders Results in permanent loss of ability to learn new information (anterograde amnesia) and retrieve old information (retrograde amnesia) Show a great degree of confabulation lack the awareness that they actually have a memory deficit. They arent meaning to lie, they dont know they are lying because they actually dont remember what they did the night before for example but will say something habituary and when someone says but no I saw you here at the store, theyll further fabricate the story to compensate for not remembering but not knowing that they are lying. Explicit memory disturbances (some implicit though) Show damage to the mammillary body, and also to the medial thalamus and frontal lobes Proposed Neural Circuit for Explicit Memory **exam** Mishkin and colleagues (1982, 2000) Temporal Lobe Structures mammillary bodies are part of temporal lobe. 2 weeks from now, I will not remember what I wore yesterday and what my daughter had for breakfast. Frontal Lobe Structures (short term and ordering Medial Thalamus Basal Forebrain-Activating Systems **Circuitry: we get info via our senses, it is projected via the neocortex to these temporal lobe structures. It is then passed onto prefrontal cortex and medial thalamus. Basal forebrain is critical because it keeps the activity in forebrain high. So those basal forebrain neurons that secrete things like aceylcholine, serotonin theyre sending projections up to the forebrain ad saying pay attention, pay attention, pay attention .. the frontal cortex is critical for short term (explicit) memory and order of explicit events. So not just keeping things in your mind, but also the order. Finally, temporal lobe is more critical for long term memory, but we have explicit memory in both frontal and temporal. ^^^^***** exam ***** ^^^^ Proposed Circuit for Implicit Memory Mishkin and colleagues (1982, 1997) Basal Ganglia Ventral Thalamus Substantia Nigra Premotor Cortex Circuitry: we get info once again from our senses. Goes to neocortex once again, but then goes to basal ganglia. the neurons use dopamine as their signaling molecule and those are found in the substantia nigra. So the basal ganglia is kept active by the dopamine neurgic cell of the substantia nigra, in order to actually make those implicit memoriesexpressed, they need to be sent to the Ventral thalamus. SO REMEMBER medial is explicit whereas ventral is implicit. It is then sent to the premotor cortex which is essential in acting out motor programs, implicit is memory for HOW. How do you ride a bike, how do you dial a phone. So it makes sense that we are going to involve those motor regions. Another major difference in the two, is that with explicit we have a lot of connections going back to temporal lobe whereas implicit does not. Unconscious nature of implicit memory Mishkin believes that implicit memories are unconscious because the connections between the basal ganglia and cortex are unidirectional Basal ganglia receives information from the cortex, but does not project back to the cortex For memories to be conscious, there must be feedback to the cortex Medial temporal lobe projects back to the cortex so explicit memories are therefore conscious Why are implicit memories unconscious? **exam** Because the neocortex sends into the basal ganglia but does not receive information back.**** Neural Circuit for Emotional Memories - Memory for the affective properties of stimuli or events - Could be implicit or explicit - Amygdala is critical for emotional memory Damage to the amygdala abolishes emotional memory but has little effect on implicit or explicit memory and
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