2/19/15 – Lecture 11 – Learning and Longer-Term Synaptic Plasticity- Goal: to learn how changes in synaptic transmission and synapse number contribute to consolidation and storage of memory- Ways our Brains Changeo Habituation: temporary changes in the strength of synaptic transmission that doesn’t require newgene expression (usually decreases sensitivity to stimuli)o Changes that require new gene expression: turning genes on to produce proteins (changes can increase or decrease the result) Longer term changes in the strength of synaptic transmission at an existing synapse Changes in the number of synaptic connections between neurons Changes in the number of neuronso Short term Memory: lasts minutes to hours or even days, repetition seems to increase the strength/ duration of short term memory Ex: studying for each bio psych exam, know it for 3-4 weeks, after that we forget a majority of ito Long Term Potentiation (LTP): a longer-lasting increase in the strength of the synaptic connection and the size of the post-synaptic potential required new gene expression in response to repeated activation of synapse  Repeated synaptic transmission tends to increase the stability of memory INVOLVED WITH SHORT TERM MEMORY!!! Not long term memory- Class experiment: see how well we memorize 2 numbers, one shown only once and the other shown many times 136472o Late LTP: longer-term memory and long-term increases (or decreases) in synaptic transmission In response to repeated activation, a cascade of signals in the post-synaptic neuron is activated by elevated Ca2+ levels- Trying to make the post synaptic neuron more sensitive to the action potentials sent by the presynaptic neuron, exert less energy- A general rise of Ca2+ levels eventually reaches a point where it activates signaling proteins, these then turn on NT receptor genes which then turn on NT receptor that is carrying mRNAo The new neurotransmitter receptors are added to the dendritic membrane or the post synaptic neuron More neurotransmitter receptors means more binding, more ion channel opening, and a much greater Post Synaptic Potential size Late LTP lasts longer than habituation, usually hours or days or even months- Takes longer to create the change, to turn on genes, to create proteins, and so it takes longer to forget By changing the strength of synaptic transmission b increasing the responsiveness of the post-synaptic cell, we change the behavior of these neurons The LEARNING in this case involves increased likelihood of firing of neurons in the prefrontal and medial temporal cortex associated with the knowledge we are trying to learn and the MEMORY of this is “stored” in the greater number of neurotransmitter receptors and greater responsiveness of the post-synaptic neurons- the more often we activate these neurons, the more we maintain this increased synaptic transmission and the more likely we will be to remember the information for longer- if we stop activating these neurons, over time the number of receptors may decrease and the post-synaptic neuron well respond normally to a new stimuli and we will “forget” it  The opposite of LTP can occur too: Long Term Depression is a smaller than normal response to the same stimuluso Long-Term Memory: new synapse formation and neurogenesis, lasts days to decades Ex: personal memories, facts you learn in school, how to ride a bike/read/write/type, etc Longer term memory involves much larger and longer acting changes in synaptic communication between neurons requiring new gene expression- 2 main ways to increase synaptic number in long term memoryo Synaptogenesis: new synapse formation, can happen through out the brain and Nervous system Post synaptic cells initiates signaling pathways that activate gene expression to produce new dendritic spines- Post synaptic cell may release factors that encourage branching and growth of pre synaptic neuron axon Requires extensive gene expression (needs 100s of genes and proteins to create new synapse)- Provides greater/stronger input to the post synaptic neuron- Change is much longer lasting than habituation or LTPo Neurogenesis: new neuron formation, which can then form new synapses Occurs only in the hippocampus (or in the olfactory bulb that is responsible for smell)- Requires extensive gene expression (1000s of gene activations and proteins) and stem cell division- Increases number of neurons available for synapse formation- MUCH longer lasting than habituation or LTP- Defects in Memoryo Amnesia: the loss of memory Types of Amnesia- Retrograde Amnesia: the loss of pre-existing memories… defect in storage or retrieval of memories- Anterograde Amnesia: inability to form new memories… defect in encoding and or consolidation of memories (the movie “Memento”)o Either way, explicit or implicit memory can be affected Causes of explicit memory amnesia- Physical trauma- Alzheimer’s Disease: neurodegenerative disorder associated with old age where neurons die and memory is affected- Korsakoff’s syndrome: caused by sever chronic alcoholism, alcohol consumption causes deficiencies in nutrients (niocine)- Psychological trauma Causes of implicit memory amnesia- Parkinson’s disease: motor disorder where it’s difficult to move voluntary or involuntary, inability to access or create motor memories- Huntington’s Disease: neurodegenerative disease that affects motor behavior and ability to access motor memories- Physical trauma to the Basal Ganglia or