Bio35 Lecture 24 Synaptic Plasticity 2024 PDF

Today’s learning objectives (Wrap-up from previous lecture) Describe how the motor cortex reorganizes when trained with a particular motor task. (Wrap-up from previous lecture) Provide an example of lost brain function due to experience-dependent loss. Define synaptic plasticity. Compare...

Today’s learning objectives (Wrap-up from previous lecture) Describe how the motor cortex reorganizes when trained with a particular motor task. (Wrap-up from previous lecture) Provide an example of lost brain function due to experience-dependent loss. Define synaptic plasticity. Compare and contrast AMPA receptors and NMDA receptors and draw implications to synaptic plasticity. Provide an example from synaptic plasticity studies which distinguishes sufficiency from necessity. Draw a postsynaptic recording which shows synaptic plasticity or long-term potentiation. Describe how number of postsynaptic receptors, dendritic spine volume, and number of synapses change with increased or decreased synaptic transmission. BASED ON THE REORGANIZTION OF THE MOTOR CORTEX, WHAT COULD THE “SKILLED REACHING TASK” HAVE BEEN? A) WRIGGLING TOES WHILE ROTATING WRISTS B) USING ELBOWS AND SHOULDERS IN A CHICKEN DANCE C) HANGING FROM A TREE FROM HIS TAIL WHILE THROWING BANANAS D) KEEPING TOES COMPLETELY STILL SPECIFIC BRAIN REGIONS EXPAND WHEN WE USE THEM MORE, BUT BRAIN REGIONS CAN ALSO SHRINK WHEN WE DON’T USE THEM EXPERIENCE-DEPENDENT PLASTICITY: LOSE WHAT YOU DON’T USE Homunculus in somatosensory cortex EXPERIENCE-DEPENDENT PLASTICITY: LOSE WHAT YOU DON’T USE Amputate digit 3 Homunculus in somatosensory cortex loses representation of digit 3 THE BRAIN THAT CHANGES ITSELF LET’S GET DOWN TO THE POINT!: SYNAPTIC PLASTICITY EXPERIENCE DEPENDENT PLASTICITY Action potential within a neuron Synaptic transmission between neurons Action potential within a neuron  Synaptic transmission between neurons SYNAPTIC PLASTICITY: THE ABILITY OF A SYNAPSE TO STRENGTHEN (OR WEAKEN) OVER TIME, DEPENDING ON ITS ACTIVITY (OR LACK OF) stimulate Synaptic transmission between neurons NORMAL SYNAPTIC TRANSMISSION Postsynaptic Postsynaptic response response the 1st time the 2nd time stimulate Synaptic transmission between neurons SYNAPTIC PLASTICITY Postsynaptic Postsynaptic response response the 1st time the 2nd time DRAW A SYNAPSE. WHO ARE THE PLAYERS INVOLVED? Where are vesicles? Receptors? HOW COULD THESE PLAYERS ACT DIFFERENTLY TO ENHANCE SYNAPTIC TRANSMISSION? THE ANATOMY OF A CHEMICAL SYNAPSE Presynaptic cell neurotransmitter Postsynaptic cell Postsynaptic receptors WHAT WOULD INCREASING THE NUMBER OF POSTSYNAPTIC RECEPTORS DO TO THE POSTSYNAPTIC RESPONSE? A) INCREASE POSTSYNAPTIC RESPONSE B) NO CHANGE C) DECREASE POSTSYNAPTIC RESPONSE At excitatory synapses, AMPA receptors and NMDA receptors are two main types of postsynaptic glutamate receptors AMPA receptors NMDA receptors Open when Open when glutamate binds. glutamate binds AND the postsynaptic When open, neuron is already cations flow in. depolarized. Because a Mg+ plug needs to be dislodged IF YOU COULD ONLY MAKE ONE CHANGE AT A GLUTAMATERGIC SYNAPSE, HOW WOULD YOU CHANGE THE POSTSYNAPTIC RECEPTORS TO ENSURE YOU INCREASE POSTSYNAPTIC RESPONSE? A) INCREASE THE NUMBER OF AMPA RECEPTORS B) INCREASE THE NUMBER OF NMDA RECEPTORS C) INCREASE THE RATIO OF NMDA:AMPA RECEPTORS  ENHANCED SYNAPTIC TRANSMISSION stimulate Synaptic transmission between neurons Postsynaptic Postsynaptic SYNAPTIC PLASTICITY response response the 1st time the 2nd time A SPECIAL TYPE OF SYNAPTIC PLASTICITY: LONG-TERM POTENTIATION EXAMPLE DATA Sustained LTP When LTP is not sustained WHAT DOES THE DATA BELOW TELL YOU ABOUT WHAT IS IMPORTANT FOR SUSTAINED LONG-TERM POTENTIATION? A) PROTEIN SYNTHESIS BLOCKADE IS SUFFICIENT FOR LTP. B) PROTEIN SYNTHESIS BLOCKADE IS REQUIRED FOR LTP. C) PROTEIN SYNTHESIS IS SUFFICIENT FOR LTP. D) PROTEIN SYNTHESIS IS REQUIRED FOR LTP. FOR EXAMPLE, PROTEIN SYNTHESIS OF AMPA RECEPTORS (A TYPE OF PROTEIN) WILL ALLOW SUSTAINED ENHANCEMENT OF SYNAPTIC PLASTICITY. ENHANCED SYNAPTIC TRANSMISSION SYNAPTIC PLASTICITY BIGGER SYNAPSES MORE SYNAPSES SYNAPTIC PLASTICITY TO PRUNE UNUSED BRAIN CIRCUITS SPECIFIC BRAIN REGIONS EXPAND WHEN WE USE THEM MORE, BUT BRAIN REGIONS CAN ALSO SHRINK WHEN WE DON’T USE THEM  SYNAPSES EXPAND WHEN WE USE THEM MORE, BUT SYNAPSES CAN ALSO SHRINK WHEN WE DON’T USE THEM  What activities do you not do anymore? Your brain will reorganize so that it reduces its capacity to do those tasks.  What do you want to improve in? What do you want people to say about you at the end of your life? How will you use your brain so that that dream becomes true? What will you practice?