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COGS 107B Final
Terms in this set (85)
- 2 different neurons have action potentials within a short-time window relative to each other.
- The synapse between the two neurons is created or strengthened.
- The way we learn through neurons co-firing and synchronizing together.
Synaptic Efficacy (strength)
- The capacity of a presynaptic input to influence the postsynaptic output.
Changes in Synaptic Efficacy
- Changes in the amount of depolarization in a postsynaptic neuron - potentiation or depotentiation.
- An increase in synaptic efficacy.
- A decrease in synaptic efficacy.
What Causes Changes In Synaptic Efficacy?
- Changes in the amount of NT (presynaptic).
- Changes in the shape of the synapse (postsynaptic)
- Changes in the number of iontropic receptors (postsynaptic).
- Changes in the kinetics of inotropic receptors (postsynaptic).
- Development or retraction of contacts between neurons (postsynaptic).
- Long, skinny shape that increases the internal resistance of the spine.
- Harder for EPSP's to travel through these.
- Shorter and wider and contribute to decreased internal resistance.
Fragile X Mutation
- Mutation of fmr gene on X chromosome found in 35% of intellectually disabled individuals.
- Responsible for shutting off production mGluR receptors.
- Makes fmr protein which inhibits mGluR.
- Activation of these receptors causes production of new immature dendritic spines.
- FMR gene doesn't make FMR protein, so mGluR is disinhibited, so more mGluR are produced. mGluR produces a biochemical cascade that leads to the production of immature spines.
- Technique to induce changes in synaptic efficacy.
- Stimulate presynaptic neuron once -> no AP firing in post.
- Stimulate Presynaptic neuron with a burst of activity -> postsynaptic neuron fires repeatedly.
- Stimulating just once -> leads to AP in post.
- Can also be stimulated from post and recorded from pre, -> leads to decreased synaptic efficacy.
Spike Timing Dependent Plasticity
- Changes in synaptic 'efficacy' between two neurons related to the relative timing of their AP's.
- A rule stating that changes in synaptic efficacy between two neurons is related to the timing of their AP's relative to each other.
- Regulate synaptic change and can be changed by Neuromodulators.
New Findings of STDP
- Ach in combination with burst pairing, results in depression.
- After burst pairing with Ach, adding DA leads to potentiation.
- Ca2+ Transient causes potentiation over longer time.
- Globally scales down all synapses.
- Potentiation can cause too much excitation.
- Signaling no longer corresponds to signaling variables.
- Associative Memory.
- Implicit/Procedural memory.
- Episodic/Declarative explicit memory.
- Working Memory.
- Pavlovian Fear Conditioning -> Association of an initially neutral tone (CS) with a foot-shock results in 'freezing' responses when the tone alone is played.
- Memories are 'labile' their recall makes them vulnerable to erasure or consolidation.
Implicit/Procedural Learning 1
- Rat reach-to-grasp as a model of motor skill learning - more is better and Ach helps.
Implicit/Procedural Learning 2
- Perceptual skill learning - 'more is better' and Ach helps.
Implicit/Procedural Learning 3
- Basal Ganglia versus HPC - an Act-Based competition.
- Hippocampal cell activity in a 'place' often depends on the places previously or subsequently visited.
- Holding items in memory is achieved (7+/-2) through interaction of the PFC and Parietal Cortex.
Premotor Cortex Idea 1
- Activity, as in the primary cortex, may directly reflect action.
Premotor Cortex Idea 2
- Activity accompanies actions as well as planning for actions.
Premotor Cortex Idea 3
- Action-Related activity may depend on ordering of actions in a sequence.
Premotor Cortex Idea 41
- Activity may reflect perceived actions as opposed to actual movements.
Abstract Firing Properties of A Motor Task 1
- Dorsolateral PFC neurons mark the beginning and ending of a behavioral episode.
Abstract Firing Properties of A Motor Task 2
- Dorsolateral PFC neurons track time intervals.
Abstract Firing Properties of A Motor Task 3
- Dorsolateral PFC neurons "count."
Abstract Firing Properties of A Motor Task 4
- Dorsolateral PFC neurons map action sequence categories.
Top-Down Influence Pathways
- 1. Direct Projections.
- 2. Projections to Neuromodulatory system.
- 3. Projections to Thalamus.
Top-Down Influences on Parietal
- Inactivation of PFC via cooling depresses the 'working memory' responses of parietal cortex neurons and increases errors.
Attention As A 'Selection' Process
- Responses of neurons in IT cortex, to their preferred stimuli are strongly modulated by attention.
- Patterns of activity occurring over many neurons.
Alpha Motor Neurons in Spinal Cord
- Located in the ventral horn of spinal cord.
- Receive info from Motor Cortex.
- Alpha motor neurons form endplates on muscle fibers where excitation leads to Ach release.
- Ach binds to ionotropic nicotinic receptors.
- Myosin and Actin cause muscles to contract.
Alpha Motor Neurons
- Projects to a single muscle but within that muscle, it will synapse on many motor fibers of the same type.
- 50ms to peak force.
- Small force.
- Non-fatiguing (aerobic)
- Useful for tonic movements, maintaining posture.
- 25 ms to peak force.
- Large force.
- Fatigue easily (glycolysis)
- Useful for quick, powerful movements. Jerk movements.
- Activation/Inactivation patterns of muscles at any given time.
- Analogous to the pop. code -> If you look at what muscles are active or inactive, you might be able to tell what action an individual is expecting.
- Motor Cortex output.
- Action that are volitional.
- Receives output from cerebellum.
- Cerebellar reflexes.
- These neurons contribute to rudimentary act or fixed action patterns.
- Reticular formation in Brainstem.
- Reflexive actions.
- No cortical engagement.
- Associated with the Red Nuc. of Tegmentum.
- Fixed action patterns.
- Mesencephalic locomotor regions.
Fixed Action Pattern
- Common, repeatedly utilized behaviors are controlled by central pattern generators.
- Circuits in brainstem that have genetic prewiring.
- Ex: walking, chewing, withdrawing from flame.
Properties of Spinal Cord Interneurons
- 1. Excitatory or Inhibitory.
- 2. Interconnected with themselves and motor interneurons.
- 3. May have axons that cross the commissure and/or extend into other outer segments.
- 4. Receive both converging and diverging motor cortes inputs.
Divergence of Corticospinal Neurons
- A single motor cortex neuron projects to the ventral horn of spinal cord and contacts many different motor neurons that control different muscles.
Convergence of Corticospinal Neurons
- Neighboring regions of motor cortex project down and converge onto single spinal cord motor neurons.
Controlling the Controller
- Premotor cortex drives activity patterns in motor cortex and is, in turn, driven by both prefrontal and parietal cortices.
Neurons In Premotor Cortex 1
- Premotor cortex in navigating rats exhibit more abstract relationships to actions.
Sequence-Dependent Action Mapping
- This neuron fires after the last turn if its a right.
- This neurons fires during forward locomotion preceding right turns.
- This neuron fires during the execution of any right turn.
Neurons in Premotor Cortex 2
- Activity may reflect the position of an action in an action sequence.
Neurons in Premotor Cortex 3
- Mirror Cells: Fire when you observe, hear, or execute an action.
Premotor Cortex - A More Indirect Role In Motor Control
- 1. Activity, as in primary motor cortex, may directly reflect present action.
- 2. Activity accompanies actions as well as planning for actions.
- 3. Action-related activity may depend on ordering of actions in a sequence.
- 4. Activity may reflect perceived actions as opposed to actual movements.
- Fires to more abstract features of a task.
- Beginning and end of behavioral episodes.
- Time intervals.
- Extract action sequence categories.
Cue + Delay Properties
- Burst when cue comes on and then sustained activity.
- Info about how long it has been.
Delay + Action Properties
- Increasing activity until the animal releases the key.
- Info to motor areas to release key.
- There are neurons in the PFC that are tuned to a particular number of objects.
Central Pattern Generator
- Common, repeatedly utilized behaviors such as walking, chewing, withdrawal imply the workings of this.
- involves the selection of muscle synergies by several different systems.
- Circ-mean of all values and shows degree of preference.
- The longer the arrow, the stronger the bias.
- The primary motor cortex doesn't activate specific muscles but tells the spinal cord "I want to move in that direction at that speed. The neurons can figure out the specifics themselves."
Nitz & Others
- Primary motor cortex creates specific muscle synergies: I want "these muscles to be activated and not these."
- Pathlets = focused on trajectories, not the specific muscles, not the direction nor the velocity, but the pathway involved.
- Monkey mirror neurons fire the same way when watching someone pick up a grape as when they pick up the grape themselves.
- Monkey picks up a peanut and cracks it open. Watches cracking open up peanut, neuron fires. Can't hear it but sees it = still fires and vice versa.
- Concept = Action.
- Reaches for block. If block is not there but the experimenter still makes the reaching movement, the neuron won't fire. If action is covered but the monkey knows the block is still there the neuron will fire.
- These go to specific areas.
- sends things to multiple areas, this way it is able to integrate info all at once to get a holistic understanding of a thing.
- How learning happens in the brain.
- Conducted similar works as Hebb but a year prior.
Flowers for Algernon/Charly
- A drug that makes both the rat and Charly intelligent.
Pop. Firing Rate Vector
- A list of firing rates for a large set of motor cortex neurons.
Retrospective and Prospective
- Two forms of spatial position coding.
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