Studied by 21 people
Lower Motor Neurons
Sends axons out of the brainstem and spinal cord to innervate the skeletal muscles of the head and body
Where do LMNs in the brainstem send axons to?
Head muscles
Where do LMNs in the spinal cord send axons to?
The rest of the body
Where does sensory information go?
Dorsal/afferent root
Where does motor information go?
Ventral/efferent root
What do motor neurons release into the muscles?
Acetylcholine (ACh)
What type of movement do muscles generate?
Unidirectional
How are muscle pairs arranged?
With extensors and flexors (antagonistic pairs)
What does the Central Pattern Generators cat tell us?
All of the neurons that control walking are in the spinal cord instead of the brain for faster processing. Walking can still work even in dead animals because it is independent of the brain.
Upper Motor Neurons
Somas originate in the brainstem/cerebral cortex and axons descend to synapse with local circuit neurons/LMNs
Tectospinal tract
UMN that controls neck musculature and generates head/eye movements
Rubrospinal tract
UMN that controls arm musculature
Reticulospinal tract
UMN that controls temporal and spatial coordiation of movement, cardiovascular, and respiratory systems
Vestibulospinal tract
UMN that controls balance/posture, axial muscles, antigravity muscles, and eye fixation during body movement
Cerebral cortex projections
Cerebral cortex, upper medulla, lower medulla, and spinal cord
Three regions of motor cortices
Primary motor cortex
Supplementary motor area
Premotor cortex
Supplementary motor area
Plans movements
Premotor cortex
Plans and controls limb movements
Primary motor cortex
Controls voluntary movement of contralateral side of body
Topographic organization
Betz cells
Betz cells
Large pyramidal cells that project to spinal cord
Firing rate (Hz)
# of APs / time
What did the monkey experiment show us?
There are neurons that are tuned to specific movements, like arm movements to the left
Muscle receptors
Golgi tendon organs
Muscle spindle receptors
Golgi tendon organs
Senses tension
Muscle spindle receptors
Primary sensory endings
Secondary sensory endings
Muscle spindle receptors: Primary sensory endings
Innervates the central region of the muscle spindle
Senses stretch
Muscle spindle receptors: Secondary sensory endings
Innervates the thin ends of the muscle spindle
Senses speed of stretch
Individual muscle fibers are innervated by…
A single motor neuron
Cerebellum
Basic limb and eye coordination
Balance
Muscle tone
3 cerebellum components
Vermis & anterior lobe
Posterior lobe
Flocculonodular lobe
Vermis & anterior lobe
Motor coordination
Limb control
Posterior lobe
Initiation/planning
Timing
Flocculonodular lobe
Vestibular control
What are the major inputs of the cerebellum?
Motor and premotor cortex (relay in pontine nuclei)
How many somatotopic maps does the cerebellum have?
At least 2
Three layers of cerebellar cortex
Molecular layer
Purkinje cell layer
Granular layer
Molecular layer
Dendrites of Purkinje cells
Stellate and basket interneuron cells
Purkinje layer
Purkinje cell bodies
Granular layer
Granule cell bodies
Golgi interneuron cells
In terms of signals, Purkinje cells are…
GABAergic
Are Purkinje cell somas in the same place as the dendrites?
No
Are Granule cell somas in the same place as the dendrites in the granule layer?
Yes
In terms of signals, Granule cells are…
Glutamatergic
What shape do the Granule cell axons take in the molecular layer?
T
2 inputs to the cerebellar cortex
Climbing fibers
Mossy fibers
Climbing fibers
From Inferior Olive (Brainstem)
Glutamatergic
Synapse on 1-10 Purkinje cell dendrites
Mossy fibers
From Pontine nuclei (Brainstem)
Glutamatergic
Corticopontocerebellar pathway
Corticopontocerebellar pathway
Cerebral cortex → pontine nucleus → cerebellum
Output from the cerebellar cortex
Purkinje cells (deep cerebellar nuclei → thalamus → cerebral cortex)
Anatomical loop
Cerebellar cortex
Pontine nucleus
Cerebellum
Deep cerebellar nuclei
Thalamus
Cerebral cortex
What results from cerebellar damage?
Balance/gait problems, error in range and force of movement, inability to rapidly stop limbs
Basal ganglia
Group of interconnected subcortical brain structures
Rodent basal ganglia
Combined into striatum
Primate basal ganglia
Separated into caudate and putamen
Projections from cortex to striatum
Pyramidal tract (PT) neurons
Intertelencephalic (IT) neurons
Pyramidal tract (PT) neurons
Upper motor neurons that project to brainstem and spinal cord
Intertelencephalic (IT) neurons
Motor cortex neurons that DON’T project to brainstem and spinal cord
Direct pathway neurons send axons to…
Globus Pallidus internal segment (GPi) and Substantia Nigra pars reticulata (SNR)
GPi & SNR → thalamus
Indirect pathway neurons send axons to…
Globus Pallidus external segment (GPe)
GPe —> subthalamic nucleus (STN)
STN → GPi & SNR
GPi & SNR → thalamus
After the direct/indirect pathway is taken, where is information sent?
GPi & SNR send axons to thalamus
Thalamus projects back to cerebral cortex
(Cortico-striatal loop)
What happens if you increase the activity of a Glutamate (GLU) neuron?
Causes EPSP and more APs in postsynaptic neuron
What happens if you decrease the activity of a Glutamate (GLU) neuron?
Causes EPSP but less APs in postsynaptic neuron
What happens if you increase the activity of a GABA neuron?
Causes IPSP and less APs in postsynaptic neuron
What happens if you decrease the activity of a GABA neuron?
Causes IPSP but more APs in postsynaptic neuron
D1 in the striatum is…
Excitatory
D2 in the striatum is…
inhibitory
Direct pathway steps
Cerebral cortex (GLU) → striatum (GABA) → GPi & SNR (GABA) → thalamus (GLU) → cerebral cortex
Indirect pathway steps
Cerebral cortex (GLU) → striatum (GABA) → GPe (GABA) → subthalamic nuclei (GLU) → GPi & SNR (GABA) → thalamus (GLU) → cerebral cortex
Learning
Process by which experience results in changes in behavior
Memory
Internal record of past experiences acquired through learning
Habituation
A decrease in the strength or occurrence of a behavior after repeated exposure to the stimulus that produces that behavior
What happens to a rat that is continuously exposed to a loud, startling stimulus?
The rat’s response becomes weaker with every loud stimulus (habituated)
Acoustic Startle Reflex
Defensive response (e.g. jumping/freezing) to a startling stimulus (e.g. a loud noise)
Orienting Response
An organism’s innate reaction to a novel stimulus
Stimulus Specificity
Habituation to one event doesn’t cause habituation to every other stimulus in the same sensory modality
Stimulus Specificity example
Being habituated to a checkboard pattern doesn’t mean you’ll be habituated to a bright rainbow pattern
Factors influencing the rate and duration of habituation
How arousing the stimulus is
The number of times it is experienced
The length of time between repeated exposures
How arousing the stimulus is…
Less arousing = faster habituation
The number of times a stimulus is experienced…
Greater # of presentations = more habituation
The length of time between repeated exposures of a stimulus…
Closely spaced repetitions = massed (faster habituation)
Spread out over time = spaced (longer duration habituation)
Sensitization
Phenomenon in which an arousing stimulus leads to stronger responses to a later stimulus
Not stimulus speific
Fewer presentations of stimuli required than for habituation
Non-associative learning
Habituation
Sensitization
Associative learning
Classical conditioning
Operant conditioning
Classical (Pavlovian) conditioning
A form of learning in which the organism acquires the expectation that a given stimulus predicts a specific upcoming important event
Unconditioned stimulus (US)
A cue that has some biological significance that naturally evokes a response
Unconditioned response (UR)
The naturally occurring response to an unconditioned stimulus (US)
Neutral stimulus (NS)
Does not elicit the UR, but is paired with UC to cause the conditioned response (CR)
Conditioned stimulus (CS)
A cue that has been paired with an unconditioned stimulus (US) and elicits a conditioned response (CR)
Conditioned response (CR)
Trained response to a conditioned stimulus (CS) in anticipation of the unconditioned stimulus (US)
Operant/Instrumental conditioning
Organism learns to make a response in order to obtain or avoid important consequences
Cognitive map
An internal psychological representation of the spatial layout of the external world
What were the 3 groups in Edward Tolman’s rat cognitive map experiment?
Never rewarded
Always rewarded
Rewarded starting on day 11
What did Tolman find in his experiment?
Never rewarding rats made them constantly make errors
Always rewarding rats made them have few errors
Rewarding rats on day 11 after 10 days of no food rewards made them perform almost perfectly in the maze!??!!
Spatial ratemap
Firing rate of a neuron presented as a function of space
Place field
A small area of increased neural activity
Created regardless of task demands (will occur even if you’re just wandering around without purpose)
Place cell
A neuron with spatial coding
Where are place cells found?
In the hippocampus
Do multiple place cells code for multiple different environments?
Yes!
Latent learning
The subconscious retention of information without reinforcement or motivation
What is an example of latent learning?
Rats will use the knowledge they learned from mazes to straight up climb walls and skip the entire puzzle because they know where the food is relative to their position
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Flashcard (25)