PSYC 210 - Exam 2

My notes again :^) this is EVERYTHING from the slides

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

1. Cerebellar cortex

2. Pontine nucleus

3. Cerebellum

4. Deep cerebellar nuclei

5. Thalamus

6. 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

1. How arousing the stimulus is

2. The number of times it is experienced

3. 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?

1. Never rewarded

2. Always rewarded

3. 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