Thalamus

Question 1

Convergence

Answer 1

Neuron in brainstem is receiving sensory input from e.g skin, the neuron is getting input from many sensory neurons, they are all converging on this neuron
Neuron is getting complex input

Question 2

Divergence

Answer 2

One sensory neuron is sending an axon that splits and communicates with multiple neurons. Multiple 2nd order neurons are innervated by one sensory neuron
Seems like we are losing precision

Question 3

Retina example of divergence

Answer 3

Millions of pixels coming up from retina, as we move up through visual pathway info gets combined
Lines make shapes, shapes make more complex shapes

Question 4

Explain Lateral Inhibition

Answer 4

Strong central signal passes through and filters out weak surrounding signals
Inhibits neurons that are lateral to middle neuron
Inhibitory interneurons release GABA on side neurons so they are inhibited so center neuron fires a lot of AP but lateral neurons don’t fire
Lateral inhibition is found everywhere in sensory systems

Question 5

2 types of neurons in the brain

Answer 5

Excitatory - Glutamate
Inhibitory - GABA

Question 6

GABA vs Glutamate axon length

Answer 6

Glutamate - long
GABA - short, localized

Question 7

Gateway to cerebral cortex almost always…

Answer 7

Thalamus

Question 8

3 planes of cutting brain

Answer 8

Coronal
Horizontal
Sagittal

Question 9

Thalamus

Answer 9

Organized as numerous discrete nuclei

Question 10

3 functional distinct groups of thalamic nuclei

Answer 10

specific relay
association
intralaminar

Question 11

Specific relay nuclei

Answer 11

Converge in VPL and VPM (ventral posterior lateral/medial)

Question 12

VPL

Answer 12

SomatoSensory from body

Question 13

VPM

Answer 13

Somatoensory info from head

Question 14

Where in thalamus do specific relay nuclei convey visual information?

Answer 14

Lateral Geniculate Nucleus

Question 15

Where in thalamus do specific relay nuclei convey auditory information?

Answer 15

Medial Geniculate Nucleus

Question 16

Regions that control movement

Answer 16

Cerebellum
Basal ganglia

Question 17

Ventral anterior and ventral lateral nuclei

Answer 17

Specific relay nuclei that connect the cerebellum and basal ganglia with the motor cortex

Question 17

2 main association nuclei

Answer 17

Medial Dorsal Nucleus
Pulvinar Nucleus

Question 18

How do we ignore everything that we see except what we focus on?

Answer 18

Blocking some stuff

Question 19

What might association nuclei be doing?

Answer 19

Gatin info flow between different regions of the cerebral cortex (thalamus can act as a gate)
POSSIBLE NOT FOR SURE

Question 20

Medial Dorsal Nucleus (MD)

Answer 20

Inputs: Prefrontal cortex, olfactory and limbic structures
Cortical outputs: Prefrontal cortex

Question 20

Pulvinar Nucleus

Answer 20

Inputs: Parietal, Occipital and temporal lobes
Outputs: Parietal, occipital and temporal lobes, superior colliculus

Question 21

Intralaminar Nuclei

Answer 21

Internal medullary lamina has clusters of neurons embedded in it, probably part of the arousal system but this is hypothesized
Project diffusely to many region so cortex as well as subcortical structures such as basal ganglia

Question 22

What’s up with that stray neural synapse in the brainstem on the anterolateral pathway?

Answer 22

Activates the arousal system. That’s why pain causes arousal.

Question 23

MEMORIZE SPCIFIC RELAY NUCLEI OF THALAMUS TABLE

Answer 23

GO TO SLIDE NAMED SPECIFIC RELAY NUCLEI OF THE THALAMUS

Question 24

Pulvinar

Answer 24

Posterior/Caudal (Back parts of brain)

Question 25

Medial Dorsal

Answer 25

Medial Dorsal

Answer 26

Every single thalamic nucleus is getting input from the cerebral cortex

Question 27

Feedforward projections

Answer 27

Projections going UP the pathway E.g brainstem to VPL nucleus

Question 28

Feedback projections

Answer 28

Projections going down to thalamus

Question 29

Feedforward and feedback vision example

Answer 29

Retina -> LGN -> Cerebral cortex = feedforward Cerebral cortex -> LGN = feedback

Question 30

Cerebral Cortex

Answer 30

Thin sheet of tissue 2-4mm Divided into 6 layers 1 - outermost 6 - deepest

Question 31

Where do feedforward projections from the relay nuclei project?

Answer 31

Layer 4

Question 32

Example of C.C layer projections

Answer 32

Optic tract, Brainstem and Thalamic reticular Nucleus (GABA) feedforwarding to the Lateral Geniculate which then feedforwards to Layer 4 which then shows a feedback signal going back to the Lateral Geniculate from LAYER 6

Question 33

Driver inputs

Answer 33

Come from retina

Question 33

Modulator inputs

Answer 33

Feedback inputs coming from Layer 6 of cortex going back to Lateral Geniculate Come from brainstem (NE neurons) - tweak and modulate basic physiologic properties of the thalamic neurons Neuromodulators modulate behavioral of thalamus Thalamic reticular nucleus (GABA) projects into thalamus and modulate

Question 34

For Association nuclei...

Answer 34

Driver inputs are coming from the cerebral cortex AND modulator inputs are coming from the cerebral cortex Driver inputs come from layer 5 Modulator come from layer 6

Question 35

Feedback projections to the thalamus come from which Layer of CC?

Answer 35

Layer 6

Question 36

Hypothesis for what thalamus is doing - gatekeeper regulating info flow to the cortex

Answer 36

Modulatory inputs could be playing a role in altering the physiological properties with specific thalamic neurons so that the different neurons are either relaying the info to the cortex in different ways or maybe some of the neurons are relaying the info up and other neurons the info is getting filtered out Maybe helps you pay attention

Question 37

AP firing methods for thalamic neurons

Answer 37

Transmission mode Bursting Mode

Question 38

Transmission Mode

Answer 38

Output mirrors input If sensory inputs increase their firing rates then thalamic neurons will increase their firing rates

Question 39

Bursting Mode

Answer 39

Fire bursts of 3-8 action potentials separated by quiet periods lasting 100s of milliseconds Sleep wave cycles

Question 40

2 diff firing modes of thalamic neurons

Answer 40

Bursting Transmission

Question 41

Bursting mode and Sleep wave cycles

Answer 41

Neurons in cerebral cortex start firing in rhythmic bursts similarly to thalamic neurons Complicated interaction between C.Cortex and thalamus

Question 42

How are thalamic neurons shifted from burst firing mode to tonic (transmission) firing mode?

Answer 42

Neuromodulators (Acetylcholine, NE and Histamine) which are released during wakefulness depolarize thalamic neurons

Question 43

Reading 3

Answer 43

Association Nuclei of the Thalamus

Question 44

Internal Capsule

Answer 44

Axons follow the internal capsule which is a massive fiber tract to get to and from the cerebral cortex

Question 45

Where is the internal capsule?

Answer 45

Thin sheet of white matter surrounding the thalamus

Question 46

Horizontal view of internal capsule vs Coronal view

Answer 46

Look at slides