Thalamus/Cortex 1: Anatomy

Question 1

Is the thalamus mostly white matter, grey matter, or both?

Answer 1

It’s pretty much all grey matter.

Question 2

What are 3 types of circuits in the thalamus?

Answer 2

Relay, association, and non-specific.

Question 3

What’s the name of the wall of white matter that separates the thalamus into medial and lateral parts?

Answer 3

the internal medullary lamina (IML)

Question 4

What are encircled by the walls of the intermedullary lamina where it splits anteriorly? What are their most important function?

Answer 4

Anterior nuclei - maintain wakefullness.

Question 5

Where is the nucleus reticularis located in the thalamus?

Answer 5

It covers the whole thing like a sheet of paper.

Question 6

What part of the thalamus receives sensory (touch, proprioception) info from the head, mostly CN V?

Answer 6

The ventral posteromedial (VPM) nucleus.

*corrected from… something incorrect and not real

Question 7

Where does auditory info go in the thalamus?

Answer 7

The medial geniculate body.

Question 8

Where does visual info go in the thalamus?

Answer 8

The lateral geniculate body.

Question 9

Where does limbic information go in the thalamus?

Answer 9

The anterior nuclei (part of the Papez circuit)… which relays it to the cingulate gyrus

Question 10

What sort of signaling happens between the thalamus and cerebral cortex? Neurotransmitter used?

Answer 10

Reciprocal excitatory signaling, using glutamate.

Question 11

How does the reticular nucleus interact with the cortex and thalamocortical (TCs) relay neurons? Neurotransmitter used?

Answer 11

Cortex and TCs relay neurons send excitatory signals to the reticular nucleus, using glutamate.
Reticular nucleus send inhibitory signals only to the TCs, using GABA.

Question 12

Are the thalamocortical cells connected to eachother?

Answer 12

No.

Question 13

How many layers are in the cerebral cortex? Is layer thickness consistent across all areas of the cortex?

Answer 13

Six (though sometimes debated). No, the thickness varies by region.

Question 14

The histology of the cortex ranges from granular to agranular. Are motor areas more granular or agranular? Sensory?

Answer 14

Granular: Mainly sensory
Agranular: Mainly motor

Question 15

What is the Brodman map based on?

Answer 15

Histological differences between regions of the cortex.

Question 16

Do all neurons in a column of the cortex share functionality and respond to the same stimuli?

Answer 16

Yes.

Question 17

What are the two types of excitatory cells found in the cortex?

Answer 17

Pyramidal cells and granular cells.

Question 18

How can you tell an excitatory from and inhibitory neuron just by histology?

Answer 18

Excitatory cells have spines on their dendrites, inhibitory cells don’t.

Question 19

What’s the major feature you can use to identify a pyramidal cell in histology?

Answer 19

The apical dendrite. (the triangular cell body can sometimes be hard to see)

Question 20

In what cortical layer are granular cells primarily found?

Answer 20

Layer 4.

Question 21

In what layer does information from the thalamus arrive in the cortex?

Answer 21

Into layer 4.

Question 22

What’s the basic circuit-unit in the cortex?

Answer 22

Excitatory signal comes into layer, stimulates inhibitory cell and second excitatory cell. Inhibitory cell inhibits the second excitatory cell. Second excitatory cell send an excitatory signal to the next layer.

Question 23

What’s the order of cell layers through which information travels in the cortex?

Answer 23

Into 4, up to layers 2/3, down to layers 5/6, and out.

Question 24

Basically what’s different about the modern model of thalamus / cortex information flow vs. the traditional “serial” flow model?

Answer 24

Cortex (both motor and sensory) provide feedback to the thalamus…