L13 - The Thalamus

Question 1

What are the three functional groupings of thalamic nuclei?

Answer 1

Specific relay
Association
Non-specific

Question 2

List the sensory specific relay nuclei and give their function

Answer 2

Ventroposterolateral nucleus - somatosensation
Ventroposreromedial nucleus - somatic sensation and taste
Medial geniculate nucleus - audition
Lateral geniculate nucleus - vision

Question 3

List the motor specific relay nuclei and state their function

Answer 3

Ventrocuterior nucleus - intiating and planning of movement

Ventrolateral nucleus - body movement co-ordination

Question 4

List the association nuclei and state their function

Answer 4

Anterior nucleus - episodic memory
Lateraldorsal nucleus- spatial orientation and learning related to ss cortex
Mediodorsal nucleus - learning and decision making
Pulvinar - stimulus processing, maintenance of oscillatiory dynamics mediating the effects of attention

Question 5

List the non-specific nuclei and state their function

Answer 5

Centromedian nucleus - Arousal and attention, control of cortical activity, pain and sleep waking cycle
Thalamic reticular nucleus - sensory information processing, attentiom. Generation of synchronous activity, sleep waking cycle.

Question 6

Outline the whisker barrel system

Answer 6

Key for detection. Each barrel belongs to a specific whisker. So whiskers on snout –> barrelettes in hindbrain –> barreloids in vpn thalamus –> barrels in si neocortex

Question 7

What are the three classes of visual ganglion cells that project to the LGN?

Answer 7

P, m and k

Question 8

List the properties of p ganglion cells

Answer 8

Larger cell bodies
Extensive dendritic fields
Larger diameter axons
Larger receptive fields
Faster conduction velocity
Respond transiently to the presentation of visual stimuli
Motion detection
More sensitive to contrast stimuli

Question 9

List the properties of p ganglion cells

Answer 9

Smaller cell bodies
Smaller dendritic fields
Smaller diameter axons
Smaller receptive fields
Slower conduction velocities
Respond in a sustained fashion
Transmit info about shape and colour

Question 10

List the properties of k ganglion cells

Answer 10

Fine calibre axons

Short wavelength sensitive cones

Question 11

What are the three layers of the LGN?

Answer 11

Magno-, parvo- and koniocellular layers

Question 12

How were the properties of each layer of the LGN discovered?

Answer 12

They performed an experiment in which they selectively damages different layers. They found that if the magnocellular layer was damaged if reduced the ability to perceive rapidly changing stimuli, if the parvocellular layer is damaged visual acuity and colour perception is impaired.

Question 13

List the properties of the magnocellular cell layer

Answer 13

Large neurons
Transient discharge pattern
High contrast sensitivity
Largely process motion and depth info

Question 14

Describe the parvocellular cell layer

Answer 14

Small neurons
Sustained discharge pattern
Low contrast sensitivity
Largely process form and colour info

Question 15

Describe Koniocellular cell layer

Answer 15

Small neurons

Carry signals from short wavelength sensitive cones

Question 16

Which layers of the LGN does the left eye project to?

Answer 16

1
4
6

Question 17

Which layers of the LGN does the right eye project to?

Answer 17

2
3
5

Question 18

Which layer does the LGN input into the visual cortex?

Answer 18

Layer IV

Question 19

What does the pulvinar do?

Answer 19

It forms input output loops mainly with the cortex for visual processing and modulating neuronal oscillatory dynamics in the visual cortex.

Question 20

Give an example of how perceptual response modulation in the LGN can be shown

Answer 20

Participants perceived a high contrast horizontal grating which gave increased LGN activity opposed to a perceived low contrast vertical grating.

Question 21

Outline the tonic mode

Answer 21

T-channel is inactivated and the cell is depolarised.

This form is more faithful to retinal output

Question 22

Outline burst mode

Answer 22

Initial hyperpolarisation then depolarisation. T-channel is activated. This is useful for initial stimulus detection.

Question 23

What are the three divisions of the medial geniculate body?

Answer 23

Ventral division (MGBv) --> processing of auditory info
Dorsal and medial divisions (MGBd and MGBm) --> multisensory

Question 24

What is contralateral hemianesthesia?

Answer 24

Damage to the vpl and vp, which causes loss of all ss modalities

Question 25

Where is the thalamus located?

Answer 25

In the forebrain diencephalon