Thalamus

Question 1

What can cause LGN degeneration?

Answer 1

Removing the eye, occipital cortex or axons to cortex

Question 2

Recite the pairings of cortex lesion to the corresponding thalamus region of degeneration

Answer 2

Frontal pole -> medial thalamus
Medial cortex -> anterior thalamus
Motor cortex -> anterior half of ventral nucleus
Anterior parietal -> posterior half of ventral nucleus
Occipital cortex -> Lateral geniculate body (LGB)
Temporal cortex -> Medial geniculate body (MGB)

Question 3

Describe the inner and outer anatomy of the thalamus

Answer 3

connected via massa intermedia (fusing of lateral ventricles); external medullary lamina (outer fiber sheet); ; inside divided into ventral, lateral and dorsal tier via Y shaped internal lamina

Question 4

Name the thalamus nucleus groups

Answer 4

anterior nucleus (from hippocampus to cortex), ventral anterior (cerebellum/basal ganglia -> motor), ventral lateral (cerebellum/basal ganglia -> motor), ventral posteriolateral (body/limbs -> somatosensory), ventral postomedial (face/gustation -> somatosensory), pulvinar nucleus (auditory/vision/sensory -> parietotemporaloccipital association), lateral posterior (integrate sensory -> association) , dorsomedial (emotional behavior and memory), reticular nucleus (inhibiting/limiting), lateral geniculate (retina -> cortex) , medial geniculate (inferior colliulus -> cortex); metathalamus

Question 5

How did people used to classify thalamus nuclei

Answer 5

specific (sensory, motor, association, limbic) vs nonspecific (regulates ‘tone’; diffuse projections; e.g. reitcular nucleus that gets input from reticular activating system, midline groups )

Question 6

What is the more modern way of classifying thalamic nuclei?

Answer 6

1) First order (from subcortical/peripheral) & high order (from cortical areas; medial dorsal, lateral dorsal, pulvinar, intralaminar); 2) by direct pathways

Question 7

How could you classify inputs to thalamic relay cells

Answer 7

Drivers & Modulators. Drivers are only 5%, powerful synapses on distal dentrites (e.g. retinal input); FIve types of modulators (corticothalamic (layer 6), reticular nucleus (GABA), interneuron (GABA), neuromodulator (oxt, NE, histamine, etc)

Question 8

What are the components of a thalamic triad

Answer 8

1) afferent fiber terminal, 2) dendrite of a thalamic relay neuron, 3) dendrites of a interneuron (postsynaptic to terminal, presynaptic to relay neuron); triad form glomerular structure

Question 9

Describe the reticular nucleus

Answer 9

It is a sheath on the dorsal and lateral area of hippocampus. thalamocortical and corticothalamic projects penetrate the nucleus and form excitatory synapses with reticular nucleus which will then inhibit the relay neuron

Question 10

Describe the relationship between inactivation and activation channels in the thalamus and their firing rates

Answer 10

depolarized -> inactivation channel opens -> tonal firing (good for accuracy); hyperpolarized -> activation channel opens -> burst firing (good for detection)

Question 11

Describe the relationship between inactivation and activation channels in the thalamus and their firing rates

Answer 11

depolarized -> inactivation channel opens -> tonal firing (good for accuracy); hyperpolarized -> activation channel opens -> burst firing (good for detection)

Question 12

what does thalamic activity look like in sleep vs non-sleep

Answer 12

awake: when relay cell depolarizes -> inactivation gate opens -> tonic (accurate rep of stimuli); when relay cell hyperpolarizes -> activation gate opens -> bursts (during drowsy states, increases detection of stimuli); nrem: bursting (interruption of relay state)