Task 2 - basal ganglia

Question 1

corpus striatum include

Answer 1

• caudate

- putamen

Question 2

caudate

Answer 2

• input from multimodal association cortices and from motor areas in frontal lobe that control eye movement
• association cortices receive input from primary and secondary sensory cortices and thalamic nuclei

-discharge in anticipation of limb and trunk movement

Question 3

putamen

Answer 3

• input from primary and secondary somatic sensory cortices in occipital and temporal lobes and auditory association areas in temporal
• fire prior to eye movement

Question 4

medium spiny neurons

Answer 4

• cells in corpus striatum with large dendritic trees
• allow them to integrate inputs from many cortical, thalamic and brainstem structures
• > converge on neurons in pallidum (globus pallidus and substantia nigra pars reticulata) -> output zone of basal ganglia

-number of spiny neurons contacted by single axon is really large -> integrate influences of many cortical cells

Question 5

striatum is functionally subdivided according to its inputs

Answer 5

• visual and somatic sensory cortical projections are topographically mapped within different regions of putamen
• more extensively cortical areas are interconnected by corticocortical pathways -> the greater the overlap in projections of striatum

Question 6

direct pathway

Answer 6

• go pathway
• projections from the medium spiny neurons of caudate and putamen to internal segment of GP
• > facilitates the initiation of volitional movement

Question 7

Parkinsons disease

Answer 7

• problems with movements
• reduction/slowing down in movements
• loss of dopamine neurons in brain
• substantia nigra: main area for dopamine
• > go to striatum (nigtostriatal pathway)
• dopamine neurons die -> can’t amplify direct pathway
• can’t prevent an excessive reduction in movement in indirect pathway
• hypokinetic

Question 8

D1 dopaminergic cells

Answer 8

-excites inhibitory outflow of striatum

Question 9

D2 dopaminergic cells

Answer 9

-turn down inhibitory outflow of striatum

Question 10

Huntingtons disease

Answer 10

• unable to stop movement
• hyerkinetic
• inhibitory outflow of basal ganglia is reduced
• activity in GPe reduces excitatory input of subthalamic nuclei to GPi
• > GPi inhibits thalamus less
• without restraining influence of basal ganglia
• > upper motor neurons can be activated by inappropriate signals -> resulting in undesired ballistic and choreifrorm movements

Question 11

medium spiny neurons in Huntingtons

Answer 11

• projections to external segment of GP degenerated
• > absence of inhibition from spiny neurons
• > GP becomes abnormally active
• > diminished ability of subthalamic nulei
• > less inhibitory response to GPi -> increased excitation of VA/VL complex of thalamus

Question 12

basal ganglia in general

Answer 12

• builds subcortical loop
• > links most areas of cortex with upper motor neurons in M1 and premotor cortex and brainstem
• neurons modulate their activity in anticipation of and during movement
• > required for normal cause of voluntary movement

Question 13

when do neurons in caudate and putamen fire?

Answer 13

putamen: discharge in anticipation of limb and trunk movement
caudate: fire prior to eye movement

-> activation of cells encode for decision to move toward a goal, not the direction and amplitude of the actual movement