basal ganglia Flashcards
What are the major constituents of the basal ganglia?
Masses of grey matter (nuclei) in the cerebral hemispheres around the thalamus • Caudate • Putamen • Nucleus accumbens • Globus pallidus • Subthalamic nucleus • Substantia nigra, ventral tegmentum
What is meant by the term striatum?
Corpus striatum = Striatum=caudate plus putamen
Where are the basal ganglia located?
surround the thalamus
- Describe the sources of dopamine neuromodulation for the striatum.
Substantia nigra pars compacta
- What is a corticostriate (CS) loop?
x
What are the general functions of the direct and indirect pathways of CS loops?
direct–>voluntary action
- What are the four known CS loops and what parts of the cortex do each of them involve?
x
What are the general functions of each of the loops?
x
- Distinguish procedural memory from declarative and emotional memories.
x
- What are the three aspects of procedural memory?
- implicit(unconscious)
- rigid
- procedural(expressing how to do something),
• emergent properties of cortico-striate loop
activity.
What is the difference between declarative and procedural learning of visual categories?
Declarative: depend on hippocampus and prefrontal regions (working memory/executive attention. mediated by hypothesis testing system. IN a field of dots, FIND the central one
Procedural:visual cortico-striate loop. In a field of dots POINT to central one. Strong visual signals enhanced, weak ones inhibited.
- What impact does dopamine neuromodulation have in action selection and instrumental/reward learning?
DA from midbrain: external/internal stimuli–> associative learning reinforcement
DA to striatum alters activity of direct vs. indirect pathways
DA reinforces behavior by innervation of nucleus accumbens , where dopamine strenghtens links between behavior and reward. Mediates wanting and liking
DA makes synapses more excitable, increasing conditioning of certain stimulus to motor pathway
well established behavior less DA dependent
- Distinguish between instrumental and reward learning. What is the difference in their outcomes?
Instrumental learning involves
• goal and action (kick ball to right place)
• stimulus responses (see ball then kick)
associations
also habit formation…automatic eventually
Reward learning:
Behavior conditioned by association of a stimulus with a reward or outcome, rather than with motor response itself
•Mediated by motivational loop:including vmPFC, orbitofrontal cortex(OFC), and nucleus accumbens
- What are the general actions of addictive drugs on the motivational CS loop?
Drugs reinforce addictive behavior via mesolimbic dopamine system.
Addiction is associated with imbalance between PFC and VTA acting on the n. accumbens
Enhanced activity of DA neurons in the ventral
tegmental area (VTA) –>heightened responses to drugs and drug-related stimuli –> facilitates motivational responses to
relapse-inducing stimuli.
PfC weakens and can’t control VTA…
- What are the characteristics and causes of: chorea,
pathology: involuntary jerky movements of face, tongue, limbs. Underactivity of indirect pathway so dorect predominates, loss of striatal GABA
caused: lesion of striatum and cortex
