produce internally generated mvmts

(freeing individuals from stimulus bound responses or goal oriented mvmts)

Learning & retention of complex motor tasks (Procedural/Habit Learning)

movement is dramatically reduced

Parkinson's

excessive & uncontrollable involuntary mvmts

Huntington's chorea

Five areas of gray matter in the telencephalon

1. Caudate nucleus

2. Putamen

3. Globus Pallidus

4. Nucleus Accumbens

5. Olfactory Tubercle

Lentiform nucleus: putamen, GP

Corpus Striatum: putamen, GP, caudate

Dorsal Striatum: putamen, caudate

Ventral Striatum: putamen, caudate, nucleus accumbens, olfactory tubercle

1. Substantia nigra (in mesencephalon)

2. Subthalamic nucleus (at junction b/t mesencephalon & diencephalon)

1. Striatum (MSN)

2. Globus pallidus (GPi, GPe)

3. Subthalamic nucleus

4. Substantia nigra (pars reticulata, pars compacta)

-receives most of the inputs to the BG

-origin of the BG output circuitry

-made up of the caudate & putamen (have indentical internal structures but are separated by the internal capsule from e/o)

-2 types of neurons (MSN, small interneurons)

-send axons out of the striatum

-dendritc spinde of MSN are plastic (change shape & properties)

-Can be divided into 2 types based on the types of circuits they participate in

Indirect: enkephalin, D2 dopamine receptors

Direct: dynorphin, subs. P, D1 dopamine receptors

GABA- From their axon terminals & INHIBIT the activity of their target cells

However, MSNs are "usually quiet"-have to be excited to inhibit

whitish appearance due to large number of myelinated axons

contains LARGE NEURONS that contain GABA (like MSN) and are INHIBITORY to their targets

Divided into two compoents:

GPi and GPe

separted from BG by the crus cerebri

Neurons send their axons to the BG & contain the EXCITATORY NT-GLUTAMATE

pars reticulata (SNR)

pars compacta (SNC)

strucuturally similar to GPi

SNR & GPi are the output structures of the BG

Cells release GABA from their axon terminals & like GP are constantly active

neurons contains the NT DOPAMINE

the neurons provide Dopaminergic innervation of the striatum (nigrostriatal pathway) which ends on MSNS and internueurons

GP & subthalamic nucleus are innervated by SNC also

dopaminergic neurons in the SNC degenerate in Parkinson's

Closed Loops: connect up with the same cortical area providing the input

Open Loops: connect up with cortical areas different from the input area

All cortical areas send axons to the striatum...These corticostratiate projections are EXCITATORY and use amino acids (Glutamate) as the NT

Projections end mostly on the dendritic spines of MSNs

Frontal lobe areas= head of caudate

Parietal lobe= body of caudate

Occipital & Temporal areas=tail of caudate

Premotor cortex= send axons directly to subthalamic nuclesus

Somatosensory & motor cortices= putamen

segregated loop circuits thru the BG

Major output target= thalamus (whose nuclei innervate the cerebral cortex)

1. Ventral Anterior (VA) nucleus

2. Mediodorsal (MD) nucleus

3. Posterior intralaminar nucleus

GPi=innervates the LATERAL VA which connects with PREMOTOR & SUPPLEMENTARY MOTOR cortical areas

SNR= innervates the MEDIAL part of VA connected with FRONTAL EYE FIELDS which control voluntary eye mvmts

Centomedian-parafascicular (CM/PF) complex (intralaminar) receives input from GPi and SNR

CM/PF = innervate the striatum, subthalamic nucleus, & premotor and supplementary motor areas AND motor cortex area 4 (unlike VA)

unclear

lesions lead to unilateral motor neglect

1. Superior Colliculus

SNR sends axons to the sup. colliculus & influences control of SACCADIC EYE MOVEMENTS

2. Midbrain tegmentum