Ch. 15, 16, 26 Cerebellum, Basal Ganglia, Cerebrum Neuroscience Exam 2

Role of Cerebellum

Adjusts posture & coordinates movement; Compares intended with actual movements and adjustments needed; cerebellar adjustments is must for smooth, accurate movements

Outer layer of Cerebellum

gray matter with 3 layers

Outer and inner layers of cerebellum contain..

interneurons

The middle layer of the cerebellum contain…

purkinje fibers; all output from the cerebellar cortex is transmitted via purkinje fibers

Two types of axons that release excitatory afferent signals in cerebellum..

mossy fibers-sensory

-climbing fibers-movement errors

Where does the cerebellum lie and attach to?

inferior to occipital lobe and attaches to posterior brainstem

3 functional regions of cerebellum

vestbulocerebellem, spinocerebellum, cerebrocerebellum

vestibulocerebellum

flocculonodular; controls equillbirum and balance

spinocerebellum

vermis and paravermal regions; controls gross limb movement

cerebrocerebellum

lateral hemispheres; controls fine motor control

vestibulocerebellum input

IL vestibular apparatus

vestibulocerebellum output

coordination of eye movement, balance, equllibrium, and processing of emotions

spinocerebellum input

extensive from spinal cord about movement commands, activity levels, and postural adjustments ; includes posterior spinocerebellar, cuneocerebellar, and internal feedback

posterior spinocerebellar input

proprioceptive info from lower limb

cuneocerebellar input

proprioceptive info from neck, UE, upper trunk

internal feedback input

spinal interneurons and descending MTs

spinocerebellum output

no neurons directly convey signals from cerebellum to MNs; includes vermal section and paravermal section

vermal section output

adjust activity in medial UMN

paravermal section output

influence lateral corticospinal tract

cerebrocerebellum input

extensive, indirect connections from cerebral cortex

cerebrocerebellum output

coordination of fine, voluntary movemtn, planning, timing, and cognitive function

signs of cerebellar motor dyfunction

abnormal motor execution that does not change with or without vision; ataxia; chronic alcoholism; nystagmus, unsteadiness, difficulty maintaining sitting and standing balance

abnormal motor execution that does not change with or without vision

IL lesion

ataxia

incoordination

chronic alcoholism

affects spinocerebellum and interferes with fine movements, ataxia gait

nystagmus, unsteadiness, difficulty maintaining sitting and standing balance

vestibulocerebellar lesions

dysdiadokokinesia

spinocerebllum lesion; trouble with rapid alternating movement

dysmetria

spinocerebllum lesion; difficulty and error when moving intended distance and target

action tremor

spinocerebellum lesion; shaking of limb during voluntary movement; can be compenstated by moving one joint at a time to break up task

cerebellar lesions

cause ataxia regardless of the use of vision

cerebellar lesions can be tested using…

romberg test, achilles DTR s-abnormal and impaired c-intact; propriocpetion/vibration s-impaired c-intact

Basic Functions of the Basal Ganglia

physiological functions of goal-directed and social behavior; decision making, judgement, prioritizing information; emotional processing and responses; learning; eye movements; spatial attention; motor output

Names of Basal Ganglia Nuclei

Striatum

-Caudate

-Putamen

Lentiform Nucleus

-Globus Pallidus

-Putamen

Subthalamic Nucleus

Substantia Nigra

Where is the subthalamic nucleus?

diencephalon

Where is the sustantia nigra?

midbrain

Input to BG

cortical motor areas- excitation glutamate

interneurons excitation-achetylcholine

Outputs from BG

GABA- inhibits thalamus

Within BG

-glutamate

-GABA

-dopamine

• from substantia nigra to adjust signals to output nuclei

BG output has profound effects on…… but

movement, but no direct output to motor neurons

3 distinct activities via 3 different pathways

voluntary muscle activity, postural and girdle muscle activity, walking

3 non motor loops of BG

goal directed behavior circuit, social behavior circuit, emotion and motivation circuit

2 motor loops of BG

oculomotor circuit, motor circuit

Goal-directed behavior circuit

head of cauduate; decision making circuit for goal-directed behavior; evaluates info. for making decisions, planning, and choose appropriate actions in active learning

Social Behavior Circuit

head of the caudate; recognizes social cues, regulates self-control, and parses out relevant and irrelevant information (prioritizes)

Emotion and Motivation Circuit

ventral striatum; participates in emotional expression, seeking rewards, and motivation; integrates emotions with other loops ; if damaged, leaves a flat-faced expression with low motivation

Oculomotor circuit

body of the caudate; makes decisions about spatial attention and eye movements; specifically, determines fast eye movement to direct attention

Motor Circuit

cortex, putamen, STN, GPi, and motor from thalamus; regulates muscle contaction, muscle force, multijoint movements, and sequence of movements; has profound effects on movement, but no direct output to motor neurons

3 pathways of motor circuit

hyperdirect, no-go, go