Lecture 8: Modulation of Movement by the Basal Ganglia Flashcards
Pyramidal Pathway =
Executor Pathway
Extrapyramidal pathways: Signals are relayed through
Multiple accessory pathways involving
basal ganglia, cerebellum, brainstem nuclei. Most of these pathways
modulate movement through the pyramidal pathway (UMN & LMN).
Extrapyramidal pathways =
Accessory (indirect pathways)
Basal ganglia pathways function:
complex motor actions
Cerebellum pathways function:
movement coordination
Vestibulospinal tracts pathway function
antigravity and equilibrium, see
vestibular system
Corticorubrospinal pathway function
fine motor control
“Basal Ganglia” refers to
a large and functionally diverse
set of nuclei that lies deep within the cerebral hemispheres.
Basal Ganglia Consist of:
Five nuclei
Basal Ganglia Consist of
Five Nuclei:
⚫ Caudate
⚫ Putamen
⚫ Globus Pallidus (External and Internal)
⚫ Substantia Nigra:( pars compacta and pars reticulata)
⚫ Subthalamus
Striatum incudes (2):
Caudate
Putamen
The basal ganglia influences:
movement
The basal ganglia influences movement by
regulating
the activity of the UPPER MOTOR NEURONAL circuits
The basal ganglia influences movement by regulating
the activity of the upper motor neuronal circuits (6):
➢ Regulate muscle contraction,
➢ Force initiation and termination of movement,
➢ Regulate multi-joint movements,
➢ Control movement sequencing,
➢ Oculomotor control (e.g. saccadic eye movement),
➢ Motor habit learning.
motor functions of basal ganglia: control of:
complex patterns of motor activity
motor functions of basal ganglia: control of complex patterns of motor activity examples (6):
➢ Writing,
➢ Using scissors,
➢ Throwing balls,
➢ Shoveling dirt,
➢ Coordinating head & eye movements,
➢ Some aspects of vocalization (speech),
➢ Etc.
Basal Ganglia: Input Zone:
Striatum (caudate + putamen)
Basal Ganglia: Input Zone:Striatum receives and process
movement-related signals from (2) :
➢ Cerebral cortex (e.g. frontal,
parietal, temporal cortex).
➢ Substantia nigra pars compacta
(dopaminergic neurons).
Basal Ganglia: Internal circuits:Main neurons of the
Striatum (caudate and
putamen) are the:
Medium
spiny neurons (inhibitory - gaba)
Medium
spiny neurons (internal circuits) are inhibitory or excitatory?
inhibitory (GABA)
Axons of the medium spiny
neurons project to:
▪ Globus pallidus (External &
Internal),
▪ Substantia nigra pars
reticulata (not SN pars
compacta)
Basal Ganglia: Output Zone 1:
Neurones of the of internal
segment of globus pallidus
(inhibitory) → Ventral anterior
and ventral lateral complex
nuclei of the thalamus
(excitatory) → Motor cortex
on the frontal cortex (upper
motor neurons).
Basal ganglia: Output Zone 2:
Neurones of the
Substantia nigra pars
reticulata (inhibitory) →
Superior colliculus
(excitatory) that
command head and eye
movements.
Efferent cells of the
output zone (i.e. globus
pallidus internal &
substantia nigra pars
reticulata) are
inhibitory.
Basal ganglia: Output Zone: efferent cells of the output zone have high levels of spontaneous activity that:
prevent unwanted
movement by tonically
inhibiting cells in the
thalamus and superior
colliculus.
slide 13
Basal ganglia Pathways: Two pathways
that influence differently the activity of the upper
motor neuron
Basal ganglia Pathways: Two pathways
Direct pathway
Indirect pathway
Slide 14
slide 15
slide 16
Cortical input activate
direct and indirect
pathways:
Direct pathway disinhibits the
VA/VL
complex of the thalamus
Direct pathway disinhibits the VA/VL
complex of the thalamus to
allow the
activation of intended motor programs
in targeted muscles
Indirect pathway increases
inhibitory
influences on other upper motor neurons
to suppress competing motor programs
(i.e., blocks unwanted movement in other
muscles that do not contribute to the
wanted movement)
The indirect pathway can thus be
regarded as a
“brake” on the function of
the direct pathway “accelerator”
Direct pathway: facilitates the
initiation of motor
programs that express movement (i.e., promotes
voluntary movement in targeted muscles).
- Indirect pathway: facilitates
the suppression of
competing or non-synergistic motor programs (i.e.,
inhibits movement in other muscles that do not contribute
to overall wanted movement).
Simultaneous activity of the two pathways leads to:
the
generation of smooth and coordinated movements.
The basal ganglia is made up
of two pathways that
compete in order to generate
smooth movements.
The basal ganglia is made up
of
two pathways that
compete in order to generate
smooth movements.
Pathophysiology of Basal Ganglia:
Parkinson’s disease
Degeneration of the substantia nigra’s neurons: i.e. loss of dopaminergic
neurons
Pathophysiology of Basal Ganglia:
Parkinson’s disease: Loss of
dopaminergic inputs on the striatum
Parkinson’s disease causes:
rigidity, akinesia (i.e. inability to initiate and stop movement), and tremors
(i.e. repetitive movements at resting sate).
2nd most common neurodegenerative disease after Alzheimer’s disease
Parkinson’s disease
slide 22
Parkinson’s disease: Treatment Options (2):
(1) Dopamine-based medication
(2) Deep Brain Stimulation:
Parkinson’s disease: Treatment Options: Dopamine-based medication
L-Dopa
(dopamine precursor)
Parkinson’s disease: Treatment Options:Deep Brain Stimulation:
➢ Insertion of electrodes deep into the brain,
➢ Targeted structures: subthalamic nucleus, globus
pallidus internal,
➢ Repetitive and regular electrical stimulation.
Pathophysiology of Basal Ganglia:
Huntington’s disease:: degeneration of __ and the size of the
Degeneration of caudate and putamen neurons (medium spiny
neurons). The size of the caudate and putamen is dramatically reduced.
Pathophysiology of Basal Ganglia:
Huntington’s disease causes:
a movement disorder: hyperkinesia (i.e. rapid and jerky motions
with no clear purpose).
hyperkinesia
rapid and jerky motions
with no clear purpose
slide 25
slide 26
Basal ganglia nuclei participate in
the
generation of saccadic eye movements
Efferent cells of the
output zone (i.e. globus
pallidus internal &
substantia nigra pars
reticulata) are
inhibitory.
Efferent cells of the
output zonehave high levels of
spontaneous activity that
prevent unwanted
movement by tonically
inhibiting cells in the
thalamus and superior
colliculus
The basal ganglia is actively involved in
movement.
participates in generating smooth and coordinated
movements.
basal ganglia
- The basal ganglia is ideally placed to provide
contextual
information to movement production.
The basal ganglia serves to
program movement but also
to cognitive and emotional operations.
