Mod 3 Brain White Matter Pathways Flashcards
What are the white matter pathways?
- Projection
- Association
- Commissural
The projection pathways are ____ pathways that run between ___ and ___
Vertical
Cortex
Lower levels
___ connect areas within hemispheres
Association
___ connect areas between hemisphere
Commissural
pathways connection and interconnection functions include
- Keep the brain informed of what’s going on within and outside the CNS
- Mediate info transfer between modalities
- Coordinate activities between hemispheres
Characteristics of projection pathways
- Connect the cortex with lower levels
- Travel vertically to connect cortex with brain structures and spinal cord
- Include both efferent (outgoing/motor) and afferent (incoming/sensory) pathways
What is the most prominent and important motor projection system
Pyramidal tract
True or false: the pyramidal tract is comprised of the corticospinal pathway
False: both corticospinal and corticobulbar pathway
What is the pyramidal tract responsible for
Initiation and control of skilled voluntary movements
Where do the fibers in the pyramidal tract originate from?
Areas 4, 6 in the frontal lobe
Area 3-1-2 in the parietal lobe
True or false:
The motor neurons that make up the pyramidal tract (both corticospinal and corticobulbar) are lower motor neurons
False: upper motor neurons
_____ are peripheral nerves
Lower motor neurons
Lower motor neurons innervate the ______ muscles
Voluntary/skeletal muscles
LMN is also known as
Final common path
Upper motor neurons are _____ motor neurons with the _____ that exert influences either directly or indirectly on the LMNs
Descending
CNS
Sensory data is relayed to the thalamus then to the cortex via the ____ pathways
Thalamocortical pathway
The motor projects extend from the ____ to the ____ and ____
Cortex
Brainstem and spinal cord
Motor projects descend downward to the brainstem via the _____, ______ and _____
Corona radiata
Internal capsule
Cerebral peducles (crus cerebri)
___ is a fan shaped radiating projection system located between the cerebral cortex above and the internal capsule below
Corona radiata
The motor pathways extend downward from the ____ areas through the _____ and converge before enter the the ____
Cortical
Corona radiata
Internal capsule
True or false
The corona radiata is comprised of only motor pathways
False
Comprised of both motor and sensory pathways
- incoming sensory pathways extend upward from the internal capsule to the cortex.
What is the internal capsule
A massive bundle of nerve fibers found between the thalamus, caudate nucleus and lenticular nucleus
Most signal, both efferent and afferent, between the cerebral cortex and the lower brainstem, and spinal cord are transmitted between ___
Internal capsule
The internal capsule is divided into what parts
Anterior limb (between the caudate and lenticular nucleus) Posterior limb (between the lenticular nucleus and thalamus) Genu (between the anterior and posterior limb)
What does the anterior limb carry
Motor data
Affective and emotional data
The anterior limb carries motor data via the
Frontopontine pathway (frontal lobe/cortex to the pons) Corticostriate pathway (cortex to BG/striatum)
The anterior limb carries affective and emotional data via
Reciprocal connection pathways Includes: Between the prefrontal cortex and thalamus Between the cingulate gyrus and thalamus Between the septal area and hypothalamus
What passes through the Genu of the internal capsule
The corticobulbar pathway = motor commands for speech
The corticoreticular pathway = arousal and alertness
The posterior limb contain both ___ and ___ pathways
Moto and sensory
Posterior limb: motor has what kind of pathway
Corticospinal
What does the motor posterior limb innervate
Limb and trunk muscles
The posterior limb sensory carry general and sensory data to
- General to Somatosensory cortex (3-1-2)
- Auditory to Heschl’s gyrus (41 and 42)
- Visual to striate cortex (17)
The association pathways provide ____ communication between cortical areas
Bidirectional
In the association pathways, there are ___ and ____ groups
Long and short
What areas do not communicate directly with each other?
Primary areas
How do primary areas communicate with each other
Via the association areas
Arucate fasciculus is also called
Superior longitudinal (located lateral to insula)
What does the arcuate fasciculus connect?
Interconnects the frontal, parietal, occipital and temporal cortices
Connects Wernicke’s and Broca’s areas
What is conduction aphasia
A disconnection syndrome between Wernicke’s and Broca’s aphasia
Where is the lesion that would cause conduction aphasia
Arcuate fasciculus lesion
What is the result of conduction aphasia
Good comprehension, reduced and impaired speech output
Where is the inferior occipital fasciculus located
Crosses beneath the Sylvia’s fissure and insula
What does the inferior occipital fasciculus connect?
The frontal lobe to occipital lobe and the inferior temporal lobes she
Where is the uncinate fasciculus located
Parallel to the inferior longitudinal fasciculus
The uncinate fasciculus connects
Orbital frontal with anterior temporal lobe cortex
The cingulum connects
The frontal, parietal, temporal area medially
Interconnects these areas with the limbic area
If there is a lesion on the cingulum what is impaired?
emotion and affective behavior
Commissural pathways
Run horizontally to connect hemispheres
Connect similar structures on each side
What are the main commissures
Corpus callosum
Anterior commissure
Posterior commissure
What is the largest commissural bundle
The corpus callosum
Contain 300-400 million fibers
What are the parts of the corpus callosum
Rostrum (interconnects the frontal areas) Genu Body (interconnects parietal areas) Splenium (interconnects occipital areas)
The anterior commissure interconnects the ___ lobe
Temporal lobe
The posterior commissure interconnects _____ _____ _____
Midbrain reflex centers
Lesions to association and commissural fibers lead to
Disconnections between cortical areas = disconnection syndrome
What is apraxia
Motor programming disorders that affect limb movement (limb apraxia), speech movements (apraxia of speech) and oral non speech movements (oral apraxia/swallowing apraxia)
What is Alexias
Acquired reading disorder
What is anomia
Unable to recall the names of everyday objects
Disconnection syndromes caused by lesions of association and commissural fibers can cause:
Apraxias
Anomia
Alexias