Lecture 8 - Thalamus and Cortex Flashcards
The thalamus is mass of ___ matter (bilateral) at centre of the brain.
gray
The thalamus forms the major part of the ______.
diencephalon
What connects the 2 thalamus together?
a band of gray matter, the interthalamic adhesion
The thalamus is located on either side of what structure?
third ventricle
What is the major function of the thalamus.
processing center: nearly all pathways projecting to cerebral cortex pass via synaptic relays in thalamus
T/F: The thalamus is a major sensory relay for all sensory systems.
False (doesn’t relay olfactory information)
What 4 (non sensory) structures/systems communicate with the thalamus.
- cerebellum
- basal ganglia
- limbic system
- reticular activating system
T/F: The projections that run between the thalamus and the cortex are unidirectional.
False (bidirectional)
What are the 2 types of projections that thalamic neuclei send to the cortex?
specific and diffuse
What are the 2 functional classes of the thalamic nuclei?
- Relay Nuclei
2. Diffuse Projection Nuclei
What is the role of the relay nuclei?
- receive inputs and project to cortex
- receive recurrent input back from cortex
- most project to a specific,local region of cerebral cortex
What kind of thalamic nuclei would project onto the primary motor area?
Relay nuclei (b/c specific area of cerebral cortex
What is the role of the diffuse projection nuclei?
have more widespread projections than relay nuclei
What kind of thalamic nuclei would project onto the reticular system?
Diffuse projection nuclei
Structurally, the thalamic nuclei are separated into what 3 groups?
anterior, medial, and lateral
The thalamic nuclei are physically separated by what structure?
internal medullary lamina
T/F: The internal medullary lamina is composed of grey matter.
False (white matter)
Which thalamic nuclei have projections to the limbic pathway?
anterior and medial nuclear gps
The intralaminar nuclei is a relay nuclei.
False (diffuse)
The intralaminar nuclei is a relay station for motor pathways between what structures?
basal ganglia and cerebellum to cortex
Is the lateral nuclear gp a relay nucleus or a diffuse projection nucleus?
relay nucleus
The lateral nuclear gp is a relay station for what?
somatosensory inputs to cortex
basal ganglia and cerebellarinputs to motor areas of cerebral cortex
The lateral nuclear group houses what 2 other nuclei responsible for sensory information?
lateral and medial geniculate nucleus
What is the role of the lateral geniculate nucleus?
relays incoming visual information to visual cortex of occipital lobe
What is the role of the medial geniculate nucleus?
relays incoming auditory information to auditory cortex of temporal lobe
The ventral posterior lateral nucleus is part of what larger thalamic nucleus?
lateral nuclear gp
The ventral posterior lateral nucleus relays information from where and projects to where?
relays from somatosensory info coming in through the spinal cord; projects to primary somatosensory cortex
The motor pathways from the basal ganglia and the cerebellum relay to which 2 nuclei?
ventral lateral and ventral anterior nucleus
Where do the fibers from the ventral lateral and ventral anterior nuclei project?
Motor cortex
A pt had an ischemic stroke which affected the thalamus. The specific location of the infarct wasn’t noted within her charts but you suspect which one of which 2 arteries?
Posterior Cerebral Artery
Anterior Choroidal Artery
What are the two most common lesions to the thalamus?
thrombosis (ischemic stroke) and hemorrhagic (rupture of the artery)
What would you expect in a pt who is recovering from a thalamic infarct. What is the formal name for it?
thalamic pain (instense burning pain) -> dysaesthesia
What two structures connect the two cerebral hemispheres?
corpus callosum and anterior commisure
T/F: The two cerebral hemispheres are completely symmetrical.
False
Name the 4 types of hemispheric specializations which makes the cerebral hemispheres asymmetrical.
- handedness
- skilled complex motor tasks
- language
- non-verbal functions
Of the 4 hemispheric specializations, which ones are programmed by the dominant side and which are programmed by the non-dominant side. Is this true for all people? What differs amongst people?
- handedness (dominant)
- skilled complex motor tasks (dominant - usually left)
- language (dominant)
- non-verbal functions (non-dominant)
True among all people, however, the side that is dominant might not be the same for everyone.
What is the cerebral cortex composed of and how many layers does it have?
grey matter (cell bodies, dendrites, axons) 6 layers
What is the highest level of the CNS?
cerebral cortex
Describe the function of all 6 layers of the cerebral cortex.
Layer I,II and III: Intracortical connections
Layer IV: incoming sensory signals
Layer V: output to other brain areas and spinal cord (large pyramidal cells)
Layer VI: output to thalamus
You are analyzing a sagittal dissection of cerebral cortex and you notice that the 4th layer is much thicker than the other layers. From what part of the brain can you assume the dissection was taken?
4th layer responsible for incoming sensory signals so I can assume that the dissection came from a sensory cortex
Does the cerebral cortex vary depending on its location in the brain?
Yes - the thickness of some of the layers (esp. layers 4 and 5) will reflect the function of that area of the brain
The primary sensory cortex recieves input from ____ nuclei of the thalamus.
relay
List the 5-6 primary sensory areas within the cortex.
- visual
- vestibular
- auditory
- gustatory
- olfactory
- somatosensory
Describe the homunculus for the primary somatosensory cortex and the primary motor cortex. Are they similar?
Homunculi for primary somatosesory cortex and primary motor cortex are very similar.
Medial - lower extremity
Lateral - face, upper extremity
Where is the insula located?
When you peel apart the Sylvian fissure you can see the insula.
List the 2 areas of the brain the process vestibular info.
- Primary vestibular area
2. Posterior insula
List the 2 areas of the brain the process gustatory info.
- Primary taste area
2. Anterior insula
The olfactory cortex is composed of what 2 things?
- Piriform
2. Orbitofrontal cortex
Primary sensory cortices help to perceive info and association cortices help to _________.
conceptualize
Describe association cortices.
large areas adjacent to primary motor and sensory areas of the cortex
occupy at least 75% of brain surface
important for higher-order information processing:
concerned with behaviourand interpreting sensory experiences
involve previous memories and experiences
What are the 2 association cortices for the motor area?
- premotor area
2. supplementary motor area
T/F: Association cortices are always right next to the primary cortices.
True
What is the role of the somatosensory association area?
complex sensation (receives and integrates different sensory modalities)
e.g. tactile and proprioceptive information for manipulating an object
+ memory
e.g. recognizing objects placed in hand without vision
What is the role of the visual association area?
relates visual information to past visual experiences
analyzes colours and motions
directs visual fixation
What is the role of the auditory association area?
interpreting sounds
compares sounds with memories of sounds
categorizing sounds as language, music or noise
What is the primary task of the sensory speech area of Wernicke? Where is it located?
language comprehension;
part of the auditory association area in temporal lobe of dominant hemisphere
What are the major functions of the premotor cortex?
receives inputs from sensory cortex and basal ganglia via thalamus
stores programs of motor activity gathered as a result of past experience
important for complex motor tasks
projects to primary motor cortex
What are the major functions of the supplementary motor area?
planning of complex movements postural control coordinating two-handed movements -> requires communication between SMA of both hemispheres
Is the supplementary motor area always involved with learned motor movements?
No
Do the premotor cortex and supplementary motor area send info to the primary motor cortex individually or simultaneously?
Simultaneously
Describe how the premotor area and supplementary area work together.
They work together in preparation for the movement. Cells in motor association cortex increase their activity just prior to a movement
The motor speech area of Broca is responsible for what? Where is it located?
production of language;
motor association area, frontal lobe of dominant hemisphere
Differentiate between heteromodal association cortex vs. unimodal association cortex.
heteromodal: integrates sensory AND motor information
unimodal: integrate either sensory OR motor
T/F: Both heteromodal and unimodal association areas integrate info from the limbic system (emotional and motivational input).
False (only heteromodal)
T/F: Unimodal association areas have the highest order mental functioning.
False (heteromodal)
T/F: Heteromodal association areas have bidirectional connections with motor, sensory, and limbic system.
True
The white matter of the brain is composed of what 3 types of fibers?
- association fibers
- commissural fibers
- projection fibers
Where do you find association fibers?
Connecting different cortices within one hemisphere (short and long fibers)
List 2 sites where you would find commissural fibers.
- corpus callosum
2. anterior commissure
Pprojection fibers are found in what pathways?
Motor and sensory (internal capsules)
Your next patient has a lesion on his motor association area. What are you expecting to see?
difficulty in performance of skilled movements (complex motor tasks); apraxia
Define apraxia.
neurological disorder characterized by loss of the ability to execute or carry out skilled movements and gestures, despite having the desire and the physical ability to perform them.
A patient comes to your clinic because they want to work on improving the neglect that is evident in their L arm. Upon seeing them walk in you suspect that they had a lesion on what part of the brain?
parietal lobe of the non-dominant hemisphere
A lesion of the frontal lobe would most likely land in an ________ cortex.
Association
You are a PT in a hospital setting and your next pt has a lesion on his frontal lobe. Before you even see the pt, what are you expecting?
- personality changes
- disorders in cognitive functioning: impaired judgment
- difficulty sequencing actions or changing activities