4. Thalamocortex Flashcards
What is the THALAMOCORTEX
Thalamus + cerebral cortex, with their bidirectional connections
Where is the THALAMUS located?
- Dorsral to the ventral portion of the 3rd ventricle
- Medial to internal capsule
Main function of the THALAMUS
- RELAY station for sensory and motor signals. Integration and Processing of info before projecting to the cerebral cortex
- Makes up most of the DIENCEPHALON (thalamus, epithalamus, subthalamus, hypothalamus, metathalamus)
What are the two MEDULLARY LAMINAE of the thalamus (slide 5)
Layers of white matter dividing the thalamic nuclei
- EXTERNAL medullary lamina
- Separates the thalamus from internal capsule
- Contains projection fibres - INTERNAL medullary lamina
Separates thalamus in its groups of nuclei:
- Lateral vs medial thalamic nuclei
- Rostral vs caudal thalamic nuclei
- Interlaminar (midline) thalamic groups
Nucleus of the ROSTRAL thalamic group
- Rostral thalamic nucleus (limbic system)
Nucleus of the MEDIAL thalamic group
- Medial dorsal nucleus
Nuclei of the LATERAL thalamic group (dorsal, ventral and ventral caudal divisions)
DORSAL Tier
* Dorsolateral nucleus
* Caudolateral nucleus
* Pulvinar nucleus
VENTRAL tier
* Ventral rostral nucleus (extrapyramidal)
* Ventral lateral nucleus (cerebellum)
VENTRAL CAUDAL group
* Ventral caudal medial nucleus (cranial nerves)
* Ventral caudal lateral nucleus (spinal nerves)
Nucleus of the CAUDAL thalamic group
- Medial geniculate nucleus (auditory, vestibular)
- Lateral geniculate nucleus (vision)
Nucleus of the MIDLINE (intralaminar) thalamic group
- Central medial nucleus
- Paraventricular nucleus
What is the thalamic RETICULAR nucleus
- Borders the internal capsule (laterally) and external medullary lamina (medially)
- Receives ARAS sensory afferents
- Projects to thalamic association areas
What are the 3 projection systems of the thalamus
- Direct cortical projection system
- Diffuse cortical projection system
- Thalamic reticular formation
Memorize table slide 17
Good luck
Location of FRONTAL lobe
- Rostral to cruciate sulcus
Location of TEMPORAL lobe
- Ventrolateral aspect of cerebrum (includes sylvian gyrus)
Location of PARIETAL lobe
- Caudal to cruciate sulcus
- Dorsal to sylvian gyrus
Location of OCCIPITAL lobe
- Caudal third of cerebrum
Name the 5 primary cortical areas
- Somesthetic
- Motor
- Olfactory
- Auditory
- Visual
What is the role of association areas
- Integrate info from primary sensory areas
- Allows perception of complex stimuli
- Associative memory
- Learning
Areas of the PRIMARY somesthetic cortex (SI) are activated by stimuli from ____ side of the body
Contralateral, except rostral face (teeth, palate, lip)
Areas of the SECONDARY somesthetic cortex (SII) are activated by stimuli from ____ side of the body
BOTH sides of the body
Understand somatotopic organization of the body parts for SI and SII
Slides 23-24
Which primary sensory area does not involve cortical projections via the thalamus?
Primary olfactory area (piriform lobe).
Receives direct projections from the lateral olfactory tracts
Describe menace response pathway (slide 34)
- Retina
- Optic nerve
- Optic chiasm
- Optic tract
- LGN
- Optic radiations
- Visual cortex
- Association fibers (internal capsule)
- Motor cortex
- Projection fibers (internal capsuel)
- Crus cerebri (mes)
- Longitudinal fibers (pons)
- Pontine nucleus (pons)
- Transverse fibers and middle cerebellar peduncle
- Cerebellar cortex
- Cerebellar efferents
- Facial nuclei (bilat)
- Orbicularis-oculi
PRIMARY MOTOR CORTEX
- Location
- Postcruciate ± precruciate gyri
- Rostral suprasylvian gyrus
SOMATOSENSORY CORTEX
- Location
- Postcruciate + precruciate gyri
- Rostral suprasylvian gyrus
(overlaps with motor cortex)
AUDITORY CORTEX
- Location
- Receives inputs from
- Medial ectosylvian gyrus (temporal lobe)
- Medial geniculate nucleus (thalamus) - relay for auditory
VISUAL CORTEX
- Location
- Receives inputs from
- Caudal part of the marginal, endomarginal, ectomarginal, occipital and splenia gyri
- Lateral geniculate nucleus (thalamus) - relay for visual
OLFACTORY AREA
- Describe the 2 olfactory tracts originating from the olfactory bulb
Olfactory bulb, to:
- MEDIAL olfactory area –> limbic system + reticular formation
- LATERAL olfactory area –> limbic system + piriform lobe
(no thalamic relay needed)
What is the impact of a uni- vs bilateral lesion to the somesthetic cortex ?
- Unilateral –> temporary contralateral deficits
- Bilateral –> more pronounced, bilateral but transient deficits
What is the impact of a unilateral lesion to auditory area?
Incomplete hear loss (extensive bilateral inputs).
Deafness requires either:
* Unilateral lx to cochlear nuclei or nerve
* Bilateral brainstem lx
Name the 6 histological layers of the cerebral cortex
- Molecular layer
- Few neurons (horizontal neurons of Cajal)
- Mainly axons + dendrites - External granular layer
- Granule (stellate) cells
- Small pyramidal neurons - External pyramidal layer
- Small + medium pyramidal neurons - Internal granular layer
- Densely packed granule (stellate) cells
- Small pyramidal neurons - Internal pyramidal (ganglionic)
- Large pyramidal neurons (Betz cells) - Mutliform (fusiform)
- Modified pyramidal cells (…)
Sensory areas have thicker____ layer;
Motor areas have thicker ____ layer
- Internal granule layer (IV)
- Internal pyramidal layer (V)
Role of layer I (molecular)
INTEGRATION of information from various cortical areas and; modulates activity of deeper layers.
Role of layer II (external granular)
INTEGRATION and processing of sensory information; role in CONNECTING different cortical areas
Role of layer III (external pyramidal)
Sends OUTPUTS to other cortical areas (integration of sensory inputs + coordination of motor outputs)
Role of layer IV (internal granular)
INTERNEURON; integrates sensory inputs from thalamus before being sent to other layers
Role of layer V (internal pyramidal)
Source of UMN; sends outputs to subcortical structures, critical for MOTOR function
Role of layer VI (multiform)
REGULATES FLOW of information between the cortex and subcortical structures.
