C J Long
Overview of Topics
Functions of the thalamus
- Describe the function of the archithalamic nuclei.
- What are the intrinsic nuclei of the thalamus and how do they function differently from the other groups.
- Describe the primary input from the thalamus to the prefrontal cortex and discuss the function.
- How might the thalamus function as an integrative system similar to the cortex?
(forms 80% of diencephalon)
- Animals with rudimentary cortex;
- Sense of smell;
- Afferents -- reticular formation & limbic system.
- Efferents -- cortical connections & basal ganglia
- Functions as a diffuse thalamic activation system.
- Produces cortical desynchronization.
- Critical for perception of stimuli.
- Decreased activity during sleep.
Preliminary processing of sensory information to cortex.
Two way connections
- Largest division of nuclei
- Projects to association areas of the cortex.
- Larger in animals with well-developed cortex.
- Intrinsic nuclei -- input from other thalamic nuclei.
- Oldest division of thalamus; animals with rudimentary cortex; sense of smell.
- Functions as a diffuse thalamic activation system
- Produces cortical desynchronization
- Critical for perception of stimuli
- Decreased activity during sleep
- Afferents and Efferents
- Afferents-- reticular formation & limbic system
- Efferents--cortical connections & basal ganglia
- Internal medullary lamina - divides medial and lateral segments
Archithalamus has midline connections with:
- Hypothalamus, basal ganglia, amygdala, orbital gyri (diffuse fibers to association cortex)
- Intralaminar (in internal medullary lamina)
- Largest (centrum medianum)
- Receives diffuse spinal and RF connections
- Diffuse cortical projections
- Reticular- lateral to external medullary lamina
- Diffuse efferent system to cortex
- Anteroventral nucleus -- from mammilothalamic tract to cingulate gyrus
- Preliminary processing of sensory information to cortex; two-way cortical connections
- Anterior nuclei--project to geniculate bodies
- Vision and audition
- Have connections with pulvinar
- Accessory arcuate nucleus--taste
- Ventral lateral nucleus
- Fibers from brachium conjunctivium
- Efferents-- internal capsule to motor cortex of precentral area
- Brings cerebellar influence to bear on voluntary motor intentions
- Largest division of nuclei
- Projects to association areas of cortex
- Larger in animals with well-developed cortex
- Intrinsic nuclei--input from thalamus
- Medial nucleus--projects frontal cortex (non-motor)
- Afferents--from ventral nuclei, hypothalamus
- Dorsal lateral nucleus & posterior lateral -- parietal
- Nucleus lateral posterior--parietal and temporal
- Temporal pole area has no thalamic connections
- Receives medial geniculate connections
- Projects to audio-psychic zone of temporal lobe
- Nucleus lateralis dorsalis
- Afferents--somatic sensory nerves
- Efferent--area 7 of parietal lobe
- Afferent--lateral and medial geniculate bodies
- Two-way connection with visuopsychic area
- Ventral anterior nucleus
- From globus pallidus to limbic areas and back
Functions of the Thalamus
- Thalamus and cortex have area-to-area connections
- These connections are usually two-way
- If the thalamus were only a relay, it would be an inconvenient relic
- Transmission of sensory message does not concern the neothalamus
- May play role as a level of sensory integration
Terms to Know
||External medullary lamina
||Intrinsic nuclei of thalamus
||Internal medullary lamina