Flashcards in Thalamus Deck (18)
Describe the basic pathway of sensory information to the thalamus.
1. Information gets collected
2. Collected and transmitted
3. Looked at analyzed
(See slide 4)
Describe sensory input to the thalamus involving the cerebral cortex, cerebellum, brainstem, and basal ganglia
See slide 9.
Describe the divisions of the diencephalon.
-Epithalamus (pineal gland, habenular, stria medullaris-fibers from the globus pallidus and limbic strcutres; major input bundle to the habenula and allows basal ganglia and limbic system to influce the brainstem reticular formation)
-Subthalamus (subthalamic nucleus, zona incerta- rostral continuation of the midbrain reticular formation)
Describe the Dorsal thalamus.
Internal medullary lamina- (myelinated fibers) divides the thalamus:
anterior division nuclei, medial division nuclei, lateral division nuclei (dorsal and ventral tier)
Intralaminar nuclei - embedded in the internal medullary lamina
Thalamic reticular nuclei- partially surrounds the thalmus
Midline nuclei- cover the ventricular surface of the thalmus (rostral continuation of the periaqueductal gray)
Label the brain on slide 11, 12, 13.
What is the thalamus near?/What does it form?
Slides 11, 12, 13.
Forms wall of 3rd ventricle
Describe the common functional principles of the thalamus.
(cerebral cortex is important for the proper functioning of the sensory system in humans)
-Thalamic nuclei "decide" what information passes (all thalamic nuclei, except reticular nucleus) are variations of the theme "decide" what info should reach cerebral cortex for further analysis
-Classification of nuclei- location and input/output
-Consists of projection (majority) and inhibitory neurons (GABAergic)
-Inputs into the thalamus (most of specific inputs to the thalamus use glutamate as a neurotransmitter.) Specific- posterior column/medial lemniscus to VPL nucleus pathway
(Regulatory- Majority/more prominent (cortex, thalamic reticular nucleus, reticular formation, cholinergic, noradrenergic, serotonergic and dopaminergic. aminergic projections))
Describe the three groupings of functional thalamic groups.
Specific or relay nuclei- well defined inputs and projects, anterior, ventral anterior, ventral lateral, ventral posterior, lateral dorsal, medial and lateral geniculate
Association nuclei- reciprocally connected to association cortex, lateral posterior, pulvinar, medial dorsal nuclei
Non-specific nuclei- (intralaminar and midline) not the same point-to-point connections like relay nuclei, Intralaminar and thalamic reticular nuclei
Describe specific or relay nuclei.
Ventral Anterior (VA)
Ventral Lateral (VL)- anterior part
Ventral Lateral (VL)-posterior part)
Ventral posteromedial (VPM)
Ventral posterolateral (VPL)
Medial geniculate body
Lateral geniculate body
Lateral dorsal (LD)
well defined inputs and projections
Anterior - mamillary body, hippocampus/ cingulate gyrus
Ventral Anterior (VA) - basal ganglia (Substantia nigra, pars reticulata)/ prefrontal cortex
Ventral Lateral (VL)- anterior part - basal ganglia (globus pallidus, internal)/ supplementary motor area
Ventral Lateral (VL)-posterior part - cerebellar nuclei/ premotor and motor cortex
Ventral posteromedial (VPM) - somatic afferents from head region / somatic sensory cortex
Ventral posterolateral (VPL) - somatic afferents from trunk and limbs / somatic sensory cortex
Medial geniculate body - brachium of IC / primary auditory cortex
Lateral geniculate body - optic tract and SC? / primary visual cortex
Lateral dorsal (LD) -hippocampus/ cingulate cortex
Describe association nuclei.
Lateral posterior (LP)
Dorsomedial (DM) (or mediodorsal)
reciprocally connected to association cortex
Lateral posterior (LP) and Pulvinar- superior colliculus, primary visual, auditory and somatosensory cortex/ posterior parietal and lateral temporal association cortex
Dorsomedial (DM) (or mediodorsal) - prefrontal cortex, olfactory, limbic / prefrontal cortex
NOT GETTING PRIMARY SENSORY INFORMATION (no primary sensory info coming in)
Describe non-specific nuclei.
Thalamic reticular nuclei
Non-specific nuclei- not the same point-to-point connections like relay nuclei,
Intralaminar - reticular formation, basal ganglia and limbic system / cerebral cortex, basal ganglia and limbic system
Thalamic reticular nuclei - thalamus and cortex / thalamus
Describe the internal capsule.
Describe the interconnections between the thalamus and cerebral cortex and subcortical structures that travel through the internal capsule.
anterior- passes through the anterior limb of the internal capsule to reach the prefrontal and cingulate gyrus
superior- passes through the posterior limb of the internal capsule to reach the premotor, motor and somatic sensory cortex
posterior- passes through the retrolenticular part of the internal capsule to reach the occipital lobes, posterior parietal and temporal
inferior- passes through the sublenticular part of the capsule, below the lentiform nucleus to reach the anterior temporal and orbital cortex
Describe the thalamic nuclei to remember.
Describe the blood supply of the thalamus and internal capsule.
small branches of the posterior cerebral artery provide most of blood to thalamus (small perforating arteries)
small branches of the Middle Cerebral A (lenticulostriate arteries- lateral striate) Anterior Cerebral A (recurrent artery of Heubner (medial striate artery) and the anterior choroidal artery provide most of blood to internal capsule
Describe the vascular (stroke) anatomic lesions and syndromes.
Thalamic region/primary functions
anterior - language (dominant) and memory (polar artery)
lateral - motor and sensory (thalamogeniculate artery)
medial - vigilance, arousal, memory (paramedian artery)
posterior- higher visual (posterior choroidal artery)
Describe intralaminar nuclei.
Project both to cerebral cortex and basal ganglia (rostral extension of the reticular formation)
Describe thalamic reticular nucleus.
projects to other thalamic nuclei and not the cerebral cortex.
The neurons of reticular nuclei are made up of inhibitory GABAergic neurons
All thalamic projection neuron axons will pass through and give off collaterals to this reticular nucleus. The cortical (or other areas) which those thalamic projection axons reach, will send projections back to their specific thalamic nuclei (modulate their firing) but also collateral branches to the reticular nuclei as they pass through it
Primary function of thalamic reticular nucleus is to isolate any novel sensory stimulus from the background ("center-surround" or saliency) and enhances activity in one area of thalamic neurons while inhibiting random activity around them