Anatomy and Physiology of Thalamus
DM input info destination
prefrontal assoc cortex general arousal, modulation of thalmic input to the cortex prefrontal assoc cortex
Thalamus
the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
internal capsule brain
the internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex.
Thalamic projection neurons have Two Physiological States
tonic and busrt mode tonic mode is normal relay and burst mode is innaccuarte one
Medial nuclear group -
Medial nuclear group - mood & emotion
corticalthalmic pathways
from cotrex to thalmus
Anterior -input -info destination
hippocampus mamillary body memory cingulate cortex
VL/VA input: info: destination:
input: basal ganglia, cerebellum info: motor destination: motor cortex
NOTE: pain of face vs. pain of body (trigmeinal pathway vs. DCML) lack of oxygen injury circuit reorganizes abnormally chronic pain Numbness & tingling - blank pathway Temperature - blank pathway Mechanical -blank pathways
...Numbness & tingling - DCML VPL sensory cortex Temperature - spinothalamic VPL sensory cortex Mechanical - DCML, trigeminal VPL & VPM motor cortex
Cerebral cortex receives inputs via:
1. Thalamus sends specific information to restricted cortical areas 2) Diffuse, modulatory inputs that set the general level of excitability of broad cortical areas
has 5 pathways
1. anterior limb 2. genu 3. posterior limb 4. sunlenticula part 5. retrolenticular part
Almost all thalamic nuclei have rich reciprocal connections with the
Almost all thalamic nuclei have rich reciprocal connections with cerebral cortex
Anterior nuclear group -
Anterior nuclear group - part of limbic sys
LGN -Input -Info -Destination
CN II Vision Calcarine sulcus (visual cortex)
dorsomedial nucleus
Controls aggression; animal instincts
GABAergic
Describing neurons or synapses that produce and release gamma-aminobutyric acid.
Thalamic association nuclei Receives information from the association cortex, and distribute it back to association cortex
Dorsomedial nuclei Pulvinar
Clinical Research
ET is the most common motor disease. It affects activities of daily living and is a prominent public health issue.
A fundamental difference between pathways entering the cortex and pathways leaving the cortex
Efferent pathways (e.g., the corticospinal, corticobulbar and corticopontine tracts) can go directly from the cortex to their destinations. They DO NOT go through the Thalamus
Afferent vs. efferent pathways
Efferent pathways carry signals away from the central nervous system. Essentially, they are signals that your brain sends to tell your body to do something, like blinking. Afferent signals come from outside stimuli and tell your brain what they are sensing, such as temperature.
Intralaminar nuclei -
Intralaminar nuclei - cerebral cortex activation
cingulate gyrus
It receives inputs from the thalamus and the neocortex, and projects to the entorhinal cortex via the cingulum. It is an integral part of the limbic system, which is involved with emotion formation and processing,[1] learning,[2] and memory.[3][4] The combination of these three functions makes the cingulate gyrus highly influential in linking motivational outcomes to behavior (e.g. a certain action induced a positive emotional response, which results in learning).[5] This role makes the cingulate cortex highly important in disorders such as depression[6] and schizophrenia.[7] It also plays a role in executive function and respiratory control.
Largely similar circuits: Start - blank Intermediate centers - e.g. blank Thalamus - specific blank Neocortex -
Largely similar circuits: Start - activation of peripheral sensory receptors Intermediate centers - e.g. brainstem Thalamus - specific nucleus Neocortex - specific region & specific layers
Burst mode
Long refractory period of calcium channels Reduction in action potentials May underlie absence epilepsy
Blood Supply anterior IC
MCA AND ACA branches (lenticulostriate branches and recurrent a of heubner
posterior interior capsule
MCA and ICA branches (lenticulostriate branches and anterior choroid artery)
Note: reticular nucleus is blank and DOES NOT project to cortex. All other nuclei are blank and project to the cortex.
Note: reticular nucleus is GABAergic and DOES NOT project to cortex. All other nuclei are glutaminergic and project to the cortex.
Functional Overview
Nuclei that transmit general and special sensory information corresponding to regions of sensory cortices Nuclei that receive impulses from cerebellum and basal ganglia and interface with motor regions of frontal lobe Nuclei that have connections with associate and limbic areas of cerebral cortex
Blood Supply to the Thalamus just one
Posterior Cerebral Artery: small branches supply most of the thalamus Posterior communicating artery Anterior choroidal artery: lateral geniculate body
Reticular nucleus -
Reticular nucleus - receives collaterals from thalmocortical and corticothalamic fibers
Thalamus Reticular Nucleus
Samples the activity in fibers Sends inhibitory (GABA) projections back to adjacent parts of the thalamus. Directs attention sleep-wakefulness cycles thalamic reticular nucleus is part of the ventral thalamus that forms a capsule around the thalamus laterally. However, recent evidence from mice and fish question this statement and define it as dorsal thalamic structure.[1][2] It is separated from the thalamus by the external medullary lamina. Reticular cells are GABAergic, and have discoid dendritic arbors in the plane of the nucleus.
thalamic nuclei
Size of Sensory Thalamic Nuclei. The thalamus is a neural structure found in all vertebrates, located at the dorsal end (top) of the brain stem. It consists of 30 to 40 "nuclei", or interconnected groups of neurons. "Sensory" thalamic nuclei connect sensory input to the cerebral cortex.
MGN -Input -Info -Destination
Superior olive and inferior colliculus of tectum Hearing Auditory cortex of temporal lobe
Ventral/Posterior Thalamic Lesions and Central Post Stroke Pain Syndrome(Dejerine-Roussy syndrome) (vpl injury) what would happen?
Syndrome of neuropathic pain due to thalamic lesions. Occurs in ~10% of stroke patients Initially paresthesias (numbness & tingling) Followed in weeks to months by allodynia (ordinarily painless stimuli cause pain) Pain described as temperature (hot, burning, cold) Pain described as mechanical sensation (dull, aching, squeezing)
Thalamus is divided into 3 principal nuclear masses (blank, blank, blank) by the internal medullary lamina (also contains intralaminar nuclei)
Thalamus is divided into 3 principal nuclear masses (anterior, medial, lateral) by the internal medullary lamina (also contains intralaminar nuclei)
Thalamus is the largest component of blank, lies between brainstem & cerebral hemisphere
Thalamus is the largest component of diencephalon, lies between brainstem & cerebral hemisphere
genu
The genu is the flexure of the internal capsule. It is formed by fibers from the corticonuclear tracts. The fibers in this region are named the geniculate fibers; they originate in the motor part of the cerebral cortex and after passing downward through the base of the cerebral peduncle with the cerebrospinal fibers, undergo decussation and end in the motor nuclei of the cranial nerves of the opposite side. It contains the corticobulbar tract, which carries upper motor neurons from the motor cortex to cranial nerve nuclei that mainly govern motion of striated muscle in the head and face.
Thalamic nuclei: Lateral group
The lateral division is divided into several nuclei.
reticular nucleus
The thalamic reticular nucleus is part of the ventral thalamus that forms a capsule around the thalamus laterally. However, recent evidence from mice and fish question this statement and define it as dorsal thalamic structure.[1][2] It is separated from the thalamus by the external medullary lamina. Reticular cells are GABAergic, and have discoid dendritic arbors in the plane of the nucleus. Input and output. The thalamic reticular nucleus receives input from the cerebral cortex and dorsal thalamic nuclei. Most input comes from collaterals of fibers passing through the thalamic reticular nucleus. ... Its function is modulatory on signals going through thalamus (and the reticular nucleus).
Thin blank nucleus lies on lateral aspect of thalamus
Thin reticular nucleus lies on lateral aspect of thalamus
VPL -Input -Info -Destination
VPL Spinothalamic & dorsal columns/medial lemniscus Pain, temperature; pressure, touch, vibration, proprioception Somatosensory cortex
VPM -Input -Info -Destination
VPM Trigeminal & gustatory pathway Face sensation, taste Somatosensory cortex
pulvinar nucleus
a mass of neurons in the posterior thalamus that have widespread reciprocal connections with areas across the cerebral cortex
Relay nuclei
a nucleus of the brain that serves primarily to relay stimuli from lower receptor centers to coordinating cortical centers -Anterior nuclei (A/LD) -Ventral anterior, ventral lateral nuclei (VA/VL) -ventral posterolateral (VPL) -Ventral posteromedial (VPM) -Medial Geniculate (MGN) -Lateral Geniculate (LGN)
anterior limb of internal capsule orgin and output (has two)
anterior nucleus-> cingulate gyrus MD-> prefrontal cortex
Thalamocortical pathways
auditory receptors in cochlea-> brain stem neurons-> MGN-> Auditory cortex or photoreceptors in eye-> other retinal neurons lgn-> visual cortex
Dicenphalon
composed of: thalmus, hypothalmus, epithalmus
Sublenticular
lgn->visual cortex (optic radiation) mgn->auditory cortex (auditory radiation)
Lateral nuclear group function
located ventrally; general and special senses
Posterior limb orgin and outputs
motor cortex-> spinal cord (corticospinal tract) motor cortex -> brainstem (coricobulbuar and corticopontine tract) vpl/vpm-> postcentral gyrus (somatosensory radiation)
Pulvinar input and output
parietal, occipital, temporal assoc cortex general arousal modulation of thalmic input to cortex parietal, occipital, temporal assoc cortex
retrolenticular
pulvinar-> association cortex lgn->visual cortex (optic radiation)
Association nuclei
receive specific inputs mainly from association cortex, and project back to related areas of association cortex. -Dorsomedial (DM) -Pulvinar (P/LP)