Thalamus Flashcards
what vesicle makes up the thalamus?
the diencephalon
most caudal of the proencehalon (dien and telen)
how many neurons are in the thalamus?
about 10 million neurons in each half
broken into 50-60 nuclei
what are the 4 parts that make up the thalamus?
1- epithalamus
2-subthalamus
3-hypothalamus
4-dorsal thalamus
what are the new positional terms at this level?
anterior= rostral
posterior= posterior
dorsal=superior
ventral=inferior
what is the epithalamus?
what does it constitute?
what structures lie within it?
roof of the 3rd ventricle
structures comprising it constitute a linkage between limbic system components in the forebrain and other parts of the brain
habenular trigone and nuclei
pineal body
striate medularis
what is the pineal body responsible for?
secretion of melatonin which is important in:
- regulating sleep/wakefulness cycle
- sexual maturity (onset of puberty)
- mating season (animals)
what is the habenula?
a nucleus that projects to the midbrain and is thought to be involved in releasing neuromodulators, such as dopamine, norepinephrine, and serotonin
what is the subthalamus?
what is the bulk of the subthalamus made up of?
border between thalamus and midbrain just rostral to substangia nigra
this part of the diencephalon is wedged laterally between the thalamus and the hypothalamus
the bulk of the subthalamus is made up of the sub thalamic nucleus and another gray matter component is the zone incerta. There are also several fiber bundles in the subthalamus:
- subthalamic fasciculus
- lenticular fasciculus
- ansa lenticularis
what is the subthalamus important for?
important for regulating movements produced by skeletal muscles
it is interconnected with other structures important in movement: basal ganglia and substantia nigra
what is the name of a lesion at the subthalamus?
hemiballisums
basically person flails extremities uncontrollably
can be dangerous to work with patient because of this
what is the hypothalamus?
head of autonomic endocrine and limbic system
involved in homeostatic control
does this by means of its neuroendocrine role in conjunction with the pituitary gland as well as by its influence on the autonomic NS, which helps regulate body temperature, the cardiovascular system, and food and water intake
it is an integral component of the limbic system
what is the dorsal thalamus?
robin’s egg
refer to this as the thalamus
general characteristics of the thalamus:
how long?
formed by what plates?
~ 3 cm long (ant-post)
1.5 cm ventral to dorsal
formed by the ALAR plates- primarily sensory but has some motor nuclei
all sensations go to thalamus before cerebrum
what are the 2 regions of the thalamus?
Allothalamus:
- afferents from amygdala
- centre-median parafascicular complex (BG)
- intralaminar region
Isothalamus:
-bulk of the thalamus
what are the functions of the thalamus?
relay and integration of sensory information
effects consciousness and helps with focusing of attention
relay and integration of motor information
what are the motor relay nuclei?
ventral anterior (BG project here??)
ventral lateral (cerebellum projects here??)
what are the sensory relay nuclei?
ventral posterior (VPL- spinothalamic tracts (fast/primary pain; medial lemniscus- discriminative)
arcuate nucleus (VPM- VTTT discrim, P&T face)
lateral geniculate- vision
medial geniculate- hearing
what are the limbic relay nuclei?
anterior
(memory and attention?)
(related to emotion and behavior)
what are the features (characteristics) of the relay nuclei?
convey information to cerebral cortex
receive direct inputs from long ascending tracts (spinothalamic, medial lemniscus, optic tract, auditory)
process info derived from basal ganglia, cerebellum (motor)
anterior- limbic system
all have reciprocal connections (loops) with well defined cortical areas (except reticular thalamic nuclei) (cortex says what it wants and how it wants it)
they undergo degeneration on ablation of the specific cortical area to which they project
what separates the R and L halves of the thalamus?
what forms the roof of the 3rd ventricle?
3rd ventricle
tela choroidea- bears a choroid plexus
what joins the 2 halves of the thalamus?
massa intermedia or interthalamic adhesion
what is the internal medullary lamina?
band of myelinated fibers subdivides the thalamus of each hemisphere into 3 unequal parts :
medial and lateral nuclear groups from the ventral nuclear group and bifurcates at its rostral extent to encompass an anterior nuclear group.
what forms the lateral wall of the thalamus?
a thin sheet of cells called the thalamic reticular nucleus
this group of cels separates the lateral group of nuclei from the posterior limb of the internal capsule
what lies adjacent to the 3rd ventricle on the medial wall of the thalamus ?
narrow band of cells making up the midline nuclei resides on the medial wall of the thalamus
what does the thalamus serve as?
station for processing and relaying neuronal activity from all types of peripheral sensory receptors, from the basal ganglia, and from the cerebellum to the cerebral cortex
with the exception of the reticular nucleus, all the thalamic nuclei project to the :
cerebral cortex (thalamocortical fibers) and receive afferents (corticothalamic fibers) from the same cortical region to which they project
midline, anterior and medial nuclei of the thalamus interconnect with:
the limbic and paralimbic cortical areas as well as the heteromodal regions of the prefrontal cortex
the ventral thalamic nuclei project in :
rostrocaudal order to the modality-specific areas of the : frontal lobe( motor cortex) parietal lobe (somatosensory, taste & vestibular) temporal lobe (auditory cortex) occipital lobe (visual cortex)
the nuclei of the lateral nuclear group reciprocate connections with:
the heteromodal cortex of the posterior parietal and temporal lobes and the unimodal association cortex for vision
the VPL and arcuate nuclei project to :
the primary somatosensory cortex
areas 1-3- postcentral gyrus
**thalamus perceives pain- don’t necessarily need cerebral cortex to feel pain
what does the medial geniculate control?
where does it project to?
pathway for hearing
receives auditory stimulus from both ears and relays to primary auditory cortex (area 41)
cochlear nuclei go up ipsilat and contralto via trapezoid and ventral/dorsal striae –> synapse on inferior colliculus via lateral lemniscus to medial geniculate via brachium of inferior colliculus
then relayed to primary auditory cortex which is on supra temporal gyrus (fushia)
what does the lateral geniculate control?
where does it project to?
pathway for vision
optic nerve coming from retina in the eye
eyes care about visual fields so both eyes work together.
optic nerves come together around pituitary, forms optic chiasm where only half fibers cross, optic tracts see contralateral visual cortex on either side of calcimine sulcus
what do the motor nuclei project to?
ventrolateral: cerebellum via dentothalamic tract; overlaps with BG
Ventroanterior: relays neocerebellum info to primary motor cortex in general (precentral gyrus/area 4) initiates movement (trajectory and forces)
where does the basal ganglia project to?
ventroanterior and ventrolateral (motor) nuclei
relays up to association cortex (premotor area/area 6) (anterior to precentral gyrus)
what are the thalamocortical radiations?
central (superior)
optic
auditory
anterior
??? slide 12
what is the principal thalamic relay nucleus for somatosensory pathways?
receives?
projects?
VENTRAL POSTERIOR LATERAL NUCLEUS (VPL)
receives info from the medial lemniscus (dorsal columns) and the spinothalamic tract
VENTRAL POSTERIOR MEDIAL NUCLEUS (VPM)
receives info from the trigeminothalamic tract
BOTH project to somatosensory cortex (1,2,3) of the postcentral gyrus
what is the nucleus of the visual pathway?
receives?
projects?
lateral geniculate body
ipsilat & contralateral retina, Raphe nuclei, Locus coeruleus, other areas of the pons & medulla, and the superior colliculus send info to the lat geniculate
the lat geniculate projects to the pulvinar nucleus, visual areas of the cerebral cortex, the superior colliculus and other areas of the pons && medulla
what is the nucleus of the auditory pathway?
receives?
projects?
medial geniculate pathway
receives from the inferior colliculus
projects to the auditory cortex (area 41
what nucleus is responsible for planning and modulation of commands?
receives?
projects?
the ventral lateral nucleus (motor)
receives info from:
anterior: the ipsilateral globus pallidus
Medial: substantial nigra, contralateral dentate nucleus, spinothalamic tract & vestibular nuclei, pre central motor cortical area
projects into to the primary motor cortex (pre central gyrus, area 4)
supplementary motor area
what nucleus influences motor activity?
receives?
projects?
ventral anterior nucleus (motor)
receives info from ipsilateral globes pallidus & substantial nigra, premotor cortex, and frontal eye field
projects to premotor and supplementary motor cortex
what nucleus is responsible for control and alertness, attention and acquisition of memory?
receives?
projects?
anterior nuclear system- functionally part of the limbic system
receives info from maxillary body of hypothalamus via mammillothalamic tract
projects to anterior limbic area, cingulate gyrus, parahyppocampal gyrus
what are association nuclei?
multimodal- don’t receive anything specific by a modality- gets inputs indirectly from many areas- project to association cortical areas
1-dorsomedial?
2- pulvinar
3-lateral posterior
what nuclei constitute the dorsal tier lateral nuclear group?
lateral dorsal
lateral posterior
pulvinar
what nucleus is responsible for memory, and interpretation of visual stimuli?
receives?
projects?
lateral dorsal nucleus
receives info from happocampal formation, pretectal area, superior colliculus
projects to the cingulate gyrus and the visual association cortex
what nucleus is responsible for interpretation of visual and other sensory stimuli?
receives?
projects?
lateral posterior nucleus
forms complex links- subcortical visual areas with association cortical visual area
receives info from the superior colliculus
projects to the parietal, temporal and occipital association cortex
what nucleus is responsible for visual and preceptive cognition and memory?
receives?
projects?
pulvinar nucleus -vision
receives from pretectal area, superior colliculus, retinas
projects to association area of parietotemporal cortex and visual areas in occipital and post temporal lobe
lesions of the lateral posterior and pulvinar nuclei affect:
spatial relations- results in neglect
you see L visual field but don’t attend to it
what nuclei constitute the medial nuclear group?
MEDIODORSAL NUCLEUS - prefrontal cortex (frontal lobes)
Parvo cellular
- affective behavior, memory and integration of somatic visceral activities
- lesion- flat emotional state; transient memory loss; anterograde amnesia
Magno cellular
-relay-smell
what nucleus is responsible for the integrating emotion, thought and judgement?
receives?
projects?
mediodorsal nucleus
receives info from the hypothalamus, amygdala, other thalamic nuclei, and the prefrontal cortex
projects to the prefrontal cortex, post parietal cortex and the limbic structures
what are the non-specific nuclei?
Reticular nuclei
Intralaminar nuclei
Midline nuclei
what are characteristics of non-specific nuclei?
diffuse and widespread indirect cortical projections
input from RF and other areas of neural axis
regulate consciousness, arousal and attention
what nuclei is responsible for cortical activation and sensorimotor integration?
receives?
projects?
intralaminar nuclei
ARAS= anterior reticular activating system
cortical AROUSAL and focusing attention
receives info from the BS RF, spinothalamic tract, cerebellar nu, palladium
projects to the frontal and parietal lobes, striatum
what nuclei are part of the limbic system and is responsible for memory and arousal?
receives?
projects?
Midline nuclei
receives info from the BS RF, hypothalamus, spinothalamic tract, midbrain
projects to the hippocampal formation, amygdala, nucleus accumbens, cingulate gyrus
what nuclei are responsible for inhibitory modulation of thalamocortical transmission?
reticular nuclei
receives info from collaterals of thalamocortical, corticothalamic, thalamostriatal, pallidothalamic fibers
projects to the body of the thalamus
what is the only thalamic nucleus that does NOT project to the cerebral cortex ??
what is its function?
reticular nuclei
instead of working as a loop (like the others) it modulates the information from other nuclei in the thalamus
function= modulatory on signals going through thalamus
what is the result of a bilateral loss of intralaminar nuclei?
causes a vegetative state where you are not attentive
what are the 4 major arteries that supply the thalamus?
FROM THE POSTERIOR CEREBRAL A:
1-thalamoperforating A- supplies anterior
2- thalamogeniculate A- supplies posterior lateral and geniculate nuclei
3- posterior choroidal A- posterior aspect (medial pulvinar, post/lat/med nuclei)
FROM THE POSTERIOR COMMUNICATING A:
4- Tuberothalamic A (Polar A)- lateral anterior of thalamus (ventral anterior nucleus)
only 66% of people have this
what deficits would occur with a dorsal thalamus pathology to the anterior area?
what artery would that involve?
tuberothalamic A
wide-ranging neuropsyychological deficits
personality changes- withdrawn, disorientation in time and place, euphoria, lack of insight, apathy etc.
impairment of recent memory, new learnings and disoriented
12% of thalamic infarcts
missing in 1/3 of people
acts like there is a confusion of ideas but they are not confused
what deficits would occur with a dorsal thalamus pathology to the paramedian area?
what areas would it affect?
35% of thalamic infarcts
dorsomedian nucleus (amygdala, intralaminar nucleus)
neuropsychological disturbances- primarily in arousal and memory
confusion, agitation, aggression and apathy
speech problems- hypophnia (soft speech) dysprosody (difficulties in pitch or timing control)
(like schizophrenics- fluctuations b/w periods of hyperactivity and periods of lack of spontaneity- sometimes can be like a zombie, sleeping and eating excessively, manic, crying, labile, crazy ideas
what deficits would occur with a dorsal thalamus pathology to the inferolateral area?
what artery would it affect?
thalamogeniculate arteries
ataxia (VA, VL) somatosensory sensations (VP)
45% of thalamic infarcts
can retain pain- may even be excruciating
what deficits would occur with a dorsal thalamus pathology to the posterior area
Pulvinar
8 % of thalamic infarcts
hypoesthesia (decreased sensitivity to light and other sensations)
spatial neglect
homoonymous horizontal sectoranopsia (lat geniculate)
-loss of vision in a portion of the visual field
what is thalamic syndrome?
(Dejerine Roussy)
blockage in thalamogeniculate branch going to postero-ventral part of the thalamus
what are the symptoms of thalamic syndrome?
commonly preceded by numbness in the affected side
numbness is replaced by burning and tingling sensations widely varying in degree of severity
symptoms can be severe and debilitating
burning and tingling can also be accompanied by hypersensitivity, usually in the form of dysaesthesias or allodynia
less commonly, some patients develop severe ongoing pain with little or no stimuli
can have motor problems
what comprises the anterior limb of the internal capsule?
corticopontine 1 fibers (fronto-pontine-cerebellum)
anterior thalamic radiation (from the thalamus projects to cortex (mostly prefrontal- involved with cognitive behaviors, decision making, etc)
frontopontine and other corticofugal fibers
what comprises the posterior limb of the internal capsule?
corticopontine 2 fibers (all other lobes-pons-cerebellum)
corticopontine and other corticofugal fibers
superior thalamic radiation (includes somatosensory radiation)
corticospinal tract
what are corticofugal fibers?
fibers returning from the cortex to the thalamus
fugal = leaving cortex
everything thalamus sends to the cortex gets sent back
what are the 4 thalami cortical radiations?
central (superior) = sensory
optic
auditory
anterior (motor)
