thalamus

nonspecific nuclei

project quite broadly through the cerebral cortex, may be involved in general functions such as arousal and alertness

nonspecific thalamic nucleus

thalamic reticular nucleus; part of ventral thalamus that forms a capsule around the thalamus laterally

diencephalon consists of the

thalamus and hypothalamus

vegetative (awareness) function

the thalamus has some intrinsic nuclei associated with alertness and arousal; can be associated with disorders of consciousness

what are the two basic physiological state of thalamic projection?

tonic mode: neurons respond like other neurons to depolarization and hyperpolarization burst mode or oscillatory mode: neurons in this state have an intrinsic rhythmicity

ventral posteromedial nucleus

trigeminothalamic (face) to somatosensory cortex

ventral posterolateral nucleus

spinothalamic (body) to somatosensory cortex

thalamic syndrome

a cerebrovascular accident (stroke) can lead to the thalamic syndrome, which involves a one sided burning or aching sensation often accompanied by mood swings

korsakoff's syndrome

a chronic memory disorder caused by severe deficiency of thiamine; commonly caused by alcohol misuse; stems from damage to the mammilary body, the mamillothalamic tract or limbic specific nuclei of the thalamus (dorsomedial nucleus or anterior group)

sensory fxn

all sensory info except olfaction is relayed to cortex via thalamus

thalamic reticular nucleus cells

are GABAergic interneurons mostly; makes a strongly inhibitory input to thalamic nuclei - fire tonically when we are awake, but fire rhythmic high frequency bursts when we are sleeping

thalamic nuclei project primarily to the

cerebral cortex, exception: reticular thalamic nucleus

medial geniculate inputs from: projects to:

cochlea, auditory primary auditory cortex

internal organization of the thalamus composed of

composed of grey matter; vertical sheaths of white matter (medullary laminae) and contains thalamo-cortical and cortico-thalamic fibers

DBS

deep brain stimulation; electrodes in the ventro lateral nucleus have been used to treat parkinsonian and essential tremor, dystonia, pain, epilepsy, essential tremor, and manifestations of gilles de la tourette's syndrome

external medullary lamina

located laterally; separates reticular nucleus from rest of thalamus

types of specific relay nuclei

medial geniculate, lateral geniculate, ventral posterolateral nucleus, ventral posteromedial nucleus, ventral lateral nucleus, ventral anterior nucleus

motor function

motor system outputs from basal ganglia and cerebellum are relayed by thalamus

emotion/memory function

part of papex/limbic circuit that helps control some emotional and memory info going to limbic cortex (cingulate gyrus)

association thalamic nuclei

pulvinar, lateral posterior nucleus, mediodorsal nucleus, lateral dorsal nucleus, anterior thalamic nuclei - much more complex info coming in and going out *located in medial portion

association nuclei

receive most of their input from the cerebral cortex and project back to the cerebral cortex where they appear to regulate activity

relay nuclei

receive very well defined input and projects this signal to functionally distinct areas of the cerebral cortex

each portion of the thalamus receives a --------- from the same portions of the cerebral cortex

reciprocal connection; gives ability of cortex to modify thalamic functions and provide a mechanism for filtering thalamic inputs to the cerebral cortex

thalamus is the primary site of

relay for all of the sensory pathways to the cerebral cortex except olfactory signals which reach the thalamus via indirect connections

types of thalamic nuclei

relay, association, nonspecific

lateral geniculate nucleus inputs from: projects to:

retina primary visual cortex

functional roles of thalamus

sensory, motor, emotion/memory, vegetative

internal medullary lamina

separates medial, lateral and anterior nuclei