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Ch008_NC22.qxd 20/12/06 12:44 PM Page 137 CHAPTER 8 Thalamus Thalamus In Situ 138 Thalamic Nuclei 139 Thalamus in Horizontal Section 141 Thalamus in Coronal Section 142 Ch008_NC22.qxd 16/12/06 3:08 PM Page 138 8 Thalamus THALAMUS IN SITU Location Paired, medially placed, deep egg-shaped nuclear structures that form part of the lateral wall of the 3rd ventricle Architecture Composed of multiple nuclei, which receive input from many cortical and subcortical structures Function Functions as the “gateway to the cortex.” Sensory input, other than olfaction, relays through the thalamus before reaching the cortex. All output to the cortex from the cerebellum and basal ganglia relays through the thalamus. The thalamus also relays limbic input to the cortex Clinical Significance Due to its multiple functions, damage to the thalamus can cause many problems, including sensory abnormalities, visual-field deficits, and behavioral changes Lesions to the sensory area can cause numbness on the contralateral body and face Interventricular foramen Corpus callosum (cut) Head of caudate nucleus 3rd ventricle Choroid plexus Internal cerebral v. Superior thalamostriate v. (vena teminalis) Pes hippocampi Inferior horn of lateral ventricle Dentate gyrus Collateral eminence Hippocampus Fimbria of hippocampus Septum pellucidum Columns of fornix Anterior tubercle Stria terminalis Interthalamic adhesion Stria medullaris Habenular tribone Pulvinar (lifted) Lateral geniculate body Medial geniculate body Brachium of superior colliculus Posterior commissure Habenular commissure Pineal gland Collateral trigone Brachium of inferior colliculus Superior colliculus Inferior colliculus Cerebellum Calcar avis Posterior horn of lateral ventricle Calcarine sulcus (fissure) 138 NETTER’S CONCISE NEUROANATOMY Ch008_NC22.qxd 16/12/06 3:08 PM Page 139 Thalamus THALAMIC NUCLEI • The thalamus is composed of many nuclei, which have motor, sensory, and limbic connections. • Some nuclei are nonspecific in nature. NUCLEUS INPUT(S) OUTPUT(S) FUNCTION Sensory Nuclei Ventroposterolateral (VPL) Spinothalamic tract Medial lemniscus Primary sensory cortex Somatic sensation for contralateral body Ventroposteromedial (VPM) Trigeminothalamic tract, pontine taste area Primary sensory cortex Somatic sensation for contralateral face, taste Medial geniculate (MGN) Brachium of the inferior colliculus Primary auditory cortex Hearing Lateral geniculate (LGN) Optic tract Primary visual cortex Vision Pulvinar Lateral geniculate body (LGB), medial geniculate body (MGB), superior and inferior colliculi Visual association cortex Visual processing Motor Nuclei Ventrolateral (VL) Cerebellum and basal ganglia Primary motor cortex Modulation and coordination of movement Ventroanterior (VA) Basal ganglia Premotor cortex Initiation and planning of movement Ventrointermedial (VI) Cerebellum Primary motor cortex Coordination of movement Limbic and Nonspecific Projection Nuclei Anterior (Ant) Mammillothalamic tract Cingulate cortex Memory storage and emotion Mediodorsal (MD) Temporal lobe, amygdala, hypothalamus Prefrontal cortex Motivation, drive, emotion Centromedian (CM) Slow pain pathways Nonspecific cortical projections Emotional content of pain NETTER’S CONCISE NEUROANATOMY 139 8 Ch008_NC22.qxd 16/12/06 3:08 PM Page 140 8 Thalamus THALAMIC NUCLEI continued Thalamocortical radiations Central sulcus CM LD LP MD VA VI VL VPL VPM Centromedian Lateral dorsal Lateral posterior Medial dorsal Ventral anterior Ventral intermedial Ventral lateral Ventral posterolateral Ventral posteromedial Internal medullary lamina Intralaminar nuclei Anterior nuclei Other medial nuclei Midline (median) nuclei MD Interthalamic adhesion LD LP VA Pulvinar VL VI CM VPL From globus pallidus and substantia nigra Reticular nucleus (pulled away) Acoustic pathway From cerebellum Somesthetic from body (spinothalamic tract and medial lemniscus) 140 NETTER’S CONCISE NEUROANATOMY Medial geniculate body VPM Lateral geniculate body Optic tract Somesthetic from head (trigeminal nerve) Ch008_NC22.qxd 16/12/06 3:08 PM Page 141 Thalamus THALAMUS IN HORIZONTAL SECTION • Thalami form the lateral walls of the third ventricle. • Posterior limb of the internal capsule separates thalamus from the lentiform nucleus. • Pulvinar is demonstrated in the artwork below. Frontal lobe External capsule Anterior limb of internal capsule Claustrum Extreme capsule Level of section (head of caudate and mid thalamus) Head of caudate nucleus Genu of corpus callosum Genu of internal capsule Insular cortex Anterior horn of lateral ventricle Posterior limb of internal capsule Transverse temporal gyrus of Heschl Auditory radiations Tail of caudate nucleus Temporal lobe Optic radiation Temporal pole of lateral ventricle Choroid plexus Fimbria of fornix Occipital lobe Columns of fornix Third ventricle Globus pallidus Putamen Splenium of the corpus callosum Thalamus Pulvinar NETTER’S CONCISE NEUROANATOMY 141 8 Ch008_NC22.qxd 16/12/06 3:08 PM Page 142 8 Thalamus THALAMUS IN CORONAL SECTION STRUCTURE ANATOMIC NOTES FUNCTIONAL SIGNIFICANCE Thalamus Individual nuclei are anatomically separated. The thalamus defines the borders of the 3rd ventricle LGN of the thalamus Comma-shaped, lateral nucleus of the thalamus Serves as the visual relay center from the optic tract to occipital cortex. Lesions can cause visual field defects MGN of the thalamus Medial to the lateral geniculate nucleus Serves as the auditory relay center from the inferior colliculus to auditory cortex MDN of the thalamus Most dorsal and medial nucleus; forms part of the wall of the 3rd ventricle Part of the limbic system CM thalamus Located ventral to the MDN Involved in the central modulation and perception of pain Lateral thalamus Contains multiple nuclear structures, including the VL and VPL Involved in motor and sensory relays 142 NETTER’S CONCISE NEUROANATOMY Ch008_NC22.qxd 16/12/06 3:08 PM Page 143 Thalamus THALAMUS IN CORONAL SECTION continued Body of corpus callosum Cingulate cortex Interventricular foramen of Monro Columns of fornix Third ventricle Body of lateral ventricle Cingulum Stria terminalis Body of caudate nucleus Level of section (midthalamus) Medial dorsal thalamus Insular cortex Lateral thalamus Lateral geniculate nucleus Centromedian thalamus Tail of the caudate nucleus Hippocampal formation Medial geniculate nucleus Cortex of cerebellum Entorhinal cortex Superior cerebellar peduncle Pons (floor of fourth ventricle) Inferior cerebellar peduncle Medulla NETTER’S CONCISE NEUROANATOMY 143 8 Ch008_NC22.qxd 16/12/06 3:08 PM Page 144