<ul><li>Thalamus is a part of diencephalon </li></ul><ul><li>Diecephalon divided into 4 regions </li></ul><ul><li>Thalamus </li></ul><ul><li>Hypothalamus </li></ul><ul><li>Epithalamus </li></ul><ul><li>Ventral thalamus(or subthalamus) </li></ul>
Thalamus <ul><li>Large mass of grey matter,lies immediately </li></ul><ul><li>lateral to third ventricle </li></ul><ul><li>The thalamus is an ovoid nuclear mass, c.4cm long, which borders the dorsal part of third ventricle </li></ul><ul><li>Two poles </li></ul><ul><li>Anterior pole(or end) </li></ul><ul><li>-Lies behind the interventricular foramen </li></ul><ul><li>Posterior pole(or end) </li></ul><ul><li>-Also called PULVINAR </li></ul><ul><li>-Lies just above and lateral to superior </li></ul><ul><li>colliculus. </li></ul>Thalamus
Anterior pole Posterior pole or pulvinar Thalamus Superior colliculus Interventricular foramina Thalamus
<ul><li>Superior(dorsal) surface </li></ul><ul><li>-The superior (dorsal) surface of the thalamus is covered by a thin layer of white matter, the stratum zonale </li></ul><ul><li>-It extends laterally from the line of reflection of the ependyma (taenia thalami), and forms the roof of the third ventricle </li></ul><ul><li>-This curved surface is separated from the overlying body of the fornix by the choroid fissure with the tela choroidea within it. </li></ul><ul><li>-More laterally it forms part of the floor of the lateral ventricle. </li></ul><ul><li>-related laterally to caudate nucleus </li></ul><ul><li>-Seperated from caudate nucleus stria </li></ul><ul><li>terminalis and thalamostriate vein. </li></ul>Superior surface
Superior surface Inferior surface Medial surface Surfaces of the thalamus
The medial surface of the thalamus is the superior (dorsal) part of the lateral wall of the third ventricle. It is usually connected to the contralateral thalamus by an interthalamic adhesion behind the interventricular foramina. The boundary with the hypothalamus is marked by an indistinct hypothalamic sulcus, which curves from the upper end of the cerebral aqueduct to the interventricular foramen. The thalamus is continuous with the midbrain tegmentum, the subthalamus and the hypothalamus Medial surface The medial surface
Medial surface of thalamus Hypothalamus Midbrain tegmentum
Inferior surface of the tegmentum is related to hypothalamus anteriorly and to ventral thalamus posteriorly. The ventral thalamus seperates the thalamus from tegmentum of midbrain Inferior surface of thalamus
Internally, the thalamus is divided into anterior, medial and lateral nuclear groups by a vertical Y-shaped sheet of white matter, the internal medullary lamina Nuclei of the anterior part . Anterior nucleus. Nuclei in the medial part Largest nuclei among them medial dorsal nucleus. Internal structure of the thalamus Thalamus consists of mainly of grey matter Superior surface is covered by a thin layer of white matter called stratum zonale Lateral surface is covered by a similar layer called external medullary layer.
Nuclei in the lateral part Ventral group Lateral group Ventral anterior nucleus Ventral lateral nucleus Or Ventral intermediate nucleus Ventral posterior nucleus Lateral dorsal nucleus Lateral posterior nucleus Pulvinar
Other thalamic nuclei Intralaminar nuclei Embedded within the internal medullary Lamina Midline nuclei Scattered cells between medial part of the thalamus and ependyma of third ventricle. Medial and lateral geniculate bodies Now included under the thalamus.
Connections of the thalamus Afferent impulses from large number of Subcortical centres converge to the thalamus. Visual and aduditory impulses reach the lateral And medial geniculate bodies. Sensation of taste are conveyed to the thalamus Through solitariothalamic fibres Thalamus does not receive direct olfactory impulses They probably reach through amygdaloid complex. Thalamus receive profuse connections from all part Of cerebral cortex,cerebellum and corpus striatum.
Thalamus is there fore regarded as integrating centre Where information of all sources is brought together. The information from thalamus is projected to whole Of the cerebral cortex through thalamo-cortical projection. Thalamocortical fibres form large bundles known as Thalamic radiations or thalamic radiation. Thalamic radiations Superior thalamic radiation (dorsal ) Posterior thalamic radiations ( caudal ) Ventral thalamic radiation
Connection of ventral group of nuclei Most important connection of thalamus are from ventral posterior nucleus Trigeminothalamic tract Solitariothalamic tract Medial leminiscus Spinothalamic tract cerebral cortex (somatosensory area,3 1 2) ventral posterior nucleus medial part lateral part
From globus pallidus From substantia nigra From Cerebellar nuclei Vestibular nuclei Spinal cord Ventral lateral nucleus cerebral cortex premotor and supplementary motor area Area 4 ventral lateral nucleus Anterior part Medial part Posterior part
Superior colliculus & Pretectal area Retina Connection of lateral group of nucleuses cerebral cortex Gyrus cinguli Parahippocampal gyrus Parietal lobe Prefrontal & orbito frontal Temporal Occipital lobe Lateral dorsal Lateral posterior pulvinar
Medial and lateral geniculate bodies are oval Collection of grey matter Situated below the posterior part of thalamus. Traditionally under metathalamus,functionally Under thalamus. The medial geniculate bodies -Relay station of the auditory pathway. -Medial geniculate body recieves fibres of lateral leminiscus. -Fibres arising in the medial geniculate bodies constitute the acoustic radiation. Medial geniculate body
Acoustic area of cerebral cortex Medial geniculate body pulvinar Inferior colliculus Superior olivary nucleus Opposite superior olivary nucleus Inferior brachium Lateral leminiscus Connection of medial geniculate body
<ul><li>Lateral geniculate body </li></ul><ul><li>Relay station for visual pathway </li></ul><ul><li>Recieves fibres from retinae of both the eyes </li></ul><ul><li>Efferent fibres arising in the body constitute </li></ul><ul><li>optic radiation. </li></ul><ul><li>Sections through lateral geniculate body shows </li></ul><ul><li>partially split six lamellae seperated by nerve </li></ul><ul><li>fibres. </li></ul><ul><li>Lateral geniculate body also recieves fibres from </li></ul><ul><li>primary visual cortex.,superior colliculus,and </li></ul><ul><li>from the reticular formation of pons and medulla. </li></ul>Lateral geniculate body
Lateral geniculate body Pulvinar Retina Ipsilateral & Contralateral Visual areas of cerebral cortex Superior colliculus Connections of lateral geniculate body Raphe nuclei Locus coeruleus Other areas in pons & medulla Reticular formation
Blood supply of thalamus Perforating branches of the posterior cerebral artery Posteromedial group(thalamo-perforating arteries) supply medial and anterior part. Posterolateral group ( thalamo-geniculate branches) supply posterior and lateral part of thalamus. Also recieves branches from posterior communicating anterior choroidal,posterior choroidal and middle cerebral artery.
Thalamic syndrome Thalamic syndrome (or thalamic pain syndrome ) is a condition that can be associated with inadequate blood supply from the posterior cerebral artery . Rare neurological disorder in which the body becomes hypersensitive to pain as a result of damage to the thalamus, a part of the brain that affects sensation Primary symptoms are pain and loss of sensation, usually in the face, arms, and/or legs. Pain or discomfort may be felt  after being mildly touched or even in the absence of a stimulus. The pain associated with thalamic syndrome may be made worse by exposure to heat or cold and by emotional distress. Sometimes, this may include even such emotions as those brought on by listening to music. It is also known as "Dejerine-Roussy disease", after Joseph Jules Dejerine and Gustave Roussy