THALAMUS AND ITS CONNECTIONS PDF

(004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21...

(004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 OUTLINE I. DIENCEPHALON A. Dorsal-posterior Structures 1. Epithalamus 2. Thalamus 3. Metathalamus B. Ventral-anterior Structure 1. Hypothalamus II. GENERAL APPEARANCE of THALAMUS III. ANATOMIC DIVISION of THALAMUS A. Internal Medullary Lamina 1. Anterior Division Figure 1. Pineal Gland 2. Medial Division  3. Lateral Division Thalamus - Oval-shaped structure IV. FUNCTION of the THALAMUS - Located in the Diencephalon A. Sensory Relay  Metathalamus B. Motor Integration (consist of two nuclei; Medial geniculate and lateral geniculate) C. Arousal - Medial geniculate body D. Pain modulation o auditory relay E. Memory & Behavior - Lateral geniculate body V. INPUT to THALAMUS o visual relay VI. PROJECTION from the THALAMUS VII. THALAMUS: VENTRAL-ANTERIOR STRUCTURE A. Axial View  Hypothalamus B. Sagittal View C. Coronal View THE DIENCEPHALON VIII. BLOOD SUPPLY  Epithalamus o Pineal gland o A few nearby structure I. DIENCEPHALON o Unpaired midline structure  Relay between the brainstem & cerebral cortex o Just rostral to superior colliculi (in the brainstem)  A derivative part of the neural tube that give rise to the specifically in the midbrain at the tectum following structures: Epithalamus, Thalamus, Metathalamus, o Looks like a pine cone (“pineal”) Hypothalamus. o Endocrine gland related to seasonal light cycles  On top of the brainstem (Midbrain, Pons, Medulla) where all o Secretes melatonin (regulates the sleep wake the diencephalic structures that will connect the brainstem to cycle), secreted by pineal gland which is located at the cerebral cortex (in between the cerebral cortex and the the top of superior colliculi in the midbrain brainstem) o Above the two superior colliculi DORSAL-POSTERIOR STRUCTURES **NOTE: Superior colliculi is related to vision while Inferior colliculi is  Epithalamus related to hearing. - Habenular nuclei o integrate smell & emotions II. GENERAL APPEARANCE of THALAMUS o whatever you are smelling, there is a reaction  There are two thalami, and one is situated on each side of to the sense of smell the third ventricle. o it attaches emotion to the sense of smell  The anterior end of the thalamus is narrow and rounded and - Pineal gland forms the posterior boundary of the interventricular foramen. o Part of the epithalamus  The medial surface of the thalamus forms part of the lateral o monitors diurnal / nocturnal rhythm wall of the third ventricle and is usually connected to the opposite thalamus by a band of gray matter, the interthalamic connection (interthalamic adhesion). Page 1 of 6 CMED 1B  (004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 III. ANATOMIC DIVISION of THALAMUS iii. Ventral Posterior (VP) = Ventral Posteriolateral (VPL)  Relay between the brainstem & cerebral cortex = Ventral Posteriomedial (VML)  The thalamus is covered on its superior surface by a thin layer of white matter, called the stratum zonale, and on its **NOTE: Remember all of the following because each of these nuclei lateral surface by another layer, the external medullary will have different specific function. lamina.  The gray matter of the thalamus is divided by a vertical sheet  Two Metathalamic Nuclei of white matter, the internal medullary lamina, into medial - Medial Geniculate Nucleus (MGN) and lateral halves. o connected with the auditory pathway  The internal medullary lamina consists of nerve fibers that - Lateral Geniculate Nucleus (LGN) pass from one thalamic nucleus to another. o Associated with the visual pathway  Anterosuperiorly, the internal medullary lamina splits,  Intralaminar Nuclei (located within internal medullary resembling a Y shape. lamina) - Centromedian (CM) INTERNAL MEDULLARY LAMINA - Parafascicular (PF)  Thin sheet of myelinated fibers (tract)  Reticular Nucleus  Divides the thalamus into four major divisions, each - Scattered around the thalamus, in the periphery of the containing specific nuclei: thalamus - Anterior - Nuclei that are connected with the reticular formation in - Medial the brainstem - Lateral and also have a posterior - Part of the ascending reticular system (ARAS) which  Not included in these divisions are makes you awake - The intralaminar nuclei - The reticular nucleus Anterior Medial Posterior Figure 2. Coronal View of Thalamus Thalamus Oval-shaped structure Located in the Diencephalon 1. Anterior Division – contain only one nucleus, (Anterior nucleus) 2. Medial Division – also contain one nucleus, Dorsomedial Nucleus (DM) 3. Lateral Division – the biggest and has a lot of nuclei in it a. Dorsal Tier i. Lateral Dorsal (LD) ii. Lateral Posterior (LP) iii. Pulvinar – is at the most posterior of the lateral Figure 3. Coronal View of Thalamus (zoom) division Pinkish structure is anterior division that contains anterior nucleus. The b. Ventral Tier greenish s the medial portion or the DM or the dorso medial structure i. Ventral Anterior (VA) or nucleus. At the back the pulvinar and the lateral portion. ii. Ventral Lateral (VL) Page 2 of 6 CMED 1B  (004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 IV. FUNCTION OF THE THALAMUS - Inputs from amygdala, olfactory cortex, & basal ganglia  Sensory relay (Something to do with behavior) - ALL sensory information (except smell) - Everything that comes from the periphery of the body  Lateral Division from your hands, from your feet, just like spinothalamic - Biggest portion which controls pain and temperature specifically the - VA (ventral anterior nucleus) and some portions of VL lateral spinothalamic tract, you also have the anterior will receive impulses from substantia nigra, internal spinothalamic from the body which actually sub serves globus pallidus (part of the basal ganglia- control motor live touch, you also have the dorsal column medial movement) lemniscus system which is responsible for pressure, proprioception vibration sense, all of those passes - VL will get information from the deep cerebellar through the brainstem and eventually will connect to the nuclei/cerebellum. The other control system. thalamus before reaching the parietal cortex for the final interpretation of the sensory feeling. - VPL (ventro posterolateral) will receive all the  Motor integration sensations (touch, light touch, deep touch, pressure, proprioception, vibration, pain and temperature) from - Receives input from cortex, cerebellum and basal ganglia. the body, trunk and the leg. - Sense of smell has its own pathway in the cerebral cortex, it’s above the tentorium cerebeli and is a - VPM (ventro postero medial) will get information all the supratentorial structure. sensations coming from the face  Arousal - Pulvinar is related to the superior colliculus that has - Part of reticular activating system (Reticular nuclei will something to do with the vision actually form a part of the ARAS for arousal and wakefulness and modulate pain, It’s connected with all - IN (intralaminar nuclei) will get information from the sensations except for sense of smell.) internal globus pallidus, brainstem, reticular formation - and sensory pathway  Pain modulation - All nociceptive information - MGN (medial geniculate nucleus) to do with auditory  Thalamus has nothing to do with the smell itself except for information the habenular nucleus which is part of the epithalamus and not the thalamus itself. - LGN (lateral geniculate nucleus) something to do with  Memory & behavior visual information - Lesions are disruptive Figure 4. Main Nuclear Divisions of the Thalamus. The posterior portion of the reticular nucleus had been removed. V. INPUT TO THE THALAMUS  Anterior Nucleus - Most anterior portion - Receive input from the mammillothalamic tract and the Figure 5. Different Divisions of the Thalamus. fornix  Dorsomedial Nucleus “MD”  Metathalamus - Vision and Hearing Page 3 of 6 CMED 1B  (004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21  Behavior and emotion - connection with hypothalamus Figure 6. LGN and MGN for Visual and Auditory (encircled)  Sensory relay - Ventral posterior group all; all sensation from body and head , including pain Figure 6.3. Ant (anterior nucleus) and MD (Dorsomedial nucleus). VI. PROJECTION FROM THE THALAMUS  Metathalamus – Vision and Hearing  MGN and LGN - Project to auditory cortex specifically the MGN because it is connected with hearing - LGN will connect with the visual cortex because it’s a visual structure Figure 6.1. Showing the VPL and VPM, which sensations are coming from the body and face.  Motor control and integration Figure 7. Reciprocal Connections between Thalamus and Cortex. Major connections between thalamic nuclei and cortical areas are shown using corresponding colors. (A) Cortex, lateral view.  Sensory relay – Ventral posterior group all; all sensation from body and head, including pain, (see Figure 7). Figure 6.2. Showing the VA (Ventral Anterior nucleus), VLo (Ventral  VPL and VPM Lateral nucleus pars oralis )& VLc (Ventral Lateral nucleus pars - Project to the primary somatosensory cortex caudalis), and In (Intralaminar nuclei). - Brodmann areas 1, 2, and 3 Page 4 of 6 CMED 1B  (004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21  Thalamus  Motor control and integration, (see Figure 7). - In the medial portion  VA and VL - Closely associated with the 3rd ventricle which contains - Projects to motor (area 4) and premotor cortex (area 6) CSF  Behavior and emotion – connection with hypothalamus, (see Figure 7).  Anterior and Dorsomedial nucleus - Connect with the cingulate gyrus that is located in the sagittal portion or the medial portion of the cerebrum. Cingulate cortex is part of the limbic system (5th lobe of the cerebrum) that has something to do with emotion and behavior Figure 8.1. An MRI showing the Thalamus.Pointed by the red arrow. SAGITTAL VIEW Figure 7.1. Reciprocal Connections between Thalamus and Cortex (B) Cortex, medial view. VII. THALAMUS: Figure 8.2. An MRI showing the Pons. Pointed by the red arrow AXIAL VIEW  Descending upper motor neurons  Arrow pointed at the left: CORONAL VIEW - Cerebral peduncle which is part of the midbrain  3RD Ventricle – a narrow, funnel-shaped structure that lies in  Arrow pointed at the right: the center of the brain. - Internal capsule is a fiber tract that separate/divide the diencephalic structures and the basal ganglia into several substructures or subsections. Figure 8. An MRI showing the Cerebral Peduncle (left) and Internal Capsule (right).Pointed by the red arrows. Figure 9. 3rd Ventricle. Pointed by the green arrow. Page 5 of 6 CMED 1B  (004) THALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 Figure 9.2. Dorsomedial nucleus, pointed by blue arrow. VL nucleus pointed by green arrow. Figure 9.1. Cerebral Peduncle pointed by red arrow. Internal Capsule VIII. BLOOD SUPPLY pointed by blue arrow.  VPM (Ventral Posteromedial Nucleus) - Sensations from the face  VPL (Ventral Posterolateral Nucleus) - Sensations from the body  Dorsomedial nucleus (see Figure 9.2)  Blood supply of the Thalamus - Has reciprocal connections to - Comes from deep branches of the posterior cerebral o prefrontal cortex – concerned with judgment, artery decision making, memory and behavior. **NOTE: Lesions on the dorsomedial nucleus will lead to memory loss aside from emotional and behavioral problems  Internal capsule (red arrow)  VL Ventral Lateral Nucleus (green arrow) - Has reciprocal connections with primary motor cortex. - It receives input from cerebellar nuclei  VA nucleus - Receives input from basal ganglia - Contributes to planning and control of movement **NOTE: Basal Ganglia goes to VA, and VL, we are talking about the cerebellum. Figure 10. Blood supply to the brain. Page 6 of 6 CMED 1B