THALAMUS

Thalamus

− Is a large, egg shaped mass of gray matter that forms the major part of the diencephalon

− Joined together by Massa Intermedia or Interthalamic Adhesion (Interthalamic Connection)

egg shaped

Shape of Thalamus

Interventricular Foramen

The Anterior end of the thalamus is a narrow and rounded that forms the posterior boundary of the

Pulvinar

The Posterior end of the thalamus is expanded to form the

Tegmentum

The Inferior surface of the thalamus is continuous with the _____ of the midbrain

Lateral Wall of The Third Ventricle

The Medial surface of the thalamus forms part of the

Interthalamic Adhesion

Other term for Massa Intermedia

Interthalamic Connection

other term for Interthalamic Adhesion

Stratum Zonale

The thalamus is covered superiorly by a thin layer of white matter called the

External Medullary Lamina

The thalamus is covered laterally by

1. Anterior Part

2. Medial Part

3. Lateral Part

The thalamus is subdivided into three main parts:

Anterior part of thalamus

− Contains Anterior Thalamic Nuclei

Anterior Part of Thalamus

− Receive Mamillothalamic Tract from Mammillary Nuclei

Anterior Part of Thalamus

− Also, receive equal connections with the Cingulate Gyrus and Hypothalamus

Anterior Part of Thalamus

Function: concerned with emotional tone and mechanisms of recent memory

Medial Part of Thalamus

− Contains large Dorsomedial Nucleus

− Responsible for integration of large variety of sensory information including, Somatic, Visceral,

Olfactory information.

Dorsal Tier and a Ventral Tier

Division of the Lateral Part of Thalamus

Dorsal (Anterior) Tier Nuclei

• Details of their connections are not clear

• They are known to have interconnections with other thalamic nuclei, parietal lobe, cingulate

gyrus, and occipital & parietal lobes

1. Lateral Dorsal Nucleus

2. Lateral Posterior Nucleus

3. Pulvinar

Nuclei of Dorsal (Anterior) Tier Nuclei

Lateral Dorsal Nucleus

caudal extension of the Anterior Nuclei

Pulvinar

largest part of the thalamus

1. Ventral Anterior Nucleus

2. Ventral Lateral Nucleus

3. Ventral Posterior Nucleus

Ventral Tier Nuclei Consists of the following:

Ventral Anterior Nucleus

- this nucleus is connected to the Reticular Formation, Substancia Nigra, Corpus Striatum, Premotor Cortex as well as to many other thalamic nuclei

- since the nucleus lies on the pathway between the Corpus Striatum and the motor areas of the frontal cortex

Ventral Anterior Nucleus

Function: it influences the activities of the Motor Cortex

Ventral Lateral Nucleus

receive major input from the Cerebellum and minor input from the Red Nucleus

Ventral Lateral Nucleus

Function: it influences motor activity

a. Ventral Posteromedial Nucleus

b. Ventral Posterolateral Nucleus

Ventral Posterior Nucleus is subdivided into:

Ventral Posteromedial Nucleus

- receives the Ascending Trigeminal and Gustatory pathways

- Function: relays common sensations to consciousness

Ventral Posterolateral Nucleus

- receives Ascending Sensory tracts, Medial and Spinal lemnisci

- Function: relays common sensations to consciousness

1. Intralaminar Nuclei

2. Midline Nuclei

3. Reticular Nucleus

4. Medial Geniculate Body

Other Nuclei of The Thalamus

Intralaminar Nuclei

Are small connections of nerve cells within the Internal Medullary Lamina

Intralaminar Nuclei

Receive afferent fibers from Reticular Formation as well as from Spinothalamic and Trigeminothalamic tracts

Intralaminar Nuclei

Influence the levels of consciousness and alertness

Centromedian Nucleus

receives fibers from Globus Pallidus and area 4

Parafasicular Nucleus

receives fibers from Area 6

Midline Nuclei

− Consist of group of nerve cells to the 3rd ventricle and in the Interthalamic connection.

− Receive afferent fibers from the Reticular Formation

Reticular Nucleus

s a thin layer of nerve cells sandwiched between the external medullary lamina and posterior

limb of the internal capsule.

Medial Geniculate Body

Forms part of Auditory pathway

Medial Geniculate Body

Swelling on posterior surface of the thalamus beneath the pulvinar

Medial Geniculate Body

Receives auditory information from both ears (predominantly opposite ear)

Lateral Geniculate Body

Forms part of visual pathway

Lateral Geniculate Body

Swelling on undersurface of the pulvinar of the thalamus

Lateral Geniculate Body

Visual information from opposite field of vision