The substantia innominata (literally "unnamed substance") of Meynert is a stratum in the human brain consisting partly of gray

Grey matter

Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil , glial cells and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts...

 and partly of white

White matter

White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...

 substance, which lies below the anterior part of the thalamus

Thalamus

The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

 and lentiform nucleus

Lentiform nucleus

The lentiform nucleus or lenticular nucleus comprises the putamen and the globus pallidus within the basal ganglia. It is a large, cone-shaped mass of gray matter just lateral to the internal capsule.-Etymology:...

. The gross anatomical structure is called the anterior perforated substance

Anterior perforated substance

The anterior perforated substance is an irregularly quadrilateral area in front of the optic tract and behind the olfactory trigone, from which it is separated by the fissure prima; medially and in front, it is continuous with the subcallosal gyrus; it is bounded laterally by the lateral stria of...

 because, to the naked eye, it appears to be perforated by many holes (which are actually blood vessels). It is part of the basal forebrain

Basal forebrain

The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...

 and includes the nucleus basalis.

Layers

It consists of three layers, superior, middle, and inferior.

• The superior layer is named the ansa lentiformis, and its fibers, derived from the medullary lamina of the lentiform nucleus, pass medially to end in the thalamus and subthalamic region, while others are said to end in the tegmentum
  Tegmentum
  The tegmentum is a general area within the brainstem. It is located between the ventricular system and distinctive basal or ventral structures at each level...
  
   and red nucleus
  Red nucleus
  The red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
  
  .

• The middle layer consists of nerve cells and nerve fibers; fibers enter it from the parietal lobe through the external capsule
  External capsule
  The external capsule is a series of white matter fiber tracts in the brain. These fibers run between the most lateral segment of the lentiform nucleus and the claustrum....
  
  , while others are said to connect it with the medial longitudinal fasciculus
  Medial longitudinal fasciculus
  The medial longitudinal fasciculus is a pair of crossed fiber tracts , one on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem and are composed of both ascending and descending fibers that arise from a number of sources and terminate in different...
  
  .

• The inferior layer forms the main part of the inferior stalk of the thalamus, and connects this body with the temporal lobe
  Temporal lobe
  The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
  
   and the insula
  Insular cortex
  In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
  
  .

External links

• Diagram at biocfarm.unibo.it