Neocortex: Vertical Columns

 Vertical Columns

The basic functional units of the neocortex are vertical cell columns that reach through all layers and have a diameter of 200 – 300 µm. Electrophysiological studies have shown that, in the cortical projection areas, each cell column is connected to a defined peripheral group of sensory cells. Stimula-tion of the peripheral field always yields a response from the entire column.

Fiber tracts connect the cortical columns with each other (D): the fibers of a column (D20) run either to columns of the ipsi-lateral hemisphere  or via the corpus callosum to mostly symmetrically localized columns of the contralateral hemisphere . Branches of individual fibers terminate in different columns (D21). It is estimated that the neocortex is made up of 4 million columns.

Comments

Post a Comment

Popular posts from this blog

Orbital cavity (eye socket) - Structure of the Eye

Image
  Orbit The orbital cavity (eye socket) is lined by the periosteum ( periorbita ) ( C26 ) and is filled with fatty tissue, the  orbital fat body  ( C27 ), in which the eyeball ( C28 ), the optic nerve ( C29 ), and the eye muscles ( C30 ) are embedded. At the anterior margin of the orbit, the fatty tissue is demarcated by the orbital septum ( BC31 ). The fatty tissue is separated from the eyeball by a connective tissue capsule, the  bulbar sheath  ( C32 ), which encloses the  sclera  ( C33 ). C34 Choroidea. C35 Osseous wall of the orbit.
Read more

Ciliary Body - Structure of the Eye

Image
  Ciliary Body The lens is suspended at the circular  ciliarybody  ( A19 ,  D ). The muscles of the ciliarybody control the curvature of the lens  and, hence, the visual acuity for close and distant vision. It consists of a radially folded surface, the  ciliary disk  ( D20 ), from where approximately 80  ciliaryprocesses  ( D21 ) protrude ( ciliary crown ). Theanterior part of the disk is occupied by the ciliary muscle; its muscle fibers, the  merid-ional fibers  ( A22 ), span between the oraser-rata and the reticulum trabeculare as well as Descemet’s membrane. From here, radial muscle fibers extend inward and bend to take a circular course ( circular fibers ) ( A23 ). The posterior surface of the ciliary body is covered by the  ciliary part of the retina ( A24 ). Delicate fibers, the  zonular fibers  ( AD25 ), extend from the ciliary body to the lens and form the  ciliary zone  ( D26 ). Many fibers ori...
Read more

Red Nucleus and Substantia Nigra

Image
  Red Nucleus and Substantia Nigra Lateral View of the Brain Stem (A) The two large nuclei extend far toward the diencephalon. The  substantia nigra  ( AB1 ) reaches from the oral part of the  pons  ( A2 ) to the  pallidum ( AB3 ) in the diencephalon. Both nuclei are important relay stations of the extrapyramidal system. Red Nucleus (A, B) The nucleus ( AB4 ) appears reddish in a fresh brain section (high iron content, p. 148, A). It consists of the parvocellular  neorubrum  and the magnocellular  paleoru-brum  situated ventrocaudally. Afferent connections The  dentatorubral fasciculus  ( B5 ) of the  dentate nucleus  ( B6 ) of the cerebellumruns in the  superior cerebellar peduncle  and terminates in the       contralateral red nucleus.   !     The  tectorubral tract  ( B7 ) of the superior colliculus terminates in the ipsilateral and contralateral...
Read more