INSIDE THE HUMAN FOREBRAIN,

Part Two ¹ of a self-paced, audio-tutoral lesson in neuroanatomy²

Web Contact pietsch@indiana.edu

CONTROL PANEL

SOUND BAR {90-min tape}

Here are a few suggestions, Doc: Wait 'til the tape fully loads before you mash the play button (that little right-facing arrowhead toward your left). There's a gizmo on the Sound Control bar that moves left to right while your machine is loading the mp3 program. Take a quick look at the Check List, at stuff you'll eventually want to know about the forebrain (cerebrum and diencephalon) from this and previous lessons. (But don't get spastic. Your pal Cranky won't squeal if you don't know the stuff.) Gabby (aka, the Hoosier Frankenstein) -- that guy on the tape -- thinks you're Igor with a plate of pickled brains and stuff in front of you. For those who don't have (like most of the World), we've collected pictures and diagrams, below. An advanced peek at that stuff wouldn't exactly hurt. You can either scroll down or link: Diagram of the Thalamus Diagram of the Hypothalamus Underside of the Brain Inner surface Coronal Sections Diagram of the fornix, hippocampus and mamillary body

CHECK LIST (optional):

1. internal capsule (anterior limb, posterior limb, genu)
2. lateral ventricle
3. basal nuclei:
   a) canduate n.
   b) lenticular n. (globus pallidus, putamen)
   c) amygdala
4. uncus
5. thalamus:
   a) pulvinar
   b) lateral geniculate body (nucleus)
   c) medial geniculate body (nucleus)
   d) massa intermedia (thalamic adhesion)
6. optic chiasm
7. hypothalamus
8. lamina terminalis
9. anterior commissure
10. fornix
    {back to the Cranky's suggestions}
    
11. hippocampus
12. insular cortex (Isle of Reil)
13. corpus callosum (genu and splenium)
14. third ventricle
15. foramen of Monro (interventricular foramen)
16. pineal body (gland)
17. Which belong to the diencepahlon?
18. Which belong to the cerebrum?

THALAMUS: NUCLEAR TERRITORIES

{back to the Cranky's suggestions}

Gabby (that Hoosier Frankenstein guy on the tape) calls this the "rowboat diagram." It's supposed to simplify the thalamus. Whatever, you can think of the thalamus as a bunch of nuclei (collections of cell bodies in the CNS [central nervous system], remember). Many many nuclei! To keep from going nuts trying to memorize every one of them, we can divide the thalamus as shown in the diagram; i. e., into logical zones (that don't demand a lot of rote); those zones receive specific input and then relay the vibes to particular places in the cerebrum. Thalamic cells, collectively, are a clearing house for information slated to go upstairs to the cerebral cortex. Notice, though, what the Hoosier Frankenstein does. First he chops off the rear end of the thalamus (the pulvinar and the medial and lateral geniculate bodies -- MGB and LGB). Then he takes what's left (the rowboat) and cuts it into Medial (next to the 3rd ventricle), Lateral and Anterior parts. The Lateral groups, we can subdivide further, into anterior, intermediate and posterior subgroups. The source and destination of the signals to those nuclear groups are in a table down towards the end. If you don't believe me Doc, click here. After you've digested what's on the tape, you might want to look over that table more closely. But look Doc, if you want to go and memorize each and every thalamic nucleus (e.g., the arcuate nucleus in the posterior-lateral group, which relays somesthetic signals from the head to the postcentral gyrus), check out any neuroanatomy textbook, and be my guest!

HYPOTHALAMUS: NUCLEAR TERRITORIES
{back to the Cranky's suggestions}

Optic Nerve (N II) Optic Chiasm Optic Tract Infundibulum (of the hypothalamus). The elliptic hole (at the arrowhead) -- an artifact-- is where the stalk of the pituitary gland attached to the brain. The latter organ (also called the hypophysis) remained in the cadaver's sella turcica when the brain was extracted from the cranial case.

{tipped up}: Mamillary Bodies, m -- rear end of the hypothalamus

INNER SURFACE
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The red wire passes into a lateral ventricle, via a foramen of Monro. The wire lies in the slit-like third ventricle (here a shallow depression). Recall (from the embryonic brain) that the third ventricle is the cavity of the diencephalon. The foramina (pl) of Monro are the passageways into the third ventricle for cerebrospinal fluid (CSF), some of which is produced in the lateral ventricles; s.p., septum pellucidum -- the velum-like medial wall of a lateral ventricle (one on each hemisphere); the corpus callosum: g --genu, cc --body, --s, splenium lamina terminalis (cut edge) -- anterior boundary of the hypothalamus anterior commissure (cut surface) hypothalamic sulcus (faint groove) -- thalamus above, hypothalamus below fornix (body) -- output conduit of the hippocampus The next frame shows a close view (scroll there)!

The little r is the rostrum of the corpus callosum; CC is the corpus callosum's genu (or knee, as in genuflect) Remember the lamina terminalis in the diagram of the embryo's brain, Doc?

CORONAL SECTIONS (a, b, c, d: anterior-->posterior)

{back to the Cranky's suggestions}

Plane a

{for close view of map click here} C, cortex of the cingulate gyrus F(above and below) marks the longitudinal fissure; the latter fissue (or sulcus) follows the contour of the genu of the corpus callosum. In a coronal section through the frontal lobe, which this is, the longitudinal fissure, like the corpus callosum, appears in the lower as well as upper part of the section. s.p., the septum pellucidum (pl = septi pellucidi) of each hemisphere and, thus, the medial wall of each lateral ventricle (1 and 2 here). 'X' marks the cavum septi pellucidi -- the narrow space between the two septi. N, head of the caudate nucleus I C, internal capsule (anterior limb) In this and the subsequent sections, white matter (myelin) stains deep blue (dark); gray matter takes on a reddish-brown appearence.

Plane a:

Plane c

{for close view of map click here} LV, LV' -- the lateral ventricles (1 and 2 -- which is which, left v right, has not been specified by the neuroanatomy thought police) 3, third ventricle cp, choroid plexuses secreate (actively transport) cerebro-spinal fluid (CSF) from the circulating blood into the ventricles. The foramen of Monro on each side drains the CSF of a lateral ventricle into the narrow, unpaired third ventricle fornices: (fornix is the singular) the body arches up and into close apposition to the underside of the corpus callosum. The columns of the fornices (towards 6 o'clock in the section) burrow into the meat of the hypothalamus and angle back to plug into the mamillary bodies. The fornix is the output conduit for the hippocampus (thought to be a major player in short-term, working memory). note the anterior commissure, a bridge between the right and left lenticular nuclei. caudate nuc. is the head of the caudate nucleus. the posterior limb of the internal capsule is sandwiched between the thalamus and the lenticular nucleus.

Plane d

{for close view of map click here} Notice the optic tract between the uncus and the internal capsule; the latter is directly continuous with the cerebral peduncle (crus cerebri) on the suface. A black arrow (on your left) points to the opposite optic tact. T is the thalamus; 3 the third ventricle. m, mamillary body (nucleus), an important terminal of the fornix, seen in the section through plane c. The mamillary bodies represent the posterior-inferior portion of the hypothalamus. M-T is the mamillo-thalamic tract. LV, lateral ventricles. IR is a downward extension of the portion ot the third ventricle in the hypothalamus; the indicated space is known as the infundibular recess. (Infundibulum means funnel in Latin.) That pink mass below IR (with the tippy-end of a black arrow pointing at it) is a part of the floor of the hypothalamus known as the tuber cinererum.

DIAGRAM OF THE HIPPOCAMPUS, FORNIX AND MAMILLARY BODY
{back to the Cranky's suggestions}

[LV lateral ventricle with septum pellucidum stripped off; t, thalamus; h, hypothalamus] The fornix carries signals from the hipppocampus, an ancient piece of cerebrum that's tucked into the temporal lobe. Thought by some investigators to be a major player in short-term or conscious, working memory, the hippocampus appears early in the embryo and in vertebrate evolution. One of the major receiving stations of the fornix is the mammillary body (nucleus). Among other places, the cells of the mammillary body signal the thalamus and do so through that prominent mammillo-thalamic tract (M-T in Plane d) . Need to see and the Uncus, Doc? If you do, click the X -- but scroll to get back here! {Click to return to plane c.}

REPLICA MODEL OF A LEFT HEMISPHERE This specimen was produced from a cast of a cadaver whose head had been splt slightly to the right of the mid-sagittal line.

S C, splenium of the corpus callosum; g (on the right) is the genu of the corpus callosum p, pulvinar of the thalamus, T letters ht lie on the hypothalamus; the lower arrow points at the mouth of a foramen of Monro f is the fornix (body); the column of the fornix arcs down and forms the anterior boundry of the foramen of Monro sp, septum pellucidum the cingulate g. (gyrus) is a major contributor to the what Broca in the 19th century called the limbic lobe ("grand lobe limbique"); or "emotional brain" of some contemporary authors. Click to return to: plane a plane b plane c plane d

BRAIN DEVELOPMENT

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