Pixelated Brain: Module 11, Section 5

MODULE 11 - SECTION 5 - THE OPTIC TRACT

The

A LATERAL VIEW of the BRAINSTEM on a MODEL

Start at the optic nerve; ignore the fact that the chiasm is vague, so continue to trace the course of the tract. it passes over the surface of the hypothalamus (orange in this view, but pea green in the one above), and then over the cerebral peduncle to reach the lateral geniculate nucleus.

THE VISUAL PATHWAY on a LATERAL VIEW of the BRAIN

Since this slide series starts behind the chiasm, our firs slid will be #36 and we will sintinue caudally to Slide #26.

VISUAL PATHWAY on SLIDE 34

VISUAL PATHWAY on SLIDE 32

VISUAL PATHWAY on SLIDE 28

VISUAL PATHWAY on SLIDE 26

Some would say that the optic tract is now beginning to rotate; for the right tract, shown here, it is a 90 degree counter-clockwise rotation, such that the yellow fibers move from the "top" of the tract to the medial edge as they prepare to enter the most medial pary of the lateral geniculate nucleus.

THE BRAINSTM
an OBLIQUE LATERAL VIEW

Now, follow the tract on this model.

THE BRAINSTEM - a BASAL VIEW

This ventral view of the same model shows the optic chiasm and tract.

THE BRAINSTEM - a BASAL VIEW

And here, another basal view.

MODULE 11 - SECTION 5 - THE OPTIC TRACT The
	LANDMARKS on a LATERAL VIEW of the BRAINSTEM Given all the excitement at the level of the chiasm, this next stretch of the pathway seems rather dull, but also a bit misleading. It seems as though the optic tract is running through the brain, but in fact it runs over the surface of the brain, and has been covered over by the expanding hemisphere. If you cut away the temporal lobe, as was done here , it is clear that the optic tract is actually running over the surface of the cerebral peduncle to reach the lateral geniculate nucleus.
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	A LATERAL VIEW of the BRAINSTEM on a MODEL Start at the optic nerve; ignore the fact that the chiasm is vague, so continue to trace the course of the tract. it passes over the surface of the hypothalamus (orange in this view, but pea green in the one above), and then over the cerebral peduncle to reach the lateral geniculate nucleus.
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	THE VISUAL PATHWAY on a LATERAL VIEW of the BRAIN Since this slide series starts behind the chiasm, our firs slid will be #36 and we will sintinue caudally to Slide #26.
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	SLIDE LEVELS for the VISUAL PATHWAY shown on a LATERAL VIEW of the BRAINSTEM
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	VISUAL PATHWAY on SLIDE 36 X
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	VISUAL PATHWAY on SLIDE 34 X
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	VISUAL PATHWAY on SLIDE 32 X
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	VISUAL PATHWAY on SLIDE 30 X
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	VISUAL PATHWAY on SLIDE 28 X
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	VISUAL PATHWAY on SLIDE 26 Some would say that the optic tract is now beginning to rotate; for the right tract, shown here, it is a 90 degree counter-clockwise rotation, such that the yellow fibers move from the "top" of the tract to the medial edge as they prepare to enter the most medial pary of the lateral geniculate nucleus.
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	THE BRAINSTM an OBLIQUE LATERAL VIEW Now, follow the tract on this model.
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	THE BRAINSTEM - a BASAL VIEW This ventral view of the same model shows the optic chiasm and tract.
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	THE BRAINSTEM - a BASAL VIEW And here, another basal view.
The fact of the matter is that the retinotopic organization of the visual pathway within the optic tract is of little clinical significance and most texts don't even mention it. The reason is that the optic tract is such a compact bundle of fibers that it is rare for only a part of it to be damaged. Thus, unlike the situation in the region of the visual radiation, lesions of the optic tract usually give rise to rather simple loss (a contralateral homonymous hemianopsia. Never the less, we show the retinotopic organization of the tract just to give you a sense of continuity. 13
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