physics

Optic tract

Optic tract is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Optic tract rather than just read about it. In short: In neuroanatomy, the optic tract (from Latin tractus opticus) is a part of the visual system in the brain. It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus.

Key takeaways

Optic tract belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Optic tract to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Optic tract from memory before moving on to harder problems.

Reference excerpt

In neuroanatomy, the optic tract (from Latin tractus opticus) is a part of the visual system in the brain. It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus. It is composed of two individual tracts, the left optic tract and the right optic tract, each of which conveys visual information exclusive to its respective contralateral half of the visual field. Each of these tracts is derived from a combination of temporal and nasal retinal fibers from each eye that corresponds to one half of the visual field. In more specific terms, the optic tract contains fibers from the ipsilateral temporal hemiretina and contralateral nasal hemiretina.

Anatomy

Arterial supply The optic tract receives arterial supply from the anterior choroidal artery, and posterior communicating artery.

Function

Visual function The optic tract carries retinal information relating to the whole visual field. Specifically, the left optic tract corresponds to the right visual field, while the right optic tract corresponds to the left visual field. To form the right visual field, temporal retinal fibers from the left eye and nasal retinal fibers from the right eye form the left optic tract, and to form the left visual field, temporal retinal fibers from the right eye and nasal retinal fibers from the left eye form the right optic tract.

Autonomic function Several autonomic ocular motor responses are consensual. The optic tract is primarily responsible for relaying visual information to the LGN, but it is also peripherally responsible for transducing these bilateral autonomic reflexes, including the pupillary light reflex and pupillary dark reflex.

Pupillary light reflex The pupillary light reflex is an autonomic reflex that controls pupil diameter to accommodate for increases in illumination as perceived by the retina. Higher light intensity causes pupil constriction, and the increase of light stimulation of one eye will cause pupillary constriction of both eyes. The neural circuitry of the pupillary light reflex includes the optic tract which joins the optic nerve to the brachium of the superior colliculus.

Pupillary dark reflex Similarly to the pupillary light reflex, the pupillary dark reflex is an autonomic reflex that controls pupil diameter to accommodate for decreases in illumination as perceived by the retina. Lower light intensity causes pupil dilation, and the decrease of light stimulation of one eye will cause pupillary dilation of both eyes. Similarly, the neural circuitry of the pupillary dark reflex includes the optic tract which joins the optic nerve to the hypothalamus.

Damage and pathologies

Lesions Lesions in the optic tract correspond to visual field loss on the left or right half of the vertical midline, also known as homonymous hemianopsia. A lesion in the left optic tract will cause right-sided homonymous hemianopsia, while a lesion in the right optic tract will cause left-sided homonymous hemianopsia. Stroke, congenital defects, tumors, infection, and surgery are all possible causes of optic tract damage. Peripheral prism expanders and vision restitution therapy may be employed in patients with visual field loss resultant of permanent optic tract damage.

Split-brain In certain split-brain patients who have undergone a corpus callosotomy to treat severe epilepsy, the information from one optic tract does not get transmitted to both hemispheres. For instance, a split-brain patient shown an image in the left visual field will be unable to vocally name what has been seen as the speech-control center is in the left hemisphere of the brain.

Pupillary reflexes Pupillary reflexes, particularly the pupillary light reflex, are a powerful diagnostic tool often employed in clinical and emergency medical practice. A lack of equal consensual pupillary constriction to a light stimulus, especially a Marcus Gunn pupil, can be indicative of optic nerve damage, brainstem death, or optic tract damage in between.

Additional images

See also Optic nerve (CN II) Ophthalmic nerve (CN V1) Bistratified cell Optic radiation

References

Illustrations

Worked examples

Example 1 — a first encounter with Optic tract

Start with the simplest possible case. Write down what Optic tract claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Optic tract before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Optic tract ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Optic tract

In research: Optic tract appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Optic tract in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Optic tract is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cerebrum, Visual system, so understanding it makes those chapters shorter.
In everyday life: Look for Optic tract outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Optic tract in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Optic tract means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Optic tract out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Optic tract in simple terms?

Why does Optic tract matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Optic tract?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Optic tract.