Visual pathway

What is the correct order of elements of the visual pathway?

Retina > Optic nerve > Optic chiasm > Optic tracts > Lateral geniculate nucleus > Meyer’s loop > Optic radiations > Visual cortex

Which retinal area is represented by the majority of the fibres of the optic nerve?

Macula

Which fibres decussate in the optic chiasm?

Nasal fibres

What type of visual field loss is common in a chiasmal lesion?

Bitemporal hemianopia

What type of visual field loss results from a lesion to the optic nerve?

Unilateral total field loss

Where do the optic tracts synapse?

Lateral geniculate nucleus

True or false? - The optic tracts are organised by nasal and temporal retina.

False - the retinal fibres have decussated at the chiasm, meaning that each optic tract contains both nasal and temporal retinal fibres. Instead, the tracts are organised by superior and inferior retina.

True or false? - the optic tracts only project to the LGN.

False - some of the fibres also project to the superior colliculi across the posterior commissure as part of the pupillary light reflex.

How many layers make up the lateral geniculate nucleus?

6

What is Meyer’s loop?

Portion of the optic radiations travelling around the lateral ventricle and through the temporal lobe

Where do the optic radiations synapse?

Brodmann area 17

What is the typical pattern of visual field loss in a lesion to Meyer’s loop?

Homonymous superior quadrantanopia

What anatomical feature of the brain corresponds to Brodmann area 17?

Calcarine sulcus

How many layers make up Brodmann area 17?

6

What are the Stria of Gennari and where are they located?

The Stria of Gennari are highly myelinated sections of the optic radiations, which synapse in layer IV of the primary visual area (Brodmann 17)

What are ocular dominance columns?

Strictly organised columns and rows of optic radiation axons, with right and left eye rows, and orientation-specific columns

True or false? - Brodmann area 17 is the only visual area in the brain.

False - the occipital lobe also houses Brodmann areas 18 and 19, which are involved in visual processing

Is the ventral visual stream the ‘what’ or the ‘where’ pathway, and where does it project to?

The ventral stream represents the ‘what’ pathway, and projects to the temporal lobe.

Is the dorsal visual stream the ‘what’ or the ‘where’ pathway, and where does it project to?

The dorsal stream represents the 'where' pathway, and projects to the parietal lobe.