Inferior longitudinal fasciculus

The inferior longitudinal fasciculus is a long-range association fibre pathway that primarily connects the occipital and temporo-occipital regions with the anterior temporal lobe within the same cerebral hemisphere. It is a bidirectional, multilayered fibre system, rather than a single homogeneous bundle, and forms an important component of the ventral visual processing pathway.

Relationship with various long association fibres

The inferior longitudinal fasciculus passes longitudinally through the occipital and temporal white matter, where it lies superficial and ventral to the inferior fronto-occipital fasciculus and has close relationships with several other white-matter pathways, including the uncinate and arcuate fasciculi, vertical occipital fasciculus, optic radiations and tapetal fibres.

Functionally, the inferior longitudinal fasciculus primarily conveys and integrates visual information between occipital visual areas and temporal cortical regions, contributing to object and face recognition, reading, lexical and semantic processing, recognition of visual emotional information, and visual memory. Some functions show relative hemispheric specialisation, particularly face processing in the right inferior longitudinal fasciculus and reading and lexical processing in the left inferior longitudinal fasciculus, whereas object recognition appears to depend more bilaterally on the pathway.

Damage to the inferior longitudinal fasciculus may therefore contribute to higher-order visual and cognitive disturbances, including visual agnosia, prosopagnosia and alexia, although these functions involve broader neural networks and should not be attributed exclusively to the inferior longitudinal fasciculus.