Superior longitudinal fasciculus


The superior longitudinal fasciculus is an association fiber tract in the brain that is composed of three separate components. It is present in both hemispheres and can be found lateral to the centrum semiovale and connects the frontal, occipital, parietal, and temporal lobes. These bundles of axon tracts pass from the frontal lobe through the operculum to the posterior end of the lateral sulcus where they either radiate to and synapse on neurons in the occipital lobe or turn downward and forward around the putamen and then radiate to and synapse on neurons in anterior portions of the temporal lobe.
The SLF is composed of three distinct components SLF I, SLF II, and SLF III.

SLF I

SLF I is the dorsal component and originates in the superior and medial parietal cortex, passes around the cingulate sulcus and in the superior parietal and frontal white matter, and terminates in the dorsal and medial cortex of the frontal lobe and in the supplementary motor cortex.
SLF I connects to the superior parietal cortex which encodes locations of body parts in a body-centric coordinate system and with M II and dorsal premotor cortex. This suggests the SLF I is involved with regulating motor behavior, especially conditional associative tasks which select among competing motor tasks based on conditional rules.

SLF II

SLF II is the major component of SLF and originates in the caudal-inferior parietal cortex and terminates in the dorsolateral prefrontal cortex.
SLF II connects to the caudal inferior parietal cortex which controls spatial attention and visual and oculomotor functions. This suggests the SLF II provides the prefrontal cortex with parietal cortex information regarding perception of visual space. Since these bundles are bi-directional, working memory in the prefrontal cortex may provide the parietal cortex with information to focus spatial attention and regulate selection and retrieval of spatial information.

SLF III

SLF III is the ventral component and originates in the supramarginal gyrus and terminates in the ventral premotor and prefrontal cortex.
SLF III connects the rostral inferior parietal cortex which receives information from the ventral precentral gyrus. This suggests that the SLF III transfers somatosensory information, such as language articulation, between the ventral premotor cortex, Brodmann 44, the supramarginal gyrus, and the laterial inferior prefrontal cortex working memory.