Superior longitudinal fasciculus

Superior longitudinal fasciculus

Lateral surface of left cerebral hemisphere. Some of major association tracts are depicted. Superior longitudinal fasciculus is at center, in red.

Diagram showing principal systems of association fibers in the cerebrum. (Sup. longitudinal fasc. labeled at center top.)
Details
Identifiers
Latin fasciculus longitudinalis superior cerebri
NeuroNames ancil-537
Dorlands
/Elsevier		 f_03/12356082
TA A14.1.09.557
FMA 77631

Anatomical terms of neuroanatomy

The superior longitudinal fasciculus (also called the superior longitudinal fascicle or SLF) is a pair of long bi-directional bundles of neurons connecting the front and the back of the cerebrum. Each association fiber bundle is lateral to the centrum ovale of a cerebral hemisphere and connects the frontal, occipital, parietal, and temporal lobes. The neurons pass from the frontal lobe through the operculum to the posterior end of the lateral sulcus where numerous neurons radiate into the occipital lobe and other neurons turn downward and forward around the putamen and radiate to anterior portions of the temporal lobe.

Anatomy

The SLF is composed of four distinct components[1] SLF I, SLF II, SLF III, and arcuate fascicle (AF). In humans, these four components are bundled together although they are functionally separate. In non-human primates, the SLF and AF are anatomically separate and have separate trajectories.

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 (Brodmann 6, 8, and 9) and in the supplementary motor cortex (M II).[2][3]

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 (Brodmann 6, 8 and 46).

SLF III

SLF III is the ventral component and originates in the supramarginal gyrus (rostral portion of the inferior parietal lobe) and terminates in the ventral premotor and prefrontal cortex (Brodmann 6, 44, and 46).

AF

The AF originates in the caudal area of the superior temporal gyrus and passes next to the neurons of SLF II above the Sylvian fissure and insula in non-human primates. In humans, neurons that originate from the caudal superior temporal gyrus and the superior temporal sulcus pass around the caudal Sylvian fissure and along with the SLF bundle and terminate in the dorsal prefrontal cortex (Brodmann areas 8 and 46).

Functions

SLF I

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.[4] 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 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 (Brodmann 46) 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 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 (pars opercularis), the supramarginal gyrus (Brodmann 40), and the laterial inferior prefrontal cortex working memory (Brodmann 46).

AF

The arcuate fascicle connects the superior temporal gyrus (Tpt) with the dorsal prefrontal cortex which suggests auditory information is transmitted between those two areas of cortex.[5]

References

  1. ↑ Makris pages 1-2
  2. ↑ Kamali, A; Flanders, AE; Brody, J; Hunter, JV; Hasan, KM (2014). "Tracing superior longitudinal fasciculus connectivity in the human brain using high resolution diffusion tensor tractography". Brain Struct Funct. 219: 269–81. doi:10.1007/s00429-012-0498-y. PMID 23288254.
  3. ↑ Makris page 11
  4. ↑ Makris page 13
  5. ↑ Makris page 14

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