The inferior longitudinal fasciculus (ILF) is traditionally considered one of the major occipitotemporal

association tract Association fibers are axons that connect cerebral cortex, cortical areas within the same cerebral hemisphere. In human neuroanatomy, axons (nerve fibers) within the brain, can be categorized on the basis of their course and connections as ass ...

s. It is the white matter backbone of the ventral visual stream. It connects the ventral surface of the anterior

temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...

and the

extrastriate cortex The extrastriate cortex is the region of the occipital cortex of the mammalian brain located next to the primary visual cortex. Primary visual cortex (V1) is also named striate cortex because of its striped appearance in the microscope. The extra ...

of the

occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...

, running along the lateral and inferior wall of the

lateral ventricle The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively. Each lateral ventricle resemble ...

. The existence of this fasciculus and its anatomical description have been the subject of several mutually conflicting studies. Some authors denied its existence because of the unclear results obtained in non-human brains. Using

diffusion tensor imaging Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is the use of specific MRI sequences as well as software that generates images from the resulting data that uses the diffusion of water molecules to generate contrast in MR images. It ...

(DTI), several authors have confirmed the presence of this constant longitudinal pathway in humans. Some other studies of the ILFLatini, F., Mårtensson, J., Larsson, E.-M., Fredrikson, M., Åhs, F., Hjortberg, M., et al. (2017). Segmentation of the inferior longitudinal fasciculus in the human brain: A white matter dissection and diffusion tensor tractography study. Brain Research based on Klingler's dissection method (a type of white matter blunt dissection, providing reliable data on the anatomy of major fibre bundles and, in some cases, additional

tractography In neuroscience, tractography is a 3D modeling technique used to visually represent nerve tracts using data collected by diffusion MRI. It uses special techniques of magnetic resonance imaging (MRI) and computer-based diffusion MRI. The results a ...

Panesar SS, Yeh FC, Jacquesson T, Hula W, Fernandez-Miranda JC. A Quantitative Tractography Study Into the Connectivity, Segmentation and Laterality of the Human Inferior Longitudinal Fasciculus.Front Neuroanat. 2018 Jun 5;12:47. doi: 10.3389/fnana.2018.00047 not only confirmed the classical descriptions of the direct connection between occipital and temporal regions but also sought to detail the subcomponents of this association tract. Four branches were consistently identified: a fusiform branch connecting the

fusiform gyrus The fusiform gyrus, also known as the ''lateral occipitotemporal gyrus'','' ''is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and the inf ...

to the anterior temporal regions; a dorsolateral occipital branch connecting the superior, middle and inferior occipital gyri to the anterior temporal regions; a lingual branch connecting the

lingual gyrus The lingual gyrus, also known as the ''medial'' occipitotemporal gyrus, is a brain structure that is linked to processing vision, especially related to letters. It is thought to also play a role in analysis of logical conditions (i.e., logical ord ...

to the anterior part of the middle temporal gyrus; and a minor cuneal branch connecting the cuneus to the anterior mesial temporal gyri.

Functions of the ILF

Summarising studies from healthy individuals, intraoperative and lesional findings, this white matter bundle supports functions linked to the ventral visual stream such as

object recognition Object recognition – technology in the field of computer vision for finding and identifying objects in an image or video sequence. Humans recognize a multitude of objects in images with little effort, despite the fact that the image of the ...

and

face perception Facial perception is an individual's understanding and interpretation of the face. Here, perception implies the presence of consciousness and hence excludes automated facial recognition systems. Although facial recognition is found in other spec ...

, Likewise, disorders linked to this white matter tract are disorders with perturbed visual perception such as associative visual

agnosia Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually ...

prosopagnosia Prosopagnosia (from Greek ''prósōpon'', meaning "face", and ''agnōsía'', meaning "non-knowledge"), also called face blindness, ("illChoisser had even begun tpopularizea name for the condition: face blindness.") is a cognitive disorder of fac ...

, visual amnesia, visual hypo-emotionality; but also some forms of

autism spectrum disorder The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder, neurodevelopmental condition (or conditions) ...

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...

and alexia. ILF supports brain functions concerning the visual modality, including object, face and place processing, reading, lexical and semantic processing, emotion processing, and visual memory. Based on these recent findings ILF can be described as a multi-functional white matter pathway involved in visually guided behavior (See Herbet et al. for reviewHerbet G, Zemmoura I, Duffau H. Functional Anatomy of the Inferior Longitudinal Fasciculus: From Historical Reports to Current Hypotheses. Front Neuroanat. 2018 Sep 19;12:77. doi: 10.3389/fnana.2018.00077).

References

External links

* - "Dissection of the Left Hemisphere" {{Authority control Cerebral white matter