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Longitudinal fissure

From Wikipedia, the free encyclopedia

Longitudinal fissure
The human brain as viewed from above. Median longitudinal fissure visible in red, running top to bottom.
Longitudinal fissure shown in red (animation)
Details
Identifiers
Latinfissura longitudinalis cerebri, fissura cerebri longitudinalis
NeuroNames35
NeuroLex IDbirnlex_4041
TA98A14.1.09.007
TA25417
FMA83727
Anatomical terms of neuroanatomy

The longitudinal fissure (or cerebral fissure, great longitudinal fissure, median longitudinal fissure, interhemispheric fissure) is the deep groove that separates the two cerebral hemispheres of the vertebrate brain. Lying within it is a continuation of the dura mater (one of the meninges) called the falx cerebri.[1] The inner surfaces of the two hemispheres are convoluted by gyri and sulci just as is the outer surface of the brain.

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Transcription

The human brain is divided into three major parts : - The cerebrum – the largest part of the human brain. The cerebrum enables sensory perception and controls voluntary motor actions. - The cerebellum – the cerebellum lies inferior to the cerebrum at the back of the head. It is mostly involved in coordination of movement and fine tuning of motor activities. - The brainstem - the brainstem is located at the base of the brain and is continuous to the spinal cord. It houses all nerve connections between different parts of the central nervous system. The brainstem provides innervation to the head and neck via cranial nerves. It also contains nuclei associated with important body functions such as regulation of blood pressure, respiration, swallowing, bladder control, sleep cycle, … among others. On top of the brainstem, and sometimes classified as part of it, is the diencephalon. The main components of the diencephalon are: - The thalamus – the thalamus serves as a gateway relaying sensory signals originated throughout the body to the cerebral cortex. It is also involved in emotional and memory functions. - The hypothalamus – the hypothalamus is the major control center of the autonomic nervous system and plays essential role in homeostatic regulation. The hypothalamus links the nervous system to the endocrine system via the pituitary gland. It also contains nuclei involved in regulation of body temperature, food and water intake, sleep and wake cycle, memory and emotional behavior. The cerebrum consists of two cerebral hemispheres. The left hemisphere controls the right half of the body. The right hemisphere controls the left half of the body. The two hemispheres are separated by a deep groove called the longitudinal fissure. Each hemisphere has a number of folds called gyri separated by grooves called sulci. A major landmark is the central sulcus. The cerebrum has four major lobes. The frontal lobe is situated anterior to the central sulcus. It is associated mainly with voluntary motor functions, planning, motivation, emotion and social judgment. Posterior to the central sulcus is the parietal lobe. This lobe is mainly concerned with sensory functions of the somatosensory category such as touch, stretch, movement, temperature and pain. The temporal lobe is separated from the frontal and parietal lobes by the lateral sulcus. The temporal lobe is associated with hearing, learning, visual memory and language. The occipital lobe is located at the rear of the cerebrum. This is the visual processing center of the brain. At first glance, the two hemispheres look identical, but research has found a number of differences between them. This is called lateralization of brain function. For example, the language formation areas - the Wernicke’s and Broca’s areas - are usually located in the left hemisphere of right-handed people. Lesions to these areas result in language comprehension deficits or speech disorders. The corresponding areas in the right hemisphere are responsible for emotional aspect of language. Lesions to these areas do not affect speech comprehension and formation, but result in emotionless speech and inability to understand the emotion behind the speech such as sarcasm or a joke.

Structure

Falx cerebri

All three meninges of the cortex (dura mater, arachnoid mater, pia mater) fold and descend deep down into the longitudinal fissure, physically separating the two hemispheres. Falx cerebri is the name given to the dura mater in-between the two hemispheres, whose significance arises from the fact that it is the outermost layer of the meninges. These layers prevent any direct connectivity between the bilateral lobes of the cortex, thus requiring any tracts to pass through the corpus callosum. The vasculature of falx cerebri supplies blood to the innermost surfaces of the cortex, neighboring the midsagittal plane.[2]

Cerebral asymmetry

Though this fissure divides the brain, the two hemispheres of the human cortex are not perfectly symmetrical, both in structure and in function. For example, the planum temporale, roughly corresponding to the Wernicke’s area, was found to be 10 times larger in the left than the right hemisphere.[3] In contrast, the caudate nucleus, within the basal ganglia, was found to be larger in the right hemisphere.[4]

Corpus callosum

The corpus callosum connects the two halves of the brain below the fissure and conveys visual, auditory, and somatosensory messages between each half. The corpus callosum is responsible for eye movement and visual perception, maintaining a balance between arousal and attention, and the ability to identify locations of sensory stimulation. In a clinical setting, those with epilepsy may benefit from the division of the corpus callosum.[5][6]

Development

Phylogenetically

It is thought that a majority of existing animals, including Homo sapiens, have evolved from a common wormlike ancestor that lived around 600 million years ago, called the urbilaterian. A bilaterian animal is one that has symmetrical left and right body halves. While it is still debated whether this species had a complex brain or not, development of similar species support the hypothesis that it had at least a simple anterior collection of nerve cells, called a cephalon.[7] Furthermore, studies have shown that this cephalon was bilateral, consisting of two or more connected sub-collections that are separated by the mid-sagittal plane,[8] suggesting the first example of such a division.

Ontogenetically

A neural crest appears in the mammalian embryo as soon as the 20th day of development.[9] It is during embryonic development that a neural tube appears and is folded into a hollow structure, as shown in Figure 1. This process is also known as neurulation.[10] The neural tube is where the central nervous system forms, which later on in development will be subdivided and differentiated into distinct sections of the brain and spinal cord. These subdivisions occur by signaling molecules that direct differentiated cells to their correct location of the organism.[11] The bilateral sides of this structure then give rise to the two hemispheres of the Homo sapiens cortex but do not merge at any point besides the corpus callosum. As a result, the longitudinal fissure is formed.[12] The longitudinal fissure can appear as early as the eighth week of development, and distinctly separates the two hemispheres by around the tenth gestational week.[13]

Figure 1: Early embryonic neural tube, depicting the separation of two sides

Function

Essentially, the fissure's purpose is to separate the brain into two hemispheres, left and right. Through case studies of brain damage or stroke to either side of each hemisphere, there is evidence that the left side of the brain controls the right side of the body, and the right side controlling the left side of the body.[14] Stroke patients have been found to unilateral impairment following damage to either the left or right hemisphere, this effecting the opposite side of the body.[15] Separating each hemisphere allows for specialization of storage, procedural and cognitive function. Through "split-brain experiments", the left hemisphere is shown to specialize in mathematics, language and general logistics.[16] The right hemisphere is further specialized, generally, in music, art, facial recognition and in most spatial events.[17]

The longitudinal fissure also pays a role in the optic nerve tract. This is shown in (figure 4.) with the optic chiasm, which takes the nerve from the right eye to the left hemisphere and the left eye to the right hemisphere. The longitudinal fissure allows for this misdirection and crossover of nerves.[18] The crossover seems to be counterintuitive, however it does serve an adaptive purpose. This purpose is to give us stereopsis, (depth and three-dimensional vision), as well as a development of binocular vision.[19] These two components combined give the ability to have a larger perceived visual field, which coincides with the hypothesis that this is an adaptive function given by the fissures placement and structure. Damage to the nerve past the optic chiasm, will cause loss or impairment to the corresponding eye. If the right side of the brain is damaged and the nerve is damaged or destroyed, then the left eye will also follow the severity of damage.[20]

Clinical significance

The longitudinal fissure plays a key role in corpus callosotomy, neurosurgery resulting in split brain, as it provides unobstructed access to the corpus callosum. Corpus callosotomy is one of the procedures used for pharmacologically treating intractable epilepsy cases, and it consists of the division of the nerve fibers running between the two hemispheres through the corpus callosum. A neurosurgeon separates the two hemispheres physically by pulling them apart with special tools, and cuts through either approximately two thirds of the fibers in the case of partial callosotomy, or the entirety in the case of complete callosotomy.[21] Without the presence of longitudinal fissure, the corpus callosotomy procedure would be significantly more challenging and dangerous, as it would require the surgeon to navigate through densely connected cortical areas. Following the procedure, the two hemispheres are no longer able to communicate with each other as before.

While patients’ brains usually adapt and allow for uninterrupted daily life, cognitive tests can easily determine whether a patient has split-brain. In an experiment involving a chimeric figure, with a woman’s face on the left half and a man’s face on the right half, a patient with split-brain focusing on the middle point will point to the woman’s face when prompted to point to the face in the picture, and will answer “a man” if asked what the picture is depicting.[22] This is because the Fusiform Face Area (FFA) is in the right hemisphere, while language centers are predominantly in the left hemisphere.

Figure 2: Diffusion tensor imaging example

Repetitive transcranial magnetic stimulation

In studies, low-frequency repetitive transcranial magnetic stimulation (rTMS) applications have been tested with various cognitive processes during time perception tasks. Studies have analyzed the effects of the low-frequency rTMS on tests of time perception when the rTMS has been applied to the "parietal medial longitudinal fissure". Findings have shown evidence to support the hypothesis that participants in this study would underestimate their perception of time for short amounts of time and overestimate for longer periods of time. Specifically, the 20 participants underestimated 1 second time intervals and overestimated 4 second/9 second intervals after applying 1-Hz rTMS.[23]

Neurosurgery

The longitudinal fissure can serve as an effective surgical passage in the frontal bone during central and pterional craniotomies, which is opening into the skull by surgery.[24][25] While there are variations in the head shapes of many species, dogs have been found to have a high variation in terms of head shapes making it difficult to find a brain surgical procedure that will work effectively for them. One goal of the study was to distinguish the longitudinal cerebral fissure anatomy and their possible variations in brachy‐(B), dolicho‐(D) and mesaticephalic‐(M) dogs. Even though the lateral cerebral fissure morphology was uniform in the dog breeds. Mesaticephalic‐(M) dogs were found to have the greatest surgical passage resulting in access to more brain structures, while the dolicho‐(D) dogs had the smallest surgical passage.

Research

Figure 3: Area of the corpus callosum in comparison with the longitudinal fissure surface area

As the corpus callosum is substantially smaller in surface area relative to the longitudinal fissure (Figure 3), fiber bundles passing through are densely packed together, and precision tracking is essential to distinguish between the individual bundles that originate from and lead to the same cortical centers. Understanding such connections allows us to understand the contralateral concurrences and what diseases can result from lesions to them. Diffusion tensor imaging (DTI or dMRI) along with fiber-tracking (FT) algorithms and functional Magnetic Resonance Imaging (fMRI) is used to image these bundles.[26][27] For instance, occipital-callosal fiber tracts were localized with 1–2  mm precision using DTI-TF techniques - which are very important for the cooperation of visual cortices, and any lesion to them can lead to alexia, the inability to read.

Additional images

Figure 4: Optical nerve cross over
  • facies dorsalis cerebri gyri
    facies dorsalis cerebri gyri
  • Cerebrum. Medial face. Dissection of corpus callosum etc.
    Cerebrum. Medial face. Dissection of corpus callosum etc.
  • Basal view of a human brain
    Basal view of a human brain
  • Cerebrum. Optic and olfactory nerves. Inferior view. Deep dissection.
    Cerebrum. Optic and olfactory nerves. Inferior view. Deep dissection.
  • Cerebrum. Inferior view. Deep dissection.
    Cerebrum. Inferior view. Deep dissection.
  • Meninges and superficial cerebral veins. Deep dissection. Superior view.
    Meninges and superficial cerebral veins. Deep dissection. Superior view.
  • Sheep Brain Dissection with labels
    Sheep Brain Dissection with labels
  • An anatomical illustration from the 1908 edition of Sobotta's Anatomy Atlas
    An anatomical illustration from the 1908 edition of Sobotta's Anatomy Atlas

See also

References

  1. ^ "longitudinal fissure - Ontology Browser - Rat Genome Database". rgd.mcw.edu. Retrieved 2019-09-24.
  2. ^ Bair, Michael M.; Munakomi, Sunil (2019), "Neuroanatomy, Falx Cerebri", StatPearls, StatPearls Publishing, PMID 31424888, retrieved 2019-09-24
  3. ^ Jill B. Becker (2002). Behavioral Endocrinology 2e. MIT Press. pp. 103–. ISBN 978-0-262-52321-9. Retrieved 4 January 2013.
  4. ^ Watkins, K. (2001). Structural Asymmetries in the Human Brain: A Voxel-based Statistical Analysis of 142 MRI Scans. Cerebral Cortex, 11(9), 868-877. doi:10.1093/cercor/11.9.868
  5. ^ Goldstein, Andrea; Covington, Benjamin P.; Mahabadi, Navid; Mesfin, Fassil B. (2019), "Neuroanatomy, Corpus Callosum", StatPearls, StatPearls Publishing, PMID 28846239, retrieved 2019-11-02
  6. ^ Buklina, S. B. (2005-06-01). "The corpus callosum, interhemisphere interactions, and the function of the right hemisphere of the brain". Neuroscience and Behavioral Physiology. 35 (5): 473–480. doi:10.1007/s11055-005-0082-5. ISSN 1573-899X. PMID 16033195. S2CID 14145192.
  7. ^ Hejnol, A., & Martindale, M. Q. (2008). Acoel development supports a simple planula-like urbilaterian. Philosophical Transactions of the Royal Society B: Biological Sciences,363(1496), 1493-1501. doi:10.1098/rstb.2007.2239
  8. ^ Mayer, G., Whitington, P. M., Sunnucks, P., & Pflüger, H. (2010). A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods. BMC Evolutionary Biology, 10, 255. doi:10.1186/1471-2148-10-255
  9. ^ O'Rahilly, R.; Müller, F. (September 2007). "The development of the neural crest in the human". Journal of Anatomy. 211 (3): 335–51. doi:10.1111/j.1469-7580.2007.00773.x. PMC 2375817. PMID 17848161.
  10. ^ Dady, A.; Havis, E.; Escriou, V.; Catala, M.; Duband, J. L. (2014). "Junctional Neurulation: A Unique Developmental Program Shaping a Discrete Region of the Spinal Cord Highly Susceptible to Neural Tube Defectsdoi= 10.1523/JNEUROSCI.1850-14.2014". The Journal of Neuroscience. 34 (39): 13208–13221. doi:10.1523/JNEUROSCI.1850-14.2014. PMC 6608335. PMID 25253865.
  11. ^ Patthey, Cédric; Gunhaga, Lena (2014-02-01). "Signaling pathways regulating ectodermal cell fate choices". Experimental Cell Research. Developmental Biology. 321 (1): 11–16. doi:10.1016/j.yexcr.2013.08.002. ISSN 0014-4827. PMID 23939346.
  12. ^ Purves, D., Augustine, G. J., Fitzpatrick, D., Hall, W. C., LaMantia, A., White, L. E., . . . Platt, M. L. (2018). Neuroscience. New York; Oxford: Sinauer Associates.
  13. ^ Dooling, E.C.; Chi, J.G.; Gilles, F.H. (1983), "Telencephalic Development: Changing Gyral Patterns", The Developing Human Brain, Elsevier, pp. 94–104, doi:10.1016/b978-0-7236-7017-9.50015-6, ISBN 9780723670179
  14. ^ Marieb, Hoehn. Brain Anatomy. http://www.wou.edu/~lemastm/Teaching/BI335/Laboratory%2001%20-%20Brain%20Anatomy.pdf
  15. ^ Gillen, Robert; Tennen, Howard; McKee, Tara (2005-04-01). "Unilateral spatial neglect: Relation to rehabilitation outcomes in patients with right hemisphere stroke". Archives of Physical Medicine and Rehabilitation. 86 (4): 763–767. doi:10.1016/j.apmr.2004.10.029. ISSN 0003-9993. PMID 15827929.
  16. ^ "Neuroscience For Kids - Hemispheres". faculty.washington.edu. Retrieved 2019-10-21.
  17. ^ "Neuroscience For Kids - Hemispheres". faculty.washington.edu. Retrieved 2019-10-21.
  18. ^ Ireland, Ashley C.; Carter, Iverson B. (2019), "Neuroanatomy, Optic Chiasm", StatPearls, StatPearls Publishing, PMID 31194427, retrieved 2019-11-02
  19. ^ Ireland, Ashley C.; Carter, Iverson B. (2019), "Neuroanatomy, Optic Chiasm", StatPearls, StatPearls Publishing, PMID 31194427, retrieved 2019-11-02
  20. ^ Ireland, Ashley C.; Carter, Iverson B. (2019), "Neuroanatomy, Optic Chiasm", StatPearls, StatPearls Publishing, PMID 31194427, retrieved 2019-11-02
  21. ^ "Corpus Callosotomy - Treatments - For Patients - UR Neurosurgery - University of Rochester Medical Center". www.urmc.rochester.edu. Retrieved 2019-09-20.
  22. ^ Levy, J., Trevarthen, C., & Sperry, R. W. (1972). Perception Of Bilateral Chimeric Figures Following Hemispheric Deconnexion. Brain, 95(1), 61-78. doi:10.1093/brain/95.1.61
  23. ^ Manaia, Fernanda; Rocha, Kaline; Marinho, Victor; Magalhães, Francisco; Oliveira, Thomaz; Carvalho, Valécia; Araújo, Thalys; Ayres, Carla; Gupta, Daya; Velasques, Bruna; Ribeiro, Pedro (June 2019). "The role of low-frequency rTMS in the superior parietal cortex during time estimation". Neurological Sciences. 40 (6): 1183–1189. doi:10.1007/s10072-019-03820-8. ISSN 1590-3478. PMID 30850896. S2CID 71716091.
  24. ^ Johns Hopkins Medicine. (n.d). Craniotomy. Health. Retrieved from https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/craniotomy
  25. ^ Carreira, L., & Ferreira, A. (2015).Longitudinal cerebral fissure anatomy variations in brachy-, dolicho- and mesaticephalic dogs and their importance to brain surgery. The Anatomical Record : Advances in Integrative Anatomy and Evolutionary Biology., 298(9), 1612–1621. doi:10.1002/ar.23183
  26. ^ Dougherty, R. F., Ben-Shachar, M., Bammer, R., Brewer, A. A., & Wandell, B. A. (2005). Functional organization of human occipital-callosal fiber tracts. Proceedings of the National Academy of Sciences, 102(20), 7350-7355. doi:10.1073/pnas.0500003102
  27. ^ Rokem, A., Takemura, H., Bock, A. S., Scherf, K. S., Behrmann, M., Wandell, B. A., . . . Pestilli, F. (2017). The visual white matter: The application of diffusion MRI and fiber tractography to vision science. Journal of Vision, 17(2), 4. doi:10.1167/17.2.4

External links

Wikimedia Commons has media related to Longitudinal fissure.
This page was last edited on 6 April 2024, at 16:39
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