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Rehabilitation and management of visual dysfunction following traumatic brain injury
Published in Mark J. Ashley, David A. Hovda, Traumatic Brain Injury, 2017
The physical substrates of vision are covered in depth in Chapter 9 of this volume, and only a brief overview is given here. Estimates by surface-based mapping in humans demonstrated that approximately one third of the human neocortex is devoted to processing vision.2 Researchers have described approximately 305 intracortical pathways linking 32 different cortical areas implicated in visual function in the primate; 25 of these are regarded as either predominantly or exclusively involved in visual function, and seven are considered visual-association areas.3 The one million ganglion cells traveling from each retina represent approximately 70% of all sensory input fibers to the brain. By contrast, the auditory nerve is comprised of approximately 35,000 nerve fibers. Four of the 12 cranial nerves subserve only vision (CN II, CN III, CN IV, and CN VI). Two additional cranial nerves supply sensation from the eyeball (CN V) and motor function to the eyelids (CN VII) along with other structures. Multiple subcortical visual substrates are involved in binocular coordination, visual attention, integrating multimodal stimuli, and perceptual coherence as well as nonvisual light processing involved in diurnal regulation. In addition to these multiple subcortical areas, every lobe of the cortex is involved in visual processing (Reviewed by Kravitz et al.4,5; Figures 26.1 and 26.2). The occipital lobe contains the primary visual cortex for initial processing of vision as contour, contrast, and depth. The inferior temporal lobe is involved in object identification, the middle temporal area in motion processing, and the parietal lobe in processing for spatial organization and visual attention.4,6 The ventral occipital temporal cortex has been implicated in word form recognition, and damage to the vertical occipital fasciculus running from this area to language and reading areas results in pure word blindness.7 The frontal eye fields and adjacent areas of the frontal and prefrontal lobes are involved in motor planning and initiation of self-directed eye movements as well as visual search.8 The ventrolateral prefrontal cortex is involved in visual working memory.9 In addition, simple visual awareness requires interactions between the primary visual cortex, posterior parietal cortex, and the frontal eye fields. Input from the limbic system (especially the cingulate gyrus) may mediate motivational relevance of the external stimulus, guiding sustenance of attentional activation in the visual system.10 Nonvisual afferent ganglion cells from the retina mediate circadian rhythms at the suprachiasmatic nucleus, which sends messages to the pineal gland for melatonin expression.11
Structural brain alterations in young adult males with narcissistic personality disorder: a diffusion tensor imaging study
Published in International Journal of Neuroscience, 2023
Jing Lou, Yueji Sun, Zhixia Cui, Lei Gong
In the study, we found a lower FA value in the ILF, which is a multilayered, bidirectional fasciculus that have a direct contact with the uncinate fasciculus, the optic radiations, the long and posterior/vertical segments of the arcuate fasciculus, the IFOF and the vertical occipital fasciculus of Wernicke [19] Moreover, ILF participates in the process of decision-making and behavior of visual guidance. Individuals with NPD have defects in cognition, emotion recognition, description or recognition ability of internal self-state [20]. The uncinate fasciculus and ILF cortex project to the anterior temporal. They indirectly provide the anatomical connection between the posterior temporal lobe and the posterior occipital region and the frontal lobe, form an indirect ventral flow, and participate in language processing and semantic processing [19]. The destruction of ILF may also constitute the pathophysiological basis of visual hallucination and social affective disorders in mental hallucinations and affective disorders in autism spectrum disorders. Once ILF injures, it may interrupt the transmission, deprive the emotional quality of the visual experience, and produce the visual hypoemotionality [21]. Our results are in accordance with the previous studies showing the lower FA in individuals with borderline personality disorder (BPD) [16].
Impact of Amblyopia on the Central Nervous System
Published in Journal of Binocular Vision and Ocular Motility, 2020
Nathaniel P. Miller, Breanna Aldred, Melanie A. Schmitt, Bas Rokers
Structural changes have been found in larger cortico-cortical projections, including increased mean diffusivity in the left inferior longitudinal fasciculus (ILF), a major pathway connecting occipital cortex (striate and extrastriate regions) to anterior temporal cortex.83,94 This study described similar structural changes in the right vertical occipital fasciculus (VOF), a little-known (and not thoroughly characterized) pathway connecting dorsal and ventral occipital cortex.95,96 Li et al. found structural changes (decreased FA) in the left ILF as well, in addition to the right superior longitudinal fasciculus (SLF),84 a large pathway that connects portions of the frontal, parietal, occipital, and temporal cortices.97,98