Disruptions in physical substrates of vision following traumatic brain injury
Mark J. Ashley, David A. Hovda in Traumatic Brain Injury, 2017
The organizational blueprint of the brain begins in the neocortex, whose laminar structure consists of six layers, a ribbon over the cerebral hemispheres. Variations in the layers of cells are found in different parts of the cortex with those areas having similar columns of cells serving a specific function. These are called modules. As described later in this chapter, an example of a module would be the primary visual cortex (PVC) in the occipital lobe because of the specific organization of column cells serving specific functions, such as form, color stereopsis, and motion. There are other primary sensory areas, including the auditory, somatosensory, gustatory, olfactory, and vestibular cortices. These primary sensory areas project their specific modality to the surrounding association cortex for more complex processing. In vision, this would be the primary visual cortex or striate cortex to extrastriatal visual areas (see Figure 9.2). This results in different sensory-specific modality association cortices. These different sensory-specific association cortices then communicate with each other via bidirectional, divergent, and convergent fibers to form the posterior multimodal association area.
Estrogens and dementia: a clinical and epidemiological update
Barry G. Wren in Progress in the Management of the Menopause, 2020
The key symptom of Alzheimer’s disease is a defect in long-term episodic memory — the ability to learn new information that can be recalled after a delay of several minutes or longer. Although semantic memory — memory for over-learned general information such as word names — is also affected, a disturbance in semantic memory is usually not the initial symptom, and semantic memory is less severely disrupted early in the disease course. Episodic memory loss in Alzheimer’s disease is linked to severe pathological changes within hippocampal and parahippocampal structures of the medial temporal lobes1 and to a deficiency in the neurotransmitter acetylcholine2. Semantic memory loss reflects more widely distributed pathology within the association cortex of the cerebral hemispheres.Other cognitive and behavioral alterations are common in this illness. Visuospatial impairments, for example, are implied when patients become lost in their own home or are unable to copy simple line drawings3. A depressed mood4 and other behavioral disturbances are observed in some patients.
The neural basis of semantic memory
Lars-Göran Nilsson, Nobuo Ohta in Dementia and Memory, 2013
Visual concepts are strongly associated with a visual appearance in memory (e.g., “apple”). Previous fMRI studies have linked the representation of visual concepts with activity in regions of the ventral temporal lobe, including areas of visual association cortex (Wang et al., 2010). We have examined the role of ventral temporal cortex in the representation of object concepts by investigating patients with the semantic variant of primary progressive aphasia (svPPA; also known as semantic dementia), a neurodegenerative disease affecting regions of the ventral and inferolateral portions of the temporal lobe and resulting in a profound loss of semantic knowledge (Gorno-Tempini et al., 2004; Bonner et al., 2010). In these patients, we have examined a finding known as the “reversal of the concreteness effect.”
Nineteenth- and twentieth-century brain maps relating to locations and constructions of brain functions
Published in Journal of the History of the Neurosciences, 2022
Figure 18 is a graphic of Flechsig’s findings. It superimposes myelination information on a line-drawing of the left lateral aspect of the brain. It takes full advantage of the knowledge gained about the convolutions by Turner and Ecker. Notice that the convolutions on either side of the fissure of Rolando is in the primordial zone—shown in black crosshatching in the figure. The auditory association cortex (area 10 and broadly encompassing Heschl’s gyrus and Wernicke’s area) is also in that zone. The numerical order of the numbers reflects the chronological order of myelination. However, the order of myelination of specific areas was not exploited by Geschwind in further analyses, but Flechsig’s three broad functional zones were. Mesulam showed the relevance of these zones for current analysis. The reader can refer to Figure 18 for reference. Areas with the earliest myelination, encompassing primary sensory-motor and limbic cortices, were designated [by Flechsig as] ‘primordial.’ [These areas are in black crosshatching.] The next phase of myelination occurred in intermediate’ (parasensory) areas that surrounded the primordial zones. [These are the areas marked by vertical lines on gray background.] The areas that were the latest to myelinate, located in prefrontal, posterior parietal and lateral temporal cortex, were designated ‘terminal’ [the white or unmarked areas] and were singled out as the components that most clearly distinguished human from anthropoid brains. (Mesulam 2015, 2793)
Functional brain segregation changes during demanding mathematical task
Published in International Journal of Neuroscience, 2019
Amir Hossein Ghaderi, Mohammad Ali Nazari, Amir Hossein Darooneh
Mathematical tasks engage many aspects of cognition such as memory, arousal, executive function and creativity. The neural basis of arithmetic problem solving i.e. numerical processing and complex calculation [3], mathematical thinking and solving abstract arithmetic problems [4] has been frequently investigated. Functional joint activity of related area to central executive network (CEN) is involved in mathematical problem solving [4–10]. The CEN involves cortical areas including the dorsolateral prefrontal cortex (DLPFC) and the posterior parietal cortex (PPC) [10]. However, other areas such as the anterior cingulate cortex (ACC), left inferior frontal gyrus (IFG), visual association cortex (VAC) and superior parietal lobule (SPL) are associated with executive function and are involved in the executive network [11].
Neuro-Ophthalmic Literature Review
Published in Neuro-Ophthalmology, 2021
David A. Bellows, Noel C. Y. Chan, John J. Chen, Hui-Chen Cheng, Peter W. MacIntosh, Jenny A. Nij Bijvank, Michael S. Vaphiades, Konrad P. Weber, Sui H. Wong
The authors reviewed the literature and from the 50 original papers found by searching for “visual snow,” they found 20 articles on pathophysiology and 15 on treatment with some overlap. Regarding pathophysiology, hyperexcitability of the visual cortex and a processing problem of higher order visual function are assumed, but the location is still in discussion. In particular, it is unclear if the primary visual cortex, the visual association cortex or the thalamocortical pathway is involved. Regarding treatment, data are available on a total of 153 patients with medication mentioned for 54 resulting in a total of 136 trials. From the 44 different medications tried, only eight were effective at least once. The best data is available for lamotrigine being effective in 8/36 (22.2%, including one total response and no worsening), followed by topiramate being effective in 2/13 (15.4%, no total response and one worsening). Amitriptyline resulted in worsening of the visual snow. The other medications reported to be effective were valproate, propranolol, verapamil, baclofen, naproxen and sertraline. The nonpharmacological approach used tinted glasses with colour filters of the yellow-blue colour.
Related Knowledge Centers
- Agnosia
- Primary Motor Cortex
- Prefrontal Cortex
- Schizophrenia
- Primary Sensory Areas