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Cortical Visual Loss
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The traditional explanation of pure alexia is a disconnection between visual processing and language areas in the left hemisphere (117, 277). The most common scenario is a left occipital lesion that not only causes a complete right hemianopia but also extends anteriorly to destroy callosal fibers in the splenium, forceps major, or white matter around the occipital horn (278, 279), so that information from the right occipital lobe can't access language areas in the left hemisphere. White matter lesions under the left angular gyrus may disconnect all visual input to language processors without needing a right hemianopia (280–282). More unusual cases reflect the combination of a splenial lesion and a right hemianopia from non-occipital lesions, such as left geniculate infarction (283, 284) or demyelination of the left optic radiations (285). Other cases may not be a disconnection but a selective visual agnosia from damage to the left fusiform gyrus (278, 286, 287), which contains an area activated by letters or words, the “visual word form area” (288) (Figure 20.13). Damage to this area can impair reading (289–292), but so can lesions in other regions such as the left middle temporal gyrus, which are part of a reading network (293, 294).
Functional Image-Guided Neurosurgery
Published in Andrei I. Holodny, Functional Neuroimaging, 2019
Cameron W. Brennan, Nicole M. Petrovich Brennan
Lesions in the posterior portion of the superior or middle temporal gyri should be assessed for proximity to receptive language function, including the canonical Wernicke’s area (38,40). As with expressive language, location of receptive function varies widely among individuals (35). Here too, ECS plays a primary role in mapping intraoperatively. Subcortical stimulation of white matter, aided by DTI delineation of major tracts, may be of utility in stopping resection before injury to functional tracts (41).
Neuroimaging studies of individuals with Down syndrome
Published in Vee P. Prasher, Down Syndrome and Alzheimer’s Disease, 2018
Felix Beacher, Declan G. M. Murphy
A recent MRI study of non-demented subjects with DS reported that cross-sectional area of the corpus callosum was significantly positively correlated with overall cognitive function as measured by the Peabody Picture Vocabulary Test, Revised.60 Corpus callosum atrophy is proposed to be a marker of neocortical atrophy in the AD brain.61 Teipel and colleagues62 therefore inferred that callosal atrophy may indicate more general neocortical atrophy in non-demented individuals with DS. VBM analysis of the same data showed significant correlations between memory performance (but not overall cognitive ability) and grey matter volume of the left superior and middle temporal gyrus, bilateral precuneus, left hippocampus, right middle temporal gyrus and right middle frontal gyrus.63 Thus the biological validity of the reported correlations between overall cognitive function and cross-sectional area of the corpus callosum is probably low.
Reemergence of the language network during recovery from severe traumatic brain injury: A pilot functional MRI study
Published in Brain Injury, 2021
Brian J. Coffey, Zachary D. Threlkeld, Andrea S. Foulkes, Yelena G. Bodien, Brian L. Edlow
In this pilot study of patients with severe TBI who recovered basic language function, we observed longitudinal increases in fMRI responses to spoken language within the STGL, right supramarginal gyrus, and right middle temporal gyrus. Although longitudinal increases in fMRI responses to speech were observed across all a priori selected ROIs, these changes did not reach statistical significance in the STGR, IFGR, and IFGL after correction for multiple comparisons. Due to the small sample size and multiple limitations detailed below, the findings in this study are preliminary. Nevertheless, the results suggest that, during recovery from severe TBI, changes within cortical nodes of the canonical language network are nonuniform and that reemergence of the entire language network may not be necessary to support recovery of language function. While the mechanistic contributions of the right supramarginal and right middle temporal gyri to language recovery are not fully understood, the supramarginal gyrus is connected to both the IFG and STG by branches of the arcuate fasciculus (37) and is believed to integrate the auditory representation of spoken words with their meaning (38). Evidence from fMRI and transcranial magnetic stimulation studies indicate that the middle temporal gyrus also contributes to comprehension of spoken and written words (39–41). Collectively, these findings provide evidence that recovery of language after severe TBI is associated with reemergence of responses within and outside the canonical language network.
An Exploratory Study on the Central Nervous Correlates of Sexual Excitation and Sexual Inhibition
Published in The Journal of Sex Research, 2020
K. Unterhorst, H. Gerwinn, A. Pohl, C. Kärgel, C. Massau, I. Ristow, J. Kneer, T. Amelung, H. Walter, K. Beier, M. Walter, B. Schiffer, T. H. C. Kruger, A. Stirn, J. Ponseti
Arnow et al. (2002) investigated the relationship between brain activity and sexual arousal and found correlations in many of the brain areas we found, the major difference being that they used penile turgidity as a regressor, whereas we used trait sexual excitation and inhibition. The regions found in both studies were the right middle temporal gyrus, bilateral cingulate cortices, occipital, premotor, and somatosensory areas. The correlations we found in medial and superior occipital and inferior and medial temporal areas can be attributed to the general processing of visual stimuli, indicating that participants who scored higher in sexual excitation have a stronger processing of VSS. Activations of occipitotemporal areas have occurred often in functional brain imaging studies investigating temporal sexual arousal (Stoléru & Mouras, 2007). According to the two streams hypothesis (Goodale & Milner, 1992), the occipitotemporal cortex is part of the ventral stream of visual processing. It winds up in the inferotemporal cortex and is also referred to as the “what pathway.” It is involved in object identification and recognition and is not specific to the presentation of sexual stimuli.
Neuroanatomical and behavioural factors associated with the effectiveness of two weekly sessions of prism adaptation in the treatment of unilateral neglect
Published in Neuropsychological Rehabilitation, 2020
Maria Gutierrez-Herrera, Simone Eger, Ingo Keller, Joachim Hermsdörfer, Styrmir Saevarsson
Based on the median splits calculated for the improvement in performance at follow-up session in the LM-M and in the cancellation tasks, patients were consistently classified into groups with higher vs lower levels of improvement. To identify the brain regions that were predominantly involved in patients showing a low prism-related improvement in motor-related tasks, we subtracted the superimposed lesions of patients with a higher level improvement (n = 7; Figure 8, bottom panel) from those of patients with a lower level of improvement (n = 7; Figure 8, top panel). As indicated in Figure 9, an extended area could be defined were lesions were 57% more common in patients showing a lower performance improvement in motor-related tasks. This area included the right inferior and middle temporal gyri, thalamus, angular, and supramarginal gyri, postcentral gyrus, fusiform gyrus, and hippocampus. As for the opposite subtraction, brain regions including the right superior temporal gyrus, temporal pole, heschl gyrus, and superior, middle, and inferior frontal gyri were damaged 57% more often in patients with better performance improvement in motor-related tasks. Additionally, a higher percentage of overlap was observed in the insula, the putamen, and the rolandic operculum (71%) (Figure 9).1