scholarly journals Quadrantanopia as the only symptom of post-COVID stroke in the occipital pole

Medicine ◽  
2021 ◽  
Vol 100 (44) ◽  
pp. e27542
Author(s):  
Katarzyna Baltaziak ◽  
Agata Szpringer ◽  
Aleksandra Czarnek-Chudzik ◽  
Maksymilian Onyszkiewicz ◽  
Mario Damiano Toro ◽  
...  
Keyword(s):  
Occipital Pole

scholarly journals Neural correlates of subsequent memory-related gaze reinstatement

2021 ◽  
Author(s):  
Jordana S. Wynn ◽  
Zhong-Xu Liu ◽  
Jennifer D. Ryan
Keyword(s):  
Eye Movements ◽  
Basal Ganglia ◽  
Recognition Memory ◽  
Visual Processing ◽  
Memory Task ◽  
Neural Correlates ◽  
Oculomotor Control ◽  
Related Activity ◽  
Pattern Similarity ◽  
Occipital Pole

AbstractMounting evidence linking gaze reinstatement- the recapitulation of encoding-related gaze patterns during retrieval- to behavioral measures of memory suggests that eye movements play an important role in mnemonic processing. Yet, the nature of the gaze scanpath, including its informational content and neural correlates, has remained in question. In the present study, we examined eye movement and neural data from a recognition memory task to further elucidate the behavioral and neural bases of functional gaze reinstatement. Consistent with previous work, gaze reinstatement during retrieval of freely-viewed scene images was greater than chance and predictive of recognition memory performance. Gaze reinstatement was also associated with viewing of informationally salient image regions at encoding, suggesting that scanpaths may encode and contain high-level scene content. At the brain level, gaze reinstatement was predicted by encoding-related activity in the occipital pole and basal ganglia, neural regions associated with visual processing and oculomotor control. Finally, cross-voxel brain pattern similarity analysis revealed overlapping subsequent memory and subsequent gaze reinstatement modulation effects in the parahippocampal place area and hippocampus, in addition to the occipital pole and basal ganglia. Together, these findings suggest that encoding-related activity in brain regions associated with scene processing, oculomotor control, and memory supports the formation, and subsequent recapitulation, of functional scanpaths. More broadly, these findings lend support to Scanpath Theory’s assertion that eye movements both encode, and are themselves embedded in, mnemonic representations.

Occipital Pole Area and Language Dominance

1997 ◽  
Vol 7 (2) ◽  
pp. 89-91 ◽  
Author(s):  
Philip David Charles ◽  
Bassel Abou-Khalil ◽  
Mustafa Bakar ◽  
Christina L. Mayville ◽  
Denis S. Atkinson ◽  
...  
Keyword(s):  
Language Dominance ◽  
Occipital Pole

scholarly journals The Mechanism of Macular Sparing

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jonathan C. Horton ◽  
John R. Economides ◽  
Daniel L. Adams
Keyword(s):  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Posterior Cerebral Artery ◽  
Occipital Lobe ◽  
Collateral Flow ◽  
Dual Representation ◽  
Field Representation ◽  
Occipital Pole ◽  
The Impact ◽  
Macular Sparing

Patients with homonymous hemianopia sometimes show preservation of the central visual fields, ranging up to 10°. This phenomenon, known as macular sparing, has sparked perpetual controversy. Two main theories have been offered to explain it. The first theory proposes a dual representation of the macula in each hemisphere. After loss of one occipital lobe, the back-up representation in the remaining occipital lobe is postulated to sustain ipsilateral central vision in the blind hemifield. This theory is supported by studies showing that some midline retinal ganglion cells project to the wrong hemisphere, presumably driving neurons in striate cortex that have ipsilateral receptive fields. However, more recent electrophysiological recordings and neuroimaging studies have cast doubt on this theory by showing only a minuscule ipsilateral field representation in early visual cortical areas. The second theory holds that macular sparing arises because the occipital pole, where the macula is represented, remains perfused after occlusion of the posterior cerebral artery because it receives collateral flow from the middle cerebral artery. An objection to this theory is that it cannot account for reports of macular sparing in patients after loss of an entire occipital lobe. On close scrutiny, such reports turn out to be erroneous, arising from inadequate control of fixation during visual field testing. Patients seem able to detect test stimuli on their blind side within the macula or along the vertical meridian because they make surveillance saccades. A purported treatment for hemianopia, called vision restoration therapy, is based on this error. The dual perfusion theory is supported by anatomical studies showing that the middle cerebral artery perfuses the occipital pole in many individuals. In patients with hemianopia from stroke, neuroimaging shows preservation of the occipital pole when macular sparing is present. The frontier dividing the infarcted territory of the posterior cerebral artery and the preserved territory of the middle cerebral artery is variable, but always falls within the representation of the macula, because the macula is so highly magnified. For physicians, macular sparing was an important neurological sign in acute hemianopia because it signified a posterior cerebral artery occlusion. Modern neuroimaging has supplanted the importance of that clinical sign but at the same time confirmed its validity. For patients, macular sparing remains important because it mitigates the impact of hemianopia and preserves the ability to read fluently. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals rTMS treatment of visual hallucinations using a connectivity- based targeting method - A case-study

2019 ◽  
Author(s):  
Azzurra Invernizzi ◽  
Hinke N. Halbertsma ◽  
Martijn van Ackooij ◽  
Leonie Bais ◽  
Jeffrey M. Boertien ◽  
...  
Keyword(s):  
Repetitive Transcranial Magnetic Stimulation ◽  
Fmri Data ◽  
Connectivity Pattern ◽  
Single Subject ◽  
Target Area ◽  
Visual Hallucinations ◽  
Eigenvector Centrality ◽  
Optimal Target ◽  
Occipital Pole

Visual hallucinations (VH) are difficult to treat because pharmacological interventions are only partially effective and associated with many adverse effects. One of the alternative non-pharmacological treatments for VH is repetitive transcranial magnetic stimulation (rTMS). However, identifying optimal stimulation sites for rTMS is challenging. To determine whether a connectivity-based targeting approach based on resting state (rs) fMRI data can be used to identify regions that may serve as effective rTMS targets. We acquired rs-fMRI scans pre-rTMS and post-rTMS in a single patient with retinitis pigmentosa (near blindness), Parkinson’s disease (PD) and had therapy-resistant VH. Rs-fMRI data were analyzed using fast Eigenvector Centrality Mapping (ECM). A target area was selected based on high ECM values and relative accessibility for rTMS. Subsequently, the patient was stimulated with 1 Hz rTMS during 5 days, followed by 30 Hz theta-burst stimulation during another 5 days. Distributions of surrogate and bootstrap data were used to statistically evaluate the effect of rTMS. The bilateral supplementary motor areas (SMA) were selected as rTMS target areas. When pre-rTMS were compared to post-rTMS, different ECM values were found in the SMA, precuneus, occipital pole and hippocampus. Clinical evaluation and follow-up showed that the intensity and frequency of the VH were decreased after rTMS. Our connectivity-based targeting approach applied to rs-fMRI data seems to be successful in identifying an optimal target area for rTMS on a single subject basis. Our results show changes in the connectivity pattern, both in the target area and associated hubs involved in VH pathogenesis.

scholarly journals Hemispherectomy for Seizures Revisited

1983 ◽  
Vol 10 (2) ◽  
pp. 71-78 ◽  
Author(s):  
Theodore Rasmussen
Keyword(s):  
Postoperative Complication ◽  
Late Complication ◽  
Therapeutic Effectiveness ◽  
Neurologic Deterioration ◽  
Highly Effective ◽  
Occipital Pole ◽  
Refractory Seizures ◽  
The Cost ◽  
The Brain

SUMMARY:The serious, late complication of superficial cerebral hemosiderosis, which appears after several years in 1/4–1/3 of patients who have undergone hemispherectomy, has resulted in recent years in a considerable reluctance to carry out this operation despite the fact it has proved to be highly effective in patients with medically refractory seizures associated with hemiplegia. Preservation of a small portion of the hemisphere, usually the frontal or occipital pole, has proved to be effective in preventing this late complication, but at the cost of a significant reduction in the effectiveness of the operation in reducing the patients’ seizure tendency. Preserving the frontal and occipital poles but disconnecting them from the rest of the brain, resulting in a functional complete but anatomical subtotal hemispherectomy, retains the therapeutic effectiveness of a complete hemispherectomy while still protecting adequately against the serious late postoperative complication of superficial cerebral hemosiderosis and its associated neurologic deterioration, hydrocephalus and sometimes death.

scholarly journals Left Parietal Craniotomy for Resection of Grade IV Arteriovenous Malformation: 2-Dimensional Operative Video

2020 ◽  
Vol 18 (4) ◽  
pp. E113-E113
Author(s):  
Benjamin K Hendricks ◽  
Robert F Spetzler
Keyword(s):  
Cerebral Artery ◽  
Video Recording ◽  
Complete Removal ◽  
Complete Recovery ◽  
Preoperative Embolization ◽  
Institutional Review ◽  
Postcentral Gyrus ◽  
Feeding Vessels ◽  
Martin Grade ◽  
Occipital Pole

Abstract Parieto-occipital arteriovenous malformations (AVMs) are the second most common site for cranial AVMs. These lesions are defined as eloquent when the nidus involves either the postcentral gyrus or the occipital pole. If located on the dominant hemisphere, these lesions can also involve the arcuate fasciculus ventrally. This patient had a large unruptured Spetzler-Martin grade IV AVM within the parieto-occipital region extending deeply to the ventricle, following presentation with a seizure. The digital subtraction angiography demonstrated feeding vessels from both the middle cerebral artery and posterior cerebral artery distributions. Despite the high Spetzler-Martin grade, the lesion demonstrated favorable features such as a compact nidus, convexity presence, and lack of involvement of the precentral and postcentral gyrus. Preoperative embolization was utilized. The AVM was successfully resected both superficially and deeply to the level of the atrium of the lateral ventricle. Postoperative angiography demonstrated complete removal of the AVM, and the patient made a complete recovery from the procedure. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

scholarly journals The generation and propagation of the human alpha rhythm

2019 ◽  
Vol 116 (47) ◽  
pp. 23772-23782 ◽  
Author(s):  
Milan Halgren ◽  
István Ulbert ◽  
Hélène Bastuji ◽  
Dániel Fabó ◽  
Lorand Erőss ◽  
...  
Keyword(s):  
Somatosensory Cortex ◽  
Lower Order ◽  
Short Range ◽  
Alpha Rhythm ◽  
Higher Order ◽  
Cortical Layers ◽  
Posterior Cortex ◽  
Quiet Wakefulness ◽  
Occipital Pole ◽  
Thalamocortical System

The alpha rhythm is the longest-studied brain oscillation and has been theorized to play a key role in cognition. Still, its physiology is poorly understood. In this study, we used microelectrodes and macroelectrodes in surgical epilepsy patients to measure the intracortical and thalamic generators of the alpha rhythm during quiet wakefulness. We first found that alpha in both visual and somatosensory cortex propagates from higher-order to lower-order areas. In posterior cortex, alpha propagates from higher-order anterosuperior areas toward the occipital pole, whereas alpha in somatosensory cortex propagates from associative regions toward primary cortex. Several analyses suggest that this cortical alpha leads pulvinar alpha, complicating prevailing theories of a thalamic pacemaker. Finally, alpha is dominated by currents and firing in supragranular cortical layers. Together, these results suggest that the alpha rhythm likely reflects short-range supragranular feedback, which propagates from higher- to lower-order cortex and cortex to thalamus. These physiological insights suggest how alpha could mediate feedback throughout the thalamocortical system.

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