An Introduction to Consciousness and the Brain
Max R. Bennett in The Idea of Consciousness, 2020
Working in Dublin in 1944, during the Second World War, Erwin Schrodinger published a book which had an enormous influence on the history of biological science in the second half of the twentieth century. After the Second World War, some of the brightest physicists decided not to go into theoretical physics but instead to try their hand at biology. The identity of objects and their color is taken up by a set of retinal ganglion cells and conveyed via the structure called the dorsal lateral geniculate of the thalamus, which acts as an interface between the external world and the neocortex, to the primary visual (or striate) cortex in the occipital lobe at the back of the head. The other main projecting pathway is concerned with determining where an object is located in visual space. Hypertension leads to a breakdown of the vasculature and hence to vascular stroke resulting in the destruction of certain parts of the brain.
Optic radiations
Fiona Rowe in Visual Fields via the Visual Pathway, 2016
The optic radiations form the start of the second nerve fibre part of the visual pathway – the first part being the retinal nerve fibres that pass from the retinae to the lateral geniculate body where they synapse. The blood supply to the optic radiations is predominantly from the posterior and middle cerebral arteries. The optic radiations pass through a large area of the posterior cranial cavity including the temporal and parietal lobes before reaching their termination in the occipital lobe. Optic radiation lesions are mostly vascular related to either the posterior cerebral artery or middle cerebral artery territories. Temporal and parietal lobe lesions can cause higher cortical deficits including complex partial seizures, auditory or complex visual hallucinations, memory problems or a Wernicke’s aphasia. Defective associate visual processing includes visual agnosia, simultanagnosia, prosopagnosia, complex formed visual hallucinations, alexia, right/left confusion and inability to recognize colours and colour matching.
Visual defects as a result of occipital lesions
John Harrison, Adrian Owen in Cognitive Deficits in Brain Disorders, 2002
The occipital lobes are of fundamental importance in vision. All visual information enters the eye in an undiscriminated form, and is systematically processed so that different attributes, namely form, color, motion orientation and depth, are processed at distinct locations within functionally specialized regions in the visual cortex. These fragments of information are meaningfully integrated so that perceptual and cognitive representations of objects being viewed and their spatial relations to each other are constructed. Since the visual cortex lies within the occipital lobes, characteristic visual syndromes can be recognized as a result of occipital lesions which, if small enough, can cause blindness for a single class of vision. As a result of studies of patients with such focal cortical lesions and artificial lesion work in non-human primates, recent years have seen a great expansion of knowledge about the mechanisms by which the visual world is re-created in the brain.
Homonymous Horizontal Sectoranopia Caused by an Occipital Lobe Infarct
Published in Neuro-Ophthalmology, 2020
Janine M. Preble, Aliza Epstein, Justin Tannir, Robert Tomsak
Homonymous horizontal sectoranopia is a rare visual field defect that characteristically occurs after damage to the lateral geniculate nucleus (LGN). While there are many reports of homonymous horizontal sectoranopia resulting from LGN damage, there are very few reports of homonymous horizontal sectoranopia resulting from damage to other areas of the brain. We present a unique case of a patient with a homonymous horizontal sectoranopia with an occipital lobe infarct. Visual field and radiologic findings are presented. To our knowledge, this is one of the few reported cases of homonymous horizontal sectoranopia resulting from an infarct to the occipital lobe.
Relative Afferent Pupillary Defects in Homonymous Visual Field Defects Caused by Stroke of the Occipital Lobe Using Pupillometer
Published in Neuro-Ophthalmology, 2018
Go Takizawa, Atsushi Miki, Fumiatsu Maeda, Katsutoshi Goto, Syunsuke Araki, Tsutomu Yamashita, Yoshiaki Ieki, Junichi Kiryu, Kiyoshi Yaoeda
Relative afferent pupillary defects (RAPD) may be detected in patients with occipital lobe lesions. However, no previous report has used an objective technique to record the abnormal pupillary light reflex in such cases. Therefore, we measured the pupillary light reflex objectively in 15 patients with homonymous visual field defects (HVFD) due to occipital stroke using a new pupillometer. This study detected significantly smaller and slower pupillary light reflexes in the contralateral eyes than in the other eyes, which is equivalent to the presence of RAPD in patients with HVFDs caused by retrogeniculate lesions using an objective technique. Our results confirmed those of the previous reports using the swinging flashlight test more objectively.
Occipital lobe epilepsy was presented in a patient with intracerebral schwannoma: a case report and literature review
Published in International Journal of Neuroscience, 2019
Hirotomo Ten, Koji Adachi, Fumio Yamaguchi, Akira Matsuno, Akira Teramoto, Akio Morita
Schwannoma arising within brain parenchyma is a rare scenario. So far, only 70 cases were reported. We reported a case of intracerebral schwannoma presented with occipital lobe epilepsy, which has never been reported before. A 19-year-old man suffered from intermittent blurred vision and headache. Neuroradiological findings showed a left occipital lesion with cystic and solid components. Histological and electron micrograph features confirmed the diagnosis of schwannoma after the tumor was totally removed. The theories and literature related to this case were reviewed and the possible developmental origin was discussed. We found that this kind of schwannoma is more often in adolescent and young adults.