Plasticity of Visual Cortex in Adult Primates
Jon H. Kaas, Christine E. Collins in The Primate Visual System, 2003
of each of the lateral geniculate nucleus layers that receive input from that eye. In cats, this would involve one of the two “A” layers, and one or more of the “C” layers, while in monkeys a monocular lesion would involve one of the two complete parvocellular layers (and its sublayers), one of the two magnocellular layers, and zones of koniocellular inputs. For simplicity, these layers for each eye are depicted in Figure 7.1 as a single layer, and the single layers for each eye are shown as adjacent rather than stacked, as they are in the lateral geniculate nucleus (LGN). The two layers (e.g., sets of layers) then project in matching patterns to primary visual cortex, V1. A monocular lesion obviously deprives each set of monocular LGN layers of all visual activation in a portion of the retinotopic map corresponding to the lesion, while the equivalent part of V1 is deprived of activation from only one eye. Obviously, the converging inputs from undeprived geniculate layers can compensate for the missing inputs. Matching lesions of both retinas, however, totally deprive both portions of LGN layers and a portion of V1. The basic experimental question addressed in the studies in cats and monkeys is what happens to the deprived neurons in the LGN and V1 after retinal lesions?
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
A lack of vision in one half of the visual field. The dividing line between the intact and blind hemifields is usually (but not always) vertical. There is a partial DECUSSATION of the optic fibres at the OPTIC CHIASM which lies between the eyeball and the LATERAL GENICULATE NUCLEUS. Half of the fibres project to the visual HEMISPHERE of the brain on the same (IPSILATERAL) side, and the other project to the visual hemisphere on the opposite (CONTRALATERAL) side. SECTION of the optic tract above the level of the chiasm therefore will lead to HOMONYMOUS HEMIANOPIA whereby both eyes will be affected, vision being lost in the TEMPORAL VISUAL HEMIFIELD in one eye and the NASAL VISUAL HEMIFIELD in the other. The exact pattern of hemianopia in the two eyes is a critical diagnostic tool for locating the site of a LESION in the visual pathway.
An Introduction to Consciousness and the Brain
Max R. Bennett in The Idea of Consciousness, 2020
Ten years ago my colleague Bogdan Dreher and I set out to see if what Levi-Montalcini had discovered for the peripheral nervous system (namely that autonomic neurons could be induced to survive if provided with the material from their normal targets such as cardiac muscle or smooth muscle) might also apply for neurons in the central nervous system. We first showed that retinal ganglion cell neurons, the nerve cells in the retina that send visual information from it to the brain along the optic nerve (depicted in Figure 1.9), normally die during development. Furthermore, these retinal ganglion cells could be induced to survive when provided with a nutrient neurotrophic molecule from their targets in the brain. Those parts of the brain are called the superior colliculus and the lateral geniculate nucleus. The neurons survived and sprouted nerve processes profusely in a tissue culture plate if provided with the neurotrophic factor, just as Levi-Montalcini had described for autonomic neurons. The difference was that in this case, the retinal neurons were supplied with a factor from the brain and not from muscle. This was probably the first indication that neurotrophic growth factors exist in the brain and not just in the peripheral nervous system, and that these growth factors can allow for the survival and profuse axon spouting of a central neuron such as a retinal ganglion neuron.
Evaluating the safety profile of focused ultrasound and microbubble-mediated treatments to increase blood-brain barrier permeability
Published in Expert Opinion on Drug Delivery, 2019
Dallan McMahon, Charissa Poon, Kullervo Hynynen
Effects of FUS+MB-mediated BBB treatments on behavior have been thoroughly assessed in a small number of studies utilizing non-human primates. McDannold et al. conducted a comprehensive study in rhesus macaques using a clinical-prototype MRgFUS brain system (ExAblate 4000, InSightec) to investigate the effects of a range of acoustic power levels and MB injection/infusion parameters. Behavioral responses were evaluated by observing activities of daily living and visual function and acuity after repeated FUS+MB treatments to the lateral geniculate nucleus (relay system for the visual pathway) and primary visual cortex. After five successive volumetric (~1 cm3) treatments targeting the primary and secondary visual cortices bilaterally over the course of 5–9 weeks, visual performance, visual acuity, motor skills, and species-specific behaviors were unaffected, although a few hypointense regions in T2*-weighted images were observed [16].
Optical coherence tomography in the investigation of systemic neurologic disease
Published in Clinical and Experimental Optometry, 2019
Sangeetha Srinivasan, Nathan Efron
A decrease in macular volume has been noted in patients with multiple sclerosis,2009 more so in the nasal portions,2010 which may corroborate with compromised retinal nerve fibre layer thickness in the temporal quadrant as reported in a previous study.2017 Evangelou et al.2001 examined the size distribution of neurons in the magnocellular and parvocellular layers of the lateral geniculate body, and axonal densities of the anterior visual pathway. They observed that the distribution of neuron size in the lateral geniculate body was correlated with axonal densities in the visual pathway. In addition, they observed there were no significant differences in neuronal size distribution between patients and controls in magnocellular layers. In parvocellular layers, cell sizes were smaller in those with multiple sclerosis compared with those of healthy controls, suggesting that smaller axons may be susceptible to damage from multiple sclerosis.2001
Measuring abnormal intrinsic brain activities in patients with retinal detachment using amplitude of low-frequency fluctuation: a resting-state fMRI study
Published in International Journal of Neuroscience, 2019
Hong-Hua Kang, Yong-Qiang Shu, Lin Yang, Pei-Wen Zhu, Dan Li, Qing-Hai Li, You-Lan Min, Lei Ye, Qiong Zhou, Yi Shao
As the anatomical region of the visual cortex, the occipital lobe takes a part in visual coding. And the primary visual cortex (V1) is an important part of the occipital lobe, which receives signals from the lateral geniculate body [23]. The V1 processed visual information with decorrelation and sparse coding [24]. In addition, the V1 is relevant to visuospatial integration [25,26]. The normal function of the retinal ganglion cells is of great importance in visual stimulation. The pathological mechanism of RD is when the retinal neuroepithelium separates from the pigment epithelium [27], which leads to the disruption in visual signals transferring. In RD patients of this study, we demonstrated significantly decreased ALFF in their right occipital lobe, and it indicates the dysfunction of the visual cortex. Thus, we speculated that the RD patients might associate with the impairment in visual cortex.
Related Knowledge Centers
- Neuroanatomy
- Optic Nerve
- Optic Radiation
- Visual System
- Reticular Formation
- Thalamus
- Neuron
- Grey Matter
- White Matter
- Retinal Ganglion Cell