China
Africa
Explore chapters and articles related to this topic
The Biological Bases of Photoreception in the Process of Image Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
In this way, visual information is transmitted to the lateral geniculate nucleus of the thalamus (a gate controlling passage of information to the primary visual cortex in the occipital lobe). In this nucleus, color-sensitive projection neurons have the same receptive field organization as those found in ganglion cells. At the level of the cortex, color-sensitive neurons and the organization of their receptive fields differ from the previously described mechanisms. Color opponency appears within the center and surround of the receptive field and also between the center and surround (double-opponent color-sensitive cells). Some cortical neurons are orientation-selective and motion-sensitive. The primary visual cortex carries out an analysis of the visual field for a variety of aspects of visual stimuli, such as orientation, direction of movement, and object color [Matthews 1998]. Further, visual information is transmitted to higher-order cortical areas – anterior to the primary visual cortex – for the processing of specialized information. Such functions as the processing of object form, color, or motion project to more specialized areas in a more anterior part of the occipital lobe and the posterior part of the temporal lobe cortex [Matthews 1998].
Visual Perception
Published in Robert W. Proctor, Van Zandt Trisha, Human Factors in Simple and Complex Systems, 2018
Robert W. Proctor, Van Zandt Trisha
Once the optic nerve leaves the eye, visual signals become progressively more refined. The optic nerve splits, sending half of the information from each eye to one half of the brain and the other half to the other. Information about objects located in the right visual field first goes to the left half of the brain, while information about objects in the left visual field goes to the right half of the brain. These separate signals are put back together later in processing. After passing through a region of the thalamus called the lateral geniculate nucleus (LGN), where the parvocellular and magnocellular pathways are kept distinct and all neurons are monocular (i.e., they respond to light at only one eye), the next stop for visual information is the primary visual cortex. Put your hand on the back of your neck: the bump from your skull that hits the top edge of your hand is approximately where the visual cortex is located.
Three-dimensional structures
Published in David Crawley, Konstantin Nikolić, Michael Forshaw, 3D Nanoelectronic Computer Architecture and Implementation, 2020
In the present context, the detailed structure of the animal visual cortex is of relatively little concern. What is relevant is that the retina of each human eye has about 7 × 106 colour-sensitive cones, used for high spatial acuity vision at high light (daylight) levels, and about 120 × 106 rods, used for low light level (night) vision (e.g. [3]). Thus, the equivalent digital input data rate is, very approximately, 2 × 130 × 106 bits of information every 20–40 ms—about 1010 bit s−1. This may be compared with the ~109 bit s−1 in a high-resolution colour TV camera. However, a significant amount of low-level processing is carried out in the retina and subsequently in the lateral geniculate nucleus (LGN), so that perhaps 2 × 106 signals from each eye are fed to the cortex for subsequent processing. The angular resolution of the ‘pixels’ of the human eye varies from the high resolution of the fovea (~ 1 mrad over a few degrees) to less than one degree at the edge of the field of vision. There is no high-speed synchronizing clock in the human brain but the 4 × 106 bits (approximately) of information emerging from the LGN are initially processed by cortical neurons with a time constant of perhaps 20 ms. The data rate at the input to the visual cortex is, therefore, approximately 2 × 108 bit s−1. Thereafter, some 2 × 108 neurons, with a total of perhaps 2 × 1012 synapses, are used to carry out all of the visual processing tasks that are needed for the animal to survive.
Hybrid deep learning algorithm for brain tumour detection
Published in The Imaging Science Journal, 2022
Jyoti Srivastava, Jay Prakash, Ashish Srivastava
Sophisticated CNN-based segmentation and classification techniques for pictures of meningiomas, gliomas, and glioblastomas are being developed. A case of a pituitary tumour is described. When working at CNN, you have only three options regarding how you want to process information. This tumour classification multiscale processing paradigm was inspired by the HVS's multiscale operations. HVS with the suggested model goes along like peaches and cream. The human visual system uses pre- and post-attentive modes of processing when processing visual inputs (HVS). Pre-attentional processing generates a serial search that covers a large visual field through fast and concurrent pre-attentional processing. Frequency and bandwidth are used by the V1 area of the visual cortex to filter inputs from the LGN (Lateral Geniculate Nucleus). The inferotemporal region (ITR) is responsible for concatenating the information processed during the cognitive process. U-net or any other sliding window technique is not required; the entire image can be used as input. In image processing, segmentation [15] is a common technique. Many programs that use digital images or objects necessitate exceedingly fine segmentation. The image can be reduced to its component pixels. The art of image segmentation is a difficult one to master. Image segmentation can be interpreted in numerous ways. Applied fields such as computer vision, medical imaging, and remote sensing utilize the term. All photo analysis methods use this method. There is a collection of articles here about picture segmentation Figure 1.
A Review of Human Physiological Responses to Light: Implications for the Development of Integrative Lighting Solutions
Published in LEUKOS, 2022
Céline Vetter, P. Morgan Pattison, Kevin Houser, Michael Herf, Andrew J. K. Phillips, Kenneth P. Wright, Debra J. Skene, George C. Brainard, Diane B. Boivin, Gena Glickman
From the retina, light information is transmitted to multiple targets in the human brain via two major pathways. The visual pathway employs the optic nerve, chiasm and tract, which sends information to structures involved in image formation, including the lateral geniculate nucleus (LGN), intergeniculate leaflet (IGL) and visual cortex of the occipital lobe. The retinohypothalamic tract (RHT) is responsible for carrying light information from the retina to the suprachiasmatic nuclei (SCN) in the hypothalamus. The SCN serves as the biological clock in mammals and has numerous downstream connections with other central nervous system structures, including the spinal cord and brain (e.g. septum, thalamus, midbrain and other regions of the hypothalamus). The RHT also projects to other nonvisual nuclei and regulatory centers of the brain that are independent of the circadian pacemaker (Gooley et al. 2003; Hattar et al. 2006).
Tutorial: Theoretical Considerations When Planning Research on Human Factors in Lighting
Published in LEUKOS, 2019
Vision starts in the eye and requires light. Photoreceptors in the outer layer of the retina—the well-known rods and cones—absorb light particles and transduce photic information to neural signals that travel to the optic chiasm via the optic nerve. The retina consists of multiple layers of neurons that are tightly interconnected. These interconnections are the means through which light processing starts immediately, including, for instance, contrast detection, color processing, and very quick adaptation to local and ambient light levels. Typically such processing continues deeper in the brain, but the initiation in the retina implies that, rather than transferring direct pixel-based information like a digital camera, the optic nerve transports preprocessed light information, having already converted individual photoreceptor inputs into, for instance, light- and color channel–based data and accentuating color and light contrasts (both spatial and temporal), which are important for fast downstream (deeper in the brain) detection of, for instance, borders and shapes; that is, object detection. From there, light information takes different routes into the brain. The pathway mainly responsible for vision is that from the optic chiasm, via the lateral geniculate nucleus to the visual cortex. Once the signals reach the cortex, we become consciously aware of them; in other words, we see.