Glob (visual system)

Last updated

Globs are millimeter-sized color modules found beyond the visual area V2 in the brain's color processing ventral (also known as parvocellular) pathway. They are scattered throughout the posterior inferior temporal cortex in an area called the V4 complex. They are clustered by color preference, and organized as color columns. They are the first part of the brain in which color is processed in terms of the full range of hues found in color space. [1] [2]

Contents

The term "glob" was proposed by Bevil Conway and Doris Tsao [3] [1] on an analogy with the cytochrome-oxidase blobs of V1, an earlier stage in the hierarchical elaboration of color. [4] This also distinguishes them from other types of modules found elsewhere in the cerebral cortex such as face patches, and inferior temporal feature columns. [3] [1]

Properties

Globs are found in the V4 complex, an area in the inferior temporal cortex, forward of area V3, that includes areas V4, the dorsal part of the posterior inferior temporal cortex and the rear part of the inferior temporal near the occipital lobe called TEO. Their neurons are not restricted to a single color preference. Neurons in adjacent glob cells have similar color tuning and form clusters that are arranged spatially within the cortex. [1] In between them are ‘‘interglob’’ areas that were not color sensitive but respond to shape. [3]

The color-tuned neurons are arranged in color columns that are of a finer scale than single globs. These columns are between 50 and 100 μm in size. Color preferences of neurons recorded sequentially along given columns are arranged according to a chromotopic map that reflects perceptual color space. [1]

They are studied using functional MRI [3] and single-unit recording. [1]

Color perception

Three types of retinal cone create signals that get transformed in the visual pathway to create the perception of color. [1] [5] However the neurons processing them in the retina, lateral geniculate nucleus, and V1 and V2 early parts of the visual cortex encode using the opponent process only a limited range of colors that does not reflect the dimensions of perceptual color space. [6] It is only the next area where globs are found that along the visual processing hierarchy, show hue sensitivity, with the population of neurons representing most (if not all) of perceptual color space and which the color responses of neurons correspond to perception. [1] [3]

Related Research Articles

<span class="mw-page-title-main">Color</span> Visual perception of the light spectrum

Color or Colour is the visual perception based on the electromagnetic spectrum. Though color is not an inherent property of matter, color perception is related to an object's light absorption, reflection, emission spectra and interference. For most humans, colors are perceived in the visible light spectrum with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelength, such as bees that can distinguish ultraviolet, and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

<span class="mw-page-title-main">Visual cortex</span> Region of the brain that processes visual information

The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 (V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5.

<span class="mw-page-title-main">Hue</span> Property of a color

In color theory, hue is one of the main properties of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, orange, yellow, green, blue, violet," within certain theories of color vision.

<span class="mw-page-title-main">Color constancy</span> How humans perceive color

Color constancy is an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red. This helps us identify objects.

<span class="mw-page-title-main">Color vision</span> Ability to perceive differences in light frequency

Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity.

<span class="mw-page-title-main">Visual system</span> Body parts responsible for vision

The visual system is the physiological basis of visual perception. The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. The visual system is associated with the eye and functionally divided into the optical system and the neural system.

<span class="mw-page-title-main">Sensory nervous system</span> Part of the nervous system

The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons, neural pathways, and parts of the brain involved in sensory perception and interoception. Commonly recognized sensory systems are those for vision, hearing, touch, taste, smell, balance and visceral sensation. Sense organs are transducers that convert data from the outer physical world to the realm of the mind where people interpret the information, creating their perception of the world around them.

<span class="mw-page-title-main">Parietal lobe</span> Part of the brain responsible for sensory input and some language processing

The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.

Multisensory integration, also known as multimodal integration, is the study of how information from the different sensory modalities may be integrated by the nervous system. A coherent representation of objects combining modalities enables animals to have meaningful perceptual experiences. Indeed, multisensory integration is central to adaptive behavior because it allows animals to perceive a world of coherent perceptual entities. Multisensory integration also deals with how different sensory modalities interact with one another and alter each other's processing.

The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct visual systems. Recently there seems to be evidence of two distinct auditory systems as well. As visual information exits the occipital lobe, and as sound leaves the phonological network, it follows two main pathways, or "streams". The ventral stream leads to the temporal lobe, which is involved with object and visual identification and recognition. The dorsal stream leads to the parietal lobe, which is involved with processing the object's spatial location relative to the viewer and with speech repetition.

Ocular dominance columns are stripes of neurons in the visual cortex of certain mammals that respond preferentially to input from one eye or the other. The columns span multiple cortical layers, and are laid out in a striped pattern across the surface of the striate cortex (V1). The stripes lie perpendicular to the orientation columns.

The grandmother cell, sometimes called the "Jennifer Aniston neuron", is a hypothetical neuron that represents a complex but specific concept or object. It activates when a person "sees, hears, or otherwise sensibly discriminates" a specific entity, such as their grandmother. It contrasts with the concept of ensemble coding, where the unique set of features characterizing the grandmother is detected as a particular activation pattern across an ensemble of neurons, rather than being detected by a specific "grandmother cell".

<span class="mw-page-title-main">Inferior temporal gyrus</span> One of three gyri of the temporal lobe of the brain

The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface of the temporal lobe, where it is limited by the inferior sulcus. This region is one of the higher levels of the ventral stream of visual processing, associated with the representation of objects, places, faces, and colors. It may also be involved in face perception, and in the recognition of numbers and words.

<span class="mw-page-title-main">Colour centre</span> Brain region responsible for colour processing

The colour centre is a region in the brain primarily responsible for visual perception and cortical processing of colour signals received by the eye, which ultimately results in colour vision. The colour centre in humans is thought to be located in the ventral occipital lobe as part of the visual system, in addition to other areas responsible for recognizing and processing specific visual stimuli, such as faces, words, and objects. Many functional magnetic resonance imaging (fMRI) studies in both humans and macaque monkeys have shown colour stimuli to activate multiple areas in the brain, including the fusiform gyrus and the lingual gyrus. These areas, as well as others identified as having a role in colour vision processing, are collectively labelled visual area 4 (V4). The exact mechanisms, location, and function of V4 are still being investigated.

In cognitive neuroscience, visual modularity is an organizational concept concerning how vision works. The way in which the primate visual system operates is currently under intense scientific scrutiny. One dominant thesis is that different properties of the visual world require different computational solutions which are implemented in anatomically/functionally distinct regions that operate independently – that is, in a modular fashion.

<span class="mw-page-title-main">Posterior parietal cortex</span> Part of the human brain

The posterior parietal cortex plays an important role in planned movements, spatial reasoning, and attention.

<span class="mw-page-title-main">Parasol cell</span>

A parasol cell, sometimes called an M cell or M ganglion cell, is one type of retinal ganglion cell (RGC) located in the ganglion cell layer of the retina. These cells project to magnocellular cells in the lateral geniculate nucleus (LGN) as part of the magnocellular pathway in the visual system. They have large cell bodies as well as extensive branching dendrite networks and as such have large receptive fields. Relative to other RGCs, they have fast conduction velocities. While they do show clear center-surround antagonism, they receive no information about color. Parasol ganglion cells contribute information about the motion and depth of objects to the visual system.

Bevil Conway, is a Zimbabwean neuroscientist, visual artist, and an expert in color. Conway specialises in visual perception in his scientific work, and he often explores the limitations of the visual system in his artwork. At Wellesley College, Conway was Knafel Assistant Professor of Natural Science from 2007 to 2011, and associate professor of Neuroscience until 2016. He was a founding member of the Neuroscience Department at Wellesley. Prior to joining the Wellesley faculty, Conway helped establish the Kathmandu University Medical School in Nepal, where he taught as assistant professor in 2002–03. He currently runs the Sensation, Cognition and Action Unit in the Laboratory of Sensorimotor Research at the National Eye Institute and the National Institute of Mental Health.

Binocular neurons are neurons in the visual system that assist in the creation of stereopsis from binocular disparity. They have been found in the primary visual cortex where the initial stage of binocular convergence begins. Binocular neurons receive inputs from both the right and left eyes and integrate the signals together to create a perception of depth.

<span class="mw-page-title-main">Ventrolateral prefrontal cortex</span> Part of the prefrontal cortex of the brain

The ventrolateral prefrontal cortex (VLPFC) is a section of the prefrontal cortex located on the inferior frontal gyrus, bounded superiorly by the inferior frontal sulcus and inferiorly by the lateral sulcus. It is attributed to the anatomical structures of Brodmann's area (BA) 47, 45 and 44.

References

  1. 1 2 3 4 5 6 7 8 Conway BR, Tsao DY (2009). "Color-tuned neurons are spatially clustered according to color preference within alert macaque posterior inferior temporal cortex". Proc Natl Acad Sci U S A. 106 (42): 18035–18039. Bibcode:2009PNAS..10618034C. doi: 10.1073/pnas.0810943106 . PMC   2764907 . PMID   19805195.
  2. ↑ Bohon, Hermann, Conway (2016). "Representation of perceptual color space in macaque posterior inferior temporal cortex (the V4 Complex)". eNeuro. 3 (4): ENEURO.0039–16.2016. doi:10.1523/ENEURO.0039-16.2016. PMC   5002982 . PMID   27595132.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. 1 2 3 4 5 Conway BR, Moeller S, Tsao DY (2007). "Specialized color modules in macaque extrastriate cortex" (PDF). Neuron. 56 (3): 560–73. doi:10.1016/j.neuron.2007.10.008. PMC   8162777 . PMID   17988638. S2CID   11724926. Archived from the original (PDF) on 2021-03-02. Retrieved 2020-08-28.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ↑ Livingstone MS, Hubel DH (1984). "Anatomy and physiology of a color system in the primate visual cortex". J Neurosci. 4 (1): 309–56. doi:10.1523/jneurosci.04-01-00309.1984. PMC   6564760 . PMID   6198495.
  5. ↑ Conway BR (2009). "Color vision, cones, and color-coding in the cortex". Neuroscientist. 15 (3): 274–90. doi:10.1177/1073858408331369. PMID   19436076. S2CID   9873100.
  6. ↑ Conway BR (2001). "Spatial structure of cone inputs to color cells in alert macaque primary visual cortex (V-1)". J Neurosci. 21 (8): 2768–83. doi:10.1523/jneurosci.21-08-02768.2001. PMC   6762533 . PMID   11306629.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.