Glob (visual system)
Encyclopedia
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 column
s. They are the first part of the brain in which color is processed in terms of the full range of hue
s found in color space
.
The term "glob" was proposed by Bevil R. Conway
and Doris Y. Tsao on an analogy with the cytochrome-oxidase
blob
s of V1
, an earlier stage in the hierarchical elaboration of color. This also distinguishes them from other types of modules found elsewhere in the cerebral cortex
such as face patches, and inferior
temporal feature columns.
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. In between them are ‘‘interglob’’ ares that were not color sensitive but respond to shape.
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 a given the columns are arranged according to a chromotopic map that reflects perceptual color space
.
They are studied using functional MRI and single-unit recording
.
create signals that get transformed in the visual pathway to create the perception of color. 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. 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.
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
's color processing ventral
Two Streams hypothesis
The two-streams hypothesis is a widely accepted, but still controversial, account of visual processing. As visual information exits the occipital lobe, it follows two main channels, or "streams". The ventral stream travels to the temporal lobe and is involved with object identification...
(also known as parvocellular) pathway. They are scattered throughout the posterior inferior temporal cortex in an area called the V4 complex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
. They are clustered by color preference, and organized as color column
Cortical column
A cortical column, also called hypercolumn or sometimes cortical module, is a group of neurons in the brain cortex which can be successively penetrated by a probe inserted perpendicularly to the cortical surface, and which have nearly identical receptive fields...
s. They are the first part of the brain in which color is processed in terms of the full range of hue
Hue
Hue is one of the main properties of a color, defined technically , as "the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,"...
s found in color space
Color space
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components...
.
The term "glob" was proposed by Bevil R. Conway
Bevil Conway
Bevil Conway neuroscientist and artist. Conway specializes in visual perception in his scientific work, and he often explores the limitations of the visual system in his artwork. He is currently Knafel Assistant Professor at Wellesley College.Conway was educated at McGill University and Harvard...
and Doris Y. Tsao on an analogy with the cytochrome-oxidase
blob
Blob (visual system)
Blobs are sections of the visual cortex where groups of neurons that are sensitive to color assemble in cylindrical shapes. They were first identified in 1979 by Margaret Wong-Riley when she used a cytochrome oxidase stain, from which they get their name. These areas receive input from...
s of V1
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
, an earlier stage in the hierarchical elaboration of color. This also distinguishes them from other types of modules found elsewhere in the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
such as face patches, and inferior
temporal feature columns.
Properties
Globs are found in the V4 complex, an area in the inferior temporal cortex, forward of area V3, that includes areas V4, the dorsalDorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
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. In between them are ‘‘interglob’’ ares that were not color sensitive but respond to shape.
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 a given the columns are arranged according to a chromotopic map that reflects perceptual color space
Color space
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components...
.
They are studied using functional MRI and single-unit recording
Single-unit recording
In neurophysiology and neurology, single-unit recording is the use of an electrode to record the electrophysiological activity from a single neuron.-History:...
.
Color perception
Three types of retinal coneCone cell
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...
create signals that get transformed in the visual pathway to create the perception of color. However the neurons processing them in the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
, lateral geniculate nucleus
Lateral geniculate nucleus
The lateral geniculate nucleus is the primary relay center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain....
, and V1 and V2 early parts of the visual cortex encode using the opponent process
Opponent process
The color opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones and rods in an antagonistic manner...
only a limited range of colors that does not reflect the dimensions of perceptual color space. It is only the next area where globs are found that along the visual processing hierarchy, show hue
Hue
Hue is one of the main properties of a color, defined technically , as "the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,"...
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.