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Ocular Dominance Column
Ocular dominance columns are stripes of neurons in the visual cortex of certain mammals (including humans) 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. Ocular dominance columns were important in early studies of cortical plasticity, as it was found that monocular deprivation causes the columns to degrade, with the non-deprived eye assuming control of more of the cortical cells. It is believed that ocular dominance columns must be important in binocular vision. Surprisingly, however, many squirrel monkeys either lack or partially lack ocular dominance columns, which would not be expected if they are useful. This has led some to question whether they serve a purpose, or are just a byproduct of development. History Discovery Ocular dominance columns were discovered in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cortical Columns
A cortical column is a group of neurons forming a cylindrical structure through the cerebral cortex of the brain perpendicular to the cortical surface. The structure was first identified by Vernon Benjamin Mountcastle in 1957. He later identified minicolumns as the basic units of the neocortex which were arranged into columns. Each contains the same types of neurons, connectivity, and firing properties. Columns are also called hypercolumn, macrocolumn, functional column or sometimes cortical module. Neurons within a minicolumn (microcolumn) encode similar features, whereas a hypercolumn "denotes a unit containing a full set of values for any given set of receptive field parameters". A cortical module is defined as either synonymous with a hypercolumn (Mountcastle) or as a tissue block of multiple overlapping hypercolumns. Cortical columns are proposed to be the canonical microcircuits for predictive coding, in which the process of cognition is implemented through a hierarchy of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torsten Wiesel
Torsten Nils Wiesel (born 3 June 1924) is a Swedish Neurophysiology, neurophysiologist. With David H. Hubel, he received the 1981 Nobel Prize in Physiology or Medicine, for their discoveries concerning information processing in the visual system; the prize was shared with Roger W. Sperry for his independent research on the cerebral hemispheres. Career Wiesel was born in Uppsala, Sweden, in 1924, the youngest of five children. In 1947, he began his scientific career in Carl Gustaf Bernhard's laboratory at the Karolinska Institute, where he received his medical degree in 1954. He went on to teach in the institute's department of physiology and worked in the child psychiatry unit of the Karolinska Hospital. In 1955 he moved to the United States to work at Johns Hopkins School of Medicine under Stephen Kuffler. Wiesel began a fellowship in ophthalmology, and in 1958 he became an assistant professor. That same year, he met David Hubel, beginning a collaboration that would last over tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. Other ways of defining species include their karyotype, DNA sequence, morphology (biology), morphology, behaviour, or ecological niche. In addition, palaeontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses) are given a binomial nomenclature, two-part name, a "binomen". The first part of a binomen is the name of a genus to which the species belongs. The second part is called the specific name (zoology), specific name or the specific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expressivity (genetics)
In genetics, expressivity is the degree to which a phenotype is expressed by individuals having a particular genotype. Alternatively, it may refer to the expression of a particular gene by individuals having a certain phenotype. Expressivity is related to the ''intensity'' of a given phenotype; it differs from penetrance, which refers to the ''proportion'' of individuals with a particular genotype that share the same phenotype. Variable expressivity Variable expressivity refers to the phenomenon by which individuals with a shared genotype exhibit varying phenotypes. This can be further described as a spectrum of associated traits that can range in size, colour, intensity, and so forth. Variable expressivity can be seen in plants and animals, such as differences in hair colour, leaf size, and severity of diseases. Mechanisms influencing expressivity This variation in expression can be affected by modifier genes, epigenetic factors or the environment. # Modifier genes can a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squirrel Monkey
Squirrel monkeys are New World monkeys of the genus ''Saimiri''. ''Saimiri'' is the only genus in the subfamily Saimiriinae. The name of the genus is of Tupi origin (''sai-mirím'' or ''çai-mbirín'', with ''sai'' meaning 'monkey' and ''mirím'' meaning 'small') and was also used as an English name by early researchers. Squirrel monkeys live in the tropical forests of Central and South America in the canopy layer. Most species have parapatric or allopatric ranges in the Amazon, while ''S. oerstedii'' is found disjunctly in Costa Rica and Panama. There are two main groups of squirrel monkeys recognized. They are differentiated based on the shape of the white coloration above the eyes. In total there are five recognized species. Squirrel monkeys have short and close fur colored black at the shoulders, yellow or orange fur along the back and extremities, and white on the face. Squirrel monkeys have determined breeding seasons which involve large fluctuations in hormones and th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macaques
The macaques () constitute a genus (''Macaca'') of gregarious Old World monkeys of the subfamily Cercopithecinae. The 23 species of macaques inhabit ranges throughout Asia, North Africa, and Europe (in Gibraltar). Macaques are principally frugivorous (preferring fruit), although their diet also includes seeds, leaves, flowers, and tree bark. Some species such as the long-tailed macaque (''M. fascicularis''; also called the crab-eating macaque) will supplement their diets with small amounts of meat from shellfish, insects, and small mammals. On average, a southern pig-tailed macaque (''M. nemestrina'') in Malaysia eats about 70 large rats each year. All macaque social groups are arranged around dominant matriarchs. Macaques are found in a variety of habitats throughout the Asian continent and are highly adaptable. Certain species are synanthropic, having learned to live alongside humans, but they have become problematic in urban areas in Southeast Asia and are not suitable t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferrets
The ferret (''Mustela furo'') is a small, domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European polecat (''Mustela putorius''), as evidenced by the ferret's ability to interbreed with European polecats and produce hybrid offspring. Physically, ferrets resemble other mustelids because of their long, slender bodies. Including their tail, the average length of a ferret is about ; they weigh between ; and their fur can be black, brown, white, or a mixture of those colours. The species is sexually dimorphic, with males being considerably larger than females. Ferrets may have been domesticated since ancient times, but there is widespread disagreement because of the sparseness of written accounts and the inconsistency of those which survive. Contemporary scholarship agrees that ferrets were bred for sport, hunting rabbits in a practice known as rabbiting. In North America, the ferret has become an increasingly pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cats
The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the domestication of the cat occurred in the Near East around 7500 BC. It is commonly kept as a pet and working cat, but also ranges freely as a feral cat avoiding human contact. It is valued by humans for companionship and its ability to kill vermin. Its retractable claws are adapted to killing small prey species such as mice and rats. It has a strong, flexible body, quick reflexes, and sharp teeth, and its night vision and sense of smell are well developed. It is a social species, but a solitary hunter and a crepuscular predator. Cat intelligence is evident in their ability to adapt, learn through observation, and solve problems. Research has shown they possess strong memories, exhibit neuroplasticity, and display cognitive skill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Visual Cortex
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 (also known as V2, V3, V4, and V5, or Brodmann area 18 and all Brodmann area 19). Both hemispheres of the brain include a visual cortex; the visual cortex in the left hemisphere receives signals from the right visual field, and the visual cortex in the right hemisphere receives signals from the left visual field. Introduction The primary visual cortex (V1) is located in and around the calcarine fissure in the occipital lobe. Each hemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing#Evolution of hairlessness, hairlessness, bipedality, bipedalism, and high Human intelligence, intelligence. Humans have large Human brain, brains, enabling more advanced cognitive skills that facilitate successful adaptation to varied environments, development of sophisticated tools, and formation of complex social structures and civilizations. Humans are Sociality, highly social, with individual humans tending to belong to a Level of analysis, multi-layered network of distinct social groups — from families and peer groups to corporations and State (polity), political states. As such, social interactions between humans have established a wide variety of Value theory, values, norm (sociology), social norms, languages, and traditions (co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
