Ocular dominance columns are regions of neurons in the striate cortex that synapse with axons carrying transduced signals from either the left or right eye. The columns span multiple cortical layers, producing a striped pattern when the deeper levels are stained. Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Brodmann area 17 (primary visual cortex) is shown in red in this image which also shows area 18 (orange) and 19 (yellow) The primary visual cortex (usually called V1) is the most well-studied visual area in the brain. ... Closeup of a blue-green human eye. ...
Prior to birth, monocular transduction pathways are already established through a process known as “fire together, wire together.” Spontaneous retinal activity in one eye of the developing fetus leads to neuronal depolarization. Synapses that receive multiple inputs are more likely to propagate the signal, whereas errant connections will not be sufficient to trigger another action potential. Post-synaptic neurons that depolarize become permeable to calcium ions, if glutamate has been released by the pre-synaptic axon terminal. Calcium’s entry leads to a chemical process that strengthens the synapse, making it more likely to survive than other connections. The word transduction has several meanings: In developmental psychology, transduction is reasoning from specific cases to specific cases, typically employed by children. ... Human eye cross-sectional view. ... In biology, depolarization is the event a cell undergoes when its membrane potential grows more positive with respect to the extracellular solution. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ...
In a normally-developed visual system, the area of dominance columns for both eyes is the same, and each cortical cell responds to visual input according to its column. Monocular deprivation during early life prevents this balance from developing, and the non-deprived eye assumes control of nearly all cortical cells. These effects were identified by Torsten Wiesel and David Hubel, neuroscientists at Harvard Medical School, through studies on cats. Torsten Nils Wiesel (b. ... David Hunter Hubel (b. ... Trinomial name Felis silvestris catus (Linnaeus, 1758) The cat (or domestic cat, house cat) is a small carnivorous mammal and a subspecies of the wild cat. ...
The initial establishment of oculardominancecolumns in visual cortex is believed to involve the segregation of overlapping geniculocortical axons into eye-specific patches based on patterns of correlated activity.
We therefore propose that, unlike oculardominance plasticity during the critical period, the initial establishment of oculardominancecolumns relies primarily on activity-independent cues, rather than on specific patterns of correlated activity.
As an alternative to correlation-based models for oculardominance development, we propose that axons arising from each LGN layer are molecularly distinct, and that interaction with corresponding cortical cues determines the termination pattern of each set of axons.
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