Orientation columns

Orientation columns are organized regions of neurons that are excited by visual line stimuli of varying angles. These columns are located in the primary visual cortex (V1) and span multiple cortical layers. The geometry of the orientation columns are arranged in slabs that are perpendicular to the surface of the primary visual cortex.

In 1958, David Hubel and Torsten Wiesel discovered cells in the visual cortex that had orientation selectivity. This was found through an experiment by giving a cat specific visual stimuli and measuring the corresponding excitation of the neurons in striate cortex (V1). The experimental set up was of a slide projector, a cat, electrodes, and an electrode monitor. They discovered this orientation selectivity when changing slides on the projector. The act of changing the slides produced a faint shadow line across the projector, and excited the neuron they were measuring. At the time of this experiment it was not conclusive that these orientation selective cells were in a "columnar" structure but the possibility of this structure was considered by research conducted by Vernon Mountcastle in 1956 about the topographic properties of the somatosensory system.

In 1974 Hubel and Wiesel wrote a paper about the geometry of orientation columns. They recorded 1410 cells in 45 penetrations into the striate cortex. Through this 1-dimensional technique they conceptualized that the orientation columns are not columns but slabs. In 1985, Gary Blasdel discovered a technique to visualize these orientation columns in 2D. His technique used photodiodes to detect optical changes in the visual cortex with the metabolic marker, 2-deoxyglucose, which labels active neurons. This confirmed Hubel and Wiesel's studies and also brought to light the swirls and pinwheel formations in the striate cortex.

Hubel and Wiesel received the Nobel Prize in Physiology and Medicine in 1981 for their contributions to the development of the visual system.

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