On the functional level, however, there are indeed reasons to believe CHIR-99021 concentration that diverse cortical areas share common computational mechanisms. First, the normalization framework, which is a prominent feature of the V1 computation, is not limited to V1 but appears in many parts of the sensory system (Carandini and Heeger, 2012). Even high-level processes such as response modulation related to attention or behavioral state

can be described as a normalization-like shift in gain (Reynolds and Heeger, 2009). Second, the feature selectivity for excitation and inhibition are often matched in other cortical areas as they are in V1. Third, the neuronal mechanisms underlying V1 feature selectivity are not limited to neurons in V1. Threshold, AZD8055 purchase response variability, driving-force nonlinearities, response saturation, low-pass filtering, response diversity, and synaptic depression are mechanisms inherent to all neurons that support action potentials. Whether neurons in other areas of the cortex take advantage of them, and, if so, whether they use them in ways analogous to V1, is an open question. This work was supported by NIH grants R01 EY04726 (D.F.) and R01 EY019288 (N.J.P.) and by a grant from the Pew Charitable

Trusts (N.J.P.). “
“It is useful to approach the topic of synaptic connections in the cortex by considering three distinct types of specificity: topographic specificity (where you

are), cell-type specificity (who you are), whatever and functional specificity (what you do; Lee and Reid, 2011). Recent technical advances have accelerated progress in understanding cell-type and, to a lesser extent, functional specificity, but it is useful to begin with the better understood topic of cortical topography, or functional architecture. Building upon the revolutionary findings of Vernon Mountcastle, who in 1957 proposed that narrow vertical columns of neurons are the fundamental unit in cortical processing (Mountcastle, 1957), Hubel and Wiesel introduced the term “functional architecture” to describe the relationship between anatomy and physiology in cortical circuits. A common textbook description of functional architecture is that receptive fields in a cortical column are all extremely similar. Instead, Hubel and Wiesel gave a more nuanced treatment of functional architecture in the visual cortex. They proposed that a cortical column can be very homogeneous for some receptive-field attributes, loosely organized for others, and even completely disorganized in yet other respects. One aspect of functional architecture in the cat visual cortex, the orientation column, is indeed monolithic. As Hubel and Wiesel (1962) wrote, “It can be concluded that the striate cortex is divided into discrete regions within which the cells have a common receptive-field axis orientation.