Figure 4.

Recurrent excitatory connectivity. (a) Connectivity within the cortical circuit is primarily like to like, with preferential (though not exclusive) connections between neurons tuned to similar orientations. This applies to both feedforward connectivity from L4 to L2/3 and recurrent connectivity within L2/3. Panel a adapted from Ko et al. (2011), Lee et al. (2016), Lien & Scanziani (2013), Morgenstern et al. (2016), Rossi et al. (2020), Wertz et al. (2015), and Yoshimura et al. (2005). (b) The spatial organization of connectivity is coaxial, whereby a neuron (red) tends to receive input from neurons (green) with similar orientation preference and whose location, in retinotopic coordinates, is along the axis of their preferred orientation. Panel b adapted from Iacaruso et al. (2017) and Rossi et al. (2020). (c) Recurrent cortical excitation is larger than incoming thalamic excitation but is matched in tuning, resulting in cortical amplification (total excitation). Panel c adapted from Li et al. (2013) and Lien & Scanziani (2013, 2018). Abbreviations: dLGN, dorsal lateral geniculate nucleus; L, layer.