Slide 20

Summary diagram illustrating that feedback inhibition is proportional to feedback excitatio in cortical networks. The anatomical arrangement of the cortex is such that pyramidal cells give rise to large recurrent connections to other pyramidal cells, resulting in a strong feedback excitation. However, interposed between this feedback excitation are inhibitory interneurons. The degree of activation of inhibitory interneurons is directly proportional to the feedback excitation. Neurons also have intrinsic inhibitory mechanisms (such as K+ currents) that act to keep network activity under control.