Figure 11.

Behavior of the circuit with local dendritic recurrent inhibition. A, The ranges of the excitation and inhibition. The red line indicates the presumed range of the feedforward and the recurrent excitation. The four blue lines indicate the presumed ranges of the dendritically mediated local recurrent inhibition: three, two, or 1.5 times wider than (a–c), or the same range as (d), the excitation, respectively. Ba, Bb, Circuit behavior when the local dendritic recurrent inhibition was three (Ba) or two (Bb) times wider than the excitation (corresponding to the blue lines a and b in A), respectively. The configurations are the same as in Figure 10C: the black and white crosses indicate <0.95 (but >0.9) and <0.9 accuracy, respectively; in addition, the white diamonds indicate the conditions in which the formation of multiple bumps was observed. When the dendritic inhibition was not very narrow (Ba), contrast-dependent intensity-insensitive accurate memory formation occurred at an appropriate inhibition strength (26). When the inhibition was made further narrower (Bb), however, multiple bumps were more easily formed and the contrast-dependent intensity-insensitive accurate memory formation could no longer occur. C, An example trial in which two activity bumps were formed and sustained.