Fig. 7: Experimental data confirm the antagonism between sparseness and stereotypy.

a A representative intracellular recording (gray) from locust bLN1 is shown to illustrate the method of removing spikes that occur at depolarizations below a threshold (dashed line). Discarded spikes are labeled ‘−’ and retained spikes are labeled ‘+’. The depolarization (dark black trace) is extracted by clipping spikes and filtering the recording (50-Hz low-pass). The threshold is set at one s.d. above the mean depolarization. b Stereotypy in locust bLN1 response reduces when we mimic more sparseness by removing spikes below the threshold (1 s.d. above mean depolarization). c Stereotypy continues to reduce as sparseness is further increased by raising the threshold in multiples of s.d. above mean depolarization. In b, c, n = 225 values (15 pairs of odors × 15 pairs of individuals). d Fly KC populations imaged at different lobes of the mushroom body in control flies reveal significant stereotypy. The stereotypy further increases in all lobes as sparseness is reduced by blocking APL output (APL>TNT); n = 315 (control, α- and α′-lobes, from 11 hemispheres from 10 flies), n = 570 (APL>TNT, α- and α′-lobes, from 20 hemispheres from 14 flies), n = 828 (control, β-, β′- and γ-lobes, from 18 hemispheres from 15 flies), n = 1890 (APL>TNT, β-, β′- and γ-lobes, from 36 hemispheres from 24 flies). Error bars represent s.e.m.