Figure 3.

Distribution of acquired responses to the different CS types. A responsive neuron is tested for its firing rate following CS-onset but before the US-onset, compared with pre-CS activity, but importantly, after normalization to CS-evoked responses during habituation (see Materials and Methods). Hence, a responsive neuron is one that changed its activity following conditioning. A, Numbers of neurons per each CS (circle sizes are proportional): response to CS+ (red), CS− SM (green), CS− OM (blue). No significant difference was found (see Results, Proportion and sign of neural responses homogenously distribute across CS types). B, Same as in A but separately for neurons that increased (left) or decreased (right) their FR following CS onset. C, Dividing increases and decreases in FR for the neurons that acquired responses to each CS type. D, Distributions of exclusive acquired responses to each CS type. E, Directionality of responses divided by CS type: neurons that increase their FR to both CS+ and CS, decrease to both, or in opposite directions. The take-home-message from these detailed careful categorizations is that there were little (nonsignificant) differences in proportions of acquired responses, and BLA neurons acquired increases and decreases in their FR to both CS+ and CS−. Hence, homogenous encoding is observed in the amygdala.