Figure 4. Correlation patterns can reveal whether switching is information-preserving vs. information-selecting.

a) Simultaneously recorded units in V1 show evidence of encoding both A and B stimuli across the population on every trial. Activity of individual units is color-coded according to whether the activity was more akin to the A-like (pink) or B-like (blue) distributions of spikes on a given trial. Only units with at least moderate evidence of mixture activity patterns are depicted; that this identification was successful can be seen by the presence of both A-like (pink) and B-like (blue) squares for every neuron across trials (rows). Notably, every trial also has both A-like and B-like responses across neurons (columns). Overall, there are more A-like than B-like responses, suggesting a possible bias in the representation. b-c) The pattern differs from those expected under covert attention (b), in which neurons might switch in synchrony between encoding one item vs. the other. This is shown here as a simulation involving the same A-like and B-like responses actually observed in (a), depicted as having occurred in a correlated fashion across neurons, or normalization (c), which would be expected to produce a common intermediate value across neurons and trials (purple).