highly significantp < 10 −9
This increase in responsiveness with depth was highly significant ( R 2 = 0.70, p < 10 −9 , linear regression, n = 35 imaged regions in seven mice; Fig. 2 A ; Table 1 ) and was observed in every animal tested ( Fig. 2 A ; Table 1 ; R 2 > 0.79 and p < 0.04 for all animals, n = 5 regions per animal).