Figure 5.

Transitional behavioral graphs after prefrontal NE depletion in C57BL/6 (sham treated n=25; lesioned n=10) and β2^−/− mice (sham treated n=21; lesioned n=8). These graphs represent the probability of transition from an event to another (the thicker the arrow, the more probable the event). The symbols representing both mice and their respective postures are provided in Supplemental Table S2. Arrows represent the string of events: preceding event to succeeding event. The transition is computed for the first 4 min and the 4 last min of the experiment. Black arrows represent events that occur steadily (with the same probability with an overlap of 1 σ of their respective sd) for the first and the last 4 min. Red and green arrows represent events that occur only in the 4 first and the 4 last minutes, respectively. Transitional graphs showed an impoverishment of the social repertoire in C57BL/6 mice after NE prefrontal depletion, with less various behavioral events than in sham-treated mice. Temporal evolution of behavioral sequences, illustrated by the number of red and green arrows, by comparison with events linked by black arrows, was also drastically lower in C57BL/6 mice after NE prefrontal depletion. Therefore, C57BL/6 mice exhibited more rigid social behavior after NE prefrontal depletion. By contrast, in β2^−/− mice, NE PrL depletion favored a recovery of the temporal evolution of contact and follow events, thus reducing significantly rigid behaviors. Stop behaviors, which were significantly less frequent in β2^−/− mice than in C57BL/6 mice, were restored after NE lesion.