  Contrary to the intense debate about brain oxygen dynamics and its uncoupling
in mammals, very little is known in birds. In zebra finches, picosecond optical
tomography (POT) with a white laser and a streak camera can measure in vivo
oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb) concentration changes following
physiological stimulation (familiar calls and songs). POT demonstrated
sufficient sub-micromolar sensitivity to resolve the fast changes in
hippocampus and auditory forebrain areas with 250 \mu m resolution. The
time-course is composed of (i) an early 2s-long event with a significant
decrease in Hb and HbO2, respectively -0.7 \mu Moles/L and -0.9 \mu Moles/L
(ii) a subsequent increase in blood oxygen availability with a plateau of HbO2
(+0.3 \mu Moles/L) and (iii) pronounced vasodilatation events immediately
following the end of the stimulus. One of the findings of our work is the
direct link between the blood oxygen level-dependent (BOLD) signals previously
published in birds and our results. Furthermore, the early vasoconstriction
event and post-stimulus ringing seem to be more pronounced in birds than in
mammals. These results in bird, a tachymetabolic vertebrate with a long
lifespan, can potentially yield new insights for example in brain aging.
