Thanks for the links. "Assumptions: The observed data are from the same subject or from a matched subject and are drawn from a population with a normal distribution."
Let me go out on a limb and say that since all the females apparently had no observable change in deoxyhemoglobin at the nucleus accumbens, and all the males did, I don't believe there's a normal distribution here. The dimorphism coincides with a biphasic distribution.
I don't know those physiological terms. A sample of 32/ half men and half women is not necessarily normal. You could not tell because it is so small. Never heard of biphasic before. It is just very suspect to generalize and make an inference to an entire population from such a small sample. That is my point.