Vector value in the human nervous system

I have argued that utility/value should be a vector quantity.  (My post of 19 Feb. 2011, my website,
http://www.robert-w-jones.com/, philosopher, axiology, and references therein) Schultz (J. of Neurophysiology, 80: 1-27, 1998) notes that the responses of most dopaminergic neurons are similar, suggesting that this system carries a scalar signal.  Schultz and Romo, however, (J. of Neurophysiology, 63: 607-624, 1990)
report that different goups of neurons display both excitatory and inhibitory responses to the very same situation.  This would suggest vector reward signaling. (see the 2003 PhD thesis of Nathaniel Daw, Carnegie Mellon school of computer science)