Biomedical Engineering Reference
In-Depth Information
Figure 6
. Nonparametric statistical maps in pseudocolor (with
p
-value coding bar), showing functional mag-
netic resonance imaging "activation," are juxtaposed on structural images (figure adapted with permission
from Breiter et al. (37)). Activation represents brain signal related to blood flow and volume changes that are
linked to changes in neural local field potentials. Images on the left show significant signal change in the
nucleus accumbens/subcallosal cortex (NAc/SCC) and sublenticular extended amygdala (SLEA) to infusion
of cocaine and not saline. These images are brain slices in the same orientation as the human face, and are 12
mm (NAc/SCC) and 0 mm (SLEA) anterior to a brain landmark, the anterior commissure. Signal time courses
from the NAc/SCC and SLEA are graphed in the middle of the figure as percent signal change during the
cocaine pre- and post-infusion intervals (infusion onset shown with a blue line). These signals were correlated
with the average behavioral ratings for rush (euphoria and physiological experience of initial cocaine effects)
and craving (motivational drive to obtain more cocaine) shown in a graph at the bottom of the figure. The
statistical correlations of the behavioral ratings with the brain signal responses to cocaine are shown as statis-
tical maps on the right of the figure.
study (37), multiple projection fields of the VT dopamine neurons were specifi-
cally targeted and visualized (Figure 6). As the study involved chronic cocaine-
dependent subjects, the results correlating subjective reports of euphoria and
craving (i.e., a mono-focused motivational state) to activation in reward circuitry,
could not be separated from neuro-adaptations to subject drug abuse. A number
of follow-up studies in healthy controls confirmed the initial findings with
cocaine, using monetary reward, social reward in the form of beautiful faces,
and thermal aversive stimuli. Together, this series of studies provided strong
evidence for a generalized circuitry that processes stimuli with motivational
salience (3,19,31,37,38). Modeling a game of chance, the monetary reward
study incorporated principles from Kahneman and Tversky's prospect
