Methods and Results
This study used intracerebral microdialysis to measure the norepinephrine outflow and depletion in response to both conditioned and unconditional stimuli in order to determine whether or not there is any chemical selectivity in the attribution of motivational salience to unconditioned stimuli. With regard to conditioned stimuli, the norepinephrine output corresponded to salience but the depletion of the chemical transmission was not affected by salience. This was was different when considering unconditioned stimuli, where they found that if the new stimulus was particularly intense and induced a sustained chemical outflow then the attributed salience was selective.
Study Participants and Factors
This study was performed on mice using chocolate consumption and forced isolation as stimulus for the norepinephric gauge of stimulus. White chocolate and milk chocolate were used as positive stimulus. Isolation with varying light exposure and food restriction was the adverse stimulus.
So, What Does this Mean
Exposure to new, highly salient stimuli increased norepinephrine output regardless of whether it was good or bad stimuli. Following exposure to a highly salient negative situation, previously mild stimulus triggered a norepinephric output on par with the highly salient. The results of this study point to norepinephric output as necessary for the place-conditioning process. Or in the words of the researchers:
“Thus, these results confirm our hypothesis and demonstrate that prefrontal cortical NE transmission is necessary for the acquisition of conditioned properties to stimuli paired with highly salient natural rewarding or aversive events in a place-conditioning procedure.”
Link to the Study