Uncovering the Neural Circuitry behind Motivation
Discoveries Offer the Possibility of Making Better Choices
At the point before we actually do something, whether that be caring for our children, exercising, or abusing drugs or alcohol, there is the motivation to do so. But what guides that motivation? In her research on rats, neuroscientist Joan Morrell was the first to uncover that subregions of the brain's prefrontal cortex are involved in both the caregiving of offspring and the motivation to parent. These are the areas of the brain responsible for executive function or our ability to make decisions, to choose between conflicting thoughts and determine the consequences of our actions.
“If you have too little activity in the prefrontal cortex, it can lead to a host of problems, such as drug and alcohol abuse, gambling addiction, poor decision making, or other imprudent choices, and a limited ability to plan and project,” says Morrell. “Up until now, neuroscientists thought parental behavior was an activity regulated largely by the core of the brain, but what we have found is that subregions of the prefrontal cortex are significant for both caregiving and the motivation to parent.”
In related research, Morrell and her team also are seeking a better understanding of the motivation to exercise by studying rats and their exuberant voluntary wheel-running behavior. She is exploring the brain regions that provide the motivation to engage in this form of exercise. Given the wide-ranging positive effects on physical and mental health that are documented in humans, and the substantial barrier that exists for many in the motivation to exercise, Morrell believes this is crucial area to extend her exploration of the brain regions mediating motivation.
By unlocking the keys to motivation, it then may become possible to mold it so the results are more beneficial behaviors.
“Our research suggests that there may be things we can do to strengthen parental behavior, and also perhaps the desire to exercise, in a manner similar to the way people can be trained if they have gambling addictions to make prudent choices,” says Morrell.
Morrell describes one key component of motivation as “seeking out.” She explains, “It is that point when you wake up in the morning and realize you are out of coffee. You will rearrange your entire morning schedule to go out and get that coffee.” It is that “seeking out” component of motivation that really starts any motivated behavioral sequence. It is this behavioral initiation, this manifestation of motivation that is her research focus.
In their research on maternal behavior, Morrell and her lab have examined the motivating forces that lead female rats to seek parenting their pups over seeking cocaine. First the maternal rats were trained to learn what compartment of an apparatus contained their pups and which one contained cocaine. What the research found was that most postpartum females seek their pups in the early stages of postpartum, while later in the postpartum period most seek cocaine. Also when the function of certain subregions of the prefrontal cortex were impeded, the rats' motivation to seek their pups was reduced, and the motivation to seek cocaine was enhanced.
What they also uncovered is that the neural circuitry in the subregions of the prefrontal cortex regulating the motivation to choose either the pups or cocaine are at least partially separable, suggesting that this may be how the fundamental wiring of the prefrontal cortex mediates its decision making, or choice. Further, the prefrontal and core brain neural circuitry that mediate pup-caregiving and the motivation to parent overlap suggesting great functional cohesion, which may ensure that parenting is a highly dependable behavioral outcome among mammals, including humans.
It's long been known that the medial preoptic region at the center of the brain plays a central role in maternal care-giving behavior. What Morrell's research has shown, however, is that subregions of the prefrontal cortex appear to be the driving force that motivates the choosing of that behavior, even in the presence of other significant stimuli, like cocaine.
Joan Morrell earned her PhD in anatomy from the University of Rochester School of Medicine and Dentistry. She then moved to Rockefeller University where she spent 12 years rising through the academic ranks from postdoctoral fellow to associate professor. She joined the faculty of Rutgers in Newark in 1986. She has published 117 peer reviewed journal articles, reviews and book chapters. In her lab, she has trained 15 graduate students to the PhD level and 12 postdoctoral fellows. She has done extensive service as a member of the National Institutes of Health Peer Review system, served as Behavioral Neuroscience Section editor for Neuroscience and also on a number of other journal editorial boards. Her research is supported by grants from the National Institute of Child Health and Human Development, the National Institute on Drug Abuse, the March of Dimes, NARSAD and the Busch Biomedical Fund.
- Behavioral differences between late preweanling and adult female Sprague-Dawley rat exploration of animate and inanimate stimuli and food, Behavioral Brain Research, March 1, 2011.
- Effect of the adenosine A2A receptor antagonist MSX-3 on motivational disruptions of maternal behavior induced by dopamine antagonism in the early postpartum rat, Psychopharmacology, January 2011.
- The medial preoptic area is necessary for motivated choice of pup- over cocaine-associated environments by early postpartum rats, Neuroscience, May 5, 2010.
- Transient inactivation of the ventral tegmental area selectively disrupts the expression of conditioned place preference for pup- but not cocaine-paired contexts, Behavioral Neuroscience, December 2009.
- The changing role of the medial preoptic area in the regulation of maternal behavior across the postpartum period: facilitation followed by inhibition, Behavioral Brain Research, December 14, 2009.
- Exposure to pups influences the strength of maternal motivation in virgin female rats, Physiology & Behavior, November 28, 2008.