Mind Control: Influencing Choice
Ever change your mind? Well now scientists can do it for you, at least that is the latest by researchers from Massachusetts General Hospital (MGH) and the University of Leuven in Belgium. By artificially stimulating a brain region believed to play a key role in learning, reward and motivation they were able to induce monkeys to change which of two images they would choose to look at.
“Previous studies had correlated increased activity in the primate VTA with positive events experienced by the animal but could not prove that VTA activity actually caused behavioral changes,” says Wim Vanduffel, PhD. “Studies in rodents have shown that artificially manipulating VTA activity strongly influences behavior, and our work has bridged the gap between rodent and primate.”
Researchers used high-resolution MRI machines to guide the placement of microelectrodes within the VTAs of macaque monkeys. In the initial set of experiments, the animals were presented with a pair of images — like a star and a ball — and could freely chose to look at one image or the other [with their choice measured by their eye movement]. Each animal was trained by means of a juice reward to look first at a white square at the center of the visual field and then at either of the paired images.
When the researchers established each animal’s preference [based on which image was looked at most frequently], a mild stimulation was applied to the VTA when the animal happened to look at the nonpreferred image — remember they were trained to not like that image by a reward for looking at the other image.
After the simulation the animal’s preference changed, and it would frequently look at what had been originally the less favored image. Conversely when the VTA stimulation was applied to the originally preferred image, the monkeys would change their preference back to the original choice.
[Loony Hint: I know this is confusing, basically the researchers trained the monkeys to look at a particular image — by giving them a treat. when the VTA is stimulated, despite the training, the monkeys would look at the other image. They would return to looking at the trained image when it was stimulated once more.
Keep in mind they were looking at the image when they stimulated the VTA, so because they stimulated it while they were looking at a particular image the monkeys would prefer that image regardless of getting a treat or not.]
To further test this, the researchers showed the monkeys a 2o minute video with both images appearing in a random order every 5 seconds. During the video, they stimulated the VTA every time the non-prefered image would appear. Then after the video, they did the image viewing test again and the monkeys would, once again prefer the non-prefered image.
Functional MR imaging taken while the animals received either a juice reward or VTA stimulation revealed that both induced activation of brain regions that previous studies in humans and other primates have associated with reward signaling by means of the neurotransmitter dopamine. Furthermore, the level of VTA stimulation required to activate these structures was considerably less than the amount required to reinforce or change behavior in the earlier experiments.
“Our study showed that the timing of VTA stimulation is important – when stimulation happens immediately after an action is performed, the monkey is more likely to perform that action – and that it applies ‘value’ to a particular stimulus and motivates future behavior,” says Vanduffel. “Our findings lay the groundwork for further investigation of the role of the VTA in reinforcing and regulating motivated behavior.”
So the bottom line? The next time you want something, I would make sure that someone didn’t just make you think that way. Do you want something a little more scientific [are you sure]? You probably want the full study — here!
Arsenault, J., Rima, S., Stemmann, H., & Vanduffel, W. (2014). Role of the Primate Ventral Tegmental Area in Reinforcement and Motivation Current Biology DOI: 10.1016/j.cub.2014.04.044