In an update to the legendary Jose Delgado experiment (see video below), researchers Wim Vanduffel and John Arsenault (KU Leuven and Massachusetts General Hospital) changed a monkey’s preferences for an image by stimulating a part of the brain called the ventral tegmental area (VTA) with electrical pulses

The VTA is located in the midbrain and helps regulate learning and reinforcement in the brain’s reward system. It produces dopamine, a neurotransmitter that plays an important role in positive feelings, such as receiving a reward.

The study was published in the journal Current Biology.

“In one experiment, we allowed macaques to choose multiple times between two images,” Vanduffel said.  “This told us which of the two visual stimuli they tended to naturally prefer. In a second experiment, we stimulated the ventral tegmental area with mild electrical currents whenever they chose the initially nonpreferred image. This quickly changed their preference. We were also able to manipulate their altered preference back to the original favorite.”

This research has already been done in rodents, using electrical microstimulation and other very advanced technologies (e.g., optogenetics),” VanDuffel explained to KurzweilAI in an email interview. “However, we showed for the first time that by activating this structure in primates, it indeed leads to changes in choice behavior. It is still important to show this result in primates since the reward circuitry differs substantially between rodents and primates.

Therapeutic brain stimulation

“Defects in the ‘reward circuitry’ can lead to many psychiatric/neurological diseases including learning deficits, addiction, attention deficits, depression, schizophrenia, etc.,” VanDuffel added. “Being able to interfere with a malfunctioning circuit may lead to new therapies for these severe diseases.”

He noted that DBS is already being used (rarely) in the hospital for treatment of drug-resistant patients. “The main purpose of our study is ‘fundamental’ in nature: trying to understand the neuronal mechanisms that lead to the changes in behavior. This is key to develop novel and more specific therapies for patients where the reward circuitry is malfunctioning. We hope that our research may help to improve such therapies. Once you know the mechanisms, it is easier to develop accurate therapies with less side effects, etc.”

Surprisingly, the Dalai Lama would have no problem with that. “If it was possible to become free of negative emotions by a riskless implementation of an electrode — without impairing intelligence and the critical mind — I would be the first patient,” he reportedly said at the Society for Neuroscience Congress, Nov. 2005.

What do you think?

Jose Delgado and his Bull Story (starts at 1:15)

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Abstract of Current Biology paper

• Stimulation of ventral tegmental area (VTA) alters free-choice behavior in primates
• VTA-EM in primates reinforces cue selection in an operant conditioning paradigm
• Pavlovian cue-VTA-EM associations motivate future cue selection
• VTA-EM increases fMRI activity throughout the dopaminergic reward system

Monkey electrophysiology [1, 2] suggests that the activity of the ventral tegmental area (VTA) helps regulate reinforcement learning and motivated behavior, in part by broadcasting prediction error signals throughout the reward system. However, electrophysiological studies do not allow causal inferences regarding the activity of VTA neurons with respect to these processes because they require artificial manipulation of neuronal firing. Rodent studies fulfilled this requirement by demonstrating that electrical and optogenetic VTA stimulation can induce learning and modulate downstream structures [3–7]. Still, the primate dopamine system has diverged significantly from that of rodents, exhibiting greatly expanded and uniquely distributed cortical and subcortical innervation patterns [8]. Here, we bridge the gap between rodent perturbation studies and monkey electrophysiology using chronic electrical microstimulation of macaque VTA (VTA-EM). VTA-EM was found to reinforce cue selection in an operant task and to motivate future cue selection using a Pavlovian paradigm. Moreover, by combining VTA-EM with concurrent fMRI, we demonstrated that VTA-EM increased fMRI activity throughout most of the dopaminergic reward system. These results establish a causative role for primate VTA in regulating stimulus-specific reinforcement and motivation as well as in modulating activity throughout the reward system.