Can't get motivated? A brain circuit may explain why and can be turned off

A study in Cell Reports reports that suppressing a ventral striatum→ventral pallidum pathway in macaque monkeys reduced hesitation to begin tasks that might include unpleasant outcomes, without changing how rewards and punishments were weighed. The circuit is described as acting like a 'motivation brake' and researchers note possible relevance to motivation problems in conditions such as depression and schizophrenia.

Researchers report a neural pathway that can dampen the drive to start a task and show a way to suppress it in macaque monkeys. The study, published in Cell Reports, identifies a connection from the ventral striatum to the ventral pallidum that the authors describe as a "motivation brake." The team trained two male macaque monkeys on decision tasks that measured whether the animals would initiate an action when rewards were paired with a possible unpleasant outcome. When signaling along that pathway was selectively suppressed, the animals were more willing to begin trials that carried the chance of an unpleasant stimulus. Key findings: - The study used a targeted genetic technique to suppress signaling from the ventral striatum to the ventral pallidum in two male macaque monkeys. - Monkeys were trained on two decision tasks: one that yielded only a water reward and one in which the reward could be paired with an unpleasant puff of air; initiating a trial required steady gaze fixation. - Suppressing the pathway had little effect on reward-only trials but made the animals more willing to start trials when a potential unpleasant outcome was present. - The intervention did not change how the animals weighed reward versus punishment; it affected initiation rather than value comparison. - Electrophysiological recordings and behavior suggest the ventral striatum detects aversive conditions and suppresses ventral pallidum activity, producing the observed reduction in action initiation. - The authors and invited commentators note the possible relevance to motivational deficits in disorders such as major depressive disorder and schizophrenia and mention potential future approaches such as targeted brain stimulation, while also emphasizing the need for balance. Summary: The study identifies a specific circuit that appears to reduce the likelihood of starting an action when unpleasant outcomes are possible and shows that selectively dampening that pathway increased initiation in macaque monkeys. If confirmed in humans, researchers say this could influence how clinicians think about difficulties initiating tasks in some psychiatric conditions; translation to human treatments and safety considerations remain to be determined.