Disturbance of approach-avoidance behaviors in non-human primates by stimulation of the limbic territories of basal ganglia and anterior insula.

The basal ganglia (BG) are involved in motivation and goal-directed behavior. Recent studies suggest that limbic territories of BG not only support reward seeking (appetitive approach) but also the encoding of aversive conditioned stimuli (CS) and the production of aversive-related behaviors (avoidance or escape). This study aimed to identify inside two BG nuclei, the striatum and pallidum, the territories involved in aversive behaviors and to compare the effects of stimulating these territories to those resulting from stimulation of the anterior Insula (aIns), a region that is well-known to be involved in aversive encoding and associated behaviors. Two monkeys performed an approach/avoidance task in which they had to choose a behavior (approach or avoidance) in an appetitive (reward) or aversive (air-puff) context. During this task, either one (single-cue) or two (dual-cue) CS provided essential information about which context-adapted behavior should be selected. Microstimulation was applied during the CS presentation. Stimulation generally reduced approaches in the appetitive contexts and increased escape behaviors (premature responses) and/or passive avoidance (noninitiated action) in aversive context. These effects were more pronounced in ventral parts of all examined structures, with significant differences observed between stimulated structures. Thresholds to induce effects were lowest in the pallidum. Striatal stimulation led to the largest diversity of effects, with a subregion even leading to enhanced active avoidance. Finally, aIns stimulations produced stronger effects in the dual-cue context. These results provide causal evidence that limbic territories of BG, like aIns, play crucial roles in the selection of context-motivated behaviors.