Emotional words evoke region- and valence-specific patterns of concurrent neuromodulator release in human thalamus and cortex

Words represent a uniquely human information channel– humans use words to express thoughts and feelings, and to assign emotional valence to experience. Work from model organisms suggests that valence assignments are carried in part by the neuromodulators dopamine, serotonin, and norepinephrine. Here, we ask whether valence signaling by these neuromodulators extends to word semantics in humans by measuring sub-second neuromodulator dynamics in N = 19 individuals evaluating positive, negative, and neutrally valenced words. Results from thalamus show that dopamine and serotonin carry information about word valence but with opposite polarity. Results from the anterior cingulate cortex show that dopamine carries word valence-related information in a strong hemisphere-dependent fashion. Overall, these experiments provide the first direct evidence that neuromodulator-dependent valence signaling extends to word semantics in humans and that these signals exhibit a substantial degree of regional specificity.