Role of the 5-HT
Distortions of self-experience are critical symptoms of psychiatric disorders and have detrimental effects on social interactions. In light of the immense need for improved and targeted interventions for social impairments, it is important to better understand the neurochemical substrates of social interaction abilities. We therefore investigated the pharmacological and neural correlates of self- and other-initiated social interaction. In a double-blind, randomized, counterbalanced, crossover study 24 healthy human participants (18 males and 6 females) received either (1) placebo placebo, (2) placebo lysergic acid diethylamide (LSD 100 μg, p.o.), or (3) ketanserin (40 mg, p.o.) LSD (100 μg, p.o.) on three different occasions. Participants took part in an interactive task using eye-tracking and functional magnetic resonance imaging completing trials of self- and other-initiated joint and non-joint attention. Results demonstrate first, that LSD reduced activity in brain areas important for self-processing, but also social cognition second, that change in brain activity was linked to subjective experience and third, that LSD decreased the efficiency of establishing joint attention. Furthermore, LSD-induced effects were blocked by the serotonin 2A receptor (5-HT