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REFERENCES1. Christopoulos A, Changeux JP, Catterall WA, Fabbro D, Burris TP, Cidlowski JA, et al. International Union of Basic and Clinical Pharmacology. XC. Multisite pharmacology: recommendations for the nomenclature of receptor allosterism and allosteric ligands. Pharmacol Rev. 2014;66:918-47. 2. Huidobro-Toro JP, Valenzuela CF, Harris RA. Modulation of GABA A receptor function by G protein-coupled 5-HT 2C receptors. Neuropharmacology. 1996;35:1355-63. 3. Im WB, Chio CL, Alberts GL, Dinh DM. Positive-allosteric modulator of the human 5-HT 2C receptor. Mol Pharmacol. 2003;64:78-84. 4. Ding C, Bremer NM, Smith TD, Seitz PK, Anastasio NC, Cunningham KA, et al. Exploration of synthetic approaches and pharmacological evaluation of PNU-69176E and its stereoisomer as 5-HT 2C receptor allosteric modulators. ACS Chem Neurosci. 2012;3:538-45. 5. Wild CT, Miszkiel JM, Wold EA, Soto CA, Ding C, Hartley RM, et al. Design, synthesis, and characterization of 4-undecylpiperidine-2-carboxamides as positive-allosteric modulators of the serotonin (5-HT) 5-HT 2C receptor. J Med Chem. 2018 https://doi. org/10.1021/acs.jmedchem.8b00401 6. Garcia-Carceles J, Decara JM, Vazquez-Villa H, Rodriguez R, Codesido E, Cruces J, et al. A positive-allosteric modulator of the serotonin 5-HT 2C receptor for obesity. J Med Chem. 2017;60:9575-84.Measuring movement has been a cornerstone of studying behavior in animals in controlled studies. Movement data have served as a primary window into behavior, and by proxy, social function, mood, and cognition [1]. In humans, variations in locomotor activity have served as markers of a range of psychiatric syndromes including major depression, bipolar disorder, anxiety, catatonia, and substance use disorders [2]. Reports of sensor-based motion measurement in humans date back to the 1950s [2], and motion-based models of human psychopathology have been key to developing animal models of psychopathology [1]. A vast literature has documented how these animal models have facilitated development of motion-based signatures of antidepressant, anxiolytic, and other drug effects and guided drug development [3]. However, the limitations of technology thus far have meant that motion-mapping in humans has remained largely restricted to experimental settings.Phenotyping of naturalistic human behavior continues to depend on self-report or observer-report measures, with sampling often at intervals of hours to days. Newer technologies, supported by advances in wireless connectivity, more compact and reliable sensors and devices, and higher computing power can now sample movement at intervals of seconds, and can facilitate measurement of human motion in the natural living environment in ways previously not possible [4]. Such technologies are setting the stage for movement to become a major new phenotypic biomarker in neuropsychiatry.A wide array of validated technologies can quantify moti...