Letter to the Editor Psychother Psychosom Neuroimaging Evidence for Increased Neurite Density in Patients Taking Lithium: A Replication Study Samuel Sarrazin a, c, m Cyril Poupon c Ivy Uszynski c Achille Teillac c Jean-François Mangin c Mircea Polosan d Pauline Favre a, c Charles Laidi a–c, e, f Marc-Antoine D'Albis a–c, e, f Marion Leboyer a, b, e, f Pierre-Marie Lledo g Chantal Henry g–i Louise Emsell j Mohammed K. Shakeel k Vina M. Goghari l Josselin Houenou a–c, e, f a INSERM U955, IMRB, Team 15, “Translational Psychiatry”, Créteil, France; b Assistance Publique – Hôpitaux de Paris, DMU Impact, Department of Psychiatry, Mondor University Hospitals, Créteil, France; c NeuroSpin, Atomic Energy Commission, Gif-sur-Yvette, France; d Grenoble Institut des Neurosciences (GIN), INSERM U836, La Tronche, France; e Université Paris Est Créteil, Créteil, France; f Fondation FondaMental, Créteil, France; g Unité Perception et Mémoire, Institut Pasteur, Paris, France; h Pôle Hospitalo-Universitaire Paris 15ème, GHU, Centre Hospitalier Sainte Anne, Paris, France; i Université Paris Descartes, Paris, France; j Laboratory for Translational Neuropsychiatry, KU Leuven, Leuven, Belgium; k Hotchkiss Brain Institute, Department of Psychiatry, University of Calgary, Calgary, AB, Canada; l Graduate Department of Psychological Clinical Science, University of Toronto Scarborough, Toronto, ON, Canada; m Maison de Santé Pluridisciplinaire Pasteur, Chevilly Larue, France Received: January 30, 2020 Accepted: March 26, 2020 Published online: May 8, 2020 Dr. Samuel Sarrazin, MD Neuroimaging Platform Neurospin, UNIACT CEA Saclay, Bâtiment 145 FR–91190 Gif-sur-Yvette (France) sarrazinsamuel @gmail.com © 2020 S. Karger AG, Basel karger@karger.com www.karger.com/pps DOI: 10.1159/000507556 Dear Editor, The biological mechanisms underlying the efficacy of lithium therapy remain largely unknown. In Psychothera- py and Psychosomatics [1], we have recently published the first study showing increased neurite density in patients taking lithium with Neurite Orientation Dispersion and Density Imaging (NODDI), an advanced model of MRI diffusion [2]. Albeit confirming previous results associat- ing lithium with changes of grey matter volume [3], repli- cation remains a priority in the field of neuroscience [4]. Here, we report a replication of our previous results – higher neurite density within the left frontal cortex – in patients under lithium therapy compared with patients without lithium therapy, in a completely independent sample. Data were collected in Calgary (AB, Canada) from 23 controls and 26 patients with bipolar disorder upon which only 7 (26.9%) were prescribed with lithium at the time of scan. MRI data were acquired with a Gen- eral Electric MR750 3T device and included T1 structural MRI (MPRAGE, voxel size: 1 × 1 × 1 mm), and multi- shell, high angular resolution diffusion MRI (EPI, 96 × 96 × 60, voxel size: 2.5 × 2.5 × 2.5 mm), 98 gradient direc- tions, 3 b-shells: b = 300, 700, and 2,000 mm 2 /s (8, 30, and 60 directions, respectively) and 10 b = 0 mm 2 /s images (1, 3, and 6 per shell, respectively). Both the MRI manufac- turer and the diffusion weighted acquisition (number of directions, b values) were different from the original pub- lication [1]. The sole measure of interest was the mean intracellular fraction within the left frontal cortex as de- fined by the Desikan-Killiany atlas [1]. Downloaded by: University of Western Ontario 129.100.58.76 - 5/11/2020 12:13:31 PM