An in vitro method for obtaining a corticospinal upper motor neuron from a neural stem cell, wherein said method comprises contacting a neural stem cell under conditions adequate for increasing the signal mediated by the CB 1 cannabinoid receptor in said cell and under conditions to promote dorsalization of said cell and wherein conditions adequate for increasing the signal mediated by the CB 1 cannabinoid receptor involve an increase in the number of Ctip2+ Satb2- cells with respect to the basal levels of at least 5% and involve: (i) contacting said neural stem cell with a CB 1 cannabinoid receptor agonist selected from the group consisting of anandamide, 2-arachidonoylglycerol (2-AG), N-arachidonoyl dopamine, arachidonyl-2'-chloroethylamide (ACEA), HU-210, JWH-073, WIN 55,212-2, cannabinol, tetrahydrocannabinol, 11-hydroxy-Δ 9 -tetrahydrocannabinol (11-OH-THC), levonantradol, dronabinol, AM-2201 (1-(5-fluoropentyl)-3-(1-naphthoyl)indole), JWH-018 (1-pentyl-3-(1-naphthoyl)indole), AM-678, 2-arachidonyl glyceryl ether (2-AGE, noladin ether), palmitoylethanolamide and CP 55,940; and/or (ii) introducing in said neural stem cell an expression vector encoding the CB 1 cannabinoid receptor to increase the expression of the CB 1 cannabinoid receptor above basal levels, and/or (iii) introducing in said neural stem cell an expression vector encoding an endocannabinoid-synthesizing enzyme to increase in the cell the activity of an endocannabinoid-synthesizing enzyme above basal levels, and/or (iv) introducing in said neural stem cell an agent which silences an endocannabinoid-degrading enzyme selected from the group consisting of a shRNA, a siRNA, an antisense nucleic acid and a ribozyme and/or contacting said neural stem cell with an inhibitor of said endocannabinoid-degrading enzyme, and wherein conditions to promote dorsalization of said cell involve contacting said neural stem cell with a dorsalizing agent selected from: a) a sonic hedgehog inhibitor selected from the group consisting of adenosine 3',5'-cyclic monophosphate, N6,O2'-dibutyryl- sodium salt, AY 9944, KAAD-cyclopamine, cyclopamine, forskolin, GANT58, GANT61, JK184, HPI-1, HPI-3, jervine, SANT-1, GDC-0449, robotnikinin and IPI-926; and b) a Smad inhibitor selected from the group consisting of Noggin, Dorsomorphin, SB431542, LDN-193189, Lefty, Activin, TGF-beta and combinations thereof. (i) contacting said neural stem cell with a CB 1 cannabinoid receptor agonist selected from the group consisting of anandamide, 2-arachidonoylglycerol (2-AG), N-arachidonoyl dopamine, arachidonyl-2'-chloroethylamide (ACEA), HU-210, JWH-073, WIN 55,212-2, cannabinol, tetrahydrocannabinol, 11-hydroxy-Δ 9 -tetrahydrocannabinol (11-OH-THC), levonantradol, dronabinol, AM-2201 (1-(5-fluoropentyl)-3-(1-naphthoyl)indole), JWH-018 (1-pentyl-3-(1-naphthoyl)indole), AM-678, 2-arachidonyl glyceryl ether (2-AGE, noladin ether), palmitoylethanolamide and CP 55,940; and/or (ii) introducing in said neural stem cell an expression vector encoding the CB 1 cannabinoid receptor to increase the expression of the CB 1 cannabinoid receptor above basal levels, and/or (iii) introducing in said neural stem cell an expression vector encoding an endocannabinoid-synthesizing enzyme to increase in the cell the activity of an endocannabinoid-synthesizing enzyme above basal levels, and/or (iv) introducing in said neural stem cell an agent which silences an endocannabinoid-degrading enzyme selected from the group consisting of a shRNA, a siRNA, an antisense nucleic acid and a ribozyme and/or contacting said neural stem cell with an inhibitor of said endocannabinoid-degrading enzyme, a) a sonic hedgehog inhibitor selected from the group consisting of adenosine 3',5'-cyclic monophosphate, N6,O2'-dibutyryl- sodium salt, AY 9944, KAAD-cyclopamine, cyclopamine, forskolin, GANT58, GANT61, JK184, HPI-1, HPI-3, jervine, SANT-1, GDC-0449, robotnikinin and IPI-926; and b) a Smad inhibitor selected from the group consisting of Noggin, Dorsomorphin, SB431542, LDN-193189, Lefty, Activin, TGF-beta and combinations thereof.