Video https://youtu.be/HBsku5G_SDM

In this whiteboard episode, we revisit the basal ganglia's simultaneous "go" and "no-go" pathways, dissecting how excitatory cortical inputs converge on the dorsal striatum's medium spiny neurons, with dopamine from the substantia nigra pars compacta amplifying reward/value while relays (globus pallidus externa/subthalamic nucleus) and outputs (globus pallidus interna/reticulata) fine-tune thalamic drive for action or suppression. Using OCD as an extreme case, we illustrate how enlarged synaptic spines and morphology from repetitive firing hijack the cortico-striato-thalamic loop, prioritizing compulsive habits over flexibility—revealing the circuit's indifference to judgment, driven ...