Indeed, the circuit involving the Hb plays a pivotal and conserved function in the control of dopaminergic and serotonergic systems among vertebrates [35], [42], and genetic inhibition of the asymmetric circuit that primarily involves the left Hb and dIPN in zebrafish leads to a defective enhancement of fear responses and anxiety [43], [44] while the complementary circuit involving the right Hb and vIPN is proposed to play an opposite regulatory role in these behaviours [45]. The gene discussed is GSTM1; the disease is Anxiety.