Representative spontaneous neuronal activity exhibited by (A) immature and (B) mature cortical cultures following application of the nAChR antagonist, mecamylamine (10 μM; MEC). (i) Spontaneous neuronal activity (100 s) on a single channel where left and right asterisks indicate typical short and long bursts that are expanded in (ii) and (iii) respectively. (iv) Spontaneous activity (100 s) following mecamylamine application where the period indicated by an asterisk is shown expanded in (v). (vi) Array-wide neuronal activity in control conditions and (vii) following mecamylamine application. Note the limited effect of nAChR blockade (c.f. mAChR blockade; Figures 6 &7) such that only burst duration was significantly affected by mecamylamine (Figure 4).