Representative spontaneous neuronal activity recorded via MEA and exhibited by (A) mature and (B) immature cortical cultures following the blockade of all endogenous ACh effects by addition of atropine (1 μM) plus mecamylamine (10 μM; MEC). (i) Spontaneous neuronal activity (100 s) recorded in control conditions on a single channel where left and right asterisks indicate typical short and long bursts expanded in (ii) and (iii) respectively. (iv) Spontaneous neuronal activity (100 s) following atropine plus MEC application where left and right asterisks indicate typical short and long bursts expanded in (v). (vi) Array-wide spontaneous neuronal activity in control conditions and (vii) following addition of atropine plus MEC. Note the similarity between atropine plus MEC treatment and atropine treatment alone (Figure 6).