Representative spontaneous neuronal activity exhibited by (A) immature and (B) mature cortical cultures following the addition of the mAChR antagonist, atropine (1 μM) and recorded via MEA. (i) Spontaneous neuronal activity (100 s) recorded from a single channel. Left and right periods highlighted by an asterisk are expanded to show a long (ii) and short bursts (iii) respectively. (iv) Spontaneous neuronal activity (100 s) following atropine application where the period indicated by an asterisk is shown expanded in (v). (vi) Array-wide neuronal activity in control conditions and (vii) following addition of atropine. Atropine converted irregular firing in control conditions into synchronised burst firing for both mature and immature cultures.