Fig. 1. Olfactory responses of Carassius auratus to changes in environmental [Ca²⁺]. (A) Typical electroencephalogram (EEG) recordings from the olfactory bulb (lower traces) and their integrated activity (upper traces) in response to increases in [Ca²⁺] from nominally zero (Ca²⁺-free AFW) to 0.1, 1.0 and 10 mmol l^-1 (horizontal bars). All three recordings were taken from the same fish. (B) Semi-logarithmic plot of mean values (normalised data, see Materials and Methods for details; N=6) showing the concentration dependence of this effect (r²=0.98), and a Hill plot fitted to the data giving an apparent EC₅₀ of 0.6 mmol l^-1 [Ca²⁺] and a Hill coefficient of 0.8. The environmental range of [Ca²⁺] normally encountered by Carassius auratus and the plasma free [Ca²⁺] are also shown.