Fig. 2. Olfactory responses of Carassius auratus to changes in environmental [Na⁺], [Mg²⁺] and [K⁺]. (A) Typical electroencephalogram (EEG) recordings from the olfactory bulb (lower traces) and their integrated activity (upper traces) in response to 100 mmol l^-1 Na⁺ (in Na⁺-free AFW), 100 mmol l^-1 Mg²⁺ in AFW and 10 mmol l^-1 K⁺ in AFW (horizontal bars). All three recordings were taken from the same fish. (B) Semi-logarithmic plot of pooled, normalised (to the response to 10^-5 mol l^-1 L-serine in AFW) data of integrated EEG amplitude (means ± S.E.M.; N=5-6) in response to changes in [Ca²⁺] (filled circles), [Mg²⁺] (filled triangles), [Na⁺] (open circles) and [K⁺] (open triangles). Note that only the responses to Na⁺ approach the amplitude of those evoked by Ca²⁺, and then only at high concentrations.