Fig. 8.

Lip stimulation alone is insufficient for memory formation. l-NAME-treated (n = 8) and seawater-treated (n = 7) animals were trained with inedible food. Each trained animal was yoked to an animal whose lips were stimulated (for l-NAME-treated, n = 8; for seawater-treated, n = 7) for a period equivalent to that of the training. Twenty-four hours later, both the trained and the yoked animals were tested with inedible netted food that entered the mouth and produced failed swallows. For animals treated with seawater, significant differences were observed between the animals that had been trained with food entering the mouth and those in which the lips were stimulated for both the time to stop responding to food (p < 0.001;t₍₁₃₎ = 5.68) and the time that food was in the mouth during the first 5 min of the test (p < 0.01;t₍₁₃₎ = 3.10; 2-tailed ttests). However, for animals treated with l-NAME, no significant differences were observed between the trained animals and the yoked controls (for the time to stop, p = 0.22,t₍₁₅₎ = 1.28; for the time that food was in the mouth, p = 0.73,t₍₁₅₎ = 0.36; 2-tailed ttests).