Behavioural features associated with VPA-treatment. A: Typical examples of rough-and-tumble play behaviours, a measure of play initiation and social interaction . The left panel illustrates an "attack" (animal on top) to the nape and the right panel a "pin" by the rat. B: Summarized data of rough-and-tumble play behaviours scored in a ten minute test session between control and VPA-treated animals. * p < 0.05. C: significant delay of about 1-2 days (p < 0.05) in eye opening between control and VPA-treated animals. Eye scoring, similar to that defined previously , is as follows; 0 closed, 1 half-open, 2 complete eye-opening. D: Rat pup body weight between groups (i.e. control and VPA-treated) during the first month of life beginning on the first day of injection (P6). There was no obvious difference between groups (p > 0.05), an indicator of normal physical development under the rearing conditions for treated animals . E: Cue-dependant associative learning for both VPA (black) and control (grey) animals. Rats were on a 47.5 h water deprivation schedule prior to training sessions. Animals were placed in the test cage and a 10 kHz sine-wave tone (5 pulses of 1 second in duration at 1 Hz) was present at random time points once the animal was in the opposite half of the cage relative to the reward location. Only when the 10 kHz tone was presented, was the reward (30% sucrose solution) available. Latency measurements represent the time between cue onset and arrival and orientation to the fixed reward location. F: Same protocol as in A, but now when the 10 kHz tone was presented, it was not reinforced (i.e. no reward was available). See Methods for more details. * p < 0.05; ** p < 0.01; ***p < 0.001.