Fig. 4.

Density of Fos-positive units counted in the three prefrontal cortical regions: ordinates: counts mm⁻². Columns show the group mean data (+SEM) for the rats trained under the adjusting-delay (ADJ. DELAY), adjusting-magnitude (ADJ. MAG.) and no-delay schedules, and the control group of rats exposed to the food-deprivation condition without behavioural training (DEP. ONLY). The horizontal line indicates the group mean data from the control group. The rats trained under the ADJ. DELAY and ADJ. MAG. schedules showed enhanced Fos expression in the orbital prefrontal cortex compared to the control group (*P < 0.05: see text).