Activation of the central serotonergic system in response to delayed but not omitted rewards.
Bottom Line: The forebrain serotonergic system is a crucial component in the control of impulsive behaviours.By contrast, during the intermittent reward condition, in which food was given on only about one-third of the site visits, the level of dopamine was lower than that during the immediate reward condition, whereas the level of serotonin did not change significantly.This is the first direct evidence that activation of the serotonergic system occurs specifically in relation to waiting for a delayed reward.
Affiliation: Neural Computation Unit, Okinawa Institute of Science and Technology, Onna, Okinawa, Japan. email@example.comShow MeSH
Related in: MedlinePlus
Mentions: We used a free operant task that we termed a sequential food–water navigation task. Six rats were individually trained and tested in a cylindrical apparatus (1.5 m in diameter with a 45-cm-high wall); two cylinders, denoted food site and water site, were fixed at a relative angle of 45° (Fig. 1B). When the rat poked its nose through a small window, a control photo beam was interrupted, and a small food pellet (45 mg) was delivered at the food site or a spout for water was protruded at the water site. The open field apparatus was surrounded by a sound-proof box (2.5 × 2.5 m and 2.4 m in height). Four 100 W lamps were set at four corners of the box. Four lamps on and two lamps on indicated the start and end of the task, respectively. One speaker was positioned above the open field. The position of the rat was monitored by a video tracking system (CV-2000; Keyence, Osaka, Japan). To receive a reward at both sites, the rat was required to traverse through an imaginary circle (home-base circle; φ = 40 cm) monitored by the tracking system between the food and water sites. An 8 kHz tone (tone 1 – 0.3 s, 70 dB) was presented when the rat entered the circle for 0.2 s, signalling that a reward was available at one of the cylinders. If the rat nose-poked at an incorrect site after tone 1, a 500 Hz tone (tone 2 – 0.3 s, 72 dB) was presented, signalling an error. Rats could start the next trial at any time after reward consumption. Rats were trained once per day for 2 h. It took 3 weeks or less for the rats to learn the sequential food–water navigation task.
Affiliation: Neural Computation Unit, Okinawa Institute of Science and Technology, Onna, Okinawa, Japan. firstname.lastname@example.org