Effect of current on the maximum possible reward.

Abstract

Using a 2-lever choice paradigm with concurrent variable interval schedules of reward, it was found that when pulse frequency is increased, the preference-determining rewarding effect of 0.5-s trains of brief cathodal pulses delivered to the medial forebrain bundle of the rat saturates (stops increasing) at values ranging from 200 to 631 pulses/s (pps). Raising the current lowered the saturation frequency, which confirms earlier, more extensive findings showing that the rewarding effect of short trains saturates at pulse frequencies that vary from less 100 pps to more than 800 pps, depending on the current. It was also found that the maximum possible reward-the magnitude of the reward at or beyond the saturation pulse frequency-increases with increasing current. Thus, increasing the current reduces the saturation frequency but increases the subjective magnitude of the maximum possible reward.

Cue-evoked dopamine release in the nucleus accumbens shell tracks reinforcer magnitude during intracranial self-stimulation

“…Thus, the precise timing and magnitude of reinforcement delivery can be tightly controlled and measured. Several pioneering studies in the field have shown that the magnitude of experienced reinforcement during ICSS is a function of both stimulation current and pulse frequency (Gallistel and Leon, 1991, Gallistel et al, 1991, Simmons and Gallistel, 1994, Arvanitogiannis and Shizgal, 2008). It has been hypothesized that the maximum possible reward during ICSS can be attained by manipulating stimulation current (Waraczynski and Kaplan, 1990, Gallistel et al, 1991, Sax and Gallistel, 1991).…”

“…Next, a threshold curve was determined for each animal (n=6) to establish their low, medium and high reinforcer magnitude levels (Gallistel and Leon, 1991, Gallistel et al, 1991, Simmons and Gallistel, 1994, Arvanitogiannis and Shizgal, 2008). This was accomplished by measuring the number of reinforced presses in separate 1 min intervals for different stimulation currents.…”

Retrospective and prospective coding for predicted reward in the sensory thalamus

“…The same cue stimulus was associated with ®ve different rewards: water (50 ml); two different amounts of sucrose solution (50 and 100 ml); and two different intensities of ICSS (70 and 140 mA). Reward value was assumed to increase in the order 21 : water, ,50 ml sucrose solution and ,100 ml sucrose solution for the natural rewards; and 70 mA ICSS and ,140 mA ICSS for the arti®cial rewards. For the neuron in Fig.…”

Adaptation effects of medial forebrain bundle micro-electrical stimulation

“…The frequency was tested at 100, 250, 400 Hz. According to the articles, with increasing frequency the tendency of the rat to press the key increases, and with increasing frequency, the number of pressures should also be increased [13,23]. Adaptation is significant over time.…”

“…William Hods did a similar job, and implanted electrodes in various reward areas [22]. In 1991, the effect of the current on the maximum reward expressed, it was concluded that when the pulse frequency increases, the pulses sent to the MFB are saturated at a range of 200 to 361 pulses per second, and there is no increase more than that [23].…”