Nictitating membrane and corneo-retinal transducers for conditioning in rabbits.

Describes a photosensitive and a DC biopotential recording method. Considering advantages and disadvantages of each, it is concluded that the biopotential method is unsuitable in experiments recording UCRs to electric shock. "In physiological experiments in which the rabbit must be restrained, eyeblink, nictitating membrane, or corneo-retinal responses may also be used as operants in preference to the conventional bar press." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Communication of affect in "cooperative conditioning" of rhesus monkeys.

"Rhesus monkeys in primate chairs were conditioned to bar press within 6 seconds of presentation of a light in order to avoid electric shock. Following acquisition of this avoidance response two animals were placed facing each other and the bar was removed from the chair of one monkey and the stimulus light from the chair of the other. In order for either monkey to avoid shock a communication was necessary since neither animal had access to all elements of the problem. The results indicated that through nonverbal communication of affect an efficient mutual avoidance was performed. It was concluded that this paradigm is an exceptionally efficient and sensitive method for investigations of nonverbal communication." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of electric-shock delivery on schedule-induced water intake: delay of shock, shock intensity, and body-weight loss

In each of four experiments, schedule-induced water intake in the rat was studied under fixed-time 40-sec food delivery. Experiments I and II studied the temporal relationship between response-independent electric-shock delivery and licking. Shock was delivered under a variable-time 60-sec schedule. A lick-dependent delay was imposed so that licking and shock delivery were systematically separated in time by a minimum of 1 to 15 sec. Over a wide range of shock intensities the data failed to reveal a consistent delay-of-shock effect. Similar shock intensities led to similar reduction of water intake at each delay of shock interval. Experiments III and IV studied the effects of body-weight loss on water intake during independent shock delivery. In Experiment III, shock was delivered under variable-time 60-sec with a minimum separation between shock and licking of 5 sec. In Experiment IV, shock was delivered under variable-time 180-sec. The minimum separation between shock and licking was 10 sec. In each study, the resistance of water intake to suppression by shock delivery increased as the degree of body-weight loss increased. Schedule-induced water intake was affected more by shock when the animal was maintained at 90% of free-feeding weight than at 70%.     

Enjoyment of perspective transformations induced by movement.

15 Ss viewed 18 geometric solids in a fixed location for 5 sec. Another 15 Ss saw the same objects moving for 5 sec across the field at a rate of 5.4Deg. of visual field/sec. Each object under each condition was rated on a 0-100 point scale of visual acceptability. It was found that the 3 regular polyhedrons which were most complex were rated highest in visual acceptability where stationary, but declined reliably in preference when moving. Simpler objects generally increased in preference under the moving condition. Findings are related to the use of simple exterior shells in contemporary architecture, and discussed in theoretical and historical contexts. (French summary) (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choice of delay of inevitable shock.

Human Ss tended to choose a short, rather than a long, delay of inevitable shock; the longer the delay the less tendency there was to choose it. Over trials, preference for the 0 delay at first decreased and then increased. This U shaped curve was much less marked in the high-shock group than in the low. Ss in the low-shock group tended to choose the 0 delay on 2 or 3 trials (out of 6); but Ss in the high-shock group tended to choose it either on 5 or 6 trials, or not at all. Threatening S with an even stronger shock enhanced the tendency to choose the 0 delay. Reaction time was fairly stable throughout. GSR at the instant of shock showed no consistent pattern. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-administered cocaine causes long-lasting increases in impulsive choice in a delay discounting task.

Cocaine use is associated with high levels of impulsive choice (preference for immediate over delayed rewards), but it is not clear whether cocaine use causes elevated impulsive choice, or whether elevated impulsive choice is solely a predisposing factor for cocaine use. This study examined the effects of prior cocaine self-administration on rats performing a delay discounting task commonly used to measure impulsive choice. Male Long-Evans rats were implanted with intravenous catheters, and following recovery, were trained to self-administer 30 mg/kg/day cocaine HCl (approx. 0.5 mg/kg/infusion) for 14 consecutive days (a control group received yoked intravenous saline infusions). Following three weeks of withdrawal, all rats were food-restricted and began training on the delay discounting task in standard operant chambers. On each trial, rats were given a choice between two levers. A press on one lever delivered a small food reward immediately, and a press on the other delivered a large food reward after a variable delay period. Rats that self-administered cocaine displayed greater impulsive choice (enhanced preference for the small immediate over the large delayed reward, as reflected by shorter indifference points) compared to controls, but were no different from controls on a “probabilistic discounting” task in which they chose between small certain and large uncertain rewards. These data suggest that self-administered cocaine can cause lasting elevations in impulsive choice, and that the high levels of impulsive choice observed in human cocaine users may be due in part to long-term effects of cocaine on brain function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects on effort discounting induced by inactivations of the nucleus accumbens core or shell.

The authors investigated the contribution of the nucleus accumbens (NAc) core and shell to effort-based decision making using a discounting procedure. Selection of 1 lever delivered a smaller, 2-pellet reward immediately, whereas the other lever delivered a 4-pellet reward after a fixed ratio of presses (2, 5, 10, or 20) that increased over 4 blocks of 10 discrete choice trials. Subsequent testing employed an equivalent delays procedure, whereby the relative delay to reward delivery after selection of either option was equalized. In well-trained rats, inactivation of the core, but not the shell, via infusion of GABA A/B agonists muscimol/baclofen reduced preference for the high-effort option under standard conditions and also when rats were tested using an equivalent delays procedure. However, inactivation of the core did not alter preference for 4-pellet versus 2-pellet rewards when the relative costs of each option were the same (1 press). Thus, the NAc core, but not the shell, appears to be part of a neural circuit that biases choice toward larger rewards associated with a greater effort cost. Furthermore, the contributions by the NAc core to this form of decision making can be dissociated from its role in delay discounting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cocaine exposure causes long-term increases in impulsive choice.

In this study, the authors examined the long-term effects of prior exposure to cocaine on a delay-discounting task commonly used to measure impulsive choice. Male Long-Evans rats received daily intraperitoneal injections of 30 mg/kg cocaine HCl or saline for 14 days. Following 3 weeks of withdrawal, rats began training. On each trial, rats were given a choice between 2 levers. A press on 1 lever resulted in immediate delivery of a single 45-mg food pellet, and a press on the other resulted in delivery of 4 pellets after a delay period. Impulsive choice was defined as preference for the small immediate over the large delayed reward. Three months after treatment, cocaine-exposed rats displayed increased impulsive choice behavior. They also showed less anticipatory responding (entries into the food trough) during the delays prior to reward delivery, indicating that the enhanced impulsive choice in these rats may be related to deficits in bridging the delay between response and reward. These data demonstrate that cocaine exposure can cause enduring increases in impulsive choice behavior, consistent with observations in human subjects with drug addictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats prefer signaled over unsignaled shock-free periods.

Three experiments with 48 female rats investigated Ss' preference for a schedule of shock containing signaled shock-free periods (SSF schedule) or the same shock schedule without signals (unsignaled schedule). Exp I was a replication of the shuttle-box experiment reported by M. S. Fanselow (see record 1981-00807-001), in which rats preferred unsignaled shock over the SSF schedule. Contrary to Fanselow's results, Ss in Exp I failed to develop a preference. In Exp II, forced-exposure training was added, testing was extended from 2 165-min sessions to 8, and a reversal phase was added. Results show that 3 of 4 Ss preferred the SSF schedule, and 2 of these continued to prefer it after reversal. In Exp III, forced-exposure training was eliminated, but signals were lengthened from 30 to 60 sec, and the test was extended to 12 sessions. Results show that Ss choosing between the unsignaled and SSF schedules chose the SSF schedule, whereas a random control group chose the unsignaled schedule. Findings indicate that choice between active schedules is determined by the relative aversiveness of all stimuli presented and not, as implied by contextual fear analysis, by that of contextual stimuli alone. (25 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Shock-induced analgesia on the formalin test: Effects of shock severity, naloxone, hypophysectomy, and associative variables.

In 5 experiments, 272 female Long-Evans rats were exposed to 3 shocks, spaced 20 sec apart, at 2 levels of severity: low (.75 sec, 1 mA) and high (3 sec, 4 mA). Both shock levels produced a similar suppression of the recuperative behavior elicited by an injection of formalin into the S's hindpaw. Naloxone fully reversed the analgesia produced by the low shock but only partially reversed the analgesia produced by the high shock. Hypophysectomy did not alter the level of analgesia. When the Ss were tested in a chamber different from the one in which they were shocked, both analgesias were totally reversed. However, imposing a delay between shock and analgesia testing did not reduce analgesia. In all experiments, the freezing response was monitored simultaneously with recuperative behavior. A parallel was found between analgesia and this defensive response, suggesting that an animal's endogenous analgesic systems may be activated along with its defensive motivational system. Results point to the critical nature of associative variables in the control of endogenous analgesic systems and suggest that shock severity is a determinant of analgesia's sensitivity to naloxone. (67 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using signaled barpressing tasks to study the neural substrates of appetitive and aversive learning in rats: Behavioral manipulations and cerebellar lesions.

Describes the development of standard within-S conditioning tasks for studying similarities and differences in the neural substrates of appetitive and aversive learning. Rats learned to press a bar during a brief tone presentation to receive a food pellet reward (the appetitive task). Using the same tone signal, conditioning chamber, and trial timing parameters, the same rats were then trained to press the bar during the tone presentation to avoid a mild footshock (the aversive task). As an initial study of the neural substrates of these forms of learning, the involvement of the cerebellum was assessed. Bilateral lesions of the deep cerebellar nuclei prevented the learning of the aversive task but had no effect on the learning of the appetitive task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Punishment of consummatory and instrumental behavior: Effects on licking and bar pressing in rats.

Maintained licking and bar pressing in 48 male hooded rats by intermittent water reinforcement. Shock punishment was delivered for either a reinforced or nonreinforced lick or bar-press response. Punishment suppressed licking more than bar pressing. Pairing punishment with reinforcement had little effect on overall response suppression. In Exp. II with 18 Ss, Ss punished for the 1st lick after a reinforced bar press showed more response suppression than Ss punished for the reinforced bar press. Results support R. Solomon's (see record 1965-00694-001) hypothesis than consummatory behavior is more sensitive to punishment than instrumental behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within subjects partial reinforcement extinction effects for a bar pressing task.

Trained 24 male albino Sprague-Dawley rats to barpress for water during both continuous and partial reinforcement of their responses. In extinction, Ss trained to press 1 bar during continuous reinforcement and a 2nd bar during partial reinforcement made more correct responses in the partial than in the continuous reinforcement condition. No difference in response rates was observed for Ss who learned the same response during both reinforcement schedules. Pairing different lighting conditions with the different schedules of reinforcement had no effect on these results, but did affect other response measures. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bar pressing for illumination change in albino rats with septal lesions.

Gave 43 sham-operated and septally-lesioned male Sprague-Dawley albino rats the opportunity to control illumination with a bar press. Ss with septal lesions changed illumination conditions more often, but spent less total time in the light, than controls. Therefore, compared with controls, Ss with septal lesions displayed both a greater preference for stimulus change and enhanced aversion for the illumination level used. A finding that such alterations in reactivity to light were maintained for 14 days is interpreted as being analogous to the effects of septal lesions on consumption of palatable and unpalatable fluids. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Antipunishment activity of diazepam in rats trained to discriminate diazepam from vehicle.

The anxiolytic and discriminative stimulus effects of drugs in the same rats during a single session were examined in this study. Rats were trained to discriminate diazepam (5 mg/kg) from vehicle in a 2-lever drug discrimination procedure and were then trained to press a 3rd lever under a multiple fixed-interval (60 sec), fixed-ratio 5 + shock schedule of food reward. Diazepam produced substitution for itself in all rats; however, it produced antipunishment effects in some of the rats, suggesting that its discriminative stimulus and antipunishment effects are separable. In contrast, the N-methyl-{d}-aspartate antagonists, NPC 17742 and phencyclidine, failed to substitute fully for diazepam and did not increase punished responding in any of the rats. These results are consistent with those of studies showing that drugs from this class produce weaker antipunishment effects than diazepam does. The potential utility of this new method is that it allows direct comparisons of the antipunishment and discriminative stimulus effects of putative anxiolytic drugs during a single session with the same animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of secondary reinforcement effects in a comparison of partial reinforcement and partial delay of reinforcement.

Studied the effects of partial reinforcement and partial delay on extinction performance. 72 naive female albino Sprague-Dawley rats served as Ss. Secondary reinforcement effects were controlled by using the same delay-of-magazine interval on nonreinforcement trials with partial reinforcement (delay of empty magazine) as occurred on delayed trials with partial delay (delay of magazine containing sucrose). 4 delay intervals (0, 15, 30, and 45 sec) were factorially combined with the schedule variable. Resistance to extinction was an increasing function for the length of the delay interval and was greater for partial reinforcement than for partial delay. No interaction was observed to occur between the length of the delay interval and type of reinforcement schedule. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect on choice of absolute and relative values of reinforcer delay, amount, and frequency.

Three experiments used pigeons to examine the assumption of the matching law that relative and not absolute values of reinforcement control preference. Experiment 1 examined this assumption for reinforcer delay, Experiment 2 for reinforcer amount, and Experiment 3 for reinforcer frequency. In each experiment reinforcers were programmed according to nonindependent concurrent variable-interval variable-interval schedules. In all three experiments, there was an orderly change in preference as the absolute value of the aspect of reinforcement being investigated was varied, even though relative value was held constant. Preference for the shorter delay decreased as the absolute values of delay were decreased; preference for the larger amount decreased as the absolute values of amount were increased; and preference for the more frequent reinforcer decreased as the absolute values of reinforcer frequency were decreased. Several alternative models were considered, but none of these models could describe all of the data. The implications of these findings for modeling of choice behavior are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychopathy and choice of immediate versus delayed punishment.

This study tested the hypothesis that psychopathic Ss would show less preference for immediate shock than would nonpsychopathic Ss. 12 psychopathic and 12 nonpsychopathic criminals and 19 noncriminals were presented with 6 trials in which they were required to choose between an immediate shock and 1 delayed 10 sec. The results confirmed the hypothesis (p     

"Temporal summation decay" in hypothalamic self-stimulation: Threshold changes at long intrapair intervals due to axonal subnormal periods.

Rats were trained to bar press for trains of conditioning (C) and test (T) pulses delivered via lateral hypothalamic electrodes. As intrapair (C–T) intervals increased from 10 msec to 100 msec, the frequency of pulses required for self-stimulation increased, similar to results of N. S. Smith and E. E. Coons (1970). This effect was observed only for electrode placements where self-stimulation was obtained at frequencies below 16 Hz and currents of 600 μA and higher. The effect was larger when the train duration was increased from 0.5 sec to 2.0 sec. The threshold increase was abolished when the T pulses were greater in current than the C pulses but not when C pulses were larger than T pulses. The larger T pulses also removed relative refractory period effects at a C–T interval of 1.0 msec. Therefore, the increase in required current or frequency at long C–T intervals appears to be due to a decline in axonal excitability (i.e., the subnormal period) rather than a decay in synaptic temporal summation. Possible flaws in other reports of paired-pulse "temporal summation decay" at long C–T intervals using 2 electrodes are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the effects of immediate reinforcement, constant delay of reinforcement, and partial delay of reinforcement on performance.

Investigated the relation between immediate reward, constant delay of reward, and partial delay of reward in 3 experiments with 149 naive female Sprague-Dawley rats. A discrete operant bar-press apparatus was employed. In Exp. I, constant delay produced less resistance to extinction than either immediate reward or partial delay, which were not different from each other. Changing the delay contingencies from training to extinction did not substantially influence performance. Exp. II showed that resistance to extinction was an increasing function of the length of the delay interval (7.5, 15, 30, or 45 sec.) in a partial-delay paradigm, and Exp. III demonstrated that resistance to extinction was a decreasing function of a constant delay interval (15, 30, or 45 sec.). Results are discussed in the context of A. Amsel's frustration theory and E. J. Capaldi's sequential hypothesis. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)