Behavioral control of visual fixation of the rhesus monkey.

A paradigm for the control of visual fixation of the macaque monkey in vision experiments was described. Using a Maxwellian view, the procedure permits the placement of discrete test-light stimuli in a specific area of the retina as the monkey fixates a primary target. This procedure holds foveal fixation as other behaviorally significant visual stimuli are presented to the visual field. By a methods-of-limits procedure, the sensitivity of the monkey eye was measured at different retinal locations under both photopic and scotopic visual adaptation.     

Perseveration of cardiac-rate effects in the rhesus monkey following pavlovian conditioning

The effects of Pavlovian conditioning on diurnal cardiac rate were studied in four rhesus monkeys. A three-hour conditioning period, consisting of 18 CS-UCS pairings with UCS an aversive tail-shock, produced cardiac-rate elevation which persisted for as long as 12 hours after the session.     

Short-term memory effects on the representation of two-dimensional space in the rhesus monkey

Human subjects represent the location of a point in 2D space using two independent dimensions (x–y in Euclidean or radius-angle in polar space), and encode location in memory along these dimensions using two levels of representation: a fine-grain value and a category. Here we determined whether monkeys possessed the ability to represent location with these two levels of coding. A rhesus monkey was trained to reproduce the location of a dot in a circle by pointing, after a delay period, on the location where a dot was presented. Five different delay periods (0.5–5 s) were used. The results showed that the monkey used a polar coordinate system to represent the fine-grain spatial coding, where the radius and angle of the dots were encoded independently. The variability of the spatial response and reaction time increased with longer delays. Furthermore, the animal was able to form a categorical representation of space that was delay-dependent. The responses avoided the circumference and the center of the circle, defining a categorical radial prototype around one third of the total radial length. This radial category was observed only at delay durations of 3–5 s. Finally, the monkey also formed angular categories with prototypes at the obliques of the quadrants of the circle, avoiding the horizontal and vertical axes. However, these prototypes were only observed at the 5-s delay and on dots lying on the circumference. These results indicate that monkeys may possess spatial cognitive abilities similar to humans.     

Maternal gestational stress alters adaptive and social behavior in adolescent rhesus monkey offspring

Data from rodent studies have indicated that stress experienced by pregnant mothers may result in behavioral and biological abnormalities in their offspring. However, few studies have examined the effects of prenatal stress on the offspring beyond the childhood period. In this study, 7 prenatally stressed (PNS) monkeys and 7 monkeys from undisturbed pregnancies were tested under mildly challenging conditions at 4 years of age. Following separation from cagemates and group formation, PNS monkeys showed more locomotion, abnormal and disturbance behavior than controls. Controls showed approximately six times more play than PNS animals. The PNS males showed the most clinging to others and the largest increase in contact with other animals over the period. Group differences were also found when the monkeys were observed as groups or alone in a playroom. Controls showed more explanatory behavior in the playroom, whereas PNS monkeys showed more inactivity. Control animals showed a decrease in distress vocalizations over time in the playroom, whereas PNS animals showed the opposite pattern. Control animals spent more time in proximity to and contact with cagemates than PNS animals. These results indicate that prenatal stress can have effects on adaptive and social behavior that persist into adolescence.     

Durable partial reinforcement effects and social dominance in the rat

Following partial reinforcement (PRF) or consistent reinforcement (CRF) of an approach response in a straight runway and experimental extinction, rats were given the arena food-dominance test in Experiment 1 and both the arena test and the tunnel-dominance test in Experiment 2. PRF subjects were dominant in the tunnel test, but subordinate in the arena test, regardless of which dominance test was given first. These durable and pervasive effects of partial reinforcement training can be interpreted in terms of frustration theory.     

Behavioral effects of testosterone in relation to social rank in the male rabbit

The role of gonadal androgens in favoring the adaptation to environmental pressure, including social organization, is well known. In the rabbit, testosterone administration increases marking behavior, and its level can be affected by agonistic interaction. In this experiment, we studied the effect of subcutaneous administration of testosterone propionate (TP) (3 mg/d for 6 days) in male rabbits belonging to the same social group (6 groups of 4 animals). In 2 additional groups (4 animals each), males were injected with almond oil. The animals were observed for 6 days in seminatural conditions, then treated with TP (or oil) and observed for another 6 days. The dominant/subordinate frequency ratio of behavioral patterns was used to rank the animals. The testosterone plasma concentration was correlated with agonistic behavior after the first period of social interaction. A significant increase of marking, digging, and defensive activity was observed after TP administration in all animals independent of rank, whereas this increase was not present in animals treated with oil. Agonistic and interactive behaviors increased significantly after TP treatment only in the first‐ranking animals. This indicates the influence of social rank in the modification of behaviors involving interactions among subjects Aggr. Behav. 29:269–278, 2003. © 2003 Wiley‐Liss, Inc.     

Two temporal parameters of free operant discriminated avoidance in the rhesus monkey

Four monkeys were exposed to free operant discriminated avoidance (discriminated Sidman avoidance) in a parametric study of safe stimulus and warning stimulus duration. The safe stimulus was assigned values of 2, 5, 10, 20, and 40 sec, the warning stimulus values of 2, 5, and 20 sec. Rate of responding was a decreasing negatively accelerated function of safe stimulus duration, with a small effect attributable to warning stimulus duration. Control of response rate by safe stimulus duration was due to the predominance of responding in the presence of the warning stimulus. Responding during the safe stimulus was independent of the temporal parameters except at schedules combining short safe and short warning stimulus durations. Latencies of responses in the warning stimulus were analyzed, and mean latency was found to be a direct function of warning stimulus duration, with only one exception, resulting from the order in which the warning stimulus values were presented. Shock rate was not systematically related to either of the manipulated parameters.