Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. I. Linear acceleration responses during off-vertical axis rotation

1. The dynamic properties of otolith-ocular reflexes elicited by sinusoidal linear acceleration along the three cardinal head axes were studied during off-vertical axis rotations in rhesus monkeys. As the head rotates in space at constant velocity about an off-vertical axis, otolith-ocular reflexes are elicited in response to the sinusoidally varying linear acceleration (gravity) components along the interaural, nasooccipital, or vertical head axis. Because the frequency of these sinusoidal stimuli is proportional to the velocity of rotation, rotation at low and moderately fast speeds allows the study of the mid-and low-frequency dynamics of these otolith-ocular reflexes. 2. Animals were rotated in complete darkness in the yaw, pitch, and roll planes at velocities ranging between 7.4 and 184 degrees/s. Accordingly, otolith-ocular reflexes (manifested as sinusoidal modulations in eye position and/or slow-phase eye velocity) were quantitatively studied for stimulus frequencies ranging between 0.02 and 0.51 Hz. During yaw and roll rotation, torsional, vertical, and horizontal slow-phase eye velocity was sinusoidally modulated as a function of head position. The amplitudes of these responses were symmetric for rotations in opposite directions. In contrast, mainly vertical slow-phase eye velocity was modulated during pitch rotation. This modulation was asymmetric for rotations in opposite direction. 3. Each of these response components in a given rotation plane could be associated with an otolith-ocular response vector whose sensitivity, temporal phase, and spatial orientation were estimated on the basis of the amplitude and phase of sinusoidal modulations during both directions of rotation. Based on this analysis, which was performed either for slow-phase eye velocity alone or for total eye excursion (including both slow and fast eye movements), two distinct response patterns were observed: 1) response vectors with pronounced dynamics and spatial/temporal properties that could be characterized as the low-frequency range of "translational" otolith-ocular reflexes; and 2) response vectors associated with an eye position modulation in phase with head position ("tilt" otolith-ocular reflexes). 4. The responses associated with two otolith-ocular vectors with pronounced dynamics consisted of horizontal eye movements evoked as a function of gravity along the interaural axis and vertical eye movements elicited as a function of gravity along the vertical head axis. Both responses were characterized by a slow-phase eye velocity sensitivity that increased three- to five-fold and large phase changes of approximately 100-180 degrees between 0.02 and 0.51 Hz. These dynamic properties could suggest nontraditional temporal processing in utriculoocular and sacculoocular pathways, possibly involving spatiotemporal otolith-ocular interactions. 5. The two otolith-ocular vectors associated with eye position responses in phase with head position (tilt otolith-ocular reflexes) consisted of torsional eye movements in response to gravity along the interaural axis, and vertical eye movements in response to gravity along the nasooccipital head axis. These otolith-ocular responses did not result from an otolithic effect on slow eye movements alone. Particularly at high frequencies (i.e., high speed rotations), saccades were responsible for most of the modulation of torsional and vertical eye position, which was relatively large (on average +/- 8-10 degrees/g) and remained independent of frequency. Such reflex dynamics can be simulated by a direct coupling of primary otolith afferent inputs to the oculomotor plant. (ABSTRACT TRUNCATED)     

Observational conditioning of snake fear in rhesus monkeys.

Hypothesized that observational conditioning is involved in the origins of many human and nonhuman primates' fears and phobias. In Exp I, a new index of snake fear in 7 19–28 yr old wild-reared rhesus monkeys and 9 laboratory-reared offspring (aged 8 mo to 6 yrs) was tested. Results show the measure was useful and demonstrated that young Ss raised by parents who had a fear of snakes did not acquire the fear in the absence of any specific experience with snakes. In Exp II, using 5 of the wild-reared Ss and 6 of the laboratory-reared Ss from Exp I, 5 of 6 offspring acquired an intense and persistent fear of snakes as a result of observing their wild-reared parents behave fearfully in the presence of real, toy, or model snakes for a short period of time. The fear was not context specific and showed no significant signs of diminution at 3-mo follow-up. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abnormal social development of protein-malnourished rhesus monkeys.

Reports results of an experiment with 2 groups of 5 rhesus monkeys. Ss fed diets deficient in protein (3.5% casein) exhibited social behaviors qualitatively different from controls fed diets sufficient in protein (25% casein). In general, the protein-malnourished Ss showed a lack of reciprocal responsiveness to social initiations, aggression, and a predominance of nonsocially-directed behaviors when compared to controls. Results are discussed in terms of a nutritional-environmental interaction that produces abnormal and possibly long-term deficits in social development. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Music perception and octave generalization in rhesus monkeys.

Two rhesus monkeys were tested for octave generalization in 8 experiments by transposing 6- and 7-note musical passages by an octave and requiring same or different judgments. The monkeys showed no octave generalization to random-synthetic melodies, atonal melodies, or individual notes. They did show complete octave generalization to childhood songs (e.g., "Happy Birthday") and tonal melodies (from a tonality algorithm). Octave generalization was equally strong for 2-octave transpositions but not for 0.5 or 1.5-octave transpositions of childhood songs. These results combine to show that tonal melodies form musical gestalts for monkeys, as they do for humans, and retain their identity when transposed with whole octaves so that chroma (key) is preserved. This conclusion implicates similar transduction, storage, processing, and relational memory of musical passages in monkeys and humans and has implications for nature–nurture origins of music perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frustration and self-aggression in social isolate rhesus monkeys.

Compared the frequency of self-aggressive behavior emitted by 6 partial social isolate and 6 socialized rhesus monkeys under baseline living conditions and a continuous reinforcement-extinction schedule of leverpressing. Under baseline conditions, male isolates showed higher levels of self-aggressive behavior than did the female isolates. Further, frustration produced by extinction of the leverpressing response produced a significant but transitory intensification of self-aggressive behavior. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discounting of cocaine by rhesus monkeys.

The present, subjective value of a reinforcer typically decreases as a function of the delay to its receipt, a phenomenon termed delay discounting. Delay discounting, which is assumed to reflect impulsivity, is hypothesized to play an important role in drug abuse. The present study examined delay discounting of cocaine injections by rhesus monkeys. Subjects were studied on a discrete-trials task in which they chose between 2 doses of cocaine: a smaller, immediate dose and a larger, delayed dose. The immediate dose varied between 0.012 and 0.4 mg/kg/injection, whereas the delayed dose was always 0.2 mg/kg/injection and was delivered after a delay that varied between 0 and 300 s in different conditions. At each delay, the point at which a monkey chose the immediate and delayed doses equally often (i.e., the ED50) provided a measure of the present, subjective value of the delayed dose. Dose-response functions for the immediate dose shifted to the left as delay increased. The amount of the immediate dose predicted to be equal in subjective value to the delayed dose decreased as a function of the delay, and hyperbolic discounting functions provided good fits to the data (median R2 = .86). The current approach may provide the basis for an animal model of the effect of delay on the subjective value of drugs of abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors influencing sexual performance in male rhesus monkeys.

Describes a 5-yr retrospective study of the sexual behavior of 8 adult rhesus monkeys showing that sexual vigor declined over the years but testosterone levels in peripheral vein plasma did not. Two prospective experiments were carried out on these males during the 6th yr: (a) The 4 poorest performers were injected daily for 28 days with testosterone propionate (1 mg/kg). There was no significant increase in level of performance, and behavior was not correlated with plasma levels of testosterone either before or 24 hrs after the last hormone injection. (b) All 8 males were exposed to novel nonspecific sensory stimulation during tests of sexual behavior. Eight different adult male rhesus strangers—present in the room but not in the test cage—were used as stimuli, one for each experimental test. Sexual behavior during experimental and control tests did not differ. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive function in aged ovariectomized female rhesus monkeys.

To determine whether ovariectomy exacerbates age-related cognitive decline, the performance of 6 aged monkeys that had been ovariectomized early in life (OVX-Aged) was compared to that of 8 age-matched controls with intact ovaries (INT-Aged) and that of 5 young controls with intact ovaries (INT-Young) in tasks of visual recognition memory, object and spatial memory, and executive function. The OVX-Aged monkeys were marginally more impaired than the INT-Aged monkeys on the delayed nonmatching-to-sample with a 600-s delay. In contrast, they performed significantly better than the INT-Aged controls on the spatial condition of the delayed recognition span test. The hypothesis that prolonged estrogenic deprivation may exaggerate the age-related decline in visual recognition memory will require additional support. However, the findings suggest that long-term ovariectomy may protect against the development with aging of spatial memory deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning of compound geometric forms in infant rhesus monkeys.

Human infants younger than 2 mo scan predominantly the external contours of compound figures; in contrast, 2-mo-olds scan internal and external features of such patterns. Whether infant rhesus monkeys (N?=?12) show a similar shift over the first weeks of life was examined in the present study. Visual activity was monitored while Ss viewed squares with internal details, a square without internal details, and the internal details alone. Results show that Ss scanned the internal details of compound figures even during the first week of life. By Weeks 3 and 7, they scanned the internal details less, increasing fixations of the external contour. Amount of looking during the first week was influenced predominantly by the number of elements in a pattern; in contrast, at Weeks 3 and 7 it was influenced foremost by the amount of perimeter and secondarily by the number of elements. The differences between visual activity in rhesus and human infants are discussed. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observational conditioning of snake fear in unrelated rhesus monkeys.

Extended the findings of the present 2nd author et al (see record 1985-05872-001) in 2 experiments, using 4 rhesus monkeys as models and 18 rhesus monkeys as observers. In Exp I, 2 wild-reared Ss with a strong fear of snakes served as models, and 10 laboratory-reared Ss with no initial snake fear, who were acquainted with but not related to their models, served as observers. The observers showed asymptotic levels of fear in another context (the Sackett Self-Selection Circus) after only 8 min of watching their models behave fearfully in the presence of snake stimuli in the Wisconsin general test apparatus. In Exp II, 2 observers from Exp I who had acquired snake fear vicariously served as models for 8 other unrelated, and for the most part unacquainted, laboratory-reared Ss. Results are similar to those for Exp I, except that the level of acquired or maintained fear was slightly lower in Exp II. The differences in level of fear in the 2 experiments are discussed in relation to the possible effects of the model's age, dominance status, rearing history, and level of fear and to possible mechanisms underlying observational conditioning. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exaggeration of self-aggression following alcohol ingestion in rhesus monkeys.

Recorded self-directed aggressive behavior in 11 rhesus macaques. 4 Ss were given 5-15% ethyl alcohol in various combinations; the others served as controls. Self-aggression increased with an increase in the amount of alcohol ingested, independent of thirst or reduced fluid intake. In contrast, alcohol has been reported to ameliorate self-mutilating behaviors of children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smoked heroin self-administration in rhesus monkeys

The Symphysis Pubis (SP) joint was investigated by X-ray in 96 adults without any history of disease of the joints. We evaluated the width of this joint by measuring the distance between the two articular surface at three points. We calculated the mean for the three interpubic distances and carried out statistical analysis so as to evaluate if there is a significative difference between the four age classes (< 50; 50-59; 60-69; > 70) and between males and females. We did not found statistically-significative differences between males and females, and between the age classes; nevertheless, it is to be noted that a slight widening of the SP joint can be seen in the elderly, which is thus not significant. We also noted that the medium part of the SP joint undergoes a larger widening in older people: this is probably due to degenerative changes in the fibrocartilagineous disc and the ligaments.     

Early experience and complexity of social organization in groups of young rhesus monkeys (Macaca mulatta).

Found that 2 6-member social groups of young rhesus monkeys, one socially deprived and the other raised with mother and age-mates, showed marked differences in the complexity of social organization. Compared to deprived Ss, experienced Ss interacted more often as trios and larger subgroups, and the response structure of their triadic subgroups was more complex. Only in the experienced group did functional aspects of triadic interactions suggest that 1 individual recognized the status relations between the other participants. These findings indicate that early social experience affects levels of social competence that transcend variations in ethologically derived response patterns and that cannot be seen in arranged dyadic encounters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavior of rhesus monkeys during artificial menstrual cycles.

Daily sc injections of estradiol, progesterone, and testosterone were given to 17 ovariectomized rhesus monkeys in amounts that imitated accurately the changing plasma levels of hormones in intact females with natural menstrual cycles. Because these cycles in ovariectomized, treated Ss were terminated by normal vaginal bleeding every 28 days and showed a midcycle gonadotropin surge, the authors termed them "artificial menstrual cycles." In dyadic mating tests, changes in the females' access times (leverpressing) for males, and in the males' ejaculatory performance, were closely similar during natural and artificial cycles, and there were well-marked behavioral rhythms. These rhythms were lost during 28-day control periods when ovariectomized Ss received injections of vehicle alone. Differences in ejaculatory performance during natural and artificial cycles could be accounted for by an order effect. It is concluded that the artificial cycle provides a valid and useful paradigm for a more detailed study of the neuroendocrine regulation of primate reproductive behavior. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of hunger on nonnutritive sucking in infant rhesus monkeys.

In Experiment I the thumbsucking of 5 Ss aged 90-180 days was measured at 0, 2.5, 7.5, and 10 hr. after feeding. In Experiment II these same Ss, now between ages 180 and 270 days, were observed at intervals of 0, 37.5, 75, 112.5, 250 min., and 10 hr. after feeding. In Experiment III 6 additional monkeys 90-180 days of age were observed at the 1st 5 intervals of Experiment II. In all experiments thumbsucking increased with hunger. In Experiment II there was no significant increase in sucking during the intervals between 0 and 250 min. Experiment III results showed a significant increase during this period suggesting that the effectiveness of specific deprivation intervals decreases with age. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of differential pretraining on learning-set formation in rhesus monkeys.

Compared the rate of learning-set formation by 4 rhesus monkeys that had previously been pretrained on the win-stay component of the learning-set strategy (Group WS) to the rate evidenced by 4 others that had pretraining on the lose-shift component (Group LS). Differences between groups were small, and asymptotic levels were below those previously obtained by monkeys without pretraining. The negative transfer resulted from generalized tendencies to perseverate or shift (Groups WS and LS, respectively), regardless of response outcome. The former tendency dissipated relatively rapidly, while the latter persisted very markedly throughout the 400-problem learning-set series. It is noted that learning-set formation requires a balance between the win-stay and lose-shift components; however, the optimal ratio is unknown. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abnormal behavior in relation to cage size in rhesus monkeys.

Rhesus monkeys (Macaca mulatta) either of wild origin or mother-reared in the laboratory were housed along in small caged from birth to 6? yrs. Observations were made on 24 Ss that were introduced singly into a small and a large test cage. Both the laboratory mother-reared and the wild-reared Ss showed abnormal behavior. The extent of the normal behavior repertoire was not smaller in Ss showing a relatively large degree of abnormal behavior. In a large cage, more normal but less stereotyped locomotion was shown than in a small cage. However, nonlocomotory abnormal patterns were not influenced by cage dimensions. The various abnormal behaviors were randomly associated. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial orienting of attention in adult and aged rhesus monkeys.

Aging produces changes in a variety of neural systems that result in a distinct neuropsychological profile of cognitive deficits. To determine the extent of functional decline in cognition with aging, the authors assessed attentional ability in adult (10–15 yr old) and aged (28–33 yr old) rhesus monkeys (Macaca mulatta) in 3 experiments, using a paradigm adapted from M. I. Posner et al (1984), in which a peripheral cue indicates the probable location of a target. Orienting of attention was not disrupted in aged monkeys. Response times of aged monkeys were comparable with adult monkeys' both in the attention task and in a simple reaction time task. These results suggest that the neural systems that subserve spatial orienting of attention remain intact in aged nonhuman primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Socially mediated reduction in emotional responses of young rhesus monkeys.

"Two studies investigated the effect of various social stimuli upon emotional responsiveness of 12 young rhesus monkeys raised in the laboratory in the visual presence of other young monkeys… . results suggest that the nature of Ss' previous social experience was an important determinant of stimulus effectiveness in reducing emotional distress. The capacity of a social stimulus to mitigate emotional disturbance did not appear to be dependent upon nor derived from feeding or other nurturant experience." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metabolic disturbances in Plasmodium coatneyi-infected rhesus monkeys

To investigate metabolic disturbances in an animal model of human malaria, four rhesus monkeys (Macaca mulatta) were infected with Plasmodium coatneyi, a parasite which induces cytoadherence of infected erythrocytes. When moribund or the parasitaemia had plateaued, the monkeys were sacrificed (3 animals) or treated with chloroquine (1 animal). Blood and cerebrospinal fluid (CSF) were sampled at intervals between inoculation and sacrifice or treatment. Arterial and CSF glucose and lactate rose during infection, indicating evolving insulin resistance. The arteriovenous difference in glucose concentration also increased, consistent with increased glucose consumption by parasitised tissues. Arterial plasma lactate rose but a positive arteriovenous concentration difference suggested tissue lactate uptake. The animal with the highest plasma lactate at sacrifice remained hyperglycaemic but also had the highest CSF lactate, the greatest cerebral sequestration and neurological depression, and biochemical and histological evidence of severe hepatic pathology. Serum cholesterol and corrected serum calcium fell consistently during infection; serum phosphate was also reduced in animals without renal impairment. These preliminary results indicate that lactic acidosis is a late complication of severe malaria and, by implication from this and other studies, hypoglycaemia occurs even later; other metabolic changes during P. coatneyi infection in rhesus monkeys also parallel those of severe falciparum malaria in humans. The model could be used in further studies of malaria-associated metabolic dysfunction and its management.