Manual and hemispheric specialization in the manipulation of a joystick by baboons (Papio papio)

An autonomous, automated and mobile device to concurrently assess several cognitive functions in group-living non-human primates

Research methods in cognitive neuroscience using non-human primates have undergone notable changes over the last decades. Recently, several research groups have described freely accessible devices equipped with a touchscreen interface. Two characteristics of such systems are of particular interest: some apparatuses include automated identification of subjects, while others are mobile. Here, we designed, tested and validated an experimental system that, for the first time, combine automatization and mobility. Moreover, our system allows autonomous learning and testing of cognitive performance in group-living subjects, including follow-up assessments. The mobile apparatus is designed to be available 24h a day, 7days a week, in a typical confined primate breeding and housing facility. Here we present as proof of concept, the results of two pilot studies. We report that rhesus macaques (Macaca mulatta) learned the tasks rapidly and achieved high-level of stable performance. Approaches of this kind should be developed for future pharmacological and biomedical studies in non-human primates.

Absence of established sex differences in patients with schizophrenia on a two-dimensional object array task

Sex differences are pervasive in schizophrenia, ranging from differences in the age of onset and symptoms of the illness to structural brain differences. Yet, there has been very little research on the interaction of these differences with established cognitive sex differences that exist in healthy populations. We tested 25 patients with schizophrenia and 17 healthy controls on a two-dimensional task of object location memory. It has been previously shown that healthy females outperform healthy males on this task, a result that was upheld in this experiment. However, the female advantage is completely absent in patients with schizophrenia. This finding has important implications for the interpretation of clinical and physiological sex differences present in schizophrenia.

The study of hemispheric specialization for categorical and coordinate spatial relations in animals

This article reviews some of the most representative studies in the animal literature pertaining to the processing of categorical and coordinate spatial relations and of their hemispheric control. Although the processing of coordinate and categorical cognition has been studied directly with nonhuman primates, experiments on cerebral asymmetries in avian spatial orientation are also reviewed. It turns out that Kosslyn's model concerning the existence of two types of spatial representations each with a specific lateralization pattern has received some support in nonhuman primates and is only weakly verified in the avian studies. Procedural differences might explain some but certainly not all of the discrepancies between the human and the animal literature. It is especially the laterality hypothesis of a left hemisphere advantage in relational cognition and a right hemispheric superiority in judging absolute distances that is not supported by the animal data. Studies specifically addressing Kosslyn's hypotheses and bearing on the use of similar stimuli, procedures and methods between the species tested are needed in order to lead to firm conclusions about the existence of coordinate versus categorical processing systems in animals.

New methodology applied to bonnet macaques (Macaca radiata) to address some contradictory evidence on manual asymmetries in Old World monkeys

Seven bonnet macaques (Macaca radiata) with strong hand preferences in performing a computer-generated joystick task that required directing a cursor to contact a small stationary target on a monitor were given comparable experience with each hand on the task over a 5-week period. Hand use was randomly restricted to either only the left or only the right hand across trials by automatically inputting into a computer the unique identification numbers of microchips implanted in the forearms of each macaque. Subsequent presentation of a novel task requiring maintenance of contact between a cursor and a moving target revealed no performance difference between preferred and nonpreferred hands or between left and right hands on the basis of number of errors or time to complete the task. The findings suggest that the strong hand preference for these tasks does not derive from a performance advantage for the preferred hand.

Lateralization of visuospatial processing in the bottlenose dolphin (Tursiops truncatus)

Two adult female bottlenose dolphins were tested for cerebral asymmetries in the visuospatial domain. The animals learned under binocular conditions a three-choice spatial discrimination task with three hoops positioned along a line in the middle of the tank. During a correct trial the dolphins had to swim from a starting position at the tanks wall through one of the hoops, come back to the starting position, choose another hoop, swim back to start and finally swim through the third hoop. For such a trial to be correct, the animals had to swim through all three hoops in any sequence without omitting or re-using one of them. After reaching criterion binocularly, monocular trials (one eye covered with an adherent suction cup) were introduced where the dolphins carried out the same task alternatingly under left or right eye seeing conditions. For both animals, the right eye performance was clearly superior to that of the left eye. Binocular and right eye performances were similar. As a result of the complete decussation at the optic nerve, this right eye superiority suggests a left-hemispheric dominance for the processing of visuospatial information. This is a remarkable deviation from the usual right hemisphere advantage for these kind of tasks found in different species of mammals and birds.

Comparative assessment of distance processing and hemispheric specialization in humans and baboons (Papio papio)

This comparative study explored the ability to process distance and its lateralization in humans and baboons. Using a conditional matching-to-sample procedure in a divided-field format, subjects had to decide whether or not the distance between a line and a dot belonged to a short- or a long-distance category. Experiments 1, 2, and 4 demonstrated the ability of baboons to process and categorize distances. Moreover, humans showed better distance processing for right visual field/left hemisphere presentations than for left visual field/right hemisphere (LVF-RH) displays (Experiments 1-2). The same bias was found in baboons (Experiment 1), but in a weaker way. In Experiment 3, naive human individuals were tested and the difficulty of the discrimination was enhanced. There was a LVF-RH advantage which vanished with practice. Results are discussed by referring to theories (i.e., Kosslyn, 1987) of visuospatial processing for coordinate and categorical judgments.

Video-task acquisition in rhesus monkeys (Macaca mulatta) and chimpanzees (Pan troglodytes): a comparative analysis

This study describes video-task acquisition in two nonhuman primate species. The subjects were seven rhesus monkeys (Macaca mulatta) and seven chimpanzees (Pan troglodytes). All subjects were trained to manipulate a joystick which controlled a cursor displayed on a computer monitor. Two criterion levels were used: one based on conceptual knowledge of the task and one based on motor performance. Chimpanzees and rhesus monkeys attained criterion in a comparable number of trials using a conceptually based criterion. However, using a criterion based on motor performance, chimpanzees reached criterion significantly faster than rhesus monkeys. Analysis of error patterns and latency indicated that the rhesus monkeys had a larger asymmetry in response bias and were significantly slower in responding than the chimpanzees. The results are discussed in terms of the relation between object manipulation skills and video-task acquisition.

Eye movements in baboons performing a matching-to-sample task presented in a divided-field format

We examined eye saccades in a baboon solving a video-formatted matching-to-sample (MTS) task. In that task, the animal had to place a cursor by way of joystick manipulation within the boundaries of a fixation point (FP) displayed on a monitor. A sample stimulus was then flashed in either the left or right of FP. Immediately thereafter, two comparison forms were displayed and the animal had to select the comparison form matching the sample. A new video technique requiring no specific head or body constraints was employed to monitor eye movements. Expt. 1 indicated that the gaze was centered on FP during the fixation procedure. However, some goal-directed express saccades, with mean latencies of 100 ms, were observed during sample presentation. Expt. 2 used an overlap procedure in which FP remained visible during sample presentation. Latencies of express saccades increased by approximatively 20 ms. Expt. 3 showed in four baboons that the overlap procedure did not affect scores. It is concluded that the computerized MTS task is a valuable tool for the assessment of hemispheric lateralization in visual processing in intact primates, as long as the sample is not displayed longer than 120 ms.