Gaze following and joint attention in rhesus monkeys (Macaca mulatta).

Gaze and attention direction provide important sources of social information for primates. Behavioral studies show that chimpanzees spontaneously follow human gaze direction. By contrast, non-ape species such as macaques fail to follow gaze cues. The authors investigated the reactions of rhesus macaques (Macaca mulatta) to attention cues of conspecifics. Two subjects were presented with videotaped images of a stimulus monkey with its attention directed to 1 of 2 identical objects. Analysis of eye movements revealed that both subjects inspected the target (object or position attended by the stimulus monkey) more often than the distractor (nonattended object or position). These results provide evidence that rhesus monkeys follow gaze and use the attention cues of other monkeys to orient their own attention to objects.

Effect of pairing red nucleus and motor thalamic lesions on reaching toward moving targets in cats.

The small effects of bilateral lesions of motor thalamus on motor control and the transient deficits induced by bilateral kainic red nucleus (RN) lesions have been explained by a parallel competitive role of the cortico- and rubro-spinal pathways. Either pathway can take over motor control if the other is damaged. In this study the effect of bilateral and simultaneous lesions of both RN and motor thalamus was analyzed on cats overtrained to reach toward a moving target. After lesion, accuracy was impaired, movement onset was delayed, and movement execution was perturbed. However, postoperative retraining led to full recovery of the preoperative accuracy level although movement latency remained higher. The relative mildness of the long-lasting deficit after lesioning 2 main motor brain structures underlines the robustness of overlearned movements and widens the idea of parallelism in the motor system to other (subcortical?) pathways.

Effect of practice on paw preference in a reaching task in cats.

Paw preference and performance were analyzed in twelve male adult cats during early and late practice of a complex visuo-motor reaching task towards a moving target. A strong bias towards left paw use was seen early in training: 80.7% of the trials being performed with the left paw, and left pawed cats (n = 11) significantly outnumbered right pawed cats (n = 1). After practice, a shift was observed towards right paw use, in that, overall, the proportion of trials executed using the left paw fell to 71.4%. Moreover two of the left pawed cats modified strongly their preference: one shifted to exclusive use of the right paw while the other one became ambidextrous. In non exclusive cats the comparison of visuo-motor scores for left and right paws during late practice showed that the usage of the paw which is both faster and more accurate had increased during training whether or not that paw was initially the preferred one. Furthermore, for cats where no systematic performance advantage was seen (i.e. one paw was faster, the other one more accurate) there was a shift towards ambidextry. As a conclusion, the results confirm a bias towards left paw use in cats performing a complex reaching task, and show that this bias is weakened by practice. The left hemisphere could take more importance when the new visuo-motor activity becomes progressively a well routinized one.

Laterality in cats: paw preference and performance in a visuomotor activity.

Laterality in paw use was investigated over a period of 6 years in 44 domestic cats trained to perform a reaching movement toward a moving spot of light. Both paw preference and paw performance were recorded. At a 50 percent criterion, no significant paw preference was found at the level of the group. When a 90 percent criterion was considered, 23 subjects had a significant preference for one paw. Among these strongly lateralized animals, there were more left- (N = 17) than right-pawed (N = 6) cats. The analysis of visuo-motor performances included reaction time, movement time, and reaching accuracy. Lateralized cats had a faster reaction time than nonlateralized cats. The more-used paw had a shorter reaction time, a shorter movement time, and was also more accurate than the less-used paw. Thus, the findings demonstrate a functional advantage of being lateralized. Moreover, the results confirm the existence of an asymmetry of paw preference in cats and show a consistent relation between paw preference and performance.

Derivation of surface macroroughness parameters of a random rough surface from an optical interferometric measurement.

A new technique for the measurement of surface roughness based on the intensity fluctuations of laser light backscattered from a moving surface has been introduced. Using a statistical model describing surface macroroughness, the possibility of inversion of optically measured data to geometrical surface profile parameters is investigated.