Acquisition of self-control of a novel muscular activity with EMG and video feedback

To examine the acquisition of voluntary control of a novel muscular activity from the initial stage to the self-control stage, the m. auricularis posterior, which had generally degenerated and had nearly lost its function of drawing an auricle backward in the human body, was selected as a target muscle to be studied. One female undergraduate student who could not move her auricles intentionally was required to activate her left m. auricularis posterior and underwent rest, pretest, training, and posttest sessions once a day for five days. At the subject's request, the electromyograph (EMG) from her left m. auricularis posterior on an oscillograph was provided for her as the feedback signal on each training trial. The picture of her left ear on television was handled in the same way. The EMG measures indicated that the subject could learn to activate her left m. auricularis posterior differentially. The number of training trials on which the subject requested the feedback signals suggested that EMG feedback signal was more useful to her than the video and that the usefulness of the feedback signals varied as the training sessions advanced. It was also concluded from analysis of the self-report data that the acquisition process of self-control of a novel muscular activity could be divided into at least four stages.     

Prismatic displacement of vision induces transient changes in the timing of eye-hand coordination

Eye-hand coordination was investigated during a task of finger pointing toward visual targets viewed through wedge prisms. Hand and eye latencies and movement times were identical during the control condition and at the end of prism exposure. A temporal reorganization of eye and hand movements was observed during the course of adaptation. During the earlier stage of prism exposure, the time gap between the end of the eye saccade and the onset of hand movement was increased from a control time of 23 to 68 msec. This suggests that a time-consuming process occurred during the early prism-exposure period. The evolution of this time gap was correlated with the evolution of pointing errors during the early stage of prism exposure, in such a way that both measures increased at the onset of prism exposure and decreased almost back to control values within about 10 trials. However, spatial error was not entirely corrected, even late in prism exposure when the temporal organization of eye and hand had returned to baseline. These data suggest that two different adaptive mechanisms were at work: a rather short-term mechanism, involved in normal coordination of spatially aligned eye and hand systems, and a long-term mechanism, responsible for remapping spatially misaligned systems. The former mechanism can be strategically employed to quickly optimize accuracy in a situation involving misalignment, but completely adaptive behavior must await the slower-acting latter mechanism to achieve longterm spatial alignment.     

Perception of the Ponzo illusion by rhesus monkeys, chimpanzees, and humans: Similarity and difference in the three primate species

In Experiment 1, 3 rhesus monkeys and 1 chimpanzee were tested for their susceptibility to the Ponzo illusion. The subjects were first trained to report the length of the target bar presented at the center of the computer display by touching either of the two choice locations designated as “long” or “short.” When inverted-V context lines were superimposed on the target bar, the subjects tended to report “long” more often as the apex of these upward-converging lines approached the target bar. The perception of the Ponzo illusion was thus demonstrated. In Experiment 2, the same 3 rhesus monkeys and 2 new chimpanzees were tested using two types of context lines that provided different strengths of linear perspective. The subjects showed a bias similar to that found in Experiment 1, but there was no difference in the magnitude of the bias between the two types of context in either species. This failed to support the classic account for the Ponzo illusion, the perspective theory, raised by Gregory (1963). In Experiment 3, the magnitude of the illusion was compared between the inverted-V context and the context consisting of short vertical lines having the same gap as the former in the same 3 rhesus monkeys and 2 of the chimpanzees from the preceding experiments. While the chimpanzees showed the illusion for both types of stimuli, the monkeys showed no illusion for the latter. In Experiment 4, 6 humans were tested in a comparable procedure. As in the nonhuman primates, the illusion was unaffected by the strength of linear perspective. On the other hand, the humans showed considerably larger illusion for the context consisting of vertical lines than for contexts consisting of converging lines. Thus, there was a great species difference in the effect of the gap itself on the magnitude of the Ponzo illusion. Similarity found at first turned out to be no more than superficial. Possible sources of this species difference are discussed.     

Integration of visual and vestibulo-tactile inputs affecting apparent self-motion around the line of sight

We investigated the effects of visual and vestibulo-tactile inputs on perceived self-motion. Each of 23 subjects was exposed to an optical pattern rotating around the roll axis (i.e., line of sight) while the chair, in which the subject was placed, was rotated back and forth between +/-70 degrees (i.e., large rolling) or between +/-35 degrees (i.e., small rolling) from the gravitational vertical. Each subject judged perceived velocity of self-motion under each of 16 combinations of pattern velocity and chair velocity. The main results were the following: (1) The mean estimation increased with pattern velocity, and it also increased with chair velocity, (2) to attain a constant perceived velocity of self-motion, pattern velocity was traded for chair velocity, and for the large rolling of the chair, visual inputs were more effective than vestibulo-tactile inputs, whereas for the small rolling, the inverse was true; (3) analyses of multiple regression, when applied to the mean estimations, showed that for both rollings of the chair, the visual component dominated over the vestibulo-tactile component, but for the small rolling of the chair, the difference in effectiveness between the two components was attenuated. We discuss these findings in terms of visual-vestibular interaction.     

Are monkeys aesthetists? Rensch (1957) revisited

Three experiments assessed whether capuchin monkeys (Cebus apella) and squirrel monkeys (Saimiri sciureus) prefer regular and symmetrical visual patterns. Pictorial representations of faces were included in 1 stimulus set. When the monkeys could pick up and manipulate small cards bearing the stimuli, all preferences expressed by capuchins and most of those expressed by squirrel monkeys were for regular stimuli. Symmetry of the patterns was influential but not essential. Some preferences were also found for faces. When images of the patterns were presented on a touch screen, capuchins continued to express preferences especially for regular and symmetrical stimuli, but they showed some avoidance of faces. Squirrel monkeys responded less discriminatingly to the touch screen stimuli. The findings provide support for B. Rensch's (1957) claim that monkeys prefer visual stimuli that humans find aesthetically pleasing.     

What perceptual rules do capuchin monkeys (Cebus apella) follow in completing partly occluded figures?

Capuchin monkeys (Cebus apella) matched a variety of rodlike figures, distinguishable only by their central portions. The monkeys were then tested for perceptual completion rules by examining which comparison figures they would choose as matching the sample with the critical central portion occluded by a horizontal belt. In Experiment 1, the monkeys overwhelmingly chose a straight rod over disconnected rods and rods having irregular shapes at their center, irrespective of the presence-absence of common motion of visible parts of the samples. The monkeys chose a connected rod for relatable rods and disconnected rods for non-relatable ones in Experiment 2. In Experiments 3 and 4, some of the monkeys chose rods specified by the global regularity of the contour, whereas others did not. Experiment 5 showed that humans and capuchin monkeys basically follow similar perceptual rules in completing occluded contours, but the global regularity rule may be stronger in humans.     

Attention to combined attention in new world monkeys (Cebus apella, Saimiri sciureus)

Co-orientation by capuchin (Cebus apella) and squirrel (Saimiri sciureus) monkeys in response to familiar humans abruptly switching the direction of their visual attention was recorded. Co-orientation occurred more frequently overall in capuchins than squirrel monkeys. Capuchins showed a tendency to habituate within trials involving consecutive attention switches performed by 2 different people, whereas squirrel monkeys co-oriented more when the 2nd attention switch was by a 2nd actor. These results suggest variable attention-processing abilities in New World monkeys, including differences in summation of attention by others.     

Novel visual stimuli activate a population of neurons in the primate orbitofrontal cortex

Neurons were found in the rhesus macaque anterior orbitofrontal cortex that respond to novel but not to familiar visual stimuli. Some of these neurons responded to all novel stimuli, and others to only a subset (e.g., to novel faces). The neurons have no responses to familiar reward- or punishment-associated visual stimuli, nor to taste, olfactory or somatosensory inputs. The responses of the neurons typically habituated with repeated presentations of a novel stimulus, and five presentations each 1s was the median number for the response to reach half-maximal. The neurons did not respond to stimuli which had been novel and shown a few times on the previous day, indicating that the neurons were involved in long-term memory. The median latency of the neuronal responses was 120 ms. The median spontaneous firing rate was 1.3 spikes/s, and the median response to novel visual stimuli was 6.0 spikes/s. These findings indicate that the long-term memory for visual stimuli is information that is represented in a region of the primate anterior orbitofrontal cortex.     

Auditory-visual intermodal matching of small numerosities in 6-month-old infants

Recent studies have reported that preverbal infants are able to discriminate between numerosities of sets presented within a particular modality. There is still debate, however, over whether they are able to perform intermodal numerosity matching, i.e. to relate numerosities of sets presented with different sensory modalities. The present study investigated auditory-visual intermodal matching of small numerosities in infancy by using a violation-of-expectation paradigm. After being familiarized with events of a few objects impacting a surface successively, 6-month-old infants were alternatively presented with two and three tones while the movement of each object remained hidden behind an opaque screen. The screen was then removed to reveal either two or three objects. Results showed that the infants looked significantly longer at the numerically nonequivalent events (the three-tone/two-object and the two-tone/three-object events) than at the numerically equivalent events (the two-tone/two-object and the three-tone/three-object events) irrespective of the rate or duration of auditory tones presented. These findings suggest that infants are capable of performing intermodal matching of small numerosities and that they might possess abstract representations of numerosity beyond sensory modalities.