Biomedical subjects
Publications and source records attributed to Cory T Miller.
Theories about the evolutionary path that led to the neuronal network underlying human language have long generated much heat without light. Using PET imaging, a recent study suggests that monkeys share a circuit for vocal perception with humans, adding some empirical data to the debate.
A fundamental issue in neuroscience pertains to how different cortical systems interact to generate behavior. One of the most direct ways to address this issue is to investigate how sensory information is encoded and used to produce a motor response. Antiphonal calling is a natural vocal behavior that involves individuals producing their species-specific long distance vocalization in response to hearing the same call and engages both the auditory and motor systems, as well as the cognitive neural systems involved in decision making and categorization. Here we present results from a series of behavioral experiments investigating the auditory-vocal interactions during antiphonal calling in the common marmoset (Callithrix jacchus). We manipulated sensory input by placing subjects in different social contexts and found that the auditory input had a significant effect on call timing and propensity to call. Playback experiments tested the significance of the timing of vocal production in antiphonal calling and showed that a short latency between antiphonal calls was necessary to maintain reciprocal vocal interactions. Overall, this study shows that sensory-motor interactions can be experimentally induced and manipulated in a natural primate vocal behavior. Antiphonal calling represents a promising model system to examine these issues in non-human primates at both the behavioral and neural levels.
Several plumage types are found in feral pigeons (Columba livia), but one type imparts a clear survival advantage during attacks by the swiftest of all predators--the peregrine falcon (Falco peregrinus). Here we use quantitative field observations and experiments to demonstrate both the selective nature of the falcon's choice of prey and the effect of plumage coloration on the survival of feral pigeons. This plumage colour is an independently heritable trait that is likely to be an antipredator adaptation against high-speed attacks in open air space.
Few studies have examined whether non-human tool-users understand the properties that are relevant for a tool's function. We tested cotton-top tamarins (Saguinus oedipus) and rhesus macaques (Macaca mulatta) on an expectancy violation procedure designed to assess whether these species make distinctions between the functionally relevant and irrelevant features of a tool. Subjects watched an experimenter use a tool to push a grape down a ramp, and then were presented with different displays in which the features of the original tool (shape, color, orientation) were selectively varied. Results indicated that both species looked longer when a newly shaped stick acted on the grape than when a newly colored stick performed the same action, suggesting that both species perceive shape as a more salient transformation than color. In contrast, tamarins, but not rhesus, attended to changes in the tool's orientation. We propose that some non-human primates begin with a predisposition to attend to a tool's shape and, with sufficient experience, develop a more sophisticated understanding of the features that are functionally relevant to tools.
Vocal production can be highly deterministic, such that once the central nervous system generates a signal to call, the vocalization is emitted immune to external events. Conversely, vocal production can be modulated by auditory feedback such that interference or disruption can cause an individual to stop calling or, if it continues to call, for the acoustic morphology of the signal to change. To explore which of these models best accounts for the control of vocal production in non-human primates, we adapted an interruption technique originally developed for songbirds for use with a New World monkey species, the cotton-top tamarin (Saguinus oedipus). Results from a pilot experiment indicated that an auditory stimulus (white noise) was more effective than a visual stimulus (strobe light) at interrupting the tamarin's species-typical 'combination long call (CLC)'. Data from a second experiment showed that although the duration of the auditory stimulus did not affect the proportion of interruptions that occurred, a 1000 ms white noise stimulus perturbed the temporal structure of the CLC to a greater extent than did a 250 ms white noise stimulus. Furthermore, when call production was interrupted, tamarins stopped vocalizing after the completion of a syllable, suggesting that the syllable represents a unit of organization within the call. Overall, these results provide evidence that tamarins can modify their vocal output based on external events, but the degree of vocal control is significantly less than in oscine songbirds.
Studies of hand use in nonhuman primates suggest that several species exhibit hand preferences for a variety of tasks. The majority of studies, however, focus on the lateralized hand use of captive nonhuman primate populations. Although captive settings offer a more controlled environment for assessing hand preferences, studies of wild populations provide important insights into how handedness is affected by natural environmental conditions and thus potential insights into the evolution of handedness. To investigate handedness in a population of wild nonhuman primates, we studied patterns of lateralized hand use during feeding in four simakobu monkeys (Simias concolor), an arboreal species inhabiting the Mentawai Islands, Indonesia. Our data show that individual variation in hand preferences for feeding existed among our study animals. In addition, each simakobu expressed a significant hand preference for supporting itself on a branch during feeding, an uncoordinated bimanual task. This bias was most prevalent when the branch used for support was a main branch rather than a terminal branch. When both hands were employed in a coordinated bimanual feeding activity (bimanual manipulation), only two subjects showed a significant bias for feeding. Our data suggest that these individuals are more likely to express significant hand preferences when feeding from stable, rather than precarious, positions within the canopy.