The neurophysiological validation of the hyperpolarization theory of internal inhibition

A Bayesian optimal escape model reveals bird species differ in their capacity to habituate to humans

The capacity to habituate to, or tolerate, the close proximity of humans varies among wildlife species and may mediate population and species viability. Some species readily habituate to human proximity while others remain sensitive. These differences are important for predicting human impact on wildlife, but can be difficult to quantify given wildlife responses are highly idiosyncratic and are often context dependent. A general method for assimilating multiple sources of information and variation in individual responses is needed to extract meaningful descriptors of population- and species-level behavior. We apply a previously verified Bayesian optimal escape model to quantify differences in the perceived risk of seven species of waterbird, and generate a metric for species-specific sensitivity by estimating the relative change in risk perception of each species across an environmental gradient from low to high prevailing human activity level. We found that, in general, birds are the least habituated (evidently perceived the highest level of risk from humans) in sites with low human activity and the most habituated (evidently perceived lower levels of risk from humans) in sites with high human activity. Species varied in the degree of these differences, with some insensitive to human activity level, while others were highly sensitive. Aside from improving our ability to study the habituation of wild populations, this method for quantifying risk perception at population and species scales has broad applications in the management and monitoring of wildlife, and may aid in environmental impact assessments and identifying populations/species susceptible to disturbance.

The Effects of Agonists of Ionotropic GABAAand Metabotropic GABABReceptors on Learning

The research described here investigates the role played by inhibitory processes in the discriminations made by the nervous system of humans and animals between familiar and unfamiliar and significant and nonsignificant events. This research compared the effects of two inhibitory mediators of gamma-aminobutyric acid (GABA): 1) phenibut, a nonselective agonist of ionotropic GABAAand metabotropic GABABreceptors and 2) gaboxadol a selective agonist of ionotropic GABAAreceptors on the process of developing active defensive and inhibitory conditioned reflexes in alert non-immobilized rabbits. It was found that phenibut, but not gaboxadol, accelerates the development of defensive reflexes at an early stage of conditioning. Both phenibut and gaboxadol facilitate the development of conditioned inhibition, but the effect of gaboxadol occurs at later stages of conditioning and is less stable than that of phenibut. The earlier and more stable effects of phenibut, as compared to gaboxadol, on storage in memory of the inhibitory significance of a stimulus may occur because GABABreceptors play the dominant role in the development of internal inhibition during an early stage of conditioning. On the other hand this may occur because the participation of both GABAAand GABABreceptors are essential to the process. We discuss the polyfunctionality of GABA receptors as a function of their structure and the positions of the relevant neurons in the brain as this factor can affect regulation of various types of psychological processes.

Does direct human eye contact function as a warning cue for domestic sheep (Ovis aries)?

Direct eye contact may function as a warning cue during interspecific interactions, and human staring has been shown to influence the behavior of many species. The authors used an arena test to assess whether human staring altered the behavior of domestic sheep (Ovis aries) compared with no human eye contact. Sheep glanced at the staring human's face more often in the first 2 min of the test, indicating that they perceived a difference between the human stimuli. Staring also elicited more locomotor activity and urination than averted gaze. However, there were no differences in fear-related behaviors, suggesting that a staring human did not represent a greater immediate threat than a nonwatching human. These results imply that human staring is a warning cue for domestic sheep, but no more. Without further reinforcement, sheep quickly habituated to the warning cue.