Discriminative whisking in the head-fixed rat: optoelectronic monitoring during tactile detection and discrimination tasks

We compared whisking movement patterns during acquisition of tactile detection and object discrimination under conditions in which (a) head movements are excluded and (b) exposure to tactile discriminanda is confined to the large, moveable vibrissae (macrovibrissae). We used optoelectronic instrumentation to track the movements of an individual whisker with high spatio-temporal resolution and a testing paradigm, which allowed us to dissociate performance on an “indicator” response (lever pressing) from the rat's “observing” responses (discriminative whisking). We analyzed the relation between discrimination performance and whisking movement patterns in order to clarify the process by which the indicator response comes under the stimulus control of information acquired by the rat's whisking behavior. Whisking patterns over the course of task acquisition differed with task demands. Acquisition of the Detection task was correlated with modulation of only one whisking movement parameter - total number of whisks emitted, and more whisking was seen on trials in which the discriminandum was absent. Discrimination between a sphere and cube differing in size and texture was correlated with a reduction in whisk duration and protraction amplitude and with a shift towards higher whisking frequencies. Our findings confirm previous reports that acquisition of tactile discriminations involves modulation by the animal of both the amount and the type of whisking. In contrast with a previous report (Brecht et al., 1997), they indicate that rats can solve tactile object detection and discrimination tasks (a) using only the large, motile mystacial vibrissae (macrovibrissae) and (b) without engaging in head movements.We conclude that the functional contribution of the macrovibrissae will vary with the nature of the task and the conditions of testing.     

Is torso soft tissue motion really an artefact within breast biomechanics research?

For rigid body POSE estimation, any relative movement of the tracking markers on a segment is often referred to as an artefact; however this may be an important part of the signal within breast biomechanics. This study aimed to quantify differences in breast range of motion when calculated relative to the torso segment using either direct or segment optimised POSE estimation algorithms. Markers on the torso and right nipple were tracked using infrared cameras (200 Hz) during five running gait cycles in three breast support conditions (no bra, everyday bra and sports bra). Multiplanar breast range of motion was calculated relative to the torso segment using two POSE estimation algorithms. First, the torso segment was defined using direct POSE estimation (direct). Second, while standing stationary in the anatomical position; the positional data of the torso markers were used to construct the torso using segment optimised POSE estimation (optimised). The torso segment length defined using direct POSE estimation changed significantly by 3.4 cm compared to that of the segment optimisation POSE estimation in the no bra condition. Subsequently, superioinferior breast range of motion was significantly greater (p<0.017) when calculated using direct POSE estimation, within each of the three breast support conditions. Segment optimisation POSE estimation is recommended to minimise any differences in breast motion associated with intra segment deformation between physical activity types. However, either algorithm is recommended when evaluating different breast support garments, as a correctly fitted bra does not cause the torso markers to move relative to each other.     

Selection for local adaptation in a plant breeding programme

Summary Regressions of yields of cultivars upon means of sets of cultivars over diverse environments are often used as measures of stability/adaptability. Prolonged selection for performance in environments of high yield potential has generally led to unconscious selection for high regressions. If adaptation to poor environments is required (as it often is in Third World agriculture), common sense suggests that low regressions could be exploited for the purpose. Simulations show that systematic selection in the poor environment is required, not merely trials of potential cultivars after selection in a good environment. In effect, systematic exploitation of a GE interactions effect is proposed. The effects are large enough to reduce correlated responses in different environments to zero. Orderly experimental studies are needed but not available. What information there is does not disagree with the theory developed here.     

John Maynard Smith and the natural philosophy of␣adaptation

One of the most remarkable aspects of John Maynard Smith’s work was the fact that he devoted time both to doing science and to reflecting philosophically upon its methods and concepts. In this paper I offer a philosophical analysis of Maynard Smith’s approach to modelling phenotypic evolution in relation to three main themes. The first concerns the type of scientific understanding that ESS and optimality models give us. The second concerns the causal–historical aspect of stability analyses of adaptation. The third concerns the concept of evolutionary stability itself. Taken together, these three themes comprise what I call the natural philosophy of adaptation.