Matthew D. M. Pawley

General anesthesia alters time perception by phase shifting the circadian clock

Following general anesthesia, people are often confused about the time of day and experience sleep disruption and fatigue. It has been hypothesized that these symptoms may be caused by general anesthesia affecting the circadian clock. The circadian clock is fundamental to our well-being because it regulates almost all aspects of our daily biochemistry, physiology, and behavior. Here, we investigated the effects of the most common general anesthetic, isoflurane, on time perception and the circadian clock using the honeybee (Apis mellifera) as a model. A 6-h daytime anesthetic systematically altered the time-compensated sun compass orientation of the bees, with a mean anticlockwise shift in vanishing bearing of 87° in the Southern Hemisphere and a clockwise shift in flight direction of 58° in the Northern Hemisphere. Using the same 6-h anesthetic treatment, time-trained bees showed a delay in the start of foraging of 3.3 h, and whole-hive locomotor-activity rhythms were delayed by an average of 4.3 h. We show that these effects are all attributable to a phase delay in the core molecular clockwork. mRNA oscillations of the central clock genes cryptochrome-m and period were delayed by 4.9 and 4.3 h, respectively. However, this effect is dependent on the time of day of administration, as is common for clock effects, and nighttime anesthesia did not shift the clock. Taken together, our results suggest that general anesthesia during the day causes a persistent and marked shift of the clock effectively inducing “jet lag” and causing impaired time perception. Managing this effect in humans is likely to help expedite postoperative recovery.

Way-finding in displaced clock-shifted bees proves bees use a cognitive map

Significance The question of the computational capacities of the brains of widely separated genera of animals is of interest to behavioral biologists, comparative psychologists, computational neuroscientists, philosophers of mind, and—we believe—much of the scientific community. Half a century ago, the claim that any nonhuman animal had a cognitive map was deeply controversial. If true, it greatly favored a computational theory of mind, as opposed to an antirepresentational behaviorist theory. Now that it is well established by behavioral and neurobiological evidence that rodents have a metric cognitive map, the question of whether insects do is a frontier question, the answer to which has broad implications in several disciplines. Mammals navigate by means of a metric cognitive map. Insects, most notably bees and ants, are also impressive navigators. The question whether they, too, have a metric cognitive map is important to cognitive science and neuroscience. Experimentally captured and displaced bees often depart from the release site in the compass direction they were bent on before their capture, even though this no longer heads them toward their goal. When they discover their error, however, the bees set off more or less directly toward their goal. This ability to orient toward a goal from an arbitrary point in the familiar environment is evidence that they have an integrated metric map of the experienced environment. We report a test of an alternative hypothesis, which is that all the bees have in memory is a collection of snapshots that enable them to recognize different landmarks and, associated with each such snapshot, a sun-compass–referenced home vector derived from dead reckoning done before and after previous visits to the landmark. We show that a large shift in the sun-compass rapidly induced by general anesthesia does not alter the accuracy or speed of the homeward-oriented flight made after the bees discover the error in their initial postrelease flight. This result rules out the sun-referenced home-vector hypothesis, further strengthening the now extensive evidence for a metric cognitive map in bees.

Behavioural Effects of Tourism on Oceanic Common Dolphins, Delphinus sp., in New Zealand: The Effects of Markov Analysis Variations and Current Tour Operator Compliance with Regulations

Common dolphins, Delphinus sp., are one of the marine mammal species tourism operations in New Zealand focus on. While effects of cetacean-watching activities have previously been examined in coastal regions in New Zealand, this study is the first to investigate effects of commercial tourism and recreational vessels on common dolphins in an open oceanic habitat. Observations from both an independent research vessel and aboard commercial tour vessels operating off the central and east coast Bay of Plenty, North Island, New Zealand were used to assess dolphin behaviour and record the level of compliance by permitted commercial tour operators and private recreational vessels with New Zealand regulations. Dolphin behaviour was assessed using two different approaches to Markov chain analysis in order to examine variation of responses of dolphins to vessels. Results showed that, regardless of the variance in Markov methods, dolphin foraging behaviour was significantly altered by boat interactions. Dolphins spent less time foraging during interactions and took significantly longer to return to foraging once disrupted by vessel presence. This research raises concerns about the potential disruption to feeding, a biologically critical behaviour. This may be particularly important in an open oceanic habitat, where prey resources are typically widely dispersed and unpredictable in abundance. Furthermore, because tourism in this region focuses on common dolphins transiting between adjacent coastal locations, the potential for cumulative effects could exacerbate the local effects demonstrated in this study. While the overall level of compliance by commercial operators was relatively high, non-compliance to the regulations was observed with time restriction, number or speed of vessels interacting with dolphins not being respected. Additionally, prohibited swimming with calves did occur. The effects shown in this study should be carefully considered within conservation management plans, in order to reduce the risk of detrimental effects on common dolphins within the region.

Circadian-Related Sleep Disorders and Sleep Medication Use in the New Zealand Blind Population: An Observational Prevalence Survey

Study Objectives To determine the prevalence of self-reported circadian-related sleep disorders, sleep medication and melatonin use in the New Zealand blind population. Design A telephone survey incorporating 62 questions on sleep habits and medication together with validated questionnaires on sleep quality, chronotype and seasonality. Participants Participants were grouped into: (i) 157 with reduced conscious perception of light (RLP); (ii) 156 visually impaired with no reduction in light perception (LP) matched for age, sex and socioeconomic status, and (iii) 156 matched fully-sighted controls (FS). Sleep Habits and Disturbances The incidence of sleep disorders, daytime somnolence, insomnia and sleep timing problems was significantly higher in RLP and LP compared to the FS controls (p<0.001). The RLP group had the highest incidence (55%) of sleep timing problems, and 26% showed drifting sleep patterns (vs. 4% FS). Odds ratios for unconventional sleep timing were 2.41 (RLP) and 1.63 (LP) compared to FS controls. For drifting sleep patterns, they were 7.3 (RLP) and 6.0 (LP). Medication Use Zopiclone was the most frequently prescribed sleep medication. Melatonin was used by only 4% in the RLP group and 2% in the LP group. Conclusions Extrapolations from the current study suggest that 3,000 blind and visually impaired New Zealanders may suffer from circadian-related sleep problems, and that of these, fewer than 15% have been prescribed melatonin. This may represent a therapeutic gap in the treatment of circadian-related sleep disorders in New Zealand, findings that may generalize to other countries.

Reply to Cheung et al.: The cognitive map hypothesis remains the best interpretation of the data in honeybee navigation

Cheung et al. (1) criticize two points of our study, both of which are unfounded. The first is that general anesthesia is not shifting the clock controlling sun compass orientation in bees. This is clearly wrong. We show that sun compass orientation and food anticipatory behavior are systematically shifted by anesthesia. This effect results from anesthesia shifting the underlying molecular circadian clock of the bee (2).

The effect of time of day on the duration of neuromuscular blockade elicited by rocuronium

In a prospective, observational trial, we investigated the influence of time of day on the duration of neuromuscular blockade (NMB) elicited by rocuronium. Forty‐nine patients scheduled for surgery between 08:00 and 02:00 were enrolled after giving written informed consent. Time to neuromuscular recovery was measured following three doses: (1) a fat‐free‐mass (FFM) related induction dose (0.6 mg.kg−1: n = 47); (2) a maintenance dose (20% of the induction dose: n = 42); and (3) a standard 10‐mg dose (n = 35). The extent of NMB was dependent on the time of administration (p = 0.038 General Linear Model Analysis). The maximum effect of 50 min (95% CI 41–59 min) was elicited between 08:00 and 11:00 and the minimum duration of 29 min (95% CI 23–35 min) between 14:00 and 17:00 (p = 0.005). A similar pattern was observed for the maintenance dose. The duration of action of rocuronium is influenced by time of day and this effect is of potential clinical significance and practical relevance to research.

Validating the use of wrist-level light monitoring for in-hospital circadian studies.

This clinical methods comparison study describes the difference between light levels measured at the wrist (Actiwatch-L) and at the eye (Daysimeter) in a postoperative in-patient population. The mean difference between the two devices was less than 10 lux at light levels less than 5000 lux. Agreement between the devices was found to decrease as eye-level light exposure increased. Measurements at eye level of 5000 lux or more corresponded to a difference between the devices of greater than 100 lux. Agreement between the eye- and wrist-level light measurements also appears to be influenced by time of day. During the day, the measurement differences were on average 50 lux higher at eye level, whereas at night they were on average 50 lux lower. Although the wrist-level monitor was found to underestimate light exposure at higher light levels, it was well tolerated by participants in the clinical setting. In contrast, the eye-level monitor was cumbersome and uncomfortable for the patients to wear. This study provides light-exposure data on patients in real conditions in the clinical environment. The results show that wrist-level monitoring provides an adequate estimate of light exposure for in-hospital circadian studies. (Author correspondence: g.warman@auckland.ac.nz)

Residency and movement patterns of an apex predatory shark (Galeocerdo cuvier) at the Galapagos Marine Reserve

The potential effectiveness of marine protected areas (MPAs) as a conservation tool for large sharks has been questioned due to the limited spatial extent of most MPAs in contrast to the complex life history and high mobility of many sharks. Here we evaluated the movement dynamics of a highly migratory apex predatory shark (tiger shark Galeocerdo cuvier) at the Galapagos Marine Reserve (GMR). Using data from satellite tracking passive acoustic telemetry, and stereo baited remote underwater video, we estimated residency, activity spaces, site fidelity, distributional abundances and migration patterns from the GMR and in relation to nesting beaches of green sea turtles (Chelonia mydas), a seasonally abundant and predictable prey source for large tiger sharks. Tiger sharks exhibited a high degree of philopatry, with 93% of the total satellite-tracked time across all individuals occurring within the GMR. Large sharks (> 200 cm TL) concentrated their movements in front of the two most important green sea turtle-nesting beaches in the GMR, visiting them on a daily basis during nocturnal hours. In contrast, small sharks (< 200 cm TL) rarely visited turtle-nesting areas and displayed diurnal presence at a third location where only immature sharks were found. Small and some large individuals remained in the three study areas even outside of the turtle-nesting season. Only two sharks were satellite-tracked outside of the GMR, and following long-distance migrations, both individuals returned to turtle-nesting beaches at the subsequent turtle-nesting season. The spatial patterns of residency and site fidelity of tiger sharks suggest that the presence of a predictable source of prey and suitable habitats might reduce the spatial extent of this large shark that is highly migratory in other parts of its range. This highly philopatric behaviour enhances the potential effectiveness of the GMR for their protection.

Dolphin fin pose correction using ICP in application to photo-identification

Photo-identification of dolphin individuals is a commonly used technique in ecological sciences to monitor state and health of individuals, as well as to study the social structure and distribution of a population. Uniqueness of some forms of damage sustained by the trailing edge of the dorsal fin throughout an individuals life allows it to be used to identify the individual. Traditional photo-identification involves a laborious manual process of matching each dolphin fin photograph captured in the field to a catalogue of known individuals. A number of efforts have been made in the past to automate this process through the use of digital image processing; however, none of them correct for the different fin orientations (3D pose) prior to performing matching in a robust way. This paper provides an overview of these existing methods and offers a novel approach of utilising the iterative closest point (ICP) algorithm for performing the projective registration of two fin shapes and shows that this proposed method is robust to segmentation noise, partial occlusions and new nicks and notches appearing since last encounter.

Shrinkage estimates of covariance matrices to improve the performance of multivariate cumulative sum control charts

Abstract Multivariate cumulative sum control charts require knowledge of the in-control process covariance parameters. Here, we show that the performance of the multivariate cumulative sum control charts for individual-observation monitoring is affected by the estimation of parameters unless the Phase I sample size is large. When only a small Phase I sample size is available, we propose the use of a shrinkage estimate. The average run length performance of multivariate cumulative sum control charts obtained using the shrinkage estimate is superior to the other methods examined in this study. The improved performance of the control charts using the shrinkage estimate is also demonstrated via an illustrative case study of Bimetal data, in which measurements of four properties of bimetal brass and steel thermostats are monitored, and a shift in the multivariate centroid is detected earlier using the shrinkage-based method.