What do dogs know about hidden objects?

Previous research has found that dogs will search accurately for an invisibly displaced object when the task is simplified and contextual ambiguity is eliminated [Doré, F.Y., Fiset, S., Goulet, S., Dumas, M.-C., Gagnon, S., 1996. Search behavior in cats and dogs: interspecific differences in working memory and spatial cognition. Animal Learning & Behavior 24, 142-149; Miller, H., Gipson, C., Vaughan, A., Rayburn-Reeves, R., Zentall, T.R., 2009. Object permanence in dogs: invisible displacement in a rotation task. Psychonomic Bulletin & Review 16 (1), 150-155]. For example, when an object is placed inside an occluder, one of which was attached to each end of a beam that could be rotated 90°, dogs search inside of the appropriate occluder. The current research confirmed this finding and tested the possibility that the dogs were using a perceptual/conditioning mechanism (i.e., their gaze was drawn to the occluder as the object was placed inside and they continued looking at it as it rotated). The test was done by introducing a delay between the displacement of the object and the initiation of the dogs’ search. In Experiment 1, during the delay, a barrier was placed between the dog and the apparatus. In Experiment 2, the lights were turned off during the delay. The search accuracy for some dogs was strongly affected by the delay, however, search accuracy for other dogs was not affected. These results suggest that although a perceptual/conditioning mechanism may be involved for some dogs, it cannot account for the performance of others. It is likely that these other dogs showed true object permanence.     

Representing occluded objects in the human infant brain

One of the most striking phenomena in cognitive development has been the apparent failure of infants to show 'object permanence' in manual reaching tasks although they show evidence for representing hidden objects in studies measuring looking times. We report a neural correlate of object permanence in six-month-old infants: a burst of gamma-band EEG activity over the temporal lobe that occurs during an occlusion event and when an object is expected to appear from behind an occluder. We interpret this burst as being related to the infants' mental representation of the occluded object.     

Spatial rotations and transpositions in orangutans (<Emphasis Type="Italic">Pongo pygmaeus</Emphasis>) and chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

This study investigated the ability of three chimpanzees and three orangutans to track the position of a reward after a series of displacements. The reward was placed under one of two opaque containers resting on a platform. Experiment 1 investigated rotational displacements in which the platform was rotated 0°, 180°, or 360°. Experiment 2 investigated transpositional displacements in which the platform remained stationary while the containers either remained stationary, or swapped their positions (in a one- two- or three-step sequence). In both experiments, the initial position of the reward was indicated either by directly showing the reward under the containers, or by placing a landmark, which had been previously associated with the reward, on top of the baited container. Subjects successfully tracked the reward through rotations and transpositions when they had seen it, but their performance substantially deteriorated when the landmark indicated the reward's initial position, even though subjects successfully used the landmark to find the reward in the absence of displacements. This decrease was especially pronounced in rotational displacements. A language-trained orangutan outperformed all the other apes and solved all problems.     

Techniques of trilobite exuviation

Examples of the trilobites Toxochasmops extensus (Boeck, 1838), Asaphiscus wheeleri Meek, 1874, Encrinurus mitchelli Foerste, 1888, Ogygopsis klotzi (Rominger, 1887), Paradoxides davidis Salter, 1863 and Oryctocephalus spp. which are interpreted as exuvial configurations, are described. Four specimens of Toxochasmops extensus arc known in which the pygidium rests either directly behind the eephalon, or with only three intervening thoracic segments. It is considered that during exuviation the old pygidium became wedged behind the cephalon. This facilitated its removal. An ecdysial configuration of Asaphiscus wheeleri is described which possesses inverted and partially rotated free cheeks. In addition, part of the thorax of the specimen is wedged obliquely behind the cephalon. This is considered to have aided withdrawal of the trilobite from its old exoskeleton. Two specimens of Encrinurus mitchelli are described which possess free cheeks inverted beneath the cranidium by lateral rotation, in a manner similar to that of A. wheeleri. Three examples of Ogygopsis klotzi are described, one a failed exuvia and two in which the free cheeks were inverted and rotated through 180° with respect to their original position and came to rest beneath the thorax. An identical exuvia of Paradoxides davidis trapezopyge is also described. Two specimens of Oryctocephalus exhibiting two different arrangements of inverted free cheeks are recorded. Possible mechanisms for each of these free cheek inversions are proposed.     

Two essential processes in the formation of a dorsal axis during gastrulation ofCynops embryo

The isolated upper marginal zone from the initial stage ofCynops gastrulation is not yet determined to form the dorsal axis mesoderm: notochord and muscle. In this experiment, we will indicate where the dorsal mesoderm-inducing activity is localized in the very early gastrula, and what is an important event for specification of the dorsal axis mesoderm during gastrulation. Recombination experiments showed that dorsal mesoderm-inducing activity was localized definitively in the endodermal epithelium (EE) of the lower marginal zone, with a dorso-ventral gradient; and the EE itself differentiated into endodermal tissues, mainly pharyngeal endoderm. Nevertheless, when dorsal EE alone was transplanted into the ventral region, a secondary axis with dorsal mesoderm was barely formed. However, when dorsal EE was transplanted with the bottle cells which by themselves were incapable of mesoderm induction, a second axis with well-developed dorsal mesoderm was observed. When the animal half with the lower marginal zone was rotated 180° and recombined with the vegetal half, most of the rotated embryos formed only one dorsal axis at the primary blastopore side. The present results suggest that there are at least two essential processes in dorsal axis formation: mesoderm induction of the upper marginal zone by endodermal epithelium of the lower marginal zone, and dorsalization of the upper dorsal marginal zone evoked during involution.     

Mirror agnosia.

Normal people rarely confuse the mirror image of an object with a real object so long as they realize they are looking into a mirror. We report a new neurological sign, ''mirror agnosia'', following right parietal lesions in which this ability is severely compromised. We studied four right hemisphere stroke patients who had left visual field ''neglect''. i.e. they were indifferent to objects in their left visual field even though they were not blind. We then placed a vertical parasagittal mirror on each patients'' right so that they could clearly see the reflection of objects placed in the (neglected) visual field. When shown a candy or pen on their left, the patients kept banging their hand into the mirror or groped behind it attempting to grab the reflection; they did not reach for the real object on the left, even though they were mentally quite lucid and knew they were looking into a mirror. Remarkably, all four patients kept complaining that the object was ''in the mirror'', ''outside my reach'' or ''behind the mirror''. Thus, even the patients'' ability to make simple logical inferences about mirrors has been selectively warped to accommodate the strange new sensory world that they now inhabit. The finding may have implications for understanding how the brain creates representations of mirror reflections.     

Funktionsmorphologie eines arthropodengelenks mit extrem gro ßem aktionswinkel das femoro-tibial-gelenk von Gerris najas (DeG.) (inseeta,heteroptera)

Summary The femoro-tibial joint of the middle leg of Gerris najas is a single-axis hinge with an effective angle of 180°. Morphology and kinematics of this joint are described. Short sclerites are inserted between the tibia and the tendon-like apodemes of its flexor and extensor muscles. Flexible at both ends, the sclerites extend the angle of leverage by 120° in the case of the extensor tibiae and by 60° in the case of the flexor tibiae. The effective lever length was determined quantitatively for the entire 180° (see Fig. 6).     

Intuitive physical reasoning about occluded objects by inexperienced chicks

Questions concerning the role of nature and nurture in higher cognition appear to be intractable if one restricts one's attention to development in humans. However, in other domains, such as sensory development, much information has been gained from controlled rearing studies with animals. Here, we used a similar experimental strategy to investigate intuitive reasoning about occluded objects. Newborn domestic chicks (Gallus gallus) were reared singly with a small object that became their social partner. They were then accustomed to rejoin such an imprinting object when it was made to move and disappear behind either one of two identical opaque screens. After disappearance of the imprinting object, chicks were faced with two screens of different slants, or of different height or different width, which may or may not have been compatible with the presence of the imprinting object hidden beneath/behind them. Chicks consistently chose the screen of slant/height/width compatible with the presence of the object beneath/behind it. Preventing chicks from touching and pecking at the imprinting object before testing did not affect the results, suggesting that intuitive reasoning about physical objects is largely independent of specific experience of interaction with objects and of objects' occluding events.     

How the two eyes add together: monocular properties of the visually guided orientation behaviour of flies

In this account fixation and the torque response to a transient moving stripe of flying femaleMusca domestica with monocular sight was tested. This was made by either covering one eye of the fly with opaque paint or by placing a screen in front of one side of the fly's visual field. A stripe was moved with constant speed once around the fly clockwise and, after a pause, counterclockwise. The torque response of the fly was measured during the motion of the stripe and shortly beforehand. The results demonstrated that the monocular torque response to progressive (from front to back) motion and regressive (from back to front) motion essentially do not differ from the binocular response, except for the region of bionocular overlap. The beginning of the response of a fly with monocular vision to progressive motion is 11 ° (on average) before the direction of flight (0°), which means that the maximal functional binocular overlap of femaleMusca domestica is stretched at least 15° to each side (3.1). In addition, the shape of the monocular torque response to a progressively moving stripe was determined (see Figs. 5Ia and 5IIb). In other experiments similar to the ones described above, a screen was placed on one side of the fly's visual field or then on the other, (instead of covering one eye) and the torque response to the moving stripe was measured. Using this method, a delay response of 90 ms was measured. We suggest that this is the delay of the direction-sensitive component of the torque response, and therefore an additional argument for the existence of two components for the optomotor torque response. Flies with a covered eye or with a screen placed in front of one side of the visual field were able to fixate a single narrow long black stripe. This, however, was possible only when an additional offset signal was added, in order to give the stripe a constant velocity component. As a result there was a shift of the fixation towards the unobscured eye. The shift was small for the monocular flies, and it was larger (13° on average) when the screen was on one side of the fly. A new type of laser torquethrust transducer was developed and is described.     

An Elliptometer: A Simple Method of Measuring the Areas of Structures in Microscopic Sections

A simple method of measuring the cross sectional areas of objects (such as cells) in microscopic sections is described. A beam of light is passed through an adjustable diaphragm and focussed by a lens on a screen of mm. ruled graph paper. The screen may be rotated about a horizontal axis. Adjustment of the aperture of the diaphragm and the plane of the screen yields illuminated areas of variable size and degree of ellipticity. As close a “fit” as possible is made between the illuminated area and the camera lucida tracing of the object to be measured. The lengths of the major and minor axes of the appropriate ellipse are read from the screen. The application of the formula for the area of an ellipse to mean major and minor axes for a group of cells gives the mean cross sectional area for the cell population under investigation.     

Demonstration of phosphorylase activity in the rat brain

Summary The phosphorylase reaction in rat brain is strong, but for its correct evaluation in pathological states certain precautions are needed. Control material from animals of the same age should be used identically and simultaneously with the pathological, preferably freezing blocks from each on the same holder. Several sections should be cut and then the holder rotated through 180° and more sections cut, thus avoiding changes in section thickness which can drastically influence the color reactions, i.e., apparent phosphorylase activity. The time the animal is killed until its brain is frozen should be less than 5 min, preferably 11/2 to 3 min, to limit postmortem changes in the enzyme.Preparing the stock incubating medium and storing it at 4°C does not affect the potency of the medium; this procedure is convenient and eliminates more variables.Small amounts of medium can be placed between two slides set at right angles to each other. The height of the chamber, equal to the thickness of a slide, is uniform.Prefixation of the cryostat sections in cold acetone (4°C) for 5 min can be useful for obtaining sharper enzyme localization.AMP is the nucleotide of choice for stimulating full phosphorylase reaction. The inclusion of glycogen in the incubating medium is also necessary.The optimal incubation time for phosphorylase + branching enzyme is about 1/2 hr for 16 sections. For phosphorylase alone (active or total) it is about 2 hr. Dehydrating, clearing, and mounting in iodine-containing solutions is not recommended nor is it necessary. The best preservation of original colors, which is important for the correct interpretation of the results, is accomplished by sealing the preparations mounted in iodine-glycerin with paraffin.     

Comparative study on the thermostability of collagen I of skin and bone: Influence of posttranslational hydroxylation of prolyl and lysyl residues

Pepsin-solubilized collagen I from skin and bone was analyzed with regard to its thermal stability as a triple helical molecule in solution and afterin vitro fibril formation. Collagen I from human control bone was compared with samples showing deficiencies or surplus in the degree of hydroxylation of lysine. The helix to coil transitions were studied by circulardichroism measurements and limited trypsin digestion. Melting of fibrils from standardizedin vitro self-assembly was investigated turbidimetrically. Human control bone collagen I has a maximum transition rate (T _m ) at 43.3°C in 0.05% acetic acid. This is 1.9°C above control skin (T _m =41.4°C), most likely, due to a higher degree of prolyl hydroxylation—0.48 in bone vs. 0.41 in skin collagen I. Lysyl overhydroxylation of human and mouse bone collagen I appears to reduce theT _m slightly (1°C). Underhydroxylated bone collagen has aT _m which is 2°C below control. Melting temperatures ofin vitro formed fibrils are an indication for higher thermostability in parallel with an increase of lysyl hydroxylation. Accordingly, the melting temperature of such fibrils from human control skin, 49.3°C, exceeds control bone by 1.4°C. The degree of lysyl hydroxylation in these samples is 0.14 and 0.10, respectively. Further underhydroxylation (0.06) reduced it down to 45.4°C, while extensive overhydroxylation did not continue to increase the thermal stability of fibrils.     

The effects of rotation and positional change of stump tissues upon morphogenesis of the regenerating axolotl limb.

Rotation of a skin cuff 180° around the proximodistal axis of the upper arm in the axolotl results in the formation of multiple regenerates in about 80° of cases after amputation of the limb through the rotated skin. Rotation of the dermis or the flexor and extensor muscles folowed by amputation produced similar percentages of multiple regenerates. Rotated bone produced no abnormalities, and rotated stump epidermis was minimally effective in stimulating multiple regeneration. A thin strip of normally oriented skin interposed between a rotated skin cuff and the amputation surface blocks the morphogenetic effect of the rotated stump skin whereas removal of the normal skin between a rotated proximal skin cuff and the amputation surface allows the formation of a low percentage of multiple regenerates. Gross rotation of stump tissue components can be broken down into axial rotation per se and positional dislocation. Experiments conducted upon skin and muscle have shown that positional dislocation along the anteroposterior axis rather than axial rotation is the manipulation that leads to the formation of multiple regenerates. The first morphological indication of multiple regeneration is the appearance of a triaxial apical ridge on the blastema. Subsequently, digits form along the apical ridges.     

Theoretical and experimental behaviour of the muscle viscosity coefficient during maximal concentric actions

The aim of this study was to calculate the theoretical variation of the nonlinear damping factor (B) as a function of the muscle shortening velocity, and then to compare the theoretical values with the experimental data obtained on both the elbow flexor and the ankle extensor muscles. The theoretical variation of the B factor was determined from a muscle model consisting of a contractile component in parallel with a viscous damper both in series with an elastic component, and by using, the charateristic equation of the force velocity curve. In this muscle model, the viscous element modelled the inability of the muscle to generate as big a contracting force (while shortening) as possible under isometric conditions. Eight volunteer subjects performed maximal concentric elbow flexions and ankle extensions on an isokinetic ergometer at angular velocities of 60, 120, 180, 240, 300 and 360°·s^–1, and held two maximal isometric actions at an elbow angle of 90° (0° corresponds to the full extension) and at an ankle angle of 0° (0° corresponds to the foot flexion of 90° relative to the leg axis). From these measurements, the force and the shortening velocity values of each muscle were determined by using a musculo-skeletal model of the joint. The results showed that the theoretical behaviour of the B factor would seem to be dependent on the shortening velocity and on the parameter which varies according to the muscle fibre type composition and affects the curvature of the force-velocity curve (a_f). For each muscle group, the experimental data of B fitted with the theoretical equation, and the best fit was obtained for an of of 0.28 for the ankle extensor and of 0.32 for the elbow flexor muscles. These results indicated that from the muscle model used in the present study it is possible to describe the mechanical behaviour of the muscle during maximal concentric action.     

Temperature Dependences of Torque Generation and Membrane Voltage in the Bacterial Flagellar Motor

In their natural habitats bacteria are frequently exposed to sudden changes in temperature that have been shown to affect their swimming. With our believed to be new methods of rapid temperature control for single-molecule microscopy, we measured here the thermal response of the Na⁺-driven chimeric motor expressed in Escherichia coli cells. Motor torque at low load (0.35 μm bead) increased linearly with temperature, twofold between 15°C and 40°C, and torque at high load (1.0 μm bead) was independent of temperature, as reported for the H⁺-driven motor. Single cell membrane voltages were measured by fluorescence imaging and these were almost constant (∼120 mV) over the same temperature range. When the motor was heated above 40°C for 1–2 min the torque at high load dropped reversibly, recovering upon cooling below 40°C. This response was repeatable over as many as 10 heating cycles. Both increases and decreases in torque showed stepwise torque changes with unitary size ∼150 pN nm, close to the torque of a single stator at room temperature (∼180 pN nm), indicating that dynamic stator dissociation occurs at high temperature, with rebinding upon cooling. Our results suggest that the temperature-dependent assembly of stators is a general feature of flagellar motors.     

Validation of Radiation Dose Received by Frozen Unprocessed and Processed Bone during Terminal Sterilisation

Fresh frozen femoral heads (FH) and frozen processed bone (FP) are widely used as a source of allograft bone. The FP bone and some of the FH are terminally sterilised by the National Blood Service Tissue Services (NSBTS), via application of a minimum 25 kGy gamma radiation dose. To comply with the Guidelines for the Blood Transfusion Services in the United Kingdom (2002), frozen musculoskeletal tissue must be maintained below −40 °C during storage and transit. In practice, NBSTS stores bone long-term in −80 °C freezers. During transport for irradiation, a temperature of circa −79 °C is maintained by packing the bone in dry ice. An evaluation of the radiation dose received by bone has previously been made via dosimeters located within the tissue and dry ice, however, some evidence suggests that low temperature can influence the accuracy of the dosimeter readings. The aim of this study was to determine the actual radiation dose received by FH and FP bone during the irradiation process. This was accomplished by comparing radiation dose readings from dosimeters placed in dry ice with dosimeters placed in a dry ice substitute of similar dimensions and density i.e., polytetrafluoroethylene (PTFE) at ambient temperature. New packing formats were developed for both FH and FP bone such that 15 FH or 3 kg of FP bone could be irradiated in one transport box at any given time in a standardised fashion. The data show that low temperature consistently increased dosimeter readings 10–27%, and that radiation dose always fell within the range of 25–40 kGy (FH = 25.1–35.7 kGy; FP bone = 25.2–32.4 kGy).     

Quenching of an electric arc in a vacuum gap with a uniform transverse magnetic field

The breaking ability of a vacuum arc interrupter with a uniform transverse magnetic field formed by a system of permanent magnets was investigated experimentally. The vacuum interrupter with a 0.5-μF shunting capacitor switched off a dc current of up to 150 A at magnetic fields of 100–180 mT. At magnetic fields of 120–160 mT, the breaking ability of the vacuum interrupter was increased to 300 A by introducing a nonuniformity in the magnetic field distribution near the contact surface.     

Behavioural responses of European silver eels(Anguilla anguilla) to the geomagnetic field

Magnetic orientation of European silver eels(Anguilla anguilla) was tested in an octagonal tank. Orientation was determined from photo-registrations of eel positions in tests performed alternately in the natural magnetic field and a field with the horizontal component rotated 180°. Tests were performed in LD 11 : 13. At a daytime light intensity of 100 lux the fish were diurnally active, while at 0.10 lux crepuscular or nocturnal activity dominated. The eels probably differed in preferred orientation, largely depending on the clockwise or anti-clockwise swimming of some of the animals. Therefore there was no preferred direction common to all eels. The orientation of single eels differed, however, significantly between the two magnetic fields, suggesting that the eels responded to the geomagnetic field.     

The waggle dance of the honey bee: Which bees following a dancer successfully acquire the information?

During the waggle dance of the honeybee, the dancer is able to tell her nestmates the distance and direction to a rich food source (Frisch, 1967). Little is known about how waggle dance followers are able to read the waggle dance in the darkness of a hive. Initial observations showed that not all of the bees that appear to be dance followers behave the same. Some bees maneuver themselves behind the dancer, while others do not. The paths of a single dancer, trained to an artificial food source, and her followers were traced during the waggle runs. The success of these dance followers was compared to their position relative to the dancer. The results of this study show that during a waggle run a dance follower must position itself within a 30° arc behind the dancer in order to obtain the dance information. The results suggest that bees are using the position of their own bodies to determine direction.     

Social Interaction with an “Unidentified Moving Object” Elicits A-Not-B Error in Domestic Dogs

Mechanical “unidentified moving objects” (UMO’s) are useful for controlled investigations into features of social interaction that generate cooperativeness and positive social affiliation in domestic dogs (Canis familiaris). We hypothesized that, if a UMO interacted socially with a dog, the UMO would become associated with certain social cues and would subsequently affect dog behaviour. We assigned dogs to a Human, Social UMO or Non-Social UMO partner. In the Human and Social UMO conditions, the partner interacted with the dog cooperatively whereas the Non-Social UMO partner was unresponsive to the dog’s actions. We then tested dogs with their partner in a Piagetian A-not-B error paradigm, predicting that the Human and Social UMO partners would be more likely to elicit A-not-B errors in dogs than the Non-Social UMO partner. Five trials were conducted in which the dog watched its partner hide a ball behind one of two screens (A or B). As predicted, dogs in the Human and Social UMO conditions were more likely to search for the ball behind the A screen during B trials than dogs in the Non-Social UMO condition. These results reveal that the unfamiliar partner’s social responsiveness leads rapidly to accepting information communicated by the partner. This study has generated a better understanding of crucial features of agents that promote dog social behaviour, which will facilitate the programming of robots for various cooperative tasks.