Echo thresholds measured in the vertical and horizontal planes

The results of studying the precedence effect in the case where the direct and delayed (reflected) signals are located in the vertical and horizontal planes are considered. Loudspeakers emitting direct and reflected sounds were placed 45 deg to the left and right of the median line of the subject’s head in the horizontal plane and in front of and above the subject’s head, i.e., with 0 and 90 deg of elevation relative to the eye level, in the vertical plane. It has been shown that the time limits of the precedence effect of short (5-ms) signals are similar in the horizontal and vertical planes. For signals more than 10 ms in duration, the values of echo thresholds were higher in the vertical plane and significantly differed (p < 0.05) from the thresholds in the horizontal plane.     

Variation in natural head position and establishing corrected head position

Corrected head position (CHP) has been simulated by using the Frankfurt horizontal (FH) for over 100 years but FH varies between individuals. Because CHP is biologically relevant for orthodontic diagnosis and treatment planning, orthognathic surgical planning, and art, this study examined relationships between head position and selected cephalometric planes.     

Ecophysiological consequences of non-random leaf orientation in the prairie compass plant,Silphium laciniatum

Summary The prairie compass plant (Silphium laciniatum L.) has vertical leaves that are characteristically oriented in a north-south plane (i.e., the flat surfaces of the lamina face east and west). We explored the consequences of this orientation by determining basic photosynthetic and water use characteristics in response to environmental factors and by determining total daily photosynthesis and water use of leaves held in different orientations. Average maximum CO₂ exchange rate (CER) of leaves near Ames, IA was constant at 22 micromol m^–2 s^–1 from May through August and then declined. CER did not exhibit a distinct lightsaturation point. CER at photon flux densities near full sunlight was constant from 22 to 35°C leaf temperature but declined at higher temperatures. However, leaf temperatures rarely exceed 35°C during the growing season. There was no change in the pattern of response of CER to temperature over the growing season. We constrained leaves to face east-west (EW,=natural), to face north-south (NS), or to be horizontal (HOR) on eight days in 1986–1988. EW leaves had the highest light interception, leaf temperatures, CER, and transpiration early and late in the day, whereas HOR leaves had the highest values in the middle of the day. Integrations of CER and transpiration over the eight daytime periods showed EW and HOR leaves to have equivalent carbon gain, higher than that of NS leaves. HOR leaves had the highest daily transpiration. Daily water use efficiency (WUE, carbon gained/water lost) was always highest in EW leaves, with the HOR leaves having 16% lower WUE and NS leaves having 33% lower WUE. The natural orientation of compass plant leaves results in equivalent or higher carbon gain and in increased WUE when compared to leaves with other possible orientations; this is likely to have a selective advantage in a prairie environment.     

Kinematics of Visually-Guided Eye Movements

One of the hallmarks of an eye movement that follows Listing’s law is the half-angle rule that says that the angular velocity of the eye tilts by half the angle of eccentricity of the line of sight relative to primary eye position. Since all visually-guided eye movements in the regime of far viewing follow Listing’s law (with the head still and upright), the question about its origin is of considerable importance. Here, we provide theoretical and experimental evidence that Listing’s law results from a unique motor strategy that allows minimizing ocular torsion while smoothly tracking objects of interest along any path in visual space. The strategy consists in compounding conventional ocular rotations in meridian planes, that is in horizontal, vertical and oblique directions (which are all torsion-free) with small linear displacements of the eye in the frontal plane. Such compound rotation-displacements of the eye can explain the kinematic paradox that the fixation point may rotate in one plane while the eye rotates in other planes. Its unique signature is the half-angle law in the position domain, which means that the rotation plane of the eye tilts by half-the angle of gaze eccentricity. We show that this law does not readily generalize to the velocity domain of visually-guided eye movements because the angular eye velocity is the sum of two terms, one associated with rotations in meridian planes and one associated with displacements of the eye in the frontal plane. While the first term does not depend on eye position the second term does depend on eye position. We show that compounded rotation - displacements perfectly predict the average smooth kinematics of the eye during steady- state pursuit in both the position and velocity domain.     

Cerebral perfusion pressure in giraffe: modelling the effects of head-raising and -lowering

Loss of consciousness caused by positional changes of the head results from reduced cerebral blood flow (CBF). CBF is related to cerebral perfusion pressure (CPP). CPP is the difference between mean arterial pressure (MAP) at the head and intracranial pressure (ICP). The positional change of the giraffe head between ground level and standing upright is the largest of all animals yet loss of consciousness does not occur. We have investigated the possibility that an increase in CPP protects giraffe from fainting, using a mechanical model that functioned as an anatomical U-tube. It consisted of a rigid ascending “carotid” limb, a collapsible “brain” tube drained by a rigid, “vertebral venous plexus” (VVP) tube, and a collapsible “head” tube drained by a collapsible tube representing the “jugular vein”. The descending tubes could be rotated relative to the “carotid” tube to be horizontal, or at 30°, 45°, and 60° to the vertical to simulate changes in head position. Pressure at the top of the “carotid” tube was intracranial MAP, at the top of the “VVP” tube was ICP, and the difference CPP. In the simulated “head-up” position and a fluid flow rate of 4 L min⁻¹, CPP was ∼170 mmHg. With the VVP tube horizontal, CPP fell from ∼170 to 45 mmHg, but increased to ∼67 mmHg at 30° “down”, to ∼70 mmHg at 45° “down” and to ∼75 at 60° “down”. The fall in CPP in the head-down positions resulted from a decrease in viscous resistance in, and dissipation of pressure to, the “head” and “jugular” tubes. These data provide an estimate of cranial pressure changes in giraffe during positional changes of the head, and suggest that an increase in CPP plays a significant role in maintaining CBF during head-raising and that it may be an important mechanism for preventing fainting in giraffe.     

The visual field and visually guided behavior in the zebra finch (Taeniopygia guttata)

Summary Measurements were made of the physical properties of the visual system of the zebra finch, a bird with laterally placed eyes. The use of the visual system in pecking and courtship behavior was examined. It was demonstrated that the optical axis and the fovea of the eye point in a direction about 62° from the sagittal axis of the head. The visual field of each eye covers about 170° in the horizontal plane. In the frontal region there is an overlap of about 30°–40° where the birds can see binocularly; caudally there is a gap in the visual field of 60°. The point of best binocular viewing is in the sagittal plane at 16.5° below the beak.Concerning movement detection, the upper threshold is 540°/s for the binocular (frontal) part of the visual field and about 1100°/s for the monocular (lateral) part. Most fixations before pecking occur monocularly. A preference for one eye during pecking was not detected. During the courtship song, a male bird directs its head towards the female. The results are discussed in comparison with findings in pigeons and chickens.     

Assimilate transport in maize (Zea mays L.) seedlings at vertical low temperature gradients in the root zone

Even moderate chilling temperatures may cause important modifications in assimilate movement in maize seedlings from the shoot to the roots, but there is no information on long-distance transport of assimilates in plants subjected to vertical gradients of moderately low temperatures in the root zone. Seedlings of a chilling-tolerant (KW1074) and a chilling-sensitive inbred line (CM109) of maize were grown in a system that allowed the maintenance of temperature gradients between the topsoil (0-10 cm) and the subsoil (10-50 cm). After pregrowth at 24C until the third-leaf stage, plants were subjected to chilling-stress regimes for 6 d (17/17/17C, 17/17/12°C, 12/12/12°C, 12/12/17°C, air/topsoil/subsoil). The time taken for the assimilates to enter the phloem from the second leaf increased at low temperatures for both lines, but to a much greater extent in CM109. Although mainly influenced by air and topsoil temperature, low temperature in the subsoil also affected this trait in CM109. The speed of assimilate transport between the second leaf and the mesocotyl in KW1074 was strongly reduced by cool temperatures in the shoot and topsoil as well as by 12°C in the subsoil in CM109, because the latter line had a larger portion of its root system in the subsoil as compared to KW1074. The portion of assimilates allocated to the root decreased at low temperatures in both lines, but to a greater extent in CM109, and was controlled mostly by the subsoil temperature. After rewarming, values of all measured parameters of assimilate transport returned to near pregrowth levels within a few days.Keywords: Assimilate transport, low temperature stress, root growth, vertical soil temperature gradients, Zea mays L.      

Spatial perception and vestibulomotor responses in man

A study was made on normal human subjects, using a stabilograph to investigate changes in posture produced in response to transcutaneous galvanic stimulation of the right labyrinth. Results were obtained for different head positions and under the illusion of head and trunk rotation produced by stimulating (vibrating) the gulteus maximus muscle. In the absence of illusion of movement, the direction of the vestibulomotor response was determined by the position of the head in relation to the feed: with the normal head position, the body swayed on a frontal plane, and on a sagittal plane when the heat turned through 90°. Vestibulomotor responses were sagittally oriented, as with real head turning, when illusory head and trunk turning through 90° was produced by vibration. When the illusion of head rotation (in relation to the feet) was not produced by this stimulus, the direction of the postural response was not produced by this stimulus, the direction of the postural response was determined by the real orientation of the head. It is concluded that the spatial perception system plays a major part in controlling spatially oriented vestibulomotor responses.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 779–787, November–December, 1986.     

Head posture and craniofacial morphology

The associations between craniofacial morphology and the posture of the head and the cervical column were examined in a sample of 120 Danish male students aged 22–30 years. Two head positions were recorded on lateral cephalometric radiographs, one determined by the subject's own feeling of a natural head balance (self balance position), and the other by the subject looking straight into a mirror (mirror position). Craniofacial morphology was described by 42 linear and angular variables, and postural relationships by 18 angular variables. A comprehensive set of correlations was found between craniofacial morphology and head posture. The correlations were similar for both head positions investigated. Of the postural variables, the position of the head in relation to the cervical column showed the largest set of correlations with craniofacial morphology. Extension of the head in relation to the cervical column was found in connection with large anterior and small posterior facial heights, small antero-posterior craniofacial dimensions, large inclination of the mandible to the anterior cranial base and to the nasal plane, facial retrognathism, a large cranial base angle, and a small nasopharyngeal space. The possible role of functional factors in mediating the relationship between morphology and posture was discussed.     

Mechanosensory‐based orientation to elevated prey by a benthic fish

Lake Michigan mottled sculpin, Cottus bairdi, respond to both live and artificial (e.g., vibrating sphere) prey with an unconditioned movement towards the source of vibration, followed by a step‐by‐step approach and final strike at the source. In addition to these well‐studied, whole‐body movements along the horizontal plane of the substrate, sculpin exhibit a little‐studied behavior in which the vertical position of the fish's head can vary from being flush with the substrate to several cm's above the substrate. To test the hypothesis that sculpin can determine source elevation via mechanosensory cues, we measured head elevation of blinded fish as a function of source elevation and distance as fish approached a small (3 mm radius), 50 Hz vibrating sphere. At distances associated with pre‐strike positions (< 2 cm), head elevations were positively correlated with source elevation before but not after pharmacological blocking of the lateral line with CoCl₂. These results demonstrate that sculpin are able to determine source elevation using mechanosensory cues alone and that in the absence of visual and olfactory cues, vertical orientation of the head towards the source requires the lateral line system.     

Microtubule plus-ends reveal essential links between intracellular polarization and localized modulation of endocytosis during division-plane establishment in plant cells

Background  

A key event in plant morphogenesis is the establishment of a division plane. A plant-specific microtubular preprophase band (PPB) accurately predicts the line of cell division, whereas the phragmoplast, another plant-specific array, executes cell division by maintaining this predicted line. Although establishment of these specific arrays apparently involves intracellular repolarization events that focus cellular resources to a division site, it still remains unclear how microtubules position the cell division planes. Here we study GFP-AtEB1 decorated microtubule plus-ends to dissect events at the division plane.     

Investigation of body surface temperature measured with infrared imaging and its correlation with feed efficiency in the turkey (Meleagris gallopavo)

As feed intake is an expensive trait to measure in a breeding program, this study investigated whether body surface temperature was correlated with feed efficiency in the turkey. Infrared images were captured on male turkeys in individual feeding cages at approximately 19-weeks of age. Body surface temperature was measured on the eye, head, distal metatarsus, and neck of the birds with temperatures ranging from 34 °C to 40 °C. Body weight, feed intake, and weight gain data were collected and feed efficiency was measured as residual feed intake (RFI) and feed conversion ratio (FCR). Distal metatarsus temperature showed moderate correlations with body weight (0.15), average daily gain (0.26) and feed intake (0.23). Surface temperature of the head, eye, and neck were not as strongly correlated with these production traits. The feed efficiency traits showed low correlations with eye temperature ranging from −0.05 to −0.12 and surface temperatures at the head, distal metatarsus, and neck were not correlated with feed efficiency. Surface temperature traits explained only a small proportion of variation in feed intake. While the collection of infrared images was efficient and required minimal contact with the caged birds, the low correlations indicate that the technology, as used in this study, has limited advantages for increasing the accuracy of selection for feed efficiency.     

The Video Head Impulse Test (vHIT) Detects Vertical Semicircular Canal Dysfunction

Background

The video head impulse test (vHIT) is a useful clinical tool to detect semicircular canal dysfunction. However vHIT has hitherto been limited to measurement of horizontal canals, while scleral search coils have been the only accepted method to measure head impulses in vertical canals. The goal of this study was to determine whether vHIT can detect vertical semicircular canal dysfunction as identified by scleral search coil recordings.

Methods

Small unpredictable head rotations were delivered by hand diagonally in the plane of the vertical semicircular canals while gaze was directed along the same plane. The planes were oriented along the left-anterior-right-posterior (LARP) canals and right-anterior-left-posterior (RALP) canals. Eye movements were recorded simultaneously in 2D with vHIT (250 Hz) and in 3D with search coils (1000 Hz). Twelve patients with unilateral, bilateral and individual semicircular canal dysfunction were tested and compared to seven normal subjects.

Results

Simultaneous video and search coil recordings were closely comparable. Mean VOR gain difference measured with vHIT and search coils was 0.05 (SD = 0.14) for the LARP plane and −0.04 (SD = 0.14) for the RALP plane. The coefficient of determination R² was 0.98 for the LARP plane and 0.98 for the RALP plane and the results of the two methods were not significantly different. vHIT and search coil measures displayed comparable patterns of covert and overt catch-up saccades.

Conclusions

vHIT detects dysfunction of individual vertical semicircular canals in vestibular patients as accurately as scleral search coils. Unlike search coils, vHIT is non-invasive, easy to use and hence practical in clinics.     

Visuomotor operation in transition from object fixation to prey shooting in chameleons

Video-records of the eye and head position of chameleons (two species) in relation to prey targets revealed the following:1. Foveal fixation is performed monocularly for object identification before chameleons decide to catch the prey.2. If the chameleon intends to catch the prey, it turns its head towards the prey in preparation for the tongue shoot. While turning its head, the fixating eye does not continue to keep the target fixed foveally. Rather, it adopts a diverging position to the head, the mediosagittal plane of which in the end is target-directed.3. Ready for tongue shoot, the position of both eyes to the head is definitely adjusted at a fixed diverging angle of 17–19 deg, and this position does not change at all with distance to the target.4. Chameleons are also able to perform tongue shoots successfully using only one eye (the other being occluded), and they use the same adjustment of prey to eye and eye to head as in the binocular case.5. Thus, the correct direction of the tongue shoot in chameleons is processed by an extrafoveal retinotopic depiction of the prey image using monocular distance information and a fixed eye in head position. Received: 10 November 1992/Accepted in revised form: 24 February 1994     

Temperatures from 4 to 15 °C are suitable for preserving the fertilizing capacity of stallion semen stored for 22 h or more in INRA96 extender

This study tested whether variable temperatures (from −0.5 to 15 °C) and air exposure could be used under laboratory and under field conditions to store stallion sperm diluted in extender INRA96 without loss of fertility. Experiment 1 (laboratory conditions) measured the effects of two 72 h storage conditions (5 °C with air vs. 15 °C without air). Experiment 2 (fixed field conditions) measured the effects of 22 h of storage without air in disposable containers maintained at four ambient temperatures (7 °C, 17 °C, 27 °C, 39 °C with semen at −0.5 °C to 3 °C, 4 °C to 7 °C, 8 °C to 10 °C, 12 °C to 15 °C, respectively). Per cycle pregnancy rate (PC) was measured after one artificial insemination (AI) in uterine body of 200 × 10⁶ total spermatozoa, 7 h (Experiment 1) or 17 h (Experiment 2) before ovulation. In Experiment 1, PC was similar for both conditions (60% (n = 40 cycles) vs. 63% (n = 40), respectively, 5 stallions × 8 cycles). Only velocity VCL and ALH were slightly higher at 15 °C. In Experiment 2, PC was reduced when ambient temperature was low (semen at −0.5 °C to 3 °C; PC = 25%) rather than intermediate (semen at 4 °C to 7 °C; PC = 53%) or high (semen at 8 °C to 10 °C; PC = 50%) (4 stallions × 8 cycles) (P = 0.002). Sperm stored at −0.5 °C to 3 °C had lower acrosome integrity/responsiveness, similar membrane integrity (HOS test) and motilities, and higher VCL and ALH, than semen stored between 4 and 15 °C. These results demonstrate a wide tolerance of equine sperm to variable positive temperatures and air exposure for 22 h storage and more. However, temperatures close to 0 °C are detrimental for fertility.     

Temperature/light dependent development of selective resistance to photoinhibition of photosystem I

Exposure of winter rye leaves grown at 20°C and an irradiance of either 50 or 250 μmol m⁻² s⁻¹ to high light stress (1600 μmol m⁻² s⁻¹, 4 h) at 5°C resulted in photoinhibition of PSI measured in vivo as a 34% and 31% decrease in ΔA₈₂₀/A₈₂₀ (P700⁺). The same effect was registered in plants grown at 5°C and 50 μmol m⁻² s⁻¹. This was accompanied by a parallel degradation of the PsaA/PsaB heterodimer, increase of the intersystem e⁻ pool size as well as inhibition of PSII photochemistry measured as F_v/F_m. Surprisingly, plants acclimated to high light (800 μmol m⁻² s⁻¹) or to 5°C and moderate light (250 μmol m⁻² s⁻¹) were fully resistant to photoinhibition of PSI and did not exhibit any measurable changes at the level of PSI heterodimer abundance and intersystem e⁻ pool size, although PSII photochemistry was reduced to 66% and 64% respectively. Thus, we show for the first time that PSI, unlike PSII, becomes completely resistant to photoinhibition when plants are acclimated to either 20°C/800 μmol m⁻² s⁻¹ or 5°C/250 μmol m⁻² s⁻¹ as a response to growth at elevated excitation pressure. The role of temperature/light dependent acclimation in the induction of selective tolerance to PSI photoinactivation is discussed.     

Spatial transformation of semicircular canal signals into abducens motor signals. A comparison between grass frogs and water frogs

The spatial transformation of semicircular canal signals to extraocular motor signals was studied by recording abducens nerve responses in grass and water frogs. Both species have similar vestibular canal coordinates but dissimilar orientations of their optic axes. Before sinusoidal oscillation in darkness the static head position was systematically altered to determine the planes of head oscillation in pitch and roll associated with minimal abducens nerve responses. Measured data and known canal plane vectors were used to calculate the abducens response vector in canal coordinates. The abducens vector deviated from the horizontal canal plane vector in grass frogs by 15° and in water frogs by 34° but was aligned with the pulling direction of the lateral rectus muscle in each of the two species. Lesion experiments demonstrated the importance of convergent inputs from the contralateral horizontal and anterior semicircular canals for the orientation of the abducens response vector. Thus, the orientation of the optic axis and the pulling directions of extraocular muscles are taken into account by the central organization of vestibulo-ocular reflexes. Horizontal and vertical canal signals are combined species-specifically to transform the spatial coordinates of sensory signals into appropriate extraocular motor signals. Accepted: 16 November 1997     

Flight torque and lift responses of the housefly (Musca domestica) to a single stripe moving in different parts of the visual field

Visually evoked torque and lift responses in fixed flying houseflies Musca domestica, were measured under open loop conditions. The visual stimuli were: a) Vertical stripes (60°×5°), moving horizontally in a range±30°. b) Horizontal stripes (60°×5°), moving vertically in a range±30°. c) Vertical stripes (30°×5°), moving horizontally in a range±55° in five different planes relative to the equatorial plane (=0) of the fly's eye. d) Horizontal stripes (30°×5°), moving vertically in a range±45° in seven different planes (=-45°,-30°,-15°, 0°, 15°, 30°, 45°) relative to the symmetry line (=0) between the two compound eyes. e) Periodic gratings displayed by two projectors at each side of the test animals (the middle part was situated at =±50°). The stimulated area was roughly 52°×80° (2000 ommatidia). This stimulus was used only in lift experiments. The results are: 1) The preferred direction of the direction sensitive torque response corresponds with the z-direction (Braitenberg, 1971). 2) The direction sensitive torque response is elicited by stimulating above and below the equatorial plane. 3) The direction insensitive torque response is only elicited by stimulating close to and below the equatorial plane. 4) The preferred direction of the direction sensitive lift response has an angle tilted about 30° to the back relative to the vertical axis in the region described in e). 5) The magnitude of the direction sensitive lift response varies considerably over . 6) The w/ dependence of the direction sensitive lift response corresponds qualitatively to the known w/ dependence of the direction sensitive torque responses. 7) The direction insensitive lift response has its maximum at =±15° and decreases with increasing . 8) The findings reported in 3) and 8) indicate the existence of a two-dimensional potential from which the attraction towards a stripe in the two considered degrees of freedom can be derived. Implications for the visually induced orientation behaviour and connections with electrophysiological experiments are discussed.     

Active tactile sensing for localization of objects by the cockroach antenna

Antennal movement during tactile orientation behavior was examined three-dimensionally in American cockroaches during tethered walking. When a wooden rod was presented to the tip of one antenna in an upright orientation at one of the three different horizontal positions (30°, 60°, or 90° from the center of the head), the animal touched it repeatedly with the antenna, and tried to approach it (positive thigmotaxis). Positional shifts were also observed for the contralateral unstimulated antenna. The ipsilateral antenna tended to touch the object during inward movement (adduction) at all three test angles. The cumulative turn angle made during a continuous test period of 24 s clearly depended on the object’s position; however, the contact frequencies were almost the same regardless of the position. The relationships between contact frequency and some locomotion parameters were also investigated on a shorter time scale of 3 s. The contact frequency positively correlated with the turn angle, with the accuracy of orientation at all three test angles, and with the translation velocity at test angles of 30° and 60°. It is concluded that the performance during tactile orientation can be represented effectively by the frequency with which the antennae touch the attractive objects.     

Horizontal or vertical photobioreactors? How to improve microalgae photosynthetic efficiency

The productivity of a vertical outdoor photobioreactor was quantitatively assessed and compared to a horizontal reactor. Daily light cycles in southern Spain were simulated and applied to grow the microalgae Chlorella sorokiniana in a flat panel photobioreactor.The maximal irradiance around noon differs from 400 μmol photons m⁻² s⁻¹ in the vertical position to 1800 μmol photons m⁻² s⁻¹ in the horizontal position. The highest volumetric productivity was achieved in the simulated horizontal position, 4 g kg culture⁻¹ d⁻¹. The highest photosynthetic efficiency was found for the vertical simulation, 1.3 g of biomass produced per mol of PAR photons supplied, which compares favorably to the horizontal position (0.85 g mol⁻¹) and to the theoretical maximal yield (1.8 g mol⁻¹). These results prove that productivity per unit of ground area could be greatly enhanced by placing the photobioreactors vertically.