共查询到20条相似文献,搜索用时 15 毫秒
1.
J. E. Flanigan P. C. Withers C. J. Fuery M. Guppy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(7):587-593
During aestivation the metabolic rate of the Australian goldfields frog Neobatrachus wilsmorei was reduced by 80% from its standard metabolic rate. The in vitro rate of oxygen consumption of isolated muscle and skin from aestivating frogs was up to 50% lower than that of the non-aestivating frogs. This in vitro rate of oxygen consumption was maintained for 6–12 h, indicating an intrinsic metabolic depression of tissues during aestivation. Frogs became dehydrated during aestivation. Muscle, skin and liver also became dehydrated during aestivation, but brain and kidney did not. Na+ and K+ contents and extracellular space measurement for muscle indicated that ion gradients were maintained across the muscle cell membrane during aestivation. Increases in plasma concentrations of Na+ and K+ were matched with similar increases in muscle intracellular ion concentrations. Extracellular space measurements were unsuccessful in the other tissues, but K+ content in all tissues (per dry weight) was maintained during aestivation, and the concentration of plasma K+ did not increase above that which can be accounted for by dehydration, indicating that K+ gradients were maintained.Abbreviations bm
body mass
- DPM
disintegrations per minute
- dw
dry weight
- MR
metabolic rate
- vO2
rate of oxygen consumption
- ww
wet weight 相似文献
2.
C. M. Valdez K. C. Nishikawa 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):187-202
This study investigates how visual and tactile sensory information, as well as biomechanical effects due to differences in
physical characteristics of the prey, influence feeding behavior in the frog Cyclorana novaehollandiae. Video motion analysis was used to quantify movement patterns produced when feeding on five prey types (termites, waxworms,
crickets, mice and earthworms). Twelve kinematic variables differed significantly among prey types, and twelve variables were
correlated with prey characteristics (including mass, length, height and velocity of movement). Results indicate that C.␣novaehollandiae uses a different strategy to capture each prey type. Visual assessment of prey characteristics appeared to be more important
in modulating feeding behavior than tactile cues or biomechanical effects. We propose a hierarchical hypothesis of behavioral
choice, in which decisions are based primarily on visual analysis of prey characteristics. In this model, the frogs first
choose between jaw prehension and tongue prehension based on prey size. If they have chosen jaw prehension, they next choose
between upward or downward head rotation based on length and height of the prey. If they have chosen tongue prehension, they
next choose between behavior for fast and slow prey. Final decisions may be the result of behavioral fine tuning based on
tactile feedback.
Accepted: 5 August 1996 相似文献
3.
Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold 总被引:3,自引:0,他引:3
Gregory D. Maniero Cynthia Carey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):256-263
The effect of exposure to low temperatures (5 °C) on lymphocyte proliferation, leukocyte populations, and serum complement
levels was examined in the northern leopard frog, Rana pipiens. Proliferation of T lymphocytes in response to phytohemagglutinin stimulation was significantly decreased in frogs kept for
2, 3, and 5 months at 5 °C compared to that of animals kept at 22 °C. A significant increase in the average percentage of
neutrophils and a decrease in the mean percentage of eosinophils was observed in the blood of frogs held for 5 months in the
cold compared to animals held at 22 °C for the same length of time. Mean serum complement activity after 1 month at 5 °C was
significantly reduced in comparison to animals held at 22 °C and was not detectable after 5 months in the cold. Recovery of
complement levels at room temperature (22 °C) was also examined after cold exposure. Complement levels were significantly
higher than controls (at 22 °C) in frogs returned to 22 °C for 7 and 14 days after 5 months in the cold. After frogs were
held at 5 °C for 1 month, serum complement levels increased significantly within 2 days after returning to 22 °C and continued
to rise 5 and 9 days after warming. Injections with Aeromonas hydrophila following a 5-week exposure to 5 °C failed to cause death or observable symptoms of disease in frogs that were returned to
22 °C.
Accepted: 20 November 1996 相似文献
4.
Gerhard Krumschnabel Christina Biasi Pablo J. Schwarzbaum Wolfgang Wieser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):280-286
Short- and long-term effects of temperature on ion flux and energy turnover were studied in hepatocytes from thermally acclimated
trout and roach. In trout hepatocytes K+ efflux was insensitive towards acute exposure to low temperature but was downregulated during cold acclimation of the fish
so as to balance the uncompensated decreased K+(Rb+) uptake of the cells. In contrast, both K+(Rb+) uptake and K+ efflux of roach hepatocytes were temperature sensitive in the short term. These acute effects, however, were offset during
cold acclimation by a near perfect compensation of both fluxes leading to re-establishment of ion flux homeostasis at the
original level. Our findings, based on a new method permitting the simultaneous monitoring of K+ efflux and uptake in the same cell population, provide experimental verification of two of the three possible strategies,
recently discussed by Cossins et al. (1995), by which the ionic steady state of fish cells may adjust to acute and chronic
temperature change. By comparing hepatocytes from two groups of trout, one kept on a maintenance diet (ration I), the other
fed ad libitum (ration II), we discovered striking effects of nutritional state on the absolute levels as well as on the temperature relationships
of K+ uptake and protein synthetic activity. Both of these functions in the hepatocytes increased in the ration II fed as compared
to the ration I fed trouts, but the increase of protein synthetic activity was greater and more uniform at the three experimental
temperatures than that of K+ uptake. Moreover, protein synthetic activity proved to be considerably more temperature sensitive than K+ uptake and, in contrast to the latter, showed a compensatory response after cold acclimation.
Accepted: 16 December 1996 相似文献
5.
U. Gerster D. G. Stavenga W. Backhaus 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(2):113-122
Na+/K+-pump activity and intracellular Na+ and K+ concentration changes in blowfly photoreceptors are derived from intracellular potential measurements in␣vivo with a model
based on the Goldman-Hodgkin-Katz theory for membrane currents. The relation between the intracellular Na+ concentration and the pump activity appears to follow a Hill function with a Hill coefficient of 1 and a maximal possible
Na+ current due to pump activity of about −4 nA. The developed photoreceptor model incorporates the slow and fast voltage-dependent
K+ channels of the blowfly photoreceptor of which the properties were taken from the literature.
Accepted: 5 August 1996 相似文献
6.
M. Kato A. Aoyama F. Naruse T. Kobayashi N. Tsukagoshi 《Molecular & general genetics : MGG》1997,254(2):119-126
Using AnCP (Aspergillus nidulans CCAAT-binding protein) as a CCAAT-specific binding factor model, the possibility that one factor is able to recognize CCAAT
sequences in several different genes in A.␣nidulans was examined. DNase I protection analysis showed that AnCP specifically bound to CCAAT sequence-containing regions comprising
21 to 36 bp of the taa, amdS and gatA genes. Furthermore, replacement of the CCAAT sequence with CGTAA was found to abolish the binding of AnCP and to have an
inhibitory effect on taa promoter activity. This clearly demonstrates a positive function of the CCAAT element. However, amylase was induced by starch
and repressed by glucose in a CCAAT-box disruptant, as in wild-type cells.
Received: 28 June 1996 / Accepted: 7 October 1996 相似文献
7.
Evolution of Substrate Specificities in the P-Type ATPase Superfamily 总被引:23,自引:0,他引:23
P-type ATPases make up a large superfamily of ATP-driven pumps involved in the transmembrane transport of charged substrates.
We have performed an analysis of conserved core sequences in 159 P-type ATPases. The various ATPases group together in five
major branches according to substrate specificity, and not according to the evolutionary relationship of the parental species,
indicating that invention of new substrate specificities is accompanied by abrupt changes in the rate of sequence evolution.
A hitherto-unrecognized family of P-type ATPases has been identified that is expected to be represented in all the major phyla
of eukarya.
Received: 21 May 1997 / Accepted: 1 August 1997 相似文献
8.
The central grassland region of the United States encompasses major gradients in temperature and precipitation that determine
the distribution of plant life forms, which in turn may influence key ecosystem processes such as nutrient cycling and soil
organic matter dynamics. One such gradient is the threefold increase in precipitation from the eastern Colorado shortgrass-steppe,
in the rain shadow of the Rocky Mountains, to the tallgrass prairie in eastern Kansas. We investigated the relative roles
of plant species and plant cover in influencing soil C and N cycling in three sites along this gradient. Plant cover (i.e.,
the presence or absence of an individual plant) was relatively more important than plant species in explaining variability
in soil properties at the dry site, the Central Plains Experimental Range in␣northeastern Colorado. However, plant species
explained relatively more of the variability in soil properties than did plant cover at the two wetter sites, Hays and Konza,
in central and eastern Kansas. The wetter sites had more continuous plant cover, resulting in less plant-cover-induced variation
in soil C and N, than did the dry site, which had distinct patches of bare ground. Plant species at the wetter sites had higher
and more variable levels of tissue C:N than plant species at the dry site, due to both within species changes and changes
in species composition. Aboveground tissue C:N was better correlated with net nitrogen mineralization rates at the wet sites
than the dry site. Thus, tissue chemistry appears to exert more control on nitrogen dynamics at the wet than the dry sites.
The results suggest that plant species traits that are relevant to nutrient cycling (e.g., tissue C:N ratios, spatial patterns,
productivity) reflect environmental limitations as well as species' physiological potentials. Furthermore, a dominant environmental
driver such as precipitation may ameliorate or exaggerate the importance of individual species traits for nutrient cycling.
Received: 11 July 1996 / Accepted: 5 December 1996 相似文献
9.
Ralph Beneke Katharina Meyer 《European journal of applied physiology and occupational physiology》1997,75(3):246-251
The effect of a 3-week exercise programme on performance and economy of walking was analysed in 16 male patients with chronic
heart failure [mean age 51.8 (SD 6.9) years, height 174.9 (SD 6.3) cm, body mass 75.3 (SD 11.5) kg, ejection fraction 20.8
(SD 5.0)%]. They were submitted to a cardiopulmonary exercise test on a cycle ergometer and a 6-min walking test on a treadmill
before and after the period of exercise training. The training programme consisted of interval cycle (five times a week for
15 min), and treadmill ergometer training (three times a week for 10 min) at approximately 70% cycling peak oxygen uptake
(O2peak) and supplementary exercises (three times a week for 20 min). Compared to the pre values cycling O2peak [11.9 (SD 2.9) vs 14.0 (SD 2.3) ml · kg–1 · min–1], maximal self paced walking speed [0.68 (SD 0.33) vs 1.16 (SD 0.30) m · s–1], and net walking power [2.16 (SD 0.89) vs 2.73 (SD 0.91) W · kg–1] had increased (P < 0.01) while net energy cost [3.31 (SD 0.66) vs 2.33 (SD 0.38) J · kg–1 · m–1] had decreased (P < 0.001) after the training period. Approximately 42% of the increase of walking speed resulted from a higher walking power
output, whereas approximately 58% corresponded to a positive effect on walking economy. The improvement in walking economy
was a function of an increase in walking velocity itself and a result of a more efficient walking technique. These results
would indicate that in patients with marked exercise intolerance, adequate exercise training programmes could contribute to
favourable metabolic changes with positive effects on the economy of motion.
Accepted: 29 August 1996 相似文献
10.
G. Körtner X. Song F. Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(8):631-638
Circadian rhythms have been observed in most mammals, but their importance and function remain controversial with respect
to daily cycles during hibernation. We investigated the timing of arousals from and entries into hibernation for both free-living
and captive mountain pygmy-possums (Burramys parvus). Under both natural and laboratory conditions most arousals and entries were entrained with the light-dark cycle. Entries
occurred mainly during the night and arousals preferably around dusk, which coincides with the onset of the normal activity
phase for the nocturnal pygmy-possums. This entrainment prevailed throughout the hibernation season although only the laboratory
animals were constantly subjected to photoperiodic stimuli, whereas under natural conditions hibernacula are shielded from
photic cues and diurnal temperature fluctuations. Nevertheless, possums left their hibernacula frequently throughout winter
and were occasionally trapped close to the snow surface suggesting that during the periods of post-arousal normothermia they
can be exposed to environmental stimuli. It thus appears that the synchronisation with the photocycle was governed by a temperature-compensated
circadian clock which was reset periodically during short activity periods. For the mountain pygmy-possum, entrainment with
the photocycle probably has two functions:
1. Entrainment ensures that foraging bouts during the hibernation season remain synchronised with the dark phase.
2. Information about the prevailing climatic conditions sampled during short activity periods enables them to time final spring
emergence from hibernation when snow melt begins and ensures that the breeding season can commence as early as possible.
Accepted: 26 August 1998 相似文献
11.
Photoperiodic time measurement regulating larval diapause in the pitcher-plant mosquito, Wyeomyia smithii, varies in a close relationship with latitude. The critical photoperiod mediating the maintenance and termination of diapause
is positively correlated with latitude (r
2 = 0.977) among six populations from southern (30–31° N), intermediate (40° N), and northern (46–49° N) latitudes in North
America. The developmental response to unnaturally short and to unnaturally long photoperiods declines with increasing latitude,
so that longer critical photoperiods are associated with a downward rather than a lateral shift in the photoperiodic response
curve. Exotic light and dark cycles of varying period (T) with a short (10 h) photophase and a scotophase ranging from 14
(T = 24) to 62 (T = 72) h, reveal two geographic patterns: a decline in perturbability of the photoperiodic clock with increasing
latitude, and no change with latitude in the 21-h period of rising and falling development with increasing T. These results
show (1) that there is a rhythmic component to photoperiodic time measurement in W. smithii, (2) that the period of this rhythm is about 21 h in all populations, and (3) that more northern populations show decreasing
responsiveness to photoperiod and increasing stability against perturbation by exotic period lengths (T > 24). Previous studies
on W.␣smithii indicate that this single temperate species of a tropical and subtropical genus has evolved from south to north. We therefore
conclude that the evolution of increasing critical photoperiod in W. smithii during its adaptive radiation into North America has more likely involved the amplitude and not the period of the underlying
circadian pacemaker.
Received: 22 July 1996 / Accepted: 30 September 1996 相似文献
12.
P. Meier J. Zettel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):297-304
In the Swiss Prealps Entomobrya nivalis hibernates in an inactive state, hidden under bark flakes on spruce. For freeze avoidance it relies on thermal hysteresis
proteins (THPs) and polyols (mainly ribitol, with small amounts arabitol and threitol). Polyols are present only during the
inactive state, THPs additionally protect during the transition phase in spring and autumn, when animals are still active
but frosts may occur. Peak values were recorded in February/March for THPs (3.5 °C hysteresis between melting and freezing
point) and for polyols (26 μg mg−1 FW; hemolymph osmolality 680 mosmol l−1). E. nivalis is able to control its hemolymph osmolality independently of body water content. Mean osmolality in summer was 350– 440 mosmol l−1, in winter it was elevated to 650 mosmol l−1, due to a synthesis mainly of ribitol. Body water content varied between 1.8 and 3.3 mg H2O mg−1 DW, depending on humidity conditions. Experiments on triggering of antifreeze synthesis showed the action of temperature
and photoperiod as cues, but there was also evidence for an endogenous rhythm. No clear correlation between antifreeze concentration
and supercooling ability could be established, suggesting that gut content or other parameters also play an inportant role.
Accepted: 18 November 1995 相似文献
13.
E. R. Wood D. E. Wiel J. C. Weeks 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):639-657
The larval proleg withdrawal reflex of the hawk moth, Manduca sexta, exhibits robust habituation. This reflex is evoked by deflecting one or more mechanosensory planta hairs on a proleg tip.
We examined neural correlates of habituation in an isolated proleg preparation consisting of one proleg and its segmental
ganglion. Repeated deflection of a single planta hair caused a significant decrease in the number of action potentials evoked
in the proleg motor nerve (which carries the axons of proleg retractor motor neurons). Significant response decrement was
seen for interstimulus intervals of 10 s, 60 s and 5 min. Response decrement failed to occur in the absence of repetitive
stimulation, the decremented response recovered spontaneously following a rest, and electrical stimulation of a body wall
nerve facilitated the decremented response (a neural correlate of dishabituation). Adaptation of sensory neuron responses
occurred during repeated hair deflections. However, when adaptation was eliminated by direct electrical stimulation of sensory
neurons, the response in the proleg motor nerve still decreased significantly. Muscle recordings indicated that the response
of an identified proleg retractor motor neuron decreased significantly during habituation training. Thus, habituation of the
proleg withdrawal reflex includes a central component that is apparent at the level of a single motor neuron.
Accepted: 20 December 1996 相似文献
14.
Jan Eivind Østnes Claus Bech 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):241-248
The ontogeny of deep-body cold sensitivity was studied in 1 to 12 days old Pekin ducklings Anas platyrhynchos. Deep-body cold sensitivity was determined by means of thermodes implanted in the abdominal cavity. The thermodes were perfused
with cold water for 15-min periods to lower the core temperature. Cooling of the body core elicited increases in metabolic
rate and vasoconstrictions in the legs of all the ducklings. From the changes induced in metabolic rate and core temperature,
deep-body cold sensitivity values of between −5.17 and −6.36 W · kg−1 · °C−1, were estimated. These values, which are in the range of those reported previously for adult Pekin ducks, did not change
with age, and it is concluded that deep-body cold sensitivity is fully developed at hatching. Our next aim was to investigate
whether the autonomic responses elicited by exposure of ducklings to cold ambient conditions could be explained by temperature
changes within the body core. During cold exposure, the increase in metabolic rate was not accompanied by a concomitant decrease
in core temperature. On the contrary, deep-body temperature increased slightly during the initial phase of cold exposure.
The ducklings attained a metabolic rate amounting to 85–90% of their peak metabolic rate before the core temperature fell
below the regulated level measured at thermoneutrality. Thus, despite the findings that Pekin ducklings have a highly-developed
deep-body cold sensitivity, their metabolic cold defence under natural conditions seems to be mediated primarily by peripheral
thermoreceptors.
Accepted: 7 January 1997 相似文献
15.
16.
W. Li P. W. Sorensen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):429-438
(1) Electro-olfactogram recording was used to determine whether the olfactory epithelium of adult sea lamprey is specifically
sensitive to bile acids, some of which have been hypothesized to function as pheromones. Ten bile acids were selected from
38 which had already been pre-screened for olfactory activity. These compounds were first tested on their own, then as adapting
stimuli, and finally as components of mixtures (2) The lamprey-specific bile acids, petromyzonol sulfate and allocholic acid,
were the most potent compounds tested. Five other bile acids were also detectable at picomolar concentrations. Petromyzonol
sulfate had a distinctive dose-response curve. (3) Cross-adaptation demonstrated that sensitivity to bile acids is attributable
to at least four independent classes of olfactory receptor sites and that both the nature and position of conjugating group(s)
are critical to receptor specificity. Notably, petromyzonol sulfate has its own highly specific and independent receptor site.
The situation for unconjugated bile acids was more complex and there appeared to be several sub-classes of receptor sites
for these compounds. (4) Mixture studies largely confirmed the cross-adaptation results, describing receptor site independence
for the same four sets of odorants. Mixture enhancement was also seen when expected and there was no evidence of mixture suppression.
(5) Together, these data demonstrate that conspecific bile acids are discriminated by the olfactory epithelium of the sea
lamprey, supporting the possibility that these compounds may function as migratory pheromones.
Accepted: 23 November 1996 相似文献
17.
A. D. Blest Sally Stowe 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):347-355
(1) In vitro retinas of a crab, Leptograpsus, were treated with a phospholipase inhibitor, manoalide, or a G-protein activator, Mas-7. Both drugs address early stages
of the phototransduction cascade. (2) Manoalide inhibited the light-dependent reduction of rhabdoms during the `day' phase
of the light cycle, but did not induce rhabdom overgrowth. Following a period of darkness manoalide failed to affect the diminution
of illuminated rhabdoms. (3) The diminution of rhabdoms that follows photoreceptor depolarisation induced by 100 mmol · l−1 K+ in darkness was not affected by 2␣μmol · l−1 manoalide. (4) When retinas in the `night' phase were treated with Mas-7 in darkness, rhabdom diameters were augmented, concurrently
with endocytosis of photoreceptor plasma membranes. (5) The results of combining manoalide and Mas-7 with actinomycin D, U-57908
or okadaic acid, drugs used in previous studies to manipulate steps notionally lower in the transduction cascade, lead to
a hypothetical model for the regulation of phototransductive membrane turnover by arthropods.
Accepted: 3 October 1996 相似文献
18.
Mark. A. Chappell Gwendolyn C. Bachman Kimberly A. Hammond 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):313-318
The heat increment of feeding (HIF), a transient postprandial increase in metabolic rate, is the energy cost of processing
a meal. We measured HIF in house wren chicks (Troglodytes aedon) ranging in mass from 1.6 to 10.3 g. This mass range (age 2–10 days) spanned a transition from blind, naked, ectothermic
chicks through alert, endothermic birds with nearly complete feathering. We fed chicks crickets (2.7–10% of chick body mass)
and determined HIF from continuous measurements of oxygen consumption rate (O2) before and after meals. At warm ambient temperatures (T
a) of 33–36 °C, the magnitude of HIF (in ml O2 or joules) was linearly related to meal mass and was not affected by chick mass. HIF accounted for 6.3% of ingested energy,
which is within the range of results for other carnivorous vertebrates. The duration of HIF was inversely related to chick
mass; 10-g chicks processed a standard meal approximately twice as fast as 2-g chicks. HIF duration increased with increasing
meal mass. The peak O2 during HIF, expressed as the factorial increase above resting metabolism, was independent of body mass and meal mass. In
large, endothermic chicks ( > 8 g), HIF substituted for thermoregulatory heat production at low T
a.
Accepted: 11 December 1996 相似文献
19.
In this study we used pinfish (Lagodon rhomboides) in field experiments to examine linkages between intertidal saltmarsh and adjacent subtidal habitats. Pinfish are more
than twice as abundant in intertidal marshes adjacent to seagrass beds than in those adjacent to the unvegetated subtidal
bottom. Movement of pinfish between the marsh edge and the adjacent subtidal habitat was greater for fish captured in areas
with both intertidal and subtidal vegetation than in those with intertidal vegetation and adjacent unvegetated mudflats. This
movement provides an important link between habitats, allowing transfer of marsh-derived secondary production to subtidal
seagrass beds and vice versa. Pinfish held in enclosures with both intertidal and subtidal vegetation were, on average, approximately
90% heavier than fish held in enclosures with intertidal vegetation and unvegetated subtidal bottom. Because saltmarshes and
seagrass beds contribute to the production of living marine resources, active measures are being taken to preserve and restore
these habitats. The results from this study have direct application to decisions concerning site selection and optimal spatial
proximity of saltmarsh and seagrass habitats in the planning of restoration and mitigation projects. To maximize secondary
production and utilization of intertidal marshes, managers may opt to restore and/or preserve marshes adjacent to subtidal
seagrass beds.
Received: 31 May 1996 / Accepted: 23 October 1996 相似文献
20.
Peter J. Simmons F. Claire Rind 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):203-214
The LGMD2 belongs to a group of giant movement-detecting neurones which have fan-shaped arbors in the lobula of the locust
optic lobe and respond to movements of objects. One of these neurones, the LGMD1, has been shown to respond directionally
to movements of objects in depth, generating vigorous, maintained spike discharges during object approach. Here we compare
the responses of the LGMD2 neurone with those of the LGMD1 to simulated movements of objects in depth and examine different
image cues which could allow the LGMD2 to distinguish approaching from receding objects. In the absence of stimulation, the
LGMD2 has a resting discharge of 10–40 spikes s−1 compared with <1 spike s−1 for the LGMD1. The most powerful excitatory stimulus for the LGMD2 is a dark object approaching the eye. Responses to approaching
objects are suppressed by wide field movements of the background. Unlike the LGMD1, the LGMD2 is not excited by the approach
of light objects; it specifically responds to movement of edges in the light to dark direction. Both neurones rely on the
same monocular image cues to distinguish approaching from receding objects: an increase in the velocity with which edges of
images travel over the eye; and an increase in the extent of edges in the image during approach.
Accepted: 23 October 1996 相似文献