Effects of temperature and dissolved oxygen on heart rate,ventilation rate and oxygen consumption of spangled perch,Leiopotherapon unicolor (Günther 1859), (Percoidei,Teraponidae)

Summary Heart, ventilation and oxygen consumption rates ofLeiopotherapon unicolor were studied at temperatures ranging from 5 to 35°C, and during progressive hypoxia from 100% to 5% oxygen saturation. Biopotentials recorded from the water surrounding the fish corresponded to ventilation movements, and are thought to originate from the ventilatory musculature. Cardio-respiratory responses to temperature and dissolved oxygen follow the typical teleost pattern, with bradycardia, increased ventilation rate and reduced oxygen consumption occurring during hypoxia. However, ventilation rate did not increase at 15°C and below. Ventilation rate showed a slower response to increasing temperature (normoxic Q₁₀=1.39) than heart rate and oxygen consumption (normoxic Q₁₀=2.85 and 2.38).L. unicolor is unable to survive prolonged hypoxia by utilising anaerobic metabolism, but has a large gill surface area which presumably facilitates oxygen uptake in hypoxic environments. Periodic ventilation during normoxia in restingL. unicolor may improve ventilation efficiency by increasing the oxygen diffusion gradient across the gills.Abbreviations EBG electrobranchiogram - ECG electrocardiogram     

Behavioral and physiological responses of wild-caught European starlings (Sturnus vulgaris) to a minor, rapid change in ambient temperature

Free-ranging animals continuously adjust to changes in their environment. The stress response, typified by increases in heart rate and glucocorticoids, is an important physiological response regulating these changes. This study investigated heart rate, corticosterone and behavioral responses of European starlings (Sturnus vulgaris) to a rapid 30min decrease in temperature using an air-conditioning unit. Ten wild-caught birds were divided into pairs and exposed to four different trials. Three trials were controls: undisturbed birds; exposing birds to only the noise of the air-conditioning unit; and exposing the birds to 20°C airflow. For the experimental trial birds were exposed to 12°C air, leading to a rapid but modest 3°C drop in ambient temperature inside the birdcages. Heart rate and behavior were recorded before and during trials, while blood samples were collected before and after each trial for corticosterone measurements. Cooling, but none of the control conditions, induced an increase in heart rate and corticosterone. Additionally, cooling led to an increase in perch hopping and feather ruffling. We conclude that minor changes in temperature can elicit a stress response in European starlings, which suggests that this may be an important mechanism by which animals cope with minor rapid environmental changes.     

Artificial rain and cold wind act as stressors to captive molting and non-molting European starlings (Sturnus vulgaris)

Free-roaming animals continually cope with changes in their environment. One of the most unpredictable environmental phenomena is weather. Being able to respond to weather appropriately is crucial as it can be a threat to survival. The stress response, consisting of increases in heart rate and release of glucocorticoids, is an important mechanism by which animals cope with stressors. This study examined behavioral, heart rate, and corticosterone responses of captive European starlings (Sturnus vulgaris) to two aspects of weather mimicked under controlled conditions, a subtle (3 °C) decrease in temperature and a short, mild bout of rain. Both decreased temperature and exposure to rain elicited increases in heart rate and corticosterone in non-molting starlings. Molt is an important life history stage in birds that affects feather cover and may require a different response to weather-related stressors. We repeated the experiment in molting starlings and found increases in heart rate in response to rain and cold wind. However, the hypothalamic–pituitary–adrenal (HPA)-axis was suppressed during molt, as molting starlings did not increase corticosterone release in response to either stimulus. These data suggest these stimuli induce increased allostatic load in starlings, and that animals may adjust their response depending on the life-history stage.     

Nitric oxide mediates metabolism as well as respiratory and cardiac responses to hypoxia in the snail lymnaea stagnalis

Lymnaea stagnalis were exposed to hypoxic and chemical challenges while ventilation, heart rate and metabolism were monitored. Hypoxia increased ventilatory behavior, but this response was eliminated by immersion in 0.75 mM nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (7 NI). 7 NI also suppressed ventilatory behavior under normoxia. 10.0 mM L-arginine (ARG, the NOS substrate) increased ventilatory behavior under normoxia, but dampened the hypoxic response. The heart-rate response to NOS inhibition exhibited dose-dependent contradictory characteristics. Under both normoxia and hypoxia 0.25 mM 7 NI increased heart rate, while 0.75 mM 7 NI suppressed it. The effect of 0.50 mM 7 NI depended on whether normoxia or hypoxia was coincident; under normoxia 0.50 mM 7 NI increased heart rate, while under hypoxia this concentration suppressed heart rate. Exposure to ARG did not elicit dose-dependent contradictory responses. Heart rate increased when treated with 10.0 mM ARG under normoxia and hypoxia, while 1.0 mM ARG increased heart rate only under hypoxia. Metabolic responses to NOS inhibition also exhibited dose-dependent contradictory changes. V.O2 decreased over 60% in response to 0.75 mM 7 NI, and baseline V.O2 was restored when exposure ceased. In contrast, 0.25 mM 7 NI increased V.O2 10%, and the increase continued after exposure ceased. 0.50 mM 7 NI decreased V.O2 40%, but V.O2 increased when exposure ceased. ARG had only the effect of increasing V.O2, and only at 10.0 mM concentration. Based on these results and on NO's known role as a neuromodulator, we conclude that the cardio-respiratory responses to hypoxia are, in part, mediated by NO.     

Electroretinographic detection of human brain dopamine response to oral food stimulation

Objective:

The activity of dopamine‐dependent retinal signaling can be assessed using electroretinography. Response of this system to oral food stimulation might provide accessible insight into the brain dopamine response to oral stimuli as retinal dopamine concentration is dependent upon mid brain dopamine concentration was postulated.

Design and Methods:

Nine individuals had cone ERG (b wave) response to oral food stimulation and oral methylphenidate (MPH) administration measured on separate days, and completed self reported eating behavior questionnaires.

Results:

Significant and similar increases in b wave response to both stimuli (P = 0.012 and P = 0.042, MPH and food, respectively) and significant correlations of the food stimulated b wave amplitude with binge eating related behavior as measured by the Gormally Binge Eating Scale (r = 0.68, P = 0.044) and self‐reported trait hunger as measured by the Stunkard and Messick Three Factor Eating Questionnaire (r = 0.67, P = 0.048) were found.

Conclusion:

The significant increase in food stimulated dopamine dependent b wave amplitude and correlation with methylphenidate stimulated b wave amplitude suggest that ERG may offer a relatively inexpensive and accessible methodology for potentially assess dopaminergic responses to food and other externally applied stimuli that have been implicated in the pathogenesis of a number of human diseases.     

Performance characteristics of conditioned blood pressure elevations in the baboon

Operant conditioning of diastolic blood pressure elevation was accomplished in six baboons (Papio sp.) by a procedure using food delivery when diastolic pressure was maintained above a prespecified level, and shock delivery when diastolic pressure remained below that level. Data from steady-state performance indicated a rise in diastolic pressure by a median 22 mm Hg when the daily session was begun. Elevated levels of diastolic blood pressure and low shock frequencies were maintained throughout the 12-hour session. The frequency and duration of shifts in diastolic pressure to below criterion level were found to be variable during the first 1–2 hours but were stable throughout the remainder of the session. Heart rate had a phasic temporal pattern over the 12-hour session, characterized for most subjects by a rate increase at session onset followed by a rate decrease. Analysis of individual performance records showed that the blood pressure increases could occur without concomitant elevations in heart rate.This research was supported by grant No. 2R01HL17958-05 from the National Heart, Lung, and Blood Institute. The authors wish to thank J. V. Brady and I. Iversen for helpful editorial suggestions.     

Effects of various taste stimuli on heart rate in humans

Relationships between taste stimuli and heart rate were evaluated in 29 healthy university students. The test solutions were sucrose, NaCl, citric acid, quinine-HCl and monosodium glutamate (MSG). Heart rate increased by 7.1-13.6% for all the taste stimuli after use as compared with pre-stimuli values. The maximum increases in heart rate came approximately 25 s after the taste stimuli. After the increases, heart rate returned to pre-stimuli levels after between 80 and 100 s. Heart rate reached its maximum with citric acid. Recovery from the heart-rate increase was more delayed for quinine-HCl and MSG than for the other stimuli. Except for sucrose, increases in heart rate and the hedonic scale values of the taste solutions showed significant negative correlation. These findings show that the taste stimuli solutions increased the heart rate and that the increase differed with the concentration and taste solution used.     

Cardiovascular and ventilatory acclimatization induced by chronic intermittent hypoxia: a role for the carotid body in the pathophysiology of sleep apnea

Patients with obstructive sleep apnea (OSA) show augmented ventilatory, sympathetic and cardiovascular responses to hypoxia. The facilitatory effect of chronic intermittent hypoxia (CIH) on the hypoxic ventilatory response has been attributed to a potentiation of the carotid body (CB) chemosensory response to hypoxia. However, it is a matter of debate whether the effects induced by CIH on ventilatory responses to hypoxia are due to an enhanced CB activity. Recently, we studied the effects of short cyclic hypoxic episodes on cat cardiorespiratory reflexes, heart rate variability, and CB chemosensory activity. Cats were exposed to cyclic hypoxic episodes repeated during 8 hours for 4 days. Our results showed that CIH selectively enhanced ventilatory and carotid chemosensory responses to acute hypoxia. Exposure to CIH did not increase basal arterial pressure, heart rate, or their changes induced by acute hypoxia. However, the spectral analysis of heart rate variability of CIH cats showed a marked increase of the low/high frequency ratio and an increased variability in the low frequency band of heart rate variability, similar to what is observed in OSA patients. Thus, it is likely that the enhanced CB reactivity to hypoxia may contribute to the augmented ventilatory response to hypoxia.     

Balancing tissue perfusion demands: cardiovascular dynamics of Cancer magister during exposure to low salinity and hypoxia

Decapod crustaceans inhabit aquatic environments that are frequently subjected to changes in salinity and oxygen content. The physiological responses of decapod crustaceans to either salinity or hypoxia are well documented; however, there are many fewer reports on the physiological responses during exposure to these parameters in combination. We investigated the effects of simultaneous and sequential combinations of low salinity and hypoxia on the cardiovascular physiology of the Dungeness crab, Cancer magister. Heart rate, as well as haemolymph flow rates through the anterolateral, hepatic, sternal and posterior arteries were measured using a pulsed-Doppler flowmeter. Summation of flows allowed calculation of cardiac output and division of this by heart rate yielded stroke volume. When hypoxia and low salinity were encountered simultaneously, the observed changes in cardiac properties tended to be a mix of both factors. Hypoxia caused a bradycardia, whereas exposure to low salinity was associated with a tachycardia. However, the hypoxic conditions had the dominant effect on heart rate. Although hypoxia caused an increase in stroke volume of the heart, the low salinity had a more pronounced effect, causing an overall decrease in stroke volume. The patterns of haemolymph flow through the arterial system also varied when hypoxia and low salinity were offered together. The resulting responses were a mix of those resulting from exposure to either parameter alone. When low salinity and hypoxia were offered sequentially, the parameter experienced first tended to have the dominant effect on cardiac function and haemolymph flows. Low salinity exposure was associated with an increase in heart rate, a decrease in stroke volume and cardiac output, and a concomitant decrease in haemolymph flow rates. Subsequent exposure to hypoxic conditions caused a slight decrease in rate, but other cardiovascular variables were largely unaffected. In contrast, when low salinity followed acclimation to hypoxic conditions, apart from an increased heart rate, there were no other cardiovascular changes associated with the low salinity episode. The implications of these changes in cardiovascular dynamics are discussed in relation to physiological mechanisms and the ecology of decapod crustaceans, in hypoxic or low salinity environments.     

Respiratory pumping in Aplysia fasciata as part of an integrated defensive response to increases and decreases in seawater concentration

Much of the neural circuitry controlling respiratory pumping in Aplysia has been well characterized, but the function of this movement is incompletely understood. To gain insight into possible functions of respiratory pumping, responses were examined for a 40 min exposure to two stimuli that modulate the movement: 1) increase and 2) decrease in seawater concentration. Thresholds were present for both stimuli to affect respiratory pumping. Above threshold, there were graded increases in the number of pumps elicited. There were decrements in respiratory pump frequency as a function of time exposed to the stimulus. Increased respiratory pumping did not contribute to volume regulation in response to exposure to altered seawaters, but was associated with increased defensive responses, such as escape locomotion (swimming) and inking. In addition, head shock, a well-established noxious stimulus, elicited temporal patterns of respiratory pumping similar to those elicited by altered seawaters. The data indicate that in our experimental conditions, respiratory pumping is elicited as part of an integrated defensive response to noxious seawaters.     

Cardiorespiratory responses to hypoxia in intact and bilaterally vagotomized pigeons

Bilateral, cervical vagotomy in birds denervates, among other receptors, the carotid bodies. To test whether such neural section removes sensitivity to hypoxia, we measured respiratory, cardiovascular, and blood gas responses to hypoxia at 84-, 70-, and 49-Torr inspiratory O2 partial pressure (PIO2) in five pigeons with intact vagi and in five bilaterally, cervically vagotomized pigeons. Normoxic respiratory frequency (fresp) and expiratory flow rate (VE) were decreased after vagotomy. Intact pigeons showed large increases in VE in response to hypoxia, effected mostly by increases in fresp. VE also increased greatly in response to hypoxia in vagotomized pigeons, but increases were largely the result of tidal volume. O2 consumption, CO2 production, and respiratory exchange ratio increased slightly in all pigeons during hypoxia. Normoxic heart rate was greater after vagotomy; cardiac output increased in all pigeons in response to hypoxia, but stroke volume increased only in intact pigeons. During normoxia, arterial and mixed venous O2 partial pressure, O2 concentration, and pH were lower and arterial and mixed venous CO2 partial pressure was higher, after vagotomy. In all pigeons during hypoxia, arterial and mixed venous O2 and CO2 partial pressure and O2 concentration decreased and arterial and mixed venous pH increased; changes were roughly parallel in intact and vagotomized pigeons. The arteriovenous O2 concentration differences during normoxia and hypoxia were similar in all pigeons. We conclude that bilateral, cervical vagotomy in the pigeon causes hypoventilation and tachycardia during normoxia, but strong respiratory and cardiovascular responses to hypoxia are still present.     

Effects of 2.8-GHz microwaves on restrained and ketamine-anesthetized rats

Summary To compare the effects of ketamine anesthesia and mild restraint on microwave-induced thermal and cardiovascular changes, sixteen Fischer 344 rats were irradiated in two states:1) unanesthetized, restrained, and2) ketamine-anesthetized (150 mg/kg, I.M.). Individual animals were exposed in H orientation to far-field continuous-wave 2.8-GHz microwaves. Irradiation was conducted at a power density of 60 mW/cm² (whole-body average specific absorption rate of 14.4 W/kg) to cyclicly increase colonic temperature from 38.5 to 39.5° C. Colonic and subcutaneous temperatures, aortic blood pressure, and heart rate were continuously monitored. The time required for colonic temperature to increase 1° C was significantly longer in the anesthetized state; however, the time to return to baseline was similar under both conditions. Heart rate and blood pressure significantly increased during irradiation in the unanesthetized state, but remained virtually unchanged in the anesthetized state. The subcutaneous temperature increase during exposure was significantly greater in the anesthetized state. The differences in responses of anesthetized and mildly restrained animals should be considered when conducting experiments on thermoregulatory responses to microwave irradiation.     

Integration of autonomic and local mechanisms in regulating cardiovascular responses to heating and cooling in a reptile (<Emphasis Type="Italic">Crocodylus porosus</Emphasis>)

Reptiles change heart rate and blood flow patterns in response to heating and cooling, thereby decreasing the behavioural cost of thermoregulation. We tested the hypothesis that locally produced vasoactive substances, nitric oxide and prostaglandins, mediate the cardiovascular response of reptiles to heat. Heart rate and blood pressure were measured in eight crocodiles (Crocodylus porosus) during heating and cooling and while sequentially inhibiting nitric-oxide synthase and cyclooxygenase enzymes. Heart rate and blood pressure were significantly higher during heating than during cooling in all treatments. Power spectral density of heart rate and blood pressure increased significantly during heating and cooling compared to the preceding period of thermal equilibrium. Spectral density of heart rate in the high frequency band (0.19–0.70 Hz) was significantly greater during cooling in the saline treatment compared to when nitric-oxide synthase and cyclooxygenase enzymes were inhibited. Cross spectral analysis showed that changes in blood pressure preceded heart rate changes at low frequencies (<0.1 Hz) only. We conclude that the autonomic nervous system controls heart rate independently from blood pressure at higher frequencies while blood pressure changes determine heart rate at lower frequencies. Nitric oxide and prostaglandins do not control the characteristic heart rate hysteresis response to heat in C. porosus, although nitric oxide was important in buffering blood pressure against changes in heart rate during cooling, and inhibition caused a compensatory decrease in parasympathetic stimulation of the heart.     

Cardiorespiratory response to exercise in men repeatedly exposed to extreme altitude

The ventilatory and heart rate responses to exercise were studied in four experienced high-altitude climbers at sea level and during a 6-wk period above 4,500 m to discover whether their responses to hypoxia were similar to those of high-altitude natives. Comparison was made with results from four scientists who lacked their frequent exposure to extreme altitude. The climbers had greater Vo2max at sea level and altitude but similar ventilatory responses to increasing exercise. On acute hypoxia at sea level their ventilatory response was less than that of scientists. Their heart rate response did not differ from that of scientists at sea level, but with acclimatization the reduction in response was significantly greater. Alveolar gas concentrations were similar after acclimatization, but climbers achieved these changes more rapidly. The increase in hematocrit was similar in the two groups. It is concluded that these climbers, unlike high-altitude residents, have cardiorespiratory responses to exercise similar to those of other lowlanders except that their ventilatory response was lower and the reduction in their heart rate response was greater.     

Hardly hard-hearted: heart rate responses of incubating Northern Giant Petrels (Macronectes halli) to human disturbance on sub-Antarctic Marion Island

Guidelines for visitors to sub-Antarctic Marion Island recommend 15 and 100 m minimum approach distances for breeding Northern (Macronectes halli) and Southern (Macronectes giganteus) Giant Petrels, respectively. Using artificial eggs containing FM transmitters, we measured the heart rate responses of incubating Northern Giant Petrels to pedestrian approaches. The mean resting heart rate was 80 beats per minute. Heart rates increased upon the detection of a person approximately 40 m away, and continued to increase during the approach to 5 m. Maximum increases over resting heart rate in response to natural disturbances and human approach were 97 and 204%, respectively. Northern Giant Petrels appear at least as sensitive to human disturbance as their congenerics. While low-key disturbance is unlikely to affect this solitary breeder as severely as it would the colonial Southern Giant Petrel, improved protection from disturbance could be achieved by restricting human passage through breeding colonies of Northern Giant Petrels to defined paths.     

Examining the effect of hunger on responses to pathogen cues and novel foods

Although multiple leading papers in the behavioral immune system literature have proposed that food deprivation affects responses to pathogen cues, evidence supporting this proposition is scarce. Here, we report results from what we believe to be the most comprehensive test of the effects of hunger on responses to pathogen cues to date. Participants (N = 40) recruited from a Dutch university attended two experimental sessions, each following a 15-hour fast. One of the two sessions was conducted immediately after eating a standardized meal, and the other was conducted before eating that same standardized meal. In each session, participants rated 40 different images (i.e., images depicting food-related pathogen cues, food-unrelated pathogen cues, violence, positive stimuli, and neutral stimuli) on valence and arousal while their heart rate and skin conductance responses were recorded. They also indicated their willingness to eat 16 novel foods. Results did not reveal an effect of nutritional state on explicit ratings of and physiological reactions to food-related or food-unrelated pathogen cues. However, participants reported a greater willingness to eat novel foods when hungry than when sated. These results raise doubt regarding proposals that short-term changes in nutritional state influence responses to pathogen cues, but they suggest that these same changes increase willingness to eat novel foods.     

Heart rate variability responses to hypoxic and hypercapnic exposures in different mouse strains.

Heart rate variability (HRV) is a well-characterized, noninvasive means of assessing cardiac autonomic nervous system activity. This study examines the basic cardiac responses to hypoxic and hypercapnic challenges in seven strains of commonly used inbred mice (A/J, BALB/cJ, C3H/HeJ, C57BL/6J, CBA/J, DBA/2J, and FVB/J). Adult male mice, 8-12 wk of age, were chronically instrumented to a femoral artery catheter for the continuous measurement of systemic arterial blood pressure and heart rate. Mice were exposed to multiple 4-min periods of hypoxia (10% O2), hypercapnia (5% CO2), and combined hypoxia/hypercapnia (10% O2 + 5% CO2). HRV was derived from pulse intervals of the blood pressure tracings. Hypoxia induced increases in high-frequency HRV power and decreased low-frequency (LF) HRV power in most strains. Hypercapnia led to decreased high-frequency HRV power and increased LF HRV power in most strains. Strain differences were most notable in regard to the concomitant exposures of hypoxia and hypercapnia, with FVB/J mice mirroring their own response to hypercapnia alone, whereas CBA/J mice mirrored their own responses to hypoxia. As blood pressure is most likely the driving factor for heart rate changes via the baroreflex pathway, it is interesting that LF, considered to reflect cardiac sympathetic activity, was negatively correlated with heart rate, suggesting that LF changes are driven by baroreflex oscillation and not necessarily by absolute sympathetic or parasympathetic activity to the heart. These findings suggest that genetic background can influence the centrally mediated cardiovascular responses to basic hypoxic and hypercapnic challenges.     

Fluctuations in central and peripheral temperatures associated with feeding behavior in rats

We examined the pattern of temperature fluctuations in the nucleus accumbens (NAcc), temporal muscle, and skin, along with locomotion in food-deprived and nondeprived rats following the presentation of an open or closed food container and during subsequent eating or food-seeking behavior without eating. Although rats in food-deprived, quiet resting conditions had more than twofold lower spontaneous locomotion and lower temperature values than in nondeprived conditions, after presentation of a container, they consistently displayed food-seeking behavior, showing much larger and longer temperature changes. When the container was open, rats rapidly retrieved food and consumed it. Food consumption was preceded and accompanied by gradual increases in brain and muscle temperatures ( approximately 1.5 degrees C) and a weaker, delayed increase in skin temperature ( approximately 0.8 degrees C). All temperatures began to rapidly fall immediately after eating was completed, but NAcc and muscle temperatures returned to baseline after approximately 35 min. When the container was closed and rats were unable to obtain food, they continued food-seeking activity during the entire period of presentation. Similar to eating, this activity was preceded and accompanied by gradual temperature increases in the brain and muscle, which were somewhat smaller than those during eating ( approximately 1.2 degrees C), with no changes in skin temperature. In contrast to trials with eating, NAcc and muscle temperatures continued to increase for approximately 10 min after the container was removed from the cage and the rat continued food-seeking behavior, with a return to baselines after approximately 50 min. These temperature fluctuations are discussed with respect to alterations in metabolic brain activity associated with feeding behavior, depending upon deprivation state and food availability.     

What goes down must come up: symmetry in light-induced migration behaviour of Daphnia

During a short period of the year, Daphnia may perform a phenotypically induced diel vertical migration. For this to happen, light-induced swimming reactions must be enhanced both at dawn and at dusk. Enhanced swimming in response to light intensity increase can be elicited by fish-associated kairomone in the laboratory, if food is sufficiently available. However, during the light change at dusk the Daphnia are still in the hypolimnion, where no fish kairomone is present and both temperature and food availability is low. Still, what goes down must come up. This raises questions about how Daphnia tunes its light-induced swimming behaviour to prevailing conditions such that a normal diel vertical migration can be performed. We investigated the symmetry in behavioural mechanism underlying these diel vertical migrations in the hybrid Daphnia galeata × hyalina (Cladocera; Crustacea), with special interest for the environmental cues that are known to affect swimming in response to light increase. That is, we tested whether fish- associated kairomone, food availability, and temperature affected both swimming in response to light intensity increase and decrease similarly. We quantified swimming behaviour during a sequentially increased rate of light change. Vertical displacement velocity was measured and proved to be linearly related to the rate of the light change. The slope (PC) of the function depends on the value of the factors kairomone concentration, food availability, and temperature. The changes of the PC with kairomone concentration and with temperature were similar both at light intensity increases and decreases. The PC also increased with food concentration, although during light increases in a different way from during light intensity decreases. Low food availability inhibited swimming in response to light intensity increase, but enhanced swimming in response to light intensity decrease. Hence, ascent from the deep water layers with low food concentration at dusk is facilitated. These causal relations are part of a proximate decision-making mechanism which may help the individual Daphnia to tune migration to predation intensity and food availability.     

The effects of temperature on signalling in ocellar neurons of the desert locust, <Emphasis Type="Italic">Schistocerca gregaria</Emphasis>

In Schistocerca gregaria ocellar pathways, large second-order L-neurons use graded potentials to communicate signals from the ocellar retina to third-order neurons in the protocerebrum. A third-order neuron, DNI, converts graded potentials into axonal spikes that have been shown in experiments at room temperature to be sparse and precisely timed. I investigated effects of temperature changes that a locust normally experiences on these signals. With increased temperature, response latency decreases and frequency responses of the neurons increase. Both the graded potential responses in the two types of neuron and the spikes in DNI report greater detail about a fluctuating light stimulus. Over a rise from 22 to 35°C the power spectrum of the L-neuron response encompasses higher frequencies and its information capacity increases from about 600 to 1,700 bits/s. DNI generates spikes more often during a repeated stimulus but at all temperatures it reports rapid decreases in light rather than providing a continual measure of light intensity. Information rate carried by spike trains increases from about 50 to 185 bits/s. At warmer temperatures, increased performance by ocellar interneurons may contribute to improved aerobatic performance by delivering spikes earlier and in response to smaller, faster light stimuli.