The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has operated since 19 December 1999 from NASA's Terra Earth-orbiting, sun-synchronous satellite. The Temperature–Emissivity ...Separation (TES) algorithm is used to calculate surface temperature and emissivity standard products, predicted to be within +1.5
K and +0.015 of correct values, respectively. Analyses of time sequences of ASTER images showing validation sites at Lake Tahoe, California, the Salton Sea, California, Railroad Valley Nevada, and the island of Hawaiʻi demonstrate that TES generally performs within these limits. The validation experiments also demonstrate that, under unusual atmospheric conditions of anomalously high humidity or spatial variability, atmospheric compensation can be incomplete and errors in temperature and emissivity images can be larger than anticipated.
Background:
Goal-directed attention involves the selective processing of behaviorally relevant sensory information. This selective processing is thought to be supported by glutamatergic and ...noradrenergic systems. Pharmacotherapies that simultaneously target these systems could therefore be effective treatments for impaired attention.
Aims:
We first tested an N-methyl-D-aspartate (NMDA) receptor co-agonist (D-serine) for effects on attention (processing speed and attentional lapses). NMDA receptor activation is thought to support noradrenergic effects on sensory processing; therefore, we tested a combination treatment comprising D-serine and a norepinephrine reuptake inhibitor (atomoxetine).
Methods:
D-serine was first tested in rats performing a two-choice visuospatial discrimination task. Combination treatments comprising relatively low doses of D-serine and atomoxetine were then tested in a separate group.
Results:
In experiment 1, D-serine reduced the skew of initiation time (IT) distributions (IT devmode) at the highest dose tested (300 mg/kg). In experiment 2, low-dose D-serine (125 mg/kg) had no effect, while low-dose atomoxetine (0.3 mg/kg) reduced IT devmode and slowed movement speed. Importantly, the combination of these relatively low doses of D-serine and atomoxetine reduced IT devmode more than either drug alone without further slowing movement speed.
Conclusions:
IT devmode is thought to reflect attentional lapses; therefore, D-serine’s effects on IT devmode suggest that NMDA receptors are involved in the preparatory deployment of attention. Greater effects following a combination of D-serine and atomoxetine suggest that preparatory attention can be facilitated by targeting glutamatergic and noradrenergic systems simultaneously. These results could inform the development of improved treatments for individuals with ADHD who experience abnormally high attentional lapses.
Rationale
Methamphetamine (METH) induces hyperthermia in warm and hypothermia in cool environments. Our first goal was to further study the role of ambient temperature in METH’s effect on core ...temperature in rats. Previously, these effects were primarily demonstrated in high doses; we extended this investigation to the low-dose range (1 mg/kg METH). Our second goal was to identify the role of the D2 receptor in METH’s effects in cool ambient temperatures.
Method
Rats received METH (saline, 1, 5, and 10 mg/kg), raclopride (saline, 0.3, 0.6, and 1.2 mg/kg), or a combination (all doses of raclopride combined with 10 mg/kg METH). Treatments occurred in ambient temperatures of 18, 24, or 30 °C.
Results and conclusions
Consistent with prior research, 5 and 10 mg/kg METH caused hyperthermia or hypothermia in a dose- and ambient temperature-dependent manner (60 min after METH). In contrast, 1 mg/kg produced similar levels of hyperthermia at all ambient temperatures. These findings suggest that a threshold METH dose exists; below this dose, METH still changes core temperature, but CNS control over temperature regulation is left intact. In our experiments regarding D2 blockade, raclopride decreased METH-induced core temperature at 30 and 24 °C (60 min after METH), consistent with previous findings. We extended these findings by demonstrating that in a cool ambient temperature (18 °C), raclopride pretreatment also lowered the core temperature response to METH. Although the D2 receptor is known to mediate hypothermia, the combination of METH and D2 blockade suggests a complex mediation of the core temperature response, perhaps involving neurotransmitter interactions.
Rationale
Norepinephrine (NE) is involved in the control of sustained attention. Studies of sustained attention in humans include measures of reaction time (RT) and RT variability (RTV). The present ...study tested the role of NE using components of the RT distribution in rats in a manner thought to be similar to human studies of RTV.
Objectives
This study tested the effects of increased synaptic NE (atomoxetine (ATX)) and α-2 receptor binding (guanfacine) on attentional lapses in rats.
Methods
Male Sprague-Dawley rats (
n
= 20) were trained and tested in a two-choice RT task (2CRTT). Atomoxetine dose (saline, 0.1, 0.5, 1.0 mg/kg, i.p.), guanfacine dose (saline, 0.01, 0.1, 0.3 mg/kg, i.p.), and distractors were manipulated in three experiments. RT was divided into initiation time (IT) and movement time (MT). Analyses of distribution mode (peak) and deviation from the mode (skew) were then performed.
Results
ATX and guanfacine had no effect on IT mode, reduced IT devmode, and increased MT mode. When distractors were introduced, ATX again improved devmode, but a lack of interaction between ATX and distractor indicated that ATX did not prevent distractor-induced impairments.
Conclusions
IT devmode is a measure of distribution skew thought to reflect lapses of attention. The effects of ATX on IT devmode suggest that increased synaptic NE reduces attentional lapses. These findings are consistent with human reports of reduced RTV after ATX administration. The same pattern of results with guanfacine suggests that the effects of increased NE are due in part to binding at α-2 noradrenergic receptors.
Moderate doses of d-amphetamine (given both acutely and chronically) have been shown to decrease impulsivity in children with attention deficit hyperactivity disorder (ADHD) and to improve attention ...and learning in normal adults. In contrast, chronic doses of methamphetamine (METH) in drug abusers have been associated with increased impulsivity, and impairments in learning and attention.
We report the effects of METH on an animal model of impulsive behavior.
Rats were tested using the adjusting amount (AdjAmt) procedure in which the animals choose between a delayed fixed (large) amount of water and an immediate adjusting (small) amount of water. In the acute METH study, rats were given a single dose of 0.5, 1.0, 2.0, and 4.0 mg/kg METH or saline 30 min before testing. In the chronic METH study, we determined the effects of the 4.0 mg/kg dose of METH injected chronically 1 h after behavioral testing for 14 days. Thus the rats were tested using the AdjAmt procedure 22 h after injections of METH or saline.
After 0.5, 1.0 and 2.0 mg/kg METH, the rats valued the delayed large rewards more than after saline, indicating that the METH decreased impulsiveness. At the 4.0 mg/kg dose, the rats failed to respond. Rats treated repeatedly with the post-session large behaviorally disruptive dose of METH valued the delayed large rewards less than the saline-treated rats, indicating that this dosing regimen of METH increased impulsiveness.
In these experiments, the rats became less impulsive after acute non-disruptive doses of pre-session METH, whereas they became more impulsive after receiving repeated post-session injections of a dose that was behaviorally disruptive when administered acutely.
Abstract Methamphetamine (METH) changes core temperature and induces behavioral activation. Behavioral activation is also known to change core temperature. The purpose of this report was to 1.) ...evaluate the extent to which the behavioral activation induced by METH showed a temporal relationship to METH-induced hyperthermia; and 2.) describe the temporal pattern of METH-induced hyperthermia over an extended dose range. Rats were treated with saline or METH (0.5–10.0 mg/kg) in computer-controlled chambers with ambient temperature maintained at 24 °C. Continuous telemetric core temperature measurements were made during a 7 h test period. Behavioral observations were made once every 15 min using an 11-point scale ranging from 0 (quiet awake) to 10 (focused licking or biting). The onset of METH-induced behavioral activation occurred at 15–30 min after treatment for all doses and preceded core temperature increases; the onset of METH-induced hyperthermia ranged from 45 min post-treatment to 120 min post-treatment. This behavior-temperature delay was 15–30 min at the lowest (0.5 and 1.0 mg/kg) and the highest (7.0, 8.0, and 10.0 mg/kg) doses tested; the delay was increased between 1.0 and 4.0 mg/kg METH (105 min delay at 4.0 mg/kg) and then decreased again from 4.0 to 10.0 mg/kg. The strongest relationship between core temperature and behavioral activation occurred at 180 min post-treatment. These data suggest that factors other than behavior are primarily responsible for the observed core temperature effects during the initial post-treatment period (60 min peak); possible effects from movement are masked. For the latter post-treatment period (180 min peak) the stronger relationship between temperature and behavior suggests a role for movement in METH-induced hyperthermia.
Four time-sequential Landsat Thematic Mapper (TM) images of an area of Amazon forest, pasture, and second growth near Manaus, Brazil were classified according to dominant ground cover, using a new ...technique based on fractions of spectral endmembers. A simple four-endmember model consisting of reflectance spectra of green vegetation, nonphotosynthetic vegetation, soil, and shade was applied to all four images. Fractions of endmembers were used to define seven categories, each of which consisted of one or more classes of ground cover, where class names were based on field observations. Endmember fractions varied over time for many pixels, reflecting processes operating on the ground such as felling of forest, or regrowth of vegetation in previously cleared areas. Changes in classes over time were used to establish superclasses which grouped pixels having common histories. Sources of classification error were evaluated, including system noise, endmember variability, and low spectral contrast. Field work during each of the four years showed consistently high accuracy in per-image classification. Classification accuracy in any one year was improved by considering the multiyear context. Although the method was tested in the Amazon basin, the results suggest that endmember classification may be generally useful for comparing multispectral images in space and time.
Rationale
Stimulants such as methamphetamine (METH) alter core temperature in a manner that is dependent on ambient temperature and that shows tolerance after chronic use. Our objectives were to (1) ...determine whether tolerance to METH-induced hyperthermia was a consequence of neurotoxicity to dopamine or serotonin and (2) determine the relationship between ambient temperature and chronic treatment on the METH-induced temperature response.
Materials and methods
Rats were treated with 1.0, 5.0, or 10.0 mg/kg METH at 24°C (experiment 1) or treated with 5.0 mg/kg METH at 20°C, 24°C, or 28°C (experiment 2). Treatment occurred for 12 days, and temperature measurements were made once per minute telemetrically during 7-h sessions in computer-regulated environments.
Results
Peak increases in core temperature occurred at 60 min post-treatment for the 1.0 and 10.0 mg/kg doses, and at 180 min for the 5.0 mg/kg dose. Tolerance-like effects were seen with chronic 5.0 (mixed results) and 10.0 mg/kg METH in the absence of dopamine or serotonin depletions measured 2 weeks after the completion of treatment. After 5.0 mg/kg METH, variations in ambient temperature resulted in an early flexible change in core temperature (phase 1) (hyperthermia at 28° and hypothermia at 20°) and a later inflexible hyperthermia (phase 2).
Conclusions
The results suggest that (1) the peak effect of different doses of METH occurs at different times (24°), (2) the diminished temperature response with chronic METH treatment was not associated with long-term dopamine and serotonin depletions, and (3) a two-phase temperature response to METH may reflect two independent mechanisms.
We identified stages of regrowth in replanted clearcuts in Douglas-fir/western hemlock forests in the Gifford Pinchot National Forest, southern Washington, USA, using a simple four-endmember ...constrained linear spectral mixing model applied to a multispectral Landsat Thematic Mapper image in order to separate and quantify spectral contributions from significant scene components. Spectral unmixing produces images of the fractional amount of the spectral endmembers, which were green vegetation, nonphotosynthetic vegetation, soil and “shade,” which includes topographic shading and shadows. Changes in endmember fractions correspond to changes in surface composition (as viewed from above). Unresolved shadows comprise the primary indicator of canopy structure and hence, regrowth stage. To isolate shadows, shading predicted from a digital elevation model was removed from the image before mixture analysis. As stands regrow, the surface cover shifts from initial high proportion of slash and exposed soil, and low proportions of green vegetation and shadows, to low fractions of stems and soil with high fractions of green vegetation and shadows. This shift in surface composition defines a regrowth trend in an endmember fraction data space. Projection of data onto this line allows estimation of structural stage and stand age, and provides a framework for remote mapping and monitoring of forest regrowth. Field analysis of 495 forest stands, representing stand structural stages ranging from newly replanted cuts to stands greater than 250 years in age, was used to assess the accuracy and precision of predicted structural stages and stand ages. The spectral unmixing approach can be used to evaluate and monitor forest regrowth quickly over large areas of the Pacific Northwest forests, and is extendible to mapping basic vegetation community type as well as structural stage.
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