Mustached bats orient and find insects by emitting ultrasonic pulses and analyzing the returning echoes. Neurons in the Doppler-shifted constant-frequency (DSCF) and frequency-modulated (FM-FM) areas of the auditory cortex form maps of echo frequency (target velocity) and echo delay (target range), respectively. Bats were trained to discriminate changes in echo frequency or delay, and then these areas were selectively inactivated with muscimol. Inactivation of the DSCF area disrupted frequency but not delay discriminations; inactivation of the FM-FM area disrupted delay but not frequency discriminations. Thus, focal inactivation of specific cortical maps produces specific disruptions in the perception of biosonar signals.

1. The biosonar signal (pulse) of the mustached bat, Pteronotus parnellii parnellii, has four harmonics (H1-4), each consisting of a long constant-frequency component (CF1-4) followed by a short frequency-modulated component (FM1-4). As the bat approaches a target, it systematically modifies its pulses to optimize the extraction of information from the echoes. These behavioral responses include 1) Doppler-shift (DS) compensation in which the bat adjusts the frequency of its pulses to correct for the DS in the echoes. This maintains the echo CF2 at a frequency to which the bat's cochlea is very sharply tuned, slightly above the CF2 frequency of the bat's pulses when it is at rest (Frest, approximately 61 kHz); 2) echo intensity compensation, in which the bat lowers its pulse intensity as it approaches a large target, thus maintaining the echo intensity within a suitable range for auditory processing; and 3) and 4) duration and rate adjustments, in which the bat first increases its pulse duration to facilitate target identification, then shortens its pulse duration while increasing its pulse rate to facilitate target analysis. 2. We examined these responses, especially DS compensation, by swinging bats on a pendulum toward a large target over a distance of 3.6 m. Eight bats were given 15-30 swings per day for 6-25 days. 1) On 97% of all swings the bats showed strong DS compensation as the pendulum approached the target. They did not show DS compensation on the backswing. 2) On 40-50% of all swings, the bats clearly displayed the other responses. The bats typically increased their pulse intensity a small amount early in the pendulum swing, then decreased pulse intensity by as much as 18 dB as the target was more closely approached. They increased their pulse intensity during the backswing. 3) Pulse duration increased from approximately 20 to 23 ms early in the forward swing, decreased to approximately 18 ms as the target was more closely approached, and then increased to 20 ms by the end of the backswing. 4) The instantaneous repetition rate increased from approximately 17 pulses/s at the start of the forward swing to approximately 28 pulses/s near the target, then decreased to approximately 10 pulses/s by the end of the backswing. Pulses usually occurred in trains of 1-2 pulses, with longer trains occasionally occurring near the target. 3. The maximum DS on the pendulum was 1.34 kHz, and the maximum DS compensation was 146 +/- 98 (SD) Hz less than this value.(ABSTRACT TRUNCATED AT 400 WORDS)

The Rescorla-Wagner model of conditioning implies that, if 2 conditionedstimulus (CS) elements are independently conditioned to asymptote and then compounded, reinforcement of the compound should reduce the conditioned strength of each element. Further, the more salient element should lose more strength and should ultimately show less conditioned strength than the less salient element. Four groups of rats in a conditioned emotional response procedure provided 2 independent tests of this deduction at different levels of CS salience. The data in each case appeared consistent with the model's prediction, significantly so in one case. The data in other aspects confirmed deductions drawn from the model.

Background Few studies have examined how developing obesity in early adulthood affects the course of asthma. Objective We analyzed lung function and asthma impairment and risk among non-obese children with asthma, comparing those who were obese in young adulthood to those who remained non-obese. Methods Post-hoc analysis of 771 subjects with mild-moderate asthma who were not obese (pediatric definition, body mass index (BMI) <95th percentile) when enrolled in the Childhood Asthma Management Program at ages 5–12 years. Subjects were then followed to age ≥ 20 years. For visits at ages ≥ 20 years, spirometry values as percent predicted and recent asthma symptom scores and prednisone exposure were compared between 579 subjects who were non-obese at all visits and 151 who obese (adult definition of BMI ≥ 30 kg/m2) on at least one visit (median number of visits when obese = 4, IQR 2–7). Results Compared to participants who were non-obese (BMI 23.4 ± 2.6 kg/m2), those who became obese (BMI 31.5 ± 3.8 kg/m2) had significant decreases in FEV1/FVC (p<0.0003) and FEV1 (p = 0.001), without differences in FVC (p=0.15) during visits at ages ≥ 20 years. For each unit increase of BMI, FEV1 percent predicted decreased by 0.29 (p=0.0009). The relationship between BMI and lung function was not confounded by sex or BMI at baseline. Asthma impairment (symptom scores) and risk (prednisone use) did not differ between the two groups. Conclusion Becoming obese in early adulthood was associated with increased airway obstruction, without impact on asthma impairment or risk.

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