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Titolo:
CONTRAST GAIN, SIGNAL-TO-NOISE RATIO, AND LINEARITY IN LIGHT-ADAPTED BLOWFLY PHOTORECEPTORS
Autore:
JUUSOLA M; KOUVALAINEN E; JARVILEHTO M; WECKSTROM M;
Indirizzi:
UNIV OULU,DEPT PHYSIOL,KAJAANINTIE 52 A SF-90220 OULU FINLAND
Titolo Testata:
The Journal of general physiology
fascicolo: 3, volume: 104, anno: 1994,
pagine: 593 - 621
SICI:
0022-1295(1994)104:3<593:CGSRAL>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIMULUS VENTRAL PHOTORECEPTORS; DROSOPHILA PHOTORECEPTORS; CALLIPHORA-ERYTHROCEPHALA; INOSITOL TRISPHOSPHATE; INTRACELLULAR CALCIUM; FOURIER-TRANSFORM; COMPOUND EYE; ADAPTATION; FLY; EXCITATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
66
Recensione:
Indirizzi per estratti:
Citazione:
M. Juusola et al., "CONTRAST GAIN, SIGNAL-TO-NOISE RATIO, AND LINEARITY IN LIGHT-ADAPTED BLOWFLY PHOTORECEPTORS", The Journal of general physiology, 104(3), 1994, pp. 593-621

Abstract

Response properties of short-type (R1-6) photoreceptors of the blowfly (Calliphora vicina) were investigated with intracellular recordings using repeated sequences of pseudorandomly modulated light contrast stimuli at adapting backgrounds covering 5 log intensity units. The resulting voltage responses were used to determine the effects of adaptational regulation on signal-to-noise ratios (SNR), signal induced noise,contrast gain, linearity and the dead time in phototransduction. In light adaptation the SNR of the photoreceptors improved more than 100-fold due to (a) increased photoreceptor voltage responses to a contraststimulus and (b) reduction of voltage noise at high intensity backgrounds. In the frequency domain the SNR was attenuated in low frequencies with an increase in the middle and high frequency ranges. A pseudorandom contrast stimulus by itself did not produce any additional noise. The contrast gain of the :photoreceptor frequency responses increasedwith mean illumination and the gain was best fitted with a model consisting of two second order and one double pole of first order. The coherence function (a normalized measure of linearity and SNR) of the frequency responses demonstrated that the photoreceptors responded linearly (from 1 to 150 Hz) to the contrast stimuli even under fairly dim conditions. The theoretically derived and the recorded phase functions were used to calculate phototransduction dead time, which decreased in light adaptation from similar to 5-2.5 ms. This analysis suggests thatthe ability of fly photoreceptors to maintain linear performance under dynamic stimulation conditions results from the high early gain followed by delayed compressive feed-back mechanisms.

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Documento generato il 05/12/20 alle ore 20:07:29