Zeitgeber and circadian activity rhythms of cockroaches a system of unipolar coupled oscillators
Title:
Zeitgeber and circadian activity rhythms of cockroaches a system of unipolar coupled oscillators
Author:
Wiedenmann, Gottfried
Appeared in:
Biological rhythm research
Paging:
Volume 15 (1984) nr. 1 pages 69-80
Year:
1984-03
Contents:
Three different patterns were found in the locomotor activity rhythm of the cockroach Leucophaea maderae, when exposed to cycles of 12 h red light: 12 h dark (RD) at constant temperature: en trainment, relative coordination, and free-run. The different reactions were only weakly correlated with the energy ranges of the red light. Instead, the free-running period and the previous state of the rhythm were most decisive. Entrainment to RD occurred when the free-running period in constant conditions was close to 24 h (23.8±0.07h, SE), while animals showing shorter average period lengths in constant conditions (23.0±0.06 h or 23.0 h±0.11 h) exhibited in RD relative coordination or an unaffected free-run, respectively. Following stepwise reduction of the red light energy to 0.5 μW/cm2, rhythms remained entrained in all cases as long as they had been entrained before, and the RD cycle was not phaseshifted. After a shift, however, re-entrainment failed, even when the light energies were one log unit higher (5 μW/cm2). The results are consistent with properties of a system of unilaterally coupled non-linear oscillators: the circadian rhythm reacts to RD like a driven self-sustained pacemaker does, which is weakly coupled to a forcing oscillation.
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