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- Kozlov, Alexander K., et al.
(author)
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Mechanisms for lateral turns in lamprey in response to descending unilateral commands : a modeling study
- 2002
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In: Biological Cybernetics. - : Springer Science and Business Media LLC. - 0340-1200 .- 1432-0770. ; 86:1, s. 1-14
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Journal article (peer-reviewed)abstract
- Straight locomotion in the lamprey is, at the segmental level, characterized by alternating bursts of motor activity with equal duration and spike frequency on the left and the right sides of the body. Lateral turns are characterized by three main changes in this pattern: (1) in the turn cycle, the spike frequency, burst duration, and burst proportion (burst duration/cycle duration) increase on the turning side; (2) the cycle duration increases in both the turn cycle and the succeeding cycle; and (3) in the cycle succeeding the turn cycle, the burst duration increases on the non-turning side (rebound). We investigated mechanisms for the generation of turns in single-segment models of the lamprey locomotor spinal network. Activation of crossing inhibitory neurons proved a sufficient mechanism to explain all three changes in the locomotor rhythm during a fictive turn. Increased activation of these cells inhibits the activity of the opposite side during the prolonged burst of the turn cycle, and slows down the locomotor rhythm. Secondly, this activation of the crossing inhibitory neurons is accompanied by an increased calcium influx into the cells. This gives a suppressed activity on the turning side and a contralateral rebound after the turn, through activation of calcium-dependent potassium channels.
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| 3. |
- Ericson, Per G P, 1956-, et al.
(author)
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The earliest record of house sparrows (Passer domesticus) in northern Europe
- 1997
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In: Journal of Archaeological Science. - : Elsevier BV. - 0305-4403 .- 1095-9238. ; 24:2, s. 183-190
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Journal article (peer-reviewed)abstract
- Remains of the house sparrow (Passer domesticus) recovered from a late Bronze Age (1200-800 sc) settlement in central Sweden are described. The house sparrow is conspicuously rare in prehistoric Europe, and this record constitutes the earliest from the northern part. The find predates the introduction of domestic fowl (Gallus gallus) to Sweden, a species with which the house sparrow has been assumed to be spread simultaneously. Instead, it is here suggested that house sparrows most likely spread over Europe along with the horse Equus caballus. (C) 1997 Academic Press Limited
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