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- Decety, Jean, et al.
(författare)
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The cerebellum participates in mental activity : tomographic measurements of regional cerebral blood flow
- 1990
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Ingår i: Brain Research. - 0006-8993 .- 1872-6240. ; 535:2, s. 313-317
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Tidskriftsartikel (refereegranskat)abstract
- Measurements in man of regional cerebral blood flow (rCBF) have demonstrated a number of cortical and subcortical events coupled to sensory stimulation or motor performance. It has also been shown that local activity changes take place in the cortex during 'pure' mental activity such as motor imagery (unaccompanied by sensory input or motor output). Thus, our group has previously shown that imagination of hand movements gives predominantly a frontal cortical rCBF activation while the corresponding hand movement activates the rolandic hand area mainly. In this paper we report tomographic rCBF measurements with a 133-Xenon SPECT technique during imagined tennis movements and silent counting. Both procedures gave rise to a significant cerebellar activation in addition to cortical rCBF changes. Apparently, the cerebellum may participate in pure mental activity. It possibly plays a role for the temporal organization of neuronal events related to cognition.
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- Elmberg, Johan, 1960-
(författare)
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Long-term survival, length of breeding season, and operational sex ratio in a boreal population of common frogs, Rana temporaria L.
- 1990
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. - 0008-4301 ; 68:1, s. 121-127
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Tidskriftsartikel (refereegranskat)abstract
- A population of individually marked adult Rana temporaria was studied during the breeding season in 1979–1988 in east-central Sweden. Annual return rate averaged 31% (range 16–51%) in males and 16% (range 5–33%) in females. Return rate was not size dependent but increased with every successful previous hibernation, indicating an increased survival rate with age. Return rate was not correlated with winter harshness. Once adult, males had on average 1.5 (maximum 6) seasons with the possibility of reproducing. Corresponding values for females were 1.4 and 4. Mean length of the breeding season was 20 (SD = 2) days. Calling generally started at water temperatures below 3 °C. The lowest spawning temperature was 1 °C. Average temperatures at spawning onset and peak spawning were 5 and 6 °C, respectively. Large males tended to arrive earlier at the pond than small males. Males arrived earlier and stayed longer than did females. The overall population sex ratio was close to unity. The operational sex ratio (OSR) varied during the breeding season, averaging 0.54 (one female to two males). No male was observed to mate more than once per season. I argue that survival selection is more important to male lifetime mating success than is competition in the breeding pond (sexual selection as affected by OSR and length of the breeding season).
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- Lacoursière, Jean O., 1958-, et al.
(författare)
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A small flume for studying the influence of hydrodynamic factors on benthic invertebrate behaviour
- 1990
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Ingår i: Journal of The North American Benthological Society. - 0887-3593 .- 1937-237X. ; 9:4, s. 358-367
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Tidskriftsartikel (refereegranskat)abstract
- A compact, versatile flume for studying the influence of hydrodynamic factors on the behaviour of benthic invertebrates is described. A range of lotic micro-environments can be simulated under controlled and replicable conditions by tailoring the velocity profile at the entrance of the test section. A specially designed diffuser composed of an array of adjustable horizontal rods allows tailored flow (e.g., zone of high shear stress, adjustable velocity gradient and turbulence level) to which organisms can be exposed. Water velocities of up to a maximum of 81.5 plus or minus 0.6 cm/s, with a turbulence intensity of 0.8% can be achieved. Simultaneous observations of flow and organism behaviours can be done by means of standard flow visualization techniques. Compact (72 cm long x 22 cm high x 10 cm wide; volume 10 L) and easily transportable, this flume is an inexpensive "desk-top" version of larger, more bulky systems, without sacrifice of performance and versatility.
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