Foster studied at the University of Bristol and graduated with a Bachelor of Science in Zoology in 1980. He also carried out postgraduate studies at the University of Bristol under the supervision of Brian Follett, and was awarded a PhD in 1984 for his thesis entitled An investigation of the extraretinal photoreceptors mediating photoperiodic induction in the Japanese quail.
While at the University of Virginia, Foster and Menaker performed experiments where the suprachiasmatic nucleus was tested by neural transplantation of donor's SCN to a recipient with an ablated SCN. In the experiment, the donor was a mutant strain of hamster with a shortened circadian period. The recipient was a wild-type hamster. Transplantation was done the other way around as well, with wild-type hamster as the donor and mutant strain hamster as the recipient. After the transplantation, the formerly wild-type hamster displayed a shortened period which resembled the mutant, and the mutant-strain hamster showed normal period. The SCN restored rhythm to arrhythmic recipients, which afterwards always exhibited the circadian period of the donor. This result led to the conclusion that the SCN is sufficient and necessary for mammalian circadian rhythms.
In 1991, Foster and his colleagues provided evidence that rods and cones are not necessary for entrainment of an animal to light. In this experiment, Foster gave light pulses to retinally degenerative mice. These mice were homozygous for the rd allele and were shown to have no rods in their retina. Only a few cones were found to remain in the retina. To study the effects of light entrainment, magnitude of phase shift of locomotor activity was measured. The results showed that both mice with normal retina and mice with degenerate retina showed similar entrainment patterns. Foster hypothesized that circadian photoreception occurs with a small number of cones without an outer layer or that an unrecognised class of photoreceptive cells are present. In 1999, Foster studied light entrainment on mice without cones or both rods and cones. Mice without cones or without both photoreceptive cells still entrained to light. Meanwhile, mice with eyes removed could not entrain to light. Foster concluded that rods and cones are unnecessary for entrainment to light, and that the murine eye contains additional photoreceptive cell types. Later studies showed that melanopsin expressing photoreceptive retinal ganglion cells were accountable for non-rod, non-cone entrainment to light.
Literary works
He is the co-author with writer and broadcaster Leon Kreitzman of two popular science books on circadian rhythms, Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing and Seasons of Life: The Biological Rhythms That Enable Living Things to Thrive and Survive. He has also co-written a book titled Sleep: a Very Short Introduction.
