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They said the separate "physiological pathway" for this chronic type of pain meant it could now be a target for future therapies.

But we can’t do that because of the physiological and addictive circuits — they stand in the way.

At this time of year, trees are enter into their leaf expansion phase - a process that demands substantial physiological resources, including water.

“That experience was quite interesting because I had never had a physiological feeling like that before.”

Such decay was "not a disease and not a cause for concern" but "a normal, healthy kind of part of the trees' physiological development", said Dr Pyne.