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HORMONES INFLUENCE WHICH BRAIN AREAS ARE ACTIVATED
However, researchers into the workings of the brain from the universities of Cologne and Bonn have now discovered that women use the areas in both cerebral hemispheres at particular periods of the menstrual cycle. Yet their linguistic faculties remain unimpaired. By contrast, in men the left-hand Wernicke's area, with few exceptions, is always responsible for speech comprehension. Researchers in the team led by Dr. Guillén Fernández from the Bonn Epileptology Clinic, who is currently also doing research at the Nijmegen Centre for Cognitive Neuroimaging, studied twelve healthy women between 22 and 34 years of age by using functional magnetic resonance imaging. This method enables researchers to detect changes in the blood supply within the brain; regions which are well supplied with blood are usually particularly active. 'In the Epileptology Clinic, for example, this is a routine method used to localise the speech areas before brain operations,' Dr. Fernández explains. Even today, some forms of epilepsy still cannot be treated by using medication. In these cases doctors try to surgically remove the cell region in the brain where the epileptic attacks originate. The diseased cells are often in one of the two temporal lobes, occasionally therefore where Wernicke's area is situated. One false incision can thus have devastating effects. 'In order to identify the speech areas, we show our patients a series of word pairs; they have to decide whether these are synonyms or not. At the same time, by using functional magnetic resonance imaging, we observe which areas of the brain are activated while they are completing this task.' The researchers then decided to also use this method to examine the effects of hormones on the brain. Other studies had shown that the natural fluctuations in hormone activity during the menstrual cycle have an effect on women's mood and spatial perception. The test persons were asked to decide whether 180 pairs of nouns were synonyms or not within the space of four seconds per pair. During the test the researchers recorded which areas of the brain were active in the test persons. The women had to do the test once during menstruation, during this period the steroid hormone levels are especially low. A second test took place during what is known as the midluteal phase a few days after ovulation, i.e. at a time when the concentration of the steroid hormones progesterone and oestrogen reaches a maximum. 'During menstruation the test persons mainly used the left-hand Wernicke's area; however, in the midluteal phase the corresponding areas of both the left-hand and right-hand sides of the temporal lobe were used,' is how Dr. Fernández summarises the findings. Areas of the brain which are involved in the perception of meaningless sequences of letters are unaffected by the fluctuations in hormone levels: this is the conclusion reached by the research team when they presented 180 pairs of sequences of letters to their test persons. 90 of these pairs were identical, the other 90 only differed by one letter; the test persons were required to decide within four seconds which of the sequences were the same. In this test there was no difference in the pattern of activity during menstruation and the midluteal phase. Incidentally, the research team did not notice any link between the linguistic abilities of their test persons and the phase of the cycle: the scores of the twelve women in these two tests were always 95 per cent, irrespective of the hormone level.
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