Authors: Liesbet Ruytjens Janniko R Georgiadis Gert Holstege Hero P Wit Frans W J Albers Antoon T M Willemsen
Publish Date: 2007/08/17
Volume: 34, Issue: 12, Pages: 2073-2081
Abstract
We used PET to study cortical activation during auditory stimulation and found sex differences in the human primary auditory cortex PAC Regional cerebral blood flow rCBF was measured in 10 male and 10 female volunteers while listening to sounds music or white noise and during a baseline no auditory stimulationWe found a sex difference in activation of the left and right PAC when comparing music to noise The PAC was more activated by music than by noise in both men and women But this difference between the two stimuli was significantly higher in men than in women To investigate whether this difference could be attributed to either music or noise we compared both stimuli with the baseline and revealed that noise gave a significantly higher activation in the female PAC than in the male PAC Moreover the male group showed a deactivation in the right prefrontal cortex when comparing noise to the baseline which was not present in the female group Interestingly the auditory and prefrontal regions are anatomically and functionally linked and the prefrontal cortex is known to be engaged in auditory tasks that involve sustained or selective auditory attention Thus we hypothesize that differences in attention result in a different deactivation of the right prefrontal cortex which in turn modulates the activation of the PAC and thus explains the sex differences found in the activation of the PACPreviously investigators tried to relate sex differences in behaviour and cognition to differences in brain anatomy function or connectivity A welldocumented example of sex differences in the brain is the difference in overall brain size We now know that the size of the male brain is on average 8–10 larger than the female brain 1 2 3 It is also thought that compared to the female brain there is more hemispheric asymmetry in the anatomy of the male brain 4 5 6 7 which is supported by the finding that in the male brain functions are represented more unilaterally 8 9 10 11 12Spatial distribution of significant increases in brain activation in men and women when comparing the auditory processing of noise music and a baseline Activations are superimposed on an anatomical MRI template of SPM2 Clusters are significant at p 005 FDR corrected for multiple comparisons L=left hemisphere y = −20 and y = −6 means a coronal plane respectively 20 mm and 6 mm posterior to the anterior commissure z = 8 means a horizontal plane 8 mm dorsal to the anterior commissure z = −1 means a horizontal plane 1 mm ventral to the anterior commissure a Contrasting music with noise women showed activation in the secondary auditory areas only whereas men showed activation in both PAC and secondary auditory areas b Comparing music to the baseline both women and men showed bilateral activation in the PAC and secondary auditory areas c Comparing noise to the baseline women showed bilateral activation in the PAC In men on the other hand no significant activation was found The differences between men and women in a and c are significant see Table 2Functional sex differences in auditory processing are widely studied in the light of language Females depend less on their left hemisphere for language processing than males in some studies 22 whereas in other studies the opposite was found 23 24 or no sex difference could be detected 25 26 Whether a sex difference in language processing can be detected might depend on the nature of the task 10Sexbased influence on activation patterns in auditory regions is also found when manipulating the amount of background noise 27 and auditory working memory tasks induce different activation patterns in males and females 28 These studies suggest that combining men and women in auditory neuroimaging studies may obscure or bias resultsHowever most of these studies focus mainly on functional sex differences in higher order associative brain areas thereby ignoring possible sex differences in primary auditory cortices Previously a sex difference in activation of the PAC during lipreading was found 29 However it has not been investigated whether nonspeech sounds can induce different activity in the PAC in both sexes
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