Imaging modalities fMRI

The results of the RREP, PET, and fMRl studies indicate common areas are activated by multiple respiratory modalities, suggesting convergent neural pathways for respiratory perception that can lead to specific respiratory sensations. The differences in brain activations with the different respiratory sensory modalities are likely due to the afferent systems activated. Each respiratory sensory modality has a unique convergent and divergent afferent input to the central nervous system and a unique temporal pattern of afferent activity. Despite well-known afferent responses to respiratory stimuli, it remains unknown which of the fMRI- and PET-imaged activated central neural structures are essential to produce specific respiratory sensations. 

Nowinski et al. 1997 Woods et al. 1999 Nowinski and Thirunavuukarasuu 2000 Rasser et al. 2005), allowing for further research into the relationship between function and anatomical structure (Nowinski and Thirunavuukarasuu 2000 Thottakara et al. 2006). These atlases vary from simple affine transformation systems which assume that the brain is a rigid structure to more sophisticated systems which apply a low order non-affine warp in order to improve fitting of the data to the atlas. In practice these atlases are extremely useful for the approximate identification of cortical areas in clinical patients and on images from modalities where anatomical content is poor, such as isotope investigations or fMRI (Figs. 8.17 and 8.18). 

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