Sustained BOLD and theta activity in auditory cortex are related to slow 4 stimulus fluctuations rather than to pitch 5

Iris Steinmann: designed study, acquired data, performed data analysis, and wrote 20 manuscript 21 Alexander Gutschalk: designed study, supervised data analysis, and wrote manuscript 22 23 Running head: Stimulus fluctuations and pitch in auditory cortex 24 25 Abstract 26 Human fMRI and MEG studies indicate a pitch specific area in lateral Heschl's gyrus. Single-27 cell recordings in monkey suggest that sustained-firing, pitch-specific neurons are located 28 lateral to primary auditory cortex. We reevaluated if pitch-strength contrasts reveal sustained 29 pitch-specific responses in human auditory cortex. Sustained BOLD activity in auditory cortex 30 was found for iterated rippled noise (versus noise or silence) but not for regular click trains 31 (versus jittered click trains or silence). In contrast, iterated rippled noise and click trains 32 produced similar pitch responses in MEG. Subsequently performed time-frequency analysis of 33 the MEG data suggested that the dissociation of cortical BOLD activity between iterated 34 rippled noise and click trains is related to theta-band activity. It appears that both sustained 35 BOLD and theta activity are associated with slow non-pitch specific stimulus fluctuations. 36 BOLD activity in the inferior colliculus was sustained for both stimulus types and varied 37 neither with pitch strength nor with the presence of slow stimulus fluctuations. These results 38 suggest that BOLD activity in auditory cortex is much more sensitive to slow stimulus 39 fluctuations than to constant pitch, compromising the accessibility of the latter. In contrast, 40 pitch-related activity in MEG can easily be separated from theta-band activity related to slow 41 stimulus fluctuations.