NeuroImage
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Cognitive neuroimaging studies typically require fast whole brain image acquisition with maximal sensitivity to small BOLD signal changes. To increase the sensitivity, higher field strengths are often employed, since they provide an increased image signal-to-noise ratio (SNR). However, as image SNR increases, the relative contribution of physiological noise to the total time series noise will be greater compared to that from thermal noise. ⋯ When the time series were additionally corrected for the residual effects of head motion after retrospective realignment, the tSNR was increased by around 58% in the visual cortex and 71% sub-cortically, exceeding tSNR ~140. In conclusion, optimal physiological noise correction at 7 T increases tSNR significantly, resulting in the highest tSNR per unit time published so far. This tSNR improvement translates into a significant increase in BOLD sensitivity, facilitating the study of even subtle BOLD responses.
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Noise exposure at high intensities leads to a temporary shift of hearing thresholds (TTS) and is followed by a permanent threshold shift (PTS). Permanent threshold shift is not only associated with cochlear damage as the primary site-of-lesion, but also with subsequent structural and functional changes within the central auditory pathway. The aim of the present study was to monitor neuronal activity within central auditory structures in mice after noise exposure at different time intervals using manganese-enhanced magnetic resonance imaging (MEMRI). ⋯ Sustained manganese accumulation was present in the auditory brainstem after moderate acoustic stimulation as well without PTS induction. The long-lasting enhancement of MEMRI signals suggests a noise-induced activity increase of various calcium-dependent processes of different origin (such as neuroprotective mechanisms). The present findings could be helpful to better understand the time-course of different symptoms in NIHL and the individual susceptibility to noise.