Regional Brain Activity Of Early Blind During Rest

Purpose Early blindness as a unimodal sensory deprivation model has been extensively studied by task-based functional magnetic resonance imaging. Recently two resting-state fMRI studies have reported altered functional connectivity between visual and other brain areas in early blind, however, they cannot answer which brain areas'local activities are changed. Amplitude of low-frequence fluctuation(ALFF) and Regional homogeneity (ReHo) are all proposed by Zang et al, which can reflect spontaneous neural activity, have become main indexes to study local brain activity in resting-state. So far, they have been used to investigate physical state and a variety of brain diseases, which are partly consistent with the pathophysiological changes in these disorders. There is no study on regional brain activity changes of early blind in resting-state. In our study, we use ALFF and ReHo to analyze changes of local brain activity in resting-state.Materals and Methods All together sixteen early blind and thirty-two age- and gender-matched sighted subjects enrolled in our study. Resting-state fMRI scan and sagittal structural images were all collected using a 3.0-T scanner. All preprocessing steps were carried out using the statistical parametric mapping (SPM8, http://www.fil.ion.ucl.ac.uk/spm), including time slicing, reducing head movement, normalized to the MNI, resampling to to 3×3×3 mm cubic voxels, a band-pass frequency filter (0.01-0.08Hz, to reduce low-frequency drift and high-frequency noise), smoothed with a 6 mm full width at half maximum. The unnormalized and normalized ALFF and ReHo values were calculated using specific algorithms, brain areas with significant changes in ALFF or ReHo values between groups were acquired by a two-sample t test. To study the relationship of between ALFF and the underlying blood oxygen level-dependent (BOLD) signals, we measured the activity amplitude (AM) of the whole brain and five regions of interest (ROI) with significantly increased ALFF values in the early blind under a normalized method. After we got the ReHo value of every voxel, an individual ReHo map was obtained on a voxel by voxel basis using REST software. To reduce the effect of individual variance, we normalized the Reho value of each voxel by dividing the mean Reho of the whole brain for each subject. Brain areas with significant changes in ReHo values between the two groups were acquired by voxel-based analysis. Multiple comparisons were statistically corrected by false discovery rate (FDR) with thresholds of q<0.05 and cluster size>30 voxels. Results Sixteen blind subjects were recruited in the final statistics. Compared to sighted subjects, the early blind showed significantly increased ALFF (unnormalized) in visual areas including the bilateral middle and inferior occipital gyri, lingual and fusiform gyri, calcarine cortices and inferior temporal gyri; the significantly increased ALFF was present in the similar brain areas in normalized analysis as in the unnormalized analysis; the early blind showed increased ReHo in visual areas including the bilateral inferior occipital gyri, lingual and fusiform gyri, calcarine cortices, and inferior temporal gyri, left middle occipital gyri. However, we did not find significantly decreased ALFF and ReHo in any brain area in the early blind comparing to that in the sighted controls. These findings are consistent with prior positron emission tomography studies which showed increased resting-state cerebral blood flow and glucose metabolism in the visual areas of early blind and thicker visual cortex.Concusion Firstly, we found increased ALFF in visual areas in early blind corresponding to the increased mean and standard deviation of regional BOLD signals, which provides direct evidence to the hypothesis that ALFF reflects the level of the resting-state brain activity. Secondly, we suggest that high resting-state brain activity in the visual areas of the early blind could be partially ascribed to the increased corticocortical, thalamocortical and intracortical connections due to lack of visual experience during critical cortex developmental period.