Widespread functional connectivity and fMRI fluctuations in human visual cortex in the absence of visual stimulation.
To what extent does the visual system's activity fluctuate when no sensory stimulation is present? Here, we studied this issue by examining spontaneous fluctuations in BOLD signal in the human visual system, while subjects were placed in complete darkness. Our results reveal widespread slow fluctuations during such rest periods. In contrast to stimulus-driven activity, during darkness, functionally distinct object areas were fluctuating in unison. These fMRI fluctuations became rapidly spatially de-correlated (39% drop in correlation level, P < 0.008) during visual stimulation. Functional connectivity analysis revealed that the slow spontaneous fluctuations during rest had consistent and specific neuro-anatomical distribution which argued against purely hemodynamic noise sources. Control experiments ruled out eye closure, low luminance and mental imagery as the underlying sources of the spontaneous fluctuations. These results demonstrate that, when no stimulus is present, sensory systems manifest a robust level of slow organized fluctuation patterns.
Nir
Yuval
Y
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Hasson
Uri
U
Levy
Ifat
I
Yeshurun
Yehezkel
Y
Malach
Rafael
R
D000328:Adult; D003623:Dark Adaptation / Q000502:physiology; D004292:Dominance, Cerebral / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005366:Figural Aftereffect / Q000502:physiology; D005403:Fixation, Ocular / Q000502:physiology; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D009903:Optical Illusions / Q000502:physiology; D010775:Photic Stimulation; D012146:Rest / Q000502:physiology; D012683:Sensory Deprivation / Q000502:physiology*; D013223:Statistics as Topic; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*