NeuroImage
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Spatial attention amplifies the neural response, i.e. spike rates, brain metabolism, and oscillatory activity at gamma frequency (beyond 30 Hz). In this study we show that when a visual target is attended enhanced synchrony between gamma phase (30 to 50 Hz) and theta phase (4 to 7 Hz), representing bottom-up and top-down activity, respectively, can be observed. ⋯ This seems to be true in particular for theta oscillations showing increased interregional phase-coupling. We conclude that memory information is stored within a distributed theta network and it is matched with an incoming sensory trace at posterior brain areas.
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Spinal cord fMRI is a useful tool for studying spinal mechanisms of pain, hence for analgesic drug development. Its technical feasibility in both humans and rats has been demonstrated. This study investigates the reproducibility, robustness, and spatial accuracy of fMRI of lumbar spinal cord activation due to transcutaneous noxious and non-noxious electrical stimulation of the hindpaw in alpha-chloralose-anesthetized rats. ⋯ Spatially, the fMRI signal extended approximately 5 mm in the longitudinal direction, covering L(3)-L(5) segments. In the cross-sectional direction, the highest signal change of blood volume-weighted fMRI was in the middle of the ipsilateral dorsal horn, which roughly corresponds to laminae V and VI, while the highest signal change of BOLD fMRI was in the ipsilateral dorsal surface. This study demonstrates that spinal cord fMRI can be performed in anesthetized rats reliably and reproducibly offering it as a potential tool for analgesic drug discovery.