10. How does fMRI form an image of neural activity? How to form an image of neural activity using NMR? Need to measure: 1. Spatial Location 2. Neural Activity Magnitude
14. Spatial Location in 2-D Echo Planar Imaging (Mansfield 1977): use frequency encoding to determine the “ x” direction and echo encoding to determine the “ y ” direction. sampling windows
22. Issues! There is not a one-to-one correspondence between T2 and the neural activity that we are trying to measure. There are pathways that might decrease the decay rate and hence results in a decreased MR signal!
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25. This figure relates the temporal and spatial resolution of methods for the study of brain function to the size scale of neuronal features and to the “invasiveness” of the methods. Comparison: temporal and spatial resolution; and invasiveness
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Notas del editor
NMR- see p1 Noll; hydrogen - p 1 Noll susceptibility - p2 Cohen
1 - p1 Noll 2 - p2 Cohen 3 - p2 Cohen and p1 Noll
2 - p2 Cohen
1 - p2 Noll, Hornak table - Hornak
p2 Noll in phase - p3 Cohen
p 4 Cohen p3-4 Noll
p5 Noll p5 Cohen
p6 Noll
p7 Noll, p5-6 Cohen
p9 Noll, p12 Cohen rapid data acquisition techniques special reception coils, increasing static magnetic field intensity SNR depends on temporal resolution - lower temporal resolution head - head restraints, bite bars, post-processing techniques, different gradient systems, multi-shot techniques, movement correction algorithms, use cortical landmarks
p13 Cohen: mapping cortical and subcortical function will require methods with an appropriate balance of temporal and spatial resolution.
invasiveness ==> it is possible to perform longitudinal studies
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