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0.8. 0.4. 0.0. -0.4. d [...-Hb]/µM. 0.2. 0.0. R. -0.2. -0.4. imager. 0. 15. 30. 45. 60. time / s. d [...-Hb]/µM. left right. Studying NIRS from infancy. uses and abuses of optical topography hellmuth obrig. use s and abuses of optical topography hellmuth obrig !!!!!.

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  1. 0.8 0.4 0.0 -0.4 d[...-Hb]/µM 0.2 0.0 R -0.2 -0.4 imager 0 15 30 45 60 time / s d[...-Hb]/µM left right Studying NIRS from infancy

  2. uses and abuses of optical topography hellmuth obrig

  3. uses and abuses of optical topography hellmuth obrig!!!!!

  4. Maybe there is some abuse in the literature

  5. Taga et al 2003

  6. this is a boring experiment 20s 20s condition 1 condition2 n=52 760 nm & 850 nm 7 detectors 8 sources

  7. the imaging result is redundant imager

  8. the interesting result is the time course concentration change / µM stim vs. stim stim vs. rest time /s

  9. data processing artefact removal General Linear Model approach PCA removal of global effects event related averaging

  10. Thus we can check our hypothesis by an analysis procedure

  11. Let‘s make things complicated Iadecola et al 04

  12. ... or alternatively oversimplify the matter neuronalmodel blood-flow regulator oxygen- extractor venous balloon BOLD contrast

  13. ‚activation‘ is an operational term E E 0.01µM 3 s D D [deoxy-Hb] BOLD contrast

  14. likewise ‚deactivation‘ is an operational term

  15. the time course is still conroversial

  16. the recoupling issue NIRS VEP

  17. There is a component not showing habituation

  18. want a break? flow velocity oxygenation d OD neuronal activity vascular response stimulus parameters vascular-response

  19. An early component of the VEP does not show habituation

  20. transcallosal inhibition

  21. Comparing excitation and inhibition of primary motor cortex tapping TMS NIRS NIRS

  22. the vascular response is similar motor TMS 10 0 -10 1 0 -1

  23. The time courses are qualitatively similar oxy deoxy mmol / l mmol / l time / s time / s

  24. activation and inhibition cannot be discriminated x3 x3 motor without with preactivation

  25. Inverse problem of the vascular response Effect CBF Spiking (on target) (local) (output) Exitation Exitation+ Inhibition Deactivation Inhibition ? Inhibition ? Disinhibition ? Lauritzen & Gold PNAS 2003

  26. Does background activity have an influence on the vascular response? ISS NIRS EEG ssVEP source detector

  27. There is a focal hyperoxygenation over the occipital region detector oxy-Hb emitter deoxy-Hb

  28. experimental setup 5ms 5ms 45ms 45ms ... ... 5 9 12 20 8 6 1 0 23 ... ... NIRS-probe EEG P3 O1 Pz O2 P4 15 s electrode 5 cm 2.5 cm NIRS 2.5 cm electrode 10 cm emitter detector

  29. Neurovascular coupling? a 2*a a 2*a

  30. Alpha power is an inverse predictor of the haemodynamic response 8-12Hz24-28Hz

  31. Modulation of evoked and spontaneous activity is mutually dependent 1s ‚idling state‘ Summation (EP /LFP) stimulus desynchronisation

  32. Use or abuse? There is a NIRS response closely linked to classical imaging methods There is changes which definitely are not related to the brain There is options to identify brain related signals Neurovascular coupling is a very general principle There are exceptions from the rule NIRS allows to investigate these deviations from a 1:1 translation

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