deletions | additions       diff --git a/Both_CSF_and_imaging_biomarkers__.tex b/Both_CSF_and_imaging_biomarkers__.tex  index 636c6af..3dd27a2 100644  --- a/Both_CSF_and_imaging_biomarkers__.tex  +++ b/Both_CSF_and_imaging_biomarkers__.tex 
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Both CSF and imaging biomarkers targeting A$\beta$ pathophysiology are available and have been widely used in AD research.  Widely used The established  CSF biomarker is the decreased level of amyloid-$\beta_{1-42}$ (A$\beta42$) in AD AD,  while the most used  imaging biomarker is the increased level of Pittsburgh compound in AD patients. A$\beta_{42}$ is 42-amino-acid form of A$\beta$ and is believed to be lowered when it gets converted to A$\beta$ plaques.  This view is consistent to the findings of inverse relationship between CSF A$\beta42$ levels and Pittsburgh compound that binds with A$\beta$ plaques level \cite{Fagan_2006}.  Figure \ref{fig:hypotheticalModelJack_2013} shows the dynamics of these biomarkers where we see that biomarkers targeting $A\beta$ pathophysiology are sensitive well before the cognitive impairment begins.