Viski S, Orgovan D, Szabo K, Rosengarten B, Csiba L, Olah L. J Neurol Sci. 2016 Apr 15;363:132-9. doi: 10.1016/j.jns.2016.02.050
Viski et al. reported on the effect of reading on blood flow changes in the posterior cerebral artery in early blind and sighted people using TCD.
From a methodological point of view, the authors used two different experimental protocols in both groups in order to evaluate heamodynamic changes in PCA: PCA flow velocity during reading was compared to the resting phase and “NLC” phase (volunteers “read” non-lexical characters; e.g. .,-.:,-.:...,). With the use of these experimental protocols, the authors were able to investigate separately the effect of “light stimulus + print reading” versus “print reading alone” in sighted, and “hand/finger movement + Braille reading” versus “Braille reading alone” in blind subjects.
This study documented no significant changes in the flow response of the PCA evoked by “Braille reading alone” in blind (10.5 ± 4.5%) and “print reading alone” in sighted subjects (8.1 ± 3.5%). In addition, the flow increase induced by “hand/finger movement + Braille reading” and by “Braille reading alone” did not differ in blind people, however, “light stimulus + print reading” in sighted subjects caused higher PCA flow increase (25.9 ± 6.9%) than “print reading alone” (8.1 ± 3.5%).
The main take-home message of this study is that no significant PCA flow response changes were detected among blind and sighted subjects, using Braille and print reading alone stimulating techniques. Interestingly, in sighted people, the 3-times higher flow velocity increase induced by “light stimulus + print reading” compared with “print reading alone” indicated that 2/3 of PCA flow increase during reading was due to the light stimulus and only 1/3 of flow response was caused by reading alone.