Marshall and Newcombe (1973) describe two processes or pathways in the brain for reading: a phonological, which derives meaning by recognising the sound; and a semantic, which recognises the pattern of the word. Since a full stop/period is never spoken -unless dictating a telegram (anyone here done that recently?), and is only a marker representing the ending or beginning of a language 'event'. I doubt if the brain stops to consider this any longer than any other word that has been recognised from the brain's store of words. Having said that, one could measure gaps when reading aloud as this would presumably be a performance and require pauses as markers for the audience, but this would seem to be a question on the craft of acting, rather than a linguistic one.