Brain activities during listening to ambiguous melodies revealed in fMRI / Follow-up report.

Abstract

The proposed ambiguity in music exists between the illusory melody C5-A4-C5-A4 (Down) and C5-E5-C5-E5 (Up) that may be heard when listening to intermittently repeated tone C5 inserted between two sustained tones A4 and E5. In this study, we changed the methods to obtain clearer images of brain activities than shown in previous report; (1) scanning and stimulus presentation used to be alternately given to prevent scanning noise from interfering with the stimulus but now given simultaneously (2) each of three (Down, Up and Neutral) categories of stimuli is presented 10 times in a series instead of given in random order as in the previous study (3) visual presentation of the implicit melodies is given instead of auditory presentation of a preceding phrase. The prefrontal cortex including the orbitofrontal cortex showed increased activities for the contrasts Down vs Neutral and Up vs Neutral, implying the involvement of working memory and motivation.