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Objective: Previous dichotic listening (DL) studies have shown that interaural amplitude or phase shifts have powerful effects on dichotic ear advantage. However, it is not known how these two factors interact. The present study aims to explore this interaction when amplitude (intensity) and phase (time) shifts occur simultaneously., Design: Participants listened to dichotically presented pairs of consonant-vowel syllables (216 trials) under nine different experimental conditions, systematically varying amplitude (+9 dB) and phase (+35 ms) shifts. Participants reported which syllable they perceived on each trial., Study Sample: Thirty-two healthy adults., Results: The results showed an expected right ear advantage (REA) in the baseline (nosound manipulation) condition. While amplitude shifts favoring the right ear were found to have a greater effect on REA than phase shifts, phase shifts favoring the left ear were found to have a greater effect on left ear advantage (LEA) than amplitude shifts. Furthermore, phase shifts favoring the left ear had a greater effect on LEA than phase shifts favoring the right ear on REA., Conclusions: Present results may have consequences for the training of individuals with auditory and phonetic difficulties, e.g. auditory processing deficits or dyslexia, by aiding the design of optimal combinations of acoustic and phonetic training tools.

The dichotic listening (DL) paradigm is often used to assess brain asymmetries at the behavioral level. The aim of this study was to evaluate the dynamic temporal and topographical characteristics of event related potentials (ERPs) obtained with diotic and dichotic consonant-vowel (CV) stimuli from the same subjects. We used a novel approach in which we concurrently analyzed on a trial-by-trial basis ERP parameters during trials that resulted in a right ear advantage (REA) or left ear advantage (LEA) or that were presented under diotic (homonymous) conditions. CV syllables were used as auditory stimuli (/ba/, /da/, /ga/, /ka/, /pa/, /ta/). The EEG measurements were performed with 64 channels by mainly focusing on the N1P2, N2P3 and late negativity (LN) components. Overall, behavioral data revealed a clear REA. The central area showed higher amplitudes than the other locations for N1P2 responses. Additionally, responses were faster for the diotic, compared to the dichotic conditions. The LN had shorter latencies in trials resulting in a REA, compared with those producing a LEA. This result makes it likely that the overall REA is a time-bound effect, which can be explained by the structural theory of Kimura. Furthermore, the results demonstrated a specific spatiotemporal shift from central to frontal areas between N1P2 and LN that was pronounced in dichotic trials. This shift points towards the involvement of frontal areas in resolving conflicting input.