Predictions about forthcoming auditory events can be established on the basis of preceding visual information. Sounds being incongruent to predictive visual information have been found to elicit an enhanced negative ERP in the latency range of the auditory N1 compared with physically identical sounds being preceded by congruent visual information. This so-called incongruency response (IR) is interpreted as reduced prediction error for predicted sounds at a sensory level. The main purpose of this study was to examine the impact of probability manipulations on the IR. We manipulated the probability with which particular congruent visual–auditory pairs were presented (83/17 vs. 50/50 condition). This manipulation led to two conditions with different strengths of the association of visual with auditory information. A visual cue was presented either above or below a fixation cross and was followed by either a high- or low-pitched sound. In 90% of trials, the visual cue correctly predicted the subsequent sound. In one condition, one of the sounds was presented more frequently (83% of trials), whereas in the other condition both sounds were presented with equal probability (50% of trials). Therefore, in the 83/17 condition, one congruent combination of visual cue and corresponding sound was presented more frequently than the other combinations presumably leading to a stronger visual–auditory association. A significant IR for unpredicted compared with predicted but otherwise identical sounds was observed only in the 83/17 condition, but not in the 50/50 condition, where both congruent visual cue–sound combinations were presented with equal probability. We also tested whether the processing of the prediction violation is dependent on the task relevance of the visual information. Therefore, we contrasted a visual–auditory matching task with a pitch discrimination task. It turned out that the task only had an impact on the behavioral performance but not on the prediction error signals. Results suggest that the generation of visual-to-auditory sensory predictions is facilitated by a strong association between the visual cue and the predicted sound (83/17 condition) but is not influenced by the task relevance of the visual information.

Visual information may influence the processing of auditory information, as illustrated by phenomena like the ventriloquist illusion (e.g., Alais & Burr, 2004), the McGurk effect (McGurk & MacDonald, 1976), or cross-modal spatial attention effects (e.g., Eimer & Driver, 2001). One way in which visual information can influence the processing of auditory information

What happens if a visual cue misleads auditory expectations? Previous studies revealed an early visuo–auditory incongruency effect, so-called incongruency response (IR) of the auditory event-related brain potential (ERP), occurring 100 ms after onset of the sound being incongruent to the preceding visual cue. So far, this effect has been ascribed to reflect the mismatch between auditory sensory expectation activated by visual predictive information and the actual sensory input. Thus, an IR should be confined to an asynchronous presentation of visual cue and sound. Alternatively, one could argue that frequently presented congruent visual-cue–sound combinations are integrated into a bimodal representation whereby violation of the visual–auditory relationship results in a bimodal feature mismatch (the IR should be obtained with asynchronous and with synchronous presentation). In an asynchronous condition, an either high-pitched or low-pitched sound was preceded by a visual note symbol presented above or below a fixation cross (90% congruent; 10% incongruent), while in a synchronous condition, both were presented simultaneously. High-pitched and low-pitched sounds were presented with different probabilities (83% vs. 17%) to form a strong association between bimodal stimuli. In both conditions, tones with pitch incongruent with the location of the note symbols elicited incongruency effects in the N2 and P3 ERPs; however, the IR was only elicited in the asynchronous condition. This finding supports the sensorial prediction error hypothesis stating that the amplitude of the auditory ERP 100 ms after sound onset is enhanced in response to unexpected compared with expected but otherwise identical sounds.