Understanding environmental sounds in sentence context

Cross-Modal Interaction Between Auditory and Visual Input Impacts Memory Retrieval

How we perceive and learn about our environment is influenced by our prior experiences and existing representations of the world. Top-down cognitive processes, such as attention and expectations, can alter how we process sensory stimuli, both within a modality (e.g., effects of auditory experience on auditory perception), as well as across modalities (e.g., effects of visual feedback on sound localization). Here, we demonstrate that experience with different types of auditory input (spoken words vs. environmental sounds) modulates how humans remember concurrently-presented visual objects. Participants viewed a series of line drawings (e.g., picture of a cat) displayed in one of four quadrants while listening to a word or sound that was congruent (e.g., "cat" or ), incongruent (e.g., "motorcycle" or ), or neutral (e.g., a meaningless pseudoword or a tonal beep) relative to the picture. Following the encoding phase, participants were presented with the original drawings plus new drawings and asked to indicate whether each one was "old" or "new." If a drawing was designated as "old," participants then reported where it had been displayed. We find that words and sounds both elicit more accurate memory for what objects were previously seen, but only congruent environmental sounds enhance memory for where objects were positioned - this, despite the fact that the auditory stimuli were not meaningful spatial cues of the objects' locations on the screen. Given that during real-world listening conditions, environmental sounds, but not words, reliably originate from the location of their referents, listening to sounds may attune the visual dorsal pathway to facilitate attention and memory for objects' locations. We propose that audio-visual associations in the environment and in our previous experience jointly contribute to visual memory, strengthening visual memory through exposure to auditory input.

Cortical mechanisms of talker normalization in fluent sentences

Adjusting to the vocal characteristics of a new talker is important for speech recognition. Previous research has indicated that adjusting to talker differences is an active cognitive process that depends on attention and working memory (WM). These studies have not examined how talker variability affects perception and neural responses in fluent speech. Here we use source analysis from high-density EEG to show that perceiving fluent speech in which the talker changes recruits early involvement of parietal and temporal cortical areas, suggesting functional involvement of WM and attention in talker normalization. We extend these findings to acoustic source change in general by examining understanding environmental sounds in spoken sentence context. Though there may be differences in cortical recruitment to processing demands for non-speech sounds versus a changing talker, the underlying mechanisms are similar, supporting the view that shared cognitive-general mechanisms assist both talker normalization and speech-to-nonspeech transitions.