Auditory processing under cross-modal visual load investigated with simultaneous EEG-fMRI.

Cognitive task demands in one sensory modality (T1) can have beneficial effects on a secondary task (T2) in a different modality, due to reduced top-down control needed to inhibit the secondary task, as well as crossmodal spread of attention. This contrasts findings of cognitive load compromising a secondary modality's processing. We manipulated cognitive load within one modality (visual) and studied the consequences of cognitive demands on secondary (auditory) processing. 15 healthy participants underwent a simultaneous EEG-fMRI experiment. Data from 8 participants were obtained outside the scanner for validation purposes. The primary task (T1) was to respond to a visual working memory (WM) task with four conditions, while the secondary task (T2) consisted of an auditory oddball stream, which participants were asked to ignore. The fMRI results revealed fronto-parietal WM network activations in response to T1 task manipulation. This was accompanied by significantly higher reaction times and lower hit rates with increasing task difficulty which confirmed successful manipulation of WM load. Amplitudes of auditory evoked potentials, representing fundamental auditory processing showed a continuous augmentation which demonstrated a systematic relation to cross-modal cognitive load. With increasing WM load, primary auditory cortices were increasingly deactivated while psychophysiological interaction results suggested the emergence of auditory cortices connectivity with visual WM regions. These results suggest differential effects of crossmodal attention on fundamental auditory processing. We suggest a continuous allocation of resources to brain regions processing primary tasks when challenging the central executive under high cognitive load.

The differential contribution of facial expressions, prosody, and speech content to empathy.

BACKGROUND: Facial expressions, prosody, and speech content constitute channels by which information is exchanged. Little is known about the simultaneous and differential contribution of these channels to empathy when they provide emotionality or neutrality. Especially neutralised speech content has gained little attention with regards to influencing the perception of other emotional cues. METHODS: Participants were presented with video clips of actors telling short-stories. One condition conveyed emotionality in all channels while the other conditions either provided neutral speech content, facial expression, or prosody, respectively. Participants judged the emotion and intensity presented, as well as their own emotional state and intensity. Skin conductance served as a physiological measure of emotional reactivity. RESULTS: Neutralising channels significantly reduced empathic responses. Electrodermal recordings confirmed these findings. The differential effect of the communication channels on empathy prerequisites was that target emotion recognition of the other decreased mostly when the face was neutral, whereas decreased emotional responses attributed to the target emotion were especially present in neutral speech. CONCLUSION: Multichannel integration supports conscious and autonomous measures of empathy and emotional reactivity. Emotional facial expressions influence emotion recognition, whereas speech content is important for responding with an adequate own emotional state, possibly reflecting contextual emotion-appraisal.