Chapter 32 - Cross-Modal Consequences of Human Spatial Attention

Abstract

Traditionally selective attention was studied separately for each sensory modality, but an increasing number of multisensory studies have now examined whether directing attention for a task in one particular sensory modality may have consequences for processing in other modalities also. For cases of spatially directed covert attention, many such cross-modal consequences of attentional selection have now been shown. Attending toward a particular location for a task in one modality often produces spatially corresponding performance consequences for other modalities also, typically with better performance at the location attended for a task in one modality being found in other modalities also. Such cross-modal effects typically remain in register with respect to external space across changes in posture (for example, eye, head, or hand movements) that realign the receptors from different senses. ERP and functional magnetic resonance imaging (fMRI) studies have begun to uncover the neural correlates of such cross-modal spatial attention effects. A key finding is that the direction of spatial attention for a task in one modality (for example, within touch) can modulate sensory-specific processing for another modality (for example, vision), to produce cross-modal influences at stages that would traditionally be considered “unimodal.” For instance, tactile spatial attention can affect occipital cortex activations in response to visual stimuli as measured with fMRI; also P1 and N1 components in visual evoked potentials recorded at the scalp. The cross-modal results that are reviewed in this chapter appear consistent with spatial attention being directed at multimodal levels of representation that may then exert influences on unimodal representations via back-projections.