(a) Multisensory cortical regions (green) that are involved
in multisensory integration. SPL = superior parietal lobule; IPS = intraparietal
sulcus; STS = superior temporal sulcus; vlPFC = ventrolateral prefrontal cortex;
PMC = premotor cortex. (b) Brain areas that are correlated with
endogenous and exogenous attention. SPL = superior parietal lobule; IPS =
intraparietal sulcus; FEF = frontal eye field; TPJ = temporal-parietal junction;
VFC = ventral frontal cortex. Endogenous attention is associated with the dorsal
attention network (blue), while exogenous attention is associated with the
ventral attention network (red) (Fox et al.,
2006). The dorsal attention network is bilateral. It is involved in
voluntary (top-down) orienting and exhibits increases in activity after the
presentation of cues that indicate where, when, or to what subjects should
direct their attention. The ventral attention network is right lateralized. It
is involved in involuntary (stimulus-driven) orienting and exhibits increases in
activity after the presentation of salient targets, particularly when they
appear in unexpected locations (Chica et al.,
2013; Fox et al., 2006).
(c) A framework for the interactions of multisensory
integration with endogenous and exogenous attention. External stimuli from
sensory organs can be integrated at multiple multisensory processing levels
(Giard and Peronnet, 1999; Talsma and Woldorff, 2005). Multisensory
integration is elicited as a consequence of the multiple phases of multisensory
processing. Although these multisensory processes are thought to be automatic,
attention influences not only unimodal processing but also multisensory
processing in both an endogenous and exogenous manner. Endogenous attention can
modulate multisensory processing via endogenous attentional selectivity
[(1) Attentional selectivity]. This modulatory effect
determines the extent to which simultaneously presented stimuli from different
modalities can be integrated (see Figure 2
& Table 1). Furthermore, the
integrated multisensory stimuli can be represented in multisensory templates
that are stored in the brain. These multisensory templates exert top-down
control over contingent attentional capture [(2) Integrated
templates]. Due to their increased salience relative to unimodal
cues, integrated multisensory cues can influence the exogenous orienting of
spatial attention even under quite complex circumstances or can improve visual
search efficiency by increasing target sensitivity [(3) Integrated
cues]. Finally, endogenous attention can spread from one modality to
another in an exogenous manner such that the stimuli of the unattended modality
come to be “attended” [(4) Attentional spread].