The Development of Cortical Multisensory Integration

TLDR

Multisensory development has largely been studied in the superior colliculus, whereas cortical areas such as the anterior ectosylvian sulcus contain distinct visual, auditory, and somatosensory regions with interfacial multisensory neurons. The study examined postnatal maturation of multisensory processes in the cat anterior ectosylvian sulcus, observing that they are rudimentary early and develop gradually. Sensory responsiveness in AES emerges in a sequence—somatosensory at 4 weeks, followed by auditory and multisensory, then visual at 12 weeks—yet early multisensory neurons are immature and only gain integrative capacity with postnatal development, indicating that higher‑order multisensory processing matures late.

Abstract

Although there are many perceptual theories that posit particular maturational profiles in higher-order (i.e., cortical) multisensory regions, our knowledge of multisensory development is primarily derived from studies of a midbrain structure, the superior colliculus. Therefore, the present study examined the maturation of multisensory processes in an area of cat association cortex [i.e., the anterior ectosylvian sulcus (AES)] and found that these processes are rudimentary during early postnatal life and develop only gradually thereafter. The AES comprises separate visual, auditory, and somatosensory regions, along with many multisensory neurons at the intervening borders between them. During early life, sensory responsiveness in AES appears in an orderly sequence. Somatosensory neurons are present at 4 weeks of age and are followed by auditory and multisensory (somatosensory-auditory) neurons. Visual neurons and visually responsive multisensory neurons are first seen at 12 weeks of age. The earliest multisensory neurons are strikingly immature, lacking the ability to synthesize the cross-modal information they receive. With postnatal development, multisensory integrative capacity matures. The delayed maturation of multisensory neurons and multisensory integration in AES suggests that the higher-order processes dependent on these circuits appear comparatively late in ontogeny.