Heteromodal connections supporting multisensory integration at low levels of cortical processing in the monkey

• Published in: The European journal of neuroscience Vol. 22; no. 11; pp. 2886 - 2902
• Main Authors: Cappe, Céline, Barone, Pascal
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.12.2005; Wiley
• Subjects: Animals; Auditory Cortex; Auditory Cortex - physiology; Callithrix; Cerebral Cortex; Cerebral Cortex - cytology; Cerebral Cortex - physiology; Cognition; Cognition - physiology; connectivity; Data Interpretation, Statistical; Feedback; Feedback - physiology; feedback-feedforward; Histocytochemistry; Image Processing, Computer-Assisted; Life Sciences; Nerve Net; Nerve Net - cytology; Nerve Net - physiology; Neurons and Cognition; New World monkey; polysensory; Primates; retrograde tracers; Somatosensory Cortex; Somatosensory Cortex - physiology; Visual Cortex; Visual Cortex - physiology
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2005.04462.x

While multisensory integration is thought to occur in higher hierarchical cortical areas, recent studies in man and monkey have revealed plurisensory modulations of activity in areas previously thought to be unimodal. To determine the cortical network involved in multisensory interactions, we performed multiple injections of different retrograde tracers in unimodal auditory (core), somatosensory (1/3b) and visual (V2 and MT) cortical areas of the marmoset. We found three types of heteromodal connections linking unimodal sensory areas. Visuo‐somatosensory projections were observed originating from visual areas [probably the ventral and dorsal fundus of the superior temporal area (FSTv and FSTd), and middle temporal crescent (MTc)] toward areas 1/3b. Somatosensory projections to the auditory cortex were present from S2 and the anterior bank of the lateral sulcus. Finally, a visuo‐auditory projection arises from an area anterior to the superior temporal sulcus (STS) toward the auditory core. Injections in different sensory regions allow us to define the frontal convexity and the temporal opercular caudal cortex as putative polysensory areas. A quantitative analysis of the laminar distribution of projecting neurons showed that heteromodal connections could be either feedback or feedforward. Taken together, our results provide the anatomical pathway for multisensory integration at low levels of information processing in the primate and argue against a strict hierarchical model.