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Abstract:
The claustrum is an evolutionarily conserved structure, which in mammals, is well connected
to most of the neocortex in a topographical manner. The claustrum has thus been deemed an
important site for combining sensory information from different modalities, and its widespread
projections put this structure in an ideal place to modulate processing in different cortical regions.
Yet, our understanding of the properties and function of this structure is rather limited.
Using extracellular recordings we map the sensory specific responses and quantify the integration
properties of the claustrum of awake monkeys. Using paradigms employing visual,
auditory and somatosensory stimuli, we find interactions between the audio-visual and the
audio-somatosensory modalities, with the recorded responses exhibiting transient activity specific
to the onset of the stimulus. At many sites, the responses to combined stimuli differ from
the unisensory responses. Furthermore, comparing sensory responses recorded in the claustrum
to those recorded at adjacent multisensory sites in insular cortex and putamen, we find
that neurons in the claustrum often respond with much higher firing rates. In addition, we study
the anatomical connectivity of the claustrum in the rat. Afferent and efferent projections subdivide
this structure into sensory specific regions. Although particular modality specific zones
have been shown to overlap, others remain aloof. This challenges the hypothesis that this
structure facilitates multi-sensory integration across all modalities. Using anterograde and retrograde
tracers we identify intra-claustral projections that connect the different sensory zones.
Our results not only confirm previous reports of arealization, but also suggest new routes of
multisensory interactions involving this structure. Altogether, our findings well support a role
for the claustrum in facilitating the interaction of the different senses.
