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A direct anterior cingulate pathway to the primate primary olfactory cortex may control attention to olfaction


Behavioral and functional studies in humans suggest that attention plays a key role in activating the primary olfactory cortex through an unknown circuit mechanism. We report that a novel pathway from the anterior cingulate cortex, an area which has a key role in attention, projects directly to the primary olfactory cortex in rhesus monkeys, innervating mostly the anterior olfactory nucleus. Axons from the anterior cingulate cortex formed synapses mostly with spines of putative excitatory pyramidal neurons and with a small proportion of a neurochemical class of inhibitory neurons that are thought to have disinhibitory effect on excitatory neurons. This novel pathway from the anterior cingulate is poised to exert a powerful excitatory effect on the anterior olfactory nucleus, which is a critical hub for odorant processing via extensive bilateral connections with primary olfactory cortices and the olfactory bulb. Acting on the anterior olfactory nucleus, the anterior cingulate may activate the entire primary olfactory cortex to mediate the process of rapid attention to olfactory stimuli.

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We thank Isabel Park and Justin Tepes for technical assistance; Marcia Feinberg and Clare Timbie for outstanding electron microscopy assistance; Dr. Ron Killiany for assistance with imaging; Dr. Angela Carville and Dr. Leah Makaron for veterinary care and surgical assistance; Dr. Basilis Zikopoulos, Dr. Jamie Bunce, Dr. Yohan John and Dr. Maria Medalla for helpful discussion of the manuscript. This work was supported by National Institutes of Health grants from the National Institute of Neurological Disorders and Stroke (R01NS024760) and the National Institute of Mental Health (RO1MH057414); and by Center of Excellence for Learning in Education, Science and Technology (CELEST), a National Science Foundation Science of Learning Center (NSF SBE-0354378). M. Á. García-Cabezas was the recipient in 2010 of a Short Stay Grant from Fundación Alicia Koplowitz (Spain).

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García-Cabezas, M.Á., Barbas, H. A direct anterior cingulate pathway to the primate primary olfactory cortex may control attention to olfaction. Brain Struct Funct 219, 1735–1754 (2014).

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  • Olfaction
  • Attention
  • Anterior cingulate cortex
  • Primary olfactory cortex
  • Anterior olfactory nucleus
  • Posterior orbitofrontal cortex