A designated odor-language integration system in the human brain.
Odors are surprisingly difficult to name, but the mechanism underlying this phenomenon is poorly understood. In experiments using event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), we investigated the physiological basis of odor naming with a paradigm where olfactory and visual object cues were followed by target words that either matched or mismatched the cue. We hypothesized that word processing would not only be affected by its semantic congruency with the preceding cue, but would also depend on the cue modality (olfactory or visual). Performance was slower and less precise when linking a word to its corresponding odor than to its picture. The ERP index of semantic incongruity (N400), reflected in the comparison of nonmatching versus matching target words, was more constrained to posterior electrode sites and lasted longer on odor-cue (vs picture-cue) trials. In parallel, fMRI cross-adaptation in the right orbitofrontal cortex (OFC) and the left anterior temporal lobe (ATL) was observed in response to words when preceded by matching olfactory cues, but not by matching visual cues. Time-series plots demonstrated increased fMRI activity in OFC and ATL at the onset of the odor cue itself, followed by response habituation after processing of a matching (vs nonmatching) target word, suggesting that predictive perceptual representations in these regions are already established before delivery and deliberation of the target word. Together, our findings underscore the modality-specific anatomy and physiology of object identification in the human brain.
Department of Neurology and Psychology Department, Stockholm University, SE-10691 Stockholm, Sweden, and Swedish Collegium for Advanced Study, SE-75238 Uppsala, Sweden jonas.olofsson@psychology.su.se.
Jonas K
JK
Olofsson
Department of Neurology and Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611.
Robert S
http://orcid.org/0000-0002-0332-919X
RS
Hurley
Department of Neurology and.
Nicholas E
NE
Bowman
Department of Neurology and.
Xiaojun
http://orcid.org/0000-0002-8310-4141
X
Bao
Department of Neurology and Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611.
M-Marsel
MM
Mesulam
Department of Neurology and Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611.
Jay A
JA
Gottfried
D000328:Adult; D001931:Brain Mapping; D003463:Cues; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D055696:Olfactory Perception; D017397:Prefrontal Cortex / Q000502:physiology*; D013060:Speech; D014796:Visual Perception
evoked potentials; functional MRI; human olfactory system; language; lexical–semantic system; orbitofrontal cortex