title: Serial processing in primary and secondary somatosensory cortex: A DCM analysis of human fMRI data in response to innocuous and noxious electrical stimulation.
abstract: The anatomy of the somatosensory system allows both serial and parallel information flow but the conditions involving each mode of processing is a matter of debate. In this functional magnetic resonance imaging (fMRI) study, cutaneous electrical stimulation was applied to human volunteers at three intensities (low-innocuous, moderate-noxious and high-noxious) to investigate interactions between contralateral primary and secondary somatosensory cortices (S1c and S2c), and between contralateral and ipsilateral S2 (S2c and S2i), using dynamic causal modeling (DCM). Our results are consistent with serial processing with a key role of the direct input to S1c for all three intensity levels. The more intense stimulus also induced significantly more interactions between S2i and S2c, consistent with an increase in inter-hemispheric integration associated with the additional recruitment of nociceptive inputs. However, stronger pain reports were also associated with reduced information flow from S1c to S2c at both the moderate (r=-0.81, p=0.004) and the high stimulation level (r=-0.63, p=0.037). These findings suggest that the connectivity pattern driven by innocuous inputs is modified by the additional activation of nociceptive afferents.
authors.affiliation: Department of neuroscience Université de Montréal, Montreal, QC, Canada; Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Montréal, QC, Canada; Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM) Université de Montréal, Montréal, QC, Canada.
authors.forename: Mina
authors.initials: M
authors.lastname: Khoshnejad
authors.affiliation: Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM) Université de Montréal, Montréal, QC, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Université de Montréal, Montréal, QC, Canada; Department of Chiropractic, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Piché
authors.affiliation: Department of Biomedical Engineering, Lebanese International University, Beirut, Lebanon.
authors.forename: Soha
authors.initials: S
authors.lastname: Saleh
authors.affiliation: Department of Stomatology, Université de Montréal, Montréal, QC, Canada; Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Montréal, QC, Canada.
authors.forename: Gary
authors.initials: G
authors.lastname: Duncan
authors.affiliation: Department of Stomatology, Université de Montréal, Montréal, QC, Canada; Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Montréal, QC, Canada; Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM) Université de Montréal, Montréal, QC, Canada. Electronic address: pierre.rainville@umontreal.ca.
authors.forename: Pierre
authors.initials: P
authors.lastname: Rainville
mesh_terms: D000328:Adult; D001499:Bayes Theorem; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010147:Pain Measurement; D058748:Pain Perception / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: DCM; Electrical stimulations; Intensity encoding; Serial processing; Somatosensory cortex