Positive and Negative Somatotopic BOLD Responses in Contralateral Versus Ipsilateral Penfield Homunculus.
One of the basic properties of sensory cortices is their topographical organization. Most imaging studies explored this organization using the positive blood oxygenation level-dependent (BOLD) signal. Here, we studied the topographical organization of both positive and negative BOLD in contralateral and ipsilateral primary somatosensory cortex (S1). Using phase-locking mapping methods, we verified the topographical organization of contralateral S1, and further showed that different body segments elicit pronounced negative BOLD responses in both hemispheres. In the contralateral hemisphere, we found a sharpening mechanism in which stimulation of a given body segment triggered a gradient of activation with a significant deactivation in more remote areas. In the ipsilateral cortex, deactivation was not only located in the homolog area of the stimulated parts but rather was widespread across many parts of S1. Additionally, analysis of resting-state functional magnetic resonance imaging signal showed a gradient of connectivity to the neighboring contralateral body parts as well as to the ipsilateral homologous area for each body part. Taken together, our results indicate a complex pattern of baseline and activity-dependent responses in the contralateral and ipsilateral sides. Both primary sensory areas were characterized by unique negative BOLD responses, suggesting that they are an important component in topographic organization of sensory cortices.
Department of Medical Neurobiology, Institute of Medical Research Israel - Canada (IMRIC), Faculty of Medicine.
Zohar
Z
Tal
Department of Medical Neurobiology, Institute of Medical Research Israel - Canada (IMRIC), Faculty of Medicine.
Ran
R
Geva
Department of Medical Neurobiology, Institute of Medical Research Israel - Canada (IMRIC), Faculty of Medicine.|The Edmond and Lily Safra Center for Brain Science (ELSC).|Program of Cognitive Science, The Hebrew University of Jerusalem, Jerusalem 91220, Israel.
Amir
A
Amedi
D000328:Adult; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010812:Physical Stimulation; D012146:Rest; D013003:Somatosensory Cortex / Q000000981:diagnostic imaging* / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult
D010100:Oxygen
fMRI; functional connectivity; somatosensory; topography