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Manganese-enhanced MRI visualizes V1 in the non-human primate visual cortex
Nicholas A Bock1, Ara Kocharyan, Afonso C Silva
1Cerebral Microcirculation Unit, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065, USA. bockn@mail.nih.gov
Abstract:
MRI at 7 Tesla has been used to investigate the accumulation of manganese in the occipital cortex of common marmoset monkeys (Callithrix jacchus) after administering four fractionated injections of 30 mg/kg MnCl(2) . 4H(2)O in the tail vein. We found a statistically significant decrease in T(1) in the primary (V1) and secondary (V2) areas of the visual cortex caused by an accumulation of manganese. The larger T(1) shortening in V1 (DeltaT(1) = 640 ms) relative to V2 (DeltaT(1) = 490 ms) allowed us to robustly detect the V1/V2 border in vivo using heavily T(1)-weighted MRI. Furthermore, the dorso-medial (DM) and middle-temporal (MT) areas of the visual pathway could be identified by their T(1)-weighted enhancement. We showed by comparison to histological sections stained for cytochrome oxidase (CO) activity that the extent of V1 is accurately identified throughout the visual cortex by manganese-enhanced MRI (MEMRI). This provides a means of visualizing functional cortical regions in vivo and could be used in longitudinal studies of phenomena such as cortical plasticity, and for non-destructive localization of cortical regions to guide in the implementation of functional techniques.
Insights
Manganese accumulation in marmoset monkey brains was visualized using 7 Tesla MRI. Manganese-enhanced MRI (MEMRI) successfully mapped visual cortex regions, aiding functional studies.
Area of Science:
- Neuroimaging
- Primate Neuroscience
- Magnetic Resonance Imaging
Background:
- Investigating manganese (Mn) accumulation in the brain is crucial for understanding its neurotoxic effects and potential as a contrast agent.
- High-field MRI, specifically 7 Tesla (7T), offers enhanced sensitivity for detecting subtle changes in brain tissue.
Purpose of the Study:
- To investigate manganese accumulation in the common marmoset monkey (Callithrix jacchus) visual cortex using 7T MRI.
- To evaluate the utility of manganese-enhanced MRI (MEMRI) for visualizing functional cortical areas in vivo.
Main Methods:
- Common marmoset monkeys received fractionated intravenous injections of manganese chloride (MnCl2).
- High-resolution 7T MRI was employed to assess T1-weighted signal changes.
- Manganese distribution was compared with histological staining for cytochrome oxidase (CO) activity.
Main Results:
- A statistically significant T1 shortening was observed in the primary (V1) and secondary (V2) visual cortex, indicating manganese accumulation.
- Differential T1 shortening between V1 and V2 allowed for robust in vivo delineation of the V1/V2 border.
- MEMRI accurately identified the extent of V1, correlating well with CO staining, and visualized other visual pathway areas like DM and MT.
Conclusions:
- MEMRI is an effective technique for visualizing functional cortical regions in vivo in marmoset monkeys.
- This method enables non-destructive localization of cortical areas, supporting longitudinal studies of cortical plasticity and guiding functional neuroimaging techniques.
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