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Magnetic resonance imaging of neuronal connections in the macaque monkey
Kadharbatcha S Saleem1, Jon M Pauls, Mark Augath
1Riken Brain Science Institute, 2-1 Hirosawa, Wakoshi, Saitama 351-0198, Japan. saleemk@pcg.wustl.edu
Abstract:
Recently, an MRI-detectable, neuronal tract-tracing method in living animals was introduced that exploits the anterograde transport of manganese (Mn2+). We present the results of experiments simultaneously tracing manganese chloride and wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) to evaluate the specificity of the former by tracing the neuronal connections of the basal ganglia of the monkey. Mn2+ and WGA-HRP yielded remarkably similar and highly specific projection patterns. By showing the sequential transport of Mn2+ from striatum to pallidum-substantia nigra and then to thalamus, we demonstrated MRI visualization of transport across at least one synapse in the CNS of the primate. Transsynaptic tract tracing in living primates will allow chronic studies of development and plasticity and provide valuable anatomical information for fMRI and electrophysiological experiments in primates.
Insights
Magnetic resonance imaging (MRI) tract tracing using manganese (Mn2+) effectively maps neuronal connections in primates. This method visualizes neural pathways across synapses, aiding in developmental and plasticity studies.
Area of Science:
- Neuroscience
- Neuroimaging
- Primate research
Background:
- Neuronal tract tracing is crucial for understanding brain connectivity.
- Existing methods have limitations in living subjects.
- Manganese (Mn2+) offers a novel MRI-detectable approach for anterograde neuronal tracing.
Purpose of the Study:
- To evaluate the specificity of manganese chloride (Mn2+) as a neuronal tracer.
- To compare Mn2+ tracing with a conventional tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP).
- To demonstrate transsynaptic tracing in the primate central nervous system (CNS) using MRI.
Main Methods:
- Simultaneous tracing of Mn2+ and WGA-HRP in the basal ganglia of a monkey.
- Utilizing MRI to detect Mn2+ transport.
- Analyzing projection patterns to assess tracer specificity and pathway visualization.
Main Results:
- Mn2+ and WGA-HRP exhibited highly similar and specific projection patterns.
- Demonstrated sequential Mn2+ transport from striatum to pallidum-substantia nigra, then to thalamus.
- Successfully visualized Mn2+ transport across at least one synapse in the primate CNS via MRI.
Conclusions:
- Mn2+ tract tracing is a specific and effective method for mapping neuronal connections in primates.
- MRI visualization of transsynaptic Mn2+ transport enables chronic studies of neural development and plasticity.
- This technique provides valuable anatomical data for functional MRI and electrophysiological studies in primates.