digraph g {
    //node [shape=plaintext];
    node [fontname="sans-serif"];
    edge [arrowhead="o" fontsize=11.0 fontname="sans-serif"]

    ctx [label="cerebral cortex"]
    p [label="putamen"]
    gpi [label="GP interna"]
    gpe [label="GP externa"]
    thal [label="VA/VL thalamus"]
    snc [label="substantia nigra pars compacta"]
    stn [label="subthalmic nucleus"]

    // direct pathway and common
    ctx -> p [label="(+) glutamate"]
    p -> gpi [label="(-) GABA" arrowhead="dot"]
    gpi -> thal [label="(-) GABA" arrowhead="dot"]
    thal -> ctx [label="(+) glutamate"]
    snc -> p [label="(+) dopamine"]
    
    // indirect pathway
    p -> gpe [label="(-) GABA" arrowhead="dot"]
    gpe -> stn [label="(-) GABA" arrowhead="dot"]
    stn -> gpi [label="(+) glutamate"]
    //stn -> gpi [label="disease:
    //hemiballismus" style="dotted" color="red"]  //hemiballismus disease
    snc -> p [label="(-) dopamine" arrowhead="dot"]
}