If you shine a light on a 3D layer, you can affect how the light interacts with the layer by adjusting its Material Options.
Twirl open the layer that is being hit by the light (not the light layer), and then twirl open the Material Options category. The key properties to adjust are Ambient, Diffuse, Specular, Shininess, and Metal.
To get a sense of how they work, drill them all down to zero, and then experiment by scrubbing each one up, one by one.
Start with Spectacular, which will add a hotspot to your layer. When you first raise this value, it may turn your whole layer into one big hotspot.)
Then raise Shininess, which makes your hotspot smaller and dims out the rest of the layer.
Next, raise the Diffuse property, which will fill in the darker areas (the areas not in the hotspot).
Raising metal will lower the color distinction between the darker areas and the highlight, but the highlight will still be brighter.
Raising the Ambient property makes the layer look slightly more reflective, but the difference is pretty subtle compared with the other Material Option properties