FIGURE 1.

General properties of thalamic afferents. (A) Schematic representation of the features that distinguish drivers and modulators in first order (left) and higher order (right) nuclei. Note the higher fraction of modulators in higher order nuclei, where some modulators have large synapses contacting proximal dendrites. In both first and higher order nuclei, modulators activate ionotropic and metabotropic receptors and, in those in which it has been tested, the postsynaptic responses facilitate under repetitive stimulation. (B) Approximate location of the brain regions that provide modulator afferents to the thalamus, color-coded for the neurotransmitter they use. The outline of a rodent brain is used for convenience, although the diagram combines results from different species (see text for details).