The lemniscal and paralemniscal pathways of the trigeminal system in rodents are integrated at the level of the somatosensory cortex.

The studies reported here demonstrate that the projection representation of the whiskers in the somatosensory cortex in rats is the area at which afferent streams arriving via the lemniscal and paralemniscal projections interact. The responses of neurons in layers IV, Va, and Vb to mechanical stimulation of single whiskers were studied. Neurons in layers IV and Vb were found to show more frequent phasic responses (typical of the lemniscal system), while those in layer Va produced predominantly tonic responses (typical of the paralemniscal system). These characteristics of adaptive-plastic rearrangements of cortical neuron activity in response to constant stimuli may result from intracortical cooperative interactions between the lemniscal and paralemniscal projection systems, which, overall, produces a precise qualitative assessment of the perceived stimulus in its specific context.