Figure 12. Morphological cell types in lamina I.

All images are shown with the rostro-caudal axis oriented vertically. Panels on left show summed projections of confocal images of labelled neurons with the patch pipette still attached, as viewed in the original parasagittal plane with dorsal towards the left. Panels on right show 3-D reconstructions rotated 30–60 deg between parasagittal and horizontal planes such that morphology is optimally viewed for purposes of classification. Arrows point to axon-like processes. Letters in top right corner of each panel refer to the physiological classification of that cell: T, tonic; P, phasic; DO, delayed onset and SS, single spike. A, fusiform neurons had two primary dendrites emerging from opposite ends of a soma elongated in the rostro-caudal axis. B, pyramidal neurons had three primary dendrites emerging from separate points of a triangularly shaped soma. Summed projections (in the parasagittal plane) show the necessity of resolving cell geometry in the Z-axis for classification, lest pyramidal cells be misclassified as fusiform. C, multipolar neurons had at least four primary dendrites that tended to arborise quite extensively, resulting in comparatively high order branches existing in proximity to the soma.