CORRELATIONS BETWEEN THE RECEPTIVE-FIELD PROPERTIES AND MORPHOLOGY OFNEURONS IN THE DEEP LAYERS OF THE HAMSTER SUPERIOR COLLICULUS

Extracellular and intracellular recording, receptive field mapping, an d intracellular HRP injection techniques were used to define the morph ological classes of cells in the deep laminae of the hamster's superio r colliculus and to determine whether there are any correlations betwe en the structural and functional characteristics of these neurons. A t otal of 110 neurons were characterized and reconstructed. Of these, 23 .6% (N = 26) were visual, 60% (N = 66) were somatosensory, 0.9% (N = 1 ) were bimodal (visual-somatosensory), and 15.4% (N = 17) were unrespo nsive. Of the somatosensory neurons, 72.7% (N = 48) were low threshold , 4.5% (N = 3) had a wide dynamic range, 9.1% (N = 6) responded only t o noxious stimulation, and 13.6% (N = 9) had complex somatosensory rec eptive fields. Deep layer cells were divided into eight morphological classes. These classes were multipolar cells (26.4%, N = 29), bipolar cells (9.1%, N = 10), widefield vertical cells (7.3%, N = 8), horizont al cells (13.6%, N = 15), stellate cells (10.9%, N = 12), ventrally di rected cells (5.5%, N = 6), sparse radial cells (17.3%, N = 19), and s mall sparse radial cells (6.4%, N = 7). Four cells (3.6%) did not fit into this classification scheme. Univariate and multivariate analyses of variance of properties such as soma area, number of branch points, total dendritic length, and volume and orientation of dendritic arbor indicated that these classes were significantly different. However, ch i2 analysis and multivariate analysis of variance indicated no signifi cant relationships between morphological class and either laminar loca tion or receptive field type. There was a significant positive relatio nship between the possession of dendrites that extended into the super ficial laminae and visual responsivity. (C) 1993 Wiley-Liss, Inc.