Structure-function correlation in transient amacrine cells of goldfish retina: basic and multifractal analyses of dendritic trees in distinct synaptic layers.

Amacrine cells generating light-evoked transient ON-OFF responses were stained by intracellular injection of horseradish peroxidase after determining their input-output (voltage response vs. light intensity) profiles. Ten cells specifically having bistratified dendritic trees were analyzed. The cross-sectional area of the dendrites in each sublamina (a and b) of the inner plexiform layer was initially measured. Although some variability was observed, there was no statistically significant overall difference in the cross-sectional areas of the dendritic trees in sublaminae a and b. Also, the amplitudes of the ON and OFF responses, generated by a midrange criterion stimulus, could not be correlated with the cross-sectional areas or the number of branches of the dendrites in sublaminae b and a, respectively. On the other hand, determination of the generalized fractal spectra revealed that the negative (up to -3) and zero-order fractal dimensions of the dendritic trees in sublamina a were consistently higher than those for sublamina b. Furthermore, there was a positive correlation between response amplitude and some part of the generalized fractal dimension in the respective parts of the dendritic trees. It is concluded that dendritic tree characteristics differ in the two halves of the inner plexiform layer and that these can be related to the cells' light-evoked response amplitudes. Furthermore, generalized fractal analysis appears to be a useful method for correlating structure and function in retinal amacrine cells with complex dendritic trees.

Interindividual variability of cranioencephalic relationships as predicted by CT.

To validate a procedure assembling CT scans in a three-dimensional (3D) array, the interindividual variability of cranioencephalic relationships, as estimated by our technique, was compared with that of the normal population. To this purpose the position of the habenulopineal complex (HPC) with respect to skull references was investigated in 41 normal subjects. In particular the x, y, and z, coordinates of individual HPCs were determined after each CT was assembled in a 3D multislice array. Thereafter, distances of the HPC from the frontal and occipital poles, the vault, and the base of the skull were measured and compared with the anatomicoradiological norms. From our estimates the distances of the HPC from both the frontal pole and the vault of the skull proved to vary as a function of the maximal skull diameter with no distortion of cranioencephalic relationships. The proposed assembling method can be regarded as a reliable tool for a quantitative evaluation of data collected from CT or other reconstructive tomography techniques in anatomicoclinical studies. This method enables a generalized (i.e., not confined to neurosurgical procedures) application of stereotactic principles.