Differential distribution of different classes of Necturus retinal ganglion cells.

The responses of Necturus retinal ganglion cells were recorded extracellularly. Each cell was characterized by its response type and the distance between its receptive field center and the center of the optic disc. There was a statistically reliable difference between the locations of sustained-ON cell and the locations of sustained-OFF and ON-OFF cells. Thus, the different classes of Necturus retinal ganglion cells are differentially distributed across the surface of the retina.

Principal components analysis of sources of variability in retinal ganglion cell responses.

An approach to the functional organization of retinal ganglion cell processing in terms of correlation matrices (Levine and Shefner, 1975; 1977a, b; Shefner and Levine, 1979) is extended by applying Principal Components Analysis. This analysis reduces each correlation matrix to a few components which are implicit in the data. The component loadings describe properties of the system in terms of loadings (correlations) of time bins on the underlying components. Each component is identified by the experimental conditions associated with the highest loadings. Mixed conditions are quantitatively interpreted as weighted contributions from the various identified components. This has led to new interpretations of existing data. Several properties of ganglion cell inputs are analyzed in this manner, including ON and OFF processes, center and surround mechanisms, rod and cone inputs, and spatially distinct areas within the receptive field center. Although the details vary, generally one of the components is highly associated with ON processes and the other with OFF and/or MAINTAINED processes. several advantages may be realized through the use of Principal Components Analysis: (1) all of the data contribute to the analysis, (2) the number and relative importance of contributing processes may be assessed, (3) the relative contribution of underlying processes to mixed responses may be assessed, and (4) the most parsimonious representation of the data is obtained.

X-like and Y-like ganglion cells in the Necturus retina.

The linearity of spatial summation within the receptive fields of Necturus retinal ganglion cells was examined with a counterphase-modulated split-field test stimulus. Modulation-locked histograms were constructed with the border at a variety of positions relative to the receptive field center. Most cells generated distinct, modulation-locked discharges when the border was 0.10 to 0.25 mm from the receptive field center. The discharges for more central border positions depended upon response type. Sustained-responding cells showed a sharp decrease in total response per cycle at the center position and increasing response for increasingly eccentric positions, i.e., nulling or X-like behavior. In contrast, the total response of transiently responding cells was largely independent of border position. For central positions of the border, these cells generated two bursts of impulses per cycle, i.e., frequency doubling or Y-like behavior.

Carcinoma of the oral cavity. An analysis of 478 cases.

Evaluation and analysis of 478 cases of carcinoma of the oral cavity treated from 1947 through 1970 shows a significant improvement in radiotherapy in the supervoltage (Co60) era. Survival in the early stages of disease (I and II) improved in the supervoltage era but not in the later stages of disease (III and IV). Results with combined therapy for advanced disease showed no significant difference from that of single mode therapy, whether with radiotherapy or with surgery in the supervoltage era.