Computerized three-dimensional stereotaxic removal of small central nervous system lesions in patients.

The authors describe the results of their recently reported computer-based stereotaxic surgical technique for the indentification, enhancement, three-dimensional reconstruction, localization, and removal of small central nervous system lesions. This technique has been applied to patients with various types of central nervous system pathology, and representative cases are reported.

A computerized microstereotactic method to approach, 3-dimensionally reconstruct, remove and adjuvantly treat small CNS lesions.

The authors update a novel method recently utilized in humans with various CNS pathology for stereotactic localization, removal, and adjuvant therapy of small CNS lesions using additional computer processing of the date from a GE 8800 CT Scanner. Multiple computer algorithms developed at Cal Tech enhance regions of interest by filtering, magnifying, color-coding and 3-dimensional reconstruction based on routine CT scans. This stereotactic approach is calculated by the computer and coordinates are mated to a modified head fixation system; small lesions can be removed with the apparatus described herein under direct binocular vision with minimal tissue damage. This technique may offer the possibility of successful secondary application of adjuvant therapy to, particularly, a CNS glioma site.

Spectral and polarization sensitivity of the dipteran visual system.

Spectral and polarization sensitivity measurements were made at several levels (retina, first and third optic ganglion, cervical connective, behavior) of the dipteran visual nervous system. At all levels, it was possible to reveal contributions from the retinular cell subsystem cells 1 to 6 or the retinular cell subsystem cells 7 and 8 or both. Only retinular cells 1 to 6 were directly studied, and all possessed the same spectral sensitivity characterized by two approximately equal sensitivity peaks at 350 and 480 nm. All units of both the sustaining and on-off variety in the first optic ganglion exhibited the same spectral sensitivity as that of retinular cells 1 to 6. It was possible to demonstrate for motion detection and optomotor responses two different spectral sensitivities depending upon the spatial wavelength of the stimulus. For long spatial wavelengths, the spectral sensitivity agreed with retinular cells 1 to 6; however, the spectral sensitivity at short spatial wavelengths was characterized by a single peak at 465 nm reflecting contributions from the (7, 8) subsystem. Although the two subsystems exhibited different spectral sensitivities, the difference was small and no indication of color discrimination mechanisms was observed. Although all retinular cells 1 to 6 exhibited a preferred polarization plane, sustaining and on-off units did not. Likewise, motion detection and optomotor responses were insensitive to the polarization plane for long spatial wavelength stimuli; however, sensitivity to select polarization planes was observed for short spatial wavelengths.

Fundamental properties of intensity, form, and motion perception in the visual nervous systems of Calliphora phaenicia and Musca domestica.

Several classes of interneurons in the optic lobes and brain of the insects, Musca domestica and Calliphora phaenicia, have been studied in detail. Visual stimuli have been categorized on the basis of the properties of intensity, form, and motion. Response characteristics of the classes of neural units are described with respect to these three classes of visual stimuli. While those units that detect motion in select directions have a tonic response, form detection units have a phasic response only. Through correlation of the responses of these classes with visual stimuli, it is shown that these units integrate the responses of other units which have very small visual fields. The small-field units are presumed to integrate the output of a small group of adjacent retinula cells and to respond differentially to intensity, form, and motion. It is shown that the response of both form and motion detection units is independent of the direction of pattern intensity gradation. As a consequence of this independence, it is further shown that failure to detect motion properly must start at a spatial wavelength four times the effective sampling station spacing rather than twice as has been predicted previously.