TRANSITION FROM ROD TO CONE VISION: II. Successive contrast

S tabell , B. & S tabell , U. Transition from rod to cone vision. II. Successive contrast. Scad J. Psychol., 1969, 10 137–139—Transition from chromatic rod to chromatic cone activity during dark adaptation is interpreted as a kind of color mixing.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION: Simultaneous color contrast

S tabell , U. & S tabell , B. Color threshold measurements in scotopic vision. III. Simultaneous color contrast. Scand J. Psychol ., 1968, 9, 133–137.—Color may be observed well below the break-point level of the dark adaptation curve, suggesting that the impulse pattern initiated in the rods may trigger a color-related response. Color is induced when the intensity of the inducing field reaches a certain level above the specific threshold, provided the stimulation of the test field is observable.     

Neuropsychological course after surgery for intracranial aneurysms. A prospective study and a critical review

Previously, only three studies with representative samples of patients with ruptured intracranial aneurysms have provided detailed results of prospective, repeated, neuropsychological assessments after surgery. These studies apparently disagree with regard to occurrence of cognitive deficits and to degree of improvement between early and delayed follow-ups. The present paper attempts to analyze the conditions underlying these differences in results. As a first step in this analysis we present a comprehensive, prospective, neuropsychological investigation of a consecutive sample of 41 patients with rupture of a supratentorial aneurysm, assessed 4 and 12 months after surgery. It is concluded that a prorated course of improvement of a wide specter of psychological functions may be revealed, but that sensitive tests and large samples are needed to establish the range of deficits and improvements with time. Differences in patient selection with respect to severity of the acute clinical state and delayed deterioration apparently contribute importantly to the discrepance in previously reported outcome.     

FACILITATION OF CHROMATIC CONE ACTIVITY BY ROD ACTIVITY

STABELL, U. & STABELL, B. Facilitation of chromatic cone activity by rod activity. II. Variation of chromatic-related cone activity. Scand. J. Psychol. , 1971, 12, 168–174.–At the cone-rod break of the dark adaptation curve, the specific threshold was found to drop to lower intensity levels, while the threshold curves of fovea proceeded in one step only, confirming the suggestion that rods may facilitate chromatic-related cone activity.     

CHROMATIC ROD VISION

STABELL, B. & STABELL, U. Chromatic rod vision. I. Wavelength of test-stimulation varied. Scand. J. Psychol. , 1971, 12, 175–178.–The ability to distinguish one type of radiation from another by its hue disappears in scotopic vision. Accordingly, scotopic hues are found to be invariant of variation of wavelength. It is concluded, on the basis of the Principle of Univariance, that hues may be triggered by light signals initiated in one type of receptor.     

CHROMATIC ROD AND CONE ACTIVITIES AS A FUNCTION OF THE PHOTOCHROMATIC INTERVAL

S tabbll , B. & S tabell , U. Chromatic rod and cone activities as a function of the photochromatic interval. Scand. J. Psychol ., 1969, 10,215– 219.—The Sco topic contrast color dominated for longer periods and at higher intensities the larger the magnitude of the photochromatic interval, indicating that the relative responsiveness of the chromatic rod to the chromatic cone activity increases as a function of the photochromatic interval.     

RODS AS COLOR RECEPTORS

The observance of color within the photochromatic interval has been shown to be possible. By pre-stimulating the subjects in a dark-adapted state, using Kodak Wratten Color Filters No. 70 (red), No. 73 (yellow) or No. 74 (green), and test-stimulating 30 sec. later with yellow, green, or blue filters at levels of intensity between the specific and absolute thresholds for these filters, it was found that they observed a blue or violet color.