How patterns of bleached rods and cones become visual perceptual experiences: A proposal

Abstract

In an attempt to increase information about how mammalian visual systems create a perceptual experience out of a retinal photochemical bleach pattern, this article brings together recent rat physiological data acquired with large electrodes, an old cat behavioral experiment, and two complex human behaviors: reading and the reversible blindness people experience when the scene being viewed is stabilized on the retinal surface. The outcome suggests this juxtaposition of disparate data sets has been logical, reasonable, and informative. The link between rats and reading is the fact that both rat and human retinas convert bleach patterns into ganglion cell volleys 3 times a second. The probable trigger for these episodic retinal volleys is a more or less abrupt change in the pattern of bleached rods and cones, and we claim the absence of this trigger when the image is stabilized is responsible for the blindness. The cat behavioral experiment correlates performance on visual discrimination tasks with the number of nerve fibers remaining after lesions of the optic tract. The analysis of the result, which shows that as few as 2% of the normal number of nerve fibers supports perfect performance of such tasks, prompts the concept of a second dynamic visual system, operating in parallel with the anatomical nervous system pictured in the textbooks. The dynamic visual system model, which brings into the foreground important old facts that have been neglected and integrates them with new data, offers a synthesis that may be useful in interpreting classical visual behavioral phenomena.retinal ganglion cell volleys ͉ stabilized image ͉ reading physiology ͉ optic tract lesion M ost human visual behavioral responses still lack convincing physiological explanations. A remarkable example of these is reading, that visual behavior children everywhere learn early and practice throughout a lifetime. But certainly the most mysterious example is the reversible blindness people report when a clever arrangement of mirrors negates the effect of eye movements, and the image in view is artificially maintained in exactly the same retinal location. Such images disappear within a second, and if the room in which the measurement takes place is lighted, the subject may ask who turned off the lights. This is the so-called stabilized image experiment, a sensory experience as surprising and improbable as any ever described.That a half-century of microelectrode measurements has so far failed to supply a satisfactory explanation for either of these visual perceptual phenomena suggests that crucial facts necessary for understanding them may lie beyond the reach of that technique. In an effort to do better with such problems, we have for the past decade been studying rats implanted with both a stimulus-producing device [remotely controlled light-emitting diodes (LED)] and relatively large electrodes that record the retinal and cortical activity the LED stimulation evokes (1, 2). The rats are free to move within a small testing box and are studied daily,...

Effects of the Hydroalcoholic Extract of Passiflora edulis on Anxiety Induced by Sub-acute Immobilization Stress

“…-Serotonin: The method which has been used is that described by Schlumpf and colleagues in 1974 [13]. On the other hand, the number of visits to the centre increased with all the doses of P. edulis groups, more significantly (p <0.001) at dose 100 mg/kg when compared to the negative control group (Fig.…”