Koiti Motokawa

MECHANISMS FOR THE TRANSFER OF INFORMATION ALONG THE VISUAL PATHWAYS.

Publisher Summary The chapter discusses the conduction of information along the visual pathway. The process of conduction is never completely isolated from the other visual functions. Receptive and central processes are also considered, but only as they augment the understanding of conduction. For convenience of presentation, separate sections are devoted to the retina, the lateral geniculate body, and the visual cortex. Other topics, such as color vision and pattern vision, are not amenable to such anatomic classification so separate sections are devoted to such topics. These sections show the form in which the relevant visual information is transmitted between and recordable from, various loci along the visual pathways. This chapter is also limited to properties of the vertebrate visual system. Following a photochemical reaction, a conductive nerve impulse is created in a secondary neuron probably a bipolar cell. Evidence are presented for the existence of the centrifugal fibers which carry impulses toward the retina, but the functional role of such fibers is still unknown. The anatomy and the electrical activity of the lateral geniculate body are described and the pre- and postgeniculate spikes are mentioned.

An investigation of the lateral spread of potentials in the octopus retina

Abstract A radial organization was found in the spread of the normally positive responses recorded from deep (near the sclera) portions of the octopus retina. Around a locally illuminated region, positive responses are recorded toward the center of the retina and negative responses toward the near periphery. A unique central area of the retina was also found.

Spectral Response Curves and Hue Discrimination in Normal and Color-Defective Subjects

Spectral response curves of normal and color-defective subjects were determined with the method of electric stimulation of the eye. The curves of anomalous trichromats consist of four components R, Y, G, and B, among which either R or G is especially weak. The curves of dichromats consists of three components; R and G are missing in the protanope and the deuteranope, respectively. The three kinds of response in the color-blind are definitely small compared with the corresponding normal responses. The magnitude of response of anomalous trichromats is intermediate between the normal and the color blind. Hue discrimination curves were obtained from one and the same subjects under comparable experimental conditions and interpreted in terms of spectral responses. From these experiments it was concluded that the yellow component plays a very important role in hue discrimination of color-defective subjects, whereas it is not so important for normal hue discrimination.

Studies of rod-process by polarization method.

Based upon differences in velocity of changes in electrical sensitivity of the eye after exposure to a flash of light, it is possible to isolate a rod-process from a mixture of cone- and rod-processes. By means of this method rod-responses to spectral lights were measured at 20° from the fovea as a function of wavelengths. The spectral distribution of rod-responses determined in this manner is found in satisfactory agreement with the scotopic visibility curve.Rod-responses to a flash of weak white light were measured at various parts of the retina. The spatial distribution of rod-responses so obtained is found to show close resemblance to the density distribution of rods in the retina, although the maximum of the former is displaced farther in the periphery beyond the maximum of the density as the intensity of the flash is reduced.

Central Mechanism of Vision

Publisher Summary This chapter describes the different aspects of central mechanism of vision. The transfer of the visual message at the dorsal nucleus of the lateral geniculate body and the modulation of color information at the central visual system are investigated. The lateral geniculate body is a prominent and well-defined thalamic nucleus with several distinct cell layers. Phylogenetically, this nucleus has been developed with the process of the encephalization of the visual function. The discharge rate in the pre- and postgeniculate neurons was expressed more quantitatively by the average frequency of response, which was determined by measuring the number of impulses in 300 or 600 ms from the onset or cessation of illumination. The applicability of the logical decision principle to the geniculate synapses can be also tested by comparing the spectral sensitivity curves of the pregeniculate and postgeniculate units. It is found that the responsiveness of radiation units to visual stimuli also changes with alteration in the animals waking state.

Die Beziehung zwischen Hautpotential uud Oxydation in der Froschhaut bei verschiedener Wasserstoffionen-konzentration des Mediums

Das Ruhepotential und der Sauerstoffverbrauch der Froschhaut wurden in der Ringerlosung mit verschiedener Wasserstcffionenkonzentration parallel zueinander untersucht, urn die Beziehung zwischen beiden Erscheinungen aufzuklaren. 1. Die beiden hangen von der Wasserstoffionenkonzentration in ganz derselben Weise ab; die Potential- bzw. O2-Verbrauch-pH-Kurve verlauft im grossen and ganzen M-formig, besitzt also zwei Maxima and ein Minimum, wobei sich das erste Maximum am neutralen Punkt und das zweite in der pH-Gegend von etwa 11-12 befindet. 2. Die H-oder OH-Ionen wirken im allgemeinen auf den O2-Verbrauch etwas milder als auf das Hautpotential. Die moglichen Ursachen hierfur wurden ausfuhrlich besprochen. 3. Der zeitliche Verlauf des Hautpotentials ist mannigfaltig und unter Umstanden sehr kompliziert, lasst sich aber doch mit der Gesetzmassigkeit in bezuf auf Gleichgewichtswerte in Zusammenhang bringen.