Monocular Light Research Articles

Metabolic changes in the retina and the optic centres following monocular light deprivation in the new-born rat

Monocular light deprivation in new-born rats produces a significant decrease of acetylcholinesterase activity in the deprived retina and in the lateral geniculate nucleus connected with the closed eye; pseudocholinesterases are not affected. No differences in enzyme activity were detected in the superior colliculus and in the visual cortex. The results are briefly discussed with regard to the physiopathology of the functional amblyopia produced by chronic light deprivation.

The development of visually evoked electrocortical responses in the rat

AbstractThe development of electrocortical responses evoked by brief, focused monocular light stimulation was studied in 35 lightly anesthetized albino rat pups (Sprague‐Dawley strain) between birth and 35 days of age. A definite sequence of waveform changes occurred during maturation. The initial response at 10 to 11 days of age consisted of a long latency, negative wave. Subsequently, at approximately 12 days of age, a shorter latency, positive‐negative complex appeared. The initial, long latency, negative wave decreased rapidly in latency over the next few days until it coalesced with the negative component of the shorter latency, positive‐negative complex at about 15 days of age, resulting in a biphasic positive‐negative wave similar to that recordable in the adult rat. These results are compared and contrasted with a similar sequence observed in the developing kitten, and are discussed in terms of structural, electrophsiological, and behavioral maturation.

THE EFFECT OF MONOCULAR LIGHT STIMULATION UPON THE PERCEPTION OF THE BODY MIDLINE: A DEVELOPMENTAL STUDY.

Summary and Conclusions Changes in the perception of the body midline due to monocular light stimulation and starting position of the tactual stimulus are reported for four different age groups. In general, the effects are a function of age, sex, and the nature of the stimulus. The magnitude of directional shifts in the perceived midline is greatest at ages 7 and 68 and least at age 20. The direction of change is consistently toward the side of stimulation. At early ages females are clearly more influenced than males by the visual and tactual stimulus variables. Such findings are viewed within an organismic developmental framework.

Neural limitations of visual excitability. I. The time course of monocular light adaptation.

Monocular visual excitability was studied psychophysically by determining the threshold intensity for a small (40-min) brief (5-msec) “test” flash centered within a larger (3°) “conditioning” flash, both presented at 7° of arc in the temporal half-field. Interval between flashes was varied from −200 (test flash preceding onset of conditioning) to +1500 msec (test flash following), nine combinations of conditioning flash intensity and duration being used as parameters. For all combinations, threshold rose between −200 and −100 msec (before the start of the conditioning flash), reaching a maximum increment when the onsets of the two flashes were synchronized. When test was superimposed upon conditioning flash in time (positive intervals), threshold declined to approach an asymptote near the end of the latter flash. Following termination of the conditioning flash, threshold returned to resting level. The maximum rise in threshold, as well as the time taken to achieve an asymptote, varied with both intensity and duration of the conditioning flash. When a rough estimate of the photochemical contribution to these threshold changes was subtracted from the raw data, residual threshold increments were obtained and attributed to neural processes. On the basis of time course, it is suggested that these neural processes involve central (geniculocalcarine) as well as peripheral (neuro-retinal) factors.