A circadian variable in self-exposure to light by the rat

Abstract

Determinations of illuminance preference of rats have been made by Lockard (1962Lockard ( , 1963 and by Johnson (1%4, 1965). Using bar pressing and locomotor response measures respectively, data obtained by these investigators differ in support of a preference hypothesis (Lockard & Lockard, 1964) suggesting a range of dim illuminations which have greater preference value than darkness. A confounding issue is the reinforcement value of stimulus change which, as Johnson (1965, p. 541) noted, varies in specific relationship to apparatus and procedure used; the effect of the variable of illumination change is apparently reduced with a locomotor response and increased with a bar-press response.The issue of organismic need for stimulus change is generally related to the theories stemming from sensory deprivation (Brownfield, 1965) and perceptual organization by active involvement (Gibson, 1966). As SoUberger (1965, p. 26) states, the animal in the field as well as man himself "builds his own environment to such an extent that it is truly an extension of himself. "The primary objective was to determine the rat's ability to place himself on a circadian cycle of light and dark. According to Lockard (1963) "It would not be unreasonable to expect self-produced periods of light and dark to bear an orderly relationship to the circadian locomotor periodicity characteristic of many rodents. Were this so, the motivation for bar pressing for light would be associated with the maintenance of a rhythmic system and the light begins to resemble a 'primary need' more than a mere sensory change [po 522).".. -- Subject. The S was a male hooded rat (four months old) of the Long Evans strain. Prior to this study S was maintained in an individual cage on a constant light schedule of 12 h dark and 12 h light (1-5 ft"i: depending on location of meter probe).Apparatus. The cage housing was a light-tight wooden box (75 x 75 x 87 cm) with 10 W incandescent lamps mounted on the ceiling with a Fresnel lens and a white translucent, vinyl plastic sheet suspended under the lamps as diffusers. A fan and baffled intake and exhaust ports allowed for adequate ventilation. Room temperature (mean = 72 deg F, ± I deg F) and humidity (mean = 42.2 deg RH, SD 4.7 deg RH) were con· trolled and measured intermittently to assure no daily periodicity.On the floor of the wooden surround and 66 em under the diffusers a transparent plastic cage (38 x 25 x 15 cm) was fitted with two levers located at opposite ends of the box 5 cm from the floor. Any bar press altered the light (1-2 ft-c) to dark or the reverse by use of a ratchet relay. A capacative-discharge circuit prevented bar holding artifacts.A 20 pen event recorder was used as a cumulative counter and a milliammeter recorder was used to detect light alterations within the chamber as sensed by a Delco LDR-25 photoresistive cell installed as one arm of a Wheatstone bridge circuit and located on the floor of the surround next to the cage. The purpose of the milliammeter recording was to facilitate data analysi...

Light reinforcement in four taxa of deer mice (Peromyscus).

“…periodicities have ,. been limited to one rat subject (Thor & Hoats, 1968), ;our results; are included here. Most subjects exhibited circadian onsets of activity , similar , to those expected from nocturnal, animals kept in constant darkness (Aschoff, 1965), i.e., day length shorter than 24 hr.…”

Rodent control of chamber brightness leads to the emergence of unique circadian rhythms

“…However, contemporary life is not merely subject to the daily rhythms of nature; we can alter our environment to match our internal state, creating a reciprocal loop between the environment and bodily rhythms. The mutual entrainment of these different rhythms may generate a new emergent circadian rhythm 7,8 that could alter our behavior and cognition. However, few studies have identi ed such emergent rhythms and evaluated their behavioral, physiological, and cognitive effects.…”

Some effects of short-term immediate prior exposure to light change on responding for light change

“…From the limited evidence available, Kish (1966) concluded that the most parsimonious way of viewing sensory reinforcement behavior was in terms of "a single 'stimulus hunger' or drive for stimulation rather than a series of drives specific to different test situations, or sensory modalities, or perhaps both [p. 127] ." Others have also postulated a single general need for stimulus change in accounting for sensory reinforcement (e.g., Isaac, 1962;Frieman, 1967; Thor & Hoats, 1968). The basis for this need is often in terms of a parallel between the sensory deprivation studies (e.g., Brownfield, 1965) and the research on curiosity-exploratory behavior, with both phenomena seen as stemming from a general need for exteroceptive stimulus change (e.g., Jones, 1966;Riesen, 1966;Schultz, 1965Schultz, , 1967.…”