Behavioral manipulation of retrieval in a spatial memory task for Drosophila melanogaster

A paradigm for operant conditioning of freely walking single Drosophila flies has been described previously. A fly can be conditioned to avoid one side of a small test chamber if the chamber is heated whenever the fly enters this side. In a subsequent memory test without heat the fly continues to avoid the previously heat-associated side. In this experimental design one cannot exclude that flies mark the heated side by an odor that they subsequently avoid during the test. As a final proof for associative learning in the present experiment, flies are trained in one chamber and tested for learning in another, similar one. Handling in the transfer experiment interferes with memory display, even if the fly is returned to the old chamber instead of a new one. Memory can be reactivated, however, by subjecting the fly to an additional brief training (priming), which is too short to establish significant learning in naive flies. For efficient priming, heat has to be applied to the same side as during training in the old chamber. Only then the fly subsequently shows a side preference and avoids the side of the new chamber, which in the old one had been associated with heat. The two chambers are similar but not identical The transfer experiment therefore raises the question as to what the flies use as spatial reference during training and test. In the light, they can be shown to orientate according to visual landmarks associated with the chamber. In complete darkness, where training and memory scores do not differ from those in the light, they are assumed to use a combination of tactile and idiothetic information for orienting.     

A small-animal inhalation chamber for short-to-intermediate term exposure

An inhalation chamber for behavioral toxicology studies is described. Complete and uniform diffusion of test atmospheres throughout the chamber is achieved, thus solving a dead-airspace problem prevalent in extant chamber designs. Modular attachments to the chamber allow for a variety of uses, including physiological-pathological and classical or operant conditioning. The chamber design and size are appropriate for testing most small laboratory animals (e.g., birds, rodents, and small primates), but the chamber is easily modified for use with larger vertebrates. Despite the versatility of design, the chamber is relatively inexpensive and easy to build.     

Post-Conditioning Devaluation of an Instrumental Reinforcer has no Effect on Extinction Performance

The extent to which a representation of the reinforcer controls an instrumental response can be assessed by studying the effect of post-conditioning changes in the reinforcer value. In the first experiment rats were trained to press a lever for sucrose pellets on a variable-interval (VI) schedule. The sucrose was subsequently devalued by pairing with Lithium Chloride (LiCl). This had no effect on lever pressing in extinction, although it profoundly reduced reacquisition responding and consumption. In Experiment II rats were trained to shuttle between the two distinctive chambers of a choice-box, in which lever pressing was reinforced in one chamber by sucrose and in the other chamber by food pellets programmed on independent VI schedules. A LiCl-induced taste-aversion was conditioned to the sucrose, and although this markedly affected reacquisition, extinction responding in the sucrose chamber and chamber preference were unaffected. These results indicate that instrumental performance can be independent of the current value of the reinforcer, and are discussed with reference to stimulus-response theory and second-order Pavlovian conditioning.     

The effect of the size of the test environment on behavior under two temporally defined schedules

The effect of the size of the floor area of the operant test chamber on behavior was tested using a standard-size test chamber and a test chamber with one-fourth of the floor area of the standard chamber. Two groups of pigeons were tested under a differential-reinforcement-of-low-rate 15-sec schedule or a variable-interval 60-sec schedule. Both groups of pigeons had higher response rates while in the smaller floor area. Pigeons under the differential-reinforcement-of-low-rate schedule also showed a decrease in rate of reinforcement, an increase in ratio of responses to reinforcements, and an alteration in interresponse-time-per-opportunity distributions when tested in the reduced floor-area condition. These effects are similar to those found under physical restraint, indicating that amount of floor space available for locomotion interacts with schedule behavior and that physical restraint may be regarded as the lower limiting value of amount of floor area available for locomotion.     

Social buffering in rats: prolactin attenuation of active interaction

Stress may result when the present environment is interpreted as threatening, and stress is known to increase the prolactin-secretory response. In the present study, rats (N=83) were exposed to a conditioned-fear paradigm (environment paired with footshock), and on testing day, rats were exposed to the experimental chamber without shock while alone (Alone n=16), with an object (Object n=17), with a euthanized conspecific (Euthanized n=16), or with a social partner (Social n=19). The control group (Control n=15) was exposed to the experimental chamber but was never shocked. The Control group had significantly lower levels of prolactin than the Alone, Object, and Euthanized groups; however, the Control group's levels of prolactin were not significantly different than that of the Social group, which was significantly lower than that for the Alone group. Social interaction decreased fear independent of the distraction provided by a stimulus in the chamber. Active touch appeared to be crucial for social buffering to occur.     

A yoked-chamber comparison of concurrent and multiple schedules: the relationship between component duration and responding

Two experimental chambers were electrically connected so that the component selected by a pigeon confronting concurrent variable-interval schedules in one chamber could be successively presented as a multiple schedule to a second pigeon in the other chamber. Component duration was regulated by the use of a changeover delay, the value of which was systematically varied between 0 and 30 sec. It was found that the relative local response rates on the preferred key (absolute response rate to that component divided by the sum of the absolute response rates during both components) tended to increase with increasing component durations for the birds in the concurrent chamber, but decreased for the birds in the multiple chamber. These data support the interpretation that there are fundamental differences in the mode of responding to multiple and concurrent schedules. Based on these findings, it was concluded that previous demonstrations of matching on multiple schedules do not establish that response allocation is controlled by a process equivalent to that found on choice paradigms. It now appears that matching on multiple (but not concurrent) schedules is a consequence of selecting short component durations. The implications of these data for Herrnstein's (1970) and Rachlin's (1973) formulations of the relationship between multiple and concurrent schedules are examined.     

The Other Shoe: An Early Operant Conditioning Chamber for Pigeons

We describe an early operant conditioning chamber fabricated by Harvard University instrument maker Ralph Gerbrands and shipped to Japan in 1952 in response to a request of Professor B. F. Skinner by Japanese psychologists. It is a rare example, perhaps the earliest still physically existing, of such a chamber for use with pigeons. Although the overall structure and many of the components are similar to contemporary pigeon chambers, several differences are noted and contrasted to evolutionary changes in this most important laboratory tool in the experimental analysis of behavior. The chamber also is testimony to the early internationalization of behavior analysis.     

Memories in drosophila heat-box learning

Learning and memory processes of operant conditioning in the heat-box are analyzed. In a search for conditioning parameters leading to high retention scores, intermittent training is shown to give better results than those of continuous training. Immediate retention tests contain two memory components, a spatial preference for one side of the chamber and a “stay-where-you-are-effect.” Intermittent training strengthens the latter. In the second part, memory dynamics is investigated. Flies are trained in one chamber and tested in a second one after a brief reminder training. With this direct transfer, memory scores reflect an associative learning process in the first chamber. To investigate memory retention after extended time periods, indirect transfer experiments are performed. The fly is transferred to a different environment between training and test phases. With this procedure, an aftereffect of the training can still be observed 2 h later. Surprisingly, exposure to the chamber without conditioning also leads to a memory effect in the indirect transfer experiment. This exposure effect reveals a dispositional change that facilitates operant learning during the reminder training. The various memory effects are independent of the mushroom bodies.     

A chamber for separating visual and physical prey access from predators

A chamber is described that provides automated separation of various phases of depredation dynamics. Two solenoid actuated doors control visual and physical access to prey items. A lever operandum is programmable to require differential response outputs by the predator. Search lever responses open one door and allow detection which may then be followed by pursuit lever responses and ultimate access for capture. The chamber is suitable for such medium sized predators as foxes and coyotes.     

Meadow voles, <Emphasis Type="Italic">Microtus pennsylvanicus</Emphasis>, have the capacity to recall the “what”, “where”, and “when” of a single past event

Some non-human animals may possess the ability to recall the “what”, “where”, and “when” of a single past event. We tested the hypothesis that male meadow voles posses the capacity to recall the “what”, “where”, and “when” of a single past event associated with mate selection in two experiments. Briefly, male voles were allowed to explore an apparatus that contained two chambers. One chamber contained a day-20 pregnant female (24 h prepartum). The other chamber contained a sexually mature female that was neither pregnant nor lactating (REF female). Twenty-four hour after the exposure, the males were placed in the same apparatus, which was empty and clean. At this time, the pregnant female would have entered postpartum estrus (PPE), a period of heightened sexual receptivity. Males initially chose and spent significantly more time investigating the chamber that originally housed the pregnant female (now a PPE female) than the chamber that originally housed the REF female. Male voles also explored an apparatus containing a chamber with a PPE female and one chamber containing a REF female. Twenty-four hour later, males were placed into an empty and clean apparatus. The males did not display an initial choice and they spent similar amounts of time investigating the chamber that originally housed the PPE female (now a lactating female) and the chamber that originally housed the REF female. The results of these and additional experiments suggest that male voles may have the capacity to recall the “what”, “where”, and “when” of a single past event, which may allow males to remember the location of females who would currently be in heightened states of sexual receptivity.     

The Elusiveness of Gustatory Potentiation of an Environmental Aversion

Two experiments investigated conditions that influence whether or not the presence of a flavor cue potentiates acquisition of an environmental aversion. Experiments 1 and 2 exposed rats to either a salient sucrose flavor or nonsalient water with black box-illness pairings. Half of the rats in the sucrose and water treatment groups became ill after exposure to the black chamber in their home cage. The other half of the rats in the two treatment conditions became ill in the black box. The results of each study indicated that a strong environmental aversion was established when illness was associated with exposure to the black box. The aversiveness of the black chamber was indicated by both less time spent in the black side and reduced intake in the black chamber. The presence of sucrose during conditioning did produce a stronger black box aversion than did water. Reliable potentiation of the environmental aversion, however, was seen only when the illness experience occurred in the black chamber but not when illness occurred in the home cage. A weaker aversion to the black chamber was also found in the water groups when illness occurred shortly after experience with the black box than when illness immediately followed exposure to the black chamber.

     

A method for the objective study of tool-using behavior

Key pecking for food was shaped in four crows within a conventional operant-conditioning test chamber. When pecking stabilized, a metal screen with openings 2.5 cm high by 1.0 cm wide, was placed over the response key, so that the crow could still see but could no longer peck the key. At the same time, several dozen wooden matchsticks, which could be used to operate the key, were placed in the test chamber. The crows made no use of these during 50 to 75 hr of exposure to this condition. Subsequently, the behavior of two crows was shaped so that they approached the matchsticks, picked one up in their beaks, approached the response key with the matchstick in their beak, and finally operated the response key by poking the matchstick through the screen. This shaping procedure was ineffective with the two other crows. However, these birds were successfully trained through positional fading of the tool. This involved suspending a metal rod from the ceiling so that it hung directly in front of the response key, and the crow had only to peck it to operate the key. Then, the rod was gradually lowered by lengthening its tether until it eventually rested on the floor of the test chamber. The principal advantage of this methodology is the automatic recording of the terminal (tool-using) behavior under study.     

Still no evidence for visual discrimination learning: A reply to Lett

Neither of the points made by Lett (1977) regarding the data from my experiments (Roberts, 1976) can be taken as evidence of visual discrimination learning with a 1-min delay of reward. If it is concluded that the Lett Group of my second experiment improved over blocks of trials but the other three groups tested in my experiments did not, this can lead only to the conclusion that rats in my Lett Group and in Lett's original experiment (Lett, 1974) improved on the basis of odor cues and not associations between chamber brightness and reward. The significantly higher frequency of initial choices of the black chamber found for black-rewarded animals over white-rewarded animals is shown to result from differential rates of stimulus satiation for animals whose initial chamber preferences agree or disagree with their designated S+.     

Attention and “visual field dependency” in the pigeon

Three pigeons were trained in an upright conditioning chamber to peck a key transilluminated by a vertical line. This training was followed by a line orientation generalization test. During the test, the chamber was tilted laterally 22.5 degrees from upright. The chamber floor remained horizontal with respect to gravity. Under these conditions, the subjects responded more often in the presence of a visually vertical (parallel to chamber walls) line orientation than in the presence of a gravitationally vertical line orientation. Subsequent reinforcement of pecking in the presence of a line that was always gravitationally vertical but not always visually vertical temporarily abolished this "visual field dependency" and resulted in generalization gradients with peak responding in the presence of the gravitationally vertical line orientation. The results are discussed in terms of selective attention to the gravitational and visual components of line orientation.     

Lightness constancy: a direct test of the illumination-estimation hypothesis

Many models of color constancy assume that the visual system estimates the scene illuminant and uses this estimate to determine an object's color appearance. A version of this illumination-estimation hypothesis, in which the illuminant estimate is associated with the explicitly perceived illuminant, was tested. Observers made appearance matches between two experimental chambers. Observers adjusted the illumination in one chamber to match that in the other and then adjusted a test patch in one chamber to match the surface lightness of a patch in the other. The illumination-estimation hypothesis, as formulated here, predicted that after both matches the luminances of the light reflected from the test patches would be identical. The data contradict this prediction. A second experiment showed that manipulating the immediate surround of a test patch can affect perceived lightness without affecting perceived illumination. This finding also falsifies the illumination-estimation hypothesis.     

Schedule-induced polydipsia suppresses pituitary-adrenal activity in rats

The effects of schedule-induced polydipsia (SIP) on pituitary-adrenal activity, as indicated by plasma levels of corticosterone, were examined in a series of experiments. Male (Experiments 1 and 3) and female (Experiment 2) rats were reduced to 80% of their free-feeding weight and given daily sessions on an intermittent-feeding schedule (fixed time of 60 sec). Half of the subjects in each experiment had water available during experimental sessions and the other half did not. Animals with water available in the experimental chamber exhibited SIP in all three experiments. In Experiment 1, blood samples were collected following (a) food consumption in the home cage, (b) a session on FT 60 sec, and (c) a session with pellets available in a cup in the experimental chamber. In Experiment 2, blood samples were taken prior to and following an FT 60-sec session, and following a session with pellets available in a cup in the chamber. In Experiment 3, pre- and postsession samples were obtained as in Experiment 2 (Part A). Subsequently, the opportunity to drink during sessions was removed, and the effect on corticoids was examined (Part B). The results indicate that (a) schedule-induced drinking suppresses pituitary-adrenal activity, (b) corticoid suppression may become a conditioned response to drinking in the chamber, and (c) corticoids return to presession levels following removal of water from the chamber. In view of these findings, it is hypothesized that SIP may serve an arousal-reducing role in intermittent-feeding situations.     

Recent advances in operant conditioning technology: a versatile and affordable computerized touchscreen system.

We report the construction of a new operant chamber that incorporates modern computer, touchscreen, and display technologies. An LCD display was housed in the front wall of a lightweight Plexiglas chamber. An Apple eMac computer was used to present visual stimuli on the monitor and to control other chamber events. Responses to the stimuli were recorded using a transparent resistive-type touchscreen that overlaid the monitor. The resulting system is simple and inexpensive to construct but powerful and flexible enough to explore a broad range of issues in animal learning and behavior.     

A yoked-chamber comparison of concurrent and multiple schedules

Pigeons were exposed to alternative pairs of variable-interval schedules correlated with red and green lights on one key (the food key). In one experimental chamber, responses on a white key (the changeover key) changed the color of the food key and initiated a 2-sec changeover delay. Pigeons in a second chamber obtained food by pecking on a colored key whenever the pigeons in the first (concurrent) chamber had obtained food for a peck on that key color. There was no changeover key in the second (multiple) chamber: changeover responses in the first chamber alternated the schedules and colors in both chambers. The pigeons in both chambers emitted the same proportion of responses on each of the variable-interval schedules, and mastered discrimination reversals at the same rate. The pigeons differed only in their absolute response rates, which were greater under the concurrent schedules. In a second experiment, changes in key color occurred automatically, with different proportions of time allocated to the two variable-interval schedules. Matching of relative response frequency to relative reinforcement frequency was affected by the relative amounts of time in each component, by rate of changeovers, and by manipulations of the variable-interval scheduling.     

Recent advances in operant conditioning technology: A versatile and affordable computerized touchscreen system

We report the construction of a new operant chamber that incorporates modern computer, touchscreen, and display technologies. An LCD display was housed in the front wall of a lightweight Plexiglas chamber. An Apple eMac computer was used to present visual stimuli on the monitor and to control other chamber events. Responses to the stimuli were recorded using a transparent resistive-type touchscreen that overlaid the monitor. The resulting system is simple and inexpensive to construct but powerful and flexible enough to explore a broad range of issues in animal learning and behavior.     

An integrated circuit shock scrambler

The construction of an inexpensive shock scrambler is described. The device uses integrated circuitry to drive switching transistors which, in turn, operate mercury relays. These relays are used to switch high voltage to the shock grids in a standard experimental chamber. The frequency at which shock can be scrambled across the grids can be varied.