Defense posture and leg-position learning in a primitive insect utilize catchlike tension

The capability for conditioning of leg position, using loud sound as an aversive natural reinforcement, was examined in a primitive New Zealand insect, the weta (Orthoptera: Stenopelmatidae). Electromyographic recordings were made during the conditioning. A majority of wetas tested came to occupy stably a metathoracic tibial position window, coupled to turning off the sound, set in either flexion or extension away from the preferred rest position. Steady tensions of up to 7 g in extension and 5 g in flexion were produced. However, no electromyographic activity accompanied the tension. It is concluded that the insects are using a peripheral catchlike mechanism to adjust posture.     

Leg position learning by an insect. I. A heat avoidance learning paradigm

A new learning paradigm which employs a natural aversive stimulus, tightly constrains learned behavior and demonstrates learning in individual animals is described. Locusts were restrained so that only the femoro-tibial joint of a single metathoracic leg was free to move. Animals were required to maintain a particular range of femoro-tibial joint angle to avoid heating of the head. The position of the tibia was sampled by an on-line computer which set the limits of joint angle and controlled the aversive stimulus while storing data for further analysis. Control animals received patterns of aversive stimuli identical to those received by experimental animals but independent of their own joint position. Quantitative evaluation of the learned behavior of individual animals allowed the identification of three different behavioral strategies by which learning was achieved.     

Association of an acoustic signal with operant conditioned feeding responses in thicklipped mullet, Crenimugil labrosus (Risso) and common carp, Cyprinus carpio (L.)

Groups of both carp, Cyprinus carpio , and mullet, Crenimugil labrosus , learned to associate a 250 Hz sine wave generated acoustic singnal with a previously conditioned trigger pressing operant response for food. Within 48 h, a programmed signal of 5 min duration in every 1 h period was stimulating trigger responses for food reward, whilst during other periods not associated with sound there were few responses.     

Learning of leg position in the shore crab,carcinus maenas

Decerebrate crabs were trained to raise their legs to avoid electric shocks. Compared with yoked controls, experimental crabs received significantly fewer shocks after 6–7 minutes training and also during the first minute of a subsequent testing period when both experimental and control crabs were in a training situation. There was considerable variation in the performance of different crabs. Some learned quickly, some slowly, while others did not learn at all. In some, the raised leg position was maintained without further reinforcement. In others, periods when the animal was receiving few shocks were interrupted by periods when the leg was lowered and several shocks were received. A variety of leg movements were utilised by crabs to avoid shocks, the most common being flexion at the mero‐carpopodite joint.     

Der „Kniesehnenreflex” bei Carausius morosus: Übergangsfunktion und Frequenzgang

Stretching and releasing the femoral chordotonal organ caused by a movement of the tendon of the organ gives rise to a movement of the tibia. This reaction is called Kniesehnenreflex (knee-tendon-reflex). Its step response can be described in the following manner: After a certain reaction-time (at flexion 0.02–0.06 sec, at extension 0.06–0.2 sec) the tibia moves with a maximum speed between 150°/sec and 1000°/sec at extension and between 20°/sec and 450°/sec at flexion. The amplitude of the movement and the maximum speed of tibia movement are correlated. After reaching the extreme position the tibia returnes nearly to its starting-point with half lifes of 3–58 sec after a flexion and 7–232 sec after an extension. — The frequency response shows a strong decrease of the amplitude of the tibia at about 1 Hz. Above 2 Hz the amplitude is only a few degrees. The phase shift between stimulus and reaction increases with increasing frequency. Big individual differences are observed. A step stimulus, which is given in addition to a sinoidal stimulus causes a response at all frequencies. — Slow stretching and releasing the chordotonal organ with constant speeds causes movements of the tibia even at stimulus speeds of 0.002 mm/min. — It is discussed: the significance of the results for the theory of the control mechanism at walk, the stability of the control system in connection with the rocking-movements of the animal and the control of Flexibilitas cerea.     

Effects of antianxiety and antipsychotic drugs on DRL responding for brain stimulation

Satiated rats could be trained to give stable rates of responding for rewarding stimulation of the lateral hypothalamus delivered on differential reinforcement of low rate (DRL) schedule requiring 2 to 8 sec interresponse intervals for reinforcement (DRL-2 to 8). The performance on a DRL-8 schedule was tested 30 min after the oral administration of benzodiazepines. Diazepam (5 and 10 mg/kg) and meprobamate (200 mg/kg) caused significant increases in response rates during the first 5 min of a session, but not thereafter. Bromazepam (1 and 5 mg/kg) also caused a significant increase in the rates during the first and second 5 min. On the other hand, chlorpromazine (20 mg/kg) caused no effect in the first 5 min but decrease in second and third 5 min. These results indicate that DRL schedules with a brain stimulation reward provided a useful tool for evaluation of antianxiety drugs. The advantage of the brain stimulation reward over food reward is that the possible effects of the drugs on hunger motivation need not be considered.     

Insect rope-walkers: kinematics of walking on thin rods in a bug, Graphosoma italicum (Heteroptera, Pentatomidae)

Leg positions during walking on a plane and on thin rods were recorded by photography, videorecording, and videokymography. Joint angles were reconstructed from the tibia-ending position, using a 3-D model of the body. Participation of leg joints in propulsion was analysed by calculating the partial derivatives of tibia end-point position on different joint angles. Adjustment to walking with a narrow ground base is achieved by additional femur depression and flexion of the tibia in the stance phase. In the swing phase, the leg is raised by the same amount as when walking on a plane, but not to the same superior position, as on a plane. The contribution of the subcoxal joint to body propulsion is 64-94% in fore-and middle legs and 22-49% in hind legs. The oblique alignment of the coxal pivot within the thorax helps maintain a long stride for variable ground bases. In Graphosoma , it is close to the optimal position: according to several criteria, the angle between the coxal axis and the body vertical shall be arctan π/2, or ∼ 57.5°.     

Arterial blood pressure and heart rate changes during self-stimulation by dogs in the basal forebrain region, lateral preoptic area, hypothalamus, ventral midbrain and amygdala.

In dogs pressing a lever for a brain-stimulation reward, arterial blood pressure (ABP) was elevated for 20 out of 24 sites tested, but this effect was usually conspicuous only at twice the threshold current sustaining stable performance. Hypertension was seen only in one ventral tegmental and two hypothalamic sites. In three anterior placements the ABP and heart rate (HR) increased more upon a fixed ratio than on continuous reinforcement. In most sites, self-stimulation was accompanied by cardiac acceleration; however, in some placements the HR was similar to or even less than control values. Continuous stimulation (5-10 sec) at one nucleus accumbens and four hypothalamic sites by the experimenter was aversive and produced a clearcut pressor response. The cardiovascular changes seem to depend on a spread of current to brain centres controlling circulatory functions and also, to some extent, on the animal's motor activity. The results contradict the claim that a causal relationship exists between the autonomic concomitants of self-stimulation and the intrinsic nature of the brain-stimulation reward.     

Is avoiding an aversive outcome rewarding? Neural substrates of avoidance learning in the human brain

Avoidance learning poses a challenge for reinforcement-based theories of instrumental conditioning, because once an aversive outcome is successfully avoided an individual may no longer experience extrinsic reinforcement for their behavior. One possible account for this is to propose that avoiding an aversive outcome is in itself a reward, and thus avoidance behavior is positively reinforced on each trial when the aversive outcome is successfully avoided. In the present study we aimed to test this possibility by determining whether avoidance of an aversive outcome recruits the same neural circuitry as that elicited by a reward itself. We scanned 16 human participants with functional MRI while they performed an instrumental choice task, in which on each trial they chose from one of two actions in order to either win money or else avoid losing money. Neural activity in a region previously implicated in encoding stimulus reward value, the medial orbitofrontal cortex, was found to increase, not only following receipt of reward, but also following successful avoidance of an aversive outcome. This neural signal may itself act as an intrinsic reward, thereby serving to reinforce actions during instrumental avoidance.     

Instrumental and classical reflexes with water reinforcement]

Thirsty dogs were learned to regulate the supply of water by flexing the paw. The movement was effective only during an acoustic stimulation, either immediately at its beginning, or 10 to 20 sec. after its isolated action. The acoustic signal produced both flexion of the paw (instrumental reflex) and rhythmic swallowing movements which preceded the moment when water was fed into the mouth (classical conditioned reflex). The effect of prolongation of the isolated acoustic stimulation was manifested with extinction of the classical conditioned reflex and activation of the instrumental one.     

Role of different projection areas of the motor cortex in reorganization of the innate head-forelimb coordination in dogs

Dogs were trained to perform the forelimb tonic flexion in order to lift a cup with meat from a bottom of the foodwell and hold it during eating with the head bent down to the cup. It is known that conditioning of the instrumental reaction is based on reorganization of the innate head-forelimb coordination into the opposite one. In untrained dogs, the forelimb flexion is accompanied by the anticipatory lifting of the head bent down to the foodwell. The following lowering of the head leads to an extension of the flexed forelimb. Tonic forelimb flexion is possible if the head is in the up position. Simultaneous holding of the flexed forelimb and lowered head providing food reinforcement is achieved only by learning. It was shown earlier that the lesion of the motor cortex contralateral to the "working" forelimb led to a prolonged disturbance of the elaborated coordination and reappearance of the innate coordination. In the present work we studied the influence of local lesions of the projection areas in the motor cortex, such as a "working" forelimb area, bilateral representation of the neck, and the medial part of the motor cortex, on the learned instrumental feeding reaction. It was found that only the lesion of the forelimb but not neck projection led to a disturbance of the learned head-forelimb movement coordination.     

Interval time-place learning by rats: varying reinforcement contingencies

Two experiments with rats were conducted to study interval time-place learning when the spatiotemporal contingencies of food availability were more similar to those likely to be encountered in natural environments, than those employed in prior research. In Experiment 1, food was always available on three levers on a variable ratio (VR) 35 schedule. A VR8 schedule was in effect on Lever 1 for 5 min, then on Lever 2 for 5 min, and so forth. While rats learned to restrict the majority of their responding to the lever that provided the highest density of reinforcement, they seemed to rely on a win-stay/lose-shift strategy rather than a timing strategy. In Experiment 2, the four levers provided food on variable ratios of 15, 8, 15, and 30, each for 3 min. As expected the rats learned these contingencies. A novel finding was that the rats had a spike in response rate immediately following a change from a higher to lower reinforcement density. It is concluded that rats exposed to spatiotemporal contingencies behave so as to maximize the rate of obtained reinforcement.     

Influences of rewarding and aversive outcomes on activity in macaque lateral prefrontal cortex

Both appetitive and aversive outcomes can reinforce animal behavior. It is not clear, however, whether the opposing kinds of reinforcers are processed by specific or common neural mechanisms. To investigate this issue, we studied macaque monkeys that performed a memory-guided saccade task for three different outcomes, namely delivery of liquid reward, avoidance of air puff, and feedback sound only. Animals performed the task best in rewarded trials, intermediately in aversive trials, and worst in sound-only trials. Most task-related activity in lateral prefrontal cortex was differentially influenced by the reinforcers. Aversive avoidance had clear effects on some prefrontal neurons, although the effects of rewards were more common. We also observed neurons modulated by both positive and negative reinforcers, reflecting reinforcement or attentional processes. Our results demonstrate that information about positive and negative reinforcers is processed differentially in prefrontal cortex, which could contribute to the role of this structure in goal-directed behavior.     

In vivo measurement of translational stiffness of rabbit knees

This paper describes the design, evaluation, and preliminary results of a specialized testing device and surgical protocol to determine translational stiffness of a rabbit knee, replicating the clinical anterior drawer test. Coronal-plane transverse pins are inserted through the rabbit leg, two in the tibia and one in the distal femur, to hold and reproducibly position the leg in the device for tests at multiple time points. A linear stepper motor draws the tibia upward then returns to the home position, and a load cell measures the resisting force; force-displacement knee stiffness is then calculated. Initial evaluation of this testing device determined the effects of preconditioning, intra-operator repeatability, rabbit-to-rabbit variability, knee flexion angle (90 degrees vs. 135 degrees ), and anterior cruciate ligament (ACL) sectioning (0%, 25%, 50%, 75%, 100%). Knee stiffness generally decreased as ACL sectioning increased. This testing device and surgical protocol provide an objective and efficient method of determining translational rabbit knee stiffness in vivo, and are being used in an ongoing study to evaluate the effect of knee instability (via partial to complete ACL sectioning) on the development of post-traumatic osteoarthritis.     

Articular contact at the tibiotalar joint in passive flexion

The knowledge of the contact areas at the tibiotalar articulating surfaces during passive flexion is fundamental for the understanding of ankle joint mobility. Traditional contact area reports are limited by the invasive measuring techniques used and by the complicated loading conditions applied. In the present study, passive flexion tests were performed on three anatomical preparations from lower leg amputation. Roentgen Stereophotogrammetric Analysis was used to accurately reconstruct the position of the tibia and the talus at a number of unconstrained flexion positions. A large number of points was collected on the surface of the tibial mortise and on the trochlea tali by a 3-D digitiser. Articular surfaces were modelled by thin plate splines approximating these points. Relative positions of these surfaces in all the flexion positions were obtained from corresponding bone position data. A distance threshold was chosen to define contact areas. A consistent pattern of contact was found on the articulating surfaces. The area moved anteriorly on both articular surfaces with dorsiflexion. The average position of the contact area centroid along the tibial mortise at maximum plantarflexion and at maximum dorsiflexion was respectively 58% posterior and 40% anterior of the entire antero-posterior length. For increasing dorsiflexion, the contact area moved from medial to lateral in all the specimens.     

Food aversion learning in the polyphagous grasshopper Schistocerca americana

ABSTRACT. The ability of the acridid Schistocerca americana (Drury) (Orthoptera: Acrididae) to learn to avoid a food when it is associated with an artificial aversive stimulus was examined. The aversive stimulus used was an injection of nicotine hydrogen tartrate at a concentration which usually did not cause knockdown. Insects learned to avoid a food which already had limited sustained acceptability. The learning was not found when the aversive stimulus followed a meal on a fully acceptable food.     

Investigating Fear in Rainbow Trout (Oncorhynchus mykiss) Using the Conditioned-Suppression Paradigm

Trout learned the operant task of pendulum-pressing for a food-reward in a mean of 4.3 sessions lasting 1 hr. In a separate phase, fish also learned—through classical conditioning—to associate a neutral light cue with an aversive stimulus. When again allowed to pendulum-press for food, after aversive classical conditioning, there was a drop in the rate of responding. The mean rate dropped from 3.6–2.9 responses per min. Most important, when the light-stimulus was superimposed on a steady bout of pendulum-pressing, trout ceased to press the pendulum and did not resume activity until termination of the light-stimulus (mean number of responses during a 3-min interval immediately prior to light-stimulus = 14.3 vs. during 3-min light-stimulus = 0.1). Psychologists have used this decrease in operant responding, or “conditioned emotional response,” as a tool to examine the psychological nature of this type of aversive conditioning. In this study, the fish demonstrated various results under this paradigm similar to those shown by “higher” nonhuman animals, therefore challenging the view of fish as unconscious, nonsentient animals.     

The propensity for consuming ethanol in Drosophila requires rutabaga adenylyl cyclase expression within mushroom body neurons

Alcohol activates reward systems through an unknown mechanism, in some cases leading to alcohol abuse and dependence. Herein, we utilized a two-choice Capillary Feeder assay to address the neural and molecular basis for ethanol self-administration in Drosophila melanogaster. Wild-type Drosophila shows a significant preference for food containing between 5% and 15% ethanol. Preferred ethanol self-administration does not appear to be due to caloric advantage, nor due to perceptual biases, suggesting a hedonic bias for ethanol exists in Drosophila. Interestingly, rutabaga adenylyl cyclase expression within intrinsic mushroom body neurons is necessary for robust ethanol self-administration. The expression of rutabaga in mushroom bodies is also required for both appetitive and aversive olfactory associative memories, suggesting that reinforced behavior has an important role in the ethanol self-administration in Drosophila. However, rutabaga expression is required more broadly within the mushroom bodies for the preference for ethanol-containing food than for olfactory memories reinforced by sugar reward. Together these data implicate cAMP signaling and behavioral reinforcement for preferred ethanol self-administration in D. melanogaster.     

Influence of handling and conditioning protocol on learning and memory of Microplitis croceipes

Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) learns odors in association with both hosts and food. The food‐associated ‘seeking’ behavior of M. croceipes was investigated under various training protocols utilizing the conditioning odor, 3‐octanone. We investigated the effects of odor training, or its lack, training duration, training frequency, time elapsed after training, wasp hunger state, and training reinforcement, on the food‐seeking responses of M. croceipes females. We found that odor‐trained females show strong food seeking responses, whereas non‐odor‐trained females do not respond to the odor, and that a single 10 s association with the odor whilst feeding on sugar water subsequently conditioned the wasps to exhibiting significant responses to it. Increases in training time to more than 10 s did not improve their responses. Repetition of the food–odor associations increased a wasp's recall, as well as its response over time, compared to a single exposure. Repeated exposure to the learned odor in the absence of a food reward decreased the responses of less hungry individuals. However, the level of response increased significantly following a single reinforcement with the food–odor association. Understanding the factors that influence learning in parasitoids can enhance our ability to predict their foraging behavior, and opens up avenues for the development of effective biological detectors.