Looking at a predator with the left or right eye: Asymmetry of response in lizards

Studies carried out with the common wall lizard (Podarcis muralis) revealed preferential use of the left eye during responses to predatory threat in laboratory settings and in the wild. Here we tested lizards under monocular conditions of vision, using temporary eye-patching. Lizards were facing a (simulated) predatory threat laterally, from the side of the non-patched eye. Results showed that lizards with the left eye uncovered during predatory threat used the left eye to monitor the predator, whereas lizards with the right eye uncovered nonetheless tried to use the covered left eye. Moreover, lizards frequently tried to change the eye exposition, making a body C-bend behaviour. Right-eyed lizards showed more frequent and faster C-bending responses than left-eyed lizards, trying to monitor the predator with the left eye even though it was patched. Results fit with asymmetries in spontaneous eye use observed in laboratory conditions and in the wild in this species, confirming that structures located on the right side of the brain (mainly served by the left eye) predominantly attend to predatory threat.     

An application of escape theory to binge eating

The application of Escape Theory (Heatherton & Baumeister, 1991 ) to binge eating was studied in a non‐clinical sample of 129 women. Structural equation modelling (SEM) showed a good fit between the Escape Model and the data. Perfectionism strongly predicted aversive self‐awareness which, in turn, predicted negative affect. Negative affect predicted levels of avoidant coping which strongly predicted levels of binge eating. Implications for understanding and treating binge eating are considered. Copyright © 2006 John Wiley & Sons, Ltd and Eating Disorders Association.     

Unit activity alterations induced in the mesencephalic periaqueductal gray by local electrical stimulation

In the framework of a series of investigations concerning the neural substrate of aversion, electrophysiological methods were used in order (1) to specify, within the rat's periaqueductal gray (PAG), functional properties, viz. conduction velocity and refractory period, of PAG neurons already assessed in previous studies by means of behavioral methods, and (2) to gather data on their local synaptic relationships. Unit activities were recorded from the periaqueductal gray with the aim of analyzing those alterations that would be induced by locally applying an electrical stimulation with parameters shown to elicit escape behavior. An implanted row of electrodes allowed the application of a stimulation to several sites aligned along a mediolateral or a rostrocaudal axis through the periaqueductal gray. The results indicate that an electrical stimulation applied to the periaqueductal gray may induce its effects through the activation of a number of dendrites and many slow conducting fibers running in a great variety of directions and branching within the periaqueductal gray. Their refractory period was surprisingly low (0.6 ms) for slow conducting fibers (below 1 m/s). The local circuitry appears to include many inhibitory connections. Their organization is assumed to be partly recurrent. Stimulation-induced inhibition becomes predominant when the stimulation is moved away from the recorded neuron along the mediolateral axis, but not along the rostrocaudal axis.     

Take me away: The relationship between escape drinking and attentional bias for alcohol-related cues

Previous research has indicated that implicit attentional bias to alcohol-related cues may serve as a cognitive measure of susceptibility to alcohol dependence. The primary goal of the current study was to examine whether college students who drink to escape dysphoric emotions or moods (i.e., escape drinkers) have stronger attentional biases for alcohol-related cues than non-escape drinkers. Additionally, because previous research has shown that presentation time and content of smoking-related stimuli moderates differences between smokers' and nonsmokers' reaction times, this study sought to determine whether these effects generalized to alcohol-related stimuli. Participants who were identified as either escape (n = 74) or non-escape drinkers (n = 48) completed a dot-probe task in which alcohol-related pictures that contained humans interacting with the alcohol-related cues (active) or alcohol-related cues alone (inactive) were presented along with matched control pictures. These stimuli were presented for either 500 ms or 2000 ms to determine whether attentional biases occur as a function of initial or maintained attention to the alcohol-related cues. Escape drinkers displayed a significantly stronger attentional bias for alcohol-related inactive cues at longer presentation times (i.e., 2000 ms) compared to non-escape drinkers. This bias was independent of alcohol dependence and family history of alcoholism. These results suggest that in addition to dependence and family history, escape drinking is an important factor to consider when examining attentional biases to alcohol-related cues.     

Cortical nociceptive responses and behavioral correlates in the monkey

Experiments were performed to characterize cerebral cortical activity and pain behavior elicited by electrical stimulation of the tooth pulp in unanesthetized monkeys. Four monkeys were trained on two different operant paradigms: two on a simple escape task and two on an appetitive tolerance-escape task. All monkeys were implanted with bipolar stimulating electrodes in the right maxillary canine tooth and subdural recording electrodes over the left primary (SI) and/or secondary (SII) somatosensory cortices. Subdural tooth pulp-evoked potentials (TPEPs) recorded over the SII consisted of components P1 (27.5 ms), N1 (40.3 ms), P2 (84.0 ms), N2 (163.5 ms), P3 (295.3 ms), and N3 (468.0 ms). The long latency component (P3-N3) was found exclusively over the SII and was elicited by high intensity stimulation. The appearance of component P3-N3 required the recruitment of A delta nerve fibers into the maxillary nerve compound action potential and was correlated with high frequencies of escape. Administration of morphine sulfate (4 mg/kg, i.m.) caused a contemporaneous reduction in escape frequency and in the amplitude of P3-N3 recorded over the SII. The relationships between TPEP amplitude, escape behavior and A delta nerve fiber activity strongly suggest that the SII is involved with nociception and pain behavior.     

Intracerebroventricular interleukin-1 receptor antagonist blocks the enhancement of fear conditioning and interference with escape produced by inescapable shock

Brain interleukin-1 (IL-1) plays a key role in mediating the neural, endocrine, and behavioral consequences of injury and infection. Recent evidence indicates that brain IL-1 may also be important in producing endocrine and neurochemical responses to stressors. The present experiment sought to determine whether intracerebroventricular (i.c.v.) administration of an interleukin-1 receptor antagonist (IL-1ra) would block behavioral effects of a stressor. I.c.v. application of hrIL-1ra before inescapable shock blocked the subsequent interference with escape learning and enhancement of fear conditioning normally produced by this treatment.     

Influences of benzodiazepines on hypothalamically elicited emotional responses in the rabbit

Tranquilizers of the benzodiazepine group (oxazepam and diazepam) enhanced the rate of self-stimulation elicited from the lateral hypothalamus. Both tranquilizers induced reversal of escape and avoidance behaviors elicited from the medial hypothalamus to a high rate self-stimulation. The reversal effect persisted for two days and the initial negative emotional responses returned later as the drugs were depleted in the organisms. Thus the effect of minor tranquilizers substantially mimics the ventral hippocampus ablation effect which also produced the reversal of the medial hypothalamus responses in earlier experiments.     

Effects of water temperature and weight of wheel load on water wheel turning behavior of imipramine administered mice

This experiment investigated the effect of imipramine on water wheel turning behavior in relation to the water temperature and the wheel load. It was shown that the higher the water temperature, the more the mice rotated the wheel, and the greater the wheel load, the less mice rotated it. However, these factors did not reduce the effect of imipramine, which increased the number of responses. It was suggested that the water wheel test shows promise as a screening test for antidepressants.     

Effect of medial hypothalamic stimulation inducing both escape and approach on unit activity in rat mesencephalon

The activity of central gray (CG) neurons was previously shown to be affected by medial hypothalamic (MH) stimulation, and the discharge rate alterations were found to be often closely correlated with the vigor of the stimulation-induced escape responses. Since MH stimulation induces not only escape responses but also approach responses, this allowed a further investigation of the degree of specificity of the correlation between stimulation-induced neuronal activity and escape responses. Out of 129 CG units studied (in 39 rats), 26 clearly responded to the MH stimulation. When the stimulation parameters were varied, the mean discharge rate alterations of 9 units located in the dorsal part of the mesencephalic CG proved to be closely correlated exclusively with the alterations that affected the stimulation-induced escape responses. Furthermore, the variation of the most frequent interspike interval (modal ISI) proved to be closely correlated with the variation of the escape response in 3 instances in which the mean discharge rate showed no such correlation. In a few instances (2 units located much more ventrally, the spike rate alterations were closely correlated only with the alterations that affected the approach responses. It is suggested that neuronal activity in the dorsal part of the CG is rather specifically implicated in the generation of MH stimulation-induced aversive effects and escape responses.     

The effects of conditioned behaviour and environmental factors on plasma corticosteroid levels in pigs

Young pigs have been subjected to various conditioning procedures or environmental factors and the changes in plasma corticosteroid levels measured. Pigs in an escape avoidance situation soon learned to avoid most of the shocks. It was possible to demonstrate conditioned suppression of food reinforced operant behaviour. However, neither the escape avoidance conditioning nor the conditioned suppression technique resulted in large increases in plasma corticosteroids compared with those elicited by administration of ACTH. Exposure of pigs to cold, or chasing them, resulted in larger increases of plasma corticosteroids than the conditioning procedures. A marked 24 hr rhythm in plasma corticosteroid levels was demonstrated.