Motivational and neuroanatomical specificity of hypodipsia for aversive solutions produced by medial preoptic injury to the rat.

Bilateral medial preoptic lesions in rats dramatically lowered the rejection threshold for quinine-adulterated water but not for food in 24-hr forced-choice tests. The detection threshold for quinine in a two-bottle choice test, however, was unaffected by the medial preoptic lesion. Bilateral septal and lateral preoptic lesions had no effect on any quinine-adulteration tests. The enhanced rejection of quinine-adulterated water in a forced-choice test by medial-preoptic-damaged rats was also observed after 24-hr of water deprivation. Furthermore, the plasma osmolality of medial preoptic rats was significantly elevated above controls after 24-hr of water deprivation. These findings were interpreted as suggesting that a medial preoptic lesion produces a deficit in thirst-motivated behavior.     

Excitotoxic lesions of the parafascicular nucleus produce deficits in a socially transmitted food preference

The parafascicular (PF) nucleus, a posterior component of the intralaminar nuclei of the thalamus, is considered to be an essential structure in the feedback circuits of basal ganglia-thalamo-cortical systems that critically participate in cognitive processes. To study the PF contribution to processing of behaviorally significant information during specific episodes of learning, we investigated the effects of damaging the PF nucleus in the acquisition of a natural form of social olfactory learning, the socially transmitted food preference (STFP) task. This task is a non-spatial paradigm that exhibits some of the characteristics of relational memory because it requires that animals use information obtained in one episode to guide later behavior in different circumstances. Adult male Wistar rats were submitted to pretraining bilateral N-methyl-D-aspartate (0.15 M, pH 7.4) lesions of the PF (0.4 microl/side, 0.2 microl/min). The behavioral effects of PF lesions were compared to vehicle- and sham-operated control groups and two retention delays were considered in separate groups: immediately (Lesion-I, Vehicle-I, and Sham-I groups) and 24h after training (Lesion-24, Vehicle-24, and Sham-24 groups). PF lesions produced delay-independent impairments in the STFP suggesting that this nucleus might modulate the acquisition of this odor-odor association task. Results are discussed in the context of medial prefrontal cortex deafferentation induced by PF damage.     

Effects of lesions of the amygdala, preoptic area, and hypothalamus on estradiol-induced activity in the female rat.

Lesions of the anterior hypothalamic nucleus and the medial preoptic area sharply attenuated enhancement of wheel running by estradiol benzoate in ovariectomized female rats. Lesions of the corticomedial amygdala had no effect on this behavior. The hormonal effects on activity were largely independent of any changes in body weight. Results of this first experiment indicated that the anterior hypothalamic and medial preoptic areas are critically involved in the induction of activity by estradiol. However, this experiment provided no support for suggestions that the corticomedial amygdala inhibits those structures that mediate the estrogenic induction of activity. In the second experiment, food deprivation was used to stimulate activity. Results of this experiment suggested that the reduction in the ability of estradiol to induce activity following anterior hypothalamic and medial preoptic lesions does not reflect a general inability to become more active.     

Some observations on the perception of Marroquin patterns.

Demonstrations are presented to show that the perception of structure in Marroquin patterns is disrupted if the dots comprising the pattern have opposite contrast polarity, and also if the dots comprising the pattern are separated in stereoscopic depth. It is also demonstrated that the perception of structure in a Marroquin pattern is made possible if the pattern is separated in stereoscopic depth from 'noise' dots, where the pattern structure cannot be perceived in either half of the unfused stereogram. In these respects the perception of Marroquin patterns is similar to the perception of Glass patterns. These findings are thus consistent with the proposal that the perception both of Marroquin and of Glass patterns is based on the construction of virtual lines.     

Medial preoptic area and onset of maternal behavior in the rat.

The present series of experiments examined whether the medial preoptic area (MPOA) is involved in the onset of maternal behavior in the rat. Previously, the MPOA had been shown to be important in the maintenance of maternal behavior in the lactating rat. The first experiment investigated whether estradiol benzoate (EB) acts on the MPOA to facilitate the onset of maternal behavior in the 16-day pregnant, hysterectomized, and ovariectomized female rat. Such rats when given EB implants in the MPOA had significantly shorter latencies for the onset of maternal behavior than had females implanted with cholesterol in the MPOA or with EB in the ventromedial hypothalamus, in mammillary bodies, or under the skin. A second experiment showed that estrogen-induced prolactin release was not involved in this facilitation. A third experiment indicated that MPOA lesions disrupt the onset of maternal behavior that is induced by pup stimulation in virgin females. It was concluded that the MPOA is involved not only in the maintenance of maternal behavior but in the hormonally mediated onset of maternal behavior and the onset of maternal behavior induced in virgin females by pup stimulation.     

Drinking by rats after lateral hypothalamic lesions: a new look at the lateral hypothalamic syndrome.

Rats that have recovered from aphagia and adipsia following lateral hypothalamic lesions are believed to be incapable of experiencing thirst and to drink water simply to facilitate the consumption of dry food. However, the present results indicate that these animals will drink in response to dehydration of the intracellular or intravascular fluid compartments and to hyperangiotensinemia, if testing continues beyond a few hours. Comparable effects also were obtained in rats with mesencephalic brain damage, which appeared to destroy portions of the substantia nigra and the ascending nigrostriatal dopaminergic projections. These findings, when placed in the context of a recent neurochemical model for recovery of function, provide the basis for a new interpretation of the lateral hypothalamic syndrome.     

The involvement of the hypothalamic preoptic area on the regulation of thirst in the rat.

Acute reversible lesion in the medial preoptic area (MPOA) by unilateral injection of the local anesthetic lidocaine chlorhydrate (1 microliter, 20 ng/microliters) causes a transient increase in water intake induced by water deprivation in rats. Since lidocaine suppresses the nervous activity, leaving intact fibers of passage and blood vessels, the results suggest an intrinsic inhibitory action of the MPOA on the regulation of water intake. Drinking elicited a return to volumes similar to those of control rats, 3-4 h after lidocaine administration. Lidocaine released into the lateral preoptic area (LPO) slightly decreased or did not change water intake, as compared with controls. The urinary excretion in the MPO group was higher than that of the controls and the LPO, while this last group excreted significantly less urine. The ablation of the POA with lidocaine suggests that the medial aspect of the POA has an intrinsic inhibitory factor influencing drinking, while the lateral aspect did not show a relevant effect.