Showing papers in "Psychobiology in 1981"

Taming of wild Rattus norvegicus by lesions of the mesencephalic central gray

Abstract: Wild-trapped Rattus norvegicus show a consistent pattern of fear and defensive behavior to nonpainful stimuli such as an approaching experimenter, an anesthetized conspecific, or tactile stimulation of the back and vibrassae, as well as to painful stimuli. This reactivity to a range of stimuli, and the different behaviors by which such fear or defensiveness may be expressed, including flight, freezing, vocalization, the jump-attack, and specific biting patterns, make wild rats very appropriate subjects for the analysis of brain mechanisms underlying fear. Lesions of the mesencephalic central gray dramatically lowered these defensive reactions to both painful and nonpainful threat stimuli, reducing or eliminating each of the defensive reactions measured. The subjects showed no evidence of significant motor impairment or disturbance of primary sensory mechanisms. Because these experimental lesions involved considerable damage to the superior colliculi, a second study used wild rats with damage only to the colliculi. These animals displayed some deficits in visually guided behavior and in reactivity to certain tactile stimuli, but most of their fear reactions were intact. These findings suggest that the mesencephalic central gray, traditionally regarded as involved in reactivity to pain, may be one component of a mechanism underlying fear and defensive behaviors to nonpainful as well as noxious stimuli.

Effects of ipsilateral rostral pontine reticular lesions on retention of classically conditioned nictitating membrane and eyelid responses

Abstract: Neural unit recordings from the pontine reticular formation in well-trained rabbits show a tone-evoked onset response (CS), a suggestion of an airpuff onset response (UCS), and an increase in unit activity that is similar to the topography of the learned response. When this same area is destroyed by unilateral electrolytic lesions (in another group of animals), retention of the learned response is abolished but the reflex response is essentially unchanged. Since a recent study (McCormick, Lavond, Clark, Kettner, Rising, & Thompson, 1981) has shown that unilateral cerebellar lesions also produce a complete and selective abolition of the CR, and the CR cannot be reinstated with retraining, these findings are discussed in terms of a common circuitry that encodes the engram for short-delay classical conditioning of striated muscle responses.

The photoreceptor sensory code for perceived duration during visual masking

Abstract: In a study of the perceived duration of visually displayed letters that were either unmasked or masked by visual noise or homogeneous flashes, Haber and Standing (1970) found that the stimulus onset asynchrony limited the perceived duration of noise-masked letters presented in light adaptation but not of letters masked with homogeneous flashes in dark adaptation. Letters presented alone, as single flashes, exhibited adaptation-dependent visual persistence. The present psychobiological study replicated the stimulus conditions used by Haber and Standing while microelectrode recordings of sensory signals were taken from single Limulus photoreceptors. The data indicate that the sensory code for perceived duration at the photoreceptor level is the time that the sensory signal is above a criterion potential. When adaptation is taken into account, this photoreceptor code replicates the complex functional relations found in the behavioral studies of Haber and Standing. The data suggest that neural integration causes an aftercoming mask to interrupt the sensory signal itself, not its processing, although processing may end when there is no signal left to be processed.

Behavioral assessment of sodium arsanilate induced vestibular dysfunction in rats

Abstract: Vestibular dysfunction was induced in Long-Evans and Wistar rats—previously thought to be refractory to the effects of ototoxic drugs—by subcutaneous or intratympanic injections of sodium arsanilate (atoxyl). Three measures of swimming behavior were taken to assess the degree of vestibular dysfunction. These measures were: escape latencies, errors, and underwater swimming times. Subcutaneous injections of sodium arsanilate that resulted in no behavioral impairment of previously trained rats resulted in less efficient learning of the maze by naive rats. Visual compensation for vestibular impairment was detected by altering or removing the visual cues the rats used in their compensation. A strain difference in sensitivity to subcutaneous injections of sodium arsanilate was found between the Wistar and Long-Evans rats, with the Wistar rats being much more sensitive.

The relationship between plasma corticosterone levels and leverpress avoidance vs. escape behaviors in rats

Abstract: Groups of rats were exposed to training procedures that produce leverpress avoidance (Experiment 1) or escape (Experiment 2) behaviors. Plasma samples were obtained by decapitation after 30 sessions, and corticosterone concentrations were determined and compared with those of corresponding yoked and nonshocked (time-in-box) groups. The mean corticosterone level of the “avoiders” was lower than that of their yoked mates and not different from that of their non-shocked mates. This indicated a reduction in their arousal level with mastery of the avoidance response, which could not be accounted for by the reduction in numbers of shocks received. The mean corticosterone level of the “escapers” was as high as that of their yoked mates, and both levels were higher than that of the nonshocked group.

Reciprocal hemispheric influences on response habituation in the electrodermal system

Abstract: In three investigations, the rate of habituation of phasic electrodermal responses to auditory stimuli and the number of nonspecific responses were correlated with lateral differences in response amplitude. Fast habituation and less frequent responses were associated with higher left- than right-hand response amplitudes, whereas slow habituation and more frequent responding were associated with higher response amplitudes on the right hand. The results indicated a coincidence between the degree of phasic electrodermal activity and reciprocal hemispheric influences, implying hemispheric interactions in mechanisms that control phasic reactivity, habituation, and attention.

A match-mismatch theory of limbic system function

Abstract: The contributions of three key limbic system structures—the amygdala, the hippocampus, and the septum—to human and animal behavior are analyzed, focusing primarily on learning and motivational variables. The amygdala is assumed to be part of a stimulus-analyzing system involved in the processing of reinforcers and salient cues. This system contributes to the formation of conditioned reinforcers and, thus, to the ability of arbitrary cues to control species specific behavior. The hippocampus is assumed to be part of a different stimulus-analyzing system which processes nonsalient stimuli. It habituates all stimuli not associated with reinforcement, this process occurring on any nonreinforced presentation. However, those non-salient stimuli followed by reinforcement are registered as secondary cues. These cues are devoid of conditioned reinforcing properties. The septum is viewed as a coordinating structure that handles the flow of information between these two systems. The principles of operation of these structures are based on neurological and behavioral data from both animals and humans.

Naloxone can alter experimental pain and mood in humans

Abstract: The present experiment investigated the possibility that endogenous opioids attenuate aversive experience in humans. Two experimental pain procedures—cold pressor pain, and ischemic pain produced by the submaximal effort tourniquet technique—were administered on each of 2 consecutive experimental days. Seven subjects received double-blind infusions of the opiate antagonist naloxone on Day 1 and saline on Day 2; for seven other subjects, the order was reversed. Based on earlier studies of exogenous opiate analgesics, the present experiment was designed to maximize subject anxiety and the “disturbingness” of the ischemic pain. Under these conditions, opiate receptor blockade significantly affected ratings and tolerance times for ischemic pain, anxiety, and mood. These results contrast with those of recent studies in which naloxone effects on experimental pain in humans were subtle or indiscernible, and suggest that psychological factors will have to be controlled and studied in the investigation of physiological bases of pain and other psychological states.

An investigation of intravenous ethanol self-administration in rats using a fixed ratio schedule of reinforcement

Abstract: Six rats were trained to press one (food) bar under a 30-sec variable interval (VI) schedule for food pellets. Once responding had stabilized, a second (drug) bar was introduced and responding on it produced intravenous infusions of ethanol according to a fixed ratio (FR) schedule of reinforcement. Across a range of ethanol doses (1-180 mg/kg), increasing the FR requirement yielded an unsystematic picture of increases, decreases, and no change in response output on the drug bar. When, in two of these animals, cocaine hydrochloride (.5-1.5 mg/ kg) was tested subsequent to the ethanol, any increase in FR requirement was usually accompanied by some increase in response output. These findings suggest that the intravenous administration of ethanol is a relatively weak positive reinforcer in that it does not support self-administration behavior under conditions which otherwise do support the intravenous self-administration of cocaine.

Inhibition of intraspecific aggression in male hamsters by septal stimulation

Abstract: Male hamsters selected for intraspecific aggressiveness were implanted with a movable monopolar electrode that was lowered through the septal region. At current levels which did not produce any motor automatisms or stereotyped competing responses, septal region stimulation prevented the initiation of subjects’ attacks on muzzled and analgesic-treated target hamsters. Thresholds for this aggression inhibition appeared to reach a minimum in the mid-and ventral septum. Stimulation at current levels necessary for aggression inhibition had no effect on sunflower seed acceptance. In operant tests, the reinforcing value of the aggression- inhibitory stimulation appeared to be positive at low current levels and negative at high levels.

Electrophysiological and behavioral correlates of arousal

Abstract: The relationships among levels of activity, responsiveness, exploration, and cortical arousal were assessed in a group of similarly reared male rats from a strain that was highly inbred to maximize genetic homogeneity. In Experiment 1, 22 subjects were tested in a complex, compartmentalized open field (i.e., a closed field), and those falling approximately 1 SD above or below the group activity mean (eight were eliminated) were designated as high- or low-active, implanted with electrodes, and tested electrophysiologically to ascertain the level of cortical arousal as determined via measurements of visually evoked potential afterdischarge amplitude. High-active subjects demonstrated a significantly lower afterdischarge amplitude, indicating that behavioral arousal may be indexed by a readily quantifiable electrophysiological measure. A second group of 14 rats (Experiment 2) was tested and retested after 45 days in the closed field, estabhshing that high- or low-behavioral responsiveness is a stable characteristic. Subjects then received 2 days’ exposure to one of two dissimilar compartments of an exploratory apparatus and were tested to determine amount of time spent in the familiar vs. novel compartments. High-active rats were found to demonstrate significantly shorter initial response latencies. However, no other differences were found. These rats were next tested in a completely open field. No significant activity differences were discovered. These findings show that a high level of arousal as a response to a highly complex environment or intense stimulation is not related to generalized activity elicited in a low-complexity environment (e.g., the open field). These findings also indicate that similarly reared rats may be differently influenced by novel, complex, or intense stimuli, such that some subjects become highly responsive and cortically aroused, whereas others respond with low levels of behavioral and cortical activation. The findings are discussed in terms of cortical and subcortical mechanisms mediating arousal.

Exploratory behavior of rats following visual cortical and subcortical lesions

Abstract: Exploratory behaviors of rats with lesions of the visual cortex or superior colliculus (SC) were examined using a traditional open field and a smaller closed field. Animals with large bilateral lesions of the SC or lesions restricted to the deep laminae of the SC exhibited excessive locomotor activity in both experimental situations. The degree of habituation of this hyperactivity and other behaviors such as investigating rearing, exploratory nose poking, and self-initiated exposure to illuminated visual stimuli in the closed field were also examined. Consideration of the complete range of exploratory responses and the effect of lesions on them lead to a proposal that the hyperactivity of rats with SC lesions is an impairment adjunct to sensory neglect and orienting behavior impairments.

Is the striatum involved in passive-avoidance behavior? A commentary

Abstract: The role of the striatum in passive avoidance (PA) behavior has been reviewed in light of recent data by Olmstead and Villablanca (1980) reporting a lack of involvement of the caudate nucleus in this behavior. Evaluation of their data revealed that a small deficit in PA was demonstrated in the caudotomized adult cat group. Similarly, our own data with kainic-acid-induced striatal lesions in rats resulted in impairments in passive-avoidance acquisition and retention. It is concluded that the striatum is involved in PA behavior, although the underlying behavioral processes that contribute to this role are not clearly understood.

N-2-chloroethyl-N-ethyl-2-bromobenzylamine hydrochloride (DSP4), a new selective noradrenaline neurotoxin, and taste neophobia in the rat

Abstract: Rats were systemically injected with N-2-cMoroethyl-N-ethyl-2-bromobenzylamine (DSP4), a selective noradrenaline neurotoxin, and their initial, neophobic response to a novel saccharin solution was measured No significant alteration of the neophobic response was noted unless the novel saccharin was presented within a novel drinking bottle; then the DSP4- treated rats showed a significantly attenuated neophobia, as measured by drinking suppression ratios The discrepancy between the present findings, which range from no alteration to an attenuated neophobia, and the enhanced neophobia result of a previous investigation that used 6-hydroxydopamine is explained on the basis of the different methods employed for depleting brain noradrenaline

Fractionation of respiratory and vascular responses with simple visual stimulation

Abstract: The unitary nature of Sokolov’s orienting response (OR) has been interpreted as requiring the covariation of a range of physiological indicators in response to stimulus variation. In contrast, Barry (1978) proposed a four-way fractionation of these indicators as a more realistic description of stimulus-response relationships in the OR domain. The first experiment tested aspects of this fractionation with simple visual stimulation and confirmed the existence of the three independent processes predicted for situations not requiring a motor response. Parallels between two of these processes and those of Groves and Thompson’s (1970) dual-process theory of habituation were noted, and then explored in the following two experiments. Results confirmed the fractionation obtained in the first experiment and indicated that dual-process theory can handle various aspects of response fractionation that cannot be accommodated by Sokolov’s OR theory.

Effects of prior environmental enrichment and amygdaloid lesions on consumatory behavior, activity, predation, and shuttlebox avoidance in male and female rats

Abstract: Male and female rats were exposed to environmental enrichment or impoverishment for 55-64 days after weaning. Medial amygdaloid lesions or control operations were then followed by consumatory, activity, predation, and shuttle-avoidance tests. Amygdaloid lesions reduced daily water consumption and prandial drinking, increased novel foods consumption and activity, impaired predatory behavior, and facilitated avoidance acquisition. Female rats showed increased rejection of quinine solution, more activity, more rapid predation, and superior avoidance when compared with males. Prior environmental enrichment decreased entrance latency into an open field, increased activity, and facilitated both predation and avoidance acquisition. The sex of the subjects interacted with lesion effects in both open-field and predation tests, while both sex and enrichment interacted with lesion effects on avoidance. Sex and enrichment interacted in open-field and avoidance tests. It is suggested that both sex and enrichment modify the behavioral effects of amygdaloid lesions by contributing in different ways to levels of generalized arousal.

Averaged cortical potentials (lambda responses) time-locked to onset and offset of saccades

Abstract: The purpose of the experiment was to examine the assumption that the lambda response would be associated with offset of the saccade. The occipital EEG and eye movements were recorded under the condition in which the subjects looked at the stimulus object freely. EEGs triggered at onset and offset of saccades were averaged separately by a computer. Lambda responses appeared to be more definite and were larger in amplitude in onset averages than in offset averages. The result showed that the lambda response was associated with offset of the saccade, and not with its onset. It is suggested that the lambda response might be a kind of visual evoked potential elicited by the afferent inflow beginning at fixation pause.

Conditioned taste aversion and unconditioned suppression of water intake induced by phenylpropanolamine in rats

Abstract: The putative aversive properties of phenylpropanolamine (PPA), an analog of amphetamine, were delineated in two behavioral tests. In a conditioned taste aversion paradigm, PPA (10, 20, or 40 mg/kg) was found to induce dose-dependent taste aversion, whereas identical dosages of PPA were found to produce dose-dependent unconditioned suppression of water intake in 23.5-h water-deprived rats. Comparison of the dose-response curves for the aversion and hypodipsia induced by PPA indicates that a single process, presumably malaise or toxicosis, may mediate these effects. These findings question the notion that PPA induces anorexia via activation of a CNS satiety mechanism and lend credence to the suggestion advanced herein that nonspecific malaise may mediate the moderate anorectic activity of PPA observed in rodents and humans.

Mitral cell responses to the odors of reward and nonreward

Abstract: The purpose of this investigation was to determine if there were specific odor components in the goalbox of a straight alleyway following reward and nonreward trials. Behavioral research has convincingly demonstrated that, unless the goalbox is cleaned between animals, a pattern of slow running on nonreward trials and fast running on reward trials soon develops. It has been proposed that the rat emits an odor in the goalbox following nonreward which allows following conspecifics to predict the upcoming goal event before reaching the goalbox. Behavioral research has been unable to determine if there are specific odors associated with reward and nonreward, or if there is only one odor of varying concentration, or if only one odor is present and the cue for the other condition is merely the absence of that odor. The results of this study strongly suggest that there are specific odors in the goalbox as a result of nonreward and reward. They further suggest that these “reward” and “nonreward” odors are different from the odors of food and urine, and that the “reward” and “nonreward” odors, although different, may possibly be similar in chemical structure.

Behavioral determinants of severe cardiac inhibition

Abstract: Behaviorally elicited cardiac arrests have been observed in different phyla independently of the neurogenicity or myogenicity of pacemakers. Startling stimuli such as visual detection of close and fast movement is especially associated with complete cardiac inhibition. In contrast, orienting responses are associated with bradycardia. Although studies on vertebrates are not usually concerned with reflex responses, it can be assumed that actual cardiac arrests occur in some cases in which bradycardia is reported, but that these arrests cannot be recorded because of the methodology used. Heart rate can be used to separate patterns displayed in such defensive reflex behaviors as orientation, startle, and freezing. Behavioral sequences can be categorized into various series of patterns which correspond to various sequential and multiphasic heart-rate patterns.

Medial hypothalamic stimulation decreases the phagocytic activity of the reticuloendothelial system

Abstract: Although research has linked the central nervous system with changes in immunoresponsivity, research on the possible role of the central nervous system in altering reticuloendothelial activity is lacking. This study investigated the possible relationship between hypothalamic structures and changes in responsivity of the reticuloendothelial system. Eight male albino rats received bilateral electrode implants in the ventromedial area of the hypothalamus, and, following brain stimulation, reticuloendothelial activity was assessed 3, 6, 12, 24, and 96 h after stimulation. Brain stimulation decreased phagocytic activity of the reticuloendothelial system. These findings may increase our understanding of a possible neural mechanism underlying relationships between stress and resistance to disease states.

Alcoholic hypoglycemia as a result of acute challenges of ethanol

Abstract: Alcohol-induced hypoglycemia was experimentally studied in male albino rats. Intraperitoneal injections of 30% ethanol resulted in a significant decrease in blood-sugar levels (relative to saline-injection control animals) in subjects that had fasted 48 and 72 h. Alcohol-induced hypoglycemia was not found in nonfasted animals.

Discriminative avoidance learning in hippocampal and cortical rats: Acquisition rate, behavioral strategies, and long-term retention

Abstract: Facilitation of visually discriminated avoidance learning was observed in rats 1 week after they were lesioned in the dorsal hippocampus. While perseveration of a spatial strategy acquired during a pretraining session occurs in sham-operated and cortically lesioned controls, no such perseveration was observed in hippocampals. Elimination of the presurgical shaping session reduced the number of spatial strategies in all groups, but differences in trials to criterion and percentage of place strategies remained. Retesting the animals 3 weeks after training showed that hippocampals and corticals had poorer retention than did shams. There were no differences in retention of groups tested 24 h after training. The long-term retention deficit seems to be independent of the fact that hippocampals learn faster, since cortically lesioned animals also showed the memory deficit, compared with controls, even though they had as many training trials. The results are taken as a demonstration of lesion-induced anterograde amnesia in the rat.

Effect of naloxone and housing conditions on shock-elicited reflexive fighting: Influence of immediate prior stress

Abstract: The effect of naloxone (4 mg/kg) on the defensive reaction of shock-elicited fighting was studied in male albino rats that were housed individually or in groups for 5 weeks. Naloxone consistently reduced the fighting reflex in both groups, but only when animals were exposed to the reflexive paradigm just prior to the naloxone injection and subsequently retested. Housing conditions also produced an effect on fighting independent of drug manipulation, in that individually housed animals exhibited decreased fighting compared with group-housed animals. Studies of pain sensitivity to shock in group-housed animals injected with naloxone exhibited a pattern similar to that of the fighting response. Naloxone increased pain sensitivity only when the animals were exposed to the shock just prior to drug administration and subsequently retested. Additional group-housed animals were tested with naloxone at lower shock intensities to examine the possibility of a positive linear relationship between pain sensitivity and shock-elicited reflexive fighting. Results did not support a positive relationship between pain sensitivity and fighting, but rather suggested that stress-related endorphin release will facilitate the fighting response. Data are discussed with respect to naloxone’s effect on locomotor activity and the association of that activity with adaptive behavior.

Motor debilitation, short- and long-term shuttlebox deficits, and brain monoamine changes following footshock pretreatment in rats

Abstract: Male hooded rat triplets, each consisting of an unshocked control (C), an animal that could escape from the shock by leverpressing (LE), and a yoked animal that received noncontingent shock (NC), were pretreated with either short-duration, high-intensity (Hi) or long- duration, low-intensity (Lo) footshock. Varying degrees of motor debilitation not offset by the escape contingency were apparent immediately following the Hi pretreatment. Only the rats showing motor debilitation had short-term deficits in FR-1 and FR-2 escape-avoidance performance that were related to lowered diencephalic norepinephrine (NE) levels. The Lo pretreatment, which utilized shocks ⩾5.0 sec in duration, had no significant long-term effects on escape-avoidance behavior under the conditions of this study. Only nondebilitated NC rats from the Hi pretreatment condition showed a reliable deficit in FR-2 shuttlebox performance at 72 h. This occurred in spite of the fact that their pretreatment shocks were shorter than 5.0 sec in duration and that they showed no signs of motor debilitation and essentially normal brain NE levels at 30 min.

Effects of vasopressin on open-field behavior in rats

Abstract: The aim of this experiment was to assess the effects of subcutaneous injections of lysine-vasopressin on the locomotor behavior of rats in an open-field situation. The results obtained showed greater peripheral locomotor activity in the placebo group during the first session, greater central area locomotor activity and a more evident gradual locomotor immobility with significant differences during the second and the fifth sessions in the experimental group. These results are discussed in terms of emotionality level, habituation, and physical and procedural characteristics of the experiment.

Effects of mixed training and overtraining on recoveries from amnesias in rats with visual cortical ablations

Abstract: This investigation was concerned with the question of whether amnesias for simple visual tasks which result from injuries to the visual cortex can be corrected via training on other visual tasks. Such effects were noted, but only when the problems shared a common mode of solution. It was also observed, in contradiction to a classical conclusion of Lashley, that extensive preoperative overtraining conveys some protection of postoperative performance of the black-white discrimination problem.

Age at infection as a determinant of the behavioral effects of herpes encephalitis in mice

Abstract: The influence of age at infection on the nature of the behavioral effects of herpes simplex type 1 encephalitis in mice was examined. Weanling and adult mice were initially immunized with a footpad (FP) inoculation of virus, followed 2 weeks later by an intracerebral (IC) inoculation. Subsequent open-field testing 2 weeks later revealed that weanling mice were hypoactive and showed a reduced proportion of center-field entries. In contrast, adult mice were hyperactive. No significant effects on Y-maze alternation or activity were observed. These results indicate that the qualitative nature of the effects of herpes encephalitis on behavior depends upon characteristics of the host.

Signal-centered action patterns in rats without neocortex in a Pavlovian conditioning situation

Abstract: After removal of neocortex, rats were found to press a lever more readily than were shamoperated controls when exposed to an autoshaping procedure in which either the movement of a lever (Experiment 1) or its illumination (Experiment 2) was paired with the delivery of food. In both experiments, the apparatus was provided with a second, but nonpredictive, lever. As in more traditional Pavlovian situations, the neodecorticates showed clearer-than- normal response differentiation between the two cues, as well as more complete reversal of responding when their predictiveness was altered. Despite abnormally strong acquisition of auto-shaped responding, the lesioned animals were able to suppress these responses under an omission schedule (Experiment 3). These data make it unlikely that the instrumental leverpress deficit seen in neodecorticated rats and rabbits in earlier studies is due in any simple way to sensory, motor, or motivational limitations in the lesioned animals and suggest a cause elsewhere in the learning paradigm itself.

Environment-dependent taste-aversion extinction: A question of stimulus novelty at conditioning

Abstract: In Experiment 1, four groups of rats were exposed to two saccharin(Sac)-lithium chloride(LiCl) pairings in a novel animal compartment. In subsequent daily extinction trials, Sac (two groups) or water (H2O) (two groups) was presented either in the same (as conditioning) or a different compartment. There was no evidence that the presence or absence of the conditioning compartment influenced the amounts of Sac or H2O drunk. Postextinction preference tests (Sac vs. H2O), performed in the conditioning compartment, showed a compartment-dependent extinction effect: There was a significantly stronger aversion in the group drinking Sac during extinction in a different (from conditioning) compartment than in the group drinking Sac in the conditioning compartment. In Experiment 2, four groups were given two Sac-LiCl trials in a novel (2 groups) or a familiar (2 groups) compartment. One “novel compartment” group and one “familiar” group were offered Sac during daily Sac-aversion extinction trials in the conditioning compartment, and the remaining groups drank Sac in a different compartment. Again, intercompartment generalization of the Sac aversion was demonstrated: There was no evidence that the particular compartment present influenced the strength of aversion during extinction. Postextinction preference tests showed the previously observed compartment-dependent extinction effect only in the case of the “novel compartment” groups. Thus, in view of previously reported data, the number of conditioning trials and the novelty of the conditioning compartment were shown to be critical to compartment-dependent taste-aversion extinction.