Aggressive behavior of pigeons: Suppression by archistriatal lesions

The agonistic responses of pigeons to the introduction of a stick and the experimenter's hand into their home cages is described. The effects of lesions of the archistriatum, a presumed homologue of the mammalian amygdala, of lesions of the overlying neostriatum and of control sham operations on this behavior in selected aggressive pigeons are reported. Only archistriatal lesions lead to a persistent depression of the aggressive and a converse increment of the avoidance components of the pigeon's response to both test stimuli. The results are discussed in relation to other evidence on the role of the avian archistriatum and this structure's correspondence with the amygdala.     

Generalization of free-operant avoidance behavior in pigeons

Three groups of four pigeons, trained to press a treadle on a free-operant avoidance schedule, were given auditory discrimination training. Alternating 2-min components of avoidance and no shock were paired with either a tone or white noise. The pigeons were subsequently given two types of generalization tests, with and without avoidable shocks scheduled. Two of the groups, trained interdimensionally, produced excitatory and inhibitory generalization gradients along the tone frequency dimension. A predicted post-discrimination gradient was computed from the algebraic summation of these gradients of excitation and inhibition. The predicted gradient was compared with the actual post-discrimination gradient obtained from the third group of pigeons that had been given intradimensional discrimination training on the tone frequency dimension. The predicted postdiscrimination gradient agreed in shape with the empirical postdiscrimination gradient. The results in general support Spence's (1937) gradient interaction theory.     

Discriminated time-out avoidance in pigeons

Performances of two pigeons were studied on a concurrent discriminated TO avoidance-VR schedule. Each avoidance response postponed a TO from a VR 140 for a specified RS interval. The warning stimulus on the TO avoidance schedule was a discontinuous clock which consisted of a series of discrete color changes that varied systematically with the RS interval. Experimental manipulations established that the avoidance behavior was under the control of the avoidance schedule and the discontinuous clock. Five-min TOs maintained higher avoidance rates than shorter TO durations; a 15-min TO maintained less avoidance responding than the 5-min TO. Chlorpromazine hydrochloride increased TO avoidance behavior and decreased concurrent VR behavior.     

Active and passive avoidance performances following bilateral olfactory bulbectomy

Three experiments were performed to study the effects of bilateral olfactory bulbectomy upon active and passive avoidance conditioning. In the first experiment, olfactory bulbectomized rats were found not to be impaired on a one-way active avoidance task but showed a fear retention deficit. In Experiment 2, sham-operated rats demonstrated a degree of fear retention that was a positive linear function of the number of shock presentations; olfactory bulbectomized rats showed a total absence of fear retention. In the third experiment olfactory bulbectomized rats failed to demonstrate the inverse relationship between shock intensity and two-way avoidance performance normally evidenced. The pattern of data obtained suggests that while bulbectomized rats do not show any general avoidance impairment they do seem to be unaffected by the suppressive effects of shock upon ongoing behavior.     

Open-field and avoidance behavior after neostriatal lesions in male and female rats.

The behavioral effects of lesions of the anterodorsal or posteroventral parts of the caudate-putamen were studied in adult male and femle rats that were gonadectomized or left untreated prior to brain surgery. Anterodorsal (ADC) lesions consistently impaired acquistion of one-way avoidance behavior and tended to interfere with the development of a two-way avoidance response; comparable effects were observed in gonadectomized and intact animals of both sexes. By contrast, ADC lesions increased activity in the open field only in intact females and increased rearing only in ovariectomized females. Posteroventral caudate (PVC) lesions caused transient aphagia and adipsia in both sexes but did not consistently affect open-field activity or the acquistion of one-way avoidance responses by either sex. These lesions profoundly impaired acquistion of shuttle box avoidance responses by intact males. By contrast, castrated males and intact and ovariectomized females with PVC lesions avoided normally in the shuttle box. The present results suggest that localization of behavioral functions within the striatum differs with the sex of the subject, in part because of activational effects of gonadal hormones.     

Role of pituitary-adrenocortical system in mediating avoidance behavior of rats with septal lesions.

Three experiments examined the hypothesis that the effects of septal lesions and systemic injections of scopolamine on avoidance acquisition could be attributed to the effects of either of these treatments on adrenocorticotropic hormone (ACTH) secretion. Septal lesions and scopolamine facilitated 2-way conditioned avoidance response acquisition, and the lesions retarded passive avoidance acquisition. However, neither the injections of dexamethasone, a synthetic glucocorticoid which inhibited ACTH secretion as did septal lesions, nor injections of ACTH which mimicked the facilitatory effects of scopolamine on basal ACTH secretion, affected avoidance in these paradigms. Thus, the main hypothesis was not supported. The finding that scopolamine did not affect passive avoidance indicates that a cholinergic system may not be involved in mediating the suppressive effects of punishment.     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

Cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels in male hooded rats produced a mild, transient hypodipsia and lowered jump thresholds to footshock. The lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hr of water deprivation. Intraperitoneal injections of DL-5-hydroxytryptophan (75 mg/kg), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control subjects. Lesions of the MFB also resulted in deficient acquisition in a one-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a one-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the first passive avoidance task. The results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB.     

Probabilistically reinforced choice behavior in pigeons

A single principle, "momentary maximizing", may account for much of a pigeon's steady-state behavior in both probability learning and concurrent variable interval experiments. The principle states that a pigeon tends to choose the alternative that momentarily has the higher probability of reinforcement. A successive discrimination procedure, which produced matching in an earlier experiment, produced here a tendency to maximize if training were adequately extended. Maximizing was produced also by other procedures, in which no reinforcing event was presented on some trials: one procedure did and two did not provide a bird with information about the availability of reinforcement on a key after an unreinforced response on the other key. The latter two procedures were analogous to concurrent variable interval schedules in two respects: the reinforcement probability on one key increased while a bird responded on the other key; and they produced matching. But sequential statistics suggested that matching resulted from momentary maximizing. Depending on the procedure, the tendency to maximize produced different relative frequencies of pecking a key for a fixed relative frequency of reinforcement. Computer simulation of maximizing behavior in several concurrent variable interval schedules produced matching and sequential statistics similar to those produced by a real bird.     

Concurrent avoidance of shocks by pigeons pecking a key

Three pigeons were studied on concurrent, unsignaled, avoidance schedules in a two-key procedure. Shock-shock intervals were two seconds in both schedules. The response-shock interval on one key was always 22 seconds, while the response-shock interval associated with the other key was varied from 7 to 52 seconds in different experimental conditions. Response rates on the key associated with the varied schedule tended to decrease when the response-shock interval length was increased. Responding on the key associated with the constant schedule was not systematically affected.     

Nondiscriminated avoidance of shock by pigeons pecking a key

Four pigeons were trained to avoid shock by pecking a key on a free-operant avoidance schedule in which no exteroceptive stimulus signalled impending shock. Response rate was an inverse function of response-shock interval when shock-shock interval was held constant at 2 sec and response-shock intervals varied from 5 to 40 sec. Amphetamine increased response rates in two subjects and reserpine markedly reduced responding in one.     

Suboptimal choice behavior by pigeons

Contrary to the law of effect and optimal foraging theory, pigeons show suboptimal choice behavior by choosing an alternative that provides 20% reinforcement over another that provides 50% reinforcement. They choose the 20% reinforcement alternative—in which 20% of the time, that choice results in a stimulus that always predicts reinforcement, and 80% of the time, it results in another stimulus that predicts its absence—rather than the 50% reinforcement alternative, which results in one of two stimuli, each of which predicts reinforcement 50% of the time. This choice behavior may be related to suboptimal human monetary gambling behavior, because in both cases, the organism overemphasizes the infrequent occurrence of the winning event and underemphasizes the more frequent occurrence of the losing event.     

Active avoidance performance in genetically defined mice

It has been concluded by several investigators that active avoidance performance in mice is primarily influenced or even determined by a single gene. The genetically defined strains C57BL/6 and BALB/c have provided evidence that an aberrant development of pyramidal cells and mossy fiber configuration in the hippocampus of BALB/c mice also is determined by a single gene. As a test of the generality of the single gene influence on avoidance learning, and to examine the relationship of the hippocampal defect to avoidance learning, adult male mice of the inbred progenitor strains C57BL/6ByJ and BALB/cByJ and their seven recombinant inbred strains were tested in a variant of the shuttle-box paradigm used in previous studies. BALB/c were found to acquire the avoidance response at a faster rate than C57BL/6, consistent with most earlier reports, but performances of the recombinant inbred strains failed to dichotomize about the progenitor strains. The rank order of performance scores for the recombinant inbred strains was different from that reported in previous studies. Thus the present data failed to support the interpretation of a single major gene influencing active avoidance learning. It is concluded that avoidance learning and performance cannot be considered as unitary variables and that the interaction of genetic with environmental factors, including the conditions of the specific testing situation, are important considerations in any interpretation of genetic effects. No relationship between the hippocampal lamination defect and avoidance performance was demonstrated.