Habituating effects of nonhydrational oral stimulation on ingestive behaviors

The role of oral stimulation in the control of ingestive behavior was investigated using an airlicking procedure. It was hypothesized that the oral experience of airlicking would inhibit subsequent ingestive activity (water intake), possibly via an habituation process as suggested by recent research (Swithers, 1996). Rats were implanted with gastric cannulas and trained to lick at a stream of air. Experimental conditions con-sisted of combinations of airlicking and intragastric hydration followed by oral intake of water. In support of the main hypothesis, airlicking did reduce subsequent ingestive activity. While the role of habituation was not tested directly, the results lend support to the proposal that oral stimulation does control ingestion, and this control could act through an habituation process.     

An animal model of excessive eating: schedule-induced hyperphagia in food-satiated rats.

Nineteen rats were maintained throughout the experiment on ad libitum wet mash and water and were trained to press a lever on fixed-interval or fixed-ratio schedules of reinforcement with electrical brain stimulation. Fourteen rats ate at least 150% more mash during intermittent reinforcement sessions than during baseline, massed reinforcement control, and/or extinction sessions. In a 3-hr session, 11 of those 14 consumed more than 22 g of wet mash (13 g dry weight), the equivalent of nearly half an animal's daily food intake. In subsequent control sessions, the electrodes did not support stimulus-bound eating despite attempts to make stimulation parameters optimal. These results indicate that the eating was schedule induced or adjunctive, and suggest that the procedure may provide an animal model of excessive nonregulatory eating that contributes to obesity in humans.     

Brain transections selectively alter ingestion and behavioral activation in neonatal rats

Food-deprived neonatal rats actively ingest milk that is infused into their mouths through intraoral cannulas. This ingestion is accompanied by behavioral activation. The involvement of various brain regions in ingestion and activation was examined by making transections along the neuraxis from the olfactory bulbs to the anterior pons in 2-day-old rats. Following a 24-hr deprivation period, a series of oral milk infusions was given, and milk intake and activity were measured. Intake was severely reduced only in animals with diencephalic transections. Cuts in front of or behind the diencephalon resulted in normal or slightly decreased intake. In contrast, activity tended to decline as the level of the transection became more caudal. Thus ingestion and its accompanying behavioral activation could be separated neuroanatomically. These results suggest that two brain mechanisms are involved in the ingestive response of the infant rat, one in the diencephalon and another caudal to the mesencephalon. However, behavioral activation appears less discretely organized, involving most of the neuraxis.     

The genetic versus pharmacological invalidation of the cannabinoid CB(1) receptor results in differential effects on 'non-associative' memory and forebrain monoamine concentrations in mice

The endocannabinoid CB(1) receptor has been implicated in the inhibitory control of learning and memory. In the present experiment, we compared the behavioral response of CB(1) receptor knockout mice (CB(1)R(-/-)) with animals administered CB(1) receptor antagonist/inverse agonist SR141716A (rimonabant; 3 mg/kg IP, 30 min pre-trial) in terms of acquisition and retention of a habituation task and changes in cerebral monoamines. The results can be summarized as follows: (i) the acute and chronic invalidation of the CB(1) receptor resulted in an increase of behavioral habituation during the first exposure to an open field, indicative of enhanced acquisition of the task; (ii) CB(1)R(-/-) mice, but not rimonabant-treated animals, showed enhanced retention of the habituation task when re-tested 48 h and 1 week subsequent to the first exposure to the open field, respectively; (iii) the facilitation of retention of the habituation task in CB(1)R(-/-) mice was accompanied by a selective and site-specific increase in serotonin activity in hippocampus; and (iv) rimonabant-treated animals displayed 'antidepressant-like' neurochemical alterations of cerebral monoamines, that is, most parameters of monoaminergic activity were increased especially in dorsal striatum and hippocampus. Taken together, the present findings demonstrate that the genetic disruption of the CB(1) receptor gene can cause an improvement of behavioral habituation, which is considered to represent a form of 'non-associative' learning. Furthermore, our data support the assumption of a rimonabant-sensitive cannabinoid receptive site that is different from the 'classical' CB(1) receptor and which, under physiological conditions, might be involved in the inhibitory control of the acquisition but not retention of non-associative learning tasks.     

A dissociation between one-trial overshadowing and the effect of a distractor on habituation

Rats drank a novel vinegar flavour and were subsequently tested either for habituation of neophobia to vinegar or for the conditioning of an aversion to vinegar when it was followed 4 hr later by an injection of lithium chloride. If they drank a sucrose distractor immediately after their first vinegar trial, habituation of neophobia was disrupted but conditioning was not. Sucrose consumed 3.5 hr after the initial vinegar trial, on the other hand, had less of an effect on habituation, but did disrupt conditioning. An incidental finding, replicated in two subsequent experiments, was that the immediate sucrose distractor had no effect on habituation when animals were tested 48 hr after their initial habituation trial. We interpret these results to suggest that distractors affect habituation by a process of generalization decrement but overshadow conditioning through a process of associative competition.     

Dynamic changes in reinforcer effectiveness: satiation and habituation have different implications for theory and practice

Reinforcers lose their effectiveness when they are presented repeatedly. Early researchers labeled this loss of effectiveness as satiation without conducting an experimental analysis. When such an analysis is conducted, habituation provides a more precise and empirically accurate label for the changes in reinforcer effectiveness. This paper reviews some of the data that suggest that habituation occurs to repeatedly presented reinforcers. It also argues that habituation has surprisingly different implications than satiation for theory and practice in behavior analysis. For example, postulating that habituation occurs to repeatedly presented reinforcers suggests ways for maintaining the strength of an existing reinforcer and for weakening the strength of a problematic reinforcer that differ from those implied by an account in terms of satiation. An habituation account may also lead to different ways of conceptualizing the regulation of behavior. For example, habituation may be a single-process contributor to the termination of behaviors that are usually attributed to satiation (e.g., ingestive behaviors such as eating and drinking), fatigue (e.g., energetic behaviors such as running), the waning of attention (e.g., cognitive behaviors such as studying), and pharmacodynamic factors (e.g., drug taking).     

Effects of auditory frequency-shifts on zero and below-zero SCR habituation

The purpose of the present experiment was to test a procedure for the measurement of effects of zero- and below-zero habituation (BZH) on responding to frequency shifts in auditory stimuli. The present procedure avoided some of the drawbacks of other procedures, that is, long duration, ambiguity in the definition of BZH, and inadequate control procedures. Two groups received 18 stimulus presentations each; group 1 received first a tone of 1000 Hz 12 times, then 1400 Hz (test stimulus 1) 3 times, and 1850 Hz (test stimulus 2) 3 times. Group 2 received the same stimuli, but 3, 12, and 3 times, respectively. The procedure had the advantages of short duration of the experiment, zero habituation and BZH were operationally defined (as 3 and 12 stimulus presentations, respectively), and there were adequate control conditions since a control group that did not receive stimulus change on the relevant trial was employed. The results showed no effects of stimulus shifts on responding to the test stimuli. Group 2 responded significantly less than group 1 across trials, though, and this may be explained by an inhibitory process elicited by changes in weak stimulation during the habituation process.     

Changes in orienting and habituation in the rat following administration of chlorpromazine

Chlorpromazine (0.5-3.0 mg/kg) significantly reduced orienting to a novel auditory stimulus, but subsequent habituation after repeated presentations of the stimulus was not prevented nor significantly impaired. These results support the suggestion that the mechanisms underlying orienting and habituation are independent.     

Working memory capacity modulates habituation rate: Evidence from a cross-modal auditory distraction paradigm

Habituation of the orienting response is a pivotal part of selective attention, and previous research has related working memory capacity (WMC) to attention control. Against this background, the purpose of this study was to investigate whether individual differences in WMC contribute to habituation rate. The participants categorized visual targets across six blocks of trials. Each target was preceded either by a standard sound or, on rare trials, by a deviant. The magnitude of the deviation effect (i.e., prolonged response time when the deviant was presented) was relatively large in the beginning but attenuated toward the end. There was no relationship between WMC and the deviation effect at the beginning, but there was at the end, and greater WMC was associated with greater habituation. These results indicate that high memory ability increases habituation rate, and they support theories proposing a role for cognitive control in habituation and in some forms of auditory distraction.     

Habituation in the rat fetus.

Rat fetuses exhibit motor and cardiac responses to chemosensory stimulation on Days 20 and 21 of gestation. The first experiment demonstrated that fetuses exhibit an increase in overall motor activity and decrease in heartrate in response to an initial intraoral infusion of a lemon solution. After a series of nine exposures, however, fetuses no longer exhibit motor or cardiac responses to lemon infusion, suggesting the existence of a habituation-like process. Responsiveness recovers spontaneously following a 3- to 9-min period without stimulation. In a second experiment, a dishabituation treatment was administered to distinguish habituation, which is a centrally mediated decrement in response, from effector fatigue, sensory adaptation, and other peripheral mechanisms that can result in reduced responsiveness. A single infusion of mint following a series of nine lemon exposures was effective in reinstating fetal motor responses to lemon on both Days 20 and 21, but reinstated cardiac responses only on Day 21. Rat fetuses habituate to repeated chemosensory stimulation, suggesting the utility of the habituation paradigm in measuring CNS development during the perinatal period.     

Habituation in the rat fetus

Rat fetuses exhibit motor and cardiac responses to chemosensory stimulation on Days 20 and 21 of gestation. The first experiment demonstrated that fetuses exhibit an increase in overall motor activity and decrease in heartrate in response to an initial intraoral infusion of a lemon solution. After a series of nine exposures, however, fetuses no longer exhibit motor or cardiac responses to lemon infusion, suggesting the existence of a habituation-like process. Responsiveness recovers spontaneously following a 3-to 9-min period without stimulation. In a second experiment, a dishabituation treatment was administered to distinguish habituation, which is a centrally mediated decrement in response, from effector fatigue, sensory adaptation, and other peripheral mechanisms that can result in reduced responsiveness. A single infusion of mint following a series of nine lemon exposures was effective in reinstating fetal motor responses to lemon on both Days 20 and 21, but reinstated cardiac responses only on Day 21. Rat fetuses habituate to repeated chemosensory stimulation, suggesting the utility of the habituation paradigm in measuring CNS development during the perinatal period.     

Extraversion and the orienting reaction habituation rate to visual stimuli

Eysenck's (1967) proposal that introversion is characterized by increased levels of activity in the cortico-reticular loop was treated in a series of experiments which compared high, middle, and low extraversion groups on the basis of OR habituation rate to visual stimulation. Generally, introverts were observed to have longer OR habituation rates to chromatic and word stimulation than extraverts as evidenced by cardiac, electrodermal, and vasomotor indices of habituation rate, a result which endorses Eysenck's hypothesis. Results are also discussed from the standpoint of individual differences in autonomic response.     

Neonatal auditory habituation and state change

Groups of newborn babies were exposed to various series of 90 dB SPL noiseband stimuli or to simulated (control) stimuli, while their heart rates (HR) and states of behavioural arousal were monitored. In general the response to stimulation was an accelerative HR change which tended to decrease with repeated stimulation. This seemed to provide evidence of habituation to the auditory stimuli. However, the HR response to sound depended on prestimulus HR and on state, and, when these effects were removed by regression techniques, the progressive decrease in evoked HR with repeated stimulation disappeared, apart from the first few trials. This implied that there was HR habituation to the initial stimuli, but not subsequently, when the apparent HR “habituation” reflected progressive endogenous state changes.     

Olfactory test performance and its relationship with the perceived location of odors

Odors are generally perceived as arising via the nose when sniffed and as part of an orally located flavor during ingestion. The perceived location of an odor may in part be an attentional phenomenon, with concurrent oral stimulation occurring at the expense of access to the olfactory channel. Two predictions were derived from this account: (a) tasks dependent on a capacity to attend to the olfactory channel--odor discrimination and naming--should be adversely affected by oral localization; and (b) tasks not dependent upon a capacity to attend--incidental learning/recognition memory--should not. Using a procedure to generate oral localization, in which odors were presented via the nose with concurrent oral stimulation (sucrose, a viscous fluid or water), greater reported oral localization was associated with poorer odor discrimination and naming, but not with recognition memory performance. These results support the notion that attentional processes contribute to oral localization of odors by reducing the capacity to attend to the olfactory channel.     

The Effects of Novel Stimuli on Water Ingestion in Bobwhite Quail (Colinus Virginianus)

Fifteen adult bobwhite quail (Colinus virginianus) were exposed to a series of single- and two-bottle preference tests in order to evaluate sensory sensitivity, habituation, and the effect of novelty. Control animals were exposed only to distilled water to provide a baseline whereas experimental birds were presented colored or flavored water in corresponding, counterbalanced test sequences. Although the initial presentation of a novel color or flavor led to a marked reduction in intake, subsequent presentations of color, but not flavor, led to rapid habituation. Implications of the strength of avoidance of gustatory stimuli are discussed.

     

Long-term habituation to spatial novelty in blind cave fish (Astyanax hubbsi): role of the telencephalon and its subregions

Blind cave fish, when released into a novel environment, show a typical exploratory behavior characterized by high swim speed along walls shortly after release. This behavior wanes during prolonged exposure and thus may reflect habituation to novelty. As the hippocampus of mammals, which plays a crucial role in spatial learning, is part of the telencephalon, the possible involvement of this brain structure of fish was investigated in exploratory behavior. Ablation of the whole telencephalon or bilateral removal of dorsal parts of the hemispheres reduced activity; in contrast, unilateral lesions of one hemisphere, bilateral lesions of dorsal and dorsoventral parts, and removal of olfactory bulbs increased activity. However, the time course of habituation in a novel environment remained unchanged, except for ablated animals in which there was virtually no habituation in swim speed. These data suggest that the telencephalon of fish may not participate in long-term habituation to spatial novelty but, rather, support the notion of the telencephalon being involved in generation of arousal.     

Retention of orienting reaction habituation in patients with postmeningoencephalitic epilepsy

A polygraphic study on habituation of the somatic, autonomic, and EEG components of the orienting reaction elicited by a repetitive auditory stimulus during successive (weekly) sessions was performed in 29 patients with postmeningoencephalic epilepsy (PME) and in 116 control subjects. The study evidenced significant retention disturbances of orienting reaction habituation (i.e., of learning), the “saving” of stimulation, achieved from one session to another to obtain the habituation criterion, being lesser in PME patients than in control subjects. The severity of habituation retention disturbances depended on seizure frequency, electroclinical form, and history, as well as on features of EEG tracings.     

The role of metabotropic glutamate receptors and cortical adaptation in habituation of odor-guided behavior

Decreases in behavioral investigation of novel stimuli over time may be mediated by a variety of factors including changes in attention, internal state, and motivation. Sensory cortical adaptation, a decrease in sensory cortical responsiveness over prolonged stimulation, may also play a role. In olfaction, metabotropic glutamate receptors on cortical afferent pre-synaptic terminals have been shown to underlie both cortical sensory adaptation and habituation of odor-evoked reflexes. The present experiment examined whether blockade of sensory cortical adaptation through bilateral infusion of the group III metabotropic glutamate receptor antagonist cyclopropyl-4-phosphonophenylglycine (CPPG) into the anterior piriform cortex could reduce habituation of a more complex odor-driven behavior such as investigation of a scented object or a conspecific. The results demonstrate that time spent investigating a scented jar, or a conspecific, decreases over the course of a continuous 10 minute trial. Acute infusion of CPPG bilaterally into the anterior piriform cortex significantly enhanced the time spent investigating the scented jar compared to investigation time in control rats, without affecting overall behavioral activity levels. Infusions into the brain outside of the piriform cortex were without effect. CPPG infusion into the piriform cortex also produced an enhancement of time spent investigating a conspecific, although this effect was not significant.