Consummatory Act Research Articles

IV nicotine self-administration in rats using a consummatory operant licking response: sensitivity to serotonergic, glutaminergic and histaminergic drugs.

Tobacco smoking is characterized by repeated self-administration of nicotine by placing the cigarette in the mouth. The repeated hand-to-mouth self-administration is essentially a consummatory act. We recently developed a paradigm in which rats lick one of two spouts to trigger intravenous (IV) delivery of nicotine, which combines a consummatory act with rapid delivery of nicotine to model the act of tobacco smoking. We have found that rats will lick hundreds of times per nicotine infusion. In the current study, using the operant licking nicotine self-administration model with young adult Sprague-Dawley rats (0.03mg/kg/infusion of nicotine), we tested the effect of antagonists of H1 histamine receptors pyrilamine, serotonin (5HT) type 2 receptors ketanserin and N-methyl-d-aspartate (NMDA) glutamate receptors with d-cycloserine as well as an agonist of 5HT2c receptors lorcaserin, in dose ranges that we have found in previous studies to significantly reduce IV nicotine self-administration with the operant lever press operand. The H1 antagonist pyrilamine significantly reduced operant licking for nicotine self-administration. Pyrilamine caused significant reductions in the operant licking paradigm at lower doses (10 and 20mg/kg) than those we previously observed to affect responding in the operant lever press paradigm. In contrast, the 5HT2A and C antagonist ketanserin did not show an effect of reducing nicotine self-administration in the same dose range we had found in a previous study to significantly reduce operant lever press nicotine self-administration. The 5HT2C agonist lorcaserin significantly decreased nicotine self-administration in the licking paradigm at the same dose threshold as with lever press responding. The NMDA glutamate partial agonist d-cycloserine did not produce any change in nicotine self-administration with the licking operand, in contrast to its effect on the classic lever-pressing task. The rat model incorporating consummatory aspects of tobacco addiction can provide distinct and potentially more relevant information concerning possible new avenues of treatment to combat tobacco addiction.

Neural mechanisms of sexual behavior in the male rat: Emphasis on ejaculation-related circuits

Sexual behavior of the male rat can be described as a ‘sequence’: a series of behavioral transitions eventually leading to a consummatory act: ejaculation. A ‘funnel-model’ is presented to describe the behavioral progression during the sexual sequence.The ejaculation itself is extensively controlled by the ‘spinal ejaculation generator’, consisting of several elements with afferent sources of genitosensory information, with ascending projection fibers to inform the brainstem and forebrain as well as with descending afferent fibers providing the supraspinal control mechanisms with the opportunity to restrict ejaculations to the optimal moments and circumstances.The messages ascending from the spinal cord reach several interconnected thalamic, hypothalamic and limbic brain areas and are integrated with olfactory information. These brain areas play a role in mechanisms like ‘sexual satiety’ or a temporary interruption of sexual activities (post-ejaculatory interval), but the exact facilitatory and inhibitory mechanisms involved have not been elucidated yet. In the ‘downward’ mechanisms controlling the spinal ‘release’ of an ejaculation, the medial preoptic nucleus plays an important role in cooperation with a number of brainstem areas. This nucleus is also explicitly involved in the rewarding experiences coming with an ejaculation.Finally, the role of several neurotransmitters and-peptides on male sexual behavior are discussed shortly, because sometimes they show remarkable effects on specific aspects of the behavioral sequence. We conclude that, despite our increased knowledge about the brain mechanisms involved in the control of ejaculation, we are still far away from a complete understanding and quite a few questions remain to be resolved.

Behavioral characterization of amygdala involvement in mediating intra-accumbens opioid-driven feeding behavior.

The present experiments were conducted to provide a more detailed behavioral analysis of the dissociable roles of the basolateral (BLA) and central nucleus (CeA) of the amygdala in mediating intra-accumbens (Acb) opioid-induced feeding of a high-fat diet. Confirming previous findings, temporary inactivation of the CeA with the GABAA agonist muscimol reduced DAMGO (D-Ala2-NMe-Phe4-Glyol5-enkephalin)-induced and baseline food intake, whereas intra-BLA muscimol selectively blocked only DAMGO-induced food intake, leaving baseline feeding intact. However, although inactivation of the BLA reduced DAMGO-induced food intake to control levels, this treatment led to exaggerated number and duration of food hopper entries after food intake had ended. A subsequent experiment under conditions of limited access to the diet found the identical pattern of behavior following intra-Acb administration of DAMGO, regardless of whether the BLA was inactivated. Last, BLA inactivation was shown to have no influence on feeding driven by a state of negative-energy balance (24-hr food deprivation), demonstrating a specific influence of the BLA on opioid-driven feeding. These findings suggest that BLA mediates palatability-driven feeding and that this influence is particular to the consummatory act of ingestion.

Discrete neurochemical coding of distinguishable motivational processes: insights from nucleus accumbens control of feeding

The idea that nucleus accumbens (Acb) dopamine transmission contributes to the neural mediation of reward, at least in a general sense, has achieved wide acceptance. Nevertheless, debate remains over the precise nature of dopamine's role in reward and even over the nature of reward itself. In the present article, evidence is reviewed from studies of food intake, feeding microstructure, instrumental responding for food reinforcement, and dopamine efflux associated with feeding, which suggests that reward processing in the Acb is best understood as an interaction among distinct processes coded by discrete neurotransmitter systems. In agreement with several theories of Acb dopamine function, it is proposed here that allocation of motor effort in seeking food or food-associated conditioned stimuli can be dissociated from computations relevant to the hedonic evaluation of food during the consummatory act. The former appears to depend upon Acb dopamine transmission and the latter upon striatal opioid peptide release. Moreover, dopamine transmission may play a role in 'stamping in' associations between motor acts and goal attainment and perhaps also neural representations corresponding to rewarding outcomes. Finally, evidence is reviewed that amino acid transmission specifically in the Acb shell acts as a central 'circuit breaker' to flexibly enable or terminate the consummatory act, via descending connections to hypothalamic feeding control systems. The heuristic framework outlined above may help explain why dopamine-compromising manipulations that strongly diminish instrumental goal-seeking behaviors leave consummatory activity relatively unaffected.

Functional Magnetic Resonance Imaging in Conscious Animals: A New Tool in Behavioural Neuroscience Research

Functional magnetic resonance imaging (fMRI) is a unique window to the brain, enabling scientists to follow changes in brain activity in response to hormones, ageing, environment, drugs of abuse and other stimuli. There are two features that make fMRI unique when compared with other imaging modalities used in behavioural neuroscience. First, it can be entirely noninvasive: each animal can serve as its own control over the natural course of its life, vital for following neuroadaptation and other developmental processes critical to understanding behaviour. Second, fMRI has the spatial and temporal resolution to observe patterns of neuronal activity across the entire brain in less than a minute. Although fMRI does not have the cellular spatial resolution of immunostaining, nor the millisecond temporal resolution of electrophysiology, synchronised changes in neuronal activity across multiple brain areas seen with functional MRI can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviours. Thus, fMRI affords a systems approach to the study of the brain, complementing and building from other neurobiological techniques to understand how behaviour is organised across multiple brain regions. In this review, we present a general background to fMRI and the different imaging modalities that can be used in fMRI studies. Included are examples of the application of fMRI in behavioural neuroscience research, along with discussion of the advantages and disadvantages of this technology.

Infant Rodent Ultrasounds ? A Gate to the Understanding of Sound Communication

Components of the communication system between infant and adult rodents based on ultrasonic vocalizations (USVs) of infants are analyzed. USVs are most often emitted from a pup lost outside the nest in response to changes of: (i) body temperature, (ii) contact with adults/littermates, (iii) handling, and (iv) smell. These changes modulate the state of arousal and the emotional/motivational states and, as a result, USVs are produced. Acoustic properties of USVs seem to reflect the degrees of changes in arousal and emotion/motivation. Adult rodents are aroused by perceiving the USVs, locate the sender and show a phonotaxic approach to the sender. Acoustic properties of USVs in the frequency and time domains are described based on which adult rodents discriminate the USVs from other ultrasounds and take the USVs or adequate models of them as preferred goals of their phonotaxic approach. The preferred approach to adequate USVs is modulated by emotions/motivations, the sex of the receiver, hormonal states, experience with pups and neurotransmitter systems of the brain. The phonotaxis can be understood as the appetitive component of a pup-caring instinct. The consummatory act of the instinct is the retrieval of the lost pup. This retrieval is independent of USV presence, but it closes the communication loop activated by the emission of USVs. Communication with USVs can be used as a tool to investigate genetic and brain mechanisms of behavioral control.

Metabolic signals, hormones and neuropeptides involved in control of energy balance and reproductive success in hamsters.

In the 'postgenome era', most research on the neuroendocrine control of energy homeostasis has focused on hormonal and neuropeptide control of food intake (i.e. the amount of food eaten) in rats and mice. The amount of food consumed is influenced by both the motivation to procure food and the consummatory act of ingestion. In some species, the rate of food intake remains relatively constant, while survival is maintained via changes in food procurement, external storage and internal expenditure. For example, in hamsters, metabolic signals, peripheral hormones and central neuropeptides influence hunger motivation, food hoarding and changes in energy expenditure without necessarily influencing the amount of food ingested. A similar suite of metabolic signals, hormones and neuropeptides is involved in optimizing reproductive success under fluctuating energetic conditions. Reproductive processes are inhibited or delayed when energy expenditure outstrips energy intake and mobilization from storage. Estrous cyclicity in Syrian hamsters is sensitive to the availability of oxidizable glucose, but the presence of central glucose alone is not sufficient for normal estrous cycles. Food deprivation-induced anestrus does not depend upon food deprivation-induced increases in concentrations of adrenal hormones such as glucocorticoids. If hormones such as insulin and leptin play a role, they might do so by modulating the availability of glucose detected at extra-hypothalamic sites, instead of or in addition to direct effects on the mechanisms that control gonadotropin releasing hormone secretion. Despite our ability to measure and manipulate gene transcription, understanding of fuel homeostasis requires examination of indirect effects of hormones and neuropeptides on peripheral metabolism, attention to the motivational as well as consummatory aspects of ingestion, and the study of behaviour in a natural or seminatural context.

Anthropomorphic Interpretations and Ethological Descriptions of Dog and Cat Behavior by Lay People

ABSTRACTUnlike ethologists and veterinarians, lay people supposedly use their own unstructured observations to interpret their companion animals' behavior, often in anthropomorphic terms. Recently, anthropomorphism has evoked new interest amongst scientists as a result of provocative publications concerning “animal mind,” that have prompted investigations in the field of cognitive ethology, and much speculation about the emotions of animals. The purpose of the research reported here was to determine the concurrency and plausibility of anthropomorphic interpretations and ethological descriptions of dog and cat behavior and facial expressions, taking into account the observer's experience with the companion animal species. Independent sets of pet owners and non-owners (n=128) were presented with selected still photographs and edited video sequences to interpret, first spontaneously, then in a multiple choice mode. These were programmed on an interactive CD-Rom. Nested ANOVA showed that the choice of different kinds of multiple choice answers was influenced by their level of plausibility, by the personal experience which the people had had with the species, and by the species shown in stills or movie sequences. Scenes which were interpreted with high agreement of over 80% either showed key elements, a consummatory act, or the context in which the behavior took place. They generally represented scenes relevant to the relationship between an owner and an animal. The facial expressions of “fear” and “curiosity” in dog scenes and “stress” in cat scenes were also interpreted with agreement of over 80%.

Courtship in Desmognathine Salamanders: The Southern Dusky Salamander, Desmognathus auriculatus

-The courtship of the southern dusky salamander, Desmognathus auriculatus (Plethodontidae), is described for the first time. Most of a male's effort is expended in orienting to and stimulating (or 'persuading') his partner. Much of the stimulation provided by the male is tactile (nudging and rubbing), although he also exhibits behavior patterns associated with the transfer of courtship pheromones (snapping and pulling). Movements of the male's forelimbs may stimulate the female visually. The consummatory act of courtship is indirect sperm transfer by means of a spermatophore, and this stage of courtship appears identical in all desmognathines yet described. Courtship behavior patterns in the subfamily Desmognathinae are an apparent mosaic of ancestral and derived characters, with some evidence for homoplasy. Formal analyses of behavioral evolution await a robust phylogenetic hypothesis and detailed ethograms for multiple populations of all recognized taxa. The absence of lungs is a character shared by all salamanders in the family Plethodontidae (Duellman and Trueb, 1986). Reliance on cutaneous gas exchange may be a major constraint on the geographic distribution of these animals. The majority of taxa are found in relatively cool and moist habitats, especially in the montane regions of the Pacific Northwest and Appalachian Mountains of North America, and the cloud forests of Central America. An exceptional, but not unique, taxon is the southern dusky salamander, Desmognathus auriculatus (subfamily Desmognathinae), populations of which occur throughout the Gulf and Atlantic Coastal Plains of the southeastern United States. Winters typically are mild and summers warm and humid in these physiographic provinces. Well away from the mountains, D. auriculatus can be found in the organic debris along the shady margins of small streams, hypoxic pools and swamps. Little has been published on the natural history of the southern dusky salamander (but see Robertson and Tyson, 1950, for some observations of this species in eastern North Carolina). Here I report the first laboratory observations of this species' courtship and mating behavior. I then compare these to descriptions for other desmognathine salamanders, in anticipation of a formal, phylogenetic analysis of the evolution of courtship in this subfamily. MATERIALS AND METHODS Sexually mature D. auriculatus were collected in the summer of 1994 from several sites near the Savannah River Site in Aiken and Barnwell Counties, South Carolina (see Gibbons and Semlitsch, 1991). Most were found by raking through the organic debris on the margins of small pools. Desmognathus auriculatus is the only desmognathine that has been recorded in this part of South Carolina, although the presence of D. fuscus is possible (see Gibbons and Semlitsch, 1991). Each of my specimens was identified as D. auriculatus on the basis of body size, the presence of pale lateral spots, and the speckled appearance of the belly. Animals were transported to the laboratory in cooled containers, where they were maintained at approximately 15 C on a natural (Pullman, Washington) photoperiod. Salamanders were housed individually in plastic boxes measuring 9 x 17 x 31 cm, with a damp paper towel as substratum and a crumpled damp paper towel as a refuge. An ad libitum diet of vitamin-mineral dusted waxworms (moth larvae) was provided. I staged a total of seven heterosexual encounters between pairs of single males and females drawn from a pool of four males and two females. No two individuals were paired together more than once. Encounters were staged in a plexiglass observation arena measuring 17 x 17 x 5 cm, floored with a damp paper towel; no refuge was made available. Animals were introduced at approximately 1500 h and left together until 0800 h the following morning. All behavioral interactions were recorded under dim red illumination on a time-lapse videotape recorder (Panasonic AG-6010) using a low-light video camera (Panasonic WV-BD400).

Context conditioning: Positive reinforcing effects of various food-related stimuli

Rats were subjected to context preference tests to investigate the degree to which various manipulations involving food stimuli can be used to appetitively condition contextual cues. One manipulation consisted of placing hungry rats in a context that contained food that they could consume. A second one involved exposure to a context containing food that could only be seen and smelled, without consumption being possible. A third type of manipulation consisted of exposong animals to a context after the consumption of a small meal in the home cage. Finally, hungry, control subjects were merely exposed to a context containing an empty food tray. Preference for the context was only enhanced after the first type of manipulation, indicating that the actual consummatory act constitutes the major source of reinforcement in the present procedure. Olfactory and visual food cues, as well as postingestional aftereffects in isolation, did not function as reinforcers.

Attenuation of water intake and operant responding by dopamine D2 antagonists: raclopride provides important cues for understanding the functional mechanism of action.

The selective dopamine (DA) D2 receptor antagonist raclopride was found to attenuate operant lever-pressing with water as reward in a dose dependent manner and more potently than the corresponding consummatory act, i.e. the unconditioned water intake. This is the same way as previously reported for other DA D2 antagonists. In screening experiments raclopride has been selected on the basis of great separation between antagonism of DA-agonist induced hyperactivity, stereotypies and production of catalepsy. We found that attenuation of lever-pressing and water intake by raclopride were not more separated in dose than after, for example, haloperidol. We further found that attenuation of lever-pressing and water intake occurred in doses relatively lower than those producing catalepsy, thus excluding catalepsy as a cause for the attenuation. Decreased water intake in thirsty animals caused by a low dose of apomorphine (APO) was counteracted by raclopride. This has previously been found with DA D2, but not with D1, antagonists, which further supports that this apomorphine-effect is mediated via D2 receptors. However, raclopride only showed this antagonism in a narrow dose-range, like haloperidol. The selective profile previously found for sulpiride, proposed to be related to low incidence of extrapyramidal side-effects in the clinic, was thus not replicated.

Scopolamine reverses haloperidol-attenuated lever-pressing for water but not haloperidol-attenuated water intake in the rat

The operant lever-pressing response has previously been found to be inhibited by lower doses of haloperidol than the corresponding consummatory act, i.e., water intake. In the present study it was found that the attenuation of the lever-pressing response caused by the neuroleptic, but not the attenuation of the water intake, could be counteracted by scopolamine. The results support the notion that blockade of operant responding by low doses of neuroleptics are probably related to the extra-pyramidal side-effects of neuroleptics seen in the clinic, as both phenomena can be counteracted by anticholinergics. These results therefore conflict with the anhedonia hypothesis put forward as an explanation of the attenuating effects of neuroleptics in operant settings. The findings also have a clear bearing on the role of dopamine in feeding and drinking behavior, as the results implies that different aspects of the control of water intake (i.e., the operant vs. the consummatory phase) are governed by different mechanisms in the CNS.

Feeding and hypothalamic stimulation increase dopamine turnover in the accumbens

The hypothesis that the dopaminergic system plays a role in feeding behavior was tested in three experiments. First, microdialysis was performed in the nucleus accumbens (NAC) at 20 min intervals during free feeding in rats at 80% of normal body weight. Extracellular concentration of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) increased significantly during eating indicating an increase in DA turnover. Second, microdialysis samples were collected from the NAC during bar pressing with a) a signal light on and food available, b) the light on but no food available, c) neither light nor food. Only when food was available did extracellular DA, DOPAC and HVA increase significantly. This increase in DA turnover occurred in the accumbens but not in the ventral striatum. Third, electrical stimulation of the perifornical lateral hypothalamus (LH) that was capable of inducing feeding increased extracellular DA, DOPAC and HVA in the NAC. This occurred whether the animal had food to eat or not. The effect of LH stimulation on DA turnover resembled the effects of free feeding and operant feeding in Experiments 1 and 2. Perifornical LH stimulation did not increase dopamine turnover in the ventral striatum. The results show that perifornical LH stimulation activates the mesolimbic dopamine system and that dopamine release in the accumbens is involved in feeding. The increase in dopamine turnover outlasted the consummatory act. This suggests that accumbens dopamine may be related to sensory input, feeding reflexes, food reward or memory processes and not just to the consummatory act itself.

Blockade by neuroleptics of water intake and operant responding for water in the rat: Anhedonia, motor deficit, or both?

Four different neuroleptic drugs, haloperidol, metoclopramide, sulpiride and cis-flupenthixol, were tested for their ability to attenuate an operant lever-pressing response with water as reward and the corresponding consummatory act, i.e., the non-conditioned water intake. All four neuroleptic drugs tested more potently attenuated the operant lever-pressing response than the consummatory water intake, just as the conditioned avoidance response previously has been found to be more potently attenuated than the non-conditioned escape reaction. The results suggest that a certain class of learned behaviors, labelled operant or instrumental behaviors, are more susceptible to the attenuating effects of neuroleptic drugs than the class of behaviors labelled non-conditioned consummatory acts. It was further concluded that the attenuation of the lever-pressing response could be explained by a decreased ability of the animals to initiate or perform the required operant response (i.e., a motor deficit) while the attenuated water intake caused by higher doses of the neuroleptics could be interpreted as a motivational effect (e.g., “anhedonia”). When studying the effects of the neuroleptic drugs it is therefore of great importance to know whether the behavior measured in the particular experimental design used is operant or consummatory. The implications of the findings are discussed.

A motivational analysis of object play in juvenile dwarf mongooses ( Helogale undulata rufula)

The dwarf mongoose ( Helogale undulata rufula) has a play vocalization, a short pulse at the 2-kHz level which is repeated at a rate of 3 to 12 or more pulses/s during the entire play period. The repetition rate is indicative of motivation intensity. This motivational study on object play shows that: (1) play becomes fragmented prior to termination; (2) motivation changes during a session fall into three different patterns all terminating at a ‘set point’ or ‘sollwert’; (3) the behaviour patterns performed during play show little sequencing related to original context but are causally different from those of exploration and have ‘optimum intensities’; (4) more limbs employed in object manipulation indicate higher intensity irrespective of the original non-play context of the behaviour pattern concerned; and (5) high intensity is coupled with more behaviour patterns performed per time interval. Hand-reared isolates show a delay in the appearance of play in ontogeny in comparison with pair-raised animals and their play contains a higher frequency of patterns bringing the object into close bodily contact. Play is considered as being a behaviour pattern complex with its own motivation which, through its performance, may compensate for motivational deficits or surpluses, a set point or sollwert replacing a consummatory act. Behaviour patterns from other behavioural contexts are taken over and reordered with regard to different rules, hence the apparent lack of sequencing. A threshold of general excitation associated with stimulus input is postulated as regulating the time of appearance of play in ontogeny, not maturational factors, and it may be used to compensate for specific stimulatory deficits occurring during ontogeny.

"What Are We to Make of All This?" Reply to Berger and Zelditch

We are reminded of scenes in films from the past, those in which a form oozes out of a vat bubbling away in a laboratory. The thing proceeds to eat Brooklyn. It appears unstopable as it incorporates all it touches, unphased by missiles hurled at it. Smiling, it burps and slithers along. In the end the creature triumphs by consuming the planet. Nevertheless the film ends happily, since in its final consummatory act, the creature takes the form of the world it ate and all is as it was in the beginning. So it goes. The fantasy-sparking comment offered by Professors Berger and Zelditch, for all of its rhetorical elegance, iaises only minor and tangential points. We are accused of designing a faulty experiment for several reasons. According to Berger and Zelditch, we did not associate certain cues with the occupational status variable but rather made them part of the demeanor set. Supposedly, this resulted in suppressing the status variable while enhancing the behavioral variables. Also, the experiment suffered from a nonequivalence of cues. One might infer from the existence of the Berger and Zelditch comment that the operating rule for judging whether a particular variable is, in reality, a status variable, is whether or not it correlates positively with influence. If it does, Why, by George that proves it, it must be a status variable! And so, the theory absorbs it, smiles, burps and moves along. We have already noted that expectation states research seems to proceed as if predicated on the belief that the basic answer to the problem was known at the time the research work commenced and subsequent work was dedicated to the elaboration of the basic expectation states assumptions rather than to their testing. (Lee and Ofshe. 1981). Given what we assume to be the working bias involved-in expectation states research, one can understand the difficulty the creators have in under-

Drinking of the Pigeon (Columba Livia L.)

1. The consummatory part of the drinking behaviour of pigeons is studied by a frame-by-frame analysis of high-speed films and X-ray motion pictures. 2. A double-suction or vacuum-pump model is formulated for the mechanics of drinking. Consummatory drinking is a series of similar movement cycles, each transporting one dose of water into the oesophagus. The swallowing movement cycle shows five phases: 1, capillary action of the beak tips; 2, lingual suction; 3, pharyngeal preparation; 4, pharyngeal suction; and 5, oesophageal collection. A double build up of an area of low air pressure occurs. As a result of the retraction of the tongue in the mouth (acting as a piston in a cylinder) low air pressure develops in the buccal cavity and water is sucked into the mouth. Secondly, a lower air pressure area develops in the pharynx as a result of a depression of its floor, so that the water in the mouth is given a momentum caudad, by which it is forced over the larynx into the oesophagus. Neither peristaltic action, nor an alternative lower air pressure area is recorded in the oesophagus. The collection of the swallowed water at the lowest place occurs by gravity. 3. Using the mechanical requirements of the double-suction model the presence and distribution of glands was predicted. As predicted the following glands were found: the gl. lingualis superior et inferior, the gl. mandibularis anterior et posterior, the gl. palatina posterior externa, the gl. cricoarytenoidea and the gl. sphenopterygoidea. 4. The application of a comparator model for the description of the stereotypy of the pecking behaviour for the drinking behaviour showed that the drinking swallowing cycle and the three types of eating swallowing cycles were basically similar. The difference, apart from those of amplitude, was the coupling of the erection of the ventral pharyngeal valves to the pro- and retraction of the linguolaryngeal apparatus. The erection occurs during drinking at the very start of the protraction, but during pecking at the start of the retraction. Further, the consummatory act of drinking is composed of some smaller fixed elementary movement units. These units are fixed for mechanocybernetical reasons. The decision points between these units though masked under normal conditions, were found at the start of the capillary phase and during the preparatory phase by experimental manipulation. 5. A possible evolutionary scenario for the double-suction mechanism is discussed. It is suggested that: 1, the feeding system is maximized for food transport by using the slide-and-glue mechanism rather than using the ancestral catch-and-throw mechanism; that 2, the feeding system was maximized for water transport by using the double-suction mechanism rather than the ancestral tipping-up mechanism; that 3, high selection pressure on fast transport of seeds has occurred and that lack of selection pressure on fast drinking was probable. From this may be concluded that the slide-and-glue mechanism is the primar mechanism and the double-suction secondar. This secondary development is in itself a simple change of coupling of one of the subunits already developed as a pecking submechanism, the erection of the ventral pharyngeal valves. Although this recoupling falls completely within the mechanical boundary conditions of the slide-and-glue mechanism so that no reconstruction of the mechanical part of the system is required, nevertheless some strong selection pressure might be necessary for the evolution of a double-suction mechanism since valve erection was found to be part of different centrally coordinated fixed elementary units in swallowing both during eating and drinking. Such an external selection pressure could not be found. Finally, it was shown that for the explanation of the evolutionary scenario of suction drinking the monistic adaptationist programme was not sufficient, and a dualistic neodarwinian approach and a multifactor analysis were advocated.

Changes in unit responses to tones after food reinforcement in the auditory pathway of the rat: Intertrial arousal

Experiments were carried out to determine the effects of short-term changes in behavioral arousal on the responsiveness to auditory stimuli of medial geniculate and inferior colliculus neurons in the rat. The independent variable was the time of presentation of the signals after a food pellet, the assumption being that the animal's state of arousal might vary after a consummatory act, and that this fact in turn might modify unit activity. Eight different periods were tested in a random order of presentation, the periods varying between 20 and 180 s from the time of presentation of a food reward. The findings indicate increased responsiveness after long intervals, as measured in peak response firing rate, together with decreased spontaneous rate in a 200-ms period before the auditory signals (background rate). The results demonstrate that variations in arousal during the short periods between food rewards in the paradigm tested influence both the spontaneous rate of discharge and the responsiveness of auditory neurons to sensory input, but that the pattern of changes is different in the medial geniculate and in the inferior colliculus. These variations are of a short-term nature compared with the long-term variations that have come to be expected with changes in the motivational or sleep-wake state of the animal. Recognition of this type of modulating influence is of great importance to neurophysiological studies of learning, in view of the fact that associative neural changes have to be extracted from the nonassociative changes that occur simultaneously.

Stimulus Control of Covert Behaviors (Urges)

In order to test the homogeneity assumption, which states that overt and covert behaviors obey the same laws, four subjects who reported covert smoking urges prior to engaging in the consummatory act of smoking were recruited to self-monitor urges and smoking behavior. The data from two subjects in Experiment 1 supported the view that urges are not artifactual byproducts of consummatory response occurrence, because frequencies of urges and smoking behavior were uncorrelated when subjects were asked not to smoke on alternate days. Stimulus control of urges was demonstrated in Experiment 2; urges were more likely in a situation that was associated with smoking than in a nonsmoking situation. This finding is consistent with the hypothesis that urges are reinforced by the associated consummatory act.

Negativism to food during self-stimulation in the anterior part of the basal forebrain in dogs

A negative response to food was found in 7 dogs self-stimulating in 8 loci within the nucleus entopeduncularis, nucleus commissurae anterioris, the preoptic area and the lateral hypothalamus. In 6 dogs this appeared simultaneously in three forms: (1) ignoring food (FI) during self-stimulation; (2) food rejection (FR), i.e. interruption of the animal's attempt to reach meat upon experimenter-exerted stimulation of the rewarding site, and (3) food ejection (FE) consisting of throwing a piece of meat out of the mouth when the current was switched on at the beginning of the consummatory act. The seventh dog displayed an approach-avoidance behavior, and only FI and FR were observed. None of the three forms of negativism to food was seen in two other dogs self-stimulating in 3 sites. Negative response to food, particularly when it appears as FE, may indicate that the rewarding value of the stimulus depends on excitation of the neural system controlling satiety.