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Biomedical subjects

W G Hall

Publications and source records attributed to W G Hall.

At least 37 records · Page 2Linked to original sources
PubMed1993

Integration of oral habituation and gastric signals in decerebrate rat pups.

During a series of oral infusions of a sweet solution, the ingestive responses of young rat pups habituate; pups stop responding to the infusions even when their stomachs are empty and the infused diet is nonnutritive. The rate of this oral habituation is enhanced by the addition of gastric fill signals, even in decerebrate pups. In intact but not in decerebrate pups, prior deprivation gates out the influence of gastric fill on habituation. This oral habituation system, responsive to multiple ingestion-related signals, may serve as the elemental process that integrates physiological state with ongoing behavior to control ingestion.

Animal Feed↗
PubMed1992

Oral habituation in rat pups is in the brainstem.

We have previously demonstrated a decremental, oral, experienced-based control of ingestion in rat pups that is potent, diet-specific, and long lasting. This control of ingestion is revealed in the decreases in mouthing responses of rat pups to repeated oral stimulation, a phenomenon that is well described as oral habituation. The present study examined the neural basis for oral habituation by examining the responses of decerebrate 10-day-old rat pups to repeated, brief infusions of a sucrose solution. Like neurologically intact pups, decerebrate pups showed distinct decreases in mouthing responses following a series of oral infusions. Thus, oral habituation is present in the hindbrain. Although intact pups demonstrated sensitization by showing increased responding to the first few stimulus presentations, decerebrates failed to show a sensitization to the stimulation. These results suggest that while the brainstem alone is sufficient for the expression of oral habituation, the forebrain also influences oral responsivity in intact animals.

Aging↗
PubMed1992

Ontogeny of feeding motor patterns in infant rats: an electromyographic analysis of suckling and chewing.

During mammalian ontogeny, there is a transition from suckling to the chewing of food. The question was asked: Is suckling a neuromuscular precursor to chewing, or are suckling and chewing independent systems? Electromyograms (EMGs) were recorded in rat pups of ages 6, 9, 12, 15, 18, and 21 days from the superficial masseter, anterior digastric, sternohyoideus, and genioglossus muscles during suckling and chewing. The EMG patterns of the 3 components of suckling behavior (nipple attachment, rhythmic sucking and the stretch response) are distinctive from one another and reflect the musculoskeletal biomechanics of suckling. Chewing EMGs are present by 12 days of age and attain the adult pattern by 18-21 days of age. During nipple attachment, pups exhibit a motor pattern that is similar to that of adult chewing, but other aspects of suckling differ from chewing in some EMG features. Comparison of EMGs between behaviors and between ages allowed interpretation of the degree of contunity of muscular activity across the suckling-to-chewing transition.

Aging↗
PubMed1992

Control of ingestion by oral habituation in rat pups.

The role of habituation of mouthing activity in the control of ingestion was investigated in 6-, 12-, and 18-day-old rat pups. In pups at all ages, oral habituation to a flavored diet inhibited ingestion of a continuous oral infusion of that same diet. Twelve-day-old pups that had orally habituated to a diet continued to consume less of a continuous oral infusion of that diet both 30 min and 3 hr later, and the duration of suppressed ingestion was shown to be dependent on the rate of stimulus presentation during habituation experience. These data suggest that oral habituation may be a diet-specific influence on both intra- and intermeal patterning.

Animals↗
PubMed1991

The early presence of food-oriented appetitive behavior in developing rats.

The appetitive behavior of 3- to 6-day-old rat pups was studied by testing their ability to direct their ingestive behavior to a restricted food source. We found that, from 3 days of age, pups were able to feed efficiently from such a source. More specifically, pups that were deprived of nutrition but not of maternal care as well as pups that were dehydrated ingested significantly more than nondeprived animals, and did so whether liquid diet was spread over the entire floor surface beneath them or restricted to a fraction of the floor surface. However, pups that had been nutritionally and maternally deprived were not able to direct their feeding. The general locomotor activation of pups in this latter group appeared to interfere with their ability to direct their behavior to the restricted source. These results indicate that from early ages, developing rats possess the appetitive competence to guide their behavior and suggest that previous findings of poorly directed behavior were a confound of the behavioral activation shown by pups tested in a state of maternal deprivation.

Animals↗
PubMed1991

Effects of hydrational state on ingestion in infant rats: is dehydration the only ingestive stimulus?

The physiological stimulus for deprivation-enhanced ingestion was studied in developing rats. During an overnight deprivation period, continuous gastric infusions of isotonic saline or milk were made to 6- and 15-day-old rat pups in order to preferentially maintain hydrational or hydrational and nutritional status, respectively. Pups' ingestion was then studied in oral-infusion tests. In 6-day-old pups that received either milk or saline infusions, ingestion was depressed relative to intake in pups that were simply deprived. But in 15-day-old pups, only milk infusions reduced intake. These findings suggest that the increased ingestion stimulated by deprivation in pups less than a week of age results primarily from dehydration, and thus that nutrient-related feeding does not emerge until later in development.

Animals↗
PubMed1991

Analysis of 2-DG autoradiograms using image-averaging and image-differencing procedures for systems-level description of neurobehavioral function.

Computer assisted 2-deoxyglucose (2-DG) autoradiography has been used to provide functional maps of areas of altered neural activity related to changes in an animal's behavior or state. The standard procedure for comparison of autoradiograms between different treatment groups has been to take measurement samples from predefined neuroanatomical regions and to average these across brains to attain statistical sensitivity for detecting treatment effects. Unfortunately, when sampling is restricted to predefined areas, important topographic information is lost along with the ability to reveal an unexpected change in neural activity. To preserve the rich topographical detail of metabolic information and to enhance the capacity to uncover novel areas of altered metabolic activity, we have developed a system for averaging entire images from 2-DG autoradiograms and for comparing the average images from two experimental groups by creating an image of differences. This procedure does not rely on sampling only preselected regions, but still allows statistical comparisons between experimental groups. The procedures we describe can be readily and inexpensively adapted for use in individual laboratories and are based on modifications of preexisting image analysis software. We show that, when average and difference images are created using standardized protocols for sectioning brain tissue and editing section images, they are impressively resolved and realistic and can serve as effective topographic descriptions of group differences in neural activity of functional and behavioral relevance.

Animals↗
PubMed1991

Habituation of oromotor responding to oral infusions in rat pups.

The influence of oromotor experience on the pattern of ingestion in rat pups and the relation of this influence to age and pups' physiological state were investigated using a procedure designed to mimic the sham-feeding preparation in adult rats. Six-, 12-, and 18-day-old pups received brief intra-oral infusions of sucrose solutions once every minute. Small infusion volumes minimized postoral effects. Pups' oromotor responsiveness was assessed by recording the pattern of mouthing behavior continuously during the test. Pups were tested after 24, 6 or 0 h deprivation. During testing, the mouthing behavior of all pups except 24-hr deprived 6-day olds showed a marked decline. The specificity of this decrement was demonstrated in a second experiment in which the decremented response was restored by a switch in solution flavor. Finally, the influence of postoral signals on the decline in responsiveness was evaluated by comparing the oral responsiveness of 18-day-old pups following intragastric, oral, or no infusions. Oral infusions suppressed subsequent oral responding, but intragastric infusions did not. These results provide evidence for a habituation-like role of oromotor experience in determining patterns of ingestive behavior within a feeding test. Here, major determinants of the pattern of decline were pups' physiological state and developmental age.

Aging↗
PubMed1990

Developmental change in unilateral olfactory habituation is mediated by anterior commissure maturation.

Habituation of an orienting response in rat pups was used to study the development of the anterior commissure (AC) and its role in olfactory memory. Six- and 12-day-old pups received odor presentations to one side of their olfactory system and were tested later for habituation to additional presentations made to either the trained or untrained side. Six-day-old pups remembered only on the trained side. Twelve-day-old pups remembered when tested on either side. Transection of the AC in 12-day-old pups before, but not after, training prevented the transfer of memory. Thus, between 6 and 12 days of age, olfactory cross-projections carried in the AC mature and provide a functional substrate for transfer, at the time of training, of a form of olfactory learning.

Aging↗
PubMed1989

A nutritive control of independent ingestion in rat pups emerges by nine days of age.

The emergence of controls of independent ingestion in rat pups was studied using nutritive (0.6 M glucose in saline or water) and vehicle gastric preloads. Two hours after preloading, ingestive responses were assessed in a 30-minute test of feeding from the floor. In 6-day-olds, all preloads had similar effects on consumption of a milk diet. In 9-day-olds, however, glucose-water preloads inhibited intake compared to water preloads. This inhibition was secondary to an effect on gastric emptying. Glucose preloads also inhibited intake in 12- and 15-day-olds. Behavioral observations indicated that feeding patterns were altered in response to glucose preloads in 9-day-olds. These results provide evidence for the emergence of a nutritive, postgastric control of independent ingestion between 6 and 9 days of age.

Aging↗
PubMed1989

Neural systems for early independent ingestion: regional metabolic changes during ingestive responding and dehydration.

The ingestive behavior of young rodents, studied independently of the mother and suckling, provides a system for the developmental analysis of the neurobiology of feeding and drinking. In these experiments regional neural metabolic activity, as assessed by semiquantitative deoxyglucose (DG) autoradiography, was related to dehydration and ingestive behavior in 6-day-old rat pups. During simple ingestive responding, changes in relative DG uptake, representative of changes in neural metabolic activity, occurred primarily in hindbrain sensory and motor nuclei. Producing cellular dehydration resulted in activity changes primarily in the basal forebrain. When pups were dehydrated and allowed to ingest during the DG-uptake period, activity changes were seen in both the hindbrain and forebrain areas that responded to ingestion or dehydration alone as well as in regions that were not affected by either manipulation alone. These latter changes, which result from an interaction of behavioral and physiological stimuli, call attention to areas that may subserve motivational aspects of behavior. Extracellular dehydration was found to produce fewer and different forebrain responses in neural metabolic activity. During ingestion, the only effects of extracellular dehydration that overlapped with those of cellular dehydration appeared in circumventricular hypothalamic regions and brain stem motor nuclei. Thus, there appeared to be only a limited final common pathway for these two types of dehydration-induced drinking. Taken together, these findings in infant rats depict distributed neural systems subserving ingestion and responding to state change. They provide a starting point early in ontogeny for the developmental analysis of neural substrates of ingestive systems.

Animals↗
PubMed1988

Reinforcers in infancy: classical conditioning using stroking or intra-oral infusions of milk as UCS.

Six-day-old rats received 20 forward pairings of an odor-conditioned stimulus (CS) with one of two unconditioned stimuli (UCS); 1) intra-oral milk infusions or 2) stroking with a sable-hair brush. These UCS's produce a common general response of increased behavioral activity, but different specific behaviors. For each UCS, additional pups received backward pairings of the CS and UCS, random pairings of the CS and UCS, CS only, UCS only, or no stimuli. Four hours later, pups received a two-odor choice test to assess the development of an odor preference and a CS-only test to assess the acquisition of conditioned responding (CR). The results of the two-odor choice test indicated that for both UCS's only forward pairings of the CS and UCS resulted in an odor preference. Similarly, the CS-only test showed that only forward pairings of the CS and either UCS were effective in producing CR's; pups that received forward pairings exhibited increased behavioral activity during presentations of the CS, which is an unconditioned response (UCR) to both UCS's. Only the forward paired CS-milk UCS group exhibited increased mouthing and probing during the CS only test; these are UCR's that occur to milk infusions but infrequently to the stroking UCS. These results demonstrate the development of similar conditioned odor preferences using behaviorally activating UCS's, but CR's which are specific to the form of the UCR.

Animals↗
PubMed1988

Developmental change in the access to olfactory memories.

Memory for a learned odor preference can be functionally confined to one side of the brain in 6-day-old rat pups by preferentially stimulating a single naris and corresponding olfactory bulb during training. We report here that this form of unilateral learning is present only during the first postnatal week; older pups show bilateral recall of unilateral olfactory experience. The maturation of bilateral learning probably depends on the postnatal growth and development of olfactory commissural fibers, because infantlike unilateral learning and memory is reinstated when these commissural fibers are sectioned before training in older pups. Section of commissural fibers after training also resulted in unilateral preferences. This latter finding indicates that the learned odor preference of older pups tested with the untrained naris open depends on access to unilaterally stored memories on the contralateral side, access provided by the newly developed commissural projections.

Aging↗
PubMed1988

Ingestive behavior in preweanling rats: emergence of postgastric controls.

Previous studies have indicated that the termination of intake in very young rat pups is controlled almost exclusively by the level of gastric fill; nutritive cues from diet have no effect on intake. In the present series of experiments, we investigated the ontogeny of postgastric nutritive controls of intake in rat pups ingesting independent of their dam. In 6-day-old pups, the level of gastric fill required to terminate ingestion was not affected by the presence or absence of post-gastric nutritive cues, but by 15 days of age a greater level of gastric fill was required to stop ingestion when postgastric cues were eliminated by a closed pyloric noose. This emergent post-gastric contribution to the inhibition of intake in 15-day-old pups does not depend on preexisting gastric fill signals, as sham-feeding pups (open gastric fistula) with nutrients in their intestines ingested less than pups without intestinal nutrients. These results provide evidence that postgastric controls of ingestive behavior mature during the postnatal period and just shortly before they are required at weaning.

Aging↗
PubMed1987

New routes to early memories.

Stimulation of one side of the olfactory system during training with odor-milk pairings in neonatal rats results in their ability to recall an odor memory by using the trained but not the untrained side of the brain. In 12-day-old rats, olfactory learning can be recalled by stimulation of either the trained or untrained side. The development of bilateral recall reflects the maturation of olfactory commissural pathways that provide access to the olfactory memory stored on the contralateral side. Furthermore, the commissural pathways need not be present at the time of memory formation but can establish new and specific access to already existing olfactory memories.

Aging↗
PubMed1987

Maternal and nutritional contributions to infant rats' activational responses to ingestion.

Infant rats deprived of food, maternal care, and the opportunity to suckle display a dramatic behavioral activation and vigorously ingest when provided milk through oral cannulas. These experiments assessed which components of deprivation are important in producing these responses to milk. Nutritional deprivation alone, with or without the presence of an active maternal female, appears to be sufficient to produce ingestion. Behavioral activation, on the other hand, appears to require both nutritional deprivation and deprivation from a maternal female. The effect of maternal stimulation on later behavioral reactivity was not a function of the pups' opportunity to suckle. However, active maternal stimulation was more effective in preventing activation than was passive maternal stimulation (e.g., thermotactile and olfactory stimulation). Stimulation provided by an active, nonlactating mother was effective in preventing behavioral activation, but the effect was short-lived, lasting only 2 hr after the pup was removed from the mother's care. This series of studies thus reveals that identified components of maternal separation have dissociable effects on appetitively motivated behaviors in infant rats.

Animal Nutritional Physiological Phenomena↗