Neocortex and feeding behavior in the rat.

Consummatory behavior and weight-regulation capacity were measured in 12 normal rats and in 43 rats that survived complete (C), sequential unilateral (U), anterolateral (A), or posterior (P) neocortical ablations. Groups C and A displayed aphagia and adipsia followed by a sequence of recovery stages gualitatively identical to, but shorter than, recovery typically seen following lateral hypothalamic lesions. After recovery, Group C displayed long-term effects of finickiness and pradial drinking. These effects as well as a measure of recovery of body-weight-regulation capacity were significantly intercorrelated with lesion size, and body-weight set point remained significantly lower than normal. Group U was relatively unaffected by the first unilateral ablation and showed, relative the second ablation but displayed the long-term effects. Group P, though significantly affected by the lesion, did not display the pattern or intensity of effects described for the other bilaterally ablated groups.     

Time-shared feeding and drinking

Barbary doves were tested in an operant situation in which they characteristically alternate between feeding and drinking. The experimental findings may be summarized as follows: (1) the cumulative distribution of the intervals between feeding bouts is little affected by reward rates; (2) a lock-on index is correlated with reward rate, but is not affected by altering reward rate per se, as long as the overall rate of ingestion remains the same; (3) when a primarily hungry animal is interrupted while feeding, or a primarily thirsty animal while drinking, the behaviour is resumed after the interruption; (4) when a primarily hungry animal is interrupted while drinking, or a primarily thirsty animal while feeding, the behaviour is resumed after a short interruption, but changes to the alternative behaviour following a long interruption; (5) titration of interruption period in the dominant region of the motivational state space is always stable, but becomes unstable if the dominance changes, or if the titrating criteria are reversed. From this evidence it is concluded that feeding and drinking can be time-shared in a manner analogous to that found in computers.     

Mechanisms underlying satiation of feeding behavior of the mollusc Aplysia

Animals filled almost to satiation by nonnutritive bulk do not satiate when they ingest a small amount of seaweed. This suggests that satiation is not triggered by chemostimulation of an anteriorly located "hot spot." Inflation of a balloon placed in the gut of the animal results in satiation as reflected in a number of different parameters of feeding behavior. The suppressive effect of a relatively brief inflation is rapidly and fully reversible, although repeated inflation and deflation appeared to produce slowly reversible or irreversible effects. The parameters of the changes in feeding during gut inflation are comparable to those of normal animals that are slowly fed individual pieces of food. The inflation volume needed to satiate the animal is a function of the rate of inflation--more rapid inflations requiring larger volumes. Cutting of the esophageal nerves results in a significant increase in the volume needed to satiate the animals, but nevertheless they eventually cease feeding and generally do not show a burst gut. The evidence indicates that the satiation that eventually occurs in nerve-sectioned animals, at least in part, is due to depression of feeding following very prolonged sensory stimulation. The data suggest that for a rapidly consumed meal, satiation results primarily due to distension-related gut signals conveyed by the esophageal nerves, whereas for very slowly consumed meals, the former factor interacts with a process associated with sensory stimulation, such as receptor adaptation. The current results indicate that balloon distension can serve as a reasonable stimulus in experiments in simplified preparations in which the nervous system can be studied.     

Internal stimuli enhance feeding behavior in the mollusc Aplysia

The hypothesis that subsatiating levels of internal food stimuli can arouse and potentiate feeding behavior was examined in the mollusc Aplysia californica. Animals were fed a small quantity of seaweed and their latencies to show biting responses were determined after food arousal was permitted to partially decay. Control animals were stimulated with food, but were not permitted to ingest it, or were fed nonnutritive glass-fiber filter paper. Compared to controls, animals that were fed showed significantly shorter latencies to respond when tested up to 80 min after previous exposure to food. These results indicate that internal stimuli can function like external stimuli to enhance responsiveness to food and suggest the hypothesis that satiation may be viewed as an interactive process involving the interplay of excitatory and inhibitory influences arising from the alimentary system.     

Pecking and feeding in chicks

Pecking is not controlled by nutritional state in a newly hatched chick, but by 3 days posthatch it normally is. This paper tests the hypothesis that first a chick must learn that pecking leads to ingestion; then, other (nonlearned) processes are automatically responsible for differential pecking rates to nutritive and nonnutritive items. The first experiment shows that experience pecking and ingesting sawdust is sufficient for differential pecking to develop. The second experiment shows that swallowing without pecking (using a force-feeding technique) does not lead to differential pecking. The third experiment shows that pecking without swallowing (using sand glued down to the floor) also does not lead to differential pecking. Finally, the last experiment shows that food deprivation affects pecking rate only after pecking and ingestion have been associated. These results support the above hypothesis that pecking followed by ingestion leads to the “attachment” of the pecking response to the feeding system. Motivational independence of pecking and the hunger system, the association of pecking with ingestion, and the development of behavior systems are discussed. It is concluded that the function of a behavior may not be related to its causes.     

Breast feeding: religious influences

In Orthodox Jewish communities, mothers are expected to breast-feed their infants and this expectation is to some extent based on religious beliefs. The degree to which this expectation promotes breast-feeding success was assessed by comparing a group of 50 Orthodox Jewish mothers with a group of 50 secular Jewish mothers in regard to infant feeding practices. All of the women lived in the Yeoville suburb of Jahannesburg, South Africa. An effort was made to interview all Orthodox mothers with at least 1 child under the age of 5 living in the area and it was assumed that the 50 mothers in the study constituted all or most of that population. A group of 50 secular mothers, comparable in age, education, and general living conditions, was also interviewed. The 50 Orthodox mothers had a total of 155 children and the secular mothers had a total of 119 children. Despite the quasi-religious motivation of the Orthodox mothers to breast-feed, there were few differences in the infant feeding practices of the 2 groups. At the age of 1 month the ratio of breast-fed to bottle-fed infants was 2.5:1 for the infants of Orthodox mothers and 2.3:1 for the infants of secular mothers. At age 6 months the ratio was 1:3 for both groups. At age 9 months the ratio was 1:6.4 for Orthodox mothers and 1:6 for secular mothers. The children of Orthodox mothers were breast-fed for an average of 5 months while the children of mothers of secular children were breast-fed for 4-1/2 months.