Non-interaction of ventromedial and lateral hypothalamic mechanisms in the regulation of feeding and hoarding behaviour in the rat

Lesions of the hypothalamic ventromedial nucleus (VMN) led to an immediate increase in food intake but not to any increase in hoarding activity. Later, when subjects were very obese, they failed to hoard even in response to a 16-hr. deprivation schedule, although this schedule did produce hoarding if body weights were held at, or were brought down to, preoperative levels. These results indicate that the lateral hypothalamic mechanism responsible for hoarding and feeding responds to long-term nutritional factors, and that it is not directly affected by the short-term satiety mechanisms in the VMN. These findings support the hypothesis (a) that even “non-physiological” activities (e.g. hoarding, exploration) are motivated by physiological needs, and (b) that the reason these activities do not ordinarily covary with physiological drives is that, unlike the physiological drives, they are not subject to inhibition by the hypothalamic satiety mechanisms.     

Book reviews

The Journal of Value Inquiry -     

The effect of overtraining and repeated extinctions on speed of extinction in electrical self-stimulation

Fourteen rats with hypothalamic electrodes needed at least 3,000 reinforcements in self-stimulation before extinction scores reached their peak. In a series of up to 36 further extinctions and reconditionings, involving a total of 10,500 reinforcements, extinction scores fell to the extreme low values typical of self-stimulation. The extent of this fall was shown to depend on the number of extinctions administered, but not on the number of reinforcements, indicating that a process of conditioned inhibition may be partially responsible for rapid extinction after self-stimulation.     

Stress-induced Fos-like Immunoreactivity in the Pons and the Medulla Oblongata of Rats

Immunoreactivity of the immediate early gene c-fos was used to investigate changes in the activity of brainstem neurons in response to acute stressors like immobilization, formalin-induced pain, cold exposure, hemorrhage and insulin-induced hypoglycemia. Different stressors induced Fos-like immunoreactivity in different pontine and medullary neurons. A single, 3 hour immobilization was found to be a very strong stimulus that activated brainstem catecholaminergic (tyrosine hydroxylase-immunopositive) neurons and cells in the raphe and certain pontine tegmental nuclei, as well as in the reticular formation. Pain, induced by a subcutaneous injection of formalin was also effective on catecholamine-synthesizing neurons and on others cells in the nucleus of the solitary tract. Cold exposure activated cells mainly in the sensory spinal trigeminal and parabrachial nuclei and in the so-called "pontine thermoregulatory area". Moderate Fos-like immunoreactivity was induced by a hypotonic (25%) hemorrhage in medullary catecholaminergic neurons, the nucleus of the solitary tract and the Barrington nucleus. Among stressful stimuli used, insulin-induced hypoglycemia elicited the smallest Fos activation in the lower brainstem. The present observations indicate that different stressors may use different neuronal pathways in the central organization of the stress response.     

Audience-contingent variation in action demonstrations for humans and computers

People may exhibit two kinds of modifications when demonstrating action for others: modifications to facilitate bottom-up, or sensory-based processing; and modifications to facilitate top-down, or knowledge-based processing. The current study examined actors' production of such modifications in action demonstrations for audiences that differed in their capacity for intentional reasoning. Actors' demonstrations of complex actions for a non-anthropomorphic computer system and for people (adult and toddler) were compared. Evidence was found for greater highlighting of top-down modifications in the demonstrations for the human audiences versus the computer audience. Conversely, participants highlighted simple perceptual modifications for the computer audience, producing more punctuated and wider ranging motions. This study suggests that people consider differences in their audiences when demonstrating action.     

Physiological drives investigated by means of injections into the cerebral ventricles of the rat

A technique is described for permanently implanting a cannula in the lateral ventricle of the rat, and the effects on certain physiological drives of various substances injected by this route were investigated.

Food intake was significantly reduced by intraventricular glucose, while intra-ventricular fructose, insulin, glucagon and a lipid-mobilizing agent were without effect. Drinking was elicited by hypertonic saline and suppressed by hypotonic solutions. The intake of salt was not effected by intraventricular low-sodium solutions. Intraventricular procaine, but not alcohol, induced an akinetic state. Intraventricular glucose failed to relieve hypoglycaemic coma.

The significance of some of these findings is discussed in relation to the hypothalamic regulation of hunger.     

Social audiences can disrupt learning by teaching

To investigate the effect of a social audience on learning-by-teaching, we examined participants' solutions of the 4-ring Tower of Hanoi problem after they demonstrated the 3-ring problem to a social agent (a person) or a non-social agent (a computer). In Introduction, Discussion participants produced less optimal solutions of the 4-ring problem after demonstrating the 3-ring problem to a social agent. An analysis of pointing behavior demonstrated that social highlighting contributed substantially to this effect. Together, these findings indicate that more social highlighting may produce a cost, rather than a benefit, on how deeply the demonstrator encodes the problem solution. Experiment 3 clarified that these results were not simply caused by the disruptions inherent to social highlighting. Taken together, the results suggest that social highlighting does not come for free — producing the highlighting may lead to more shallow encoding of demonstrated actions.     

Adrenergic stimulation of the rat diencephalon and its effect on food intake and hoarding activity

The diencephalic area most sensitive to microinjections of noradrenaline lay outside the area of the lateral hypothalamus in which feeding can be produced by electrical stimulation. Injection of either area, including injections that caused increased feeding, failed to have any effect on hoarding activity. Since hoarding can be elicited both by food deprivation and by electrical stimulation of the lateral hypothalamus, these findings indicate biochemical, anatomical and motivational differences between the central feeding mechanism sensitive to adrenergic stimulation, and that responding to electrical stimulation or nutritional depletion. The former mechanism may be disinhibitory; the latter, excitatory.     

Book reviews

ROBINSON, J. O. The psychology of Visual Illusion. London: Hutchinson University Library. 1972. Pp. 285. £ 3.00.

CARROLL, JOHN B. and FREEDLE, Roy O. (Eds). Language Comprehension and the Acquisition of Knowledge. New York: John Wiley. 1972.

PEARSON, R. The Avian Brain. London: Academic Press. 1972. Pp 624. £ 10.00.

KORNBLUM, S. (Ed.). Attention and Perfomance IV. New York and London: Academic Press. 1973. Pp. xxx+771. $ 18.50.

WASON, P. C. and JOHNSON-LAIRD, P. N. Psychology of Reasoming: Reasosming: Structure and Content. London: B. T. Batsford Limited. 1972. Pp 26.4. £ 3.50.

GILBERT, R. M. and MILLENSON, J. R. (Eds). Reinforcement: Behavioural Analysis. New York: Academic Press. 1972. Pp. xiii+288. £ 6.35.

STRONGMAN, K. T. The Psychology of Emotion. London: Wiley. 1973. Pp. 191. £ 3.50.

MYERS, R. D. (Ed.). Methods in psychobiology. Vol. 2. London and New York: Academic Press. 1972. Pp. xii+398. £ 6.50.

NILSSON, N. J. Problem-Solving Methods in Artificial Intelligence. New York: McGraw-Hill. 1971. Pp. 255. POund 5.40.

SHEEHAN, P. W. (Ed.). The function and Nature of Imagery. New York: Acadmic Press. 1972. Pp. $ 22.50.

CLARKE, E. and DEWHURST, K. An Illustrated of Brain Furction. Oxford: Sandford Publication. 1972. Pp. 154. £ 5.50.

SCHACHTER, S. Emotion, Obesity and Crime. New York: Academic Press. 1971. Pp. 195. £ 3.50.

MCGUIGAN, F. J. and LUMSDEN, D.B. (Eds). Contemporary Appraches to Conditioning and Learning. Washingotn, D. C.: v. H. Winston and Sons. 1973. Pp. xii+231. £ 6.50.

BECK, J. Surface Colour Perception. Ithaca and London: Cornell University Press. 1972.Pp. £ 11.50.