Eliot Stellar

Memory in Mice as Affected by Intracerebral Puromycin

The antibiotic, puromycin, caused loss of memory of avoidance discrimination learning in mice when injected intracerebrally. Bilateral injections of puromycin involving the hippocampi and adjacent temporal cortices caused loss of short-term memory; consistent loss of longer-term memory required injections involving, in addition, most of the remaining cortices. Spread of the effective memory trace from the temporal-hippocampal areas to wide areas of the cortices appears to require 3 to 6 days, depending upon the individual animal. Recent reversal learning was lost while longer-term initial learning was retained after bilateral injections into the hippocampal-temporal areas.

The Neurobiology of Motivation and Reward

This book was conceived many years ago as an abstract goal for a father-son team when the father was working in university administration and the son was just getting into the academic business. Eventually, the father returned to the laboratory, the son began to get his feet on the ground, and the goal became concrete. Now the work is finished, and our book enters the literature as, we hope, a valuable contribution to understanding the terribly complex and subtle problem of the neuro biology of motivated behaviors. We would also like the book to stand as a personal mark of a cooperative relationship between father and son. This special relationship between the authors gave us an extra dimension of pleasure in writing the book, and it would delight us if it gave anyone else an extra dimension of enjoyment from reading it. One thing we hope happens is that anyone or simply considering entering similar considering a similar partnership, of this book as encouragement. Such re fields, will take the existence lationships are highly satisfying if both parties take care to protect the partnership. When we actually sat down to write the book, we were humbled by the immense literature and the smallness of both our conceived space for putting it down and of our brains for processing all the information.

The effects of repeated cycles of weight loss and regain in rats

This study examined the metabolic effects of weight cycling, i.e., repeated periods of weight loss followed by regain. There were three groups of adult, male Sprague-Dawley rats: (1) Chow Controls (a normal weight control group fed chow throughout); (2) Obese Controls (animals fed a high-fat diet throughout); and (3) Obese Cycling (obese animals cycled through two bouts of caloric restriction and refeeding). The cycled animals showed significant increases in food efficiency (weight gain/kcal food intake) in the second restriction and refeeding periods compared to the first, i.e., weight loss occurred at half the rate and regain at three times the rate in the second cycle. Several physiological changes were associated with this cycling effect. At the end of the experiment, cycled animals had a four-fold increase in food efficiency compared to obese animals of the same weight who had not cycled. These data suggest that frequent dieting may make subsequent weight loss more difficult. The possible metabolic and health consequences of yo-yo dieting are discussed.

Attentive, Affective, and Adaptive Behavior in the Cat Sensory deprivation of the forebrain by lesions in the brain stem results in striking behavioral abnormalities

Lesions of the lateral portion of the upper midbrain, involving medial, lateral, spinal, and trigeminal lemnisci primarily, result in a consistent syndrome of symptoms in the cat. (i) There is a marked sensory deficit, characterized mainly by sensory inattention and poor localization in the tactile, proprioceptive, auditory, gustatory, and nociceptive modalities, where direct pathways are interrupted. Similar defectsappear in vision and olfaction where no known direct or primary paths are interrupted. (ii) These cats are characterized by a lack of affect, showing little or no defensive and aggressive reaction to noxious and aversive situations and no response to pleasurable stimulation or solicitation of affection or petting. The animals are mute, lack facial expression, and show minimal autonomic responses. (iii) They show a hyperexploratory activity characterized by incessant, stereotyped wandering, sniffing, and visual searching, as though hallucinating. This behavior appears to be centrally directed and is very difficult to interrupt with environmental stimuli. (iv) They also demonstrate exaggerated oral activities: they snap in response to tactile stimulation of the lips, seizing and swallowing small objects even if inedible; they overeat; they hold objects too large to swallow (a mouse, a catnip ball) firmly clamped in the mouth for long periods of time; they mount and seize other animals (rat, cat, dog, monkey) by the back or the neck; they lick and chew the hair and skin of the back or tail incessantly when confined in a cage. In interpreting these results we emphasize the view that the syndrome is due chiefly to the extensive, specific, sensory deprivation produced by interruption of the lemnisci at the rostral midbrain. The relation of these findings to the effects of sensory isolation in man and animals, to the effects of midbrain lesions and neodecortication, to parietal lobe syndrome in primates, and to the behavior of autistic children is discussed. It is our belief, from these studies, that the symptoms produced by interruption of the lemnisci, characterized by a high degree of somatotopic and modality localization, are due to a loss of patterned sensory input to the forebrain, particularly to the neocortex and to the rostral midbrain. Without a patterned afferent input to the forebrain via the lemnisci, the remaining portions of the central nervous system, which include a virtually intact reticular formation, seem incapable of elaborating a large part of the animals repertoire of adaptive behavior (45).

Responses of lean and obese subjects to preloads, deprivation, and palatability ☆

The effects of preloads, deprivation, and palatability on the eating behavior of non-dieting lean and obese subjects were studied during laboratory meals, using small solid food units (SFUs) to measure the rate of ingestion over the time-course of the meals. In both weight groups, rate of intake decreased from the beginning to the end of meals. The smaller the preloads and the longer the deprivation interval, the faster subjects ate at the beginning of meals and the higher their hunger ratings were. The longest deprivation interval also increased palatability ratings, meal length, and the total amount that subjects ate. Increasing the palatability of the food increased the rate of intake at the beginning of meals, meal length, and the amount of food that subjects ate. Obese subjects were more sensitive to palatability and less responsive to deprivation than lean subjects. For example, while lean subjects became less discriminating about the palatability of the food at the beginning of meals as deprivation increased, obese subjects did not. The satiation mechanism of obese subjects was also different from lean subjects. For example, obese subjects overate after preloads while lean subjects underate compared to their baselines.

Sugar and Fat: Sensory and Hedonic Evaluation of Liquid and Solid Foods

Twenty-five subjects evaluated the sweetness, creaminess and fat content of liquid and solid dairy products containing between 0.1 and 52 g fat/100 g and sweetened with 0-20% sucrose weight/weight. Liquid stimuli included skim milk, whole milk, half and half, and heavy cream, while the solids included cottage cheese and cream cheese, blended and spread jelly-roll fashion on slices of white bread. The subjects ratings of stimulus sweetness, creaminess, and fat content differed sharply between liquids and solids, and the assessment of fat content of solid foods appeared to be impaired. In contrast, acceptability ratings for both sets of stimuli were not substantially different: the subjects optimally preferred equivalent levels of sugar in both liquids and solids, but selected higher fat levels in solid than in liquid foods. Sensory preferences for fat in liquid stimuli may not always be indicative of preferences for fat in solid foods.

Bite size, ingestion rate, and meal size in lean and obese women ☆ ☆☆

The effect of bite size on ingestion rate, satiation, and meal size was studied in nine lean and nine obese women. On separate days, subjects were given one of three bite sizes of sandwiches and one of two bite sizes of bagels with cream cheese to eat in a laboratory lunch. Decreasing bite size significantly lowered ingestion rate for the whole meal. The effect was most pronounced at the beginning of meals. As bite size decreased from 15 to 5 g, the average ingestion rate decreased from (mean +/- SEM) 19.4 +/- 2.0 to 15.9 +/- 2.0 g/min (p < 0.001). The initial ingestion rate decreased from 30.0 +/- 2.9 to 19.6 +/- 1.7 g/min (p < 0.001). The larger the bite size, the more quickly ingestion rate decelerated; by the end of meals, ingestion rate was not different across conditions. The decrease in ingestion rate with smaller bites was offset by an increase in meal duration, such that meal size did not differ across conditions. Eating behavior of lean and obese subjects was not different. There were individual differences related to ingestion rate, but these were not related to body weight nor to meal size. These results bring into question the recommendation of behavior therapists that obese people eat more slowly in order to eat less.

Memory and cerebral protein synthesis in mice as affected by graded amounts of puromycin

Abstract The effects of intracerebral injections of graded amounts of puromycin on memory and on degree and duration of inhibition of cerebral protein synthesis have been studied in the mouse. As the concentration of the antibiotic was decreased it became progressively less effective in its behavioral and biochemical effects so that memory was retained in an increasing proportion of animals as the effect on protein synthesis diminished.

Direct Measurement of Food Intake in Man: A Method for the Objective Study of Eating Behavior

&NA; A method for the direct measurement of food intake in man is described. This method provides a means for independently studying many of the variables which are thought to operate in the control of food intake. A liquid diet from a hidden reservoir was ingested through a straw during a 20‐min. breakfast or lunch meal. Subjects were tested at the same time each day for several weeks. Stable ingestion patterns emerged after four or five trials. The ingestion of a constant amount of liquid diet at various intervals before the test meal depressed intake as a function of the time interval. Subjective hunger ratings correlated well with rate and amount ingested and were reduced appropriately by ingestion prior to the test meal.

Effect of naltrexone on food intake, hunger, and satiety in obese men

Increasing doses of naltrexone (25 to 200 mg) given over 4 consecutive days reduced intake of laboratory luncheon meals by 30% in 17 obese men. Meal size remained suppressed in the laboratory during the week following naltrexone administration. Water intake in the laboratory and body weight were not affected. Rates of ingestion and subjective ratings suggested that naltrexone reduced appetite rather than promoted early satiation. Nausea and other side effects occurred on 1 or 2 days during the naltrexone week in seven subjects whose food intake was reduced. Food intake was also reduced in seven of the remaining 10 subjects who reported no adverse reactions. These results suggest that a conditioned taste aversion or a conditioned anorexia may have developed in some subjects.