Chronic sweet intake lowers pain thresholds without changing brain mu- or delta-opiate receptors

Sprague-Dawley rats drank sweetened (3% dextrose + 0.144% saccharin, w/v) or unflavored water for 18 days and subsequent pain reactivity was assessed using a hot plate. Compared to the rats that consumed unflavored water, the rats that consumed sweet water responded more quickly on the hot plate indicating that their threshold for pain was lowered. Another group of rats given identical exposure to the fluids had their brains prepared for measuring opiate receptor binding using the delta-receptor ligand [3H]D-Ala-D-Leu-enkephalin ([3H]DADLE) and the mu-receptor selective ligand [3H]Tyr-D-Ala-Gly-MePhe-Gly-ol ([ 3H]DAGO). Binding of these opiates to mu- and delta-receptors in the cerebral cortex, striatum, hippocampus, hypothalamus, brain stem, and remaining brain regions was the same for the rats that drank sweet fluids and those that drank unflavored water. These findings suggest that drinking sweet fluids lowers pain thresholds but does not alter mu- and delta-receptors.     

Scopolamine interactions with D1 and D2 antagonists on radial-arm maze performance in rats

Recent evidence indicates that acetylcholine and dopamine play complementary roles in cognitive as well as motor functions. In our previous study, the dopamine receptor blocker, haloperidol, was found to attenuate the radial-arm maze choice accuracy deficit caused by the muscarinic acetylcholine receptor blocker, scopolamine. Haloperidol has activity in blocking both D1 and D2 dopamine receptor subtypes. The current study was conducted to determine whether this dopamine-acetylcholine interaction specifically involved D1 or D2 dopamine receptors. The D1 antagonist, SCH 23390, and the D2 antagonist, raclopride, were administered with a dose of scopolamine which caused choice accuracy deficits in the radial-arm maze. The scopolamine-induced deficit was reversed by SCH 23390, the D1 antagonist, indicating that D1 blockade alone is sufficient to reverse the amnestic effects of muscarinic blockade. There was no indication in this study that the D2 blocker, raclopride, had a similar effect. However, this does not mean that such an effect may not be present at other doses of raclopride or with other D2 antagonists. The present finding that D1 blockade counteracts scopolamine-induced cognitive dysfunction not only furthers the understanding of dopamine-acetylcholine relationships in cognitive function, it also suggests a promising direction for the development of treatments for cognitive dysfunction due to cholinergic loss.     

Understanding the central processing limit in consistent-mapping visual search tasks

Effects of load (i.e., the number of stimuli in the display) have been observed in multiple-frame studies using a consistent mapping of stimuli to responses (e.g., Fisher, 1982, 1984). In a series of four experiments, it is shown that these effects are not the consequence of differences across the high- and low-load conditions in either decision noise or peripheral masking. Additionally, it is shown that of two modes of limited capacity (a limited-channel and divided-capacity model) considered as possible explanations of load effects in tasks where subjects are required to locate a target, only one--the limited-channel model--is consistent with the results from all three location tasks. Finally, it is argued that the limited-channel model predicts not only the behavior observed in the four consistent-mapping experiments reported in this article but also the behavior observed in several related consistent-mapping tasks (Kleiss & Lane, 1986; Shiffrin & Gardner, 1972).     

Mental rotation: effects of dimensionality of objects and type of task

The original studies of mental rotation estimated rates of imagining rotations that were much slower when two simultaneously portrayed three-dimensional shapes were to be compared (R. Shepard & J. Metzler) than when one two-dimensional shape was to be compared with a previously learned two-dimensional shape (Cooper and her associates). In a 2 X 2 design, we orthogonally varied dimensionality of objects and type of task. Both factors affected reaction times. Type of task was the primary determiner of estimated rate of mental rotation, which was about three times higher for the single-stimulus task. Dimensionality primarily affected an additive component of all reaction times, suggesting that more initial encoding is required for three-dimensional shapes. In the absence of a satisfactory way of controlling stimulus complexity, the results are at least consistent with the proposal that once three-dimensional objects have been encoded, their rotation can be imagined as rapidly as the rotation of two-dimensional shapes.     

Some tests of the interactive-activation model for word identification

Summary The interactive-activation model postulates (a) that activation at the letter level leads automatically to activation at the word level, (b) that the word-superiority effect reflects reactivation of letters by the word they spell, and (c) that subjects identify words on the basis of information obtained from separate letter-position channels. In the first two experiments, we showed words in upper, lower, or mixed case: the word-superiority effect was reduced when words were presented in mixed-case letters, presumably because extra-letter information is lost with mixed-case presentation; i.e., postulate (c) is wrong. The third experiment showed that when the letters of a word are rotated 180° subjects can identify the letters without producing a word-superiority effect; i.e., one of postulates (a) and (b) is wrong. In Experiments 4 and 5, we trained subjects to name words presented in inverted letters; training was more effective when subjects could exploit bigram information in addition to letter-channel information; i.e., reading inverted text is based on extra-letter-feature information, not on a general skill in rotating letters. Taken together, our data deny three of the interactive-activation model's major postulates. We offer some suggestions for future versions of the model. Electronic mail: Userid: MEWHORTD; Nodeid: QUCDN; Domain: BITNET     

Insight-oriented group psychotherapy of latency-age children in an acute care setting

Traditional approaches to group therapy with latency-age children have stressed activity and nonverbal therapeutic interventions. These approaches originated in the 1940s with Slavson's activity aroup therapy. A review of the literature of the past 25 years reveals that many clinicians have increasingly employed verbal techniques with latencyage groups. Most such reports describe groups for latency-age out-patients. In this paper, a verbal, interpretive technique for group therapy with latency-age inpatients is described. Clinical vignettes are included to illustrate this technique. Our experience suggests that such a technique can become an integral part of the inpatient treatment program for the latency-age child.     

An evaluation of the Garren-Edwards diet and behavior modification program

This study evaluated the efficacy of the Garren-Edwards Behavior Modification Program, which uses the Garren-Edwards Gastric Bubble as an adjunct to treatment. Group therapy sessions were conducted with 23 morbidly obese subjects for 6 months on a biweekly basis. Each therapy session used a five-stage problem-solving sequence designed to facilitate adaptive behavioral alternatives. In evaluating weight change, a multivariate analysis of variance was conducted along with two preplanned orthogonal comparisons. Patients lost significant amounts of weight between initial to 3-month (p<.0001) and 3- to 6-month intervals (p<0001). A similar treatment effect was noted in an additional sample of 24 morbidly obese subjects following 3 months of treatment (p<0005). The findings support the value of longer goal-oriented programs in promoting continued weight loss. Implications for treatment process and therapist interventions prompted by this new format are discussed.     

Effect of the interintromission interval on lordotic response and attack latency in golden hamsters (Mesocricetus auratus)

After 12-15 ejaculatory series, each consisting of several short intromissions (2- to 3-s vaginal penetration) and an ejaculation, male golden hamsters adopt an altered copulatory pattern consisting of long intromissions (5- to 25-s penetration with intravaginal thrusting). Receptivity declines and the tendency for the female to attack the male increases at about the time of this shift in copulatory pattern. Because the mean interintromission interval (III) between short intromissions is about 8 s compared to 100 s between long intromissions, it is possible that females detect this difference and adjust their mating accordingly. When the III between short intromissions from a rested male was experimentally increased to 100 s by use of a halter and lead device, the duration of lordosis was significantly less than that displayed by females paired with control males (8-s III) and virtually the same as that displayed by females paired with males that produced only long intromissions. This suggests that the female uses the temporal patterning of intravaginal stimulation as one criterion for terminating mating with a particular male.     

Rodents' (Rattus, Mesocricetus, and Meriones) use of learned caloric information in diet selection

When given a choice between two mashes of equal caloric density but differing flavors, rats (Rattus norvegicus) show a robust preference for the flavor previously associated with a higher calorie food. This finding suggests that rats may identify food quality by sensory cues such as taste. Our initial attempt to show this effect in the golden Syrian hamster (Mesocricetus auratus) failed, apparently because of this species's tendency to store both high- and low-calorie mashes in their cheek pouches during conditioning trials. Initially we attempted to circumvent this seeming morphological constraint on learning by presenting low- and high-calorie mashes on alternate days. This procedure too failed to produce evidence of flavor-caloric learning, although this procedure produced robust learning in another rodent, the Mongolian gerbil (Meriones unguiculatus). Another method of preventing cheek pouching--concurrently presenting low- and high-calorie liquid diets--was more successful; then, hamsters showed clear evidence of flavor-caloric learning. Thus, although flavor-caloric learning is demonstrable in species of rodent besides the rat, the circumstances under which it occurs vary.     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): III. Contact calls

We trained budgerigars by operant conditioning to discriminate among a set of contact calls in a same-different task and analyzed response latencies from this task by using multidimensional-scaling (MDS) and cluster-analysis procedures. Humans listened to the same calls and indicated the similarity between pairs of calls by a direct rating procedure. An MDS program (sindscal) was used to arrange these complex acoustic stimuli in multidimensional space reflecting perceptual organization. Multiple regression techniques were used to identify the acoustic characteristics of contact calls that were correlated with the perceptual dimensions obtained from MDS. A number of spectral characteristics (e.g., peak frequency, rate of frequency modulation, and concentration of spectral energy) emerged as important for both budgerigars and humans, but the relative salience of these cues differed for the two species. Additional tests with two groups of budgerigars--cagemates and noncagemates--showed that experience with calls can change the salience of various acoustic characteristics used for perceptual organization and individual recognition.