Our study indicates that individuals with TI deletion generally have more behavioral and psychological problems than individuals with the TII deletion or UPD. Four recently identified genes have been identified in the chromosome region between BP1 and BP2 with 1 of the genes (NIPA-1) expressed in mouse brain tissue but not thought to be imprinted. It may be important for brain development or function. These genes are deleted in individuals with TI deletion and are implicated in compulsive behavior and lower intellectual ability in individuals with TI versus TII.

Purpose The mean length of children’s utterances is a valuable estimate of their early language acquisition. The available normative data lacks documentation of language and nonverbal intelligence levels of the samples. This study reports age-referenced MLU data from children with specific language impairment and children without language impairments. Method 306 child participants were drawn from a data archive, ages 2;6–9;0 years, 170 with SLI and 136 control children. 1564 spontaneous language samples were collected, transcribed and analyzed for sample size and MLU in words and morphemes. Means, standard deviations, and effect sizes for group differences are reported for MLUs, along with concurrent language and nonverbal intelligence assessments, per 6-month intervals. Results The results document an age progression in MLU words and morphemes, and a persistent lower level of performance for children with SLI. Conclusions The results support the reliability and validity of MLU as an index of normative language acquisition and a marker of language impairment. The findings can be used for clinical benchmarking of deficits and language intervention outcomes, as well as comparisons across research samples.

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Advances in genetics have led to an increased understanding of the role of the genotype on behavioural functioning. The purpose of the present study was to examine differences in intellectual functioning in individuals with Prader-Willi syndrome (PWS) with a paternal 15q11-q13 deletion versus maternal uniparental disomy (UPD) of chromosome 15. Measures of intelligence and academic achievement were administered to 38 individuals with PWS (24 with deletion and 14 with UPD). The subjects with UPD had significantly higher verbal IQ scores than those with deletion (P< 0.01). The magnitude of the difference in verbal IQ was 9.1 points (69.9 versus 60.8 for UPD and deletion PWS subjects, respectively). Only 17% of subjects with the 15q11-q13 deletion had a verbal IQ > or = 70, while 50% of those with UPD had a verbal IQ > or = 70. Performance IQ scores did not differ between the two PWS genetic subtype groups. This is the first report to document the difference between verbal and performance IQ score patterns among subjects with PWS of the deletion versus the UPD subtype.

Objective: Prader-Willi syndrome (PWS) is a genetic disorder associated with developmental delay, obesity, and obsessive behavior related to food consumption. The most striking symptom of PWS is hyperphagia; as such, PWS may provide important insights into factors leading to overeating and obesity in the general population. We used functional magnetic resonance imaging to study the neural mechanisms underlying responses to visual food stimuli, before and after eating, in individuals with PWS and a healthy weight control (HWC) group. Research Methods and Procedures: Participants were scanned once before (pre-meal) and once after (post-meal) eating a standardized meal. Pictures of food, animals, and blurred control images were presented in a block design format during acquisition of functional magnetic resonance imaging data. Results: Statistical contrasts in the HWC group showed greater activation to food pictures in the pre-meal condition compared with the post-meal condition in the amygdala, orbitofrontal cortex, medial prefrontal cortex (medial PFC), and frontal operculum. In comparison, the PWS group exhibited greater activation to food pictures in the post-meal condition compared with the pre-meal condition in the orbitofrontal cortex, medial PFC, insula, hippocampus, and parahippocampal gyrus. Between-group contrasts in the pre-and post-meal conditions confirmed group differences, with the PWS group showing greater activation than the HWC group after the meal in food motivation networks. Discussion: Results point to distinct neural mechanisms associated with hyperphagia in PWS. After eating a meal, the PWS group showed hyperfunction in limbic and paralimbic regions that drive eating behavior (e.g., the amygdala) and in regions that suppress food intake (e.g., the medial PFC).

Dramatic increases in childhood obesity necessitate a more complete understanding of neural mechanisms of hunger and satiation in pediatric populations. In this study, normal weight children and adolescents underwent functional magnetic resonance imaging (fMRI) scanning before and after eating a meal. Participants showed increased activation to visual food stimuli in the amygdala, medial frontal/orbitofrontal cortex, and insula in the pre-meal condition; no regions of interest responded in the post-meal condition. These results closely parallel previous findings in adults. In addition, we found evidence for habituation to food stimuli in the amygdala within the pre-meal session. These findings provide evidence that normal patterns of neural activity related to food motivation begin in childhood. Results have implications for obese children and adults, who may have abnormal hunger and satiation mechanisms.

Research techniques based upon the behavioral principles of operant conditioning have provided a complementary approach to the standard pharmacologic analysis of physical dependence upon opiates (SEEvE~S 1936(SEEvE~S , 1958. With these techniques, a simple arbitrary response is conditioned by following it with a reinforcement. For example, a food deprived rhesus monkey learns to press a lever because pressing a ]ever leads to a pellet of food. By the same token, if a lever pressing response is followed by the injection of an opiate to a physically dependent animal, that response will be learned.Using the general principle outlined above, several investigators have recently demonstrated that it is possible to condition physically dependent rats to emit operant responses for morphine reinforcement. NichoLs and co-workers (1956, 1959), have shown that dependent rats will learn to drink water containing morphine rather than the initially preferred morphine-free tap water. W~Ks (1960, ]962) has recently shown that unrestrained rats can be conditioned to emit a lever-pressing response to receive intravenously infused morphine on a fixed ratio reinforcement schedule. In addition, he has shown that pretreatment with nalorphine produces an increase in rate of responding for the drug, presumably produced by the induced abstinence syndrome. General procedureThe experimental approach we have used is an extension of the lines of investigation based upon the principle of reinforcement of behavior by opiate administration, to permit an analysis of the interaction of pharmacological and behavioral variables in opiate dependence (Sc~uSTE~ *

Sixteen rats were initially exposed for 50 sessions to either a fixed-ratio 40 or an interresponse-time-greater-than-l1-second food reinforcement schedule, then shifted to a fixedinterval 15-second food reinforcement schedule. Animals with fixed-ratio 40 histories lever pressed at much higher rates under the fixed-interval schedule than did animals with interresponse-time-greater-than-11-second histories. This difference persisted across 93 sessions of fixed-interval exposure. The effects of d-amphetamine were assessed after 15 and 59 sessions of fixed-interval exposure. On both occasions, the low-rate responding of animals with interresponse-time-greater-than-l1-second histories was typically increased by all doses of the drug, while the high-rate responding of animals with fixed-ratio 40 histories was typically decreased by all doses of the drug. These results suggest that control response rate under the fixed-interval schedule, which may be affected by a history of responding under another schedule, is the primary determinant of the relative effects of d-amphetamine.Key words: operant history, fixed-interval schedule, fixed-ratio schedule, IRT greaterthan-t schedule, rate dependency, d-amphetamine, lever press, ratsThe effects of most behaviorally-active drugs on a given behavior depend critically on the steady-state characteristics of that behavior in the absence of the drug (Kelleher and Morse, 1968; Thompson and Schuster, 1968). Of particular importance is the rate of occurrence of the behavior. The effects produced by a number of compounds are so strongly influenced by response rate that they are termed rate-dependent (Dews, 1958;Dews and Wenger, 1977;Kelleher and Morse, 1968). d-Amphetamine prototypically exemplifies rate-dependency: with few exceptions, low doses of this drug decrease high-rate behaviors while increasing low-rate behaviors (e.g., Clark and Steele, 1966;Dews, 1958;Poling, Urbain, and Thompson, 1977;Smith, 1964).A number of factors may influence the rate of occurrence of a particular behavior. Rein-