IntroductionPhysiological variables are often scaled or normalized to account for differences in body size. The use of scaling is important in comparing individuals against a standard or to other individuals or groups differing in body size, investigating the longitudinal effects of growth, and examining relationships between physiological variables and performance.Traditionally, cardiac output (Q) and stroke volume (SV) have been scaled relative to body surface area (BSA [m 2 ], ratio scaling) to create size-independent variables (e.g., cardiac index [QI, l · min -1 · m -2 ] and stroke volume index [SVI, ml · beat -1 · m -2 ]). This form of scaling cardiovascular data has been used for nearly 75 years, with Grollman [6] reporting in 1929 that the resting Q of men and women was a function of their body surface area. The physiological appropriateness of ratio scaling of cardiovascular AbstractThis study investigated different methods of scaling submaximal cardiac output (Q) and stroke volume (SV) to best normalize for body size (body surface area [BSA], height [Ht], weight [Wt], and fat-free mass [FFM]). Q and SV were measured at both an absolute (50 W) and a relative power output (60 % of V O 2max ) in 337 men and 422 women, 17 to 65 years of age. Traditional ratio scaling was examined in addition to allometric scaling, where scaling exponents (b) were determined for each body size variable (x) that best normalized the physiological outcome variables (y) for body size (y = ax b ). With ratio scaling, regardless of the body size variable (x = BSA, Ht, Wt, FFM), there was no evidence of a linear relationship between x and y (y = Q or SV). A linear relationship is a necessary condition for appropriate normalization. Further, when ratio-scaled variables (e.g., Q/BSA) were correlated to the body size variable (e.g., BSA) by which they were scaled, significant (p ≤ 0.05) relationships still existed for BSA, Ht, Wt, and FFM. Thus, ratio scaling did not meet either criteria for normalizing Q and SV for body size. In contrast, when allometrically-derived scaling exponents were used to normalize Q and SV (e.g., Q/BSA b ), the resulting scaled values were uncorrelated (i.e., size-independent) with BSA, Ht, Wt, or FFM. These results were independent of age, sex or race. In summary, ratio scaling did not appropriately normalize Q and SV for differences in body size, while allometric scaling did result in size-independent values. Thus, individually-derived allometric exponents should be applied to body size variables to most appropriately adjust Q and SV for body size.

Rationale Deficits in memory and attention are broadly acknowledged during psychosis; however, experiments on modeled psychosis often test working memory without systematic manipulation of attentional demands. Objectives The major research goal was discovering which neurobehavioral processes, attention, or memory contributed more to drug-provoked performance deficits. Materials and methods Rats were trained to perform operant ratio discrimination (RD) tasks wherein the number of presses at a rear-wall lever was discriminated using one of two front-wall levers. Effects from four psychotomimetic drugs, the serotonin agonist 2,5-dimethoxy-4-iodoamphetamine, the noncompetitive NMDA-glutamate receptor antagonist phencyclidine (PCP), and two CB1-selective cannabinoid agonists, WIN 55,512-2 and AM 411, were assessed using a signal detection analytical overlay to dissociate cognitive from noncognitive motor and motivational disruptions. Further methods allowed dissociation of attention compromises from mnemonic deficits. Results For each test compound, at least one dose elicited decreased RD accuracy without affecting response rates, and task difficulty was shown to be a crucial dictator of accuracy effect specificities. Effects from both PCP and WIN 55,512-2 biased animals to select the response lever conditioned for denser reinforcement. The same two drugs rendered peculiar response patterns in distracter light session components, considering light blinks were included to divert subjects’ attention away from task-relevant information. The response patterns determined during distracter components of PCP/WIN testing sessions, counterintuitively, suggest performance enhancement. Conclusion Comprehensive viewing of RD performance patterns after drug administration indicates that sustained attention and transient information management are significantly impaired during the drug-induced psychosis state, while selective attention is less affected.

National survey data suggest a steady increase in the diagnosis and treatment of mental disorders in children, particularly Attention Deficit/Hyperactivity Disorder (ADHD). As nearly all children diagnosed with ADHD are prescribed stimulant drugs, rationale exists to quantitatively characterize behavioral responses following withdrawal from chronic stimulant dosing. These rodent experiments involved chronic administration of 7.5 mg/kg, s.c. amphetamine to subjects throughout adolescence followed by cognitive tests to gauge learning and performance during the withdrawal stage 7 to 14 days past withdrawal. Tests used a complex Stone 14-unit multiple T-maze, which is a robust paradigm for demonstrating age-related differences in rodent models when behavioral cognitive endpoints are used. Results reveal that amphetamine-treated subjects committed fewer major and retracing errors with increased minor errors and a significantly lower mean completion time. These findings suggest that pharmacotherapy aimed at adolescent-phase treatment of ADHD does not provoke spatial memory deficits at times proximal to drug withdrawal and lends support to amphetamine use in the treatment of ADHD children.

No abstract