Limits...
Intraindividual variability (IIV) in an animal model of ADHD - the Spontaneously Hypertensive Rat.

Perry GM, Sagvolden T, Faraone SV - Behav Brain Funct (2010)

Bottom Line: ADHD-affected individuals also have high intra-individual variability (IIV) in reaction time.We represented IIV as the average absolute deviation of individual behavior within the five 18-min segments of each experimental session from the average behavioral trait value within that session ('individual phenotypic dispersion', PDi).Some studies indicate the sharing of symptoms of hyperactivity and impulsiveness in SHR and ADHD-affected humans; high IIV in operant behavioral metrics suggests that the SHR may be useful in elucidating the genetic basis for IIV in humans.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medicine, SUNY Upstate Medical University, Syracuse, NY 13210, USA. perryg@upstate.edu

ABSTRACT
Attention-deficit/hyperactivity disorder (ADHD) is characterized by numerous behaviors including inattention, hyperactivity and impulsiveness. ADHD-affected individuals also have high intra-individual variability (IIV) in reaction time. The genetic control of IIV is not well understood. The single study of the genetics of this phenomenon in humans detected only marginal associations between genotypes at two candidate genes for ADHD and variability in response time. The Spontaneously Hypertensive Rat (SHR/NCrl) is an animal model of ADHD, expressing high activity, inattention and impulsive behavior during operant and task tests. The SHR might be useful for identifying genes for variability, but it is not known whether it also expresses high IIV, as is symptomatic of ADHD. We therefore conducted an investigation of IIV in the SHR. We used 16 SHR/NCrl rats and 15 Wistar-Kyoto (WKY/Nico) controls applying a reinforcement schedule used in the validation of the SHR as an animal model of ADHD. We represented IIV as the average absolute deviation of individual behavior within the five 18-min segments of each experimental session from the average behavioral trait value within that session ('individual phenotypic dispersion', PDi). PDi for hyperactivity, impulsiveness and inattention in the SHR and WKY rats was analyzed using nonparametric ranking by experimental session. SHR/NCrl rats had higher PDi than WKY/Nico controls for impulsiveness and inattention. There was a significant upward trend for PDi over experimental segments within sessions for attention in SHR rats, but not in WKY. PDi for hyperactivity was correlated with PDi for impulsiveness and we therefore excluded observations associated with short IRTs (< 0.67 s); dispersion in hyperactivity outside this interval was also significantly higher in SHR rats than in WKY rats. Some studies indicate the sharing of symptoms of hyperactivity and impulsiveness in SHR and ADHD-affected humans; high IIV in operant behavioral metrics suggests that the SHR may be useful in elucidating the genetic basis for IIV in humans.

Show MeSH

Related in: MedlinePlus

Histogram distributions of impulsive, inattentive and hyperactive behavior in 16 Spontaneously Hypertensive Rats (SHR) and 15 control Wistar-Kyoto (WKY) rats.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2959001&req=5

Figure 1: Histogram distributions of impulsive, inattentive and hyperactive behavior in 16 Spontaneously Hypertensive Rats (SHR) and 15 control Wistar-Kyoto (WKY) rats.

Mentions: Intra-individual variability (IIV) was measured as the average absolute deviation from mean individual operant behavior by session for each trait. Individual phenotypic dispersion (PDi) was calculated as the average of absolute differences between behavior in each segment within session and the average behavior for the entire session as , where is the operant behavior for rat i within segment j (from 1-5) and is the average behavior for the rat within the complete session. The distribution of PDi was strongly non-normal for all traits (Figure 1). Therefore, in order to avoid complications arising from violations of the normal distribution, we tested for differences in IIV between strains using Kruskal-Wallis nonparametric ranking of average PDi across all segments within each session, and general linear modeling [27] on average log-transformed PDi, so that one PDi value was available per individual per session. Behavioral means for each strain were estimated using general linear modeling of log-transformed PDi. Variance proportions for PDi were estimated from log-transformed averages across all sessions and segments [27]. To avoid confounding dispersion estimates for impulsiveness and hyperactivity by the inclusion of short IRTs in estimates of total activity, we excluded all activity measurements with IRT < 0.67 s in the estimation of PDi for hyperactivity.


Intraindividual variability (IIV) in an animal model of ADHD - the Spontaneously Hypertensive Rat.

Perry GM, Sagvolden T, Faraone SV - Behav Brain Funct (2010)

Histogram distributions of impulsive, inattentive and hyperactive behavior in 16 Spontaneously Hypertensive Rats (SHR) and 15 control Wistar-Kyoto (WKY) rats.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2959001&req=5

Figure 1: Histogram distributions of impulsive, inattentive and hyperactive behavior in 16 Spontaneously Hypertensive Rats (SHR) and 15 control Wistar-Kyoto (WKY) rats.
Mentions: Intra-individual variability (IIV) was measured as the average absolute deviation from mean individual operant behavior by session for each trait. Individual phenotypic dispersion (PDi) was calculated as the average of absolute differences between behavior in each segment within session and the average behavior for the entire session as , where is the operant behavior for rat i within segment j (from 1-5) and is the average behavior for the rat within the complete session. The distribution of PDi was strongly non-normal for all traits (Figure 1). Therefore, in order to avoid complications arising from violations of the normal distribution, we tested for differences in IIV between strains using Kruskal-Wallis nonparametric ranking of average PDi across all segments within each session, and general linear modeling [27] on average log-transformed PDi, so that one PDi value was available per individual per session. Behavioral means for each strain were estimated using general linear modeling of log-transformed PDi. Variance proportions for PDi were estimated from log-transformed averages across all sessions and segments [27]. To avoid confounding dispersion estimates for impulsiveness and hyperactivity by the inclusion of short IRTs in estimates of total activity, we excluded all activity measurements with IRT < 0.67 s in the estimation of PDi for hyperactivity.

Bottom Line: ADHD-affected individuals also have high intra-individual variability (IIV) in reaction time.We represented IIV as the average absolute deviation of individual behavior within the five 18-min segments of each experimental session from the average behavioral trait value within that session ('individual phenotypic dispersion', PDi).Some studies indicate the sharing of symptoms of hyperactivity and impulsiveness in SHR and ADHD-affected humans; high IIV in operant behavioral metrics suggests that the SHR may be useful in elucidating the genetic basis for IIV in humans.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medicine, SUNY Upstate Medical University, Syracuse, NY 13210, USA. perryg@upstate.edu

ABSTRACT
Attention-deficit/hyperactivity disorder (ADHD) is characterized by numerous behaviors including inattention, hyperactivity and impulsiveness. ADHD-affected individuals also have high intra-individual variability (IIV) in reaction time. The genetic control of IIV is not well understood. The single study of the genetics of this phenomenon in humans detected only marginal associations between genotypes at two candidate genes for ADHD and variability in response time. The Spontaneously Hypertensive Rat (SHR/NCrl) is an animal model of ADHD, expressing high activity, inattention and impulsive behavior during operant and task tests. The SHR might be useful for identifying genes for variability, but it is not known whether it also expresses high IIV, as is symptomatic of ADHD. We therefore conducted an investigation of IIV in the SHR. We used 16 SHR/NCrl rats and 15 Wistar-Kyoto (WKY/Nico) controls applying a reinforcement schedule used in the validation of the SHR as an animal model of ADHD. We represented IIV as the average absolute deviation of individual behavior within the five 18-min segments of each experimental session from the average behavioral trait value within that session ('individual phenotypic dispersion', PDi). PDi for hyperactivity, impulsiveness and inattention in the SHR and WKY rats was analyzed using nonparametric ranking by experimental session. SHR/NCrl rats had higher PDi than WKY/Nico controls for impulsiveness and inattention. There was a significant upward trend for PDi over experimental segments within sessions for attention in SHR rats, but not in WKY. PDi for hyperactivity was correlated with PDi for impulsiveness and we therefore excluded observations associated with short IRTs (< 0.67 s); dispersion in hyperactivity outside this interval was also significantly higher in SHR rats than in WKY rats. Some studies indicate the sharing of symptoms of hyperactivity and impulsiveness in SHR and ADHD-affected humans; high IIV in operant behavioral metrics suggests that the SHR may be useful in elucidating the genetic basis for IIV in humans.

Show MeSH
Related in: MedlinePlus