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Biomedical subjects

T Humphries

Publications and source records attributed to T Humphries.

12 recordsLinked to original sources
PubMed1999

Effect of methylphenidate on attention in children with attention deficit hyperactivity disorder (ADHD): ERP evidence.

Methylphenidate is the most common treatment for attention deficit hyperactivity disorder (ADHD) and has been shown to improve attention and behaviour. However, the precise nature of methylphenidate on specific aspects of attention at different dose levels remains unclear. We studied methylphenidate effects in ADHD from a neurophysiological perspective, recording event-related potentials (ERPs) during attention task performance in normal controls and children with ADHD under different dose conditions. Twenty children with ADHD and 20 age matched controls were assessed with a continuous performance task requiring subjects to identify repeating alphabetic characters. ERPs and behavioural measures were recorded and analyzed for trials where a correct response was made. The ADHD group was assessed off drug (baseline) and on placebo, low (0.28 mg/kg) and high (0.56 mg/kg) dose levels of methylphenidate. The results showed that the ADHD group at baseline was more impulsive and inattentive than controls and had shorter P2 and N2 latencies and longer P3 latencies. Low dose methylphenidate was associated with reduced impulsivity (fewer false alarms) and decreased P3 latencies, whereas the higher dose level was associated with reduced impulsivity and less inattention (more hits), as well as increased P2 and N2 latencies and decreased P3 latencies. Amplitudes were unaffected and there were no adverse effects of the higher dose for any of the children. These results suggest differential dosage effects and a dissociation between dose levels and aspects of processing.

Attention↗
PubMed1998

Future value and patch choice in least chipmunks.

Animals subsisting on non-renewing patches confront a unique valuation problem, in which the objective value of a patch is inversely related to the amount already harvested. We investigated whether the subjective patch valuations of captive least chipmunks, Tamias minimus, reflected this environmental constraint as they foraged for buried patches of seeds. On the day following partial depletion of two patches, chipmunks spontaneously selected the least depleted patch, despite having no direct information about its former or present value. These findings held across experiments in which the order and extent of patch depletion were under the forager's control or experimental control. The animals consistently chose sites from which they had taken the fewest items, despite experiencing no difference in relative capture rate, suggesting that they discounted patch value on the basis of amount harvested or harvest time. Furthermore, the animals refused to return to patches they had completely depleted, and when induced to re-dig depleted patches by placing seeds above them, the animals chose randomly despite a three-fold difference in the number of items previously taken from each, suggesting that they disregarded rewards taken, attending only to the amount remaining. Subsequent experiments showed that chipmunks can take past reward history into account. When we refilled previously depleted patches and induced chipmunks to re-dig and deplete them again, they treated the patches as renewable types and represented their value in terms of the amount removed, not the amount left. Thus, the assessment mechanism of least chipmunks is facultative: they expect that patches will not replenish, but are prepared for exceptions. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

Tissue-specific methylation differences and cognitive function in fragile X premutation females.

Tissue-specific variation in (CGG)n repeat size and methylation status of the FMR1 gene was investigated in 17 female premutation carriers. Minor variation in premutation repeat size among leukocyte, lymphoblast, and fibroblast tissues was noted in some subjects. One subject exhibited a premutation size allele of (CGG)64 in leukocyte and fibroblast tissues by polymerase chain reaction analysis but a normal-size allele of (CGG)46 in lymphoblast cells, suggesting low-level mosaicism in blood and clonality of the lymphoblast cell line. Six subjects exhibited differences in methylation pattern between leukocytes and lymphoblasts but not between leukocytes and fibroblasts, whereas 2 subjects showed large differences in methylation pattern between leukocytes and fibroblasts. Cognitive function was studied in 14 subjects using the Wechsler Adult Intelligence Scale-Revised. Mean Verbal and Performance IQs were well within the average range as was the mean Full Scale IQ; nevertheless, a trend toward lower Performance IQ compared with Verbal IQ was observed. No significant correlation was apparent between Full Scale IQ and (CGG)n repeat size; however, a significant positive correlation was observed between Full Scale IQ and the proportion of the active X carrying the normal FMR1 allele in fibroblasts but not in leukocytes or lymphoblasts.

Adult↗
PubMed1996

Methylphenidate slows right hemisphere processing in children with attention-deficit/hyperactivity disorder.

To examine the effects and particularly, any potential detrimental effects of methylphenidate on right hemisphere processing in children with attention-deficit/hyperactivity disorder (ADHD), the performance of 26 children (aged 8-15 years) with ADHD was compared under methylphenidate and placebo on various cognitive tasks in a double-blind within-subjects design. Results indicated that reaction times on a tachistoscopic task were slower on methylphenidate for stimuli that produced a left visual field advantage (reflecting better right hemisphere functioning) but not for stimuli that produced a right visual field advantage (reflecting better left hemisphere functioning) or for bilateral stimuli. It is argued that methylphenidate induces a slower response on tasks involving right hemisphere processing, resulting in slower reaction times and unchanged accuracy rates. Findings on two tasks that more closely reflect classroom-type tasks revealed an improvement in performance on methylphenidate, suggesting that any stimulant-induced benefits on learning style may have overcome detrimental effects on unilateral processing. These findings may help understand the complex, diverse, and sometimes unpredictable effects of psychostimulants on cognitive functioning that are observed clinically in individuals treated for ADHD.

Adolescent↗
PubMed1996

Evidence of nonverbal learning disability among learning disabled boys with sensory integrative dysfunction.

The presumed sensorimotor basis of the nonverbal learning disability syndrome was investigated among 90 learning disabled boys (M age = 6 yr., 8 mo., SD = 12.2 mo.) with sensory integrative dysfunction. The majority of the boys were Caucasian, lower to middle socioeconomic status, and from urban, English-speaking families. 14% (n = 13) of the boys satisfied core discrepancy criteria for nonverbal learning disability, including both a significantly higher Wechsler Verbal than Performance IQ and a higher standard score in Reading than Arithmetic on the Wide Range Achievement Test. Compared with a control group of 19 boys from the same sample who had no significant discrepancies, boys with nonverbal learning disability had significantly greater weaknesses in space visualization and visuomotor coordination. As predicted, rote verbal memory and syntactical strengths were also exhibited by boys with nonverbal learning disability, but the two groups did not differ significantly.

Child↗
PubMed1994

Teacher-identified oral language difficulties among boys with attention problems.

Teachers evaluated the language functioning of 95 boys, aged 6.5 to 13.8 years, identified as having attention problems (AP, n = 30), learning disability (LD, n = 33), or average achievement (AA, n = 32). The three groups did not differ significantly (p > .05) in their frequency of articulation problems. Significantly (p < .05) more AP boys were rated as having pragmatics problems than both of the other groups. AP boys were also viewed as having a higher frequency of receptive/expressive language problems than were AA boys, but not compared with LD boys. LD and AA boys did not differ in their ratings for pragmatics problems, but more LD than AA boys were perceived as having receptive/expressive problems. The average incidence of all types of language problems was highest for the AP boys at 42% with poor pragmatics representing their most frequently rated language difficulty. AP boys' pragmatics difficulties seemed to be characterized by greater difficulty in maintaining than initiating a conversation compared with the other two groups. This difficulty was positively associated with the teachers' ratings of the AP boys' impulsivity.

Adolescent↗
PubMed1993

Use of IQ criteria for evaluating the uniqueness of the learning disability profile.

Beyond predetermined Performance Scale differences, a group of 24 children with learning disabilities having a lower Verbal, higher Performance IQ profile on the WISC-R and 33 slow learners were not found to be otherwise distinguished by their individual WISC-R subtest scores or subtest scatter. The majority of children were males, white, of lower to middle socioeconomic status and ranged in age from 6 to 13 years.

Adolescent↗
PubMed1992

A comparison of the effectiveness of sensory integrative therapy and perceptual-motor training in treating children with learning disabilities.

This study compared the effect of sensory integration therapy (SI), perceptual-motor training (PM) and no treatment (NT) on the performance of 103 children with learning disabilities and sensory integrative dysfunction, aged 58 to 107 months, who were randomly assigned to one of the two treatment groups or to no treatment. After receiving a total of 72 1-hour sessions of therapy for 3 hours per week, PM-treated subjects showed significant gains over the other two groups, primarily in gross motor performance. SI-treated subjects showed an advantage in motor planning. There were no accompanying group differences in visual perception, handwriting readiness, copying ability, cognitive, academic, language and attentional skills or in self-concept. These findings demonstrate motor gains resulting from motor treatments without carry-over to functional skills and abilities more directly associated with school performance.

Attention↗
PubMed1991

Attention deficit hyperactivity disorder: does cognitive behavioral therapy improve home behavior?

This study evaluates the effectiveness of cognitive behavioral therapy (CBT) in improving the home behavior of children with attention deficit hyperactivity disorder (ADHD). Twenty-five boys (age 7 to 13) with a diagnosis of ADHD were randomized to a CBT or supportive therapy control group. Outcome measures included parent and teacher ratings of the child on the Behavior Problem Checklist-Attention Problem Subscale (BPC-AP), and the Self-Control Rating Scale (SCRS), parent ratings on the Modified Werry Weiss Activity Scale, and child ratings on the Piers Harris Self-Concept Scale and Matching Familiar Figures Task. Data were analyzed using a two-way analysis of variance for main effects. A significant improvement favoring CBT was found on the Werry Weiss Scale, which measures the parent's perception of the child's hyperactivity in the home, and the child's rating of his/her self-esteem on the Piers Harris Self-Concept Scale. Other outcome measures did not demonstrate statistical differences. This research provides support for the use of CBT in children with ADHD. CBT was found to improve the parent's perception of the child's hyperactivity in the home as well as the child's self-esteem.

Adolescent↗
PubMed1983

A categorical analysis of the social attributions of learning-disabled children.

The social attributions of learning-disabled and control children with either similar or higher social acceptance ratings were assessed within an open-ended interview format. In addition, measures of social self-esteem and expectation of social success were obtained. The learning-disabled group used luck more frequently and personality interaction less frequently as explanations for social outcomes than did the other two groups. Learning-disabled children also had the lowest expectation of social success and, like the low acceptance group, had a poorer social self-image. Possible explanations for the development of these attributions and the implications for holding them were discussed.

Child↗
PubMedDate not supplied

Mediators of the risk for problem behavior in children with language learning disabilities.

A developmental-organizational perspective was employed to explore underlying risk for problem behavior in children with language learning disabilities. The independent and relative influences of social discourse and social skills on problem behavior were examined in 50 children with language learning disabilities (LLD) and 50 control children (children without LLD) aged 8 to 12 years. Hierarchical regression analyses revealed that when examined independently, both impaired social discourse skill and poor social skills accounted for the negative effect of LLD status on children's problem behavior. When social discourse and social skills were examined simultaneously in relation to problem behavior, social discourse no longer retained its predictive value. This result suggests that children's impaired social interactional functioning is central to the development of behavioral symptomatology. However, the importance of social discourse cannot be overlooked, given the significant correlation between social discourse and social skills ratings. Though these results are correlational in nature, it is argued that the impaired communicative competence of some children with LLD may contribute to poor social skills that ultimately manifest themselves as more clinical problem behaviors characterized by internalizing and externalizing symptomatology. Finally, differences were confirmed in social discourse performance, social skills, and problem behaviors between the children with LLD and the control group children. Findings emphasize the importance of the routine assessment and monitoring of broader social discourse skills, in addition to social competence, in children with LLD.

Child↗