Biomedical subjects

Merrill Hiscock

Publications and source records attributed to Merrill Hiscock.

7 recordsLinked to original sources

PubMed2006

Concurrent counting and typing: lateralized interference depends on a difference between the hands in motor skill.

In previous demonstrations of differences between left- and right-handers in dual-task performance, participants' hand preference has been confounded with asymmetry of manual skill. The present study was designed to disentangle those two factors as sources of lateralized interference in the concurrent-task paradigm. Forty-eight normal adults (24 females and 24 males) counted backward by ones or by twos while typing an easy or difficult sequence of letters with either hand. When participants were grouped according to self-reported hand preference, both groups showed bilaterally symmetric slowing, relative to single-task conditions. However, when the same participants were grouped according to manual asymmetry in the baseline condition, the cognitive task interfered significantly more with the faster hand than with the slower hand. Baseline typing rate, averaged across hands, did not influence dual-task interference. Both self-reported left-hand preference and left-hand superiority in baseline typing were associated with reduced interference on the cognitive task, and the reduced interference in those groups seemed to reflect relatively loose coupling between manual and cognitive tasks. The results support and extend Caroselli et al.'s (1997) findings regarding the effect of baseline manual asymmetry on the pattern of dual-task interference. Irrespective of the participant's hand preference, the presence or absence of baseline asymmetry may be sufficient to determine whether dual-task interference is lateralized.

Adolescent↗

PubMed2006

Dual-task interference in right- and left-handers: typical laterality patterns are obtained despite reversal of baseline asymmetries.

Lateralized interference between concurrent cognitive and manual activities is used to infer cerebral hemisphere specialization for the cognitive activity. However, some evidence indicates that lateralized interference depends largely on manual asymmetry in the single-task (baseline) condition. To test the competing explanations, we asked 40 right-handed (RH) and 40 left-handed (LH) adults to key press and calculate concurrently. Baseline manual asymmetries were manipulated by increasing the complexity of the task performed by the dominant hand. Nevertheless, in the dual-task conditions, RHs showed more overall interference when performing with the right hand and LHs showed a nonsignificant tendency in the opposite direction. The results indicate that differential interference patterns, similar to those previously reported for right- and left-handers, may be obtained even when the usual baseline manual asymmetries are reversed.

Analysis of Variance↗

PubMed2006

Neuropsychological function in adults with von Recklinghausen's neurofibromatosis.

The cognitive function of adults with von Recklinghausen's neurofibromatosis (NF-1) was examined. This study sought to replicate in an adult sample the findings of decreased visuospatial and attention abilities reported for many children with NF-1. Specifically, it was anticipated that adults with NF-1 would be classified separately from unaffected controls according to visual and attention-executive function skills. Second, this study examined whether language skills discriminated between adults with NF-1 and unaffected controls. The sample included 20 participants with NF-1 and 25 control participants. All participants were administered a battery of neuropsychological tests (Developmental Test of Visual-Motor Integration (VMI), Judgment of Line Orientation (JLO), Visual Form Discrimination, Booklet Category Test, Figure Cancellation, Peabody Picture Vocabulary Test-Revised (PPVT-R), Sentence Repetition, Controlled Oral Word Association). The results of a discriminant function analysis partially supported the hypothesis: Two of the tests of visual-spatial skill (VMI, JLO) and one of the language tests (PPVT-R) were found to be the best predictors for group membership. The discriminant function accounted for 45% of the variance between the groups and correctly classified 15 of the NF-1 participants and 21 of the control participants. Post hoc exploratory analyses revealed that the VMI was the most important test in discriminating between the groups. It is suggested that patients with NF-1 will tend to have sparing of basic cognitive functions but will have greater impairment on tests that use multiple cognitive skills.

Adult↗

PubMed2005

Constant and variable aspects of the dichotic listening right-ear advantage: a comparison of standard and signal detection tasks.

The study was designed to disentangle perceptual and attentional components of the dichotic listening right-ear advantage (REA). A total of 120 normal adults (108 right-handers and 12 left-handers) were administered the Halwes Fused Dichotic Words Test (FDWT) under standard conditions, which entail a forced-choice response format and no attention instructions. Two weeks later, the same stimuli were administered in a signal detection format with varied attention instructions (left, right, and equally divided). The standard task yielded the expected REA. The signal detection task yielded an REA for detection of targets that remained invariant across attention conditions. In contrast, ear asymmetry for localisation of targets varied with attention instructions. The REA on the standard task was correlated with the asymmetry of target detection (r = .57) on the signal detection task but not with the asymmetry of localisation or response bias. Ear asymmetry on the standard test seems to reflect an early stage of processing that is not altered by shifts of attention. Volitional shifts of attention influence the localisation of targets, but this component of signal processing is unrelated to the REA obtained on the standard test.

Adolescent↗

PubMed2004

Dual-task performance in early stage dementia: differential effects for automatized and effortful processing.

Attentional functions of individuals with early stage Alzheimer's disease (AD) and normal older adults (NC) were studied using a concurrent-task paradigm. Fourteen patients (5 men, 9 women) and 14 age- and sex-matched normal adults engaged in speeded unimanual tapping and speaking tasks during single- and dual-task trials. Speaking tasks were either relatively automatized (Speech Repetition) or relatively effortful (Speech Fluency). As single-task tapping rates were slower for the AD participants than for the NC participants, a proportional decrement score was used as an index of interference in the dual-task conditions. Interference during concurrent-task performance was greater when the cognitive task was effortful for both the NC and the AD groups. Although AD patients suffered higher levels of interference than NC participants while performing the effortful speech task, the two groups showed equivalent small changes in tapping speed while combining the automatized speaking and tapping tasks. Results suggest that a general-purpose attentional processing resource declines in the early stages of AD but dual-task performance is well-maintained when the component tasks are relatively automatized.

Activities of Daily Living↗

PubMed2002

Executive functions in children with frontal and temporal lobe epilepsy.

Even though frontal lobe epilepsy (FLE) is a relatively common seizure type, no formal psychometric studies of children with FLE have been reported. We compared 12 children with FLE and 15 children with temporal lobe epilepsy (TLE) on neuropsychological tests of attention, memory, executive functioning, and adaptive functioning. The results of these tests indicated that the children with FLE had deficits in planning and executive functions, whereas their verbal and nonverbal memory was intact. The opposite pattern was observed in children with TLE. Measures of executive functioning and impulse control were the best predictors of adaptive functioning. The findings suggest that children with FLE have a pattern of cognitive deficits that differs markedly from the pattern seen in children with TLE. Children with FLE have prominent deficits in executive functioning that appear to be related to poor behavioral adaptation.

Activities of Daily Living↗

PubMed2002

Raven's progressive matrices performance in adults with traumatic brain injury.

Raven's Progressive Matrices (RPM), a widely used test of reasoning, is sensitive to aging, but it has not proven to be helpful in the assessment of acquired focal or lateralized brain damage. Clinical experience suggests that the test is insensitive to traumatic brain injury (TBI), but the data are difficult to interpret because of rapid inflation of norms over time (the Flynn effect). In examining data from 64 adult patients with TBI who were administered the Standard RPM between 1981 and 1989, we used previous and subsequent norms conjointly to adjust for the Flynn effect. Anterograde and retrograde adjustment of norms led to highly convergent results. After adjustment for the Flynn effect, RPM performance was comparable to Wechsler IQ, significantly below estimated premorbid IQ, and nearly 2 SD above performance on 2 TBI-sensitive neuropsychological tests. We conclude that RPM performance is neither more nor less sensitive than Wechsler IQ to the consequences of TBI in the adult, but erroneous conclusions are likely to be reached if the Flynn effect is not taken into account.

Adolescent↗