Biomedical subjects

M Hiscock

Publications and source records attributed to M Hiscock.

At least 19 recordsLinked to original sources

PubMed2001

Attention processes in children with shunted hydrocephalus versus attention deficit-hyperactivity disorder.

Children with congenital hydrocephalus, children with attention deficit-hyperactivity disorder, and normal controls were evaluated with measures of focused attention (Visual Orienting and Detection Task), sustained attention (continuous performance test), and attention shifting (Wisconsin Card Sorting Test). Components from these tasks have been linked to attention systems mediated by anterior or posterior brain networks. Children with congenital hydrocephalus showed an inability to focus and shift attention, which specifically implicated impairment of the disengage and move components of the posterior brain attention system. Children with attention deficit-hyperactivity disorder displayed the expected performance patterns on measures of focused attention once their difficulties with sustained attention were taken into account. However, they showed problems with shifting and sustaining attention, which are commonly associated with the anterior brain attention system.

Achievement↗

PubMed2001

Is there a sex difference in human laterality? IV. An exhaustive survey of dual-task interference studies from six neuropsychology journals.

The entire contents of six neuropsychology journals (161 volumes, 612 issues) were screened to identify dual-task laterality experiments. Of 112 experiments thus identified, 45.5% provided information about sex differences. Although 23 experiments yielded at least one significant main effect or interaction involving the sex factor, only 5 outcomes represented an unambiguous sex difference in laterality. All 5 of those sex differences support the hypothesis of greater hemispheric specialization in males. The confirmatory outcomes constitute less than 10% of the informative experiments and less than 5% of the total population of experiments. These data alone do not rule out the possibility that sex differences are chance findings (Type I errors). However, when considered along with similar results from perceptual laterality data previously examined, the dual-task data fit the pattern of a small but reliable population-level sex difference in human laterality.

Adult↗

PubMed2001

Performance on paced serial addition tasks indicates an associative network for calculation.

Although paced serial addition (PSA) tasks are considered to be tests of general information-processing capacity, recent work suggests that performance on such tasks is influenced by arithmetic-specific variables. We designed two visual PSA experiments to determine whether the performance of normal adults would support predictions derived from the cognitive psychology of calculation. Experiment 1 showed that mixing familiar (Arabic numeral) and less familiar (Roman numeral) stimulus formats reduced scores below the averaged scores for pure Arabic and Roman lists. The Roman-Arabic order of addends was more difficult than the Arabic-Roman order. Experiment 2, which involved only Arabic numerals as addends, showed that performance could be impaired by constraining the trial-to-trial variability of sums. The results of both experiments confirm the importance of arithmetic-specific variables in PSA and provide support for an associative network model of calculation. In addition, the findings implicate interference from extraneous addends and responses as the performance-limiting factor.

Adult↗

PubMed2000

Selective attention fails to alter the dichotic listening lag effect: evidence that the lag effect is preattentional.

Berlin et al. (1973) reported that either stimulus from a dichotic pair of consonant-vowel syllables is processed preferentially when its presentation is delayed by 30-60 ms. In the first of three experiments with 60 normal right-handed adults, we replicated the Berlin et al. "lag effect," but only for asynchronies between 60 and 90 ms. In Experiment 2 subjects focused attention selectively on one ear. The results indicated that focused attention and stimulus asynchrony have additive effects: Performance improved at the attended ear irrespective of stimulus asynchrony, but the lag effect remained unchanged relative to the divided-attention condition. Experiment 3 entailed a signal detection task that allowed separate analysis of detection and localization accuracy. As in previous studies, selective attention to one ear increased the accuracy of localization but not detection at the attended ear. Both dependent measures indicated a lag effect that remained invariant as attention was manipulated. These findings imply that the lag effect is attributable to a preattentional stage of auditory processing.

Adult↗

PubMed2000

Toward solving the inferential problem in laterality research: effects of increased reliability on the validity of the dichotic listening right-ear advantage.

As noted by Satz, the prevalence of lateralized language in the general population is underestimated substantially by the proportion of people who show the typical asymmetry on a laterality task. In a series of two dichotic listening experiments with a total of 171 right-handers and 170 left-handers, we tested the hypothesis that increased reliability of measurement will lead to increased classification accuracy. Experiment 1 showed that neither the frequency nor magnitude of the right-ear advantage (REA) for fused rhyming words increased as the number of trials increased from 120 to 480. Ear-difference scores were highly reliable (r = .85), even when based on 120 trials. Experiment 2, which involved lists of dichotic word pairs, yielded similar results. Even though retest reliability of the ear-difference score for 132 word pairs was only .45, neither the incidence nor strength of the REA increased significantly when the number of pairs was increased to 528. The results indicate that the poor classification accuracy of dichotic listening tasks cannot be attributed to unreliability.

Acoustic Stimulation↗

PubMed1999

Allocation of attention in dichotic listening: differential effects on the detection and localization of signals.

In 2 dichotic listening experiments, 96 normal right-handed adults attended selectively to the left and right ear and divided their attention equally between both ears. Participants listened for specified targets and reported the ear of entry. The material consisted of pairs of consonant-vowel syllables in Experiment 1 and pairs of rhyming consonant-vowel-consonant words in Experiment 2. Both experiments yielded a right-ear advantage for detection and for localization. Attention instructions had no effect on detection. However, focusing attention on 1 ear increased the number of targets attributed to that ear while decreasing the number of targets attributed to the opposite ear. The dissociation between detection and localization indicates that volitional shifts of attention influence late (response selection) processes rather than early (stimulus identification) processes. Selective-listening effects can be accounted for by a 2-stage model in which a fixed input asymmetry is modulated by a biased selection of responses.

Adolescent↗

PubMed1999

Is there a sex difference in human laterality? III. An exhaustive survey of tactile laterality studies from six neuropsychology journals.

The contents of six neuropsychology journals (161 volumes, 612 issues) were screened to identify tactile laterality experiments. Of 73 experiments identified, 40% provided information about sex differences. Seventeen experiments yielded a total of 18 sex differences, of which 4 could be interpreted in terms of the hypothesis that functional cerebral lateralization is more pronounced in males. All 4 interpretable outcomes (constituting 5.5% of the population of experiments and 13.8% of the informative experiments) were found to be consistent with the differential lateralization hypothesis. The results, in isolation, do not justify rejecting the null hypothesis. However, when considered in conjunction with findings for auditory and visual laterality studies, the present results are compatible with a weak population-level sex difference.

Adult↗

PubMed1999

The roles of location specificity and masking mechanisms in the attentional blink.

In a series of four experiments using rapid serial visual presentations of two target letters embedded in numeral distractors, with different numbers of display positions and with or without masking, we show that (1) the nonmonotonic, U-shaped attentional blink (AB) function, which occurs when all items are presented at the same display location, is eliminated in favor of a monotonic function when targets and distractors are presented randomly dispersed over four or nine adjacent positions; (2) the AB monotonicity is maintained with the spatially distributed presentation even when backward masks are used in all possible stimulus positions and when the location of the next item in sequence is predictable; and (3) the U-shaped AB is not due to position-specific forward or backward masking effects occurring at early levels of visual processing. We tentatively conclude that the U-shaped AB is primarily a function of the interruption of late visual processing produced when the item following the first target occurs at the same location. In order for the AB to severely disrupt performance, the item following the first target must be presented at the same location as the target so that it can serve both as a distractor and as a mask interrupting of interfering with subsequent visual processing.

Adult↗

PubMed1999

Allocation of attention in dichotic listening: effects on the detection and localization of targets within lists.

In each of two dichotic listening experiments, 48 normal right-handed adults were instructed to attend selectively to the left and right ears and to divide attention equally between ears. Participants listened for specified targets and reported the ear of entry when the target was heard. Stimuli consisted of lists of digit names in Experiment I and lists of words in Experiment 2. Shifts of attention altered ear asymmetry for localizing but not for detecting digit names. For words, attention shifts altered both detection asymmetry and localization asymmetry, but the effect of attention on detection seemed to reflect differential retrieval from short-term memory rather than differential perception. In both experiments, shifting attention toward either ear resulted in a reporting bias such that signals were attributed to the attended ear more often than to the unattended ear. The results confirm our previous findings, for single pairs of stimuli, that volitional shifts of attention alter response selection rather than perception.

Adolescent↗

PubMed1998

Ear advantage in dichotic listening after correction for early congenital hearing loss.

Twelve patients who had undergone surgical correction for either unilateral or bilateral congenital hearing loss were given a postoperative dichotic listening test for consonant vowel-consonant (CVC) words. Four normal hearing control subjects were also tested. Patients were first given a test of subjective loudness, and the level of presentation of stimuli in the atretic ear was adjusted accordingly. In the dichotic condition all controls exhibited a right ear advantage, and all unilateral atresia patients showed an ear advantage favouring the non-atretic ear. Patients with bilateral atresia essentially exhibited no ear advantage. Patients had the same error rate as controls in the dichotic condition, which suggests that ear advantage was not due to increased errors in the atretic ear. For patients there was a significant relationship between ear advantage and both preoperative interaural asymmetry in hearing loss and age at operation. Results suggest that a sensitive and critical period for development of the ear is complete by 5 years of age. Results also suggest some limited ability to adjust to permanent change in stimulation levels until, but not after, puberty.

Adolescent↗

PubMed1998

Paced serial addition: modality-specific and arithmetic-specific factors.

Tests of paced serial addition are used to detect diminished information-processing capacity. Nonetheless, performance might be influenced by modality-specific interference or by variables that specifically affect numerical processing. In a series of three experiments with normal adults, we manipulated, respectively, the modality in which addends were presented, the modality in which responses were produced, and the format in which visual addends were displayed. Performance was enhanced when stimuli were presented visually and when responses were made manually. When visual addends were used, Arabic numerals were processed more effectively than number words. Thus, performance was influenced by modality-specific interference and by presentation format. We conclude that paced serial addition tasks may not provide a pure measure of general information-processing capacity.

Acoustic Stimulation↗

PubMed1997

Asymmetric interference between concurrent tasks: an evaluation of competing explanatory models.

According to Kinsbourne's functional cerebral distance model, asymmetric interference between concurrent cognitive and manual tasks reflects the functional specialization of the cerebral hemispheres. However, alternative explanations include initial-values artifact (statistical bias model), motor asymmetry (manual dominance model), and a combination of functional cerebral distance and manual dominance (two-factor model). We evaluated the competing models in four experiments with right- and left-handed university students for whom manual dominance was in effect reversed by requiring the dominant hand to perform the more difficult manual task. The cognitive load of the nonmanual task was varied within each experiment. The results did not support any of the models but, instead, reflected only tradeoffs between manual and nonmanual performance. The primary implications for future research are that performance on both tasks must be measured, and each task must be sensitive to interference from the other task, if observed asymmetries are to be interpretable.

Adult↗

PubMed1997

Webster's scattergram method: usefulness for assessing the asymmetry of interference between concurrent tasks.

Webster (1988) described a means of using scattergrams to represent the manual and nonmanual data from dual-task laterality experiments in a composite analysis. We used Webster's method and the conventional approach (i.e., separate analyses) to analyze the results of an experiment in which 40 right-handed adults performed a verbal and a manual task concurrently. Whereas separate analyses yielded dissimilar outcomes for the two tasks, the scattergram analysis showed that overall interference was greater when the right hand performed the manual task than when the left hand performed the manual task. Advantages of the scattergram method for analyzing dual-task data are discussed.

Adult↗

PubMed1997

Adaptive and maladaptive utilization of color cues by patients with mild to moderate Alzheimer's disease.

The ability to utilize color information was investigated in 12 patients with mild to moderate probable Alzheimer's Disease (DAT) and in 12 age- and gender-matched control subjects. All subjects underwent testing of visual acuity and color vision before being tested with a cognitive task consisting of four conditions (no color, color as attention enhancer, color as valid cue, color as distracter). Although the groups did not differ in visual acuity or color vision, patients with DAT were less accurate than controls in all four conditions of the cognitive task. Both groups performed best with color as a valid cue and worst with color as distracter, but condition had a significantly stronger effect on patients than on controls. It is concluded that color is a potent stimulus attribute for patients with DAT.

Journal Article↗

PubMed1996

Shifts in children's ear asymmetry during verbal and nonverbal auditory-visual association tasks: a "virtual stimulus" effect.

Dichotic consonant-vowel-consonant (CVC) syllables were presented to 96 right-handed children between the ages of 8 and 12 years. Children were assigned either to a "code" condition that entailed translating the CVCs into English words or to a "bird" condition in which the CVCs had to be matched to cartoons of birds. A differential ear asymmetry for the code and bird tasks developed linearly across four blocks of trials. By Block 4, the code task yielded a significant right-ear advantage and the bird task yielded no ear advantage. The results are inconsistent with any model that attributes ear asymmetries entirely to fixed structural characteristics of the nervous system. Instead, ear asymmetries are influenced by the subject's categorization of the stimuli, i.e., by "virtual stimuli". These appear to be constructed over time (blocks of trials).

Association Learning↗

PubMed1995

Dual-task interference patterns reveal differential processing of upright and inverted faces.

The concurrent-task method was used to investigate the hemispheric locus of face encoding. In each of three experiments, 48 right-handed adults performed unimanual finger tapping while encoding whole or partial faces for subsequent recognition. Faces were upright in Experiments 1 and 2 but inverted in Experiment 3. Irrespective of stimulus orientation, face encoding disrupted left- and right-hand tapping equally. Upright faces were less accurately recognized if learned during left-hand tapping than during right-hand tapping; inverted faces showed no lateralized interference. The results support tachistoscopic findings that indicate predominantly right-hemispheric processing of upright faces and bilateral processing of inverted faces.

Adolescent↗

PubMed1995

Asymmetry of verbal-manual interference: dissociation between rate and variability in left-handers.

In two experiments, 48 right-handed and 48 left-handed adults, respectively, performed speeded and consistent finger tapping with and without concurrent oral reading. Interference was measured in terms of change in tap-to-tap rate and variability. Experiment 1 confirmed a previous report that concurrent reading decreases the rate of speeded finger tapping and increases the rate of consistent tapping in right-handers, and that the right hand is affected more than the left. Experiment 2 showed that, for left-handers, concurrent reading decreases the rate of left-hand tapping more than right-hand tapping but increases the variability of the right hand more than the left. The double dissociation in left-handers between hand and dependent variable suggests that the speed and variability reflect different mechanisms of intertask interference. More generally, the findings illustrate the multidimensionality of motor performance and the risk of making inferences about neural organization on the basis of a single dependent measure.

Adolescent↗

PubMed1995

Assessment of anxiety in hospital patients.

There has been research in North America to validate the nursing diagnosis of anxiety. As part of this work, Young used the defining characteristics and developed a tool to measure anxiety. The present research sought to extend that study in the United Kingdom, assess the anxiety-defining characteristics tool and identify key indicators of anxiety that might be useful in clinical practice. Four anxiety measurement tools, drawn from the literature, were used. These were the state trait anxiety inventory, the graphic anxiety scale, the hospital anxiety and depression scale, and the anxiety-defining characteristics tool. A random sample of 79 hospitalized patients were interviewed and their anxiety rated using all four measures. Calculation of Spearman's correlation co-efficients revealed convergent validity between the anxiety-defining characteristics tool and the state trait anxiety inventory and the anxiety score on the hospital anxiety and depression scale. Anxiety levels were found not to be affected by the age or sex of the respondent, or the length of stay or number of previous admissions. Discriminant analysis suggested that six characteristics adequately discriminated anxious subjects: sweating, faintness, tendency to blame others, continual review of things in their mind, focus on self and a lack of self-confidence. The study concluded that there is a scope for further research into these characteristics and their use in clinical practice.

Adult↗