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Biomedical subjects

J Liederman

Publications and source records attributed to J Liederman.

30 records · Page 2Linked to original sources
PubMed1986

Determinants of the enhancement of the right visual field advantage by bilateral vs. unilateral stimuli.

Bilateral presentation of two different verbal inputs usually produces a stronger left hemispheric/right visual field (RVF) processing advantage than unilateral presentation. Previous reports of this effect confounded stimulus load with display configuration. Two experiments are presented in which the number of items during unilateral and bilateral trials was equated. The RVF advantage was enhanced during a free recall paradigm (Experiment I) but not during a partial report paradigm in which subjects were cued in advance to report only the top or the bottom of the display (Experiment II). This demonstrates that the effect does not depend upon the number of inputs per display and can not invariably be produced by bilateral/bihemispheric stimulation. It is suggested that subjects may be strongly biased to give priority to items delivered to the RVF/left hemisphere during bilateral trials. However, when this bias is constrained by rendering half of the RVF inputs irrelevant, subjects may be forced to pay equal attention to LVF inputs. Thus, eliminating the attentional bias eliminates the enhancement of the RVF advantage during bilateral trials.

Adolescent↗
PubMed1986

Handedness is not a unidimensional trait.

Most theories about the inheritance of hand preference assume that handedness is a unidimensional trait which forms a continuous distribution. This paper demonstrates that sampling a wide range of manual activities reveals dimensions of hand preference that are independent. 180 right handed and 110 left handed adults indicated their hand preference for 55 activities according to a five point scale. A Varimax Factor Analysis revealed four factors which accounted for 80 percent of the variance. Factor 3 was of special interest because it represented behaviors which rely upon the axial musculature and involve strength more than dexterity. Hand preference for items on this factor were less laterally biased than on factors which included such fine motor behaviors as writing or drawing. These results suggest that manual preference is governed by more than one neural system and that these systems may be independently lateralized.

Adolescent↗
PubMed1986

Words created by children versus aphasic adults: an analysis of their form and communicative effectiveness.

The creation of words through the novel combination of English morphemes (e.g., "map ball" to refer to a globe) was studied in 40 preschool children, 40 grade school children, and 40 adults. These lexical innovations were collected while subjects named pictured objects, and were evaluated in terms of incidence, communicative effectiveness, novelty, semantic accuracy, and certain linguistic characteristics. Preschool children's innovations were as communicatively effective as those of grade school children and adults and contained the highest proportion of innovations with redundant elements. Grade school children produced the highest proportion with semantic inaccuracies. This suggests that preschoolers invent words from a limited set of highly familiar terms, whereas grade schoolers rely more on partially known terms. In addition, the children's innovations differed significantly from those previously collected from aphasic adults. This demonstrates that aphasia does not cause a regression to an early level of linguistic sophistication.

Anomia↗
PubMed1986

Subtraction in addition to addition: dual task performance improves when tasks are presented to separate hemispheres.

This research links neuro- and cognitive psychology by asking whether performance of two concurrent cognitive tasks is facilitated by presentation of each task to a different cerebral hemisphere. Subjects were required to perform two arithmetic problems which were presented simultaneously. One problem required addition; the other subtraction. In Experiment I, briefly exposed numbers were exposed for 100 ms and were arranged so that a digit at fixation had to be added to a top number and subtracted from a bottom number. In Experiment II, the numbers were reversed so that the addition task was below the subtraction task. During Bilateral/bihemispheric trials, the addition problem was presented to one visual field and the subtraction problem to the other visual field. During Unilateral/single hemisphere trials, the addition and subtraction problems were projected to only one visual field. Results indicated that a higher proportion of problems were correctly solved during the Bilateral/bihemispheric trials than during the Unilateral/single hemisphere trials. These data suggest that dividing simultaneous inputs so that each hemisphere is confronted with a task requiring only one kind of cognitive operation facilitates performance, perhaps by minimizing intertask interference. This study illustrates one kind of hemispheric cooperation which facilitates dual task performance.

Cerebral Cortex↗
PubMed1986

Interhemispheric interference during word naming.

The hypothesis that the use of two hemispheres as receiving stations for information, rather than just one hemisphere, decreases interference between items, and improves performance, was tested by requiring subjects to identify four words simultaneously projected to one visual field (Unilateral-single hemisphere presentation) or divided between two visual fields (Bilateral-bihemispheric presentation.) In Experiment I, words projected to different hemispheres were incorrectly "blended" into a single response as frequently as words projected to a single hemisphere. In Experiment II, subjects were told that half of the display was irrelevant. Irrelevant words which were projected to a different hemisphere than the relevant words were incorrectly named as often as when all four words were projected to the same hemisphere. In addition, overall performance during Bilateral-bihemispheric presentations did not exceed that during the better of the two Unilateral-single hemisphere presentations, not only when naming was required (Experiments I and II), but even when only recognition was required (Experiment III). This demonstrates that division of inputs between the hemispheres does not always improve performance.

Eye Movements↗
PubMed1986

Independent dimensions of hand preference: reliability of the factor structure and the handedness inventory.

Healey, Liederman, and Geschwind (1986) suggested that handedness is not a unidimensional trait. They devised a questionnaire with 55 handedness items and 6 familial hand preference items and administered it to 290 adults. Their analysis identified four independent factors underlying hand preference. In the current study, the reliability of all but one of the items on the original inventory was established by retesting 83 of the original subjects. An additional analysis revealed that approximately 2% of the population could be considered to have "ambiguous" handedness in the sense that they indicated unstable hand preference according to the criteria suggested by Soper and Satz (1984). The reliability of the factor structure was evaluated by factor analyzing data from a new sample of 487 subjects, demographically similar to those in the original sample. All four factors reappeared with minor shifts in item loadings. The original and second samples were then combined, and four factors were again found, even when the sample was reconstructed so that there were equal numbers of males and females. On the basis of these new analyses our initial conclusion was confirmed: hand preference must be characterized along more than one dimension.

Journal Article↗
PubMed1985

Interhemispheric collaboration in response to simultaneous bilateral input.

Two experiments tested whether processing is speeded when inputs are divided between the hemispheres rather than projected to a single hemisphere. Bilateral (bihemispheric) vs unilateral (single hemisphere) word pairs were tachistoscopically presented. Subjects responded when the words semantically matched. Irrespective of distance, visual angle and compatibility with reading biases, bilateral/bihemispheric performance was as fast as the better of the two individual unilateral/single hemisphere conditions and faster than their average. This pattern occurred only at the beginning of each experiment. With practice, performance significantly improved in the single but not the bihemispheric conditions. The excellent initial performance during the bihemispheric condition and its lack of improvement with practice are discussed with reference to models of interhemispheric collaboration.

Adolescent↗
PubMed1985

Developmental changes in hemispheric independence.

In this research, we questioned whether children's relative inability to use the 2 cerebral hemispheres independently contributes toward their difficulty with the simultaneous execution of conflicting tasks. 2 naming tasks were simultaneously presented to either 1 visual field/hemisphere combination (unilateral) or were divided between visual fields/hemispheres (bilateral). We predicted that bilateral presentation would improve performance by insulating these conflicting tasks from mutual interference and that there would be a developmental shift in the size of the advantage for bilateral presentation. This hypothesis was confirmed in a sample of 120 children (N = 40 per group). Older children (12- and 14-year-olds) named more items when they were presented bilaterally, rather than unilaterally, when conflicting inputs were directed to different hemispheres. Younger children (10-year-olds) displayed no advantage for bilateral presentation regardless of whether conflicting tasks were projected to the same hemisphere or different hemispheres. The fact that 10-year-olds did not benefit from division of conflicting inputs between the hemispheres was interpreted as a symptom of their relative inability to use the hemispheres independently.

Adolescent↗
PubMed1983

Lexical creativity during instances of word-finding difficulty: Broca's vs. Wernicke's aphasia.

Lexical innovation--the creation of a word by combining existing morphemes in a novel way (e.g. "map ball" for "globe")--was evaluated as a method for circumventing word-finding difficulty in Broca's and Wernicke's aphasia. Aphasic groups were matched for naming performance and compared to a control group of normal adults matched for age and education. Lexical innovations were collected during the administration of a confrontation naming test, and were then analyzed in terms of the correctness of morpheme combination, semantic accuracy, novelty, and communicative effectiveness. An innovation was considered to be communicatively effective when its intended referent was understood by a naive judge. The lexical innovations of the two aphasic groups were diametrically opposed: as compared to both Broca's aphasics and normal adults, Wernicke's aphasics innovated significantly less often, and their innovations were significantly inferior in terms of: semantic precision, the proper construction of morpheme combination, and communicative effectiveness. This pattern suggests that lack of verbal fluency may be compatible with lexical creativity, while empty logorrheic speech may be an impediment to lexical creativity. Similarly, we conclude that the agrammatism of Broca's asphasia does not interfere with lexical innovation, while the paragrammatism of Wernicke's aphasia does interfere with lexical innovation, thus suggesting that paragrammatism affects morpheme combination at the word level as well as the sentence level.

Aphasia↗
PubMed1982

The origin of left hand preference: pathological and non-pathological influences.

Models of the origin of left hand preference were tested with prospective data. Infants with and without a history of perinatal complications, matched for age, sex and parental handedness, were filmed at 6 weeks of age. Children with a history of perinatal complications lacked the rightward headturning bias of those children without a history of perinatal trauma. Children with a history of perinatal complications were also deviant with reference to the duration of a postural reflex and its degree of lateralization. Perinatal complications may delay the establishment of volitional hand use as well as increase the probability of left-handedness. The data were interpreted as supporting SATZ's (Cortex 8, 121-135, 1972) rather than BAKAN et al.'s (Neuropsychologia 11, 363-366, 1973) model of "pathological" left-handedness.

Birth Injuries↗
PubMed1981

Right-hand preference facilitated by rightward turning biases during infancy.

A rightward turning bias is the earliest human asymmetry and may be a precursor of handedness. Head-turning affects arm position as part of the Asymmetric Tonic Neck Reflex (ATNR). The hypothesis was tested that turning biases operate in coordination with the ATNR to promote handedness by measuring reflex behavior during turns in the preferred vs nonpreferred direction. Twenty infants were filmed during spontaneous movement and during the following factorial design: head turned left vs right; voluntarily vs passively; 30 degrees vs 70 degrees. The incidence, strength, and duration of the ATNR were least when the child turned toward his/her preferred side. When right-preference children turned rightward, the occurrence of the ATNR was no better than chance. Thus, a child can orient toward the right hand with minimal intrusion of the ATNR upon limb position, perhaps promoting right-handedness.

Elbow Joint↗