Biomedical subjects

M P Bryden

Publications and source records attributed to M P Bryden.

At least 19 recordsLinked to original sources

PubMed1992

Orienting of auditory spatial attention: effects of a lateralized tone cue.

Mondor and Bryden [8] (Neuropsychologia 29, 1179-1190, 1991) reported that the normal Right Ear Advantage for the identification of verbal material presented dichotically could be largely eliminated if subjects were cued to attend to and report from only one ear on each trial. In these experiments, the ear to be attended was cued by presentation of a tone to that ear only prior to each dichotic trial. The present series of studies were undertaken to determine whether this lateralized tone cue exerted its effect by orienting attention or by alerting the subject of the forthcoming trial. Results revealed that for both the right and left ears the facilitating effect of the cue was dependent on the accuracy of the location information it conveyed. Thus, the precueing technique originally employed by Mondor and Bryden as a means of controlling the contribution of attention to ear advantages was validated. It is concluded that the precueing technique provides a powerful means for specification of the extent to which attentional factors and hemispheric functional capabilities contribute to ear asymmetries.

Acoustic Stimulation↗

PubMed1992

Manipulations of subjects' level of arousal in dichotic listening.

The effects of manipulation of the subject's level of arousal on the right ear advantage (REA) in dichotic listening to CV-syllables were investigated. There were three different arousal manipulations under high and low incentive levels. Negative manipulations involved threat of electric shock (high incentive) or noise (low incentive) for incorrect answers. Positive manipulations involved the possibility to earn a substantial (high incentive) or small (low incentive) sum of money for correct answers. A third, neutral, condition involved no specific instructions about consequences for correct or incorrect answers. Thirty-six females participated in the study. Heart rate was recorded as an independent measure of change in level of arousal as a function of the experimental instructions. The results showed that the high negative condition abolished the REA effect, with a non-significant difference between ears. This was caused by both an increase in correct left ear reports and a decrease in correct right ear reports. The other arousal conditions had no effect on the REA. The results are discussed in terms of right hemisphere dominance for aversive emotional processing in dichotic listening.

Acoustic Stimulation↗

PubMed1992

On the relation between visual spatial attention and visual field asymmetries.

In the typical visual laterality experiment, words and letters are more rapidly and accurately identified in the right visual field than in the left. However, while such studies usually control fixation, the deployment of visual attention is rarely restricted. The present studies investigated the influence of visual attention on the visual field asymmetries normally observed in single-letter identification and lexical decision tasks. Attention was controlled using a peripheral cue that provided advance knowledge of the location of the forthcoming stimulus. The time period between the onset of the cue and the onset of the stimulus (Stimulus Onset Asynchrony--SOA) was varied, such that the time available for attention to focus upon the location was controlled. At short SOAs a right visual field advantage for identifying single letters and for making lexical decisions was apparent. However, at longer SOAs letters and words presented in the two visual fields were identified equally well. It is concluded that visual field advantages arise from an interaction of attentional and structural factors and that the attentional component in visual field asymmetries must be controlled in order to approximate more closely a true assessment of the relative functional capabilities of the right and left cerebral hemispheres.

Attention↗

PubMed1992

On the relation between auditory spatial attention and auditory perceptual asymmetries.

Laterality investigators have typically interpreted any perceptual asymmetry as a direct expression of the functional organization of the brain. However, many other confounding factors, including the asymmetric distribution of attention, may also contribute to either the magnitude or the direction of any of these advantages. In two experiments, attention was manipulated in a dichotic listening paradigm by presenting a preexposural tone cue to the ear from which the subject was required to report. The time available to orient attention was manipulated by varying the time period between the onset of the cue and the onset of the trial (stimulus onset asynchrony, or SOA). Results indicated that a right ear advantage for the identification of verbal material obtained at a 150-msec SOA was almost completely eliminated at an SOA of 450 msec. In addition, the direction of the ear advantage for emotion identification was found to depend on task difficulty. A left ear advantage, apparent when task difficulty was minimal, was reversed to a right ear advantage when difficulty was increased. These data are taken as evidence that, when subjects are faced with a difficult dichotic task, there is a general tendency for right-handed subjects to bias their attention toward the right ear. Such a tendency is shown not only to have likely seriously compromised the results of past investigations of functional perceptual asymmetries but also to be inconsistent with previously proposed theories of dichotic listening performance.

Adult↗

PubMed1991

The influence of attention on the dichotic REA.

Laterality researchers have frequently neglected to control for possible attentional components of perceptual asymmetries. Attention was manipulated in a dichotic listening paradigm by presenting a pre-exposural tone cue to the ear from which the subject was required to report. The time period between the onset of the cue and the onset of the trial (Stimulus Onset Asynchrony--SOA) was varied such that the time available to orient attention was manipulated. In two experiments, sizeable REAs were apparent at the shortest SOA (150 msec) but were substantially attenuated at longer intervals (450 and 750 msec SOA). In addition, a much larger effect of SOA on left-ear than on right-ear performance was observed. These effects were taken as evidence of an attentional bias to the right ear in the typical dichotic listening situation.

Adult↗

PubMed1991

Handedness is not related to self-reported disease incidence.

A hand preference inventory and a disease questionnaire were administered to a sample of 743 undergraduate students. The incidence of left-handedness was not related to the report of any of the diseases surveyed. Among right-handers, preference scores were slightly lower (less right-handed) in those reporting drug allergies or migraine. These data provide no support for the argument that handedness and immune disorders are related.

Adult↗

PubMed1991

Handedness effects in the detection of dichotically-presented words and emotions.

Left-handed and right-handed subjects were given two dichotic listening tasks using identical material. In one task, they were asked to determine whether or not a specific target word was present (verbal task). In the other task, subjects were asked to indicate whether or not one of the dichotically-competing words was spoken in a particular affective tone (emotion task). Overall, a right-ear advantage (REA) was found with the verbal task and a left-ear advantage (LEA) with the emotion task. Left-handers showed a slightly smaller REA than right-handers on the verbal task, but a slightly larger LEA on the emotion task. This finding suggests that left- and right-hemispheric functions are not related in a complementary fashion and that handedness effects for nonverbal tasks are different from those seen with verbal tasks. The emotional LEA was much larger for angry stimuli than for happy, sad, or neutral stimuli. Rather than providing evidence for a hemisphere by affective valence interaction, such results suggest a stimulus-specific effect.

Adult↗

PubMed1991

Geschwind's theory of cerebral lateralization: developing a formal, causal model.

Geschwind and Galaburda (1987) have proposed a complex and influential model of cerebral lateralization that is based on the argument that increased fetal testosterone levels modify neural development, immune development, and neural crest development. The theory can explain many aspects of cerebral lateralization and its relation to learning disorders, giftedness, and immune deficits. This article clarifies the structure of the theory by presenting it as a causal-path model. The internal coherence of the model is then evaluated by assessing the central concept of anomalous dominance, the role of timing in the articulation of the model, and the invocation of nonlinear processes. Finally, the article considers the problems implicit in testing a "grand" theoretical model and derives some principles for assessing the testability of various predictions, given the practical constraints of sample size and the problems of measurement error.

Autoimmune Diseases↗

PubMed1991

Attentional factors in visual field asymmetries.

Over the past 30 years, numerous studies have reported left/right asymmetries in visual field performance, with performance generally superior in the right visual field for verbal tasks and in the left visual field for spatial tasks. These asymmetries parallel those found in neurological studies of hemispheric specialization. Consequently, many investigators have concluded that visual hemifield differences are primarily a reflection of the functional differences between the two cerebral hemispheres. However, alternative explanations proposing that visual field effects are dependent on other factors such as inadequate fixation, eye movements during presentation, postexposural scanning, and attentional biases have been offered. The potential impact of each of these factors on visual field differences are reviewed and discussed. Evidence is provided suggesting that attention and hemispheric functional differences interact to produce the magnitude and direction of visual field differences.

Attention↗

PubMed1991

Cognitive abilities in androgen-insensitive subjects: comparison with control males and females from the same kindred.

To determine the effect of androgen insensitivity on cognitive abilities, subjects with the syndrome of complete androgen insensitivity (AI) were compared to control males and females from the same kindred on the Spanish version of the Wechsler Adult Intelligence Scale (WAIS). All subjects had similar sociocultural backgrounds and only right-handed subjects were used in the primary analysis. This design was chosen to diminish the effect of critical variables on test performance, thereby highlighting the effect of androgen unresponsiveness on cognition. The results indicated that control males and females were superior to androgen insensitive subjects on the Perceptual Organization factor, which included five visuospatial subtests. Separate analysis of these subtests revealed that males performed significantly better than females on Block Design, Picture Completion, and Object Assembly, and better than androgen insensitive subjects on all five subtests. Females were superior to androgen insensitive subjects on four subtests (Block Design, Picture Completion, Digit Symbol, and Picture Arrangement). Despite the small sample size, when female siblings were compared to their AI sisters, they were also superior on these four visuospatial subtests. The difference between the Verbal Comprehension and Perceptual Organization factors was greatest in androgen-insensitive subjects, while control males demonstrated the least difference. Females and AI subjects did not differ from one another on the Freedom from Distractibility factor nor on the subtests comprising it, but their performances were poorer than control males. None of the groups differed significantly on Full Scale IQ, Verbal IQ, the Verbal Comprehension factor, or any subtests included in this category.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

The corpus callosum and cerebral speech lateralization.

In order to specify the callosal involvement in the establishment of cerebral lateralization, a dichotic listening task was administered to six subjects with congenital absence of the corpus callosum, two callosotomized patients, and two hemispherectomized patients. The acallosal subjects were also compared to six subjects matched for age, sex, and hand dominance as well as to six subjects also matched for IQ. Our findings indicate that language functions, as assessed by dichotic listening performance, are more strongly lateralized in callosal agenesis subjects than in IQ-matched normal controls. Our results also reveal that hemispherectomized patients typically show a strong ear-advantage favoring the ear contralateral to their remaining hemisphere. Callosotomized patients, on the other hand, show a more variable pattern of results that seems to be related to the postsurgical time interval. Finally, our findings suggest that there might be a relationship between IQ and lateralization in subjects with borderline or mild deficiency.

Adolescent↗

PubMed1990

Gender, level of spatial ability, and lateralization of mental rotation.

The present study indicates that some of the inconsistencies in studies of the lateralization of mental rotation may be a consequence of uncontrolled individual differences in the general level of spatial ability. In order to investigate the relation between spatial ability and the lateralization of mental rotation, 48 subjects (24 males and 24 females) were divided into three groups based on their performance on a standardized test of spatial ability. They then performed a lateralized two-dimensional mental rotation task. The results showed the typical mental rotation function in that angle of rotation and reaction time were linearly related. A significant spatial ability by visual field interaction indicated that subjects with low spatial ability had a left field advantage, whereas subjects with medium spatial ability showed no field advantage and subjects with high spatial ability showed a right field advantage. Gender also interacted with visual field, with males showing a left visual superiority and females an insignificant right visual field advantage. A significant three-way interaction of gender, spatial ability, and angle of rotation reflected the fact that low spatial males were more profoundly affected by rotation than the other groups. The results suggest that at least some of the inconsistent findings in studies of lateralization of mental rotation may be accounted for by differences in the level of spatial ability.

Aptitude↗

PubMed1990

Locus of information in words and the right visual field effect.

The right visual field (RVF) advantage found for the identification or classification of words has usually been interpreted as evidence for left hemisphere language functions. It has more recently been explained as the result of the fact that the most informative part of the word, presumably the beginning, is in a region of better visual acuity. It is not clear from existing evidence that the beginnings of words are in fact more informative. The present study assessed the locus of information in words by deleting either the initial or terminal one or two letters. Subjects were required to generate a completion. Regardless of whether subjects were scored as correct for generating the original target word (as would be appropriate in a naming study) or for producing any legitimate word (as would be appropriate for a lexical decision study), the results indicated that most words have more information in the initial letters. Nevertheless, there are exceptions to this rule, and some words have more terminal information. Equal numbers of words with more initial information and with more terminal information were selected for two visual field studies in order to assess the effect of the locus of information on visual laterality. In neither a lexical decision study nor a naming study did locus of information affect the commonly observed right visual field superiority. Thus the distribution of information is not likely to be a major confounding variable in laterality studies employing horizontally presented words.

Adolescent↗

PubMed1990

Reliability of hand preference items and factors.

The present study examined the test-retest reliability of a 32-item version of the Waterloo Handedness Questionnaire (Steenhuis & Bryden, 1987, 1988, 1989) on 500 subjects. The questionnaire was shown to be reliable in terms of basic factor structure. High test-retest reliability was also found within subjects' responses and across items for both right-handers and left-handers, although left-handers were less consistent than right-handers, particularly with regard to direction of hand preference on individual questionnaire items. Furthermore, the direction of hand preference was more reliable than was the degree of hand preference. These data support a multidimensional view of hand preference in which both direction and degree can be reliably assessed.

Adult↗

PubMed1990

Sex differences and the role of figural complexity in determining the rate of mental rotation.

Two experiments were conducted to investigate the effects of figural complexity on the rate of mental rotation of 3-dimensional figures and to compare the performance of men and women. Complexity was manipulated in three ways: by changing the number of blocks in the figure (7 or 10), by altering the number of turns (2 or 3), and by using outline or solid figures. In the first study, these factors were manipulated between groups of subjects. Women showed steeper slopes than men, but none of the complexity variables affected either slope or intercept for the mental rotation function. In the second study, number of turns and number of blocks were manipulated within-subjects, using only the solid figures. There were significant sex differences in both slope and intercept, and the number of blocks affected the slope of the rotation function. In both studies, a small percentage of the subjects showed nonlinear functions relating angular rotation to response time. Although the women consistently showed slower rotation functions, rate of rotation did not relate either to figural complexity or to nonlinearity. The results suggest that the rate of mental rotation is not affected by figural complexity, at least at the levels used in the present study, and that men and women employ essentially similar strategies.

Adult↗

PubMed1989

Effects of cultural background and education on handedness.

A 5-item handedness questionnaire was given to 317 subjects in four different groups: (1) 51 Tucano (Amazonian jungle) adolescents (36 male, 15 female); (2) 66 Spanish-speaking adolescents (43 male, 23 female) with similar age and educational background to the Tucano group; (3) 100 urban subjects (50 male, 50 female) with a low educational level; and (4) 100 urban subjects (50 male, 50 female) with a high level of education. Hand preference scores were not affected by sex or educational level. The incidence of left-handedness was lower in the Tucano group than in the other groups, despite the fact that the Tucano culture is a highly permissive one. The two rural groups showed less extreme hand preferences than the urban groups, and the Tucano in particular were less likely to indicate extreme hand preferences on any of the items. These results indicate significant effects of culture and environment on declared hand preference, and may be pertinent to recent discussions of cerebral organization in illiterates.

Adolescent↗

PubMed1989

Different dimensions of hand preference that relate to skilled and unskilled activities.

Hand preference is multidimensional with two major factors and a variable number of minor factors. In the present factor analyses of hand preference, there was no evidence to support Healey, Liederman and Geschwind's (1986) suggestion that hand preference dimensions can be distinguished on the basis of those requiring movement of the distal musculature (fingers and hand) and those requiring movement of the proximal. The first factor reported here relates to "skilled" activities. Hand preference for the use of tools and manipulation of other objects is strongly lateralized in self-professed right- and left-handers. "Less skilled" activities such as picking up objects load on a second and a third factor. Preference for picking up objects including very small ones and relatively heavy ones is much less lateralized, although there appears to be a distinction between activities that involve strength and those that do not. A fourth factor relates to the use of bats and axes, a bimanual activity.

Adult↗

PubMed1989

Regional cerebral blood flow correlates of a dichotic listening task.

This investigation was designed to test the hypothesis that ear advantage on a dichotic listening (DL) task of pitch discrimination reflects asymmetries in the metabolic activities of the temporal lobes. Fourteen normal subjects, with either a left-ear advantage (LEA) (n = 9) or a right-ear advantage (REA) (n = 5) on the DL task, underwent measurements of regional cerebral blood flow (rCBF) during a resting baseline condition and during performance on the DL task. For both groups, the DL task was associated with selective and significant increases in rCBF to the contralateral posterior temporal lobe. Our finding of selective rCBF activation with dichotic stimulation may have potential implications for an understanding of the functional organization of the cerebral hemispheres.

Acoustic Stimulation↗