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Biomedical subjects

J B Hellige

Publications and source records attributed to J B Hellige.

At least 19 recordsLinked to original sources
PubMed2001

Categorical and coordinate spatial processing: more on contributions of the transient/magnocellular visual system.

Observers were presented with stimuli consisting of a line and two horizontally separated dots. A categorical spatial task required observers to indicate whether the dots were above or below the line and a coordinate spatial task required observers to indicate whether the line could fit into the space between the two dots. Coordinate (but not categorical) spatial processing was less accurate and took longer with stimuli presented on a red background than with stimuli presented on a green background, even though the background color varied randomly from trial to trial and the viewing screen remained gray between trials. Because the color red attenuates processing in the transient/magnocellular visual system, these results suggest that coordinate spatial processing is dependent on that pathway. Furthermore, such effects do not involve mechanisms of perceptual adaptation that depend on the same color background being present throughout an experiment or for a prolonged period of time. As in earlier experiments, the effects of color condition were the same regardless of which visual field (and hemisphere) received the stimulus information. However, in contrast to the results of earlier experiments, there was no significant interaction of task and visual field.

Adaptation, Physiological↗
PubMed2001

Are hemispheric strategy differences independent of the level of performance?

Studies requiring identification of consonant-vowel-consonant (CVC) nonwords have suggested that attention is distributed more slowly or sequentially across the letters when they are presented to the right hemisphere than to the left hemisphere. Two experiments investigated whether hemispheric differences in processing strategy would be reduced with reductions of hemispheric differences in accuracy. The magnitude of visual field differences in accuracy was controlled by manipulating exposure duration, and the effect was observed on visual field differences in processing strategy. For both CVC identification (Experiment 1) and identification of nonletter symbols (Experiment 2), hemispheric strategy differences were independent of differences in accuracy. Both quantitative and qualitative hemispheric differences in processing visual displays appear to depend on the nature of the stimuli and the nature of the processes they invoke.

Adolescent↗
PubMed1999

Quantitative and qualitative hemispheric asymmetry for processing Japanese kana.

Native Japanese speakers identified three-letter kana stimuli presented to the left visual field and right hemisphere (LVF/RH), to the right visual field and left hemisphere (RVF/LH), or to both visual fields and hemispheres simultaneously (BILATERAL trials). There were fewer errors on RVF/LH and BILATERAL trials than on LVF/RH trials. Qualitative analysis of error patterns indicated that there were many fewer errors of first-letter identification than of last-letter identification, suggesting top-to-bottom scanning of the kana characters. In contrast to similar studies presenting nonword letter trigrams to native English speakers, qualitative error patterns were identical for the three visual field conditions. Taken together with the results of earlier studies, the results of the present experiment indicate that the ubiquitous RVF/LH advantage reflects a left-hemisphere superiority for phonetic processing that generalizes across specific languages. At the same time, qualitative aspects of hemispheric asymmetry differ from one language to the next and may depend on such things as the way in which individual characters map onto the pronunciation of words and nonwords.

Brain↗
PubMed1999

Hemispheric asymmetries in vigilance and cerebral arousal mechanisms in younger and older adults.

Younger and older adults responded to an asterisk presented to either the left or right visual field, with delay interval between onset of a fixation cross and onset of the asterisk varied. At delay intervals longer than 3 s, reaction time was faster when the same visual field was stimulated on 2 successive trials than when different visual fields were stimulated. This prefield effect was larger in the left visual field (right hemisphere), consistent with hypotheses of hemispheric asymmetry for arousal and vigilance. For older adults, these results were obtained only when participants responded with the left hand, suggesting that some aspects of hemispheric asymmetry for attention-related processing or the efficiency of interhemispheric transfer may change in an age-related fashion.

Adolescent↗
PubMed1999

Effects of bilateral stimulation and stimulus redundancy on interhemispheric interaction.

Recent visual laterality studies have included trials in which critical stimulus information is presented simultaneously in both visual half-fields and, thereby, simultaneously to both cerebral hemispheres. To investigate interhemispheric interaction, researchers compare performance on bilateral redundant trials with performance on unilateral trials in which a single copy of the target is presented to one hemisphere or the other. The authors used the identification of nonword letter trigrams to examine the relationship between unilateral and bilateral performance when the 2 types of trials were equated for the number of locations stimulated (Experiment 1) and the number of redundant copies of the target (Experiment 2). Results suggest that when the number of stimulated locations is held constant, each of 2 copies of a target stimulus can be processed with the same efficiency and the same strategy as it would have been had it been the only copy.

Adult↗
PubMed1998

Relationships between brain morphology and behavioral measures of hemispheric asymmetry and interhemispheric interaction.

Thirty adult males identified consonant-vowel-consonant nonword trigrams projected briefly to the left visual field (right hemisphere), the right visual field (left hemisphere) or to both visual fields (and hemispheres) simultaneously. Magnetic resonance images of the brains of these same individuals provided measurements of the length of the Sylvian fissure and surface area of the planum temporale within each hemisphere as well as measurements of the midsagittal area of the corpus callosum. Both behavioral and morphological asymmetries were consistent with those found in previous studies. In addition, there were several relationships between brain morphology and trigram naming. For example, as the length of the right-hemisphere Sylvian fissure increased to become more like the typical length of the left-hemisphere Sylvian fissure, there were fewer errors of trigram identification and attention was distributed more quickly or evenly across the three letters contained in the display. In addition, as the midsagittal area of the corpus callosum increased, the percentage of errors increased on left visual field trials, but not on right visual field or bilateral trials, suggesting that an increase in corpus callosum size may be indicative of greater functional isolation of the two hemispheres.

Adult↗
PubMed1998

Hemispheric asymmetry for word naming: effects of frequency and regularity of pronunciation.

Observers named visually presented words as quickly as possible when the words were presented to the centre of a viewing screen (Experiments 1, 5, and 6) or were flashed to either the left visual field/right hemisphere (LVF/RH) or right visual field/left hemisphere (RVF/LH) on each trial (Experiments, 2, 3, and 4). Words varied in frequency of occurrence in the language and in regularity of pronunciation. On lateralised trials, there was a RVF/LH advantage for both error rate and reaction time, with this hemispheric asymmetry for word naming being independent of both frequency and regularity. The RVF/LH advantage was also independent of whether the letters within a word were arranged horizontally or vertically. Error rates and reaction times were lower for high-than for low-frequency words and lower for words with a regular pronunciation than for exception words. In addition, on centre trials the effects of regularity were larger for low-frequency words than for high-frequency words. However, when words were presented in the visual periphery, the effects of regularity were of the same magnitude for high-and low-frequency words. In view of the theoretical importance of the Frequency by Regularity interaction, this latter result suggests that word processing is qualitatively different in the visual periphery than in the centre of vision; indicating that perceptual asymmetries in a typical visual half-field experiment may be limited in what they can tell us about the relative contributions of the two hemispheres to processing words in the centre of vision.

Journal Article↗
PubMed1998

Spatial processing and hemispheric asymmetry. Contributions of the transient/magnocellular visual system.

Right-handed observers were presented with stimuli consisting of a line and two horizontally separated dots. A categorical spatial task required observers to indicate whether the dots were above or below the line, and a coordinate spatial task required observers to indicate whether the line could fit into the space between the two dots. For the coordinate task, reaction time was faster when the stimuli were presented to the left visual field (right hemisphere) than when the stimuli were presented to the right visual field (left hemisphere). The opposite hemispheric asymmetry was obtained for the categorical task. In addition, coordinate spatial processing took longer with stimuli presented on a red background than with stimuli presented on a green background. The opposite hemispheric asymmetry was obtained for the categorical task. In addition, coordinate spatial processing took longer with stimuli presented on a red background than with stimuli presented on a green background. The opposite trend characterized categorical spatial processing. Because the color red attenuates processing in the transient/magnocellular visual pathway, these results suggest that coordinate spatial processing is more dependent on the transient/magnocellular pathway than is categorical spatial processing. However, manipulations of color condition had no effect on visual field (hemispheric) asymmetries, suggesting that the two hemispheres rely on the same visual information and on the same computational mechanisms as each other-although they do not always use that information with equal efficiency.

Adult↗
PubMed1997

Effects of output order on hemispheric asymmetry for processing letter trigrams.

Observers identified consonant-vowel-consonant trigrams with the letters arranged vertically by pronouncing the stimulus (treating the bottom letter as the first letter) and spelling it from bottom to top. On each trial, the trigram was presented to the left visual field/right hemisphere (LVF/RH), to the right visual field/left hemisphere (RVF/LH), or to both visual fields simultaneously (BILATERAL trials). Quantitative and qualitative visual field differences were identical to those found when observers used a more natural response output order, treating the top letter of the trigram as the first letter. The results suggest that, regardless of output order, attention is distributed across the three letters in a relatively slow, top-to-bottom fashion on LVF/RH and BILATERAL trials, whereas attention is distributed more rapidly and evenly across the three letters on RVF/LH trials.

Brain↗
PubMed1997

Individual differences in lateralization: effects of gender and handedness.

Male and female left- and right-handers participated in 3 experiments designed to investigate 3 components of performance asymmetry in lateralized tasks. Experiment 1 used a consonant-vowel-consonant (CVC) identification task measuring quantitative differences in hemispheric abilities and hemispheric control and qualitative differences in hemispheric strategies. The quantitative data revealed that left-handers have a smaller performance asymmetry than do right-handers and that both groups have the same degree of increased accuracy when stimuli are presented bilaterally. Handedness affected the qualitative measures of men, not of women. Experiment 2 used nominal and physical letter-matching tasks with bilateral presentations and measured the flexibility of callosal function. The results suggest that left-handers have less flexible interhemispheric communication than do right-handers and show no effect of gender. Experiment 3 used a chair identification task indexing hemispheric arousal bias. Left-handers tended to have more aroused right than left hemispheres, whereas the distribution of right-handers was centered around 0 arousal bias. Intertask analyses revealed a relationship between arousal bias and metacontrol, where individuals with more aroused right hemispheres tended to use a right-hemisphere strategy in the bilateral condition of the CVC experiment. Intercorrelations between measures from the experiments revealed only a limited relationship between metacontrol patterns in the CVC task and a measure of callosal flexibility in the physical letter-matching task. The results are discussed in the context of the relationships between dimensions of hemispheric asymmetry.

Adult↗
PubMed1996

Hemispheric asymmetry for visual information processing.

The left and right hemispheres of humans do not handle all aspects of visual information processing with equal ability. This is illustrated by a review of research concerning the processing of global versus local stimulus properties, low versus high spatial frequencies, and coordinate versus categorical spatial relationships. In general, the right hemisphere is dominant for processing global aspects of visual stimuli that are carried by low spatial frequencies, for the processing of coordinate spatial relationships and, perhaps, for extracting information from the magnocellular visual pathway. In something of a complementary manner, the left hemisphere is dominant for processing local aspects of visual stimuli that are carried by high spatial frequencies and, perhaps, for processing categorical spatial relationships and for extracting information from parvocellular visual pathway. Consideration is given to developmental mechanisms that may underlie the emergence of hemispheric asymmetry for these interrelated aspects of visual information processing.

Brain↗
PubMed1995

Fluctuations of perceptual asymmetry across time in women and men: effects related to the menstrual cycle.

Women and men performed the same tachistoscopic chair identification task and free-vision face processing task during each of three test sessions. For women, the first and third sessions were performed during two successive periods of menstruation and the second session was performed during the intervening midluteal phase of the menstrual cycle. For men, the three test sessions were presented at 2-week intervals. For the chair identification task, there was no visual field (hemispheric) asymmetry for men during any of the three test sessions. For women, there was a right visual field (left-hemisphere) advantage during the second (midluteal) test session, but not during the first and third (menstrual) sessions. For the free-vision face processing task, there was a robust left-side (right-hemisphere) bias during all test sessions for both women and men and no effect of test session for either gender. Results for the nonlateralized chair identification task are consistent with the hypothesis that, in women, the left hemisphere is more activated during the midluteal phase of the menstrual cycle relative to the menstrual phase. Results for the lateralized face processing task suggest that hemispheric dominance for specific aspects of information processing are less likely to show such phase-related effects.

Brain↗
PubMed1995

Age differences and similarities in patterns of cerebral hemispheric asymmetry.

Younger (M age = 20.4 years) and older (M age = 70.7 years) adults participated in 3 visual half-field experiments. These were designed to examine specific aspects of hemispheric asymmetry: (a) hemispheric dominance for phonetic-linguistic processing (as measured by identification of non-word trigrams), (b) hemispheric differences in trigram processing strategy, (c) characteristic perceptual biases thought to reflect hemispheric arousal asymmetries, and (d) hemispheric dominance for processing emotions shown on faces. Patterns of left-right asymmetries were comparable for older and younger participants, and intercorrelations among the various measures of asymmetry were similar for both groups. In view of the present results, it seems unlikely that changes in hemispheric asymmetry contribute significantly to age-related changes in cognitive functioning.

Adolescent↗
PubMed1994

Effect of skill on visual laterality: now you see it--now you don't.

Clancy and Hoyer (1993) have recently investigated the effects of domain-specific expertise and hemispheric asymmetry on detecting featural differences in visual patterns. Based on the pattern of reaction time results, they concluded that there is a left-hemisphere advantage for making difficult, domain-relevant visual discriminations in skilled experts but not in unskilled control subjects. However, response accuracy data from the same experiment contradict their conclusions about the relationship of skill to the pattern of hemispheric asymmetry and favor an alternative interpretation in terms of the specific aspects of visual information needed to make different types of discrimination.

Attention↗
PubMed1994

Babies, bath water, and the chicken's way out.

Bryden, McManus, and Bulman-Fleming (1994) have provided a thoughtful critique of the developmental model of cerebral lateralization proposed by Geschwind, Behan, and Galaburda. Although it is clear that many particular aspects of the Geschwind-Behan-Galaburda (GBG) model have not withstood empirical test, the GBG model has had an important and useful impact by encouraging others to conceptualize cerebral laterality in an appropriately developmental way. Consequently, although the present commentary reinforces some of the criticisms leveled by Bryden et al., it also points out why it would be unwise to throw out the baby (i.e., a developmental perspective) with the bath water (i.e., particular details of the GBG model).

Animals↗
PubMed1994

Hemispheric asymmetry for processing unpronounceable and pronounceable letter trigrams.

In each of two experiments, observers attempted to identify three-letter strings presented briefly to the left visual field/right hemisphere (LVF/RH), to the right visual field/left hemisphere (RVF/LH), or to both visual fields (and hemispheres) simultaneously (redundant BILATERAL trials). Similar visual half-field effects were obtained for both all-consonant (CCC) strings and consonant-vowel-consonant (CVC) nonwords. For both types of strings, there were fewer errors on RVF/LH trials than on LVF/RH trials and the pattern of error types was qualitatively different for the two visual fields. The similarity of visual half-field results for CCC and CVC strings indicates that results that have been reported in earlier studies with CVC strings are not restricted to letter strings that can be coded as a single pronounceable syllable, as some have suggested. Instead, the results are consistent with hypotheses about hemispheric differences in the ability to encode and remember individual letters in a multielement display. In addition, for both CCC and CVC letter strings there were fewer errors on redundant BILATERAL trials than on either type of unilateral trial, suggesting interhemispheric collaboration in both cases. However, the qualitative error patterns obtained on redundant BILATERAL trials suggest that the precise way in which the hemispheres collaborate differs with the type of letter string.

Adult↗
PubMed1994

Individual variation in hemispheric asymmetry: multitask study of effects related to handedness and sex.

Functional hemispheric asymmetries were examined for right- or left-handed men and women. Tasks involved (a) auditory processing of verbal material, (b) processing of emotions shown on faces, (c) processing of visual categorical and coordinate spatial relations, and (d) visual processing of verbal material. Similar performance asymmetries were found for the right-handed and left-handed groups, but the average asymmetries tended to be smaller for the left-handed group. For the most part, measures of performance asymmetry obtained from the different tasks did not correlate with each other, suggesting that individual subjects cannot be simply characterized as strongly or weakly lateralized. However, ear differences obtained in Task 1 did correlate significantly with certain visual field differences obtained in Task 4, suggesting that both tasks are sensitive to hemispheric asymmetry in similar phonetic or language-related processes.

Brain↗