Recognition of tachistoscopically presented verbal and non-verbal material after unilateral cerebral damage

Three groups of S's were examined in order to study the effects of unilateral brain-damage on recognition rates for verbal and non-verbal stimuli in the lateral visual fields. Patients with damage in the region of the middle cerebral artery of the left or right hemisphere and neurologically intact individuals were asked to identify verbal and non-verbal stimuli presented tachistoscopically in each field. The results indicate superior recognition for both types of stimuli in the visual field contralateral to the intact hemisphere. The effect is greater for non-verbal material with right hemisphere injury and greater for verbal material with left hemisphere injury. A significant superiority of recognition in the nasal field of each eye is found to interact with the effect of the side of lesion and type of material.     

Interhemispheric cooperation of left- and right-handers in mental calculation tasks

Relations between handedness and interhemispheric processing in cognitive tasks were examined. Thirty six right-handers and thirty left-handers (familial and nonfamilial left-handers) were asked to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field, or one to the left and one to the right visual field simultaneously. In Experiment 1, the numbers were displayed in Arabic numerals, and in Experiment 2 one of the numbers was displayed in Kanji and one in Arabic numerals. The results of Experiment 1 showed a bilateral advantage, however no subject group difference was shown in the performance of the three (left unilateral, right unilateral, and bilateral) presentation conditions. Though familial left-handers showed a weaker tendency to different patterns than right and non-familial left-handers, the results of Experiment 2 were largely similar to those of Experiment 1. These findings suggest that interhemispheric processing may not differ between left- and right-handers.     

Attentional mechanisms and perceptual asymmetries in tachistoscopic recognition of words and faces.

In simultaneous bilateral tachistoscopic recognition tasks, normal right-handers named more words in the right visual field and recognized more faces in the left visual field. Priming the left hemisphere with a verbal task diminished the left field superiority for faces, and priming the right hemisphere with a face-recognition task, reduced the right visual field superiority for words. These priming effects disappeared when a recognition procedure was used. When words and faces were presented simultaneously, subjects required to attend to the faces and report them first showed a left visual field superiority for faces and a right visual field superiority for words. Subjects told to attend to the words and report them first showed only the right visual field superiority for words.     

Interhemispheric Cooperation of Left- and Righthanders in Mental Calculation Tasks

Relations between handedness and interhemispheric processing in cognitive tasks were examined. Thirty six right-handers and thirty left-handers (familial and nonfamilial left-handers) were asked to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field, or one to the left and one to the right visual field simultaneously. In Experiment 1, the numbers were displayed in Arabic numerals, and in Experiment 2 one of the numbers was displayed in Kanji and one in Arabic numerals. The results of Experiment 1 showed a bilateral advantage, however no subject group difference was shown in the performance of the three (left unilateral, right unilateral, and bilateral) presentation conditions. Though familial left-handers showed a weaker tendency to different patterns than right and non-familial left-handers, the results of Experiment 2 were largely similar to those of Experiment 1. These findings suggest that interhemispheric processing may not differ between left- and righthanders.     

Temporal integration of form as a function of subject handedness and retinal locus of presentation

Two experiments are reported examining differences in perceptual processing as a function of subject handedness. Experiment 1 compared performance in the left vs right visual fields of right- vs left-handed subjects. Only right-handed subjects exhibited an interaction of visual field with spatial frequency (as mediated by interflash interval), suggesting that left-handers are not differentially lateralized for high vs low spatial frequency processing. Experiment 2 examined foveal performance in left-handers vs right-handers with or without familial sinistrality. Subjects with personal or familial sinistrality exhibited superior performance when the processing of low frequencies was required, suggesting that sinistrality may confer an advantage in the processing of lower spatial frequencies.     

Motor control of the hands: the effect of familial sinistrality.

Left- and right-handed subjects, selected on the basis of degree of hand preference and for the presence or absence of familial sinistrality, responded to monaurally presented tonal stimuli (440 Hz note played on four different instruments) using their right and left hands on separate occasions. It was found that in both the strong left-handers and the inconsistent strong right-handers, motor control of the hands was related to familial sinistrality (FS). Specifically, strong left-handers and inconsistent strong right-handers with FS have a difference in the motor control of the hands in the left hemisphere, with a left hemisphere-left hand advantage. Strong left-handers and inconsistent strong right-handers with no FS have a difference in the motor control of the hands in the right hemisphere, with a right hemisphere-left hand advantage.     

DEVELOPMENT OF MOTOR CO-ORDINATION BY NORMAL LEFT-HANDED CHILDREN

Ninety-six normal left-handed children were tested for motor co-ordination on a series of timed repetitive tasks, alternating left and right hands, feet and fingers. Preferred hand advantage could be demonstrated to the same degree for the left hand of these children as it had been for the preferred right hand in previously studied groups of the same age (Denckla 1973, 1974). The only test (finger to thumb successive opposition) that failed to show a preferred hand advantage in left-handers also had failed to show such an advantage among right-handers. This same test was performed more rapidly by left-handed girls than boys, as it had been by right-handed girls. However, left-foot superiority appeared to be less well established among left-handers than superiority of the right foot among right-handers, and at a later age. Left-handed children were less likely than their right-handed counterparts to choose their preferred hand when trying out a new task. Writing posture, i.e. whether inverted or straight, could not be established unambiguously for the left-handed children up to the age of 10, and often differed for writing and printing.     

Effects of Sex,Handedness, Stimulus and Visual Field on “Mental Rotation”

Shepard's mental rotation paradigm (e.g. Shepard and Metzler, 1971) was modified to allow tachistoscopic presentation of stimuli at varying angles of orientation (0° to 180°) in the right and left visual fields. Thirty male and thirty female subjects divided into three handedness groups (right-handers, non-familial and familial left-handers) judged whether a stimulus was a standard form or its mirror image. In general response times for correct judgements (RT_c) increased monotonically as a function of angle of orientation though the curves tended to be negatively accelerated rather than linear. Right-handers showed a slower rate of increase in RT_c as a function of angle than either left-handed group. Mean RT_c and the rate of increase in RT_c were equivalent for the two sexes and for the two visual fields. Both mean RT_cs and on the rate of increase in RT_c varied as a function of the stimulus.Error rates also increased monotonically as a function of angle of orientation. No sex or handedness differences in error rates were found. However, errors increased significantly less rapidly when stimuli were presented in the left visual field. It is argued that right hemisphere specialization for spatial processing minimizes the rate of increase in errors.The present failure to find sex differences may be of interest and it is argued that rapid presentation of stimuli results in subjects setting maximum and minimun response times. Within this relatively restricted “bandwith” of response times males and females may perform spatial tasks equally efficiently. Some confirmation for this hypothesis vs. an alternative based upon differences in hemispheric organization was found in a second experiment.     

Hemispheric dominance for speech and calculation: electrophysiologic correlates of left dominance in left handedness

Slow brain potentials were recorded in left-handers and right-handers during: (i) processing of language and mental arithmetic tasks, without vocalization, and (ii) subsequent writing down of the answers with either the right or left hand. Left-sided laterality of negative potentials was taken as evidence of hemispheric dominance. It appeared during the processing of words and numbers in 26 of the 30 left-handers and was localized mainly in the left frontal and temporal parietal regions. Similar results were found with the right-handers. This electrophysiological evidence indicates that the left hemisphere is dominant for language and calculation in the vast majority of left-handers. Only when writing with either their left or right hand do left-handers show less left-sided laterality than right-handers.     

Sex and handedness differences in eye-hand visual reaction times in handball players

Sex and handedness differences in the eye-dominant hand, the right eye-right hand and the left eye-left hand visual reaction times were studied in 270 right-handed and 56 left -handed young handball players. Reaction time was assessed by a software package. All visual reaction times were longer in women than in men. In the eye-dominant hand and the left eye- left hand visual reaction times, the left-handers had a superiority over the right handers, but there was no difference between the right eye-right hand visual reaction times of the right- and left-handers. In right-handers, all visual reaction times were longer in women than in men, but there was no sex difference in left-handers. The results suggest that left-handed players have probably an intrinsic neurological advantage.     

SEX AND HANDEDNESS DIFFERENCES IN EYE-HAND VISUAL REACTION TIMES IN HANDBALL PLAYERS

Sex and handedness differences in the eye-dominant hand, the right eye-right hand and the left eye-left hand visual reaction times were studied in 270 right-handed and 56 left­-handed young handball players. Reaction­ time was assessed by a software package. All visual reaction times were longer in women than in men. In the eye-dominant hand and the left eye-­left hand visual reaction times, the left-handers had a superiority over the right handers, but there was no difference between the right eye-right hand visual reaction times of the right- and left-handers. In right-handers, all visual reaction times were longer in women than in men, but there was no sex difference in left-handers. The results suggest that left-handed players have probably an intrinsic neurological advantage.     

Reaction time differences between left- and right-handers during mental rotation of hand pictures

During mental rotation tasks using hand pictures, right-handers make left–right judgements by mentally rotating their own hand to an orientation of the presented hand image. Although strategy difference for the tasks between left- and right-handers has been suggested, the strategy of left-handers has been incompletely understood. In the present study we compared differences in reaction times between 15 left-handed and 16 right-handed normal individuals during a mental rotation task using simple hand pictures. Participants were required to identify pictures of a hand presented in four orientations (upright, counterclockwise rotated, clockwise rotated, and inverted) as either a right or a left hand. Right-handers recognised a right hand faster than a left hand, whereas no significant difference was seen for left-handers. Both left- and right-handers recognised a right hand faster than a left hand in counterclockwise-rotated images, and recognised a left hand faster than a right hand in clockwise-rotated images. The findings suggest that the differences in the reaction times between left- and right-handers depend on a laterality balance of hand motor skills. During mental rotation task using simple hand pictures, left-handers may mentally simulate their own hand to match the stimulus image as similar to right-handers.     

Influence of handedness on peripheral auditory asymmetry

It is well established that in humans many differences between right- and left-handers, anatomical, physiological and functional, exist. Left- and mixed-handedness is associated with greater bihemispheric representation of cognitive functions than in right-handers. Several studies indicate a left–right asymmetry in the function of hearing pathways between cochlea and auditory cortex, and furthermore, that this asymmetry is associated with handedness. Our investigation focuses on the medial olivo-cochlear system, which has been demonstrated to be more effective in the right than left ear in right-handers. The aim of the study was to investigate this auditory efferent system asymmetry according to handedness, gender, eyedness, footedness and the presence of spontaneous otoacoustic emissions. The medial efferent system has been found to be more effective in the right than left ear in right-handers, while functioning symmetrically in left-handers. Furthermore, the olivo-cochlear system, assumed to be involved in basic language processing, shows an asymmetrical pattern of functioning influenced by handedness as well as by hemispheric language representation. Reverse medial efferent system asymmetry was observed in left-handers compared to that in right-handers, on condition that only left-handed males were considered, or that the left-handers were also left-eyed, or that spontaneous otoacoustic emissions were present in the left ear of the left-handers, or when only left-handers without mixed-handers were considered.     

Clinical importance of asymmetry and handedness differences in common carotid artery intima-media thickness

Earlier publications have reported that common carotid artery intima-media thickness (CCA-IMT) was lower on the right side than on the left side and that left-handed patients have a lower risk of sudden death of brain infarction. This study aimed to determine whether there is an asymmetry and the handedness related difference in CCA-IMT. Ultrasonographic examinations were performed with the use of Aplio US system. In total sample, male and female left-handers, CCA-IMT was greater on left side than on right side. In men, both right and left CCA-IMTs, but in women only right IMT, were lower in the left-handers than in the right-handers. Both right and left CCA-IMTs was positively correlated with age in men and in women. Handedness was a significant factor influencing CCA-IMT with adjustment for sex and age. It was greater on left side than on right side, especially in the left-handers. CCA-IMTs were lower in the left-handers than in the right-handers. These results suggest that hemodynamic stress and intimal damage was larger in the left carotid artery, which was larger in the right-handers compared to the left-handers.     

Zur hemispha¨rendominanz fu¨r sprache und rechnen: Elektrophysiologische korrelate einer linksdominanz bei linksha¨ndern

Slow brain potentials were recorded in left-handers and right-handers during: (i) processing of language and mental arithmetic tasks, without vocalization, and (ii) subsequent writing down of the answers with either the right or left hand. Left-sided laterality of negative potentials was taken as evidence of hemispheric dominance. It appeared during the processing of words and numbers in 26 of the 30 left-handers and was localized mainly in the left frontal and temporal parietal regions. Similar results were found with the right-handers. This electrophysiological evidence indicates that the left hemisphere is dominant for language and calculation in the vast majority of left-handers. Only when writing with either their left or right hand do left-handers show less left-sided laterality than right-handers.     

Direction of hand preference: the connection with speech and the influence of familial handedness

Taking familial handedness into account, right- and left-handers with differing degrees of hand preference were monaurally presented with verbal stimuli (CVs) to which they responded using their right and left hands at separate times. This reaction time design was used to ascertain the relative cognitive functioning capacity of each hemisphere for verbal processing. However, the results disclosed more about the determination of direction of hand preference than about cognitive processing, per se. It was found that in both strong right-handers and strong left-handers with an incongruent hand preference (i.e., own handedness incongruent with family history of handedness) direction of hand preference is the result of suppression of the nonpreferred hand in the left hemisphere. Strong right- and strong left-handers with a congruent hand preference (i.e., hand preference congruent with family history of handedness) appear to have a more direct hand preference-left hemisphere mechanism. The findings of the present study are used to form part of a new theory of hand preference determination.     

Independent functioning of the two cerebral hemispheres for recognizing bilaterally presented tachistoscopic visual-half-field stimuli.

Bilateral tachistoscopic presentation of verbal stimuli produces a significantly larger right visual half-field (VHF) superiority than does unilateral presentation, when fixation is controlled by a center digit. This experiment tested whether the increased asymmetry was due to (a) subjects attending the right VHF and ignoring the left VHF or (b) interference between the hemispheres due to competition for the left hemisphere language areas. Words, shaptes, and pictures of faces were presented bilaterally to each VHF, with fixation controlled by a center digit. In three conditions, the same type of stimuli was presented in each VHF (e.g., a word in both the left and right VHF). In two conditions words were presented to one VHF and nonverbal stimuli to the opposite VHF (words paired with words and words paired with faces). It was found that the stimulus pairings did not affect VHF asymmetry for any stimulus. Words showed a large right VHF superiority in all conditions. Shapes showed a significantly smaller right VHF superiority in all conditions. Faces showed no VHF asymmetry in any condition. It was concluded that attentional factors were not important since shapes or faces could be recognized accurately from the left VHF without lowering verbal recognition from the right VHF. Thus the low recognition accuracy from the left VHF is specific for verbal stimuli rather than attentional. The interference hypothesis was also not supported since all the right VHF stimuli (words, shapes, or faces) were associated with low recognition of words from the left VHF. It was suggested instead that VHF asymmetry under unilateral and bilateral presentation reflect two different mechanisms. Under conditions of unilateral presentation, VHF asymmetries are caused by loss of information when any given stimulus must cross the callosum to reach the hemisphere specialized for its processing. However, with bilateral VHF presentation and fixation control, the two hemispheres act as independent channels for information processing. Under this condition, each hemisphere recognized the stimulus from its contralateral VHF. Thus the large right VHF superiority for words with bilateral presentation reflects the superior ability of the left hemisphere for verbal recognition.     

Laterality differences in recognition of Japanese and Hangul words by monolinguals and bilinguals

Two-character nonsense Kana words, individual Kanji words and individual Hangul words are presented tachistoscopically in the left or right visual field to 20 normal, right-handed Japanese students and 13 normal, right-handed Korean subjects. The former did not know Hangul letters. The latter were born and raised in Japan, in exclusively Japanese-speaking families, but they could read Hangul letters and write them a little because they have learned the Hangul language for 6 months. In each of three conditions (Kana, Kanji and Hangul work recognition), each subject was required to move the index finger of his right or left hand leftwards as fast as possible after the presentation of two of four stimuli and rightwards after the presentation of the other two. The reaction time was measured. A significant right field superiority for the recognition of Kana words and no lateral asymmetry for Kanji words were shown in both Japanese and Korean groups. However, for the Hangul recognition, a significant left field superiority for Japanese subjects and a significant right field superiority for Korean subjects were obtained. These findings are interpreted as follows. Kana and Kanji are processed somewhat differently in the cerebral hemispheres. Japanese subjects do not recognize Hangul stimuli as orthographic characters but as shapes or figures. Korean subjects can identify Hangul stimuli as letters. Both the first language (Kana) and second language (Hangul) are processed in the dominant left hemisphere by right-handed Korean subjects.     

Material specific hemispherical arousal.

It has been previously demonstrated that warning stimuli (WS) reduce reaction time (RT) by causing cortical activation. The purpose of this study was to use verbal and non-verbal WS to see if these stimuli asymmetrically activate the cerebral hemispheres.Sixteen right-handed Ss were given a manual RT task using a light as the RT stimulus and either verbal or non-verbal sounds as WS. RTs by the right hand were significantly faster with verbal WS than with non-verbal WS. There were no significant differences for the left hand between the verbal and non-verbal WS. These results give partial support to the asymmetrical activation hypothesis.     

DIRECTION OF HAND PREFERENCE: THE CONNECTION WITH SPEECH AND THE INFLUENCE OF FAMILIAL HANDEDNESS

Taking familial handedness into account, right- and left-handers with differing degrees of hand preference were monaurally presented with verbal stimuli (CVs) to which they responded using their right and left hands at separate times. This reaction time design was used to ascertain the relative cognitive functioning capacity of each hemisphere for verbal processing. However, the results disclosed more about the determination of direction of hand preference than about cognitive processing, per se. It was found that in both strong right-handers and strong left-handers with an incongruent hand preference (i.e., own handedness incongruent with family history of handedness) direction of hand preference is the result of suppression of the nonpreferred hand in the left hemisphere. Strong right- and strong left-handers with a congruent hand preference (i.e., hand preference congruent with family history of handed ness) appear to have a more direct hand preference-left hemisphere mechanism. The findings of the present study are used to form part of a new theory of hand preference determination.