Hemispheric asymmetry for alphabetic identification: Scaling analyses

In a test of the analytic-holistic theory of hemispheric asymmetry, 20 subjects saw brief presentations of upper-case letters in either the left or right visual half-field. A right half-field advantage was found for both accuracy of identification and vocal latency of erroneous responses. Multidimensional scaling, hierarchical clustering, and correlation analyses of the error patterns indicated similarities of processing between the hemispheres. The results were discussed in terms of loss of information from storage prior to processing.     

Lateralization of defence mechanisms related to creative functioning

Eighty-four undergraduate students were randomly divided into left and right visual half-field groups. They were tested in either visual half-field with a percept-genetic test of anxiety and defense mechanisms (the MCT). The subjects also took a test of creative functioning (the CFT) and degree of lateralization in the MCT was related to level of creativity in the CFT. Subjects low in creativity were significantly lateralized on measures typical for the right visual half-field group (isolation and repression) and tended to differ on a left visual half-field measure (regressive strategies). For high creative subjects no differences were found between the visual half-field groups. Also, high creative persons more often responded with non-hemisphere-specific defenses than low creative ones. The results were interpreted as due to differing levels of transmission of information between the two hemispheres of the brain.     

Bilateral tachistoscopic word perception of stutterers and normal subjects

Bilateral tachistoscopic procedures were utilized to investigate the visual half-field preferences of 15 stutterers and a group of 15 normal controls. Statistical analyses indicated a right visual half-field preference for the control group. In contrast, a significant visual half-field preference was not revealed for the stuttering group. However, further analysis revealed that a significantly larger proportion of stutterers, compared to controls, demonstrated a left visual half-field preference. Results indicated reversed cerebral processing for the stuttering group as compared with the control group.     

Perceptual interference and hemispheric specialization

Two experiments evaluated the effect of stimuli presented at fixation on the recognition of faces or random shapes presented to the left or right visual half-field (VF). Increasing the processing demands of the center stimulus produced a large, linear decrease in recognition from both VFs for both faces and shapes. Recognition of random shapes was decreased more in the right visual field by center digits and in the left VF by center faces and shapes. In addition, interference was found between the VF faces and the center digits to the left of fixation. It was concluded that differences in the processing capacity of the two hemispheres are a function of the verbal-nonverbal nature of the stimuli at a later stage in processing but that the two hemispheres may also differ along other perceptual dimensions at an earlier stage of visual recognition.     

Parallel but temporally displaced visual half-field metacontrast functions

Using a classic letter-ring metacontrast paradigm, left and right visual field meta-contrast functions were separately determined. The parallel U-shaped recognition functions for both half-fields were found to interact differentially with stimulus onset asynchrony, the left visual field function being displaced by 13 ms toward longer test stimulus-masking stimulus separations. This result was consistent with the hypothesis of longer processing time requirements for verbal stimuli delivered to the right than to the left hemisphere. This indicates that the neural locus (loci) responsible for left visual field verbal processing delay is (are) capable of mediating metacontrast phenomena. It was tentatively concluded that a relative processing delay within the right hemisphere underlies the differing visual half-field metacontrast interaction with stimulus onset asynchrony.     

Hemispheric asymmetry and electrodermal activity in orienting and pavlovian conditioning paradigms

Three experiments on lateralization of electrodermal orienting and conditioned behavior are reported. The basic findings show effects of hemispheric asymmetry on initial magnitude and rate of habituation of phasic stimulus-elicited electrodermal responses. In summary, responses to verbal stimuli repeatedly flashed to the right visual half-field are larger than corresponding responses in the left half-field. Similarily, spatially relevant stimuli initially presented to the left half-field result in larger responses than when the same stimuli are repeatedly presented in the right half-field. In the auditory modality, data show asymmetrical control of responding to verbal material in a dichotic conditioning paradigm with greater resistance to extinction when the conditioned stimulus is initially fed only to the left hemisphere as compared to when it is fed only to the right hemisphere. It is argued that the present approach taps on basic mechanisms for the lateralization of attentional and associative functions.     

Does Global Context Modulate Cerebral Asymmetries? A Review and New Evidence on Word Imageability Effects

In this article we examine whether the distribution of function across the right and left cerebral hemispheres for lexical processing is influenced by the global context within which words are presented. A review of previously published studies indicates that the ubiquitous right visual field (RVF)/left hemisphere advantage for word recognition may be reduced or eliminated for nouns, content words, or high image words, but only when such items are presented along with verbs, function words, or low image words. However, paradoxically, when the former items are presented in more homogeneous contexts, the RVF advantage is uniformly observed. We propose that the processing efficiency of a hemisphere for a given stimulus depends on that item's relation to the other stimuli provided, that is, the global context. This was examined in a visual half-field experiment that varied whether high and low image nouns were presented in homogeneous (blocked lists) or heterogeneous (mixed lists) contexts. An unvarying RVF advantage was observed for high image words in homogeneous contexts, but this advantage was eliminated when the same items were presented in heterogeneous contexts. We suggest that stimulus heterogeneity maximizes reliance on differing, but complementary, computational biases across hemispheres. Hence, the extent to which the left and right hemispheres are recruited for the recognition of individual word types can vary dynamically with variation in the stimulus environment.     

Letter versus dot stimuli as tools for “splitting the normal brain with reaction time”

Filbey and Gazzaniga (1969) found simple dot-present or -absent reports averaged 35 ms slower for the left than for the right visual field. Other data suggests that verbal processing efficiency differences between the cerebral hemispheres, rather than transcallosal transfer time alone, must be tapped to obtain half-field differences as large as 35 ms. Three experiments were conducted. The first failed to show any half-field differences in vocal RT for dot detection; the second replicated previous reports of significant right field superiority of vocal RT to letter stimuli for right handers, and also showed a substantially smaller half-field difference for left handers; the third experiment, utilizing the fixation control procedure of the second experiment, again failed to show half-field differences for the dot detection paradigm. Differences between the Filbey and Gazzaniga and present results probably reflect important procedural differences. We conclude that transcallosal transfer time for simple dot information is much smaller than assumed by Filbey and Gazzaniga and that the letter report-time task taps hemispheric asymmetries of verbal processing efficiency.     

Lateralization of defence mechanisms in a visual half-field paradigm

A percept-genetic test of defence mechanisms (the Meta-Contrast Technique) was given to 169 undergraduate students. Subjects were divided into three groups: two visual half-field groups and one group tested in the regular way. It was hypothesized that the visual field groups would differ from one another and from the control group. An ANOVA showed that the left and right visual half-field conditions differed significantly, as hypothesized. Clear regressive signs were more common in the left visual half-field group, whereas isolation and repression were more common in the right. Furthermore, the visual half-field conditions differed in certain respects from the control group. It was concluded that processes in both hemispheres are important for complex psychological functions.     

Visual field x response hand interactions and level priming in the processing of laterally presented hierarchical stimuli

Hemisphere-specific processing of laterally presented global and local stimulus levels was investigated by (a) examining interactions between the visual field of stimulus presentation and the response hand and (b) comparing intra- with inter-hemispheric effects of level priming (i.e. faster and more accurate performance when the target level repeats). Although in Experiment 1, which involved two-choice responses with left and right hands, performance costs occurred when the same hemisphere received the stimulus and controlled the response hand, further analyses suggest that these effects reflect spatial compatibility rather than intra-hemispheric interference. Consistent with the spatial compatibility interpretation, in Experiment 2 a similar visual field x response interaction was obtained with regard to left and right responses given with the same hand. Trial-to-trial level priming occurred in both experiments and was unaffected by the intra-hemispheric sequence of target levels. Implications regarding hemispheric processing mode are discussed.     

Bilateral tachistoscopic perception, handedness, and laterality.

Right-handed, familial left-handed, and nonfamilial left-handed males and females reported high- or low-imagery words which were located to the left and right of fixation in bilateral tachistoscopic displays. On each trial, an arrowhead appeared in the center of the display. The arrowhead pointed to either the left or the right half-field, indicating the order of report. Right-handers reported more accurately from the right half-field, and familial left-handers reported more accurately from the left half-field. The order of report results showed that right-handers were similar to nonfamilial left-handers; for left half-field presentation, both groups were more accurate when the arrowhead pointed to the left than when it pointed to the right (i.e., first report was more accurate than second report). There was a main effect of word imagery, but this factor did not interact with visual half-field. Thus, there was no evidence that representations of high-imagery words are lateralized differently than representations of low-imagery words. The results are discussed with respect to lateralization of memory for verbal material.     

Mirror-reading in right- and left-handers

In mirror-reading, words are read from right to left and letters are read in a reverse right-to-left orientation. In one experiment we compared the ability of normal right- and left-handed subjects to mirror-read and found that the left-handers made fewer errors and could read mirror print more rapidly. In a second experiment we attempted to learn whether there is a hemifield superiority for reading mirror words and whether there are any differences between left- and right-handers in a hemifield. We found that although both right- and left-handers more rapidly detected mirror words projected to the left visual half-field, there were no differences between groups. However, in the right visual half-field, the performance of left-handers was superior to that of the right-handers. The results of the hemifield study suggest that left-handers may be superior at reading mirror words because they can more easily reverse their scanning pattern.     

ROTATION OF MENTAL IMAGES IN BABOONS WHEN THE VISUAL INPUT IS DIRECTED TO THE LEFT CEREBRAL HEMISPHERE

Abstract— The mental rotation phenomenon was examined in baboons and humans using a video-formatted matching-to-sample task. Sample stimuli were presented either centrally or in the right or left visual half-field. Immediately afterward, subjects had to distinguish the previously presented sample Stimulus from its mirror image after both had been rotated to the same angular deviation. A mental rotation phenomenon was found in baboons and humans, but in baboons this effect wax limited to conditions in which visual input was directed to the right visual half-field. These data represent the first evidence of mental rotation in a nonhuman species.     

阿拉伯数字与汉字大写数字认知的大脑功能一侧化实验研究

用半视野速示术检查阿拉伯数字和汉字大写数字在三种任务加工条件（认读、简单相加、奇偶概念异同判断）下进行认知的大脑两半球机能活动一侧化效应。结果表明：以被试正确反应的百分数为指标,两类数字的三种任务加工均没有表现出明显的视野（大脑半球）优势。以被试正确反应的反应时为指标,两类数字的认读和简单相加也未出现视野（大脑半球）的明显差别,而两类数字的奇偶概念异同判断却出现了差异显著的右视野（左半球）优势。     

Is Happy Facial Expression Identified by the Left or Right Hemisphere？

1IntroductionCorrectly identifying other people′s facial ex-pressions of emotions is important to human socialinteraction in all societies.Many studies suggestthat the identification of facial expressions in par-ticular and perceptual processing of emotional infor-mation is carried out mainly by the right hemi-sphere of the brain[1￣7].Damage to the righthemisphere generally produces more significant im-pairment in recognition of all facial expressions ofemotion than damage to the left hemisp…     

Lateral eyes or lateralized? Hemiretinal and ocular dominance effects on visual field asymmetries for the lexical decision task

The effects of hemiretinal stimulation and ocular dominance on a visual half-field lexical decision task were investigated. Twelve right-eyed and 12 left-eyed subjects made word/nonword decisions about stimuli presented in the left and right visual field under binocular, left-eye alone, and right-eye alone viewing conditions. Both accuracy (d') and response time measures were recorded. The nasal hemiretina advantage for response time and temporal hemiretina advantage for accuracy found for face recognition (Proudfoot, 1983, Brain and Cognition, 2, 25-31) were not present when lexical decisions were made. An overall right visual field advantage was present for both eye-dominance groups. The results support a hemispheric interpretation of visual field differences for the processing of words during lexical decision.     

A processing division on the recency axis: The selective effects of visual field,match type,and direction of reading on terminal and pre-terminal items in a letter matching task

Four experiments were conducted to evaluate the hypothesis that different processes are involved in decisions about terminal and pre-terminal items in a sequential item recognition task. The impetus for the investigation was previous findings that the matching of terminal and pre-terminal items to simultaneously presented bilateral probes yielded a right visual field (RVF) and left visual field (LVF) advantage respectively.Experiments 1 and 2 demonstrated that the interaction between match type and visual field, generally attributed to hemispheric specialization, is restricted to decisions about terminal items, while the left visual field advantage found for pre-terminal items was dependent on a left-to-right scanning strategy. Experiments 3 and 4 provided further evidence that a serial search through the probe set determined responses to pre-terminal items by showing that the effect was dependent on a varied mapping between stimuli and targets. When target items could be identified without a serial search through the memory set, the left visual field advantage for pre-terminal items was abolished.The results confirm that distinct processing principles are involved in decisions about terminal and pre-terminal items in recognition memory. They suggest that the process responsible for decisions about pre-terminal items involves a habit-controlled scanning mechanism operating serially on spatially distributed information. The process responsible for decisions about terminal items may be based on either: (a) hemispheric principles, or (b) a link between the content of attention and spatially distributed expectations.     

Electrodermal orienting responses to verbal and geometrical visual stimuli projected to the left or right retinal half-fields: sex differences

Using the visual half-field technique, verbal and geometrical slides were repeatedly projected to either the left or right visual field in an electrodermal orienting paradigm. Bilateral skin conductance response-magnitudes were recorded continuously over trials. Half the subjects (8 males and 8 females) had a verbal and a geometrical slide repeatedly presented to the right of a central fixation-point, (i.e. initial left hemisphere input) and the other half had the same kinds of stimuli presented to the left (i.e. initial right hemisphere input). There were 32 presentations of each stimulus, i.e. a total of 64 trials. The intertrial interval (ITI) varied between 25 to 40 sec. Results showed significantly larger response-magnitudes in the female group having the stimuli presented in the left visual field and especially to the geometrical slide. The same trend in data was also found for the male subgroup having the stimuli presented in the left visual field. No significant differences between the bilateral left and right hand recordings were foundin the main analysis. However, a closer inspection of the data indicated the left hand recording to be more sensitive than the right hand recording.     

刺激的知觉辨认难度与大脑两半球间的分布式加工

采用半视野速示术将标准刺激在中间视野呈现,比较刺激以不同偏心视角（3.5°,5°和6.5°）在左或右视野同时呈现,以检查不同偏心视角引起比较刺激知觉辨认难度的改变对汉字大写数字奇－偶概念同/异判断任务在大脑两半球间分布式加工的影响。结果显示：随偏心视角的增大正确反应时和错误百分数均显著提高;三种视角条件下左右手的正确反应时均有明显的右视野（左半球）优势;3.5°视角右视野（左半球）呈现时右手反应明显快于左手,5°视角右视野（左半球）与左视野（右半球）呈现时均为右手反应明显快于左手,6.5°视角右视野（左半球）与左视野（右半球）呈现时均为左手反应明显快于右手。这些结果提示：本研究条件下只有比较刺激在6.5°偏心视角呈现时刺激和反应可能出现大脑两半球间分布式加工,3.5°和5°视角呈现时可能为左半球单独加工。6.5°视角刺激呈现的分布加工明显由于大视角呈现时比较刺激辨认难度与注意要求的提高所致。     

Visual mislocalisation induced by translational and radial background motion

Three experiments were conducted to explore how translational and radial background motion affected visual localisation. In experiment 1, subjects were asked to indicate the apparent position of a small spot of light flashing against a background of vertical stripes, at a varying point in time before and after rapid translational motion of the background to the left or right. When the spot was flashed before the background motion, subjects mislocalised it toward the central fixation point. An interesting finding was that this mislocalisation occurred in most cases when the background moved in the direction opposite to the visual half-field in which the spot was flashed. That is to say, a spot flashed on the right side of the fixation point was mislocalised when its background moved to the left, and not when it moved to the right; and the converse was also true. In experiment 2, concentric circles were used as the background, and moved in a contracting or expanding direction. The results indicated that mislocalisation toward the central fixation point occurred when a spot was flashed before contracting motion of the background. The same mislocalisation was observed for the spot flashed in the lower visual field, but not when it was flashed in the upper visual field (experiment 3). It is concluded that the mislocalisation is a visual illusion induced by a transient background motion toward the central fixation point.