Left Visual Field Presentations Research Articles

Hemispheric Processing of Chinese Scientific Metaphors: Evidence via Hemifield Presentation.

The role of the two hemispheres in processing metaphoric language is controversial. In order to complement current debates, the current divided visual field (DVF) study introduced scientific metaphors as novel metaphors, presenting orientation mapping from the specific and familiar domains to the abstract and unfamiliar domains, to examine hemispheric asymmetry in metaphoric processing. Twenty-four Chinese native speakers from science disciplines took part in the experiment. The participants were presented with four types of Chinese word pairs: scientific metaphors, conventional metaphors, literal word pairs, and unrelated word pairs. The first word in each pair was presented centrally, and the second was presented to the left visual field (the Right Hemisphere) or the right visual field (the Left Hemisphere). Event-related potentials (ERPs) were recorded when participants read the target words and judged whether words in each pair were related. The data demonstrated that both hemispheres were involved at the initial stage of metaphor processing, but the right hemisphere took a more privileged role. The significant activation of the left hemisphere for scientific metaphoric processing supports the fine-coarse coding hypothesis. During right-visual-field presentation, the left hemisphere, responsible for the processing of closely related domains, has to integrate the loosely associated domains of scientific metaphor, which greatly increased cognitive taxes. Moreover, the data of late positive components (LPCs) revealed different hemispheric activation between scientific metaphors and conventional metaphors. Compared with literal pairs, conventional metaphors elicited significantly higher LPCs during right visual field presentation, while the scientific metaphor elicited significantly lower LPCs during left visual field presentation. These results suggest different processing mechanisms between novel metaphors and conventional metaphors and the special role of the right hemisphere in novel metaphoric processing at the later mapping stage.

Electrophysiological Correlates of Character Transposition in the Left and Right Visual Fields.

This study examined the brain activity elicited by the hemispheric asymmetries and morpheme transposition of two-character Chinese words (canonical and transposed word) and pseudowords using event-related potentials (ERPs) with a dual-target rapid serial visual presentation (RSVP) task. Electrophysiological results showed facilitation effects for canonical words with centrally presented visual field (CVF) and right visual field (RVF) presentations but not with left visual field (LVF) presentations, as reflected by less negative N400 amplitudes. Moreover, more positive late positive component (LPC) amplitudes were observed for both canonical words and transposed words irrespective of the visual fields. More importantly, transposed words elicited a more negative N400 amplitude and a less positive LPC amplitude compared with the amplitudes elicited by canonical words for CVF and RVF presentations. For LVF presentations, transposed words elicited a less negative N250 amplitude compared with canonical words, and there was no significant difference between canonical words and transposed words in the N400 effect. Taken together, we concluded that character transposition facilitated the mapping of whole-word orthographic representation to semantic information in the LVF, as reflected by the N250 component, and such morpheme transposition influenced whole-word semantic processing in CVF and RVF presentations, as reflected by N400 and LPC components.

Altered saccadic targets when processing facial expressions under different attentional and stimulus conditions

Depending on a subject’s attentional bias, robust changes in emotional perception occur when facial blends (different emotions expressed on upper/lower face) are presented tachistoscopically. If no instructions are given, subjects overwhelmingly identify the lower facial expression when blends are presented to either visual field. If asked to attend to the upper face, subjects overwhelmingly identify the upper facial expression in the left visual field but remain slightly biased to the lower facial expression in the right visual field. The current investigation sought to determine whether differences in initial saccadic targets could help explain the perceptual biases described above. Ten subjects were presented with full and blend facial expressions under different attentional conditions. No saccadic differences were found for left versus right visual field presentations or for full facial versus blend stimuli. When asked to identify the presented emotion, saccades were directed to the lower face. When asked to attend to the upper face, saccades were directed to the upper face. When asked to attend to the upper face and try to identify the emotion, saccades were directed to the upper face but to a lesser degree. Thus, saccadic behavior supports the concept that there are cognitive-attentional pre-attunements when subjects visually process facial expressions. However, these pre-attunements do not fully explain the perceptual superiority of the left visual field for identifying the upper facial expression when facial blends are presented tachistoscopically. Hence other perceptual factors must be in play, such as the phenomenon of virtual scanning.

Stability of right visual field advantage in an international lateralized lexical decision task irrespective of participants’ sex, handedness or bilingualism

ABSTRACTIn lateralized lexical decision tasks (LDTs), accuracy is higher and reaction times (RTs) are faster for right visual field (RVF) than left visual field (LVF) presentations. Visual field differences are thought to demonstrate the left hemisphere's (LH) dominance for language. The use of different tasks and words between studies and languages make direct comparisons difficult. We performed a lateralized LDT for which we selected four to six letter words that are used in three languages of Switzerland (French, German, and Italian) and English and Dutch. We accounted for the potential moderating roles of sex, handedness and multilingualism (early acquisition versus late acquisition of at least one second language). One hundred participants were tested at a French-speaking University in Switzerland. All performed a French vocabulary knowledge task [Brysbaert (2013). Lextale_FR a fast, free, and efficient test to measure language proficiency in French. Psychologica Belgica, 53(1), 23–27. Retrieved from http://hdl.handle.net/1854/LU-4373981]. Results showed a RVF over LVF advantage (accuracy, RTs and signal detection theory measures) for all groups, that is, irrespective of participants’ sex, handedness and how many languages they spoke. We observed, however, that enhanced vocabulary knowledge related to a right hemisphere shift in early bilinguals and a LH shift in late bilinguals. We discuss how the current observations can inform future studies suitable for the validation of the current task using an “international” vocabulary.

Event-related potentials reveal linguistic suppression effect but not enhancement effect on categorical perception of color.

The present study used the event-related potential technique to investigate the nature of linguistic effect on color perception. Four types of stimuli based on hue differences between a target color and a preceding color were used: zero hue step within-category color (0-WC); one hue step within-category color (1-WC); one hue step between-category color (1-BC); and two hue step between-category color (2-BC). The ERP results showed no significant effect of stimulus type in the 100-200 ms time window. However, in the 200-350 ms time window, ERP responses to 1-WC target color overlapped with that to 0-WC target color for right visual field (RVF) but not left visual field (LVF) presentation. For the 1-BC condition, ERP amplitudes were comparable in the two visual fields, both being significantly different from the 0-WC condition. The 2-BC condition showed the same pattern as the 1-BC condition. These results suggest that the categorical perception of color in RVF is due to linguistic suppression on within-category color discrimination but not between-category color enhancement, and that the effect is independent of early perceptual processes.

Word and pseudoword superiority effects in a shallow orthography language: the role of hemispheric lateralization.

The word superiority effect (WSE) has made it possible to demonstrate the automatic activation of lexical-orthographic entries in reading. The observation of this effect is important since it led to experimental support of the main cognitive reading models. These models were mostly developed on English data, hence the verification in different orthography systems is relevant. The present study tested WSE in Italian, a language in which this effect was predicted to be less constant given the highly consistent correspondence between orthography and phonology. Moreover, the presentation of the items in a lateralized visual field condition allowed testing of assumptions about the roles of the right and left hemispheres in written word recognition and, in particular, on the hemispheric lateralization of lexical processing. Two experiments were conducted with undergraduate students who had to recognize a target letter within a word, pseudoword, or nonword. In Experiment 1, prime and probe letters were in the same letter case, while in Experiment 2 they were in different letter cases. Error rates and reaction times were analyzed with mixed models. The results showed a superiority of pseudowords (pseudoword superiority effect; PSE) over illegal strings with no evidence of a clear superiority of words over pseudowords for both left and right visual field presentations. This suggests that in Italian, the sub-lexical route could play a major role in reading and that this route relies on a visual-perceptual orthographic coding concerning familiarity of letter combinations, which is also available to the right hemisphere.

Grammatical number agreement processing using the visual half-field paradigm: An event-related brain potential study

Despite indications in the split-brain and lesion literatures that the right hemisphere is capable of some syntactic analysis, few studies have investigated right hemisphere contributions to syntactic processing in people with intact brains. Here we used the visual half-field paradigm in healthy adults to examine each hemisphere's processing of correct and incorrect grammatical number agreement marked either lexically, e.g., antecedent/reflexive pronoun (“The grateful niece asked herself/*themselves…”) or morphologically, e.g., subject/verb (“Industrial scientists develop/*develops…”). For reflexives, response times and accuracy of grammaticality decisions suggested similar processing regardless of visual field of presentation. In the subject/verb condition, we observed similar response times and accuracies for central and right visual field (RVF) presentations. For left visual field (LVF) presentation, response times were longer and accuracy rates were reduced relative to RVF presentation. An event-related brain potential (ERP) study using the same materials revealed similar ERP responses to the reflexive pronouns in the two visual fields, but very different ERP effects to the subject/verb violations. For lexically marked violations on reflexives, P600 was elicited by stimuli in both the LVF and RVF; for morphologically marked violations on verbs, P600 was elicited only by RVF stimuli. These data suggest that both hemispheres can process lexically marked pronoun agreement violations, and do so in a similar fashion. Morphologically marked subject/verb agreement errors, however, showed a distinct LH advantage.

Sex hormonal modulation of interhemispheric transfer time

It is still a matter of debate whether functional cerebral asymmetries (FCA) of many cognitive processes are more pronounced in men than in women. Some evidence suggests that the apparent reduction in women's FCA is a result of the fluctuating levels of gonadal steroid hormones over the course of the menstrual cycle, making their FCA less static than for men. The degree of lateralization has been suggested to depend on interhemispheric communication that may be modulated by gonadal steroid hormones. Here, we employed visual-evoked EEG potentials to obtain a direct measure of interhemispheric communication during different phases of the menstrual cycle. The interhemispheric transfer time (IHTT) was estimated from the interhemispheric latency difference of the N170 component of the visual-evoked potential from either left or right visual field presentation. Nineteen right-handed women with regular menstrual cycles were tested twice, once during the menstrual phase, when progesterone and estradiol levels are low, and once during the luteal phase when progesterone and estradiol levels are high. Plasma steroid levels were determined by blood-based immunoassay at each session. It was found that IHTT, in particular from right-to-left, was generally longer during the luteal phase relative to the menstrual phase. This effect occurred as a consequence of a slowed absolute N170 latency of the indirect pathway (i.e. left hemispheric response after LVF stimulation) and, in particular, a shortened latency of the direct pathway (i.e. right hemispheric response after LVF stimulation) during the luteal phase. These results show that cycle-related effects are not restricted to modulation of processes between hemispheres but also apply to cortical interactions, especially within the right hemisphere. The findings support the view that plastic changes in the female brain occur during relatively short-term periods across the menstrual cycle.

The perirhinal cortex modulates V2 activity in response to the agreement between part familiarity and configuration familiarity

Research has demonstrated that the perirhinal cortex (PRC) represents complex object-level feature configurations, and participates in familiarity versus novelty discrimination. Barense et al. [(in press) Cerebral Cortex, 22:11, doi:10.1093/cercor/bhr347] postulated that, in addition, the PRC modulates part familiarity responses in lower-level visual areas. We used fMRI to measure activation in the PRC and V2 in response to silhouettes presented peripherally while participants maintained central fixation and performed an object recognition task. There were three types of silhouettes: Familiar Configurations portrayed real-world objects; Part-Rearranged Novel Configurations created by spatially rearranging the parts of the familiar configurations; and Control Novel Configurations in which both the configuration and the ensemble of parts comprising it were novel. For right visual field (RVF) presentation, BOLD responses revealed a significant linear trend in bilateral BA 35 of the PRC (highest activation for Familiar Configurations, lowest for Part-Rearranged Novel Configurations, with Control Novel Configurations in between). For left visual field (LVF) presentation, a significant linear trend was found in a different area (bilateral BA 38, temporal pole) in the opposite direction (Part-Rearranged Novel Configurations highest, Familiar Configurations lowest). These data confirm that the PRC is sensitive to the agreement in familiarity between the configuration level and the part level. As predicted, V2 activation mimicked that of the PRC: for RVF presentation, activity in V2 was significantly higher in the left hemisphere for Familiar Configurations than for Part-Rearranged Novel Configurations, and for LVF presentation, the opposite effect was found in right hemisphere V2. We attribute these patterns in V2 to feedback from the PRC because receptive fields in V2 encompass parts but not configurations. These results reveal two new aspects of PRC function: (1) it is sensitive to the congruency between the familiarity of object configurations and the parts comprising those configurations and (2) it likely modulates familiarity responses in visual area V2.

The role of saccade preparation in lateralized word recognition: Evidence for the attentional bias theory

Words presented to the right visual field (RVF) are recognized more readily than those presented to the left visual field (LVF). Whereas the attentional bias theory proposes an explanation in terms of attentional imbalance between visual fields, the attentional advantage theory assumes that words presented to the RVF are processed automatically while LVF words need attention. In this study, we exploited coupling between attention and saccadic eye movements to orient spatial attention to one or the other visual field. The first experiment compared conditions wherein participants had to remain fixated centrally or had to make a saccade to the visual field in which subsequent verbal stimuli were displayed. The orienting of attention by saccade preparation improved performance in a lexical decision task in both the LVF and the RVF. In the second experiment, participants had to make a saccade either to the visual field where verbal stimuli were presented subsequently or to the opposite side. For RVF as well as for LVF presentation, saccade preparation toward the opposite side decreased performance compared to the same side condition. These results are better explained by the attentional bias theory, and are discussed in the light of a new attentional theory dissociating two major components of attention, namely preparation and selection.

Lexical decision with left, right and center visual field presentation: a comparison between dyslexic and regular readers by means of electrophysiological and behavioral measures

This study examined the differences in processing between regular and dyslexic readers in a lexical decision task in different visual field presentations (left, right, and center). The research utilized behavioral measures that provide information on accuracy and reaction time and electro-physiological measures that permit the examination of brain activity during cognitive processing. Two groups of university students, regular and dyslexic readers, were matched on age, gender, intelligence, socioeconomic status, and handedness. A lexical decision task was used in order to examine the processes during word recognition. Subjects were required to decide whether a sequence of letters constituted a real word existing in spoken language or whether the stimulus seen was not an accurate word. For the behavioral measures, it was found that the dyslexics read slower and with more errors than the regular readers. Moreover, the ERP components appeared later in dyslexics as compared to regular readers in this task. The performance of the dyslexics improved and even approached that of the regular readers when the stimuli were presented to the left visual field. Thus, it seems that the dyslexics were relying more on their right hemisphere for linguistic processing, whereas the regular readers were relying more on their language areas in the left hemisphere.

Positive schizotypy scores correlate with left visual field interference for negatively valenced emotional words: A lateralized emotional Stroop study

Fourteen men scoring high and 14 men scoring low on a positive schizotypy scale participated in a lateralized emotional Stroop task. Vocal reaction times for color naming of neutral, positive and negative emotional words were recorded. Across participants, the color naming of neutral and emotional words was slightly faster to right than to left visual field presentations. In men with high scores on positive schizotypy, the presentation of negative words to the left visual field (right hemisphere) resulted in significant affective interference with color naming, which was significantly larger than in men with low scores. Correlational analysis also showed that positive schizotypy was significantly associated with emotional interference in response to LVF negative words. The outcome is discussed in terms of right hemispheric engagement in negative emotions in high positive schizotypic men.

Perceptual asymmetries influence task choice: The effect of lateralised presentation of hierarchical stimuli

The current study examined how hemispheric asymmetries in perceptual processing affect control processes associated with voluntary task choice during multitask behaviour. In a voluntary task-switching paradigm, where participants are free to choose which task to perform on each trial, participants identified either the global-or local-level features of hierarchical stimuli presented to either the left or right visual field. Hemispheric asymmetries in perception of lateralised hierarchical stimuli were evident in reaction times. Importantly, participants were more likely to categorise the stimulus in line with the processing efficiency of the hemisphere to which it was initially presented: the global task for left visual field presentation and the local task for right visual field presentation. Perceptual processing characteristics influence control processes associated with task choice in multitask environments.

Interhemispheric cooperation and non-cooperation during word recognition: Evidence for callosal transfer dysfunction in dyslexic adults

Participants report briefly-presented words more accurately when two copies are presented, one in the left visual field (LVF) and another in the right visual field (RVF), than when only a single copy is presented. This effect is known as the ‘redundant bilateral advantage’ and has been interpreted as evidence for interhemispheric cooperation. We investigated the redundant bilateral advantage in dyslexic adults and matched controls as a means of assessing communication between the hemispheres in dyslexia. Consistent with previous research, normal adult readers in Experiment 1 showed significantly higher accuracy on a word report task when identical word stimuli were presented bilaterally, compared to unilateral RVF or LVF presentation. Dyslexics, however, did not show the bilateral advantage. In Experiment 2, words were presented above fixation, below fixation or in both positions. In this experiment both dyslexics and controls benefited from the redundant presentation. Experiment 3 combined whole words in one visual field with word fragments in the other visual field (the initial and final letters separated by spaces). Controls showed a bilateral advantage but dyslexics did not. In Experiments 1 and 3, the dyslexics showed significantly lower accuracy for LVF trials than controls, but the groups did not differ for RVF trials. The findings suggest that dyslexics have a problem of interhemispheric integration and not a general problem of processing two lexical inputs simultaneously.

Brain State-dependent Functional Hemispheric Specialization in Men but not in Women

Hemispheric specialization is reliably demonstrated in patients with unilateral lesions or disconnected hemispheres, but is inconsistent in healthy populations. The reason for this paradox is unclear. We propose that functional hemispheric specialization in healthy participants depends upon functional brain states at stimulus arrival (FBS). Brain activity was recorded from 123 surface electrodes while 22 participants (11 women) performed lateralized lexical decisions (left hemisphere processing) on neutral and emotional (right hemisphere processing) words. We determined two classes of stable FBS, one with right anterior-left posterior orientations (RA-LP maps) and one with left anterior-right posterior orientations (LA-RP maps). Results show that functional hemispheric specialization is dependent upon the class of FBS and gender. Of those with LA-RP maps, only men showed a strong emotional word advantage (EWA) after left visual field (right hemisphere) presentation, but no EWA after right visual field (left hemisphere) presentation. Subsequent to all other brain states, there was an almost equal EWA after presentation to either visual field. Only about half of the FBS in men led to the pattern of functional hemispheric specialization. We suggest that 'split-brain' research may be marginally describable by a model, but only in exceptional situations, while in connected brains this functional hemispheric specialization is only one of many dynamic states.

Aggression in females is also lateralized: left-eye bias during aggressive courtship rejection in lizards

A small but taxonomically diverse number of vertebrates have a left-eye preference for aggression, but this has been shown only in males. Here we present data consistent with a left-eye preference for aggressive rejection display in females of the striped plateau lizard, Sceloporus virgatus. Already-mated females perform this display, which contains key elements of male–male aggressive displays, to courting males. Lateral eye placement reduces binocular vision of such displays. In a field study, we recorded the responses of individual gravid females to one of three possible stimulus presentations: a tethered conspecific male presented so the female viewed him (1) from a head-on (HO) position, (2) with her left visual field (LVF) or (3) with her right visual field (RVF). Although a small proportion of all trials yielded no response, females were significantly less likely to show any response in RVF presentations compared with HO or LVF presentations. In a large majority of trials, females responded to males, and almost all responding females displayed aggressively. When females displayed after RVF presentations, a female was equally likely to use her LVF or RVF to view the male when she first performed an aggressive rejection display. In contrast, in LVF and HO presentations where females displayed, females were significantly more likely than expected by chance to use their LVF to view the males when they displayed. Charge, a very aggressive act, also was significantly more likely to occur when females were viewing males with their LVF than their RVF or HO. Finally, in a small number of unmanipulated natural encounters we observed, all females used their LVF to display to courting males. Our results suggest that, as in males of several vertebrate species, females show a left-eye bias for conspecific aggression.

Word frequency and laterality effects in lexical decision: Right hemisphere mechanisms

Three experiments investigated the role of the right cerebral hemisphere in the word frequency effect observed in visual word recognition. The experiments examined lexical decisions to low and high frequency words as well as non-words in a divided visual field paradigm. Experiment 1 showed a significant word frequency effect only for left visual field presentation. Experiment 2 provided a partial replication of the results of Experiment 1 with a different set of words. In Experiment 3, case alternation was implemented to investigate a possible explanation of the findings. Results of the first experiment were replicated in the condition without case alternation. In the case-alternated condition, the word frequency effect was significant only for right visual field presentations. The present findings emphasize the need to consider that information processing strategies relevant to hemispheric asymmetries might account in part for the word frequency effect.

The effect of orthographic uniqueness and deviation points on lexical decisions: evidence from unilateral and bilateral-redundant presentations.

Words with an early or late orthographic uniqueness point and nonwords with an early or late orthographic deviation point were presented to the left, right, or both visual fields simultaneously. In Experiment 1, 20 participants made lexical decision judgements to horizontal stimulus presentations. In Experiment 2, a further 20 participants completed the task using vertical presentations to control for attentional biases. Consistent with previous research, words with earlier orthographic uniqueness points prompted faster responses across visual fields, regardless of stimulus orientation. Although research has suggested that the left hemisphere's superiority for language processing stems from a comparatively parallel processing strategy, with the right hemisphere reliant upon a serial mechanism, left and right visual field presentations were not differentially affected by orthographic uniqueness point. This suggests that differential sequential effects previously reported result during processes other than retrieval from the lexicon. The overall right visual field advantage observed using horizontal presentations disappeared when stimuli were presented vertically. Contrary to expectations, there was a facilitatory effect of late orthographic deviation point for horizontal nonword presentations. Overall, the results were interpreted as being consistent with predictions of a cohort model of word recognition, and they highlighted the effect of stimulus orientation on left and right hemisphere word recognition.

Microstate analysis of information processing in a reading task with Kanji and Katakana

The present study investigated the differences in time course and the brain electric signature during the reading process of two types of Japanese characters, Kanji (morphograms) and Katakana (syllabograms). We studied 18 right-handed Japanese females, healthy, informed volunteers. Subjects observed a sequence of Kanji and Katakana words, both consisting of two syllables for 50 ms in either the left visual field (LVF) or the right visual field (RVF) at intervals of 2000 ms, while 39-channel-EEG were recorded. Four average ERP map series were separately averaged using letter criterion and stimulus conditions for each subject. The ERPs from all conditions and subjects were averaged and segmented into microstates, which were quasi-stable landscapes of potential distribution maps. The microstate topographies were assessed numerically by the electric gravity center, a conservative estimate of the mean location of all intracerebral, active, electric sources. To assess the differences of the electric gravity center between Kanji and Katakana, the mean vector was compared between two conditions using a paired t-test. Significantly, different microstates were found between Kanji and Katakana. In the RVF presentation, Kanji were more right lateralized than Katakana at 178–262 ms, and in the LVF presentation, Kanji were also more right lateralized than Katakana at 214–338 ms. These temporal and spatial aspects suggest that the differences between Kanji and Katakana reading already appear at early information processing stages, and this difference was independent of the input hemisphere.

Picture the difference: electrophysiological investigations of picture processing in the two cerebral hemispheres

The nature of semantic memory and the role of the two cerebral hemispheres in meaning processing were examined using event-related brain potentials (ERPs) elicited by pictures in sentences. Participants read sentence pairs ending with the lateralized presentation of three target types: (1) expected pictures, (2) unexpected pictures from the expected semantic category, and (3) unexpected pictures from an unexpected category. ERPs to contextually unexpected pictures were more negative 350–500 ms (larger N400s) than those to expected pictures in both visual fields. However, while N400s to the two types of unexpected items did not differ with left visual field presentations, they were smaller to the unexpected items from the expected category with right visual field presentations. This pattern, previously observed to words [Brain Language 62 (1998) 149], suggests general differences in how the two hemispheres use context on-line. Other aspects of the N400 response—and effects on earlier ERP components—reveal differences between pictures and words, suggesting that semantic memory access is not modality-independent. The P2 component varied with ending type for right but not left visual field presentations, suggesting that the left hemisphere may use contextual information to prepare for the visual analysis of upcoming stimuli. Furthermore, there was clear evidence for an earlier negativity (“N300”), which varied with ending type but, unlike the N400, was unaffected by visual field of presentation. Overall, the results support our hypothesis that the left hemisphere actively uses top–down information to preactivate perceptual and semantic features of upcoming stimuli, while the right hemisphere adopts a “wait and see” integrative approach.