Right Hemisphere Advantage Research Articles

Empirical study of Kanji as archetypal images: understanding the collective unconscious as part of the Japanese language

Chinese characters originated as a semiotic system independent from spoken language and in the Japanese language they function non-phonetically with speakers exhibiting right-hemispheric advantage in their processing. We tested the hypothesis that Chinese characters are archetypal images and therefore part of our collective unconscious memory. Our study builds on the first empirical study of archetypal memory of Rosen et al. (1991) which demonstrated that archetypal symbols presented matched with their correct meaning were better learned and recalled. In a series of three experiments we used 40 Chinese characters instead of the archetypal symbols used by Rosen, et al. (1991). The results provided empirical evidence that Chinese characters matched with their correct meaning were significantly better recalled than the ones that were mismatched. Thus, we demonstrated that there appears to be unconscious knowledge of the meaning of the Chinese characters which was triggered as a result of priming when the characters were correctly matched with their meaning. On this basis, we suggest that Chinese characters exhibit the same cognitive qualities as archetypal symbols. Thus, in the Japanese language an archetypal image is integrated non-phonetically into the system of language and signifies the concept independent from the phonetic signifier and is equal to it.

Change Detection in Complex Scenes: Hemispheric Contribution and the Role of Perceptual and Semantic Factors

The perceptual salience and semantic relevance of objects for the meaning of a scene were evaluated with multiple criteria and then manipulated in a change-detection experiment that used an original combination of one-shot and tachistoscopic divided-visual-field paradigms to study behavioural hemispheric asymmetry. Coloured drawings that depicted meaningful situations were presented centrally and very briefly (120 ms) and only the changes were lateralised by adding an object in the right or in the left visual hemifield. High salience and high relevance improved both response times (RTs) and accuracy, although the overall contribution of salience was greater than that of relevance. Moreover, only for low-salience changes did relevance affect speed. RTs were shorter when a change occurred in the left visual hemifield, suggesting a right-hemisphere advantage for detection of visual change. Also, men responded faster than women. The theoretical and methodological implications are discussed.

Lateralization of spatial categories: A comparison of verbal and visuospatial categorical relations

Many reports show that spatial relations between and within objects show differences in hemispheric lateralization. Coordinate, metric relations concerning distances are processed with a right-hemisphere advantage, whereas a left-hemisphere advantage is thought to be related to categorical, abstract relations (Kosslyn, 1987). Kemmerer and Tranel (2000) argued that the left-hemisphere advantage for categorical processing might apply only for verbal spatial categories, however, whereas a right-hemisphere advantage is related to visuospatial categories. To test this idea, we examined categorical processing for stimuli in both verbal and visuospatial formats, with a visual half-field, match-to-sample design. In Experiment 1, we manipulated the format of the second stimulus to compare response patterns for both verbal and visuospatial stimuli. In Experiment 2, we varied the expectancy of the format of the second stimulus, allowing for an assessment of strategy use. The results showed that a left-hemisphere advantage was related to verbal stimulus format only, but not in all conditions. A right-hemisphere advantage was found only with a visuospatial expectancy, visuospatial format, and brief interval. The theory we present to explain these results proposes that the lateralization related to basic categorical processing can be strongly influenced by verbal characteristics and, to some extent, by additional coordinate processing. The lateralization measured in such cases does not represent lateralization related purely to categorical processing, but to these additional effects as well. This stresses the importance of careful task and stimulus design when examining categorical processing in order to reduce the influence of those additional processes.

Dissociation between eye-movements and right perceptual biases in chimeric face processing in right hemisphere lesioned patients

Using blended chimeric facial stimuli, where the left and the right sides of the face are different, we have previously shown that both young and older observers tend to bias their responses significantly toward the information on the left, supposedly reflecting a right-hemisphere advantage in this task (Butler, Gilchrist, Burt, Perrett, Jones & Harvey, 2005, Neuropsychologia, 43, 52-59; Harvey & Butler, 2004, Perception, 33, 106). Analyses of the eye movement patterns further indicated a tendency for both groups to initially scan to the left side of the chimeric image, presumably reflecting the tendency to first inspect the side of the face better suited to face analysis (left side of face/right hemisphere). As expected, patients with right hemisphere lesions based their gender decisions mainly on the right side of the chimeric face and this was not only the case for patients who suffered from spatial neglect (Mattingley, Bradshaw, Phillips, Bradshaw, 1993, Brain and Cognition, 23, 145-165). More interestingly though, there was no clear relationship between perceptual and eye-movements biases to chimeric stimuli. Although most patients showed more right-sided saccades and longer rightward fixations this was not necessarily reflected in the rightward perceptual bias. One patient in particular showed rightward saccades only, yet based his gender decision on the left hemi-face half the time when he should have shown 100% rightward hemi-face judgements. We would argue that although in healthy subjects face biases and eye-movement biases are tightly coupled, this relationship breaks down with brain damage and that for such patients eye-movement patterns are not a good indicator of perceptual processing (see also Ferber, Danckert, Joanisse, Goltz, Goodale, 2003, Neurology, 60 1826-1829 and Harvey, Olk, Muir, K, 2003, Neuropsychologia, 41, 1114-1121 for supporting evidence).

Mirror-image discrimination and reversal in the disconnected hemispheres

Two callosotomized patients and 24 neurologically normal subjects performed simple binary discriminations between upright letters flashed in one or other visual field. Where discrimination of the letters F and R by name either showed a left-hemisphere advantage or no hemispheric effect, discrimination of whether the same letters were normal or backward showed a right-hemisphere advantage. These results suggest that discrimination of mirror-image letters depends on matching to an exemplar, for which the right-hemisphere is dominant, while letter naming depends on abstract category recognition. One commissurotomized patient, DDV, showed systematic left–right reversal of the letters in the left visual field, classifying the normal letters as reversed and reversed ones as normal, and persisted with this reversal when the letters were shown in free vision. This suggests that reversed exemplars of the letters may be laid down the right cerebral hemisphere. There was no such reversal in the other patient (DDC).

On Why Left Events are the Right Ones: Neural Mechanisms Underlying the Left-hemifield Advantage in Rapid Serial Visual Presentation

When simultaneous series of stimuli are rapidly presented left and right, containing two target stimuli T1 and T2, T2 is much better identified when presented in the left than in the right hemifield. Here, this effect was replicated, even when shifts of gaze were controlled, and was only partially compensated when T1 side provided the cue where to expect T2. Electrophysiological measurement revealed earlier latencies of T1- and T2-evoked N2(pc) peaks at the right than at the left visual cortex, and larger right-hemisphere T2-evoked N2(pc) amplitudes when T2 closely followed T1. These findings suggest that the right hemisphere was better able to single out the targets in time. Further, sustained contralateral slow shifts remained active after T1 for longer time at the right than at the left visual cortex, and developed more consistently at the right visual cortex when expecting T2 on the contralateral side. These findings might reflect better capacity of right-hemisphere visual working memory. These findings about the neurophysiological underpinnings of the large right-hemisphere advantage in this complex visual task might help elucidating the mechanisms responsible for the severe disturbance of hemineglect following damage to the right hemisphere.

Hemispheric asymmetries in discourse processing: Evidence from false memories for lists and texts

Previous research suggests that the right hemisphere (RH) may contribute uniquely to discourse and text processing by activating and maintaining a wide range of meanings, including more distantly related meanings. The present study used the word-lists false memory paradigm [Roediger, H. L., III, & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 803–814.] to examine the hypothesis that difference between the two cerebral hemispheres in discourse processing may be due, at least partly, to memory representations for implicit text-related semantic information. Specifically, we tested the susceptibility of the left hemisphere (LH) and RH to unpresented target words following the presentation of semantically related words appearing in either word lists or short texts. Findings showed that the RH produced more false alarms than the LH for unpresented target words following either word lists or texts. These findings reveal hemispheric differences in memory for semantically related information and suggest that RH advantage in long-term maintenance of a wide range of text-related word meanings may be one aspect of its unique contribution to the construction of a discourse model. The results support the RH coarse semantic coding theory [Beeman, M. (1998). Coarse semantic coding and discourse comprehension. In M. Beeman & C. Chiarello (Eds.), Right hemisphere language comprehension: Perspectives from cognitive neuroscience (pp. 255–284). Mahwah, NJ: Erlbaum.] and suggest that hemispheric differences in semantic processing during language comprehension extend also to verbal memory.

A bias for the female face in the right hemisphere

In the present study we assessed the contribution of the two hemispheres to the attribution of gender of faces in male and female observers. Normal and chimeric faces were presented in their canonical orientation and upside-down in a tachistoscopic paradigm. Chimeric faces were composed of two halves (left and right) obtained from photos of individuals of the same sex or from individuals of different sexes. All faces were presented tachistoscopically with a central fixation, the two halves falling in the two visual fields of the observer, who was required to rapidly judge the sex of the face. A left half-face (right-hemispheric) bias for gender attribution with upright faces was observed both in male and female participants, as previously reported. Strikingly, however, the bias depended entirely on female-left/male-right chimeras, revealing a right-hemispheric advantage for the recognition of female faces. The results are discussed in the light of a behavioural bias during development (i.e., maternal cradling).

Investigations of hemispheric specialization of self-voice recognition

Three experiments investigated functional asymmetries related to self-recognition in the domain of voices. In Experiment 1, participants were asked to identify one of three presented voices (self, familiar or unknown) by responding with either the right or the left-hand. In Experiment 2, participants were presented with auditory morphs between the self-voice and a familiar voice and were asked to perform a forced-choice decision on speaker identity with either the left or the right-hand. In Experiment 3, participants were presented with continua of auditory morphs between self- or a familiar voice and a famous voice, and were asked to stop the presentation either when the voice became “more famous” or “more familiar/self”. While these experiments did not reveal an overall hand difference for self-recognition, the last study, with improved design and controls, suggested a right-hemisphere advantage for self-compared to other-voice recognition, similar to that observed in the visual domain for self-faces.

The development of categorical and coordinate spatial relations

Two classes of spatial relations can be distinguished in between and within object representations. Kosslyn [Kosslyn, S. M. (1987). Seeing and imagining in the cerebral hemispheres: A computational approach. Psychological Review, 94, 148–175] suggested that the right hemisphere (RH) is specialized for processing coordinate (metric) spatial information and the left hemisphere (LH) processes categorical (abstract) information more effectively. The present study examined the developmental pattern of spatial relation processing in 6–8-year old, 10–12-year old and adults. Using signal detection analyses we calculated sensitivity and bias scores for all age groups. The results indicated that older children and adults showed a greater response bias than younger children. Also, discrimination sensitivity for spatial relation changes clearly improved with age. For the oldest children (10–12-year old) and adults this improvement was accompanied by a RH specialization. In contrast with Kosslyn's claim, this RH advantage also applied to the processing of categorical spatial information. The results are discussed in terms of a right hemispheric specialization for spatial relation processing which matures with age.

Night-time right hemisphere superiority and daytime left hemisphere superiority: A repatterning of laterality across wake–sleep–wake states

During the sleep onset period (SOP), there is a state-specific relative advantage of the right hemisphere (RH). This superiority could either be due to the ability of the RH when operating at levels of reduced arousal, as suggested by its superiority in sustaining vigilance, or it could depend on a more pronounced homeostatic deactivation of the left hemisphere (LH). To evaluate whether variations of lateralization from wake to sleep are consistent with one of these two hypotheses, we considered a finger tapping task (FTT) bimanually performed during two wakeful conditions, during the SOP, upon experimental awakenings from stage 2 and REM sleep in the first and in the second part of the night, and upon morning awakening. The RH advantage in sustaining vigilance would be supported if the relative RH advantage was present throughout the sleep period. Finding that the repatterning of hemispheric asymmetry is present and/or prominent in the first part of the night would support the homeostatic hypothesis, i.e. when the homeostatic process is more pronounced. Results from 16 subjects revealed a significant superiority of the LH during the two wakeful conditions. At sleep onset, a clear reversal of dominance was observed and it was followed by a steady RH superiority upon both REM and NREM sleep awakenings, and upon the morning sleep–wake transition. Therefore, performance in a FTT reveals a repatterning of laterality across wake–sleep–wake states. These results are interpreted as consistent with the hypothesis concerning an advantage of the RH in sustaining vigilance.

Predicting therapeutic response to secondary treatment with bupropion: Dichotic listening tests of functional brain asymmetry

Studies using neuroimaging, electrophysiologic and cognitive measures have raised hopes for developing predictors of therapeutic response to antidepressants. Pretreatment measures of functional brain asymmetry have been found to be related to response to the selective serotonin reuptake inhibitor fluoxetine. This report examines the extent to which dichotic listening tests also predict clinical response to an antidepressant with a different mechanism of action, i.e., bupropion. Dichotic listening data were obtained for 17 unmedicated depressed patients who were subsequently treated with bupropion. Right-handed outpatients were tested on dichotic fused-words and complex-tones tests. Seven patients who responded to bupropion and 10 nonresponders did not differ in gender, age or education. Bupropion responders had significantly larger left-hemisphere advantage for perceiving words when compared to nonresponders, but there was no difference in their right-hemisphere advantage for tones. All patients having a left-hemisphere advantage above the normal mean responded to bupropion, whereas only 9% of patients below the normal mean responded to treatment. These findings should encourage further study of the clinical value of dichotic listening and other measures of functional brain asymmetry for identifying depressed patients who most benefit from treatment with different classes of antidepressants.

Right hemisphere sensitivity to novel metaphoric relations: Application of the signal detection theory

The present study used the signal detection theory to test the hypothesis that the right hemisphere (RH) is more sensitive than the left hemisphere (LH) to the distant semantic relations in novel metaphoric expressions. In two divided visual field experiments, sensitivity ( d′) and criterion ( β) were calculated for responses to different types of word pairs. In the first experiment, subjects were presented with unfamiliar two-word novel metaphoric expressions (“signal”) and unrelated word-pairs (“noise”). In the second experiment, literal expressions (“signal”) and unrelated word pairs (“noise”) were presented. In line with the Coarse Semantic Coding Theory [Beeman, M. (1998). Coarse semantic coding and discourse comprehension. In: M. Beeman & C. Chiarello (Eds.). Right hemisphere language comprehension: Perspectives from cognitive neuroscience. Mahwah, NJ: Erlbaum, pp. 255-284.] as well as with the Graded Salience Hypothesis [Giora, R. (2003). On our mind: Salience, context and figurative language. New York: Oxford University Press.], the findings suggest that the RH is more sensitive than the LH to unfamiliar metaphoric relations. Furthermore, this RH advantage in processing distant semantic relations did not extend to familiar semantic relations.

Functional cerebral asymmetry in auditory motion perception

Several studies have shown a right-hemispheric advantage for sound localisation. However, most of these studies used stationary sound stimuli, although in most everyday situations humans are in motion when localising sound, or face a moving sound source. To elucidate the question of a functional asymmetry in cortical processing of auditory motion information, we tested 23 neurologically healthy human participants. Virtual leftward or rightward motion (broadband noise) was presented with variable movement angles (MA) in the horizontal plane (via headphones) in either the participants’ left or right hemispace. Participants had to indicate whether the sound moved left or rightward. The frequency of “right” judgements determined as a function of MA had a sigmoidal shape in both hemispaces, indicating significant overall discrimination of motion direction. However, the frequency of correct judgements revealed a significantly better performance for the left than for the right hemispace, suggesting a superiority of the right hemisphere. This finding is in agreement with recent neuroimaging results showing higher right-hemispheric activity during localisation of moving sounds. The results might also point to a supramodal right-hemisphere advantage in the attentional processing of motion perception.

Hemispheric asymmetries for the conscious and unconscious perception of emotional words

The current research examines the interactions between hemispheric asymmetries for visual perception and emotion. In a series of four experiments, participants completed tasks measuring both conscious and unconscious perception of linguistic stimuli. In these studies, stimulus-presentation parameters (brief exposure duration vs masking) and the emotional valence of the test stimuli (negative vs positive) were manipulated in order to create studies in which the visual and emotional asymmetries were congruent (favoured the same hemispheres) or were incongruent (favoured opposing hemispheres). The results demonstrated that negative emotional stimuli led to a right-hemisphere advantage for conscious perception only when stimuli were shown for brief exposures (17 ms). Positive emotional words did not elicit hemispheric asymmetries. The results are discussed in terms of their relevance for theories of emotional lateralisation.

Affective and cognitive modulation of performance monitoring: Behavioral and ERP evidence

This study investigates the effects of negative affect on performance monitoring. EEG was acquired during a lateralized, numeric Stroop working memory task that featured task-irrelevant aversive and neutral pictures between stimuli. Performance accuracy showed a right-hemisphere advantage for stimuli that followed aversive pictures. Response-locked event-related potentials (ERPs) from accurate trials showed an early negative component (CRN; correct response/conflict-related negativity) followed by a positive wave comparable to the Pe (error positivity). The CRN was bi-peaked with an earlier peak that was sensitive to aversive pictures during early portions of the experiment and a later peak that increased with error likelihood later in the experiment. Pe amplitude was increased with aversive pictures early in the experiment and was sensitive to picture type, Stroop interference, and hemisphere of stimulus delivery during later trials. This suggests that ERP indices of performance monitoring, the CRN and Pe, are dynamically modulated by both affective and cognitive demands.

An examination of the right-hemisphere hypothesis of the lateralization of emotion

The Right-Hemisphere Hypothesis posits that emotional stimuli are perceived more efficiently by the right hemisphere than by the left hemisphere. The current research examines this hypothesis by examining hemispheric asymmetries for the conscious and unconscious perception of emotional stimuli. Negative, positive, and neutral words were presented for 17 ms to one visual field or the other. Conscious perception was measured by using a subjective report-of-awareness measure reported by participants on each trial. Unconscious perception was measured using an “exclusion task,” a form of word-stem-completion task. Consistent with previous research, there was a right-hemisphere advantage for the conscious perception of negative information. As in previous studies, this advantage for conscious perception occurred at the expense of unconscious perception. Specifically, there was a right-hemisphere inferiority for the unconscious perception of negative information. Contrary to the predictions of the Right-Hemisphere Hypothesis, there were no hemispheric asymmetries for the perception of positive emotional information, thus suggesting that the Right-Hemisphere Hypothesis may not be applicable to all behavioral studies.

Sex differences in spatial ability: A lateralization of function approach

The current study was designed to examine whether the extent of the male advantage in performance on a spatial task was determined by the extent to which the task was right-hemisphere dependent. Participants included 108 right-handed men and women who completed the mental rotation, waterlevel, and paperfolding tasks, all of which were presented bilaterally. The results partially supported the hypothesis. On the mental rotation task, men showed a right-hemisphere advantage, whereas women showed no hemispheric differences; however, no overall sex differences were observed. On the waterlevel task, men outperformed women, and both men and women showed a right-hemisphere advantage. On the paperfolding task, no sex or hemispheric differences were observed. Although the findings of the current study were mixed, the study provides a framework for examining sex differences across different types of spatial ability.

Neural activity associated with metaphor comprehension: spatial analysis

Though neuropsychological data indicate that the right hemisphere (RH) plays a major role in metaphor processing, other studies suggest that, at least during some phases of this processing, a RH advantage may not exist. The present study explores, through a temporally agile neural signal—the event-related potentials (ERPs)—, and through source-localization algorithms applied to ERP recordings, whether the crucial phase of metaphor comprehension presents or not a RH advantage. Participants ( n = 24) were submitted to a S1–S2 experimental paradigm. S1 consisted of visually presented metaphoric sentences (e.g., “Green lung of the city”), followed by S2, which consisted of words that could (i.e., “Park”) or could not (i.e., “Semaphore”) be defined by S1. ERPs elicited by S2 were analyzed using temporal principal component analysis (tPCA) and source-localization algorithms. These analyses revealed that metaphorically related S2 words showed significantly higher N400 amplitudes than non-related S2 words. Source-localization algorithms showed differential activity between the two S2 conditions in the right middle/superior temporal areas. These results support the existence of an important RH contribution to (at least) one phase of metaphor processing and, furthermore, implicate the temporal cortex with respect to that contribution.

Qualitative differences in the representation of spatial relations for different object classes.

Two experiments investigated whether the representations used for animal, produce, and object recognition code spatial relations in a similar manner. Experiment 1 tested the effects of planar rotation on the recognition of animals and nonanimal objects. Response times for recognizing animals followed an inverted U-shaped function, whereas those for basic-level object recognition followed an M-shaped function (with a dip at 1800). Experiment 2 tested for laterality effects in the recognition of animals, produce, and objects. A right-hemisphere advantage was found for recognizing animals, whereas no hemispheric advantages were found for recognizing produce or objects. These results suggest that the recognition of animals with nonunique structural descriptions is mediated using coordinate spatial relations, whereas most forms of basic-level object recognition are mediated using categorical spatial relations.