Hemispheric Processing Research Articles

The neural correlates of impaired collision avoidance in hemianopic patients

The aim of this study was to assess the brain regions associated with impaired performance in a virtual, dynamic collision avoidance task, in a group of patients with homonymous visual field defects (HVFDs) because of unilateral vascular brain lesions. Overall task performance was quantitatively assessed as the number of collisions while crossing an intersection at two levels of traffic density. Twenty-six patients were divided into two subgroups using the median split method: patients with 'performance above average' (HVFD(A), i.e. lower number of collisions) and patients with 'performance below average' (HVFD(B), i.e. higher number of collisions). In order to identify the anatomical structures that might be specifically affected in HVFD(B) patients but spared in HVFD(A) patients, overlap, subtraction and voxel-based lesion-symptom mapping analyses were performed using the MRIcron software. No significant difference in collision avoidance between patients with left- and right-hemispheric lesions was revealed. Separate lesion analysis in 12 patients with right- and 14 patients with left-hemispheric lesions showed that the cortical structures associated with impaired collision avoidance were the parieto-occipital region and posterior cingulate gyrus in the right hemisphere and the inferior occipital cortex and parts of the fusiform (occipito-temporal) gyrus in the left hemisphere. In the present collision avoidance paradigm, impaired performance of patients with right-hemispheric lesions is associated with damage in the dorsal processing stream and potential impact on the visual spatial working memory (WM), while impaired performance of patients with left-hemispheric lesions is associated with damage in the ventral stream and potential impact on the visual object WM.

A new method for selectively enhancing hemisphere processing: Voice frequency amplification influences the strength of attribute framing

An attribute framing effect occurs when positive or negative associations produced by positive or negative frames are mapped onto evaluations resulting in a more favourable evaluation for the positively framed attribute. We used a new voice frequency manipulation to differentially enhance right versus left hemisphere processing. In doing so we found a strong attribute framing effect when a speaker with a low-frequency voice enhanced the contextual processing style of the right hemisphere. However, a framing effect was not obtained when a speaker with a high-frequency voice enhanced the inferential/analytical processing style of the left hemisphere. At the theoretical level our results provide evidence that the contextual processing style of the right hemisphere is especially susceptible to associative implications, such as those found in attribute framing manipulations. At the applied level we provide a simple method for altering the effectiveness of persuasion messages.

A “concrete view” of aging: Event related potentials reveal age-related changes in basic integrative processes in language

Normal aging is accompanied by changes in both structural and functional cerebral organization. Although verbal knowledge seems to be relatively stable across the lifespan, there are age-related changes in the rapid use of that knowledge during on-line language processing. In particular, aging has been linked to reduce effectiveness in preparing for upcoming words and building an integrated sentence-level representation. The current study assessed whether such age-related changes extend even to much simpler language units, such as modification relations between a centrally presented adjective and a lateralized noun. Adjectives were used to elicit concrete and abstract meanings of the same, polysemous lexical items (e.g., “green book” vs. “interesting book”). Consistent with findings that lexical information is preserved with age, older adults, like younger adults, exhibited concreteness effects at the adjectives, with more negative responses to concrete adjectives over posterior (300–500 ms; N400) and frontal (300–900 ms) channels. However, at the noun, younger adults exhibited concreteness-based predictability effects linked to left hemisphere processing and imagery effects linked to right hemisphere processing, contingent on whether the adjectives and nouns formed a cohesive conceptual unit. In contrast, older adults showed neither effect, suggesting that they were less able to rapidly link the adjective–noun meaning to form an integrated conceptual representation. Age-related changes in language processing may thus be more pervasive than previously realized.

Hemispheric processing of inferences during text comprehension: The role of consistency and task difficulty

Although the hemispheres likely carry out different processes during reading, currently little is known about how the consistency effect and the difficulty of the task influences hemispheric processing during text comprehension. In the current study participants read texts promoting an inference, and performed a lexical decision task to inference-related targets presented to the left visual field–right hemisphere or the right visual field–left hemisphere. To manipulate the consistency of information targets were either consistent or inconsistent with the inference. To manipulate difficulty the antecedent and its referent were either separated by two sentences (i.e., the less-difficult condition) or four sentences (i.e., the more-difficult condition). In the consistent condition facilitation was greater in the left hemisphere than the right hemisphere. In the inconsistent condition facilitation was greater in the right hemisphere than the left hemisphere. When analyses were combined across conditions, consistent targets showed greater facilitation in the left hemisphere than in the right hemisphere. Interestingly the level of difficulty did not mediate how the hemispheres process inferences. The current findings suggest that the consistency of information, rather than the difficulty of a task, primarily influences inference generation in the cerebral hemispheres.

Event-Related Potential Correlates of Performance-Monitoring in a Lateralized Time-Estimation Task

Performance-monitoring as a key function of cognitive control covers a wide range of diverse processes to enable goal directed behavior and to avoid maladjustments. Several event-related brain potentials (ERP) are associated with performance-monitoring, but their conceptual background differs. For example, the feedback-related negativity (FRN) is associated with unexpected performance feedback and might serve as a teaching signal for adaptational processes, whereas the error-related negativity (ERN) is associated with error commission and subsequent behavioral adaptation. The N2 is visible in the EEG when the participant successfully inhibits a response following a cue and thereby adapts to a given stop-signal. Here, we present an innovative paradigm to concurrently study these different performance-monitoring-related ERPs. In 24 participants a tactile time-estimation task interspersed with infrequent stop-signal trials reliably elicited all three ERPs. Sensory input and motor output were completely lateralized, in order to estimate any hemispheric processing preferences for the different aspects of performance monitoring associated with these ERPs. In accordance with the literature our data suggest augmented inhibitory capabilities in the right hemisphere given that stop-trial performance was significantly better with left- as compared to right-hand stop-signals. In line with this, the N2 scalp distribution was generally shifted to the right in addition to an ipsilateral shift in relation to the response hand. Other than that, task lateralization affected neither behavior related to error and feedback processing nor ERN or FRN. Comparing the ERP topographies using the Global Map Dissimilarity index, a large topographic overlap was found between all considered components.With an evenly distributed set of trials and a split-half reliability for all ERP components ≥.85 the task is well suited to efficiently study N2, ERN, and FRN concurrently which might prove useful for group comparisons, especially in clinical populations.

Hemispheric resource availability influences face perception: A multiple resource approach to social perception

Two experiments tested the hypothesis that social perception recruits distinct limited-capacity processing resources that are distinguished by the cerebral hemispheres. To test this hypothesis, social perception efficiency was assessed after relevant hemispheric processing resources were depleted. In Experiment 1 prime faces were unilaterally presented for 30 ms, after which centrally presented target faces were categorised by sex. In Experiment 2 prime faces were unilaterally presented for 80 ms after which centrally presented target faces were categorised by fame. Results showed that sex categorisation was slower after primes were presented in the right versus left visual field, and that fame categorisation was slower after familiar primes were presented in the left versus right visual field. The results support a multiple resource account of social perception in which the availability of resources distributed across the cerebral hemispheres influences social perception.

Laterality and sex differences in tactile detection and two-point thresholds modified by body surface area and body fat ratio

Tactile detection and two-point discrimination tests are commonly used in neurological examinations. However, questions remain about the influence of both body and patient characteristics on test thresholds. The left side of the body has sometimes been reported more tactilely sensitive than the right, and females are said to be more sensitive than males. We measured tactile detection and two-point discrimination thresholds on the finger, palm, and forehead of a large sample of young adults (N = 171), examining laterality and sex differences, and the effects of body surface area (BSA) and body fat ratio (BFR). In tactile detection, there were no effects of laterality, BSA, or BFR, although females had lower thresholds than males. In two-point discrimination, there was an effect of laterality, with lower thresholds on the left side. This probably reflects hemispheric spatial processing differences. A significant BFR effect implies that subcutaneous fat affects skin deformation, but there were no effects of sex or BSA. The two-point discrimination findings differ in several respects from recent findings using grating orientation discriminations. A small positive correlation between the tasks, falling far short of test–retest reliabilities, indicates that they use largely disjoint but partially overlapping processes.

Native and nonnative processing of Japanese pitch accent

ABSTRACTThe theoretical framework of this study is based on the prevalent debate of whether prosodic processing is influenced by higher level linguistic-specific circuits or reflects lower level encoding of physical properties. Using the dichotic listening technique, the study investigates the hemispheric processing of Japanese pitch accent by native Japanese listeners and two groups of nonnative listeners with no prior pitch accent experience but differing in their native language experience with linguistic pitch: native listeners of Mandarin (a tone language with higher linguistic functional use of pitch) and native listeners of English (a stress language with lower functional use of pitch). The overall results reveal that, for both native and nonnative listeners, the processing of Japanese pitch accent is less lateralized (compared to lexical tone processing, which has been found to be a left hemisphere property). However, detailed analysis with individual pitch accents across groups shows a right hemisphere preference for processing the high–accent–low (H*L) pattern, a left hemisphere preference for LH*, and no hemisphere dominance for LH, indicating a significant reliance on the acoustic cues. These patterns are particularly prominent with the English listeners who are least experienced with linguistic pitch. Together, the findings suggest an interplay of linguistic and acoustic aspects in the processing of Japanese pitch accent by native and nonnative listeners.

Running Head: Hemispheric Processing of Slogans Brand Familiarity in Advertisement Slogans: The Role of the Left and Right Cerebral Hemispheres

Previous research shows that brand familiarity can affect purchase behavior, such that a familiar brand will be preferred over a less familiar brand. Previous research also shows that the use of metaphoric advertisements increases purchase intent. However, it is unknown how consumers implicitly process familiar brands when reading advertisements. Through the divided visual field paradigm, we investigated how the left and right cerebral hemispheres process familiar brands when presented with advertisement slogans. Participants in this experiment read familiar brand names and were presented with metaphoric, literal, or neutral slogans. Participants responded to related target words briefly shown to either the right or left hemisphere. The right hemisphere showed greater facilitation for literal than for metaphoric slogans when consumers were presented with familiar brands. Purchase intent ratings were higher when targets were presented to the left hemisphere. These findings suggest that brand familiarity influences consumers’ processing of slogans in the right hemisphere and affects purchase intent ratings in the left hemisphere.

Sniffing with the right nostril: lateralization of response to odour stimuli by dogs

Lateralization in dogs, Canis familiaris, has been reported for paw usage and response to visual and acoustic stimuli. Surprisingly, however, no investigation of possible lateralization for the most relevant sensory domain of dogs, namely olfaction, has been carried out. Here we investigated left and right nostril use in dogs freely sniffing different emotive stimuli in unrestrained conditions. When sniffing novel nonaversive stimuli (food, lemon, vaginal secretion and cotton swab odours), dogs showed initial preferential use of the right nostril and then a shift towards use of the left nostril with repeated stimulus presentation. When sniffing arousal stimuli such as adrenaline and veterinary sweat odorants, dogs showed a consistent right nostril bias all over the series of stimulus presentations. Results suggest initial involvement of the right hemisphere in processing of novel stimuli followed by the left hemisphere taking charge of control of routine behaviour. Sustained right nostril response to arousal stimuli appears to be consistent with the idea that the sympathetic hypothalamic–pituitary–adrenal axis is mainly under the control of the right hemisphere. The implications of these findings for animal welfare are discussed.

Anarchic-hand syndrome: ERP reflections of lost control over the right hemisphere

In patients with the callosal type of anarchic-hand syndrome, the left hand often does not act as intended and counteracts the right hand. Reports are scarce about the underlying neurophysiological mechanisms. We report the case G.H. who developed the syndrome after infarction of the left arteria pericallosa. It has been suggested that the syndrome arises out of lacking inhibition from the dominant left hemisphere on the right hemisphere. Yet, in tests of spatial intelligence G.H. performed much better with his “anarchic” left hand than with his dominant right hand, similar to observations commonly reported in split-brain patients. Left–right manual choice responses and event-related EEG potentials to laterally presented stimuli were measured. Asymmetries were evident in G.H.’s behavior and EEG potentials, different from age-matched healthy participants ( n = 11). His right-hand responses were fast and unaffected by incompatibility with stimulus location, whereas his left-hand responses were variable and accompanied by a large negative central-midline EEG potential, probably reflecting efforts in initiating the response. G.H.’s visual N1 component peaked earlier and was larger at the right than the left side of the scalp, and the P3 component was distinctly reduced at the right side. Both features occurred independent of side of stimulus presentation and side of responding hand. The effort indicated by the midline negativity and the asymmetrically reduced P3 might directly reflect G.H.’s lack of control on his right hemisphere’s processing. The faster visual processing of the right hemisphere suggested by the N1 asymmetry might contribute to “anarchic” processing, making the right hemisphere process stimuli before control impulses exert their effect. These neurophysiological results tend to support the split-brain account which assumes that the syndrome arises by the lack of communication between hemispheres that act according to their respective competences.

Framing effects: The influence of handedness and access to right hemisphere processing

Changing how information is framed, such that the same critical information is cast in a positive or negative light, has a powerful impact on judgements and decision making. Research indicates that the influence of frames may be driven by participants’ initial affective response and that the right hemisphere is sensitive to the emotional connotation of stimuli. While previous research tested the effects of hemispheric differences on framing effects by inducing asymmetrical activation, the current study explored how stable brain differences may account for differences in susceptibility to framing effects. Because mixed degree of handedness is associated with increased access to right hemisphere processes, mixed-handed participants were expected to be more susceptible to the effects of framing than strong-handed participants. Participants responded to the Asian disease problem and completed as assessment of handedness. Although mixed- and strong-handed participants were affected differently, the results were not consistent with the hypothesis. Mixed-handed participants conformed to risky choice framing effects when options were framed negatively and showed no effect of the positive frame. Strong-handed participants conformed to positively framed options and showed no effect of the negative frame. Possible explanations are discussed.

Visual field differences in visual word recognition can emerge purely from perceptual learning: Evidence from modeling Chinese character pronunciation

In Chinese orthography, a dominant character structure exists in which a semantic radical appears on the left and a phonetic radical on the right (SP characters); a minority opposite arrangement also exists (PS characters). As the number of phonetic radical types is much greater than semantic radical types, in SP characters the information is skewed to the right, whereas in PS characters it is skewed to the left. Through training a computational model for SP and PS character recognition that takes into account of the locations in which the characters appear in the visual field during learning, but does not assume any fundamental hemispheric processing difference, we show that visual field differences can emerge as a consequence of the fundamental structural differences in information between SP and PS characters, as opposed to the fundamental processing differences between the two hemispheres. This modeling result is also consistent with behavioral naming performance. This work provides strong evidence that perceptual learning, i.e., the information structure of word stimuli to which the readers have long been exposed, is one of the factors that accounts for hemispheric asymmetry effects in visual word recognition.

Number of sense effects of Chinese disyllabic compounds in the two hemispheres

The current study manipulated the visual field and the number of senses of the first character in Chinese disyllabic compounds to investigate how the related senses (polysemy) of the constituted character in the compounds were represented and processed in the two hemispheres. The ERP results in experiment 1 revealed crossover patterns in the left hemisphere (LH) and the right hemisphere (RH). The sense facilitation in the LH was in favor of the assumption of single-entry representation for senses. However, the patterns in the RH yielded two possible interpretations: (1) the nature of hemispheric processing in dealing with sublexical sense ambiguity; (2) the semantic activation from the separate-entry representation for senses. To clarify these possibilities, experiment 2 was designed to push participants to a deeper level of lexical processing by the word class judgment. The results revealed the sense facilitation effect in the RH. In sum, the current study was in support of the single-entry account for related senses and demonstrated that two hemispheres processed sublexical sense ambiguity in a complementary way.

Music Reading Expertise Selectively Improves Categorical Judgment with Musical Notation

Different domains of perceptual expertise often lead to different hemispheric engagement (e.g. Kanwisher et al., 1997). Recent work suggests that the neural substrates engaged in musical reading are shifted from left hemisphere novice processing to bilateral processing in experts (Wong & Gauthier, 2010). To relate this shift to behavior, we tested whether music-reading training improves categorical and coordinate perceptual judgments, which are argued to rely on the left and right hemisphere respectively (Kosslyn et al., 1989). Music-reading experts and novices judged whether two sequentially presented music sequences were identical. The notes were either on a staff (categorical) or without a staff (coordinate) in either trained or untrained (90° rotated) orientations. Experts performed better than novices for categorical judgments, and the advantage was larger for the trained than untrained orientation. The two groups performed similarly for coordinate judgments. Music-reading fluency predicted performance in categorical judgments in the trained orientation in experts, while it predicted performance in all conditions in novices. This suggests that music-reading training selectively improves categorical judgments in the trained orientation, while music-reading ability in novices reflects general perceptual ability with notes. Future studies will clarify how these findings are related to the hemispheric shift in music-reading expertise.

Differential Hemispheric Processing in the Recognition of Chinese Characters with Different Structures in Foveal and Parafoveal Vision

Whether foveal representation in reading is initially split and contralaterally projected to different hemispheres or bilaterally projected remains a controversial issue. Here we examine visual field asymmetry effects in naming Chinese characters with different structures, with characters presented either to the left visual field or the right visual field (RVF), and either within or outside foveal vision (eccentricity). We show that overall the RVF advantage in naming characters was significant in both eccentricity conditions (fovea vs. parafovea), with a stronger effect in parafoveal vision. This suggests that foveal splitting may not be an all-or-none phenomenon but has a graded effect. When examining characters with different structures separately, this interaction between visual field and eccentricity was significant only in the dominant, right-heavy character structure type, but not in the minority left-heavy or symmetric structure types, suggesting a modulation of character structure or type frequency on the eccentricity effect. In addition, existence of a phonetic radical modulated the visual field asymmetry effect differentially in different character structure types; however this effect did not interact with eccentricity. This result thus suggests that character structure and existence of a phonetic radical have differential modulation on character processing in the foveal and parafoveal vision.

Evaluating Effects of Divided Hemispheric Processing on Word Recognition in Foveal and Extrafoveal Displays: The Evidence from Arabic

BackgroundPrevious studies have claimed that a precise split at the vertical midline of each fovea causes all words to the left and right of fixation to project to the opposite, contralateral hemisphere, and this division in hemispheric processing has considerable consequences for foveal word recognition. However, research in this area is dominated by the use of stimuli from Latinate languages, which may induce specific effects on performance. Consequently, we report two experiments using stimuli from a fundamentally different, non-Latinate language (Arabic) that offers an alternative way of revealing effects of split-foveal processing, if they exist.Methods and FindingsWords (and pseudowords) were presented to the left or right of fixation, either close to fixation and entirely within foveal vision, or further from fixation and entirely within extrafoveal vision. Fixation location and stimulus presentations were carefully controlled using an eye-tracker linked to a fixation-contingent display. To assess word recognition, Experiment 1 used the Reicher-Wheeler task and Experiment 2 used the lexical decision task.ResultsPerformance in both experiments indicated a functional division in hemispheric processing for words in extrafoveal locations (in recognition accuracy in Experiment 1 and in reaction times and error rates in Experiment 2) but no such division for words in foveal locations.ConclusionsThese findings from a non-Latinate language provide new evidence that although a functional division in hemispheric processing exists for word recognition outside the fovea, this division does not extend up to the point of fixation. Some implications for word recognition and reading are discussed.

Hemispheric processing and reading efficiency

This study using a primed lexical decision task in a visual half-field paradigm investigated the advantage of interhemispheric processing to enhance cognitive capacity associated with reading ability among college students. Sixty-five undergraduate students (23 males, 42 females, mean age = 20.6) served as one of the following: skilled readers for the short SOA, skilled readers for the long SOA, or unskilled readers for the long SOA. The results demonstrated that intrahemispheric processing was advantageous in a simple task and interhemispheric processing was advantageous in a complex task for skilled readers, but unskilled readers did not show the advantage of interhemispheric processing in the complex task. The lack of switching strategies suggests that their unskilled reading ability may stem from inefficient reading processing.

Sub‐patterns of language network reorganization in pediatric localization related epilepsy: A multisite study

To study the neural networks reorganization in pediatric epilepsy, a consortium of imaging centers was established to collect functional imaging data. Common paradigms and similar acquisition parameters were used. We studied 122 children (64 control and 58 LRE patients) across five sites using EPI BOLD fMRI and an auditory description decision task. After normalization to the MNI atlas, activation maps generated by FSL were separated into three sub-groups using a distance method in the principal component analysis (PCA)-based decisional space. Three activation patterns were identified: (1) the typical distributed network expected for task in left inferior frontal gyrus (Broca's) and along left superior temporal gyrus (Wernicke's) (60 controls, 35 patients); (2) a variant left dominant pattern with greater activation in IFG, mesial left frontal lobe, and right cerebellum (three controls, 15 patients); and (3) activation in the right counterparts of the first pattern in Broca's area (one control, eight patients). Patients were over represented in Groups 2 and 3 (P < 0.0004). There were no scanner (P = 0.4) or site effects (P = 0.6). Our data-driven method for fMRI activation pattern separation is independent of a priori notions and bias inherent in region of interest and visual analyses. In addition to the anticipated atypical right dominant activation pattern, a sub-pattern was identified that involved intensity and extent differences of activation within the distributed left hemisphere language processing network. These findings suggest a different, perhaps less efficient, cognitive strategy for LRE group to perform the task.

Hemispheric processing of sarcastic text

Recent evidence suggests that certain types of figurative language, such as conventional metaphors or idioms, may have a left hemisphere processing advantage or are processed similarly in both hemispheres. Sarcasm, however, is likely processed differently than other types of figurative language in the hemispheres because readers often need to construct a novel interpretation of sarcastic text to successfully understand the text’s sarcastic meaning. To investigate how the hemispheres process sarcasm during text comprehension, participants in the current study read sarcastic, literal, and neutral texts and made lexical decisions to related target words presented to either the left visual field-right hemisphere or the right visual field-left hemisphere. Facilitation for sarcastic texts was greater in the right hemisphere than the left hemisphere. In addition, facilitation was greater for literal texts than sarcastic texts in the left hemisphere. These findings suggest that the right hemisphere may play a unique role when readers encounter sarcasm during text comprehension.