Evidence for right hemisphere phonology in a backward masking task

The extent to which orthographic and phonological processes are available during the initial moments of word recognition within each hemisphere is under specified, particularly for the right hemisphere. Few studies have investigated whether each hemisphere uses orthography and phonology under constraints that restrict the viewing time of words and reduce overt phonological demands. The current study used backward masking in the divided visual field paradigm to explore hemisphere differences in the availability of orthographic and phonological word recognition processes. A 20 ms and 60 ms SOA were used to track the time course of how these processes develop during pre-lexical moments of word recognition. Nonword masks varied in similarity to the target words such that there were four types: orthographically and phonologically similar, orthographically but not phonologically similar, phonologically but not orthographically similar and unrelated. The results showed the left hemisphere has access to both orthography and phonology early in the word recognition process. With more time to process the stimulus, the left hemisphere is able to use phonology which benefits word recognition to a larger extent than orthography. The right hemisphere also demonstrates access to both orthography and phonology in the initial moments of word recognition, however, orthographic similarity improves word recognition to a greater extent than phonological similarity.     

The role of the right hemisphere in speech act comprehension

In this research the role of the RH in the comprehension of speech acts (or illocutionary force) was examined. Two split-screen experiments were conducted in which participants made lexical decisions for lateralized targets after reading a brief conversation remark. On one-half of the trials the target word named the speech act performed with the preceding conversation remark; on the remaining trials the target did not name the speech act that the remark performed. In both experiments, lexical decisions were facilitated for targets representing the speech act performed with the prior utterance, but only when the target was presented to the left visual field (and hence initially processed by the RH) and not when presented to the right visual field. This effect occurred at both short (Experiment 1: 250 ms) and long (Experiment 2: 1000 ms) delays. The results demonstrate the critical role played by the RH in conversation processing.     

Visual neglect in the first weeks after a stroke in the right hemisphere

The aim of the study was to characterize symptoms of visual neglect among patients who recently survived a stroke in the right hemisphere (RH), and to contribute to the understanding of change in symptoms during the first months after a RH stroke. Thirteen patients with a RH stroke and twenty controls were assessed by using standard neglect tests. Five patients were followed up by repetitive test sessions during the next four months. To assess more subtle symptoms, reaction-time (RT) measures derived from an experimental cue-target paradigm were included in the final test session. A high frequency of neglect symptoms was documented at the first test session. The changes in performance during the first weeks were characterized by a high inter-individual as well as a high intra-individual variability. Although the remission rate on standard tests was high in the follow-up study, the RT measures indicated sustained symptoms of visual extinction in all patients. The long-term implication of the changes of neglect symptoms during the first weeks after a stroke and signs of sustained symptoms of visual extinction calls for further longitudinal studies including a larger group of patients.     

The right hemisphere advantage in visual change detection depends on temporal factors

What accounts for the Right Hemisphere (RH) functional superiority in visual change detection? An original task which combines one-shot and divided visual field paradigms allowed us to direct change information initially to the RH or the Left Hemisphere (LH) by deleting, respectively, an object included in the left or right half of a scene presented centrally. We manipulated the perceptual salience and semantic relevance of the change as well as the duration of the Inter-Stimulus Interval (ISI) between the scenes in order to clarify the role of the RH in memory and attention processes, and to explore whether lengthening the ISI would enhance the contribution of the LH. When analyzing data collapsed over the two levels (high vs. low) of salience and of relevance, changes were better detected in the left visual field (lvf) than in the right visual field (rvf) in the case of a short ISI, while no difference emerged in the case of a long ISI. Moreover, lengthening the ISI resulted in a performance decrement in the lvf, both for accuracy and response speed. The fact that the RH superiority was limited to short intervals indicates that stimulus-driven orienting contributes more than perceptual processing to this hemispheric asymmetry. When considering perceptual and semantic properties of the change, the effect of the ISI duration seemed to specifically emerge in the case of low relevance, with an enhancement of accuracy in the rvf when comparing the long with the short ISI. This suggests that the ISI influence on hemispheric performance operates on different levels.     

The propositional structure of discourse in the two cerebral hemispheres

Readers construct at least two interrelated representations when they comprehend a text: (a) a representation of the explicit ideas in a text and the relations among them (i.e., a propositional representation) and (b) a representation of the context or situation to which a text refers (i.e., a discourse model). In a recent study, found evidence that readers' representations were structured according to propositional relations, but only in the left hemisphere. Both hemispheres, however, appeared to represent contextually relevant semantic information. The goal in the current study was to examine further the organization of explicit text concepts in the two hemispheres. We used an item-priming-in-recognition paradigm in combination with a lateralized visual-field manipulation. We found evidence for a propositionally structured representation in the left hemisphere, that is, priming effects that reflected the linear distance between primes and targets in the propositional structure of passages. We also found that the right hemisphere represented explicit text concepts, but we found no evidence that these concepts were organized structurally. In a second experiment, we found our item priming effects reflected the representation of text information in memory and did not reflect lexical-semantic priming at test.     

Hemihypokinesia after right hemisphere stroke

We tested the hypothesis that the right hemisphere is dominant for motor activation of "intention." If the right hemisphere is dominant for intention and if intention is a prerequisite for movement, motor impairment should be worse after an infarct in the right hemisphere than in the left. We asked nine subjects with right and nine with left hemisphere infarcts to elevate each shoulder independently. Subjects with right hemisphere lesions had more trouble moving the contralateral shoulder. The data are consistent with the hypothesis that the right hemisphere is dominant for motor activation or intention.     

Hemispheric specialization and creative thinking: A meta-analytic review of lateralization of creativity

In the last two decades research on the neurophysiological processes of creativity has found contradicting results. Whereas most research suggests right hemisphere dominance in creative thinking, left-hemisphere dominance has also been reported. The present research is a meta-analytic review of the literature to establish how creative thinking relates to relative hemispheric dominance. The analysis was performed on the basis of a non-parametric vote-counting approach and effect-size calculations of Cramer’s phi suggest relative dominance of the right hemisphere during creative thinking. Moderator analyses revealed no difference in predominant right-hemispheric activation for verbal vs. figural tasks, holistic vs. analytical tasks, and context-dependent vs. context-independent tasks. Suggestions for further investigations with the meta-analytic and neuroscience methodologies to answer the questions of left hemispheric activation and further moderation of the effects are discussed.     

Lateral biases and reading direction: a dissociation between aesthetic preference and line bisection

Perceptual asymmetries for tasks involving aesthetic preference or line bisection can be affected by asymmetrical neurological mechanisms or left/right reading habits. This study investigated the relative contribution of these mechanisms in 100 readers of Japanese and English. Participants made aesthetic judgments between pairs of mirror-reversed pictures showing: (a) static objects, (b) moving objects and (c) landscapes. A line bisection task was also administered. There was a strong effect of reading direction for static and mobile objects whereby Japanese readers preferred objects with a right-to-left directionality (and vice versa for English readers). In contrast, similar patterns were observed for the Japanese and English readers for the landscape and line bisection tasks. The results show that reading habits affect aesthetic judgments for static and moving object tasks, but not the landscape and line bisection tasks. The difference between the tasks may be related to the horizontal/vertical geometry of the stimuli, which makes the landscape and line bisection tasks more prone to universal effects related to cerebral dominance.     

Gender differences in empathy: the role of the right hemisphere

The relationship between activation of the right cerebral hemisphere (RH) and empathy was investigated. Twenty-two men and 73 women participated by completing a chimeric face task and empathy questionnaire. For the face task, participants were asked to pick which of the two chimeric faces looked happier. Both men and women were significantly more likely to say the chimera with the smile to their left was happier, suggesting activation of the RH. As expected, men scored significantly lower than women on the empathy questionnaire, p = .003. A correlation was found between RH activation on the face task and empathy for women only, p = .037, suggesting a possible neural basis for gender differences in empathy.     

Neuropsychological syndromes in right hemisphere stroke patients

A specific set of syndromes, based on different intrahemispheric lesion locations, has not yet been described in patients with right hemisphere lesions. To explore whether statistically derived clusters could give clues to a syndrome structure, neuropsychological data from a sample of 106 patients with right hemisphere stroke were studied. CT data were available for 58 of the patients. Based on factor analysis of eight test and four ratings variables, six variables were chosen for a cluster analysis. A structure of 13 clusters was considered statistically valid. Combining clusters with parallel test profiles into main cluster classes, five right hemisphere syndromes proved clinically valid: an above average syndrome ( n =46), denial perseverance (frontal) syndrome ( n =14). a depressed mood syndrome ( n = 14), a focal RH syndrome ( n =18) and a global RH syndrome ( n =9). It is suggested that syndromes are related to intrahemispheric location of the lesion, such as the extent of anterior and posterior damage.     

Sensitivity to local sentence context information in lexical ambiguity resolution: evidence from left- and right-hemisphere-damaged individuals

Using a cross-modal semantic priming paradigm, the present study investigated the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use local sentence context information to resolve lexically ambiguous words. Critical sentences were manipulated such that they were either unbiased, or biased toward one of two meanings of sentence-final equibiased ambiguous words. Sentence primes were presented auditorily, followed after a short (0 ms) or long (750 ms) interstimulus interval (ISI) by the presentation of a first- or second-meaning related visual target, on which subjects made a lexical decision. At the short ISI, neither patient group appeared to be influenced by context, in sharp contrast to the performance of the NBD control subjects. LHD nonfluent aphasic subjects activated both meanings of ambiguous words regardless of context, whereas RHD subjects activated only the first meaning in unbiased and second-meaning biased contexts. At the long ISI, LHD nonfluent aphasic subjects failed to show evidence of activation of either meaning, while RHD individuals activated first meanings in unbiased contexts and contextually appropriate meanings in second-meaning biased contexts. These findings suggest that both left (LH) and right hemisphere (RH) damage lead to deficits in using local contextual information to complete the process of ambiguity resolution. LH damage seems to spare initial access to word meanings, but initially impairs the ability to use context and results in a faster than normal decay of lexical activation. RH damage appears to initially disrupt access to context, resulting in an over-reliance on frequency in the activation of ambiguous word meanings.     

The moderating effect of humor style on the relationship between interpersonal predictors of suicide and suicidal ideation

This study investigated how positive and negative humor styles relate to suicidal ideation, thwarted belongingness, and perceived burdensomeness. Analyses indicated that affiliative and self-defeating humor style moderated the relationships between thwarted belongingness and suicidal ideation as well as perceived burdensomeness and suicidal ideation when controlling for depression. The clinical importance of assessing and tracking humor styles as potential coping mechanisms against suicidal thinking is discussed.     

A high-loaded hemisphere successfully ignores distractors

We used a response competition paradigm to investigate whether a distractor is effectively rejected under conditions where it is projected to a highly-loaded hemisphere. In two experiments we asked right-handed participants to identify a target among five task-relevant letters while they ignored a distractor. We manipulated both the distractor visual-field (low-load/high-load) and the compatibility of the target and the distractor. In the low-loaded visual-field, we presented a distractor with one task-relevant stimulus to one visual-field and the remaining task-relevant stimuli to the opposite visual-field. In the high-loaded visual-field, we presented a distractor and task-relevant stimuli in reverse. In Experiment 1 (left/right), we found a compatibility effect for the low-loaded, but not for the high-loaded visual-field. In Experiment 2, this modulation of the compatibility effect did not appear when the upper/lower visual-field was manipulated. These findings demonstrate that a distractor is successfully ignored when it is presented to a highly-loaded hemisphere.     

Relationships between the Dark Triad and humor styles: A replication and extension

Two hundred undergraduate students completed paper-and-pencil measures of the Dark Triad (Machiavellianism, narcissism, and psychopathy) and the Humor Styles Questionnaire, which taps two adaptive (affiliative and self-enhancing) and two maladaptive (aggressive and self-defeating) styles of humor. The first purpose of the study was to replicate relationships between these variables reported by Veselka et al. (2010). The second purpose was to expand on their results by investigating relationships between several sub-factors of the Dark Triad (in addition to global scores) and the humor styles. Results provided substantial replication of Veselka et al. at the global level and, at the sub-factor level, provided additional insights into the potential role of adaptive and maladaptive humor styles in the personality dynamics of individuals characterized by the various facets of the Dark Triad.     

The representation of discourse in the two hemispheres: an individual differences investigation

Two experiments were conducted to investigate discourse representation in the two cerebral hemispheres as a function of reading skill. We used a lateralized visual-field procedure to compare left hemisphere (LH) and right hemisphere (RH) sensitivity to different discourse relations in readers with varying skill levels. In Experiment 1, we investigated two levels of discourse representation in memory: (a) the propositional representation and (b) the discourse model. We found that all readers were sensitive to propositional relations in the LH. In contrast, sensitivity to propositional relations in the RH increased as a function of reading skill. In addition, reading skill was positively related to topic relations in the LH, whereas it was negatively in the RH. In Experiment 2, we investigated propositional relations of different distances and again found that all readers were sensitive to propositional relations in the LH, whereas sensitivity to propositional relations in the RH was negatively related to reading skill. In general, reading skill appears to be associated with left-lateralized discourse representations.     

Rumination and dysphoria: The buffering role of adaptive forms of humor

The current study examines the effects of rumination and humor on individuals’ dysphoria level. Measures of humor (affiliative and self-enhancing), rumination, and depressive symptoms were completed by 303 undergraduate students. Consistent with our hypothesis, both affiliative humor and rumination independently accounted for variance in dysphoria levels. In addition, self-enhancing humor and rumination were independently associated with dysphoria. Moreover, significant interactions between affiliative humor and rumination, and self-enhancing humor and rumination, on dysphoria also emerged. Results indicated that among individuals with high rumination, those with high affiliative and/or self-enhancing humor had significantly lower levels of dysphoria than individuals with low affiliative and/or self-enhancing humor. The combination of low affiliative and/or self-enhancing humor and high rumination led to substantially higher levels of dysphoria than any other combination. Implications for psychotherapy and research in this area are discussed.     

Asymmetries for the visual expression and perception of speech

This study explored asymmetries for movement, expression and perception of visual speech. Sixteen dextral models were videoed as they articulated: 'bat,' 'cat,' 'fat,' and 'sat.' Measurements revealed that the right side of the mouth was opened wider and for a longer period than the left. The asymmetry was accentuated at the beginning and ends of the vocalization and was attenuated for words where the lips did not articulate the first consonant. To measure asymmetries in expressivity, 20 dextral observers watched silent videos and reported what was said. The model's mouth was covered so that the left, right or both sides were visible. Fewer errors were made when the right mouth was visible compared to the left--suggesting that the right side is more visually expressive of speech. Investigation of asymmetries in perception using mirror-reversed clips revealed that participants did not preferentially attend to one side of the speaker's face. A correlational analysis revealed an association between movement and expressivity whereby a more motile right mouth led to stronger visual expressivity of the right mouth. The asymmetries are most likely driven by left hemisphere specialization for language, which causes a rightward motoric bias.