Exploring cerebral asymmetries for the verb generation task

Dual-task decrements in mono-, bi- and multilingual participants: Evidence for multilingual advantage

Evidence suggests that language processing in bilinguals is less left-lateralized than in monolinguals. We explored dual-task decrement (DTD) for mono-, bi- and multilinguals in a verbal-motor dual-task paradigm. We expected monolinguals to show greater DTD than bilingual participants, who would show greater DTD than multilingual participants. Fifty right-handed participants (18 monolingual, 16 bilingual, 16 multilingual) completed verbal fluency and manual motor tasks in isolation and concurrently. Tasks were completed twice in isolation (left-handed, right-handed) and twice as dual-tasks (left-handed, right-handed); participants' motor-executing hands served proxy for hemispheric activation. Results supported the hypotheses. Completing dual-tasks incurred greater cost for manual motor tasks than for verbal fluency tasks. Negative cost of performing dual-tasks diminished as number of languages spoken increased; in fact, multilingual individuals demonstrated a dual-task advantage in both tasks when using the right hand, strongest in the verbal task. Dual-tasking had the greatest negative impact on verbal fluency of monolingual participants when the motor task was completed with the right hand; for bi- and multi-lingual participants, the greatest negative impact on verbal fluency was seen when the motor task was completed with the left hand. Results provide support for the bi-lateralization of language function in bi- and multilingual individuals.

Brain connectivity-based prediction of real-life creativity is mediated by semantic memory structure

Associative theories of creativity argue that creative cognition involves the abilities to generate remote associations and make useful connections between unrelated concepts in one's semantic memory. Yet, whether and how real-life creative behavior relies on semantic memory structure and its neural substrates remains unclear. We acquired multi-echo functional magnetic resonance imaging data while participants underwent a semantic relatedness judgment task. These ratings were used to estimate their individual semantic memory networks, whose properties significantly predicted their real-life creativity. Using a connectome predictive modeling approach, we identified patterns of task-based functional connectivity that predicted creativity-related semantic memory network properties. Furthermore, these properties mediated the relationship between functional connectivity and real-life creativity. These results provide new insights into how brain connectivity patterns support real-life creative behavior via the structure of semantic memory. We also show how computational network science can be used to couple behavioral, cognitive, and neural levels of analysis.

Disrupted dynamic network reconfiguration of the language system in temporal lobe epilepsy

Temporal lobe epilepsy tends to reshape the language system causing maladaptive reorganization that can be characterized by task-based functional MRI, and eventually can contribute to surgical decision making processes. However, the dynamic interacting nature of the brain as a complex system is often neglected, with many studies treating the language system as a static monolithic structure. Here, we demonstrate that as a specialized and integrated system, the language network is inherently dynamic, characterized by rich patterns of regional interactions, whose transient dynamics are disrupted in patients with temporal lobe epilepsy. Specifically, we applied tools from dynamic network neuroscience to functional MRI data collected from 50 temporal lobe epilepsy patients and 30 matched healthy controls during performance of a verbal fluency task, as well as during rest. By assigning 16 language-related regions into four subsystems (i.e. bilateral frontal and temporal), we observed regional specialization in both the probability of transient interactions and the frequency of such changes, in both healthy controls and patients during task performance but not rest. Furthermore, we found that both left and right temporal lobe epilepsy patients displayed reduced interactions within the left frontal 'core' subsystem compared to the healthy controls, while left temporal lobe epilepsy patients were unique in showing enhanced interactions between the left frontal 'core' and the right temporal subsystems. Also, both patient groups displayed reduced flexibility in the transient interactions of the left temporal and right frontal subsystems, which formed the 'periphery' of the language network. Importantly, such group differences were again evident only during task condition. Lastly, through random forest regression, we showed that dynamic reconfiguration of the language system tracks individual differences in verbal fluency with superior prediction accuracy compared to traditional activation-based static measures. Our results suggest dynamic network measures may be an effective biomarker for detecting the language dysfunction associated with neurological diseases such as temporal lobe epilepsy, specifying both the type of neuronal communications that are missing in these patients and those that are potentially added but maladaptive. Further advancements along these lines, transforming how we characterize and map language networks in the brain, have a high probability of altering clinical decision making in neurosurgical centres.10.1093/brain/awy042_video1awy042media15754656112001.

Thin slices of creativity: using single-word utterances to assess creative cognition

We investigated the hypothesis that individual differences in creative cognition can be manifest even in brief responses, such as single-word utterances. Participants (n = 193) were instructed to say a verb upon seeing a noun displayed on a computer screen and were cued to respond creatively to half of the nouns. For every noun-verb pair (72 pairs per subject), we assessed the semantic distance between the noun and the verb, using latent semantic analysis (LSA). Semantic distance was higher in the cued ("creative") condition than the uncued condition, within subjects. Critically, between subjects, semantic distance in the cued condition had a strong relationship to a creativity factor derived from a battery of verbal, nonverbal, and achievement-based creativity measures (β= .50), and this relation remained when controlling for intelligence and personality. The data show that creative cognition can be assessed reliably and validly from such thin slices of behavior.

Hemispheric and executive influences on low-level language processing after traumatic brain injury

OBJECTIVE

The purpose of this study was to examine whether minor high-level language deficits found after traumatic brain injury (TBI) might be due to low-level language processing issues or executive control influences. A possible mechanism was also investigated.

METHOD

Nineteen age- and education-matched healthy controls (16 M, 3 F) and 19 persons who had experienced a complicated mild, moderate or severe TBI between 1-3 years prior (16 M, 3 F; mean GCS = 9.44) participated in two computerized behavioural experiments utilizing two paradigms standard in the psycholinguistic literature (priming with lexical decision and verb generation), which included trials of greater and lesser executive demand.

RESULTS

Response time and accuracy differences were found in both experiments, indicating deficits in single-word processing for the patient group. Disproportionate difficulty was found for trials which included an executive component. Right visual field (left hemisphere) preferences were found to be stronger in the TBI group than in controls.

CONCLUSIONS

Results suggest that persons with TBI may have difficulties in processing single words alone, especially under conditions of increased executive demand, and that atypical patterns of hemispheric recruitment may be associated with these difficulties.

Functional MRI evidence for inefficient attentional control in adolescent chronic cannabis abuse

Control of attention is a key mechanism underlying behavior regulation. In this study we detail the aspects of attention that covary with the chronic use of cannabis throughout adolescence. We compared performance and brain activation differences in tasks involving attention between young adults with a history of chronic cannabis use during adolescence and matched non-user control subjects. Two tasks were used to activate attention networks: the Attention Network Task (ANT) and the use generation task. In the ANT, chronic users (N=14) differed from controls (N=14) in showing poorer performance (longer reaction time and more errors) on tasks requiring processing of incongruent stimuli reflecting the executive attention network, but not in networks related to alerting or orienting components of attention. Functional MRI of brain activity showed stronger activation within the right prefrontal cortex in chronic users compared to the control group specifically on ANT trials requiring executive attention. The use generation task also revealed significantly stronger activation of the same right prefrontal area in users compared to controls. These results suggest that chronic cannabis users have less efficient executive attention in conflict resolution tasks, demanding more activation in the right prefrontal areas to resolve conflict.

The effects of divided attention on speech motor, verbal fluency, and manual task performance

PURPOSE

The goal of this study was to evaluate aspects of the functional distance hypothesis, which predicts that tasks regulated by brain networks in closer anatomic proximity will interfere more with each other than tasks controlled by spatially distant regions. Speech, verbal fluency, and manual motor tasks were examined to ascertain whether right-handed activity would interfere more with speech and language performance because of the presumed greater demands on the left hemisphere.

METHOD

Twenty young adults completed a speech task (repeating a sentence), a verbal fluency task (listing words beginning with the same letter), and right- and left-handed motor tasks (placing pegs and washers in a pegboard) in isolation and concurrently.

RESULTS

Speech kinematic data showed that during concurrent performance of manual tasks, lip displacement and peak velocity decreased, whereas sound pressure level increased. Spatiotemporal variability increased when the nondominant hand was used for a motor task. Manual motor scores significantly decreased when concurrently performed with the verbal fluency task but not with sentence repetition.

CONCLUSION

These findings suggest that the control of concurrent tasks may be more complex than is predicted by the functional distance hypothesis.

Activation and maintenance of peripheral semantic features of unambiguous words after right hemisphere brain damage in adults

BACKGROUND: The right cerebral hemisphere (RH) sustains activation of subordinate, secondary, less common, and/or distantly related meanings of words. Much of the pertinent data come from studies of homonyms, but some evidence also suggests that the RH has a unique maintenance function in relation to unambiguous nouns. In a divided visual field priming study, Atchley, Burgess, and Keeney (1999) reported that only left visual field/RH presentation yielded evidence of continuing activation of peripheral semantic features that were incompatible with the most common image or representation of their corresponding nouns (e.g., rotten for "apple"). Activation for weakly related features that were compatible with the dominant representation (e.g., crunchy) was sustained over time regardless of the visual field/hemisphere of initial stimulus input. Several studies report that unilateral right hemisphere brain damage (RHD) in adults affects the RH's meaning maintenance function, but this work also has centred on homonyms, and/or more recently metonymic and metaphoric polysemous words. AIMS: The current investigation examined whether RHD deficits in processing secondary and/or distantly related meanings of words, typically observed in studies of homonyms, would extend to peripheral, weakly related semantic features of unambiguous nouns. METHODS #ENTITYSTARTX00026; PROCEDURES: Participants were 28 adults with unilateral RHD from cerebrovascular accident, and 38 adults without brain damage. Participants listened to spoken sentences that ended with an unambiguous noun. Each sentence was followed by a spoken target phoneme string. Targets included peripheral semantic features of the sentence-final noun that were either compatible or incompatible with the dominant mental images of the noun, and were presented at two intervals after that noun. A lexical decision task was used to gauge both the early activation and maintenance of activation for these weakly related semantic features. OUTCOMES #ENTITYSTARTX00026; RESULTS: Accuracy data demonstrated activation (priming) for both types of peripheral features, in both groups, shortly after presentation of the corresponding noun. Neither group evidenced continuing activation for either type of feature at a longer interval. These results are interpreted as reflecting rapid decay/poor maintenance of activation for distantly related features for both groups. The lack of a biasing context, however, did not provide an appropriate test for previously reported suppression deficits after RHD. Fast decay of activation of compatible semantic features was unexpected for the control group. Adults with RHD were less accurate than the control group at both test intervals for the features that are semantically more distant from their associated nouns (Related-incompatible features). Accordingly, it is argued that the RHD group's poor maintenance of activation for these features reflects a deficit, rather than normal performance. The interpretation of results from this study is complicated by the lack of RT priming for either type of semantic feature, and for either participant group. CONCLUSIONS: The right cerebral hemisphere appears to be necessary for activating semantic features that are particularly distantly related to their corresponding lexical items, and for sustaining activation of these features in the absence of a biasing context. Because lexical processing has been linked with discourse comprehension for adults with RHD, more work in this area should enhance clinical management in the future.