Recent work in cognitive neuroscience has focused on analyzing the brain as a network, rather than as a collection of independent regions. Prior studies taking this approach have found that ...individual differences in the degree of modularity of the brain network relate to performance on cognitive tasks. However, inconsistent results concerning the direction of this relationship have been obtained, with some tasks showing better performance as modularity increases and other tasks showing worse performance. A recent theoretical model Chen, M., & Deem, M. W. 2015. Development of modularity in the neural activity of children's brains.
016009 suggests that these inconsistencies may be explained on the grounds that high-modularity networks favor performance on simple tasks whereas low-modularity networks favor performance on more complex tasks. The current study tests these predictions by relating modularity from resting-state fMRI to performance on a set of simple and complex behavioral tasks. Complex and simple tasks were defined on the basis of whether they did or did not draw on executive attention. Consistent with predictions, we found a negative correlation between individuals' modularity and their performance on a composite measure combining scores from the complex tasks but a positive correlation with performance on a composite measure combining scores from the simple tasks. These results and theory presented here provide a framework for linking measures of whole-brain organization from network neuroscience to cognitive processing.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In cognitive network neuroscience, the connectivity and community structure of the brain network is related to measures of cognitive performance, like attention and memory. Research in this emerging ...discipline has largely focused on two measures of connectivity-modularity and flexibility-which, for the most part, have been examined in isolation. The current project investigates the relationship between these two measures of connectivity and how they make separable contribution to predicting individual differences in performance on cognitive tasks. Using resting state fMRI data from 52 young adults, we show that flexibility and modularity are highly negatively correlated. We use a Brodmann parcellation of the fMRI data and a sliding window approach for calculation of the flexibility. We also demonstrate that flexibility and modularity make unique contributions to explain task performance, with a clear result showing that modularity, not flexibility, predicts performance for simple tasks and that flexibility plays a greater role in predicting performance on complex tasks that require cognitive control and executive functioning. The theory and results presented here allow for stronger links between measures of brain network connectivity and cognitive processes.
•Greater fMRI activity was observed in the left than the right STG during a sublexical speech perception task.•TMS disrupted performance during a speech perception task when applied to the left ...anterior STG relative to a control region.•TMS on the left posterior STG and the right STG during a speech perception task did not significantly disrupt performance.•A causal role of the left anterior STG on speech perception was established but not of the right STG.
Debate continues regarding the necessary role of right superior temporal gyrus (STG) regions in sublexical speech perception given the bilateral STG activation often observed in fMRI studies. To evaluate the causal roles, TMS pulses were delivered to inhibit and disrupt neuronal activity at the left and right STG regions during a nonword discrimination task based on peak activations from a blocked fMRI paradigm assessing speech vs. nonspeech perception (N = 20). Relative to a control region located in the posterior occipital lobe, TMS to the left anterior STG (laSTG) led to significantly worse accuracy, whereas TMS to the left posterior STG (lpSTG) and right anterior STG (raSTG) did not. Although the disruption from TMS was significantly greater for the laSTG than for raSTG, the difference in accuracy between the laSTG and lpSTG did not reach significance. The results argue for a causal role of the laSTG but not raSTG in speech perception. Further research is needed to establish the source of the differences between the laSTG and lpSTG.
Bilingual language control may involve cognitive control, including inhibition and switching. These types of control have been previously associated with neural activity in the inferior frontal gyrus ...(IFG) and the anterior cingulate cortex (ACC). In previous studies, the DRD2 gene, related to dopamine availability in the striatum, has been found to play a role in neural activity during cognitive control tasks, with carriers of the gene’s A1 allele showing different patterns of activity in inferior frontal regions during cognitive control tasks than non-carriers. The current study sought to extend these findings to the domain of bilingual language control. Forty-nine Spanish-English bilinguals participated in this study by providing DNA samples through saliva, completing background questionnaires, and performing a language production task (picture-naming), a non-verbal inhibition task (Simon task), and a non-verbal switching task (shape-color task) in the fMRI scanner. The fMRI data were analyzed to determine whether variation in the genetic background or bilingual language background predicts neural activity in the IFG and ACC during these three tasks. Results indicate that genetic and language background variables predicted neural activity in the IFG during English picture naming. Variation in only the genetic background predicted neural activity in the ACC during the shape-color switching task; variation in only the language background predicted neural activity in the ACC and IFG during the Simon task. These results suggest that variation in the DRD2 gene should not be ignored when drawing conclusions about bilingual verbal and non-verbal cognitive control.
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•Bilingual language control is associated with activity in the inferior frontal gyrus.•Non-verbal control is associated with activity in the anterior cingulate cortex.•Specific genotypes predict fMRI activity during language control and task switching.•Bilingual experience predicts fMRI activity during language control and inhibition.
Bilingualism represents an interesting model of possible experience-dependent alterations in brain structure. The current study examines whether interhemispheric adaptations in brain structure are ...associated with bilingualism. Corpus callosum volume and cortical thickness asymmetry across 13 regions of interest (selected to include critical language and bilingual cognitive control areas) were measured in a sample of Spanish-English bilinguals and age- and gender-matched monolingual individuals (N = 39 per group). Cortical thickness asymmetry of the anterior cingulate region differed across groups, with thicker right than left cortex for bilinguals and the reverse for monolinguals. In addition, two adjacent regions of the corpus callosum (mid-anterior and central) had greater volume in bilinguals. The findings suggest that structural indices of interhemispheric organization in a critical cognitive control region are sensitive to variations in language experience.
•Thickness asymmetry of anterior cingulate is reversed for bilingual vs monolinguals.•Rightward asymmetry for bilinguals, leftward for monolinguals.•Mid-anterior/central corpus callosum volume greater for bilinguals.•Brain structure in a cognitive control region varies with language experience.•Differing interhemispheric organization in brain structure for bilinguals.
Brainstem BOLD response to visual and acoustic stimuli Han, Chungmin; Ress, David; Ramos Nunez, Aurora I. ...
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC),
07/2020
Conference Proceeding
Odprti dostop
Understanding the fundamental roles of brainstem function resulting in proper motor control is critical to motor-rehabilitation after brain injuries. In particular, vestibular and reticular formation ...nuclei are thought to be associated with spasticity in chronic stroke patients. We used two kinds of stimuli in 10 healthy subjects to activate these nuclei while collecting high-resolution (1.5-mm) fMRI across the majority of brainstem. Optokinetic stimuli evoked illusory self-motion to activate the vestibular nuclei. Acoustic-startle stimuli were sets of loud tones designed to activate of the reticular formation. We summarized the response represented in a form of activation volume, mean percent signal change, and the phase delay (time lag) following the stimulus. We observed patterns of significant activations in the brainstem but did not find significant differences between the stimulus. We conclude that more sensitive measurement techniques are needed to reliably detect vestibular and reticular formation nuclei responses.
A bilingual person's brain has to manage two languages. According to psycholinguistic models, lexical representations of the two languages are always active and to select the correct language, the ...other has to be inhibited (Green, 1998). This includes cognitive control processes (e.g. language planning, response inhibition, maintenance of representation) that might require additional brain networks beyond those classically involved in language processing. Regions such as prefrontal, anterior cingulate cortices, inferior parietal lobule, and caudate have been found to be involved in cognitive control processes (Abutalebi & Green, 2007). The present study examined whether or not bilingual experience shapes the structure and function of the brain by examining relationships among language proficiency, second language age of acquisition, and structural and functional correlates. Participants were 49 Spanish-English bilinguals who learned English between the ages of 0 and 17 years. Cortical thickness measures as well as functional activity during a picture-naming task requiring switching between the two languages on a trial-by-trial basis were acquired using a functional Magnetic Resonance Imaging scanner. The results indicate that age of acquisition of the second language but not proficiency is related to gray matter structure in the right dorsolateral prefrontal cortex, a cognitive control region and that gray matter cortical thickness is related to functional activity during a condition that requires switching in naming pictures between two languages. These results carry implications for the understanding of how language experience shapes the functional and neural correlates of the bilingual brain.
Spasticity, defined as velocity-dependent resistance to passive stretch, is common after stroke and imposes significant therapeutic challenges. It is believed that disinhibition of brainstem nuclei ...is responsible for spasticity, but there is debate on which individual nuclei within the brainstem, i.e. the lateral vestibular nuclei or pontine reticular formation within the whole reticular formation, are primarily involved. As such, we aimed to localize the activity of these individual brainstem nuclei via 3T functional magnetic resonance imaging (fMRI) in 10 people with post-stroke spasticity and compared the data with 11 age-matched healthy individuals. We used both acoustic and visual stimuli aimed at activating the pontine reticular formation and lateral vestibular nuclei. Visual stimuli were presented in the form of a moving checkerboard evoking illusionary self-motion to activate the vestibular network. Acoustic stimuli used loud (Sound pressure level SPL = 100 dB) acoustic bursts, expected to evoke a startle reflex and therefore activate both pontine reticular formation and lateral vestibular nuclei. We expected to find greater asymmetry in activation of brainstem nuclei in post-stroke compared to healthy individuals. We did not observe any difference in lateral symmetry between the two groups. However, we found that chronic stroke individuals exhibited three significant (p\gt 0.05) effects: 1) there were different delays in response to visual stimuli compared to acoustic stimuli; 2) the level of activation of the vestibular nuclei in post-stroke individuals was correlated to age, time since stroke, and brainstem volume); 3) brainstem volume of chronic stroke participants was smaller than in healthy individuals. These findings suggest that further efforts would be useful to better characterize functional activation of brainstem nuclei, especially in pathologies such as stroke.
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