Effective connectivity reveals strategy differences in an expert calculator

Mathematical reasoning is a core component of cognition and the study of experts defines the upper limits of human cognitive abilities, which is why we are fascinated by peak performers, such as chess masters and mental calculators. Here, we investigated the neural bases of calendrical skills, i.e. the ability to rapidly identify the weekday of a particular date, in a gifted mental calculator who does not fall in the autistic spectrum, using functional MRI. Graph-based mapping of effective connectivity, but not univariate analysis, revealed distinct anatomical location of “cortical hubs” supporting the processing of well-practiced close dates and less-practiced remote dates: the former engaged predominantly occipital and medial temporal areas, whereas the latter were associated mainly with prefrontal, orbitofrontal and anterior cingulate connectivity. These results point to the effect of extensive practice on the development of expertise and long term working memory, and demonstrate the role of frontal networks in supporting performance on less practiced calculations, which incur additional processing demands. Through the example of calendrical skills, our results demonstrate that the ability to perform complex calculations is initially supported by extensive attentional and strategic resources, which, as expertise develops, are gradually replaced by access to long term working memory for familiar material

Overlapping neural systems represent cognitive effort and reward anticipation

Anticipating a potential benefit and how difficult it will be to obtain it are valuable skills in a constantly changing environment. In the human brain, the anticipation of reward is encoded by the Anterior Cingulate Cortex (ACC) and Striatum. Naturally, potential rewards have an incentive quality, resulting in a motivational effect improving performance. Recently it has been proposed that an upcoming task requiring effort induces a similar anticipation mechanism as reward, relying on the same cortico-limbic network. However, this overlapping anticipatory activity for reward and effort has only been investigated in a perceptual task. Whether this generalizes to high-level cognitive tasks remains to be investigated. To this end, an fMRI experiment was designed to investigate anticipation of reward and effort in cognitive tasks. A mental arithmetic task was implemented, manipulating effort (difficulty), reward, and delay in reward delivery to control for temporal confounds. The goal was to test for the motivational effect induced by the expectation of bigger reward and higher effort. The results showed that the activation elicited by an upcoming difficult task overlapped with higher reward prospect in the ACC and in the striatum, thus highlighting a pivotal role of this circuit in sustaining motivated behavior

The function of the left angular gyrus in mental arithmetic: Evidence from the associative confusion effect

While the left angular gyrus (lAG) has been repeatedly implicated in mental arithmetic, its precise functional role has not been established. On the one hand, it has been speculated that the lAG is involved in task-specific processes. On the other hand, the observation of relative deactivation during arithmetic has led to the contention that differential lAG activation reflects task-unrelated difficulty effects associated with the default mode network (DMN). Using functional magnetic resonance imaging, we investigated the neural correlates of the associative confusion effect that allowed us to dissociate effects of task difficulty and task-related arithmetic processes on lAG activation. The associative confusion effect is characterized by poorer performance while verifying addition and multiplication equations whose solutions are associated with the other operation (confusion equations: e.g., 9 × 6 = 15 ) compared with solutions unrelated to both operations (non-confusion equations: e.g., 9 × 6 = 52 ). Comparing these two conditions revealed higher activation of the anterior lAG (areas PGa, PFm, and PF) and the left dorsolateral prefrontal cortex for the confusion problems. This effect displayed only slight anatomical overlap with the well-established reverse problem-size effect (small minus large problems) and task-related deactivation in the parietal cortex. The finding of greater lAG activity (less deactivation) in the more difficult task condition is inconsistent with the hypothesis that lAG activation during mental arithmetic reflects task difficulty related modulations of the DMN. Instead, the present findings provide further support for the symbol-referent mapping hypothesis, suggesting that the lAG mediates the automatic mapping of arithmetic problems onto solutions stored in memory. © 2011 Wiley Periodicals, Inc

Changes in brain activity in response to problem solving during the abstinence from online game play

Background and aims: Several studies have suggested that addictive disorders including substance abuse and pathologic gambling might be associated with dysfunction on working memory and prefrontal activity. We hypothesized that excessive online game playing is associated with deficits in prefrontal cortex function and that recovery from excessive online game playing might improve prefrontal cortical activation in response to working memory stimulation. Methods: Thirteen adolescents with excessive online game playing (AEOP) and ten healthy adolescents (HC) agreed to participate in this study. The severity of online game play and playing time were evaluated for a baseline measurement and again following four weeks of treatment. Brain activation in response to working memory tasks (simple and complex calculations) at baseline and subsequent measurements was assessed using BOLD functional magnetic resonance imaging (fMRI). Results: Compared to the HC subjects, the AEOP participants exhibited significantly greater activity in the right middle occipital gyrus, left cerebellum posterior lobe, left premotor cortex and left middle temporal gyrus in response to working memory tasks during baseline measurements. After four weeks of treatment, the AEOP subjects showed increased activity within the right dorsolateral prefrontal cortex and left occipital fusiform gyrus. After four weeks of treatment, changes in the severity of online game playing were negatively correlated with changes in the mean β value of the right dorsolateral prefrontal cortex in response to complex stimulation. Conclusions: We suggest that the effects of online game addiction on working memory may be similar to those observed in patients with substance dependence

Effects of stress

Complex cognitive tasks such as mental arithmetic heavily rely on intact, well-coordinated prefrontal cortex (PFC) function. Converging evidence suggests that frontal midline theta (FMT) oscillations play an important role during the execution of such PFC-dependent tasks. Additionally, it is well- established that acute stress impairs PFC function, and recent evidence suggests that FMT is decreased under stress. In this EEG study, we investigated FMT oscillations during a mental arithmetic task that was carried out in a stressful and a neutral control condition. Our results show late- onset, sustained FMT increases during mental arithmetic. In the neutral condition FMT started to increase earlier than in the stress condition. Direct comparison of the conditions quantified this difference by showing stronger FMT increases in the neutral condition in an early time window. Between- subject correlation analysis showed that attenuated FMT under stress was related to slowed reaction times. Our results suggest that FMT is associated with stimulus independent mental processes during the natural and complex PFC- dependent task of mental arithmetic, and is a possible marker for intact PFC function that is disrupted under stress

Brain Correlates of Mathematical Competence in Processing Mathematical Representations

The ability to extract numerical information from different representation formats (e.g., equations, tables, or diagrams) is a key component of mathematical competence but little is known about its neural correlate. Previous studies comparing mathematically less and more competent adults have focused on mental arithmetic and reported differences in left angular gyrus (AG) activity which were interpreted to reflect differential reliance on arithmetic fact retrieval during problem solving. The aim of the present functional magnetic resonance imaging study was to investigate the brain correlates of mathematical competence in a task requiring the processing of typical mathematical representations. Twenty-eight adults of lower and higher mathematical competence worked on a representation matching task in which they had to evaluate whether the numerical information of a symbolic equation matches that of a bar chart. Two task conditions without and one condition with arithmetic demands were administered. Both competence groups performed equally well in the non-arithmetic conditions and only differed in accuracy in the condition requiring calculation. Activation contrasts between the groups revealed consistently stronger left AG activation in the more competent individuals across all three task conditions. The finding of competence-related activation differences independently of arithmetic demands suggests that more and less competent individuals differ in a cognitive process other than arithmetic fact retrieval. Specifically, it is argued that the stronger left AG activity in the more competent adults may reflect their higher proficiency in processing mathematical symbols. Moreover, the study demonstrates competence-related parietal activation differences that were not accompanied by differential experimental performance

Brain Modularity Mediates the Relation between Task Complexity and Performance

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 & Deem, 2015) 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.Comment: 47 pages; 4 figure

Early cortical surface plasticity relates to basic mathematical learning

Children lay the foundation for later academic achievement by acquiring core mathematical abilities in the first school years. Neural reorganization processes associated with individual differences in early mathematical learning, however, are still poorly understood. To fill this research gap, we followed a sample of 5-6-year-old children longitudinally to the end of second grade in school (age 7–8 years) combining magnetic resonance imaging (MRI) with comprehensive behavioral assessments. We report significant links between the rate of neuroplastic change of cortical surface anatomy, and children's early mathematical skills. In particular, most of the behavioral variance (about 73%) of children's visuospatial abilities was explained by the change in cortical thickness in the right superior parietal cortex. Moreover, half of the behavioral variance (about 55%) of children's arithmetic abilities was explained by the change in cortical folding in the right intraparietal sulcus. Additional associations for arithmetic abilities were found for cortical thickness change of the right temporal lobe, and the left middle occipital gyrus. Visuospatial abilities were related to right precentral and supramarginal thickness, as well as right medial frontal gyrus folding plasticity. These effects were independent of other individual differences in IQ, literacy and maternal education. Our findings highlight the critical role of cortical plasticity during the acquisition of fundamental mathematical abilities

Structural and functional largescale brain network dynamics: Examples from mental disorders

Hjernen er organisert i ulike funksjonelle og strukturelle nettverk. Til tross for omfattende forskning, er fremdeles ikke funksjonen og dynamikken i slike nettverk godt forstått. En økt innsikt kan være avgjørende for å forstå symptomer, og mekanismene som kontrollerer disse, hos pasienter med psykiske lidelser som schizofreni. Avhandlingen omfatter tre studier som hver adresserer ulike delmål i forskningen. Den første studien undersøker endringer i strukturelle nettverk hos en gruppe pasienter med schizofreni. Studien viser på gruppenivå at det er dels utbredte strukturelle forskjeller i hvit substans hos pasienter med schizofreni som opplever hørselshallusinasjoner sammenlignet med pasienter som ikke opplever disse hallusinasjonen. For å undersøke mulig samsvarende funksjonelle endringer har det vært behov for først å utvikle en ny tilnærming for å måle forskjeller i dynamikken mellom hjernens nettverk i hvile (DMN) og i aktiv oppgaveløsing av krevende kognitive oppgaver (EMN) hos en gruppe friske frivillige deltakere. I korte trekk, ble tre ulike visuelle, kognitive oppgaver presentert for deltakerne gjennom et fMRI blokk design. Resultatene i studien viste en antikorrelasjon i tid i områder som er involvert i henholdsvis hvile (DMN) og aktiv tilstand (EMN). For å gjøre undersøkelser hos pasienter med psykiske lidelser mindre tidkrevende, beskrives i avhandlingen også en studie som undersøker om hvileområder i hjernen (DMN) som er aktivert nettopp som del av en fMRI blokk design studier overlapper med en tilleggsundersøkelse med femminutters kontinuerlig hvile («resting state»). Sammenligningen er også interessant fra et mer basalforskningsperspektiv fordi en rask endring mellom aktiv tilstand og hvile kanskje bedre reflekterer en realistisk hviletilstand enn den kontinuerlige undersøkelsen som i dag representerer «gullstandarden» i denne type forskning. Resultatene fra studien viste stor grad av overlapp mellom aktiverte områder og at den foreslåtte tilnærmingen dermed kan ha et stort potensial i videre undersøkelser. I sum beskriver forskningen i avhandlingen muligheter for å undersøke strukturelle og funksjonelle nettverk hos pasienter med psykiske lidelser. Avhandlingen viser første resultater hos pasienter med schizofreni som strukturelle forskjeller i hvit substans mellom pasientgrupper avhengig om de opplever hørselshallusinasjoner eller ikke. Slike undersøkelser kan og bør komplementeres med undersøkelser av funksjonelle nettverk slik som foreslått i de andre studiene i avhandlingen, og i sum bidra til et godt rammeverk for videre undersøkelser hos pasienter.The human brain is organized in various networks both functionally and structurally. However, despite the extensive research on brain connectivity, which was made possible due to the development of in vivo brain imaging techniques, the neuroscientific field is still far from fully comprehending networks function and dynamics. Detailed knowledge about the relationship between various brain networks is essential for understanding the function of the healthy brain. However, many studies on mental disorders such as schizophrenia suggest that it might be caused by abnormal brain network functioning and structural aberrations. Therefore, the knowledge of the brain network's dynamics and structure might be critical for revealing the underpinnings of mental disorders such as schizophrenia. The presented thesis had three main goals, resulting in three structural and functional imaging studies. Firstly, the brain's structural connectivity affected by schizophrenia has been investigated to determine the nature and extent of its changes. Hence, Diffusion Tensor Imaging (DTI) and tract-based spatial statistics (TBSS) were employed to explore white matter differences between subtypes of schizophrenia patients compared to healthy controls. This study revealed widespread FA-value reduction in the hallucinating schizophrenia subjects' white matter compared to non-hallucinating ones. Since widespread aberrations of the white matter should affect the function of the large-scale brain networks, the second goal was to explore the two main functional brain networks, Default Mode Network (DMN) and Extrinsic Mode Network (EMN). This is because dysfunction of DMN and EMN networks has been previously suggested to be significant for the generation of symptoms of schizophrenia disorder, such as Auditory Verbal Hallucinations (AVH). Since the concept of EMN is relatively new and not yet deeply explored, and additionally protocol used in that study has not been previously utilized to study EMN and DMN, it was first necessary to test the design in a group of healthy participants. This study used the novel protocol based on the classic block design fMRI experiment with three different visual tasks: mental rotation, working memory, and mental arithmetic. The results of study II proved the existence of the EMN that is anti-correlated with the DMN and is domain-general. Lastly, the neuroimaging studies of the participants suffering from mental disorders such as schizophrenia require relatively short and effective examination protocols. Therefore, the last project investigated both similarities and differences in DMN activity between two experimental designs: block design and resign state. A classic block design experiment would be a good candidate for the investigation reflecting the fluctuating activity of the brain during typical daily activity. The results of Study III showed that the activity of the DMN was generally similar in the two experiments, though with some discrepancies. These differences were in the DMN architecture itself and concerning the relations of the DMN with other brain networks. These findings, in combination with the results of study number two suggest that the block design experiment could be the most effective for studying the function of the brain in schizophrenia. The studies incorporated in that thesis add to the current findings on the white matter alterations in schizophrenia disorder and contribute to a better understanding of the function and dynamics of the large-scale brain networks: EMN and DMN. Last but not least, the performed studies give a good background for future clinical studies on schizophrenia disorder.Doktorgradsavhandlin

Drawing cartoon faces - a functional imaging study of the cognitive neuroscience of drawing

We report a functional imaging study of drawing cartoon faces. Normal, untrained participants were scanned while viewing simple black and white cartoon line-drawings of human faces, retaining them for a short memory interval, and then drawing them without vision of their hand or the paper. Specific encoding and retention of information about the faces was tested for by contrasting these two stages (with display of cartoon faces) against the exploration and retention of random dot stimuli. Drawing was contrasted between conditions in which only memory of a previously viewed face was available versus a condition in which both memory and simultaneous viewing of the cartoon was possible, and versus drawing of a new, previously unseen, face. We show that the encoding of cartoon faces powerfully activates the face sensitive areas of the lateral occipital cortex and the fusiform gyrus, but there is no significant activation in these areas during the retention interval. Activity in both areas was also high when drawing the displayed cartoons. Drawing from memory activates areas in posterior parietal cortex and frontal areas. This activity is consistent with the encoding and retention of the spatial information about the face to be drawn as a visuo-motor action plan, either representing a series of targets for ocular fixation or as spatial targets for the drawing actio