Anja Ischebeck

How specifically do we learn? Imaging the learning of multiplication and subtraction.

The present functional magnetic resonance imaging (fMRI) study investigates modifications of brain activation patterns related to the training of two different arithmetic operations, multiplication and subtraction. Healthy young adults were trained in five sessions to answer multiplication and subtraction problems. In the following fMRI session, trained and new untrained problems closely matched for difficulty were presented in blocked order. Contrasts between untrained and trained operations showed stronger activation of inferior frontal and parietal regions, especially along the banks of the intraparietal sulcus. The reverse contrasts, trained minus untrained operations, yielded significantly higher activation in the left angular gyrus for multiplication but no significantly activated area for subtraction. This suggests that training leads to a reduction of general purpose processes, such as working memory and executive control in both operations, indicated by the decrease of activation in inferior frontal areas. For multiplication, however, the increase of activation in the left angular gyrus indicates a switching of cognitive processes. Trained subtraction therefore seems to lead to faster and more efficient strategies, while trained multiplication showed a shift from quantity-based processing (supported by the areas along the intraparietal sulci) to more automatic retrieval (supported by the left angular gyrus). The same training method caused changes in brain activation patterns that depended on the given operation. The effects of learning on the brain therefore seem not only to depend on the method of learning but also on its content.

Neural correlates of distance and congruity effects in a numerical Stroop task: an event-related fMRI study

This study aimed at investigating the neural correlates of a number-size congruity task. Using an event-related fMRI design, we presented one-digit number pairs to 17 participants in a number-size interference task that required subjects to focus on one stimulus property (e.g., numerical size) and to ignore the other (physical size). In different blocks, participants were asked to decide which digit of a digit pair was numerically larger (numerical comparison task) or physically larger (physical comparison task). Stimuli were classified into three categories: (a) congruent: physical and numerical comparison leads to the same response; (b) incongruent: physical and numerical comparison leads to different responses; (c) neutral: the stimuli differ only with regard to the task-relevant stimulus property. Behavioral results reflect robust distance effects (quicker reaction times for long distances relative to short ones) and size congruity effects (longer reaction times for incongruent relative to congruent stimuli) in both tasks. Imaging results reveal that-compared to congruent trials-incongruent trials led to a stronger activation in the dorsolateral prefrontal cortex and the anterior cingulate cortex, areas associated with attentional control. The distance effect (neutral condition only) led to a stronger activation in bilateral parietal areas including the intraparietal sulcus (IPS).

Learning by strategies and learning by drill--evidence from an fMRI study.

The present fMRI study investigates, first, whether learning new arithmetic operations is reflected by changing cerebral activation patterns, and second, whether different learning methods lead to differential modifications of brain activation. In a controlled design, subjects were trained over a week on two new complex arithmetic operations, one operation trained by the application of back-up strategies, i.e., a sequence of arithmetic operations, the other by drill, i.e., by learning the association between the operands and the result. In the following fMRI session, new untrained items, items trained by strategy and items trained by drill, were assessed using an event-related design. Untrained items as compared to trained showed large bilateral parietal activations, with the focus of activation along the right intraparietal sulcus. Further foci of activation were found in both inferior frontal gyri. The reverse contrast, trained vs. untrained, showed a more focused activation pattern with activation in both angular gyri. As suggested by the specific activation patterns, newly acquired expertise was implemented in previously existing networks of arithmetic processing and memory. Comparisons between drill and strategy conditions suggest that successful retrieval was associated with different brain activation patterns reflecting the underlying learning methods. While the drill condition more strongly activated medial parietal regions extending to the left angular gyrus, the strategy condition was associated to the activation of the precuneus which may be accounted for by visual imagery in memory retrieval.

Imaging early practice effects in arithmetic.

A better understanding of learning processes in arithmetic in healthy adults can guide research into learning disabilities such as dyscalculia. The goal of the present functional magnetic resonance imaging study was to investigate the ongoing process of learning itself. No training was provided prior to the scanning session. Training consisted in a higher frequency of repetition for one set of complex multiplication problems (repeated) and a lower frequency for the other set (novel). Repeated and novel problems were presented randomly in an event-related design. We observed activation decreases due to training in fronto-parietal areas and the caudate nucleus, and activation increases in temporo-parietal regions such as the left angular gyrus. Training effects became significant after approximately eight repetitions of a problem and remained stable over the course of the experiment. The change in brain activation patterns observed was similar to the results of previous neuroimaging studies investigating training effects in arithmetic after a week of extensive training. The paradigm employed seems to be a suitably sensitive tool to investigate and compare learning processes on group level for different populations. Furthermore, on a more general level, the early and robust changes in brain activation in healthy adults observed here indicate that repeating stimuli can profoundly and quickly affect fMRI results.

Gender differences in regional cerebral activity during the perception of emotion: A functional MRI study

Whether men activate different brain regions during various emotions compared to women or whether gender differences exist in transient emotional states has been the subject of only few studies. We used event-related functional magnetic resonance imaging (fMRI) to investigate gender differences during the perception of positive or negative emotions. The experiment comprised two emotional conditions (pleasant/unpleasant visual stimuli) during which fMRI data were acquired. Altogether, 38 healthy volunteers (19 males, 19 females) were investigated. When subtracting the activation values of men from those of women, suprathreshold positive signal changes were detected in the right posterior cingulate, the left putamen and the left cerebellum during positive mood induction, and in bilateral superior temporal gyri and cerebellar vermis during negative mood induction. The subtraction of activation values of women from those of men yielded no significant differences. Our findings suggest gender-related neural responses to emotional stimuli and could contribute to the understanding of mechanisms underlying gender-related vulnerability of the prevalence and severity of neuropsychiatric disorders.

Effective connectivity of the left BA 44, BA 45, and inferior temporal gyrus during lexical and phonological decisions identified with DCM

Distinct regions in the left inferior frontal gyrus (IFG) preferentially support the processing of different word‐types (e.g., real words, pseudowords) and tasks (e.g., lexical decisions, phonological decisions) in visual word recognition. However, the functional connectivity underlying the task‐related specialisation of regions in the left IFG is not yet well understood. In this study we investigated the neural mechanisms driving the interaction of WORD‐TYPE (real word vs. pseudoword) and TASK (lexical vs. phonological decision) in Brodmanns area (BA) 45 in the left IFG using dynamic causal modelling (DCM). Four different models were compared, all of which included left BA44, left BA45, and left inferior temporal gyrus (ITG). In each model, the visual presentation of words and pseudowords is assumed to directly evoke activity in the ITG and is then thought to be subsequently propagated to BA45 and to BA44 via direct intrinsic connections. The models differed with regard to which connections were modulated by the different tasks. Both tasks were assumed to either modulate the ITG_BA45 connection (Model #1), or the BA44_BA45 connection (Model #2), or both connections in parallel (Model #3). In Model #4 lexical decisions modulated the ITG_BA45 connection, whereas phonological decisions modulated the BA44_BA45 connection. Bayesian model selection revealed a superiority of Model #1. In this model, the strength of the ITG_BA45 connection was enhanced during lexical decisions. This model is in line with the hypothesis that left BA 45 supports explicit lexical decisions during visual word recognition based on lexical access in the ITG. Hum Brain Mapp, 2009.

Neural correlates of the number-size interference task in children.

In this functional magnetic resonance imaging study, 17 children were asked to make numerical and physical magnitude classifications while ignoring the other stimulus dimension (number–size interference task). Digit pairs were either incongruent (3 8) or neutral (3 8). Generally, numerical magnitude interferes with font size (congruity effect). Moreover, relative to numerically adjacent digits far ones yield quicker responses (distance effect). Behaviourally, robust distance and congruity effects were observed in both tasks. Imaging baseline contrasts revealed activations in frontal, parietal, occipital and cerebellar areas bilaterally. Different from results usually reported for adults, smaller distances activated frontal, but not (intra-)parietal areas in children. Congruity effects became significant only in physical comparisons. Thus, even with comparable behavioural performance, cerebral activation patterns may differ substantially between children and adults.

Does caffeine modulate verbal working memory processes? An fMRI study.

To assess the effect of caffeine on the functional MRI signal during a 2-back verbal working memory task, we examined blood oxygenation level-dependent regional brain activity in 15 healthy right-handed males. The subjects, all moderate caffeine consumers, underwent two scanning sessions on a 1.5-T MR-Scanner separated by a 24- to 48-h interval. Each participant received either placebo or 100 mg caffeine 20 min prior to the performance of the working memory task in blinded crossover fashion. The study was implemented as a blocked-design. Analysis was performed using SPM2. In both conditions, the characteristic working memory network of frontoparietal cortical activation including the precuneus and the anterior cingulate could be shown. In comparison to placebo, caffeine caused an increased response in the bilateral medial frontopolar cortex (BA 10), extending to the right anterior cingulate cortex (BA 32). These results suggest that caffeine modulates neuronal activity as evidenced by fMRI signal changes in a network of brain areas associated with executive and attentional functions during working memory processes.

Stimulating creativity via the exposure to other people's ideas

As it is the case in brainstorming, each single idea a person generates to a specific problem may stimulate new ideas or solutions in others. In this fMRI study, we investigate the effects of cognitive stimulation via the exposure to other peoples ideas on the originality of generated ideas. Participants are requested to generate alternative uses of conventional everyday objects subsequent to a short cognitive stimulation intervention in which they are exposed to other ideas, which were either common or highly original. In a control condition, meaningless pseudowords are shown. Results suggest that cognitive stimulation via common or moderately creative ideas was effective in improving creativity. At the neurophysiological level, temporo‐parietal brain regions (primarily right‐hemispheric) turned out to be particularly sensitive to cognitive stimulation, possibly indicating that cognitive stimulation via relevant memory cues results in a state of heightened focused attention to memory that facilitates efficient retrieval and recombination of existing knowledge. Hum Brain Mapp, 2012.

Fact learning in complex arithmetic and figural-spatial tasks: the role of the angular gyrus and its relation to mathematical competence.

Neuroimaging studies have revealed a strong link between mental calculation and the angular gyrus (AG) which has been interpreted to reflect arithmetic fact retrieval. Moreover, a stronger AG activation in individuals with higher mathematical competence has been reported. The present fMRI study investigates the specificity of the AG for arithmetic fact learning and the interplay between training and mathematical competence on brain activation. Adults of lower and higher mathematical competence underwent a five‐day training on sets of complex multiplication and figural‐spatial problems. In the following fMRI test session, trained and untrained problems were presented. Similar training effects were observed in both problem types, consisting of AG activation increases bilaterally and wide‐spread activation decreases in frontal and parietal regions. This finding indicates that the AG is not specifically involved in the learning of arithmetic facts. Competence‐related differences in the AG only emerged in untrained but not in trained multiplication problems. The relation between AG activation and mathematical competence in arithmetic problem solving therefore seems to be due to differences in arithmetic fact retrieval which can be attenuated through training. Hum Brain Mapp 2009.