Laura Zamarian

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.

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.

Long-Term Enhancement of Brain Function and Cognition Using Cognitive Training and Brain Stimulation

Summary Noninvasive brain stimulation has shown considerable promise for enhancing cognitive functions by the long-term manipulation of neuroplasticity [1–3]. However, the observation of such improvements has been focused at the behavioral level, and enhancements largely restricted to the performance of basic tasks. Here, we investigate whether transcranial random noise stimulation (TRNS) can improve learning and subsequent performance on complex arithmetic tasks. TRNS of the bilateral dorsolateral prefrontal cortex (DLPFC), a key area in arithmetic [4, 5], was uniquely coupled with near-infrared spectroscopy (NIRS) to measure online hemodynamic responses within the prefrontal cortex. Five consecutive days of TRNS-accompanied cognitive training enhanced the speed of both calculation- and memory-recall-based arithmetic learning. These behavioral improvements were associated with defined hemodynamic responses consistent with more efficient neurovascular coupling within the left DLPFC. Testing 6 months after training revealed long-lasting behavioral and physiological modifications in the stimulated group relative to sham controls for trained and nontrained calculation material. These results demonstrate that, depending on the learning regime, TRNS can induce long-term enhancement of cognitive and brain functions. Such findings have significant implications for basic and translational neuroscience, highlighting TRNS as a viable approach to enhancing learning and high-level cognition by the long-term modulation of neuroplasticity.

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.

Number processing in posterior cortical atrophy--a neuropsycholgical case study.

Posterior cortical atrophy (PCA) is an uncommon syndrome of dementia with early onset, characterised by disorders of higher visual function, variable symptoms of Balints syndrome, visual agnosia, alexia, agraphia, finger agnosia, right-left disorientation and dyscalculia [Benson D. F., Davis R. J., & Snyder B. D. (1988). Posterior cortical atrophy. Archives of Neurology, 45, 789-793]. In a single case study specific numerical deficits were observed which may be predicted by parietal neurodegeneration (more pronounced on the right side; verified by SPECT). Besides impairments in all tasks involving visuo-spatial abilities (e.g., dot counting, analog number scale task), deficits appeared in tasks requiring access to an internal representation of numbers such as mental number bisection, approximation, estimation and semantic facts. In number comparison an increased distance effect was found. In simple arithmetic, a striking dissociation between operations was found-multiplication and addition facts being preserved at a superficial level, subtraction and division being severely impaired. The study confirms the close relation between spatial and numerical processing and highlights the modular organisation of the semantic system (number semantics impaired). Moreover, the study adds evidence about the clinical manifestation of the particular degenerative syndrome.

Flexible transfer of knowledge in mental arithmetic — An fMRI study

Recent imaging studies could show that fact acquisition in arithmetic is associated with decreasing activation in several frontal and parietal areas, and relatively increasing activation within the angular gyrus, indicating a switch from direct calculation to retrieval of a learned fact from memory. So far, however, little is known about the transfer of learned facts between arithmetic operations. The aim of the present fMRI study was to investigate whether and how newly acquired arithmetic knowledge might transfer from trained multiplication problems to related division problems. On the day before scanning, ten complex multiplication problems were trained. Within the scanner, trained multiplication problems were compared with untrained multiplication problems, and division problems related to multiplication (transfer condition) were compared with unrelated division problems (no-transfer condition). Replicating earlier results, untrained multiplication problems activated several frontal and parietal brain areas more strongly than trained multiplication problems, while trained multiplication problems showed relatively stronger activation in the left angular gyrus than untrained multiplication problems. Concerning division, an ROI analysis indicated that activation in the left angular gyrus was relatively stronger for the transfer condition than for the no-transfer condition. We also observed distinct inter-individual differences with regard to transfer that modulated activation within the left angular gyrus. Activation within the left angular gyrus was generally higher for participants who showed a transfer effect for division problems. In conclusion, the present study yielded some evidence that successful transfer of knowledge between arithmetic operations is accompanied by modifications of brain activation patterns. The left angular gyrus seems not only to be involved in the retrieval of stored arithmetic facts, but also in the transfer between arithmetic operations.

Executive functions, categorization of probabilities, and learning from feedback: What does really matter for decision making under explicit risk conditions?

In two experiments with healthy subjects, we used the Game of Dice Task (GDT), the Probability-Associated Gambling (PAG) task, the Iowa Gambling Task (IGT), and executive-function and logical thinking tasks to shed light on the underlying processes of decision making under risk. Results indicate that handling probabilities, as in the PAG task, is an important ingredient of GDT performance. Executive functions and logical thinking also play major roles in deciding in the GDT. Implicit feedback learning, as measured by the IGT, has little impact. Results suggest that good probability handling may compensate for the effects of weak executive functions in decisions under risk.

Validation of the Innsbruck REM sleep behavior disorder inventory

A diagnosis of definite REM sleep behavior disorder requires both a positive history for REM sleep behavior disorder and polysomnographic demonstration of REM sleep without atonia. To improve and facilitate screening for REM sleep behavior disorder, there is a need for simple clinical tools with sufficient sensitivity and specificity for the identification of subjects with probable REM sleep behavior disorder. We developed a short REM sleep behavior disorder screening questionnaire with 7 REM sleep behavior disorder– and 2 non‐REM sleep behavior disorder–specific control items and performed a validation study in 70 REM sleep behavior disorder subjects and 140 sleep disorder controls. Response patterns to all 7 REM sleep behavior disorder–specific items differed between REM sleep behavior disorder and non‐REM sleep behavior disorder patients (all P < 0.05), whereas the 2 non‐REM sleep behavior disorder–specific control items did not differentiate between REM sleep behavior disorder and non‐REM sleep behavior disorder (all P > .05). In 5 of the 7 REM sleep behavior disorder–specific items, AUC was greater than 0.700. These 5 items were included in the Innsbruck REM sleep behavior disorder inventory. In this questionnaire, a cutoff of 0.25 (number of positive symptoms divided by number of answered questions) had a sensitivity of 0.914 and a specificity of 0.857 for both idiopathic and Parkinsons‐related REM sleep behavior disorder (AUC, 0.886). The Innsbruck REM sleep behavior disorder inventory is a promising, easy‐to‐use, short screening tool for REM sleep behavior disorder with excellent sensitivity and specificity for both idiopathic and Parkinsons‐related REM sleep behavior disorder.

Are Numbers Special? Comparing the Generation of Verbal Materials From Ordered Categories (Months) to Numbers and Other Categories (Animals) in an fMRI Study

Months, days of the week, and numbers differ from other verbal concepts because they are ordered in a sequence, whereas no order is imposed on members of other categories, such as animals or tools. Recent studies suggest that numbers activate a representation of their quantity within the intraparietal sulcus (IPS) automatically, that is, in tasks that do not require the processing of quantity. It is unclear, however, whether ordered verbal materials in general and not only numbers activate the IPS in such tasks. In the present functional magnetic resonance imaging study word generation of months, numbers, and animals were compared. Word generation of numbers and nonnumerical materials from an ordered category (months) activated the IPS more strongly than generating items from a not‐ordered category such as animals or the verbal control conditions. An ROI analysis of three subregions within the anterior IPS revealed that the most anterior and lateral of these regions, human intraparietal area hIP2, shows a greater sensitivity to ordered materials than the other two areas, hIP1 and hIP3. Interestingly, no difference in activation was observed within the IPS between numbers and months suggesting that the activation of the IPS might not be modulated by the additional quantity information carried by numbers. Hum Brain Mapp, 2008.

Knowing 7 × 8, but not the meaning of ‘elephant’: Evidence for the dissociation between numerical and non-numerical semantic knowledge

Patients affected by semantic dementia (SD) and other severe cognitive deficits may show preserved numerical skills, including the retrieval of multiplication facts from long-term memory. No studies so far specifically investigated the network of arithmetic facts in semantic dementia. Thus, it is unknown whether preserved multiplication in SD truly reflects intact semantic knowledge or preserved retrieval of verbal sequences (just as the recitation of rhymes or poems). In the present study a patient (SG) with SD underwent an extensive assessment of number processing and calculation abilities. In particular, multiplication knowledge was investigated through a series of computerised tasks (production task, multiple-choice task, number bisection task with multiplicative triplets, number-matching task). SG demonstrated excellent performance in all number processing and calculation tasks. In computerised tasks tapping multiplication fact knowledge, SG was as accurate and fast as healthy controls. Analyses on individual regression slopes indicated that SGs reaction time effects (problem-size effect, problem-difficulty effect, interference effects, and facilitation effect) were comparable to those found in controls in each task. These results add new evidence to the independence of numerical knowledge from other semantic information and provide further insight into the organisation of stored arithmetic knowledge.