[Exercise-induced left bundle branch block with chest pain related to antimalarial prophylaxis with chloroquine]. / Bloc de branche gauche douloureux d'effort associé à la chimioprophylaxie antipaludique par chloroquine.

Left bundle branch block (LBBB) during exercise can be associated with chest pain. Though this association is mostly correlated with an underlying coronary artery disease, painful LBBB has been described in patients with normal coronary arteries. We report a case of exercise-induced LBBB with typical angina pectoris related to antimalarial prophylaxis with chloroquine in a 66-year old woman with normal coronary arteries, which was reversed after treatment discontinuation. The effect of chloroquine on the electrophysiological properties of nodal cardiac tissue is responsible for this rate-dependent LBBB. Precautions for future antimalarial prophylaxis are also discussed.

Influence of cognitive strategies on the pattern of cortical activation during mental subtraction. A functional imaging study in human subjects.

Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investigate the influence of cognitive strategies on cortical activation during mental calculation. Twenty-nine right-handed subjects performed a serial subtraction of prime numbers. Even though a common corpus of brain areas was activated during this mental calculation, differences appeared between subjects in function of their spontaneous cognitive strategy. In subjects using a so called verbal strategy (n=15), the main activation was located in the whole left dorsolateral frontal cortex with a little activation of the inferior parietal cortex. In subjects using a so called visual strategy (n=14), a bilateral activation in the prefrontal cortex and a high activation in the left inferior parietal cortex were observed. These results demonstrate that numbers are processed through a distributed network of cortical areas, the lateralization of which is clearly influenced by subject strategy.

A functional magnetic resonance imaging study of mental subtraction in human subjects.

The neuronal network involved in a precise type of calculation procedure, mental subtraction, was investigated by means of functional magnetic resonance imaging. Two tasks were used requiring covert production of numbers: (1) with calculation; (2) without calculation. During the first task, activation was observed in the left dorsolateral prefrontal and premotor cortices, in Broca's area and bilaterally in the inferior parietal cortex. During the second task, activation was mainly observed in Broca's area and to a less extent in the left prefrontal and premotor cortices. Statistical comparison of data in the two situations revealed that the procedure of mental subtraction is mediated by a distributed system which includes predominantly the left dorsolateral prefrontal cortex and the inferior parietal cortex bilaterally.

[Influence of individual strategies on brain activation patterns during cognitive tasks]. / Influence des stratégies individuelles sur le patron d'activation cérébrale au cours de tâches cognitives.

Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investigate the influence of cognitive strategies on cortical activation during mental calculation. Twenty-nine right-handed subjects performed a serial subtraction of prime numbers. Data were analyzed taking into account whether the spontaneous strategy of subjects was verbal (n = 15) or visual (n = 14). Even thought a common corpus of brain areas was activated during this mental calculation task, i.e. the dorsolateral prefrontal, premotor and parietal cortices, and Broca's area, differences appeared between the two groups of subjects. In subjects using a verbal strategy, the main activation was located in the whole left dorsolateral frontal cortex with a little activation of the inferior parietal cortices. In subjects using a visual strategy, a bilateral activation in the prefrontal cortex and a high activation in the left inferior parietal cortex were observed. These results demonstrate that numbers are processed through a distributed network of cortical areas, the lateralization of which is clearly influenced by subject strategy. Taken together this data reveals a functional interaction between the left inferior parietal cortex and the right prefrontal cortex in the visuo-spatial sketchpad for number processing. This network could be involved in sustained selective attention to mental numerical images generated in the left inferior parietal cortex.