Changes in fMRI BOLD response to increasing and decreasing task difficulty during auditory perception of temporal order.

We have discovered changes in brain activation during difficult and easy milliseconds timing. Structures engaged in difficult and easier auditory temporal-order judgment were identified in 17 young healthy listeners presented with paired-white-noises of different durations. Within each pair, a short (10 ms) and a long (50 ms) noise was separated by a silent gap of 10, 60 or 160 ms, corresponding to three levels of task difficulty, i.e. difficult, moderate and easy conditions, respectively. A block design paradigm was applied. In temporal-order judgment task subjects were required to define the order of noises within each pair, i.e. short-long or long-short. In the control task they only detected the presentation of the stimulus pair. A multiple regression with 'task difficulty' as a regressor ('difficult', 'moderate', 'easy') showed dynamic changes in neural activity. Increasing activations accompanying increased task difficulty were found in both bilateral inferior parietal lobuli and inferior frontal gyri, thus, in classic regions related to attentional and working memory processes. Conversely, decreased task difficulty was accompanied by increasing involvement of more specific timing areas, namely bilateral medial frontal gyri and left cerebellum. These findings strongly suggest engagement of different neural networks in difficult or easier timing and indicate a framework for understanding timing representation in the brain.

[P-wave ekg averaging technique--a new method of selecting patients with paroxysmal atrial fibrillation]. / Technika usredniania zalamka P ekg--nowa metoda wyodrebniania chorych z napadowym migotaniem przedsionków.

The aim of study was to assess the value of signal averaged ecg for detection of patients (pts) at risk for paroxysmal atrial fibrillation (paf). We examined three groups of pts: group I-41 pts with nonvalvular paf, group II-20 pts with hypertension and/or ischemic heart disease without paf and group 3-26 health persons, without organic heart disease. In all pts the signal-averaged electrocardiogram triggered by P waves was recorded. Seven parameters of the spatial magnitude of filtered P wave were measured. Significant difference between group I and group II or III was found in most parameters. Using the method of multidimensional variance analysis we constructed "the diagnostic vector" in multidimensional parameters space, which was used to determine patients belonging to group. Total percent of right decision was 85%. These findings suggest that pts at risk for paf could be detected while in sinus rhythm by using the P wave-triggered signal-averaged ecg.