25 Hz has been advocated as a means to avoid confounding and to standardize measurements in short-term investigations of autonomic cardiovascular regulation. Controversy remains, however, as to whether it causes any alteration in autonomic control. We addressed this issue in 40 supine, middle-aged, healthy volunteers by assessing the changes induced by PB (0.25 Hz for 8 min) on 1) ventilatory parameters, 2) the indexes of autonomic control of cardiovascular function, and 3) the spectral indexes of cardiovascular variability. Subjects were grouped into group 1 (n ϭ 31), if spontaneous breathing was regular and within the high-frequency (HF) band (0.15-0.45 Hz), or group 2 (n ϭ 9), if it was irregular or slow (Ͻ0.15 Hz). In both groups, PB was accompanied by an increase in minute ventilation (both groups, P Ͻ 0.01), whereas tidal volume increased only in group 1 (P ϭ 0.0003). End-tidal CO 2 decreased by [median (lower quartile, upper quartile)] Ϫ0.2 (Ϫ0.5, Ϫ0.1)% (group 1, P Ͻ 0.0001) and Ϫ0.6 (Ϫ0.8, Ϫ0.5)% (group 2, P ϭ 0.008). Mean R-R interval and systolic and diastolic pressure remained remarkably stable (all P Ն 0.13, both groups). No significant changes were observed in spectral indexes of R-R and pressure variability (all P Ն 0.12, measured only in group 1 to avoid confounding), except in the HF power of pressure signals, which significantly increased (all P Ͻ 0.05) in association with increased tidal volume. In conclusion, PB at 0.25 Hz causes a slight hyperventilation and does not affect traditional indexes of autonomic control or, in subjects with spontaneous breathing in the HF band, most relevant spectral indexes of cardiovascular variability. These findings support the notion that PB does not alter cardiovascular autonomic regulation compared with spontaneous breathing.heart rate variability; controlled breathing; baroreflex sensitivity; spectral analysis A LARGE NUMBER OF STUDIES (9,19,35) have been published in the last two decades using the analysis of spontaneous oscillations of pulse interval and blood pressure as an indirect, quantitative, and noninvasive means to assess the autonomic control of cardiovascular function. Both physiopathological investigations and clinical applications have been carried out, and a rich variety of algorithms for analysis have been proposed. Among them, those based on spectral analysis of individual signals and of their mutual interrelationships have gained the highest interest, mainly because they would enable an interpretative link between different oscillatory components and specific physiological mechanisms (18,23,37). To control for confounding factors that might affect measured parameters, cardiovascular variability signals have been mostly collected during short-term recordings performed in dedicated laboratories, where environmental and physical conditions have been kept constant and emotional and sensorial stimuli have been avoided. Less attention, however, has been paid to respiration, despite much evidence that breathing characteristics (frequency, amplit...

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Episodic memory is critical to daily life functioning. This type of declarative memory declines with age and is the earliest cognitive function to be compromised in Alzheimer’s disease (AD). Subjective memory complaints are commonly reported by older adults and have been considered a risk factor for developing AD. The possibilities for prevention of memory disorders in older adults have increased substantially in recent years. Previous studies have shown that anodal transcranial Direct Current Stimulation (tDCS) applied over the left lateral prefrontal cortex (PFC) after a contextual reminder strengthened existing verbal episodic memories, conceivably through reconsolidation, in elderly people. In this study, we hypothesized that anodal tDCS applied over the left lateral PFC after a contextual reminder would improve delayed memory retrieval relative to placebo (sham) stimulation in elderly individuals with SMC. Twenty-two subjects learned a list of words. Twenty-four hour later, tDCS (anodal or placebo) was applied over the left lateral PFC after a contextual reminder. Memory retrieval was tested 48h and 30 days later. These findings showed that anodal tDCS over the left lateral PFC strengthened existing episodic memories, a behavioral effect documented by improved recognition up to 30 days, relative to placebo stimulation. This study suggests that tDCS after a contextual reminder can induce long-lasting beneficial effects by facilitating the consolidation processes and opens up the possibility to design specific non-invasive interventions aimed at preventing memory decline in this at-risk population.