Modulation of a fronto-parietal network in event-based prospective memory: an rTMS study

Event-based prospective memory (PM) is a multi-component process that requires remembering the delayed execution of an intended action in response to a pre-specified PM cue, while being actively engaged in an ongoing task. Some neuroimaging studies have suggested that both prefrontal and parietal areas are involved in the maintenance and realization of delayed intentions. In the present study, transcranial magnetic stimulation (TMS) was used to investigate the causal involvement of frontal and parietal areas in different stages of the PM process (in particular, target checking and intention retrieval), and to determine the specific contribution of these regions to PM performance.Our results demonstrate that repetitive TMS (rTMS) interferes with prospective memory performance when applied at 150-350 ms to the right dorsolateral prefrontal cortex (DLPFC), and at 400-600 ms when applied to the left posterior parietal cortex (PPC).The present study provides clear evidence that the right DLPFC plays a crucial role in early components of the PM process (target checking), while the left PPC seems to be mainly involved in later processes, such as the retrieval of the intended action.     

Determining the acoustic properties of the lens using a high-frequency ultrasonic needle transducer

Ultrasonic parameters including sound velocity and attenuation coefficient have recently been found to be useful in characterizing the cataract lens noninvasively. However, the regional changes of these acoustic parameters in the lens cannot be detected directly by those ultrasonic measurements. This prompted us to fabricate a 46-MHz needle transducer (lead magnesium niobate-lead titanate [PMN-PT] single crystal) with an aperture size of 0.4 mm and a diameter of 0.9 mm for directly measuring the sound velocity and frequency-dependent attenuation coefficient in lenses. These parameters have been shown to be related to the hardness of a cataract, and hence this technique may allow surgeons to detect the acoustic properties of the cataract via a small incision on the cornea before/during phacoemulsification surgery. To verify the performance of the needle transducer, experiments were performed on porcine lenses in which two types of cataracts (nucleus and cortical) were induced artificially. The needle transducer was mounted on a positioning system and its tip was inserted into the lens, allowing the anterior-to-posterior profiles of acoustic parameters along the lens axis to be obtained immediately. The experimental results show that the acoustic parameters are not constant within a single normal lens. The sound velocity and ultrasound attenuation coefficient (at 46 MHz) were 1701.2 ± 8.4 m/s (mean ± SD) and 9.42 ± 0.57 dB/mm, respectively, at the nucleus, and 1597.2 ± 9.6, 1589.3 ± 6.1 m/s and 0.42 ± 0.26 and 0.40 ± 0.33 dB/mm close to the anterior and posterior capsules, respectively. Finally, the data obtained demonstrate that regional variations in the acoustic properties of lenses corresponding to the hardness of different types of cataract can be detected sensitively by a needle transducer. (E-mail: j648816n@ms23.hinet.net)     

Effects of open endotracheal suction on lung volume in infants receiving HFOV

Objective To describe the pattern and magnitude of lung volume change during open endotracheal tube (ETT) suction in infants receiving high-frequency oscillatory ventilation (HFOV). Design Prospective observational clinical study. Setting Tertiary neonatal intensive care unit. Patients and participants Seven intubated and muscle-relaxed newborn infants receiving HFOV. Interventions Open ETT suction was performed for 6 s at −100 mmHg using a 6-F catheter passed to the ETT tip after disconnection from HFOV. The HFOV was then recommenced at the same settings as prior to ETT suction. Measurements and results Change in lung volume (ΔV _L) referenced to baseline lung volume before suction was measured with a calibrated respiratory inductive plethysmography recording from 30 s before until 60 s after ETT suction. In all infants ETT suction resulted in significant loss of lung volume. The mean ΔV _L during suctioning was −13 ml/kg (SD 4 ml/kg) (p < 0.0001 vs. baseline, repeated-measures ANOVA), with a mean 76.5% (SD 14.1%) of this volume loss being related to circuit disconnection. After recommencing HFOV lung volume was rapidly regained with mean ΔV _L at 60 s being 1 ml/kg (SD 4 ml/kg) below baseline (p > 0.05, Tukey post-test). Conclusions Open ETT suction caused a significant but transient loss of lung volume in muscle-relaxed newborn infants receiving HFOV.     

Slow right prefrontal transcranial magnetic stimulation as a treatment for medication-resistant depression: a double-blind, placebo-controlled study

Over the past decade, efforts have been made to assess the positive therapeutic effects of transcranial magnetic stimulation (TMS) by altering the excitability of the brain. We conducted a double-blind, placebo-controlled study to assess the efficacy of right prefrontal slow repetitive TMS in patients with treatment refractory major depression. This pilot study supports the therapeutic potential of rTMS in the low-frequency range of 1 Hz on right prefrontal cortex for the treatment of refractory major depression. Additional studies will be necessary to assess the efficacy of rTMS with different indices (frequency, intensity, and stimulation site) for major depression and other psychiatric diseases.     

rTMS of the prefrontal cortex in the treatment of chronic migraine: a pilot study

A recent fMRI study showed that dorsolateral prefrontal cortex (DLPFC) exerts an inhibitory control on pain pathways in humans. We investigated whether high-frequency rTMS over left DLPFC could ameliorate chronic migraine. Treatment consisted of 12 rTMS sessions, delivered in alternate days over left DLPFC. Sham rTMS was used as placebo. Eleven patients were randomly assigned to the rTMS (n=6) or to the placebo (n=5) treatment. Measures of attack frequency, headache index, number of abortive medications (outcome measures) were recorded in the month before, during and in the month after treatment. Subjects treated by rTMS showed a significant reduction of the outcome measures during and in the month after the treatment as compared to the month before treatment. No significant differences in the outcome measures were observed in the placebo group. High-frequency rTMS over left DLPFC was able to ameliorate chronic migraine. This is in agreement with the suggested role of DLPFC in pain control.     

High-frequency oscillations after status epilepticus: epileptogenesis and seizure genesis

PURPOSE: To investigate the temporal relation between high-frequency oscillations (HFOs) in the dentate gyrus and recurrent spontaneous seizures after intrahippocampal kainite-induced status epilepticus. METHODS: Recording microelectrodes were implanted bilaterally in different regions of hippocampus and entorhinal cortex. A guide cannula for microinjection of kainic acid (KA) was implanted above the right posterior CA3 area of hippocampus. After recording baseline electrical activity, KA (0.4 microg/0.2 microl) was injected. Beginning on the next day, electrographic activity was recorded with video monitoring for seizures every day for 8 h/day for > or = 30 days. RESULTS: Of the 26 rats studied, 19 revealed the appearance of sharp-wave activity and HFOs in the frequency range of 80 to 500 Hz in the dentate gyrus ipsilateral to the KA injection. In the remaining seven rats, no appreciable activity was noted in this frequency range. In some rats with recurrent seizures, HFOs were in the ripple frequency range (100-200 Hz); in others, HFOs were in the fast ripple frequency range (200-500 Hz), or a mixture of both oscillation frequencies was found. The time of detection of the first HFOs after status epilepticus varied between 1 and 30 days, with a mean of 6.3 +/- 2.0 (SEM). Of the 19 rats in which HFO activity appeared, all later developed recurrent spontaneous seizures, whereas none of the rats without HFOs developed seizures. The sooner HFO activity was detected after status epilepticus, the sooner the first spontaneous seizure occurred. A significant inverse relation was found between the time to the first HFO detection and the subsequent rate of spontaneous seizures. CONCLUSIONS: A strong correlation was found between a decreased time to detection of HFOs and an increased rate of spontaneous seizures, as well as with a decrease in the duration of the latent period between KA injection and the detection of spontaneous seizures. Two types of HFOs were found after KA injection, one in the frequency range of 100 to 200 Hz, and the other, in the frequency range of 200 to 500 Hz, and both should be considered pathological, suggesting that both are epileptogenic.     

An experimental randomized study of six different ventilatory modes in a piglet model with normal lungs

A randomized study of 6 ventilatory modes was made in 7 piglets with normal lungs. Using a Servo HFV 970 (prototype system) and a Servo ventilator 900 C the ventilatory modes examined were as follows: SV-20V, i.e. volume-controlled intermittent positive-pressure ventilation (IPPV); SV-20VIosc, i.e. volume-controlled ventilation (IPPV) with superimposed inspiratory oscillations; and SV-20VEf, i.e. volume-controlled ventilation (IPPV) with expiratory flush of fresh gas; HFV-60 denotes low-compressive high-frequency positive-pressure ventilation (HFPPV) and HVF-20 denotes low-compressive volume-controlled intermittent positive-pressure ventilation; and SV-20P denotes pressure-controlled intermittent positive-pressure ventilation. With all modes of ventilation a PEEP of 7.5 cm H₂O was used. In the abbreviations used, the number denotes the ventilatory frequency in breaths per minute (bpm). HFV indicates that all gas was delivered via the HFV 970 unit. The ventilatory modes described above were applied randomly for at least 30 min, aiming for a normoventilatory steady state. The HFV-60 and the HFV-20 modes gave lower peak airway pressures, 12–13 cm H₂O compared to approximately 17 cm H₂O for the other ventilatory modes. Also the mean airway pressures were lower with the HFV modes 8–9 cm H₂O compared to 11–14 cm H₂O for the other modes. The gas distibution was evaluated by N₂ washout and a modified lung clearance index. All modes showed N₂ wash-out according to a two-compartment model. The SV-20P mode had the fastest wash-out, but the HFV-60 and HFV-20 ventilatory modes also showed a faster N₂ wash-out than the others. Regarding the lung clearance index, the SV-20P, HFV-60 and HFV-20 modes showed better indices than the other modes. No relationship was found between the ventilatory mode and extravascular lung water, and there were no differences in the hemodynamic variables.This study was supported by the Swedish Medical Research Council (project 4252), Sweden     

High-frequency hearing risk of operators of industrial ultrasonic devices

Summary Sound and ultrasound emitted by industrial ultrasonic (Uls) devices exceed the known proposed hygienic limits, especially for frequencies 10–20 kHz. The consequence of this may be a negative influence of this energy on the auditory function in the high-frequency hearing range. To determine the hearing risk to Uls operators, an adequate method for testing the hearing threshold from 10-20 kHz has been developed. In order to get reference values, 189 non-exposed persons were tested. On this basis, the hearing thresholds of 55 operators for frequencies 500–20,000 Hz were evaluated. In addition to threshold elevations in the range 10–20 kHz, a decreasing number of subjects responding to stimuli at the highest audible frequencies was observed. The threshold shift at 10–20 kHz of subjects exposed to sound and ultrasound emitted by Uls-devices depends upon the physical parameters of the sound spectrum, time on the job and daily exposure time. No abnormalities were found in the hearing range 500–8000 Hz.     

One-sided high-frequency oscillating ventilation in the treatment of neonatal unilateral pulmonary emphysema

We describe a preterm infant (31 weeks' gestation) with unilateral pulmonary emphysema. Bronchoscopy showed no bronchial obstruction. After 20 days of right-sided high-frequency oscillating ventilation, the emphysema in the left lung had completely resolved and the patient could be extubated.