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At least 685 records · Page 38Linked to original sources
PubMed1990

[Effect of hyperlipidemia and hypothyroidism on auditory evoked brain stem responses].

Temporary changes in audiometry have been reported in hypercholesterolaemia and in hypo- and hyperthyroidism. The purpose of the present prospective and controlled study was to record changes in conduction time of auditory brain-stem response (ABR) in patients with hyperlipidaemia and hypothyroidism before and after therapy over a period of 6 months. The acoustic evoked brain-stem response Jewett waves I-V were delayed in patients with hypercholesterolaemia, hypertrigliceridaemia and hypothyroidism in comparison with an age-matched control group. The changes in pure-tone threshold and brain-stem responses correlated with the degree of hyperlipidaemia or hypothyroidism. After treatment the brain-stem responses of hypothyroid patients tended to return to normal, and in a few cases normal pure-tone thresholds were achieved. Of the patients with hypercholesterolaemia and hypertrigliceridaemia, 28% had improvements in pure-tone thresholds, whereas no significant changes were found in the ABR following therapy.

Auditory Threshold↗
PubMed2005

Spatio-temporal activation of cyclic AMP response element-binding protein, activity-regulated cytoskeletal-associated protein and brain-derived nerve growth factor: a mechanism for pontine-wave generator activation-dependent two-way active-avoidance memory processing in the rat.

The present study explored possible physiological and molecular mechanisms of pontine-wave (P-wave) generator activation-dependent memory processing in the rat using a two-way active-avoidance learning paradigm. The results show that learning training increased rapid eye movement sleep and activated brainstem cells in the P-wave generator. During this period, there was a time-dependent increase in phosphorylation of cAMP response element-binding protein (CREB) in the dorsal hippocampus and amygdala and increased synthesis of activity-regulated cytoskeletal-associated protein (Arc) in the dorsal hippocampus, amygdala, frontal cortex and occipital cortex. Learning training also increased synthesis of brain-derived nerve growth factor (BDNF) in the occipital cortex, amygdala and dorsal hippocampus at different time intervals. During this time, the levels of nerve growth factor did not change. The results also show that the increase in rapid eye movement sleep P-wave density during the post-training 3-h recording session is positively correlated with the increased levels of phosphorylated CREB, BDNF and Arc in the dorsal hippocampus. These results suggest that memory processing of two-way active-avoidance learning may involve excitation of P-wave-generating cells in the brainstem and increased expression of phosphorylated CREB, Arc and BDNF in a time-dependent manner in the forebrain. These dynamic changes in cellular and molecular features provide considerable insight into the mechanisms of the P-wave generator activation-dependent memory consolidation process.

Amygdala↗
PubMed2005

Effects of light physical exercise on sleep in middle-aged rats.

The effects of physical activity on sleep were evaluated in 12-month-old rats. The animals (n = 18) were induced to walk or run for 45 min in a rota-rod treadmill while control mates remained in their home cages. Immediately after the trial, they were left free to sleep for four hours, during which their electroencephalographic activity was recorded. Baseline electroencephalogram showed no differences among groups in sleep parameters and spike wave discharges during wakefulness in all rats. Sleep variables and spike wave discharges remained constant in the controls over times. On the contrary, Student's t-test for paired data indicated a decrease in spike wave discharges in both walking and running rats while paradoxical sleep rose parallel with slow wave sleep in walking animals but declined in running rats, in spite of an increment in slow wave sleep. The results seem to indicate that: i) light exercise improves sleep quality in middle aged rats, provided it is not stressful and ii) physical activity supplies important benefits to waking brain by reducing spike wave discharges.

Age Factors↗
PubMed1991

Stable bimodal response to cholinomimetic drugs in Alzheimer's disease. Brain mapping correlates.

We investigated quantitative EEG brain mapping as a physiologic marker of drug response while studying the stability of intersubject variability in patients with Alzheimer's disease (AD) who were receiving bethanechol through intracerebroventricular (ICV) shunts. Two of the patients had previously demonstrated cognitive and behavioral improvements on medication; the third had cognitive deterioration complicated by agitated depression. All three patients were reexamined in a dose-response paradigm. Serial brain mapping examinations were performed along with brief cognitive testing. All patients showed drug responses that were comparable with responses during their initial dose-response phase. There were strong linear correlations between global decreases in 2 to 6 Hz slow-wave activity and cognitive improvement. Brain mapping demonstrated that slowing decreased in magnitude and field with increasing dose until optimal dose was reached; with supra-optimal doses, the magnitude and field of the slowing increased dramatically. These results suggest that the quality of cholinomimetic drug responses are stable over time in individual patients, and that magnitude and pattern of slow-wave activity as measured by brain mapping may be useful in monitoring treatment with cholinomimetic agents.

Alzheimer Disease↗
PubMed1999

Non-linear analysis of the rhythmic activity in rodent brains.

This paper discusses the employment of non-parametric non-linear prediction algorithms to investigate non-linear dynamics in the rhythmic brain activity of rats. Three algorithms (Sugihara-May Simplex, K-neighbour and Casdagli's) were tested yielding similar prediction results which--when subject to a suitable bootstrap based t-tests--revealed that the theta waves recorded in rat brains cannot have their intrinsic non-linearity dismissed at a significance of 0.05.

Algorithms↗
PubMed1988

Ultrasound effects on fetal auditory brain stem responses.

The use of diagnostic ultrasound raises questions regarding its bioeffects upon fetal auditory function. This study was designed to determine whether ultrasound produces changes in the auditory brain stem response in fetal lambs. Near-term fetal lambs were chronically instrumented with electroencephalogram electrodes at the vertex and the right mastoid region. An earphone was secured in the fetal right external ear canal for auditory stimulation. An ATL mechanical sector scanner was used for all ultrasound studies at a spatial peak, temporal average intensity of 15.5 mW/cm2. Auditory brain stem responses were recorded at five and 15 minutes during pulsed-wave ultrasound exposure of the cranium and then 30 minutes after cessation of insonation. Sham experiments (without insonation) were then performed in a similar time sequence to rule out the effects of habituation. There was a consistent decrease in the mean amplitude and a consistent increase in the mean latency of all five wave deflections of the auditory brain stem response during insonation. These changes persisted for 30 minutes following cessation of insonation, after which auditory brain stem response amplitude and latency values returned toward control values. No changes in auditory brain stem response amplitude or latency were observed during sham experiments. We conclude that direct ultrasound exposure of the fetal cranium through the maternal abdominal wall may temporarily influence nerve conduction along central nervous system axonal pathways. This transient influence is reversible, with all values approaching baseline within 30 minutes.

Animals↗
PubMed1992

Electrical stimulation of motor cortex in experimental cortical ischaemia: pyramidal responses at C5 and the surface EMG.

In 7 baboons maintained under propofol anaesthesia, pyramidal tract responses were related to the corresponding peripheral EMG evoked by electrical stimulation of the motor cortex under conditions of focal cortical ischaemia. Pyramidal responses were recorded epidurally at the C5 level and the EMG was recorded from the contralateral hand or foot muscle using subdermal needle electrodes. Cortical ischaemia was produced by transorbital occlusion of the common anterior cerebral artery, and regional cortical blood flow was measured by the hydrogen clearance method. In the normally perfused brain, the later I waves of the C5 response required a lower stimulus strength to elicit them than the earlier I1 wave. It was more difficult to record the EMG from the hand than from the foot following stimulation of the corresponding cortex even though the C5 responses were always obtained in both cases. With moderate ischaemia, the later I waves were selectively abolished, leaving the D and I1 waves. EMG amplitude was significantly correlated with cortical blood flow (r = 0.88, P less than 0.005), and the threshold of cortical flow for the EMG was 10-13 ml/100 g/min. Our results indicate that changes in amplitude of the late I waves and particularly of the EMG are sensitive indicators of cortical ischaemia.

Animals↗
PubMed1981

Brainstem auditory and short-latency somatosensory evoked responses in brain death.

Thirty-five patients who met all clinical criteria for brain death and 53 patients who did not were tested with brainstem auditory (BAER) and short-latency somatosensory (SER) evoked responses. Of the brain-dead patients, 77% had no waves present in the BAER, including wave I, whereas 69% had medullary components present in the SER. These data suggest that the SER has greater clinical utility in the brain-death setting, because it is important to have a wave present that established that the input signal has reached the central nervous system. No brain-dead patients had subsequent waves in either test. These results are correlated with neuropathologic findings and contrasted with data obtained in the comatose but not brain-dead patients.

Adolescent↗
PubMed1999

[The neurobiology of slow-wave sleep].

In the two last years my lectures were addressed to the biological bases of wakefulness and REM sleep. The present lecture is focused on slow wave sleep, which corresponds to stages 3 and 4 in humans. These two sleep stages both present high voltage slow waves in the EEG that belong to the delta band (less than 3 Hz). Slow wave sleep usually lasts between 70 and 90 minutes in normal individuals, and takes place during the first hours of the night, as though our organism was making sure we got this essential sleep. Slow wave sleep is: a) the first sleep stage to recuperate after sleep deprivation, b) the stage with the most constant length even in individuals who have very different sleep habits, and c) the sleep stage that remains constant during experiments of gradual sleep reduction for eight-hour sleepers. This sleep stage is the one in which growth hormone is released and it essential for physical and intellectual efficiency and normal behavior in young adult individuals. Slow wave sleep is remarkably reduced in old people. What brain structures are responsible for the bioelectric and behavioral events of the slow waves sleep? Both the cerebral cortex and thalamus are indispensable for the existence of the slow waves EEG characteristic to this stage. Other brain structures participate in slow wave sleep organization; these include the basal forebrain, the oral pontine reticular nucleus, the deep cerebellar nuclei and the solitary tract nucleus. In this presentation I consider the most relevant functions of these structures as well as their anatomical connections, mainly with the neuronal networks responsible for other stages of the sleep-wakefulness cycle.

Adult↗
PubMed1999

Diurnal fluctuation of sleep propensity across the menstrual cycle.

Most women experience sleep changes across the menstrual cycle. We applied the ultra-short sleep-wake schedule to healthy females to compare their 24-h sleep propensity rhythms in the follicular and luteal phases. The daytime (09.00-16.30 h) subjective sleepiness and the number of slow wave sleep-containing nap trials increased in the luteal phase compared to the follicular phase, but the mean sleep propensity did not change. During the periods of 17.00-00.30 h and 01.00-08.30 h there were no differences between the two phases. These results suggest that increased daytime sleepiness in the luteal phase may be related to brain mechanisms controlling slow wave sleep.

Adult↗
PubMed1990

Brain-stem auditory-evoked responses elicited by maximum length sequences: effect of simultaneous masking noise.

The effects of masking noise on wave V of the brain-stem auditory-evoked response (BAER) obtained to pseudorandom pulse sequences are evaluated in two experiments. In the first experiment, the level of broadband noise was covaried with minimum pulse interval (rate) using maximum length sequence analysis (MLSA). Both increasing noise level and decreasing minimum pulse interval decrease wave V amplitude and increase wave V latency. A nonadditivity of rate and noise level was observed such that, at the shortest interpulse intervals, simultaneous background noise produced virtually no latency change and minimal amplitude change, for the noise levels tested. In a second experiment, high-pass masking was performed to assess the feasibility of derived-band techniques using maximum length sequence analysis (MLSA) and to compare the frequency regions responsible for the BAER using MLSA versus conventional averaging. Results of experiment 2 showed that reliable responses across high-pass masker cutoff frequency could be obtained in normal-hearing listeners. The frequency specificity of the MLSA-based responses was nearly identical to that obtained by conventional averaging, although both amplitude and latency of wave V were affected by the high-pass masker cutoff and minimum pulse interval values. These studies suggest that the neuronal populations and frequency regions responsible for the BAER are virtually the same for MLSA and conventional averaging.

Adult↗
PubMed2003

Brain-derived neurotrophic factor shows a protective effect and improves recovery of the ERG b-wave response in light-damage.

We investigated the neuroprotective effects of brain-derived neurotrophic factor (BDNF) and its influence on the functional recovery of the retina following light-induced retinal damage by electroretinogram (ERG). Rats were exposed to constant fluorescent light for 2, 5, 7, or 14 days, then returned to a cyclic light environment for 14 days. The result indicated that BDNF had few effects on the a-wave amplitude, but there was a statistically significant difference in the b-wave amplitudes between BDNF-treated and control eyes from day 0-14 of the recovery period following 2 days of light exposure (p < 0.05). Our findings suggest that BDNF not only protects the retinal neuronal function but also enhances the recovery from retinal light damage.

Animals↗
PubMed2006

Comparison of intracranial pressure measured simultaneously within the brain parenchyma and cerebral ventricles.

We report a 48-year-old man treated for acute subarachnoid hemorrhage (SAH) wherein intracranial pressure (ICP) was measured simultaneously within the ventricular cerebrospinal fluid (CSF) and the brain parenchyma (PAR). Single pressure waves within the continuous pressure signal were identified with determination of the single wave parameters pulse amplitude (i.e. pressure difference between diastolic minimum pressure and systolic maximum pressure), mean pressure (i.e. mean pressure from beginning to ending minimum diastolic minimum pressure), and latency (i.e. rise time from diastolic minimum pressure to systolic maximum pressure). A total of 218,589 CSF/PAR single pressure wave pairs were analyzed. For these CSF/PAR wave pairs the mean difference in pulse pressure amplitude was -0.13 mmHg [95% confidence interval (CI) -0.13 to -0.12 mmHg], mean difference in mean single wave pressure -0.71 mmHg (95% CI -0.74 to -0.68 mmHg), and mean difference in latency -0.01 seconds (95% CI -0.01 to -0.01 seconds). Hence, in this patient monitoring ICP within the ventricular CSF or brain parenchyma gave similar results. Moreover, the comparisons of single CSF/PAR wave pulse pressure amplitudes gave no evidence of a pressure gradient from brain parenchyma to the ventricular CSF in this patient.

Cerebral Ventricles↗
PubMed1988

EEG changes under hyperbaric conditions: spectral analysis during simulated diving.

Continuing investigations of the influences of the hyperbaric pressure upon EEG record in divers during simulated diving. The hyperbaric ecological system exerts influences on brain bioelectric activity manifesting itself by changes of alpha frequency and appearance of slow waves. The changes in the brain activity are mostly observable at the changes in chamber pressure values. The changes in EEG recordings are smallest at constant pressures. EEG examination can be used as a measure of the safety of newly developed decompression schedules.

Adult↗