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Optical imaging of intrinsic signals is widely used for high-resolution brain mapping in various animal species. A new approach using continuous data acquisition and Fourier decomposition of the signal allows for much faster mapping, opening up the possibility of applying this method to new experimental questions.
To study the sensitivity of some central brain structures to the action of an electromagnetic field of decimeter waves (EMF of DW) a dynamic investigation of single unit activity was undertaken. Neurons of the hippocampus and hypothalamus with an excitatory type of response were found to have the greatest reactivity to EMF of DW. Neurons of the mesencephalic reticular formation and of the specific nuclei of the thalamus had mostly an inhibitory type of response. The number of neurons responding actively to EMF of DW and the number of inactive neurons varied depending on the energy density of the EMF.
Sensitivity of central cerebral structures to the action of the electromagnetic fields of decimetre waves (DMW) was studied with the aid of unit activity of comissural neurons. The greatest reactivity to DMW was found in neurons of hypothalamus and hippocampus. Neurons of the midbrain RF and of the specific thalamic nuclei displayed mainly an inhibitory response. The number of neurons responding to the DMW varied depending on the energetical density.
Locating the sources of brain magnetic fields is a basic question in magnetoencephalography (MEG). This question belongs to the indeterminate problem, that is, infinite solutions can be obtained from the equations of the measured small magnetic fields on the detector. Therefore a model of mathematics is needed to give more information. The major models of mathematics are the search method with many dipoles and the Lp minimum norm method. For the first model, if a global search is used, too much calculation time will be spent; if the gradient search is used, the searches usually converge to a local minimun. So other methods are introduced to find out the initial values, and then the gradient search can be used. For the second model, the depth of the brain sources will dependend on the choice of the weight functions which have several different types, and we do not know in advance which type is correct, so that it is difficult to have a good estimation of the depth of the brain sources. To overcome the difficulties, we use the method with three object functions which are the minimum Lp norm, the deviation between the calculated magnetic fields and the measured magnetic fields, and the number of the sources. This method is similar to the minimum norm method, a weight function is also introduced. But this weight function contains many reference variables which have to be determined through the minimization with three object functions. By choosing suitable weight function and its reference variables, the correct estimation of the depth of the brain sources can be achieved.
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The auditory brainstem electric response yields information on both the neurological and the audiological status of infants and adults. These early waves have particular properties as: non-habituation, absence of latency modifications between sleep, awake state, or under high doses of barbiturates. We have developed a procedure for extracting each type of information by measuring the latencies of wave I (auditory nerve) and wave V (inferior colliculus), then the speed of conduction between these two waves.
STUDY OBJECTIVES: Hypersynchronous delta activity (HSD) is usually described as several continuous high-voltage delta waves (> or = 150 microV) in the sleep electroencephalogram of somnambulistic patients. However, studies have yielded varied and contradictory results. The goal of the present study was to evaluate HSD over different electroencephalographic derivations during the non-rapid eye movement (NREM) sleep of somnambulistic patients and controls during normal sleep and following 38 hours of sleep deprivation, as well as prior to sleepwalking episodes. DESIGN: N/A. SETTING: Sleep disorders clinic. PATIENTS: Ten adult sleepwalkers and 10 sex- and age-matched control subjects were investigated polysomnographically during a baseline night and following 38 hours of sleep deprivation. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: During normal sleep, sleepwalkers had a significantly higher ratio of HSD over the time spent in stage 2, 3 and 4 on frontal and central derivations when compared with controls. Sleep deprivation resulted in a significant increase in the ratio of the time in HSD over the time in stage 4 on the frontal lead in both groups and on the central lead in controls. There was no evidence for a temporal accumulation of HSD prior to the episodes. CONCLUSIONS: HSD shows a clear frontocentral gradient across all subjects during both baseline and recovery sleep and has relatively low specificity for the diagnosis of NREM parasomnias. Increases in HSD after sleep deprivation may reflect an enhancement of the homeostatic process underlying sleep regulation.
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In this experiment, the paradigm of CNV is changed, with two warning stimuli presented and the key press for discrimination exchanged in order to reject the motor factor in CNV. The main results are: Second level of CNV is increased, an extrication wave is discovered. Various hypotheses about CNV are discussed, proposing that the psychological factor in CNV is not a unitary one, but the increase of the mental load which is synthetically composed of many psychological factors.
From 1980 to 1989, during intracranial pressure (ICP) recording, brain herniation (central transtentorial herniation associated with uncal herniation) developed in 15 patients as a result of aneurysmal rebleeding, uncontrollable brain swelling and/or oedema in spite of attempts at treating increased ICP. The relationship between the ICP level at which herniation occurred and the ICP fluctuation patterns in continuous ICP recordings prior to the development of the herniation was studied retrospectively. As for the ICP fluctuation patterns, the patients were assigned to 2 groups on the basis of the presence or abscence of plateau waves of Lundberg: group I comprising 8 patients without plateau waves but with a high ICP, and group II comprising 7 patients with both plateau waves and a high ICP. In the group I patients the herniation occurred as a result of aneurysmal rebleeding or brain swelling after subarachnoid haemorrhage, and in the group II patients the herniation resulted from brain tumour, meningitis carcinomatosa and superior sagittal sinus thrombosis. In the group I patients the herniation developed at a mean ICP level of 70-98 mmHg, and in the group II patients it occurred at a mean ICP level of 120-150 mmHg, far higher than the ICP level causing herniation in the group I patients. It has been shown that patients with a plateau-wave phenomenon in continuous ICP recordings have a marked impairment of cerebrospinal fluid (CSF) absorption and a delayed CSF flow.(ABSTRACT TRUNCATED AT 250 WORDS)
During slow-wave sleep, rat brain glycogen increases within a few minutes to about 70% above waking levels. Upon awakening, the increment is lost within 2-5 min. After repeated episodes of sleep, brain glycogen levels are comparable to those observed after only a single episode of sleep. Liver glycogen is unaffected by slow-wave sleep.
The value of the Auditory Brain Stem Response (ABR) in the assessment and detection of neurological disorders could be considerably enhanced if the normative standards of ABR characteristic parameters take into account all other systematic sources of variance. The present study attempts to take into account the influence of head size on latency and amplitude of the ABR components. We examined amplitude and latency as a function of head size in 40 normal male subjects (age 20-40 years). Significant negative correlation was found between amplitude and head radius. The experimental data were fitted using a theoretical curve of the potential on the surface of a three-concentric sphere model representing the human head. The fitted curve of amplitude versus radius can be applied to normative data in order to substantially reduce dispersion and consequently increase the diagnostic value of this parameter. Moreover, a substantial effect of radius on wave V latency was detected. Normalization of the latencies with reference to the head radius, assuming that the latter is proportional to the length of brain stem, resulted in a significant reduction in the standard deviation of these data as compared to the original.
The contribution of ipsilateral and contralateral auditory brain-stem structures to the generation of wave V of brain-stem auditory evoked potentials is a controversial subject. We describe two cases with an intrinsic brain-stem lesion that involved the lateral lemniscus unilaterally in the middle and upper pons. The focal nature of the auditory structures was confirmed by detailed neuropathologic data in one case and by magnetic resonance scans in the other one. In both cases, brain-stem auditory evoked potentials revealed the unilateral absence (case 1) or marked attenuation (case 2) of wave V on stimulation of the ear contralateral to the intrinsic pontine lesion. Findings in both cases strongly suggest that wave V is predominantly generated by pontine structures contralateral to the stimulated ear and that the integrity of the contralateral lateral lemniscus is essential.
With different task load levels and input modality formats, P3 wave of event related brain potential (ER-P) were recorded and analyzed in eighteen healthy young man performing six dual tasks. The dual task was made up of visual tracking primary task (T) and Sternberg additional task (S) or Oddball additional task (O) (TS and TO). Its difficulty was controlled by changing the velocity and dimension of movement of target in primary task. The results showed that P3 latency (LAT) prolonged when the primary task was more difficult and its changes of amplitude(AMP) depended on the input modality formats of primary task and additional task. AMP of TO dual task with different formats decreased when the primary task was more difficult and that of TS with same formats increased. It suggests that task load level and input modality format may influent P3 wave of event related brain potential.
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Systemic injections of cholecystokinin octapeptide sulfate ester (CCK-8-SE) elicit various behavioral and autonomic responses, such as increases in nonrapid-eye-movement sleep (NREMS) and hypothermia. There are two CCK receptors; both CCK-A and CCK-B receptors are stimulated by CCK-8-SE. The relative importance of the CCK-A and CCK-B receptors in the somnogenic and hypothermic effects of CCK-8-SE is not well understood. In the present experiments, we studied the effects of the selective activation of CCK-B receptors by CCK tetrapeptide (CCK-4) or nonsulfated CCK-8 (CCK-8-NS) on sleep and brain temperature (Tbr). Rats were injected intraperitoneally with saline on the control day and with CCK-8-NS (10, 50, or 250 microg/kg) or CCK-4 (10, 50, or 250 microg/kg) on the test day 5-10 min before dark onset. Electroencephalogram, electromyogram, and Tbr were recorded for 12 h. None of the treatments affected sleep or Tbr significantly, with the exception of 10 microg/kg CCK-4, which transiently decreased the amount of NREMS, and 10 microg/kg CCK-8-NS, which slightly increased REMS. These results suggest that the activation of CCK-B receptors by systemic injection of CCK-4 or CCK-8-NS is not sufficient to elicit increased NREMS and hypothermia in rats.
The purpose of this study was to compare the sensitivity of the ABR wave V latency-intensity (L-I) function to that of Alternate Binaural Loudness Balance, Loudness Discomfort Level, and Acoustic Reflex Threshold tests in identifying sensory hearing losses. Five audiometric groups were tested by each procedure. The groups included subjects with normal hearing, and with conductive, high-frequency sensory, flat sensory, and retrocochlear hearing losses. The ability of each test to separate sensory from retrocochlear impairments was investigated. A positive discriminator for cochlear impairments was of particular interest. A combination of wave V L-I slope at lower intensities and the dB HL value that separates steep and shallow slopes of the L-I function appears to meet this objective.
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