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Biomedical subjects

W Haschke

Publications and source records attributed to W Haschke.

At least 19 recordsLinked to original sources
PubMed1998

Postnatal conditioning for spreading cortical depression in the rat brain.

The cerebral cortex of anaesthetised 2- to 12-day-old rats was superfused with artificial cerebrospinal fluid containing 100 mM acetate substituted for chloride to condition the brain for spreading depression (SD). After such superfusion, the earliest SD-like events were found at day 9 and full blown SD at day 10, whereas in the unconditioned brain the first SD occurred between days 12 and 15. Acetate conditioning of the cerebral cortex may be used to unmask neuronal and glial properties that are hidden in early stages of development.

Acetates↗
PubMed1996

Initiation of spreading depression can be blocked by transcortical polarization of rat cerebral cortex.

Spreading depression (SD) was elicited in urethane anesthetized rats by pricking the cortical gray matter with a needle. The SDs were monitored by recording changes of direct current (DC) potentials and changes of extracellular potassium concentrations ([K+]e). Simultaneous recordings were made at cortical depths of 400 microns and 1200 microns by an array of two double-barrelled electrodes, one served to measure DC the other contained an ion-sensitive resin. An additional DC microelectrode was inserted in the gray matter near the point of SD elicitation at a depth of about 400 microns. An epicortical Ag-AgCl wire electrode surrounding the recording site and a remote Ag-AgCl electrode penetrating the cortex in the contralateral hemisphere were used for polarizing DC currents. These currents were applied 5 min before elicitation of SD by a needle prick and were sustained for a period ending 3 min after SD. Cathodic polarization of cortical surface with intensities of 30 microA and higher blocked the SD completely. Lower intensities of polarizing currents (10 or 20 microA) had no effect. After ending polarizations normal SDs could be elicited. The polarizing and restitution effects were replicable in the same animal. The results suggest that longer lasting DC polarization of the cortex blocks initiation of SD but not propagation.

Animals↗
PubMed1994

Stimulus preceding slow potential shifts (SPS), EEG and visual evoked potentials (VEP) in rabbits.

In experiments of a modified "amplitude trigger" design on rabbits with chronically implanted cortical electrodes we looked for correlations between the partial activation state and EEG, DC-shifts and amplitudes of visual evoked potentials. The activation states are characterized by power spectra of EEG frequencies, actual heart and respiration rates and were in strong correlation with N1 amplitude of VEP as well as polarity and amplitude of stimulus preceding slow potential shifts. Three different activation states could be separated: low vs. "optimum" vs. high activation state. The "optimum" activation state is characterized by large amplitude VEP, positive directed stimulus preceding slow potential shifts as well as a desynchronized preflash EEG.

Animals↗
PubMed1994

Transcortical polarization in rat inhibits spreading depression.

In cerebral cortex of rats single spreading depressions (SD) were elicited by a slight needle prick. SDs were monitored by recording changes of direct current (DC) potential via an array of four glass microelectrodes providing a simultaneous depth profile. Using an epicortical Ag-AgCl wire electrode surrounding the recording site and a contralateral Ag-AgCl electrode penetrating the whole grey matter, a polarization current was applied starting 5 min before and ending 3 min after eliciting a SD. By anodic polarization of the cortical surface with intensities of 10 to 20 microA the SD was blocked in the whole grey matter. Restitution of SD in course and amplitudes was found only 45 min to 60 min after ending the polarization. Cathodic polarization of the cortical surface resulted in similar effects. Both polarizing and restitution effects were replicable in the same animal. The results are relevant for further investigations to discover the particular role of glial cells in regulation of extracellular potassium concentration during SD.

Animals↗
PubMed1993

Medial septal area modulation of sustained negative shifts in awake rabbits.

Experiments were performed on rabbits with chronically implanted Ag-AgCl electrodes over occipital cortex and chrome-nickel stimulation electrodes in the medial septal area. Visual evoked potentials (VEP) were elicited by means of randomly occurring flashes. After measuring the N1-amplitude of the VEPs, responses with N1-1 amplitudes below a previously determined discriminative value were reinforced by a weak footshock 1.5 S1 after the flash. In the group of high-amplitude VEP we found longer negative shifts than in the group of low-amplitude VEP, starting 600-700 ms after flash and lasting up to the end of the observed time range. The stimulation of medial septal area (0.5 mA, 6 imp/s) during the normal flash application led to a delay of the maximum of this negative shift which returned now to baseline within the observed range. The amplitude of these sustained negative shifts was larger during septal stimulation. Larger negative shifts followed high-amplitude VEP than the low-amplitude ones. Repetition of usual flash application without septal stimulation after a 10 min break turned the negative shift to normal. After electrolytic destruction of medial septal area this late negative shift vanished without any restitution.

Acetylcholine↗
PubMed1992

Activation state of the cortex could be changed by reinforcement of low-amplitude visual evoked potentials in rabbits.

Visually evoked potentials (VEP) were recorded chronically from occipital cortex in awake rabbits. The VEP typically consisted of a triphasic response (positive deflection P60--negative deflection N205--positive deflection P450) that was followed by a late negative shift starting about 750 ms after the eliciting flash. After computation of a discriminating amplitude value (200 or 250 microV) the VEP were divided for comparison in high- and low-amplitude groups. Significant differences between these groups existed in amplitudes and latencies of the early VEP components. High-amplitude VEP were followed by larger late negative shifts and had significantly (P less than 0.01) earlier second positive deflections. In these high-amplitude cases, the EEG-baseline was more negative than in the low-amplitude VEP. In addition, we found a more synchronized background EEG in the low-amplitude VEP group. We conclude that different VEP amplitudes depended on different activation states of the cortex which could be changed by reinforcement.

Animals↗
PubMed1992

Differences in mental task performance and slow potential shifts in subjects differing in cortisol level.

Hormones of the pituitary-adrenocortical axis (e.g., cortisol) are involved in the regulation of brain function. This study was aimed to clarify whether individual differences in baselines of cortisol are related to differences in heart rate (HR), slow brain potential shifts (SPS), performance data and personality. 17 males were instructed to solve 120 arithmetical tasks under time stress conditions. They could obtain monetary bonuses according to the accuracy of their task performance. This test condition was compared to a control condition. To determine the plasma level of cortisol by radioimmunoassays four blood samples were collected during the session. Baselines were estimated twice. A clustering procedure with respect to all cortisol levels resulted in a group of high responders (HC, n = 9) and a group of low responders (LC, n = 8). The HR was significantly higher in the HC group. The SPS of the LC group were characterized by a larger P300 elicited by the task followed by a steep negative slow wave (NSW) as compared to the HC group. LC subjects also showed a higher NSW before feedback presentation. The LC group solved the tasks faster and obtained more than twice the reward than the other group. They scored higher in achievement motivation and also reported increased 'Social Acceptance' and decreased 'Tiredness'. In sum, the results suggest a more efficient regulation of the arousal level of the LC group in contrast to the HC group as far as reflected in the parameters analysed.

Adolescent↗
PubMed1991

Activation-induced changes in evoked and slow brain potentials: effect of cocaine in rabbits previously subchronically treated by cocaine.

To study the type of adaptive modification (tolerance vs. sensitization) in different organism's indices following intermittent cocaine (COC) administrations, acute COC (2 mg/kg, SC)-induced changes in heart and breathing rate, response to increasing noxious stimulation, spontaneous EEG and event-related evoked and slow brain potentials (ERP) registered from the occipital cortex and hippocampal CA1 region were investigated in naive rabbits and one subchronically treated with COC (6 injections at a same dose). Tolerance developed for bradycardia, depression of noxious responsiveness, cortical desynchronization and increase of main components of cortical ERP, typical to acute COC, while the changes in breathing and hippocampal ERP were stable. These changes as well as a significant increase due to COC administrations of the basal values of an animal's noxious responsiveness and increase in relative changes in main component of cortical ERP (N205) are considered as a consequence of adaptive changes in neurophysiological/neurochemical substrate accepting COC action and mediating phenomena tolerance-sensitization and dependence typical to the drug.

Adaptation, Physiological↗
PubMed1990

An easy method to record slow potential shifts (SPS) in rabbits using the "oddball" paradigm.

Rabbits with chronically implanted Ag-AgCl electrodes over somatosensory and visual cortex were trained to a modified 'oddball' paradigm with visual stimulation. Event related potentials (ERP) and slow potential shifts (SPS) were recorded. By means of a computer controlled stimulator 'frequent' and 'rare' LED flashes were administered to the eyes of the rabbit. If 'rare' stimuli were reinforced by a weak electrical footshock, negative SPS rose steeper and reached significantly higher amplitudes than in 'frequent' conditions without reinforcement. Different kinds of the follow-up of 'frequent' and 'rare' series were tested. Best effects were obtained, if a session was divided into 3 blocks (3 srs. 'frequent'--5 srs. 'rare' reinforced--2 srs. 'frequent' and probability of 'rare' flashes was 20%. Our present data formed a basis for investigations on the neuronal and glial sources of SPS in rabbits.

Animals↗
PubMed1989

[Possibilities of objective assessment of the course of activation in ideomotor training].

An active exploration of movement tasks is accompanied with central nervous activation. Its systematical examination needs a teamwork of scientists of various branches of knowledge (i.e. physiology, psychology, sport sciences). Mental training (motor imagination - MI) was chosen as a model for such examinations. In connection with the execution of MI there are characteristic chances of the mean alpha frequency of the EEG, heart rate, respiration rate and skin conductance. The time course of these parameters depends on the number, the duration and the sequence of MI. A graduated submaximal load on ergometer has no influence on the course of the examined parameters. Our investigation allows the conclusion that different activation processes go on within different subsystems during the execution of MI. From a physiological point of view it seems to be necessary that a concrete paradigm of MI must be examined concerning the course of the parameters and, thus, to guarantee the effort of MI.

Adolescent↗
PubMed1987

ERP analysis of reafferent information processing during the performance of an arithmetical task.

Reafferent information processing accomplished by distributed cerebral systems was studied by analysing concomitant event-related potentials (ERPs) elicited by weak electrical stimulation of the skin of the hand. The subjects were instructed to interpret this stimulus as feedback information indicating whether their solution of an arithmetical task was correct or not. ERPs elicited by positive or negative feedback signals showed striking differences. ERPs were also influenced by the subject's confidence in the correctness of the solution, while probability of stimulus occurrence was less important in the design. Neurophysiological implications of ERP-disclosed influences on feedback processing are discussed.

Adult↗
PubMed1980

[Modification of light-evoked potentials depending on the feeding behavior of rabbits. II. Dependence on biological significance of the stimulus].

The dependence on biological significance of the stimulus of averaged evoked potentials (AEP) to flash from visual and sensomotory cortex and from the dorsal hippocampus were studied in alert rabbits in the example of a conditioned reflex (BR) with food reinforcement. The AEP to conditioned flash from visual cortex showed a surface positivation at the end of the early section (67-76 ms) and at the beginning of the late section of the potential (100 to 180 ms) in comparison with AEP to "indifferent" stimuli in a pseudoconditioning (PC). Typical for the visual and sensomotory cortex of trained hungry, but not satiated animals was the occurrence of a positive component (Sp130) with mean peak latency of 130 ms. The shortest EMG-onset corresponded with the beginning of the positivation or the Sp130-component. Records of the CA1-field of the dorsal hippocampus showed changes already 40 to 60 ms after the flash. Possible conclusions about the functional meaning of EP-changes, depending on the biological significance of the signal, are discussed.

Animals↗
PubMed1975

[A simple method for the evaluation of differences in averaged evoked potentials as demonstrated of visual evoked potentials changed through hippocampal stimulation].

A simple method is presented which by subtraction of amplitudes of averaged evoked potentials (AEP) within regular time-intervals enables us to estimate differences in the course of the potential. First results demonstrate that all parts of the potential may be influenced and that most striking differences must not necessarily occur in the peak region of the AEP. The late negative complex of the AEP is likely to be a result of summation of some subcomponents, which may be altered differently. The method presented allows exact measurements of each of them.

Animals↗