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D B Linke

Publications and source records attributed to D B Linke.

31 records · Page 2Linked to original sources
PubMed1990

Activation of the epileptic focus during intracarotid amobarbital test. Electrocorticographic registration via subdural electrodes.

During presurgical evaluation, bilateral intracarotid amobarbital tests were performed in 21 patients (42 tests) to establish the lateralization of cerebral speech dominance as well as memory function. All patients suffered from long-standing, medically intractable, complex partial seizures. Electrocorticographic recording during the investigation was carried out via bilaterally implanted subdural electrodes. The aim of the study was to assess amobarbital-induced effects on the primary epileptic focus, determined throughout presurgical evaluation. Following the application of amobarbital the primary epileptic focus was selectively activated in 10 and preferentially activated in 3 patients suffering from temporal lobe epilepsy. Specific responses of the primary epileptic focus consisted of: (i) induction of a spike-burst-suppression pattern, mainly in the mesio-basal aspects of the focal temporal lobe (n = 13); (ii) induction of spikes or sharp waves following contralateral intracarotid injection (n = 10); (iii) late induction of spikes or sharp waves following ipsilateral injection (n = 4); (iv) loss or marked reduction of drug-induced beta activity over the primary epileptic focus (n = 14) following ipsilateral or contralateral injection. In conclusion, electrocorticographic recording during the intracarotid amobarbital test contributes valuable information about the primary epileptic focus in a high proportion of patients.

Action Potentials↗
PubMed1990

Crossed cerebellar diaschisis in intracarotid sodium amytal procedures: a SPECT study.

Eight patients with drug-resistant complex-partial seizures were subjected to left- and right-sided intracarotid sodium amytal (ISA) procedures during preoperative investigations for surgical treatment. Regional changes of cerebral and cerebellar blood flow during barbiturization were measured by [99mTc]-HMPAO-SPECT. Crossed cerebellar diaschisis (CCD) was observed in 13 out of 16 tests (81%) as well as ipsilateral cerebral hypoperfusion (87%). Thus CCD occurred more frequently in ISA procedures than in previously studied patients with cerebral infarctions and tumors. Since intracarotid injections of sodium amytal lead to hypoperfusion mainly in those areas of the brain that are supplied by the middle cerebral artery, functional suppression of these regions is supposed to be one of the main preconditions of CCD. Our findings suggest that CCD as demonstrated by the SPECT-technique is a common phenomenon in ISA procedures.

Adolescent↗
PubMed1989

[Depth EEG and evoked potentials using an intravascular catheter electrode in the baboon].

Obtaining an intracranial EEG, as well as a depth recording of the somatosensory evoked potentials, via a vascular approach are described. Experimentally, a directable microcatheter was placed in the middle cerebral artery of baboons. Using the catheter guide wire as electrode, intracranial electrical activity was recorded from within the cerebral vessels. Significantly, depth recordings of the SEP showed waves of thalamic origin not present in surface recordings. Advantages of this method over surface recordings are the greater gain of information possible and, over other techniques of depth recording, the comparibly lesser invasiveness.

Animals↗
PubMed1989

[Cognitive processes in unconscious patients? A brain mapping study of the P300 potential].

P300 is the most investigated component of the event-related potentials. Being the correlate of an active target discrimination and decision making process it is seen as related to cognition. Such elementary cognitive processes--as expressed in P300--can happen even in states of coma. In four of 35 comatose patients with diffuse head injury we were able to measure the P3-wave showing frontal and parietal components. Accordingly some unawakable patients can still recognize differences in pitch. The structure of components and their psychophysiological meaning are discussed.

Adult↗
PubMed1988

[Temporary mirror writing and mirror reading as disinhibition phenomena? A case study].

After removal of a left parietal meningioma a 74-year-old right-handed woman developed temporary mirror writing and mirror reading. Further analysis of the mirror phenomena came from tachistoscopic hemifield stimulation showing a right hemisphere superiority for the recognition of words presented in mirror fashion. These neuropsychological results are discussed in the context of common concepts. Finally the hypothesis of bihemispheral mirror-image engrams according to Orton will be suggested as a comprehensive explanation and supported by evidence from the literature.

Aged↗
PubMed1988

[Preoperative diagnosis: the Wada test with SPECT control for localizing brain function in therapy-refractory epilepsy].

Extensive diagnostic measures are necessary to clarify the indication for surgery in patients suffering from epilepsy that is refractory to treatment. Within the overall framework of neuropsychological diagnosis we conducted the Wada test, injecting 200 mg (or 3 mg/kg body weight) of sodium amytal on different days, in each case into the left or right internal carotid artery. This results in a 3-5 minute anaesthesia of the relevant hemisphere. By means of a neuropsychological short test it is possible to determine the performance of the non-blocked hemisphere. The extent of the blocking is also determined by simultaneous i.v. injection of HM-PAO (hexamethyl propylene amine oxime) labelled with 99m Tc, the uptake of which by various cerebral regions is visualised via SPECT. The Wada test supplies information on the lateralisation of cognitive functions (speech, memory etc.) whereas the SPECT examination enables additional determinations not only of processes that must be characterised as diaschisis, but also on the extent of blocking of a hemisphere. The results supply clues to expected postoperative cognitive deficits and thus enable a differentiated assessment of the indication for surgery. This is discussed on the basis of two clinical cases.

Adult↗
PubMed1987

[Are cognitive processes related to the EEG alpha phase? An experimental study using P300].

Different models have been developed in the past to explain the functional significance of the EEG alpha rhythm. This rhythm has been viewed as an expression of a scanning mechanism, of an inner clock or of an excitability cycle. Based on these conceptions, several older works dealing with EEG alpha phase and reaction time suggest that the EEG may also serve as a gating mechanism for cognitive information processing. The purpose of this investigation was therefore to determine the existence of a possible correlation between P300 and the background EEG. P300 was used as a neuroelectrical correlate of a cognitive decision-making process. However no significant relationship between P300 latency period and EEG alpha phase was found. The variability of P300 can therefore not be explained in this way.

Alpha Rhythm↗
PubMedDate not supplied

[Psychoanalysis and science-theoretical critique--new aspects of an old controversy].

Up to now, relations between psychoanalysis and philosophy of science have mainly been confined to controversies about the scientific status of psychoanalysis. Freud himself had tried to reject classifications of psychoanalysis as a non- or pseudoscience by maintaining a sort of foundationist empiricism, which is philosophically problematic in several respects. The discussion of one classical (Popper) and one recent (Grünbaum) critique of psychoanalysis shows that the arguments are still broadly determined by Freuds own philosophical prejudice. It is then argued that a coherentist philosophy of science would allow a more adequate discussion of the problem of the scientific status of psychoanalysis than did classical foundationism.

Freudian Theory↗