Technetium-99m HM-PAO brain SPECT in epileptic patients before and during unilateral hemispheric anesthesia (Wada test): report of three cases.

The lipophilic brain SPECT agent [99mTc]hexamethyl propylene amine oxime (HM-PAO) was used in three cases before and during unilateral anesthesia of one hemisphere for lateralization of speech dominance (Wada test). This procedure led to a decrease of regional cerebral blood flow (rCBF) in each of the hemispheres to 55 and 90%, respectively. Diminution of rCBF was significantly more pronounced in the dominant hemisphere. A second phenomenon observed during the Wada test was crossed cerebellar diaschisis. These findings support the assumption that HM-PAO allows monitoring of brain perfusion, as rapid changes of rCBF due to decreased neuronal activity cause respective alterations of cerebral and cerebellar uptake of this new brain agent.

Severe negative emotional reactions in intracarotid sodium amytal procedures: further evidence for hemispheric asymmetries?

Intracarotid sodium amytal (ISA) procedures are commonly used to determine the lateralization of language and memory functions in presurgical evaluation of epileptic patients. Besides, they provide a means for studying putative hemispheric asymmetries in the organization of emotional behavior. In this study, we report the incidence of negative emotional reactions in eighty epileptic patients undergoing ISA procedures as a part of presurgical evaluation. There were only four such reactions in a total of 159 tests (2.5%), all in right-handed patients with left cerebral dominance for language functions. In one case, emotional outbursts occurred with barbiturization of the nondominant hemisphere. This observation invalidates the hypothesis that a loss of left-hemispheric functions generally leads to negative emotional reactions due to a right hemisphere specialization for the processing of negative emotions. Rather than pointing to fixed hemispheric asymmetries, our findings suggest that severe negative emotional reactions result from a flexible cognitive evaluation of the organism's overall situation.

[A case of apraxia and global aphasia without apraxia for axial body movement]. / Ein Fall von Apraxie und globaler Aphasie bei fehlender Apraxie für Bewegungen der Körperachse.

The case of a right handed 58 year old woman is presented who suffered an ischemic stroke after angiography following a vasospasm in the left internal carotid artery. The neuropsychological examination revealed global aphasia and severe apraxia for movements of the face and the extremities. However, the patient was able to carry out adequately axial movements to imitation and also to verbal command. These particular findings are discussed and explained within the context of the existing literature.

[Computer-assisted neuropsychological training in neurological rehabilitation]. / Computerunterstütztes Hirnleistungstraining in der neurologischen Rehabilitation.

Using computer-assisted cognitive training to treat patients with cognitive disorders has proved a useful tool in neurological rehabilitation. This has been shown by positive experience in many rehabilitation clinics but also in numerous control studies investigating the efficiency of such training. Patients with attention deficits show the most pronounced improvements as the computer with its technical possibilities is an ideal training instrument because of stimulus representation and reaction time measures. In other areas, computer training has become an essential therapeutic means complementing other therapies. In a clinical environment it seems that computer training is essential because it enables attaining the necessary therapeutic density. However, training must be integrated and become part of a global therapeutic framework.

[Are cognitive processes related to the EEG alpha phase? An experimental study using P300]. / Stehen kognitive Prozesse in Beziehung zur EEG-alpha-Phase? Eine experimentelle Studie zu 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.

[Does lateralized hemispheric control of cardiovascular activity exist? A Wada test study]. / Gibt es eine lateralisierte hemisphärische Kontrolle der kardiovaskulären Aktivität? Eine Wada-Test Studie.

The question of whether the influence of the cerebral hemispheres on cardiovascular activity exhibits left/right differences is important for the understanding of the psychophysiology of the autonomous nervous system. Experimental results have been contradictory. One experimental procedure used is the intracarotid amobarbital test (Wada test: short anesthesia of one cerebral hemisphere). Even with this test contradictory results have been obtained in various studies, although all involved relatively small of numbers of patients. Some authors have described increases in heart rate following anesthesia of the left hemisphere, while others found little or no effect at all. We therefore searched for evidence of lateralization in a larger number of patients (36) with complex partial seizures. These patients underwent the Wada test as part of the preoperative diagnostic evaluation. In this study, inactivation of the left or right hemisphere did not lead to significantly different effects on heart rate, or on systolic or diastolic blood pressure.

[Psychoanalysis and science-theoretical critique--new aspects of an old controversy]. / Psychoanalyse und wissenschaftstheoretische Kritik--Neues zu einem alten Streit.

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.

[Cognitive processes in unconscious patients? A brain mapping study of the P300 potential]. / Kognitive Prozesse bei Bewusstlosen? Eine Brain-Mapping-Studie zu P300.

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.

[Are cognitive processes in a phase relation with 40 Hz EEG?]. / Stehen kognitive Prozesse in Phasenbeziehung zum 40 Hz-EEG?

A coherent EEG-rhythm occurring in the 40 Hz range has been shown to correlate with cognitive processes of attention in a large number of studies. We intended to evaluate whether this frequency is of specific functional significance, and whether it may represent a rhythm of excitability for cognitive processes. The model of a rhythm of excitability assumes the 40 Hz-EEG to be a timer and organizer for information processing. Event-related potentials of 12 healthy normal subjects were recorded in an experiment of attention (auditory click stimulation). In order to evaluate whether the phases of the 40 Hz-EEG represent a rhythm of excitability, responses to stimuli having similar phases at the beginning of the stimulus were selected and averaged. An effect of the different 40 Hz-phases could not be demonstrated on the amplitude and latency of N100 and P200, components of the event-related potential associated with information processing. These findings suggest that a possible timer for cognitive processes of attention is not linked to the phases of the 40 Hz-surface-EEG.

The locked-in syndrome and the behaviorist epistemology of other minds.

In this paper, the problem of correct ascriptions of consciousness to patients in neurological intensive care medicine is explored as a special case of the general philosophical 'other minds problem'. It is argued that although clinical ascriptions of consciousness and coma are mostly based on behavioral evidence, a behaviorist epistemology of other minds is not likely to succeed. To illustrate this, the so-called 'total locked-in syndrome', in which preserved consciousness is combined with a total loss of motor abilities due to a lower ventral brain stem lesion, is presented as a touchstone for behaviorism. It is argued that this example of consciousness without behavioral expression does not disprove behaviorism specifically, but rather illustrates the need for a non-verificationist theory of other minds. It is further argued that a folk version of such a theory already underlies our factual ascriptions of consciousness in clinical contexts. Finally, a non-behaviorist theory of other minds for patients with total locked-in syndrome is outlined.

[The subject of death. On the current controversy about brain-oriented determination of death]. / Das Subjekt des Todes. Zur aktuellen Kontroverse um hirnorientierte Todesbestimmungen.

Recently new concepts of partial brain death have seriously challenged the well-established whole-brain definition of death. In the present paper, we propose a 4-level-model of death, which differentiates the levels of attribution, definition, criteria, and tests. It is argued that whole-brain concepts of death are susceptible to partial-brain oriented criticism, mainly because they do not provide a precise determination of the subject of death.

[Depth EEG and evoked potentials using an intravascular catheter electrode in the baboon]. / Tiefen-EEG und evozierte Potentiale mittels intravaskulärer Katheter-Elektrode beim Pavian.

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.

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.

[Preoperative diagnosis: the Wada test with SPECT control for localizing brain function in therapy-refractory epilepsy]. / Präoperative Diagnostik: Wada-Test mit SPECT-Kontrolle zur Hirnfunktionslokalisation bei therapieresistenter Epilepsie.

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.