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Biomedical subjects

D von Cramon

Publications and source records attributed to D von Cramon.

At least 19 recordsLinked to original sources
PubMed1979

Spontaneous activity of autonomic functions in coma due to drug overdose.

Spontaneous heart rate, respiration rate and electrodermal activity were studied in 32 patients with different grades of severe poisoning by ingestion of various drugs. The degree of their behavioural impairment was determined with the Munich Coma Scale (MCS) which measures stimulus evoked somatomotor responses. There was a significant reduction of spontaneous variations of heart rate and respiration rate with increasing severity of coma. Spontaneous electrodermal fluctuations were present only at the least severe grades of impairment. Thus, cardiorespiratory and electrodermal activity can provide significant information on the level of behavioural impairment in severe poisoning.

Adolescent↗
PubMed1979

Collicular function in human vision.

Threshold elevation in the periphery of the visual field as a consequence of repetitive stimulation can be abolished by stimulating a mirror-symmetric position in the contralateral visual half-field. A patient suffering from a congenital malformation of the right superior colliculus did not exhibit threshold elevation when stimulated repeatedly in the left visual field. Stimulation in the right visual half-field resulted in the usually observed threshold elevation, but stimulating a mirror-symmetric position in the left visual half-field did not abolish threshold elevation in the right half-field. These observations suggest that: (a) threshold elevation probably occurs as a consequence of collicular adaptation and (b) the mirror-symmetrically organized interhemispheric interaction is mediated at the collicular level.

Dominance, Cerebral↗
PubMed1979

Roving eye movements with bilateral symmetrical lesions of the thalamus.

Typical roving eye movements (pendular deviations of the bulbi) were observed in a 41-year-old patient with bilateral symmetrical softenings in the anterior thalamic region. They constantly appeared after lid closure with a mean latency of 7.3 sec. The mean frequency was 0.25 cps, the mean amplitude 30 degrees. The phenomenon of roving eye movement is discussed with regard to the supranuclear structures regulating binocular eye movements.

Adult↗
PubMed1979

Autonomic responses to meaningful and non-meaningful auditory stimuli in coma.

In a group of poisoned patients, the lowest MCS (Munich Coma Scale) vigilance grade at which patients responded when called by their names was determined. In 12 patients at this vigilance grade, the extent to which the meaning of the names contributed to their reactions was investigated. Their first name and a control stimulus (name backwards) were repeatedly presented via headphones. Stimulus intensity was 90 dB(A). During stimulus presentation, changes in heart rate, finger pulse amplitude, and electrodermal activity were recorded. A comparison between responses under both stimulus conditions revealed that the first reactions of poisoned patients to their names are primarily elicited by the physical properties of the stimulus.

Acoustic Stimulation↗
PubMed1979

The contribution of the 'second' visual system to directed visual attention in man.

The visual functions of a patient suffering from a brain lesion incorporating the left n. pulvinar was examined in order to assess the contribution of this structure to human vision. With the exception of the following abnormalities visual functions were normal. First, there was a decrease in the critical flicker frequency in the periphery (but not in the parafoveal region) of the right visual hemifield, that is, that contralateral to the pulvinar lesion. However, the second and most striking characteristic was--as shown by presenting visual stimuli bilaterally and simultaneously-a 'neglect' for the periphery of this contralateral visual half-field. This 'neglect' was a function of (a) position in the visual field (eccentricity), (b) stimulus properties (size and luminance), (c) temporal properties (length of presentation and interstimulus interval). In addition to this reduced capacity to detect stimuli appearing in the periphery of the right visual hemifield, there was also prolonged latency of visually evoked saccadic eye movements and a paucity of spontaneous eye movements directed towards the right visual hemifield. These results are interpreted in terms of a contribution of the n. pulvinar to the detection of light stimuli presented in the periphery of the visual field, and support the view that the tectopulvinar extrastriate visual pathway plays an important role in the control of visual attention.

Attention↗
PubMed1979

Restitution of visual function in patients with cerebral blindness.

Patients with postchiasmatic visual field defects were trained at the border of their visual field. Using a psychophysical method, light-difference thresholds were determined repeatedly in this visual field area. Improvement in contrast sensitivity and increase in size of the visual field could be obtained by this training procedure. The improvement was confined to the trained visual field area and showed interocular transfer indicating its central nature. Althoughh only contrast sensitivity was trained, the observed improvement was not limited to this visual function. Visual acutity, critical flicker fusion, and colour perception also showed and improvement suggesting an association of these functions. The improvement was restricted to the training period-no spontaneous recovery was observed between or after the periods of training. It is suggested that a lesion in the central visual system does not always result in a complete and permanent loss of function. The critical level of function that normally has to be reached for sufficient neuronal sensitivity may be obtained by systematic visual stimulation in the area between the intact and blind parts of the visual field. This increase in neuronal sensitivity leads to an improvement in visual performance.

Adult↗
PubMed1978

Consciousness and disturbances of consciousness.

The problem of consciousness is discussed briefly, including the contrary views of consciousness as a transcendental phenomenon and as an animistic fiction. Measurement of consciousness is possible only indirectly by means of quantitative assessment of accompanying behavioral deficits. Knowledge of the structural basis of consciousness is incomplete. The ascending reticular activating system (ARAS) is necessary for the maintenance of the state of consciousness. The monoamine and a great number of descending projections modulate the ARAS. The contents of consciousness depend also on telencephalic structures, primarily on the telencephalic cortex. Certain localized telencephalic lesions bring about disturbances of consciousness. The role of the corpus callosum in the problem of consciousness is discussed (one brain--two minds hypothesis). Then a classification of the various disturbances of consciousness is proposed. The term "disturbances of vigilance" is used for all disturbances of consciousness which are caused by a lesion in or a functional disorder of the ARAS or any of its modulating subsystems. The term "disturbances of the contents of consciousness" refers to disturbances of consciousness due to global or localized lesions or functional disorders of telencephalic structures. A list of characteristic features is given for each class of disturbances of consciousness.

Attention↗
PubMed1978

Association and dissociation of visual functions in a case of bilateral occipital lobe infarction.

A severe restriction of the visual field was observed in a patient suffering a bilateral occipital lobe infarction. Soon after the lesion, the visual field had an angle of approx. 4 degrees. Some recovery was observed within the following months. Within the restricted visual field, several visual functions were tested. Increment threshold, for instance, was found to be one log unit higher than would normally be expected. Color vision was completely lost soon after the lesion, but some recovery was later observed. Although binocular interaction was demonstrated by the interocular transfer of after-effects, the patient never experienced steropsis. He also seemed unable to recognize faces. Dsepite the small visual field, optokinetic nystagmus could be elicited. A notable slowing down of visual analyses was observed in experiments on visual reaction time, on the inversion of the Necker cube, and on binocular rivalry. The complete loss of certain functions like steropsis or face recognition in contrast to a quantitative reduction of other functions like visual acuity or color perception can be discussed in the light of two conceptual models of perceptual processing. One model suggests the representation of different visual functions within one neuronal network, each function represented by a different number of neurons or a different algorithm within the network. The second model suggests a spatial segregation of different visual functions in different cortical areas that receive input from one common structure, presumably the striate cortex.

Aged↗
PubMed1977

[The frequency of rapid eye movements and blinks as an activation indicator (author's transl)].

Electrooculographic (EOG) records were studied in 10 neurological patients with disturbances of activation according to clinical assessment and in 12 normal subjects. Rapid horizontal eye movements (saccades) and movements of the eyelids (blinks) were measured. It was concluded that the frequency distribution of blinks and saccades indicates activation deficits in a sensitive and reliable way. The continuous decrease of activation from orthological to pathological states could be shown by counting the frequencies of blinks and saccades. The relationship between the two variables is interpreted with regard to its functional significance.

Adolescent↗
PubMed1977

Diurnal variation of visual field size in patients with postretinal lesions.

Perimetry at various times of day in patients with large visual field defects due to postretinal lesions showed significant variations of visual field size. The largest visual fields were observed at noon, the smallest in the evening. Such systematic variations were observed only in patients who showed a gradual increase of increment threshold between the intact parts of the visual field and the scotoma. In two patients who showed an abrupt transition between intact and blind areas of the visual field, no obvious diurnal variation was observed. It is suggested that an endogenous modulation of neuronal sensitivity coupled to a hypothetical circadian oscillator is the basis of the diurnal variation.

Adolescent↗
PubMed1975

[Quantitative clinical assessment of the course in a case of temporal encephalitis (author's transl)].

The neuropsychiatric symptoms and signs of a case of sporadic encephalitis are presented. Psychopathological features are assessed with the IMPS (Lorr-scale). This is shown to be useful for objectivation and differentiation of the psychopathological syndrome. A disadvantage of the IMPS is the limited applicability in states with disturbed verbal communication and insufficient recording of mnestic impairment. Of the 4 states of activation defined for patterns of horizontal and vertical EOG and EMG recordings, state 2 (i.e., electrical activity of the mentalis-EMG, no blinks, no rapid lateral eye movements) and state 4 (i.e., rapid lateral eye movements, electrical activation of the mentalis-EMG) are appropriate measures for a quantitative description of the course of the disease. The relative distribution of state 2 and 4 within one period of registration indicates that the decrease of state 2 and the increase of state 4 are highly correlated with the reduction of psychopathological symptoms. Furthermore, transition among states shows the same correlation during the course of the disease. The ratio of the total number of transitions and non-transitions within one period of registration is proportional to the alleviation of clinical signs.

Adult↗