Hans-Otto Karnath

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Measures of brain activation (e.g., changes in scalp electrical potentials) have become the most popular method for inferring brain function. However, examining brain disruption (e.g., examining behavior after brain injury) can complement activation studies. Activation techniques identify regions involved with a task, whereas disruption techniques are able(More)
Recent technological advances, such as functional imaging techniques, allow neuroscientists to measure and localize brain activity in healthy individuals. These techniques avoid many of the limitations of the traditional method for inferring brain function, which relies on examining patients with brain lesions. This has fueled the zeitgeist that the(More)
Normally, we are aware of the current functions of our arms and legs. However, this self-evident status may change dramatically after brain damage. Some patients with "anosognosia" typically are convinced that their limbs function normally, although they have obvious motor defects after stroke. Such patients may experience their own paretic limbs as strange(More)
BACKGROUND Stroke patients may exhibit the peculiar behavior of actively pushing away from the nonhemiparetic side, leading to lateral postural imbalance and a tendency to fall toward the paralyzed side. This phenomenon has been called the "pusher syndrome." OBJECTIVE The current study analyzes the mechanism leading to contraversive pushing. METHODS The(More)
The dorsal stream of visual information processing connecting V1 to the parietal cortex is thought to provide a fast control of visually guided reaching. Important for this assumption was the observation that in both the monkey and the human, parietal lesions may provoke disturbance of visually goal-directed hand movements. In the human, severe misreaching(More)
Pantomime of tool use is a frequently used test for apraxia. For basic cognitive neuroscience, pantomime of tool use is of interest because it constitutes a link between instrumental and communicative manual actions. We used lesion subtraction analysis to determine the locations specifically associated with defective pantomime of tool use in patients with(More)
Lesion of the "vestibular cortex" in the human posterior insula leads to a tilted perception of visual vertical but not to tilted body posture and loss of lateral balance. However, some stroke patients show the reverse pattern. Although their processing of visual and vestibular inputs for orientation perception of the visual world is undisturbed, they push(More)
BACKGROUND AND PURPOSE Hemiparetic stroke patients with disturbed awareness for their motor weakness (anosognosia for hemiparesis/-plegia [AHP]) may exhibit further abnormal attitudes toward or perceptions of the affected limb(s). The present study investigated the clinical relationship and the anatomy of such abnormal attitudes and AHP. METHODS In a new(More)
The present study investigated the gaze as well as the head and the eye-in-head movements of neglect patients while they were exploring their surroundings. A random configuration of letters was presented on the inner surface of a sphere that surrounded the subject, requiring free exploratory eye and head movements. The subjects were requested to search for(More)
Various studies have documented that right hemispheric lesions restricted to the basal ganglia or to the thalamus may evoke spatial neglect. However, for methodological reasons, the exact anatomical correlate of spatial neglect within these two subcortical structures still remained uncertain. The present study identified these locations by comparing the(More)