TY  - THES
AB  - Hemineglect is a disturbance that can occur after lesions of one hemisphere of the brain, in most cases the right one. The affected people neglect visual, tactile or acoustic stimuli in the half-space opposite to the brain lesion. This behavior cannot be explained as a consequence of a disturbed processing of sensory information, neglect is rather a disturbance of its own.
Vallar, Guariglia, Nico, and Bisiach (1995) investigated, how patients with spatial hemineglect would perform on an auditory localization task. The subject's task was to indicate the direction of a sound; in one condition it came from the front and in another condition from the back. The subjective location of the mid-sagittal plane was calculated by this data. Compared to right brain-damaged patients without neglect and a group of healthy controls, the mid-sagittal plane of right brain-damaged patients with hemineglect was displaced rightwards in the front and the back half-space. Vallar and colleagues (1995) interpreted this in favor of a translation of an egocentric coordinate system, rather than a rotation around the vertical axis of the body.
Inspired by the work of Vallar et al. (1995), the following study investigated hemineglect in the tactile modality. Just like the auditory, the tactile sense allows questions regarding the back half-space. Can a deviation to the right of the subjective mid-sagittal plane in front space, which was found in the visual and auditory modality, be confirmed in the tactile modality as well? Does the subjective mid-sagittal plane in back space also show a deviation from the objective position? Would the deviation go to the right or to the left, to support translation or rotation of the egocentric frame of reference? These questions should be addressed in the following study.
8 right brain-damaged patients with neglect, 8 right brain-damaged patients without neglect and 11 nearly age matched healthy controls served as subjects in this study. All of them wore a belt containing 15 electrodes. Only one electrode at a time caused a prickling sensation, at first in the front, later in the back half-space. A specially constructed keyboard in the shape of a half-circle with 15 keys, served for the subjects as a means to enter their response regarding the spatial position of the stimuli. From this data the point of subjective equality (PSE) was calculated by multiple regression. The PSE is the point, where the probability for the subjects to classify a stimulus as right or left is equally high.
In the front space the mean PSE in the group of neglect patients deviated -12 degrees to the left and was significantly different from the mean PSE of the healthy control group. In back space, the mean PSE of all groups deviated with -3 degrees slightly to the left, but was not different between the groups.
The results were discussed in terms of external factors like the design of the study, the selection of the subjects and the equipment. Furthermore, aspects like perception, localization, visualization as well as planning and execution of the response were considered as factors that potentially could have influenced the results. In addition, the PSE as a method to calculate the mid-sagittal plane was discussed. It is considered possible that a deviation of the reacting movements of the neglect patients to the right has influenced the results. An additional thought is that pointing to targets in space as well as the visual search for them are active processes, whereas the perception of acoustic and visual stimuli are passive processes, and both dimensions could possibly dissociate within one patient.
This study neither provides evidence for a translation nor for a rotation of the egocentric frame of reference in the tactile modality. This result is contradictory to the majority of the publications, which have dealt with the estimation of the front mid-sagittal plane in by neglect patients and had favored its deviation to the right.
DA  - 2006
KW  - Neglect , Tastsinn , Neuropsychologie , Hirnschädigung , Hemineglect , Taktil , Rotation , Translation , Brain damage , Sense of touch , Neglect
LA  - ger
PY  - 2006
TI  - Neglect in der taktil-sensiblen Modalität : Untersuchung mit elektrischer Stimulation am Rumpf
UR  - https://nbn-resolving.org/urn:nbn:de:hbz:361-10410
Y2  - 2024-11-21T21:27:18
ER  -