This thesis describes a clinical study of disturbances of spatial perception.
Chapter I gives a short review of hemispheric asymmetry. For a long time
the right hemisphere was regarded as the minor hemisphere, of which
substantial regions were thought to have no specific function. Jackson,
however, believed that the posterior area of the right hemisphere played a
crucial role in subserving visual recognition and visual memory, but few of
his contemporaries agreed with him.
Later Rieger, Babinski and Dide also stressed the importance of the right
posterior region in spatial tasks. But is was not until more comprehensive
studies had been done in the 1950's (Hecaen and co-workers; McFie and coworkers)
that the right-hemisphere dominance for certain types of perception
was more generally accepted. The investigation of patients who underwent a
commissurotomy has contributed to our present knowledge of hemispheric
asymmetry (Sperry and co-workers).
Several types of spatial disorientation can be distinguished clinically: (a)
defective localization of stimuli in external space, (b) defective short-term
memory for spatial location, (c) defective route finding, (d) reading and
counting disabilities, (e) defective topographical memory, (f) visualconstructive
disabilities, and (g) simultaneous agnosia.
In older articles these disabilities were attributed to bilateral temporoparieto-
occipitallesions. But spatial disorientation has also been described in
patients with unilateral posterior lesions on either side and even in frontal
lobe disease. Later more comprehensive studies were done, because analysis
of single cases is susceptible to several sources of error. In many of these
studies it was concluded that the right posterior region plays an important
role in subserving visual and tactile localization (Hannay, Varney and
Benton; De Renzi). Yet, some authors only stressed the relevance of the
antero-posterior dimension but not the hemispheric asymmetry (Semmes et
a!.; Butters and Barton). The differences between these studies were probably
task-dependent. Most of the tests for assessing spatial abilities were derived
from intelligence tests or were designed to examine other well-known clinical
defects.