H. Hildebrandt et C. Schwendemann, Tonic and phasic alertness - One or two right hemispheric cortico-subcortical networks?, AKT NEUROL, 28(5), 2001, pp. 219-227
The functional role of the right hemisphere for sustained attention and vig
ilance is well-known. This investigation focusses on the localisation of di
fferent components of sustained attention. We analysed visual simple reacti
on time with and without acoustic warning for 63 patients with infarcts in
the right hemisphere and compared the results with a control group of 30 pa
tients with lesions in the cerebellum. Moreover we calculated a value which
indicated how much the patients profited by the warning tone. We argue tha
t this value is a good indicator for sustained attention. The involved brai
n areas were transferred into a standardized brain atlas blinded for the re
sults of the neuropsychological investigation. The neuropsychological resul
ts of the patients with right hemisphere brain damage, as a whole, were the
n compared with the control group. We compiled the mean reaction time for o
verlapping lesion areas and after sub-grouping the 63 right hemisphere pati
ents according to different infarct patterns, we tested the statistical dif
ferences between the lesion locations. As a result we found a general slowi
ng in right hemisphere patients. This was most pronounced for lesions invol
ving the right frontal and the posterior parietal areas. But only patients
with lesions involving the white matter of the corona radiata (including th
e corpus of the caudatum) and patients with lesions involving the insular c
ortex were impaired in sustained attention, as operationalized by our calcu
lation. The results of the patients with fronto-parietal lesions fit recent
PET studies which give evidence to the meaning of these areas for simple r
eaction tasks. On the other hand. there may be a second network responsible
for sustaining attention in the absence of external arousal signals.