DISCUSSION
Our data showed that partial resection of the gyrus
rectus resulted in selective impairment of memory for
objects, leaving memory for locations intact. One might
suppose that the object-location test was very easy and
not sensitive enough to catch any differences between
groups of tested subjects. However, subjects reached
the criterion on the average on the 4rd trial. Thus, it indicates
that performance in the object-location test was far
from ceiling effect.
As we have mentioned earlier, focal lesions to the
ventromedial prefrontal cortex are rarely investigated in
humans. Most human research concerns the effects of
relatively large lesions to this region. The only study we
are aware of showed that partial removal of the gyrus
rectus resulted in a worse short-term memory as measured
with the Benton visual retention test (Hûtter and
Gilsbach 1996). This finding is in agreement with the
present data and our previous study performed on the
same groups of patients that revealed that this area plays
a critical role in short-term storage of visual information
(Szatkowska et al. 2001).
There is another clinical study suggesting the involvement
of ventromedial prefrontal cortex in memory.
Bechara et al. (1998) found that patients with more
posteriorily placed bilateral lesions showed deficient performance
on an analogue of the delayed nonmatching-
-to-sample test, whereas patients with more anterior lesions
were not impaired. This studymay be relevant to our
research as posterior ventromedial lesionsmight imply the
involvement of the posterior part of the gyrus rectus.
However, more extended and more variable localizations
of lesions made it difficult to establish in what cases the
area of gyrus rectus was damaged.
It is worth noting that neuropsychological studies did
not search for the possibility that the ventromedial
prefrontal cortex plays a different role in object- and object-
location-memory. However, this issue was investigated
in monkeys. As noted in the introduction, studies
in monkeys indicated that ventromedial prefrontal le-