We studied the properties of palinopsia due to a known cerebral
lesion, in which positive afterimages were confined to a region in
the lower left quadrant. The results of Experiments 1–3 show that
the negative afterimages in CQ's affected quadrant were no different
from those in his unaffected quadrant. The experience of an
immediate-type palinopsia is therefore not necessarily accompanied
by distortion of normal adaptive phenomena, in particular when the
palinoptic images are positive rather than negative afterimages. The
aim of Experiment 4–7 was to provide objective measures of CQ's
positive palinoptic afterimages, concerning their intensity, duration
and location. The results show that the palinoptic afterimage could
be evoked by an adaptor of relatively low intensity (1.0 cd/m 2). CQ
was able to match the intensity of his positive afterimage with a
real physical stimulus, showing that his palinoptic afterimage was about 10% of the brightness of the stimulus inducing it. This contrasts
with the negative afterimages in his affected and unaffected quad-
rants, which were almost as strong as the stimuli inducing these. Importantly, his positive palinoptic afterimages lasted for over two
minutes, 7 to 10 times as long as his negative afterimages, and were
systematically displaced from the inducing location, in distinct con-
trast to the highly retinotopic nature of normal negative afterimages.