Patient AMA suffered a head trauma that left her with several visual compla
ints, including a reading disability. AMA appears to suffer from 'simultana
gnosia, as established with tasks such as naming briefly presented multiple
stimuli or overlapping figures, describing the theme of complex scenes, an
d counting arrays of stimuli. Specifically, AMA has difficulty perceiving i
mmediately successive stimuli and, in particular, multiple stimuli that app
ear at novel or unexpected locations. Her ability to encode spatial relatio
ns rapidly (of either the categorical and coordinate type) is markedly redu
ced. However, when a familiar target appears among multiple stimuli at expe
cted (previously encoded) locations, AMA's performance can be within normal
limits. These results suggest that this patient's simultanagnosia cannot b
e reduced to an inability to process multiple stimuli per se. Rather it is
better characterised as (1) an inability to index new locations of multiple
stimuli, and (2) a reduced efficiency in pattern analysis. The former defi
cit, in turn, may lead to difficulty in focusing on objects efficiently and
using objects as landmarks or reference points. Damage to one or both of t
he above mechanisms could produce simultanagnosia and reading difficulty.