ABSTRACT
IMPLICIT PROCESSING OF GLOBAL INFORMATION IN BALINT’S SYNDROME
Georgina M. Jackson1, Rachel Swainson1, Dominic Mort2, Masud Husain2 and Stephen R. Jackson1
(1Institute of Neuroscience, University of Nottingham; 2Division of Neuroscience and Psychological Medicine, Imperial
College, University of London)

INTRODUCTION
To perceive the world as a unitary whole we
need to integrate local features into separate and
coherent objects. Previous studies in neurologically
intact subjects have shown that information at a
global level can interfere with the processing of
local features (i.e., a global interference effect). For
instance, when asked to identify the smaller letters
in so-called ‘Navon’ stimuli, reaction times are
slowed if the global letter is different from the
smaller letters from which it is composed (Navon,
1981). Balint’s Syndrome is a relatively rare
disorder associated with bilateral parieto-occipital
damage (Balint, 1909). Patients presenting with this
syndrome show a profound deficit in identifying
multiple visual objects presented simultaneously
and in perceiving complex global scenes, even
when they can accurately report local details. We
made use of the global interference effect to
investigate whether the global deficit seen in
Balint’s Syndrome reflects a deficit in global
processing or in the awareness of global form.
Using event related potentials (ERPs) we
demonstrate that the patient processes global
information in the absence of explicit awareness.
CASE JJ
Our patient (JJ) is a 65-year-old right-handed
male who has suffered recurrent cerebral
haemorrhages over the past 6 years. A recent MRI
scan shows asymmetrical bilateral atrophy to areas
of the parietal, temporal and occipital cortices with
damage to the left parietal cortex extending further
into the superior region. JJ exhibits evidence of
simultanagnosia on a number of tasks. Firstly,
when presented with the Boston Cookie Thief
picture he can report only isolated items from the
picture.
Secondly, when presented with overlapping
figures taken from the Birmingham object
recognition battery (BORB) JJ only reports one
item from each pair. Thirdly, JJ requires 150msec
to report the identity and colour of a single
coloured letter stimulus but requires 2600 msec to
correctly report the identity and colour of a pair of
coloured letters. When given unlimited time to
report the global letter in a ‘Navon’ figure (e.g., is
Cortex, (2004) 40, 179-180

it a ‘u’, an ‘n’, or an ‘o’?), JJ’s performance is at
chance. In contrast, he is completely accurate
(100% correct) in reporting both the local letters in
the ‘Navon’ figure and non-compound letters
(whether filled or outline) of the same size as the
global ‘Navon’ figure. Importantly, while JJ is
unable to accurately report the identity of the
global figure, he is significantly slower to correctly
identify local letters in a ‘Navon’ figure if the
identity of the global letter differs from that of the
local letters [Means: Congruent = 733 msec,
Incongruent = 757 msec; F (1, 921) = 5.5; p =
0.02].
ERP study
Patient JJ performed a focused attention version
(i.e., identify the local level only) of the Navon
task (Miller and Navon, 2002). He was presented
with large (7°) compound stimuli consisting of
global ‘u’, ‘n’ (an upside down letter ‘u’), or ‘o’
stimuli made up of smaller letter ‘u’, ‘n’ or ‘o’
stimuli. The local ‘u’ and ‘n’ stimuli could thus be
congruent or incongruent with respect to the global
figure. Each stimulus was presented for 200 msec.
Note, with presentation durations of 200 msec JJ is
never able to report the identity of the global
figure. Sixty trials of each type were presented. JJ
was required to make a left button press to indicate
he had seen a letter ‘u’ and a right button press to
indicate the presence of an ‘n’. No response was
required to the letter ‘o’. JJ was allowed 2000
msec to respond. Response times were determined
from the onset of the visual stimulus until the
button-press. The first block of 60 trials was used
for practice.
ERP recording
High density event-related electrical potentials
(ERPs) were recorded using a 128-channel
geodesic sensor net coupled to a high input
impedance amplifier. EEG was continuously
recorded and digitised at 250 Hz. The continuous
EEG was then segmented into one-second epochs
time-locked to the onset of each visual stimulus,
commencing 100msec prior to stimulus onset.
ERPs were transformed using an average reference
transform, and low-pass filtered with a cut-off
frequency of 45Hz.

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Georgina M. Jackson and Others

Fig. 1 – Visual event-related potentials recorded over occipito-temporal cortex of the left hemisphere of patient JJ when presented
with congruent (black) and incongruent (green) Navon figures (see text for details). Data reveal a significant early increase in the
positive-going waveform (P160) for incongruent trials that is then followed by a later decrease in the negative-going waveform (N400)
for incongruent trials. Significant time samples shaded red (p < 0.05, 2-tailed T-test). B Current source density (CSD) plots showing the
topography of current sources and sinks at 400 msec after stimulus onset for congruent and incongruent trials demonstrating an
enhanced negativity (N2) centred over frontal (Fz) cortex for incongruent trials.

The epoch was baseline corrected using data
from the 100msec prior to stimulus onset.
ERP RESULTS
A number of differences can be observed in the
visual evoked potentials between the congruent and
incongruent conditions. These are shown in Figure
1. At 160 msec after stimulus onset there is a
significant increase in the positive-going
waveforms recorded over the occipito-temporal
cortex of the left hemisphere (P160) for
incongruent trials. Later, at 400 msec after stimulus
onset, there is a significant decrease in the
negative-going waveform (N400) for incongruent
trials. Finally, a priori examination of the frontal
N2 recorded over FZ shows an increased N2
magnitude for incongruent trials. These differences
between the congruent and incongruent condition
demonstrate that JJ is processing to identification
global level information that he cannot report.
DISCUSSION
JJ was unable to report the identity of the global
level figure when presented with ‘Navon’ figures.
However, his identification of large, non-compound,
letters was always excellent, as was his ability to
accurately report the local level features. In spite of
JJ’s inability to report the global identity, his RT
performance and the ERP data indicate that his
visual system is extracting global information, and
that this information is being processed to
identification. Consistent with our finding of a left

occipito-temporal locus of ERP differences between
congruent and incongruent trials, a recent PET study
of normal subjects demonstrated that reporting the
local level of ‘Navon’ figures was associated with
activation within the inferior occipital cortex of the
left hemisphere (Fink et al, 1997). Similarly,
Proverbio et al. (1998) in an ERP study of normal
subjects, found increased negativity for congruent
compared with incongruent trials over occipitotemporal sites, when the task required the reporting
of local information. In conclusion, even though JJ
is unaware of global information, the pattern of his
ERPs is concordant with that previously reported in
normal subjects.
Acknowledgements. This work was supported by a
BBSRC grant awarded to GMJ, and a Leverhulme Trust
Special Research Fellowship to RS. MH is supported by a
grant from The Wellcome Trust.
REFERENCES
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FINK GR, HALLIGAN PW, MARSHALL JC, FRITH CD, FRACKOWIAK
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MILLER J and NAVON D. Global precedence and response
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Dr.Georgina M. Jackson, Division of Psychiatry, Behavioural Sciences, University of
Nottingham, Queen’s Medical Centre, Nottingham NG7 2UH. E-mail:
georgina.jackson@nottingham.ac.uk