Event-related potentials elicited by distractors in an auditory
oddball paradigm in schizophrenia
, Zvezdan Pirtos
, Martina Tomori
, David B. Vodus
University Psychiatric Hospital, Studenec 48, SI 1260 Ljubljana Polje, Slovenia
Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, SI 1525 Ljubljana, Slovenia
Received 18 November 2004; received in revised form 13 July 2005; accepted 20 July 2005
Patients with schizophrenia are affected more adversely than healthy controls by distracting conditions, due to their
inability to adequately apportion attentional resources to targets or distractors. We attempted to re-evaluate the effects of
distractors in 25 patients with chronic schizophrenia and in 12 controls. They performed an auditory target-detection task
with 1500 Hz tone distractors and an additional control condition where a 1500-Hz tone was used as the target. The rate of
target misses for patients with schizophrenia was 3.79% in non-distractor conditions and 14.79% in distractor conditions.
Significantly reduced N100 responses to distractors and distractor condition targets were found. P300 responses to all target
stimulus categories were reduced, but P300 responses to distractors were equal to those in the control group. There was a
reduction of P300 amplitudes to distractors in both groups; however, only the control group showed significant enlargement
of P300 amplitude when the distractors became the target stimuli. There is evidence that patients with schizophrenia tend to
be less able to allocate their attentional resources adequately to target vs. distractor stimuli. When the distractors became the
target stimuli, their responses remained unchanged, which suggests their inability to appropriately integrate stimulus
information with contextual information.
D 2005 Elsevier Ireland Ltd. All rights reserved.
Keywords: Attention; N200; P300
Information-processing deficits and attention ab-
normalities are a prominent feature of schizophrenia.
They are strongly associated with clinical and func-
tional impairments of the illness (Green, 1996; Braff,
1999). Patients with schizophrenia are generally more
vulnerable to distractors than healthy subjects (Olt-
manns and Neale, 1975; Moser et al., 2001). Even
simple perceptual overload may stress the informa-
tion-processing capacity (Hotchkiss and Harvey,
1990). However, not all the studies confirm these
0165-1781/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved.
* Corresponding author. Tel.: +386 1 5872 356; fax: +386 1 5284
E-mail address: firstname.lastname@example.org (A. Kogoj).
Psychiatry Research 137 (2005) 49 – 59