Attentional modulation of source attribution in schizophrenia

In patients with schizophrenia, the misattribution of
self-generated events to an external source is associated with
self-recognition deficits and the presence of psychotic symptoms.
The aim of the present study was to investigate how this
misattribution is influenced by dysfunction of attentional
processing, which is also impaired in schizophrenia. I conducted
two different studies. In both studies participant’s expectancies
were manipulated using visual cues that were either congruent
(valid) or incongruent (invalid) with the speech. The source
(self/alien) and the acoustic quality (undistorted/distorted) of
the speech were also manipulated. First, twentythree patients with
schizophrenia, with hallucinations and delusions (H/D patients) and
twentythree matched healthy controls (HC) were tested for the
behavioral study. Later on, twenty patients with first episode
psychosis (FEP) and twenty matched healthy controls (HC) underwent
functional Magnetic Resonance Imaging (fMRI) while listening to
prerecorded speech. The results of the behavioral part of the study
showed that H/D patients exhibited increased error rates comparing
to HC, when listening to the distorted self spoken words,
misidentifying their own speech as produced by others. Importantly,
patients made significantly more errors across all the invalid cue
conditions. This suggested not only the presence of pathological
misattribution bias, but also an inadequate balance between
top-down and bottom-up attentional processes in patients, which
could be responsible for misattribution of the ambiguous sensory
material. Analysis of fMRI data showed that FEP patients when
listening to self-generated speech preceded by an invalid (alien)
cue, relative to HC showed a strong trend to misidentify their own
speech as an other person's. The patient group had reduced
activation in the right middle temporal gyrus (MTG) and left
precuneus (Pc) relative to HC. Within the FEP group, the level of
activation in the right MTG was negatively correlated with the
severity of their positive psychotic symptoms. I conclude that
impaired attentional modulation in schizophrenia may contribute to
the tendency for FEP patients to misattribute the source of
self-generated material, and this may be mediated through the right
MTG and Pc, regions that are involved in both self-referential
processing and the integration of sensory information.