The aim of this research is to investigate the neurolinguistic mechanisms underlying thought
disorders among schizophrenic patients. In particular, it will investigate the
neurolinguistic basis for loose association - a phenomena which this population is
characterized by. Several researchers have previously suggested that loose associations among
schizophrenic patients relate to a lack of inhibition in the automatic spread of activation
mechanisms within semantic networks (e.g., Soriano, Jimenez, Roman, & Bajo, 2008). This
research focuses on the relationship between I. the left-right hemisphere dynamic and II.
semantic processing, among schizophrenic patients. The research follows Jung-Beeman's (2005)
model which relates semantic associations, activation and inhibition processes to the
functioning of the two cerebral hemispheres.
Previous research suggests that, when compared to the neurotypical population, people with
schizophrenia show a less defined - or even reversed - hemispheric lateralization pattern for
semantic processing. This is linked to an impairment in language function in the left
hemisphere, and to a language functions shift from left to right hemisphere (e.g., Crow,
1997). The investigators assume that this unique lateralization pattern may cause a change in
balance in the semantic activation and inhibition system among schizophrenic patients.
As stated, one of the linguistic models that predicts how reduced left hemisphere dominancy
will influence linguistic functioning is Jung-Beeman's (2005) bilateral model for language
understanding. According to this model, the left hemisphere specializes in precise and fine
semantic processing, while the right hemisphere specializes in coarse and abstract semantic
processing. Building upon this distinction, our assumption is that schizophrenic patients
experience a difficulty in fine semantic processing which is caused by functional impairment
in the left hemisphere. It is our further assumption that coarse semantic processing -
located in the right hemisphere - is relatively unimpaired. This change in the balance
between the two processes may have direct implications on the associative semantic network
among schizophrenic patients.
In order to test this hypothesis, the current research will make use of a specific language
expression type which involves fine and coarse semantic processing, and for which there is
evidence for crucial right hemisphere involvement: novel metaphor processing. 10-20 adult
schizophrenic patients will be presented with four different types of two word expressions:
literal; conventional metaphor; novel metaphor and unrelated. The patients will have to
decide as quickly and accurately as possible if the expression is meaningful or meaningless
while their brain activity is recorded by a Magnetoencephalographic (MEG) device (which
combines a high temporal resolution with the ability to localize the activity).
Therefore, our main hypothesis is that schizophrenic patients will show a bilateral brain
activity pattern when conducting semantic decisions, and that this pattern will be related to
improved reaction times and accuracy when presented with novel metaphors than when presented
with other types of expressions.