This abstract is taken from my PhD thesis, submitted in 2008.
Functional Brain Electrical Activity Imaging during Affective Facial Processing in People with Schizophrenia
Empirical evidence suggests impaired affective facial processing in schizophrenia. However, the nature of this deficit is the subject of ongoing study. The current study used the Steady-State Probe Topography (SSPT) technique to examine early and late stages of identity- and emotion-matching in people previously diagnosed with schizophrenia. This was done in order to examine whether these deficits were generalised to different types of facial processing or were emotion-specific, and whether deficits on these tasks could be associated to differences in frontal and temporal functioning compared to matched controls.
Steady-State Visually Evoked Potentials (SSVEPs) were recorded at 64 electrodes from 34 normal controls, whose elicited SSVEP differed across gender, so each gender was examined separately. SSVEPs were recorded from 14 people previously diagnosed with schizophrenia and were compared to a group of 15 age-, IQ- and gender-matched controls derived from the normal control group. In normal controls, early SSVEP changes were recorded at prefrontal and temporal cortices associated in both conditions with bilateral prefrontal activation in females and left prefrontal activity and right-sided inhibition in males. Late SSVEP changes appeared to differ between genders with left frontal activity in males and continued bilateral prefrontal activity in females. Males demonstrated longer continued occipitotemporal activity in both conditions. People previously diagnosed with schizophrenia exhibited early and late SSVEP changes at prefrontal and occipitotemporal regions during emotion-matching while they were associated with SSVEP changes in prefrontal and temporal regions during identity-matching. The activity of the prefrontal regions was greater than matched controls in both conditions, with greater increases observed later in both tasks. In normal controls this early prefrontal activity was associated with differing gender-specific processing of early visual stimuli, concurrent with temporal processes. Later processes were interpreted as differing gender-specific strategies involved with extracting task relevant information. In people previously diagnosed with schizophrenia, this greater activity in the prefrontal cortex was associated with compensatory mechanisms that occurred in spite of sufficient posterior temporal activity in early physical processing of the stimuli. This compensatory activity may have been associated with subcortical communication to the prefrontal cortex. A second experimental design was administered to find further evidence of frontal dysfunction in schizophrenia evident from the first experiment. Neuropsychology tests were conducted with 21 people diagnosed with schizophrenia and 20 matched controls. There were significant differences between both groups on frontal tasks of language and speeded attention, but no correlations were observed between these frontal tasks and face processing. A final comparison was conducted with data from the two experimental subject groups combined. This analysis examined 35 people previously diagnosed with schizophrenia and 35 matched controls. Deficits in both affective and non-affective face processing were observed, with correlations between affective face processing and positive and general psychopathology symptoms of schizophrenia. These findings were interpreted as a generalised face processing deficit with greater deficits in affective facial processing, in part, due to cognitive symptoms of schizophrenia.