Schizophrenic Perception of Faces Schizophrenia

Schizophrenic Perception of Faces

Schizophrenia and Perception of Faces

Much research has already been done that shows patients with schizophrenia have problems identifying faces and their emotional expressions. Chen, Norton, Ougur and Heckers (2007) wanted to know if "the visual detection of a face as face is impaired as well" (p. 1). In other words, do schizophrenic patients recognize that a face they see is a face? For the normal person, it is easy to recognize a face. To be unable has negative social consequences for the schizophrenic patient because it greatly curtails social interaction. The significance of this study then is that knowledge of the mechanisms involved in the detection of faces could lead to interventions and improvement of the schizophrenic patient's social functioning and social life.

For human beings, the face is a "special class" of visual object. The researchers point out, "it is known that the processes involved in face recognition are qualitatively different from those involved in recognition of other visual objects" (Chen et al., 2007, p. 1).

According to the researchers, facial detection takes place within a distinct system in the brain designed for facial recognition, a system that normally processes and uses facial information efficiently and functions independently from the need to identify other objects. "Facial information is processed in a special brain system that includes the fusiform face area in the temporal cortex (FFA)" (Chen et al., 2007, p. 6). The researchers hypothesized that an inability to identify a face as a face, the first stage of information processing, would suggest that some kind of impairment exists in the FFA system. Processing facial information involves at least three perceptual components, visual processing, analysis of identity, and recognizing emotions in facial expressions. This study focuses on the first stage, which is visual processing when the individual first perceives a face and recognizes it as such.

Methods

The researchers reasoned that to find out whether schizophrenia patients recognize faces as faces, they needed to isolate face detection from other aspects and stages of facial recognition, such as identity and emotional affect. They use the term face detection "to indicate the awareness of the mere presence of a face" (Chen et al., 2007, p. 2). Their task was to limit or eliminate any clues about identity and emotion so they could get at information about face detection in schizophrenia without other stages of perception.

Their research design involved five strategies. First, they designed a line drawn face as stimulus, which did not convey any clues about emotion or who the face might belong to. Secondly, they decided to expose subjects to these line drawn faces for very brief durations of time. Making the exposure short also helped isolate the detection part of the process from other considerations like gender, age, identity, etc. Thus, the task of the subject was to see if a face-like stimulus was present in a short period of time. The researchers also measured whether the subjects could detect a non-face visual object. They utilized a line-drawn tree for this part. The tree image contained the same number of line segments as the face did and had other similar characteristics (brightness and complexity, for example). The researchers measured stimulus inversion effect as well, since even among normal individuals, recognition is known to be disrupted when a face is encountered upside down. This is not the case with other objects.

29 of the subjects in this study were persons who had been positively diagnosed for either schizophrenia or schizoaffective disorder. Experienced clinicians that did not know the purpose of the study interviewed them and found that they met the criteria in DSM-IV. None of the patients had any neurological history like strokes or seizures, they had normal IQs, and had been free of substance abuse for at least six months. All the subjects in the patient group were taking antipsychotic medicines. 28 subjects comprised the normal control group. They were recruited through a newspaper ad and had no histories of Axis I psychiatric disorders.

The subjects were shown images on a computer screen for 13, 26, 52, or 104 ms, sometimes upright and sometimes inverted, and were asked to indicate, by pressing one of two keys on a keyboard, whether the image of a face or a tree was located on the left side or on the right side of each drawing.

Results

Schizophrenia patients exhibited significantly less accuracy when they tried to detect upright and inverted faces than normal controls did. Stimulus durations made no difference as the deficit existed across all durations.

Unlike the detection of faces, tree detection was not significantly different for the two groups. A reduced stimulus inversion effect in schizophrenia was shown primarily in faces but not in tree detection. The only interaction shown to be significant was between group and stimulus orientations (upright or inverted). Other interactions were not significant. Tree detection was more accurate in normal controls than in patients, but this finding was independent of stimulus orientation. Antipsychotic drugs that patients were taking did not appear to be correlated with their accuracy in face detection.

Conclusion

The first stage of facial information processing appears to be impaired in schizophrenia. This would be the first and most basic perception in the brain's facial information processing system. The researchers argue that face recognition is "categorically different from recognition of other visual objects" and that a deficit in recognizing a face as a face in schizophrenia patients indicates a problem or impairment in the FFA part of the brain. They argue this because the problem is with detecting faces and not with detecting other visual objects. The researchers state, "The results of this study suggest that this is the case" (Chen et al., 2007, p. 5). For schizophrenics the face inversion effect was significantly greater than for tree inversion. The researchers argue this also indicates something wrong in the first stage of visual detection of faces. Schizophrenia patients exhibited very little inversion effect when they were detecting trees. Their stimulus inversion effect for trees did not significantly differ from controls. But the patients did show significant differences in inversion effect when detecting faces. This "suggests an impairment specific to facial information processing in schizophrenia" (p. 6) and suggests that poor face detection in schizophrenia is linked to dysfunctional FFA (an impairment in the fusiform face area in the temporal cortex). Schizophrenics may be using a different or "less efficient, cortical mechanism" for processing facial information, or it may be they cannot access the normally "highly efficient, face-specific brain system" (p. 7).