llucinations may be auditory, visual, or tactile. Auditory hallucinations occur most frequently and often are manifested as voices inside the head which make derogatory and insulting comments. Tactile hallucinations, the least common, are often experienced as external touching or a creeping sensation under the skin. Visual hallucinations are typically perceived as the presence of persons who are not really there. Delusions, which are irrational beliefs held in the face of contradicting evidence, may take on persecuted, grandiose, or religious tones. Delusions may also be experienced as part of the thinking process. The schizophrenic may believe that his or her thoughts are under someone else's control or that thoughts are being removed from (thought withdrawal) or placed in (thought insertion) his or her head. It is believed that positive symptoms are caused by an excess of dopamine in the mesolimbic region of the brain (Discussion of schizophrenia, 1998).
Negative symptoms, which take away from a person's mental experience or behavior, involve a
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