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Essay / Schizophrenia Essay - 784
Schizophrenia is a devastating and costly mental disorder that affects 1% of the world's population. Patients manifest clusters of positive, negative, and cognitive symptoms in their early 20s and are often left with severe mental disability and lifelong social stigma. Cognitive deficits in patients with schizophrenia are considered the main symptoms of this disorder and may manifest in the initial stage (Elvevåg and Goldberg, 2000). Atypical antipsychotics improve positive symptoms but can only modestly improve cognitive symptoms (Richelson, 2010). In addition to this, some of the typical antipsychotics even have impairing effects on cognitive symptoms (Heaton and Crowley 1981). To find appropriate treatments for the cognitive deficits of schizophrenia, it is important to know the underlying pathophysiology. Cognitive deficits in schizophrenia affect “executive functions” which involve working memory, reasoning, and task flexibility (Cho et al., 2006). Executive function such as “set switching” refers to the ability to modify ongoing behavior in response to a change in strategy to achieve the goal (Floresco et al., 2008). The literature suggests that different neurotransmitters are involved in the pathophysiology of cognitive deficits in schizophrenia. The dopamine hypothesis of schizophrenia has long gained prominence due to increased dopaminergic activity in subcortical areas of the brain associated with positive symptoms of schizophrenia. In contrast to increased dopaminergic activity in the subcortical area, data indicate that dopaminergic activity is decreased in the prefrontal cortex in schizophrenia patients (Perlstein et al., 2001). Reduced dopamine D1 receptors and dopamine fiber density... middle of article...... chizophrenia is unclear. We wonder whether these anomalies appear simultaneously or whether one precedes maintenance or whether they appear in combination. Impaired ability to alter intuitive attentional set constitutes a core feature of schizophrenic illness and is associated with prefrontal cortical abnormality. To assess executive functions in rats, we will use a set-shifting task. The set-shift task requires rats to learn visual cue discrimination and then switch to a response discrimination strategy to obtain a reinforcer (sucrose pellet). Our preliminary results show that control rats perform approximately 75 trials to reach the successful performance criterion in the set-shifting task. We predict that rats infused with GABA, dopamine, and/or glutamate antagonists in the prilimbic cortex will require a greater number of trials than control rats to reach performance criterion...