الفهرس 
Introduction.Only 14 pages are availabe for public view
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Abstract
Anhedonia as a psychopathological symptom was first noted in the early 19th century. The term “anhedonie” was introduced in clinical psychiatry over a century ago when Ribot, 1896 first defined anhedonia as the “insensibility relating to pleasure alone”. Anhedonia has been observed in various psychiatric disorders e.g. major depressive disorder, schizophrenia, schizo-affective disorder, substance use disorders. Anhedonia is one of the two core symptoms of depression. Among patients with MDD, about 40% have clinically significant anhedonia. Anhedonia is recognized as core negative symptom of schizophrenia. Yet available treatments targeting anhedonia and related negative symptoms in schizophrenia are non-existent. Anhedonia may be defined according to types of activities that can produce pleasure; ”physical anhedonia” refers to decreased ability to experience pleasure from physical activities such as eating, touching, and sex, while ”social anhedonia” refers to decreased pleasure in social interactions. Another distinction regarding different forms of anhedonia; that is concerned with pleasure experience in the moment (consummatory anhedonia) and the expectation of future experiences would be pleasurable (anticipatory anhedonia). Evidences suggests that there are specific neuroanatomical areas underling various facets of reward processing, including the prefrontal cortex (orbitofrontal cortex ’’OFC’’, ventromedial prefrontal cortex ’’vmPFC’’ and anterior cingulate cortex ’’ACC’’), dorsal striatum (caudate and putamen), nucleus accumbens and amygdala. Anhedonia can arise from deficits in various aspects of reward processing, e.g. desire for reward, anticipation/prediction of reward, effort to gain reward, consummatory pleasure and cognitive aspects of learning stimulus-reward associations. Anhedonia has been traditionally measured with self-report questionnaires. While these can give an indication of the subjective experience of anhedonia. The most popular way for assessment of anhedonia was selfreport scales or questionnaires e.g. The Fawcett–Clark Pleasure Scale or The Snaith–Hamilton Pleasure Scale ”SHAPS”. Currently there is no available treatment approved by the Food and Drug Administration (FDA) selective for improving anhedonia in major depression. Residual anhedonia might persist even after remission of MDD in about 14% of patients, associated with poor clinical outcomes. Study findings on emotional ’’experience’’ are heterogeneous. Patients with schizophrenia report higher levels of anhedonia, compared with healthy individuals. In schizophrenia literature, studies asking about current feelings of positive emotion revealed that patients provide ’’inthe- moment’’ reports that are similar to controls. According to the discrimination between ’’anticipatory’’ and ’’consummatory’’ anhedonia in schizophrenic patients, most studies reflects deficits in anticipatory pleasure, but not in consummative experience. Despite the contradictory results, many researchers defined the discrepancy between the ’’current’’ (state/ or consummatory) and ’’non-current’’ (trait/ or anticipatory) pleasure experience in schizophrenia as “emotion paradox”. Reviews of behavioral and neuroscience literature suggested that depressed individuals demonstrate difficulty in rewardrelated processing and abnormalities in brain systems involved in reward process.