Neurolepsis: Anhedonia or blunting of emotional reactivity?

Affective status in relation to impulsive, motor and motivational symptoms: personality, development and physical exercise

The contributions of impulsive and risk-taking behaviour in depressive and bipolar disorders, motivational and motor behaviours in anhedonic and substance addictive states, and the factors, particularly distress and trauma, underlying the development of neuropathology in affective status are described from clinical, epidemiological and laboratory perspectives. In order to distinguish one case factor for biopsychological substrates of health, an array of self-reported characteristics, e.g., positive or negative affect, stress or energy, optimism, etc., that may be predictive or counterpredictive for the propensity for physical exercise and activity were analysed using a linear regression in twelve different studies. Several individual characteristics were found to be markedly and significantly predictive of the exercise propensity, i.e., positive affect, energy, health-seeking behaviour and character, while optimism was of lesser, though significant, importance. Several individual characteristics were found to be significantly counterpredictive: expression of BDI- and HAD-depression, major sleep problems and lack/negligence of health-seeking behaviour. The consequences of physical activity and exercise for both affective well-being, cognitive mobility and neurogenesis is noted, particularly with regard to developmental assets for younger individuals. Affective disorder states may be studied through analyses of personal characteristics that unfold predispositions for symptoms-profiles and biomarkers derived from properties of dysfunction, such as impulsiveness, temperament dimensions, anhedonia and 'over-sensitivity', whether interpersonal or to reward.

Dopamine and reward: the anhedonia hypothesis 30 years on

The anhedonia hypothesis--that brain dopamine plays a critical role in the subjective pleasure associated with positive rewards--was intended to draw the attention of psychiatrists to the growing evidence that dopamine plays a critical role in the objective reinforcement and incentive motivation associated with food and water, brain stimulation reward, and psychomotor stimulant and opiate reward. The hypothesis called to attention the apparent paradox that neuroleptics, drugs used to treat a condition involving anhedonia (schizophrenia), attenuated in laboratory animals the positive reinforcement that we normally associate with pleasure. The hypothesis held only brief interest for psychiatrists, who pointed out that the animal studies reflected acute actions of neuroleptics whereas the treatment of schizophrenia appears to result from neuroadaptations to chronic neuroleptic administration, and that it is the positive symptoms of schizophrenia that neuroleptics alleviate, rather than the negative symptoms that include anhedonia. Perhaps for these reasons, the hypothesis has had minimal impact in the psychiatric literature. Despite its limited heuristic value for the understanding of schizophrenia, however, the anhedonia hypothesis has had major impact on biological theories of reinforcement, motivation, and addiction. Brain dopamine plays a very important role in reinforcement of response habits, conditioned preferences, and synaptic plasticity in cellular models of learning and memory. The notion that dopamine plays a dominant role in reinforcement is fundamental to the psychomotor stimulant theory of addiction, to most neuroadaptation theories of addiction, and to current theories of conditioned reinforcement and reward prediction. Properly understood, it is also fundamental to recent theories of incentive motivation.

Olanzapine attenuates the reinforcing effects of cocaine

The possibility that the atypical neuroleptic olanzapine can antagonize the ability of cocaine to produce both conditioned place preference and self-administration in rats was investigated. Pre-treatment with olanzapine (3.0, 4.5 mg/kg, but not 1.5 mg/kg) significantly attenuated conditioned place preference produced by cocaine (10 mg/kg). However, the higher dose of olanzapine administered alone resulted in conditioned place aversion. Pre-treatment with olanzapine also produced a dose-dependent decrease in cocaine self-administration (0.33 mg/infusion) under a fixed-ratio 2 schedule of reinforcement. Olanzapine produced a similar dose-responsive attenuation in operant responding for food (fixed-ratio 10) suggesting that olanzapine produces a nonspecific decrease in operant behavior. Pre-treatment with 4.5 mg/kg olanzapine significantly attenuated cocaine-induced hyperactivity, whereas lower olanzapine doses had little effect upon cocaine-induced hyperactivity. These results suggest that pre-treatment with olanzapine is capable of blocking the reinforcing effects of cocaine and illustrates the value of using multiple tests of reinforcement when evaluating the pharmacological effects of newer psychotherapeutic agents.