The dopaminergic system, and in particular the dopamine D2 receptor, has been implicated in reward mechanisms. The net effect of neurotransmitter interaction at the mesolimbic brain region induces “reward” when dopamine (DA) is released from the neuron at the nucleus accumbens and interacts with a dopamine D2 receptor. “The reward cascade” involves the release of serotonin, which in turn at the hypothalmus stimulates enkephalin, which in turn inhibits GABA at the substania nigra, which in turn fine tunes the amount of DA released at the nucleus accumbens or “reward site.” It is well known that under normal conditions in the reward site DA works to maintain our normal drives. In fact, DA has become to be known as the “pleasure molecule” and/or the “antistress molecule.” When DA is released into the synapse, it stimulates a number a DA receptors (D1-D5) which results in increased feelings of well-being and stress reduction. A consensus of the literature suggests that when there is a dysfunction in ...

Reward deficiency syndrome: a biogenetic model for the diagnosis and treatment of impulsive, addictive, and compulsive behaviors.

We studied 14 patients with obsessive-compulsive disorder (OCD) by positron emission tomography and the fluorodeoxyglucose method, looking for abnormalities in local cerebral metabolic rates for glucose in brain structures that have been hypothesized to function abnormally in OCD. These patients were compared with 14 normal controls and 14 patients with unipolar depression. The patients with unipolar depression and OCD did not differ in levels of anxiety, tension, or depression. In OCD, metabolic rates were significantly increased in the left orbital gyrus and bilaterally in the caudate nuclei. This was apparent on all statistical comparisons with both controls and unipolar depression. The right orbital gyrus showed at least a trend to an increased metabolic rate in all comparisons. The metabolic rate in the left orbital gyrus, relative to that in the ipsilateral hemisphere (orbital gyrus/hemisphere ratio), was significantly elevated compared to controls and subjects with unipolar depression, and stayed high even with successful drug treatment. Though it was in the normal range in the morbid state, with improvement in OCD symptoms after drug treatment, the caudate/hemisphere metabolic ratio increased uniformly and significantly bilaterally. This ratio did not increase in patients who did not respond to treatment. Thus, OCD showed cerebral glucose metabolic patterns that differed from controls in both the symptomatic and recovered states.

Local Cerebral Glucose Metabolic Rates in Obsessive-Compulsive Disorder: A Comparison With Rates in Unipolar Depression and in Normal Controls

Reviews research on brain damage, psychiatric disorders, and normal emotion, which has shown the importance of the right hemisphere's holistic and nonverbal conceptualization to emotion. Studies of hemispheric asymmetries in psychiatric patients have suggested the importance of specific and apparently lateralized arousal systems in the brain that support the differential cognitive capacities of the 2 cerebral hemispheres. The operation of these arousal systems seems to vary closely with the individual's affective state. Research on emotional effects of unilateral lesions has suggested that the hemispheres may be specialized not just for the kind of emotion but for its valence, positive or negative. Research issues and methods in this area are still at an early stage of development, yet it seems clear that further research on the lateralization of emotion should reveal how emotional processes are at one level dependent on basic neurophysiological activation processes and at another level intrinsic to the differential forms of conceptualization of the 2 cerebral hemispheres. (3½ p ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

Lateral brain function, emotion, and conceptualization.

• Three retrospective studies were conducted to examine functional brain asymmetry in the regulation of emotion. In the first study, reports of 119 cases were collected of pathological laughing and crying associated with destructive lesions. Pathological laughing was associated with predominantly right-sided damage, whereas pathological crying was associated with predominantly left-sided lesions. In the second study, 19 reports detailing mood following hemispherectomy were collected; right hemispherectomy was associated with euphoric mood change. In the third study, lateralization of epileptic foci was assessed in reports of 91 patients with ictal outbursts of laughing (gelastic epilepsy). Foci were most likely to be predominantly left-sided. The findings are congruent with studies of the effects of unilateral brain insult on mood, and a general model of hemispheric asynmetry in the regulation of emotion is presented.

Hemispheric Asymmetry in the Expression of Positive and Negative Emotions: Neurologic Evidence

Clinical application of the P3 component of event-related potentials. II. Dementia, depression and schizophrenia.

Evoked potential correlates of psychosis.

Somatosensory evoked potential (SEP) changes associated with selective attention were investigated. In 16 subjects, SEPs were recorded from five locations while they counted electrical stimuli to one of four randomly stimulated fingers. Sequential SEP events measured included peaks P30 (positivity at 30 msec). P45, N60, P100. N140. P190. N230, P400. Counting was associated with greater P45, P100. P190, N230, and P400 amplitudes; effects were not attributable to eye or tongue activity. Analyses designed to reveal changes associated with two conceptualized “channels” (finger class, hand) showed that the P45, P100, and P190 amplitude increases involved both channels. The P400 effect was limited to the target finger. Channel effects for N60 and N140 amplitudes resulted from decreases localized to the unattended element of one channel, suggesting “inhibition.” Latency effects involved mainly the hand channel; counted hand latencies were shorter for P30, P45, P100 and P190. The findings indicate modifications of both early and late electrocortical events with selective attention, and that changes can be of several kinds. They support the view that attention proceeds in more than one stage.

Somatosensory Evoked Potential Changes With a Selective Attention Task

Evoked potentials of schizophrenics in several sensory modalities.

• Psychiatric diagnostic correlates of EEG measures were Investigated in 242 unmedicated patients and 94 nonpatients. Computer analysis of eyes-open and eyes-closed EEGs (12 leads) provided time series of amplitude, frequency, and wavesymmetry measures; mean levels and temporal variability Indexes were also factor analyzed across leads. Comparisons between various age-and sex-matched groups disclosed numerous differences. Compared with those of nonpatients, schizophrenics' EEGs showed lower amplitude variability, greater frequency variability, greater wave symmetry, and less reactivity to eye opening. The EEGs of schizophrenic subgroups, including latent schizophrenics, were similar and also like those of manics. The EEGs of manics and major depressives differed markedly. The EEGs of subjects with personality disorders and schizophrenics differed from nonpatients in opposite directions. Groups could be classed according to the level of EEG activation: high included manics and schizophrenics; normal, nonpatients and neurotics; and low, major depressives and those with personality disorders.

John J. Straumanis

Papers

Evoked potential correlates of psychosis.

Somatosensory Evoked Potential Changes With a Selective Attention Task

Evoked potentials of schizophrenics in several sensory modalities.

Relationships between psychiatric diagnosis and some quantitative EEG variables.

Pattern evoked potential measurements suggesting lateralized hemispheric dysfunction in chronic schizophrenics.