Academic journal article Iranian Journal of Psychiatry

Cortical Alpha Activity in Schizoaffective Patients

Academic journal article Iranian Journal of Psychiatry

Cortical Alpha Activity in Schizoaffective Patients

Article excerpt

During the past few decades, the concept of oscillatory brain dynamics has attracted much attention in neuroscience research. Since the 1990s, applications of measurement of oscillatory activity have grown rapidly in clinical pathology. There are many studies in this field and our research group commenced research on pathological brain oscillations in bipolar disorder (1-3), attention-deficit/hyperactivity disorder (4, 5), and schizoaffective disorder (6). Schizoaffective disorder (SA) is a severe, chronic psychiatric disorder that consists of symptoms of schizophrenia and affective disorders concurrently (7), with a lifetime prevalence of 0.3% (7, 8) which is more common in females than males (9). Genetic findings suggest GABA-A receptor dysfunction influences the duration of inhibitory post synaptic current onto pyramidal cells in SA (especially in bipolar type) (10-12). Due to the association between cortical gamma oscillations (30-80 Hz) and excitatory-inhibitory activity generated between GABA interneuron cell assemblies and reciprocally connected glutamatergic cells (13, 14), a recent magnetoencephalography (MEG) study (15) investigated gamma activity in schizoaffective bipolar disorder. The authors reported an increased gamma power in remitted schizoaffective bipolar disorder, which represents an abnormalities in the cortical excitatory-inhibitory balance.

Furthermore, some biological and neuropathological evidence suggests specific deficits in serotonin (5-HT) receptor function in SA (16, 17). Serotonin plays the role of neuromodulator/neurotransmitter in the central nervous system (CNS). Given the extensive innervations of the serotonergic system within the CNS and the brain, the 5-HT system is involved in many functions, and it is the target of numerous drugs used to treat psychiatric and brain disorders. Among the cortical areas, the frontal lobe is the richest region in 5-HT receptors and serotonergic terminals.

Desired levels of 5-HT in the prefrontal and frontal cortices are necessary for behavioral inhibition and modulation of attention in humans.

5-HT axons have a large impact on generation of action potentials by establishing axo-axonic contacts; previous studies suggested a link between 5-HT levels and the magnitude of alpha oscillations from electroencephalography (EEG) (18).

However, the observations of 5-HT levels and alpha activity are inconsistent in SA. Some studies (16, 17) reported downregulation or upregulation of cortical serotonergic activity in SA that may affect the alpha oscillations, resulting in higher or lower alpha activity in the cortex .

To the best of our knowledge, few studies have analyzed the spontaneous EEG and visual evoked potentials of SA patients. Although spontaneous EEG of SA has been studied before, no study investigated the spontaneous EEG of SA patients with acute episodes. Therefore, the aim of this study was to analyze the resting state EEG alpha activity of SA patients with closed and open eyes. We hope the results of this study provide some insight into the mechanisms causing the disorder and also clarify the previously mentioned contradictory findings.

Materials and Method

Participants

For the study group, our sampling frame was the list of all patients referred to Razi psychiatric hospital (Tehran, Iran) and hospitalized in a five year period. Of the 131 adult patients with SA who were hospitalized in these five years, 76 patients were selected by a random sampling method. Then, the patients were evaluated considering the inclusion and exclusion criteria. All participants in this group met Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV-TR; American Psychiatric Association, APA, 2000) diagnostic criteria for SA as determined by an experienced psychiatrist; all had at least one episode in the past and were experiencing symptoms at the time of the study. Eight patients were excluded after evaluation due to psychiatric comorbidity, another eight were excluded due to substance abuse, seven were excluded due to epileptic seizures or severe head injuries, two were excluded due to major medical illness, and six were excluded due to their or their family's unwillingness to participate in the study. …

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