Clinical Implications of EEG and ERP as Biological Markers for Alzheimer's Disease and Mild Cognitive Impairment

OBJECTIVES: Memory impairment is a very important mental health issue for elderly and adults. Mild cognitive impairment (MCI) is a prodromal stage of Alzheimer's disease (AD). Early detection of the prodromal stage of patients with AD is an important topic of interest for both mental health clinicians and policy makers. METHODS: Electroencephalograpgy (EEG) has been used as a possible biological marker for patients with MCI, and AD. In this review, we will summarize the clinical implications of EEG and ERP as a biological marker for AD and MCI. RESULTS: EEG power density, functional coupling, spectral coherence, synchronization, and connectivity were analyzed and proved their clinical efficacy in patients with the prodromal stage of AD. Serial studies on late event-related potentials (ERPs) were also conducted in MCI patients as well as healthy elders. Even though these EEG and ERP studies have some limitations for their design and method, their clinical implications are increasing rapidly. CONCLUSION: EEG and ERP can be used as biological markers of AD and MCI. Also they can be used as useful tools for early detection of AD and MCI patients. They are useful and sensitive research tools for AD and MCI patients. However, some problems remain to be solved until they can be practical measures in clinical setting.

Gender Difference in Event Related Potentials to Masked Emotional Stimuli in the Oddball Task

OBJECTIVE: We investigated gender differences in event-related potential (ERP) responses to subliminally presented threat-related stimuli. METHODS: Twenty-four participants were presented with threat-related and neutral pictures for a very brief period of time (17 ms). To explore gender differences in ERP responses to subliminally presented stimuli, we examined six ERP components [P1, N170, N250, P300, Early Posterior Negativity (EPN) and Late Positive Potential (LPP)]. RESULTS: The result revealed that only female participants showed significant increases in the N170 and the EPN in response to subliminally presented threat-related stimuli compared to neutral stimuli. CONCLUSION: Our results suggest that female participants exhibit greater cortical processing of subliminally presented threat-related stimuli than male participants.

ERP Components Associated with Emotional Processing in Anxiety Disorder

This article aimed to describe typical event-related potentials (ERP) components of emotional processing in patients with anxiety disorder and highly anxious individuals. ERP components associated with emotional processing could be broadly divided into three components with short, middle and long, respectively. Many studies show that patients with anxiety disorders are characterized by different emotional bias to specific stimuli and more sensitive to emotional stimuli than normal individuals. In addition, these emotional biases were stronger and quicker in patients with anxiety disorder than normal individuals. Some studies reported that anxious people show abnormality at the initial stage (e.g. P1) of emotional processing. However, other studies reported the abnormality at the late stage (e.g. LPP) or wholeness of emotional processing in anxious individuals. We summarized the updated finding of possible ERP components of emotional processing in patients with anxiety disorder and highly anxious individuals. The significance and clinical implication were discussed.

Impairement of Gamma Oscillation in Patients with Schizophrenia / 대한정신약물학회지

Neural oscillations are a fundamental mechanism for enabling coordinated activity during normal brain functioning and are therefore a crucial target for schizophrenia research. Schizophrenia has been known to be associated with disturbances of neural oscillations, and these disturbances of neural oscillations could be implicated with cognitive deficit. Synchronized oscillations have been shown to establish the precision in spike timing that is crucial for use-dependent synaptic plasticity. Gamma oscillations have been proposed to represent reference signals for temporal encoding, sensory binding of features into a coherent percept, and storage and recall of information. Conversely, disruption of gamma oscillations could underlie some psychiatric disorders, such as schizophrenia and Alzheimer's disease. Gamma-aminobutyric acid interneurons are known to be important for the synthesis of gamma band. Among them, the fast-spiking cells that contain the calcium-binding protein parvalbumin (PV) appear to play a particularly critical role in the generation of synchronized gamma activity. Knowledge about PV neurons is insufficient yet. However, evidences for the role of gamma band impairement specific to the schizophrenia is accumulating. Through more assertive researches, we anticipate that futher roles of gamma band could be come out someday.

Effects of a New Antipsychotic Drug (YKP1447) on Impaired Prepulse Inhibition Induced by Apomorphine and Phencyclidine in Rats / 대한정신약물학회지

OBJECTIVE: Schizophrenia, a devastating mental disorder, displays a wide range of cognitive impairments including attentional impairment. Prepulse inhibition (PPI), in which a startle response to a loud acoustic noise is reduced by a preceding auditory stimulus of a lower intensity, is impaired in schizophrenic patients and rats injected with apomorphine (APO) or phencyclidine (PCP) mimicking attentional deficits in schizophrenics. Here we examined therapeutic efficacy of a newly developed atypical antipsychotic compound (YKP1447;YKP) on PPI impairment induced by various doses of APO and PCP. METHODS: This study was composed of 3 experiments. YKP (0.5-15 mg/kg) or vehicle (VEH) was administered 15 min before the injection of APO (0.5 mg/kg, Exp1) or PCP (2.0 mg/kg, Exp2:1.5 mg/kg, Exp3). They were then tested for PPI in which a mix of startle stimulus and prepulse was presented. RESULTS: APO or PCP treatment effectively impaired PPI in tested animals (VEH/APO or VEH/PCP). Impaired PPI in APO group was reversed in animals that were pretreated with YKP (5-10 mg/kg) (Exp1). However YKP treatment was not effective in PCP group (Exp2-3). CONCLUSION: High concentration of YKP pretreatment had antipsychotic effect on APO-induced impairment in attentional function suggesting that the compound could potentially be used to treat cognitive impairment due to increased dopaminergic receptorbinding.

The Effects of Pulsed Electromagnetic Stimulation on Functional Recovery Following Laryngeal Reinnervation in the Rat / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Ideal treatment for vocal cord paralysis is to restore normal movement of the vocal cord and to bring back the natural voice. Pulsed electromagnetic stimulation (PEMS)has been known to bring early nerve regeneration as well as better functional recovery. The purpose of this investigation is to learn the effect of PEMS on regeneration of the recurrent laryngeal nerve. MATERIALS AND METHOD: Using 36 healthy male Sprague-Dawley rats, we made transections on their left recurrent laryngeal nerves and performed primary anastomosis under the operating microscope. Rats were divided into an experimental group and a control group, each having 18 rats by random sampling. For the experimental group, PEMS was carried out three hours a day and five days a week for twelve weeks. For the control group, PEMS was not given while other conditions were kept the same as in the experimental group. The extent of functional recovery was observed for each group by performing videostroboscopic examination once every week. After twelve weeks, a test for the functional recovery was performed electrophysiologically through laryngeal electromyography during respiration. RESULTS: After the twelve-week experiment, 14 out of 18 rats survived in the group which received PEMS while 8 out of 18 rats stayed alive in the control group. Ten rats (71%)in the PEMS performed group and 3 rats (38%)in the control group showed recovery of vocal cord movement, but it did not reveal any significant difference statistically. However, the time it took for functional recovery was 3.93+/-0.27 weeks and 7.87+/-0.85 weeks for the PEMS performed group and the control group, respectively. And the difference was statistically significant. CONCLUSION: This investigation confirmed the efficacy of PEMS on the early functional recovery in rats with surgically transected and reanastomosed recurrent laryngeal nerve. Further studies to understand the mechanism of action of these effects as well as the local stimulation rather than the total body stimulation seem to be necessary.

Effects of Sertraline on the 1% Sucrose Consumption and the Body Weight Following Chronic Unpredictable Mild Stress in Rats / 신경정신의학

The study was designed to evaluate the effects of sertraline on l% sucrose intake and weight change in rats with chronic unpredictable mild stress and normal controls. We applied 11 types of stress regimens and identified depressive behaviours in 18 Spraque-Dawley rats for 8 weeks. After 4 weeks of chronic unpredictable mild stress procedure, those 18 rats were stratified into a sertraline-treated subgroup and a saline subgroup. Also nonstressed 18 rats were stratified into the sertraline-treated subgroup and the saline subgroup and were started intraperitoneal injections of sertraline(4.29mg/Kg) or saline for rest of 4 weeks. The 1% sucrose intake and the body weight were checked on the 4th day of every week, over the 8 weeks of experiment. The results were as follows: 1) The sertraline-treated subgroup of chronic unpredictable mild stressed rats showed significant increase of 1% sucrose intake between the 1st week and the 2nd, the 3rd and 4th week, while the sertraline-treated subgroup of non-stressed rats showed decreasing trend for 1% sucrose intake. 2) The sertraline-treated subgroup of chronic unpredictable mild-stressed rats showed a sustained decrease of body weight, while the sertraline-treated subgroup of non-stressed rats showed a non-significant increase of body weight. 3) In the group subjected to chronic unpredictable mild stress, there were no significant correlations between 1% sucrose intake and body weight and also no correlations in the nonstressed group. In summary, sertraline had an effect on restoring the decreased 1% sucrose intake to normal condition but no effect on regaining the body weight in the chronic unpredictable mild stresstreated rats. Sertraline resulted in a decrease of l% sucrose intake and no effect on body weight in the non-stressed rats.

Effects of Combined Treatment with Fluoxetine and Choline on the Retention of Passive Avoidance Learning after Chronic Mild Stress in Rat / 신경정신의학

This study was performed to evaluate the effects of serotonin and choline on the memory function in rat model of depression. Chronic exposure to mild unpredictable stress was found to depress the consumption of sweet 1% sucrose solution in the Sprague-Dawley rats. We identified depressive behaviours in 27 Sprague-Dawley rats. Rats in experiments were stratified into 3 groups, ie, fluoxetine with choline, choline, and saline control. Memory function was evaluated by passive avoidance learning and retention tests. We evaluated how long memory retention would remain improved at training-testing intervals of 1 day, 1 week, 2 week, 3 week, and 4 week in depressive state of the Sprague-Dawley rats during 4 weeks of experimental drugs treatment. The results were as follows: 1) The fluoxetine with choline-treated group showed significant differences in the maintenance of retention from the saline control at 1, 2, 3, and 4 week training-testing interval. 2) The choline-treated group showed significant differences in the maintenance of retention from the saline control at 3 and 4 week training-testing interval. In summary, the combined treatment of fluoxetine with choline showed earlier effects on memory function compared with choline alone in the passive avoidance retention test in the animal model of depression. We suggest that there are synergistic interaction between serotonin and choline in the long term memory function in rat model of depression.