Çiğdem Özesmi

Effects of cigarette smoking on cognitive processing

Several previous studies have reported that cigarette smoking enhances performance of cognitive processing. These enhancements are generally attributed to the pharmacological effects of nicotine, while there is some debate whether the effects of smoking/nicotine are a result of recovery from abstinence. Evoked potentials (EPs) and event related potentials (ERPs) of the brain have been applied as an index of information processing in a wide variety of normal and cognitive impaired subjects. This study was carried out on 20 healthy students (23 ± 2.3 years old) from the medical faculty of City University. Study population comprised ten chronic cigarette smokers consuming an average of 14 ± 4.2 cigarettes per day, with a history of smoking for more than one year. Ten non--smokers served as control. Standard oddball paradigm was presented, and EEG activity was recorded at the Fz, Cz, Pz electrode sites. Twenty responses to target stimuli were averaged at each location. N1, P2, N2, and P300 components were evaluated in these recordings. Amplitudes were measured relative to prestimulus baseline, and peak latencies were defined as the time point of maximum amplitude. It was found that there were no significant differences between either N1, P2, N2, P300 amplitudes or peak latency values of cigarette smokers and non smokers. As a result, chronic cigarette smoking generally does not improve cognitive processing

Habituation of the Auditory Evoked Potential in a Short Interstimulus Interval Paradigm

The present experiment was carried out to investigate elicitation and habituation of the auditory event related potentials with stimulus trains utilizing a short interstimulus intervals (ISI) of 1500ms. Scalp event related potentials elicited by auditory stimuli were recorded in 10 male subjects. Thirty auditory stimuli were presented binaurally over headphones to every subject with a duration of 1000ms, each with a constant ISI of 1500ms. No task relevance was given to the stimuli. Wave-forms were collected using a Pentium 100 computer.

Electrodermal Activity in Nonmedicated Hyperthyroid Patients Having No Depressive Symptoms

The aim of the present study was to investigate whether the alteration in hypothalamic-pituitary-thyroid axis function results in electrodermal abnormality without causing marked psychiatric manifestations or not. Electrodermal activity was recorded with the skin conductance unit and IBM-AT computer. Basal levels of electrodermal activity (EDA), as well as responsivity to repeated insignificant acoustic stimulation were studied in 24 nonmedicated hyperthyroid patients and 35 healthy controls. The outcome of psychiatric rating scores indicated that patients had low anxiety scores and normal depression scores. The basal levels of thyroid hormones were higher in patients, when compared with the control group. On the analysis of EDA, we found lower onset latency and duration of the skin conductance response and higher skin conductance level in nonmedicated patients than healthy controls. The results above provide supporting evidence that the change of hypothalamic-pituitary-thyroid axis function results in abnormal EDA, without causing marked psychiatric manifestations.

The effect of immobilization stress on sensory gating in mice

Central sensory filtering processes can be demonstrated using a paired stimulus paradigm. Normal humans show a diminished, vertex-recorded midlatency (50 ms) of auditory evoked potential to the second of paired clicks (0.5 s apart), a phenomenon termed as auditory gating. A loss of 50 ms in auditory gating is strongly related to psychosis. The N40 auditory evoked potential (EP) in rats has been used to develop an animal model for the study of sensory gating mechanisms. Previous animal studies of auditory gating have used psychotomimetic drug administration to induce sensory gating. However, a nonpharmacologic model of deficient gating would be advantageous.In the present study we investigated the effect of immobilization stress on sensory gating in twelve adult male mice. Evoked responses to the paired auditory click stimuli from vertex location of scalp were recorded using a silver needle electrode, a bioelectric amplifier, and an analog-digital converter. The mice were exposed to immobilization stress (IS) for 3 h. Data showed that the N40 potential was depressed in response to the second of the paired stimuli before application immobilization stress. At the end of the 3-h immobilization, the depression of the second N40 response was not observed. It was concluded that sensory gating is present in the mice and acutely disrupted by stressful stimuli, as shown in human subjects and rats

The Relation Between Event Related Potential and Working Memory in Healthy Subjects

In numerous investigations the P300-component of the event related potential has proved a valid indicator of memory activities. The present study explores the amplitude and latency of the components of event-related potential regarding short-term memory task. Event related potentials, elicited by auditory stimuli, were recorded in 40 healthy subjects. For evaluating short term memory capacity of a subject, software in Delphi for Windows language was written. Algorithm of the software was the presentation of randomly selected four different digits for 4 seconds, removing it and waiting for subjects response, adding one digit, if response was true, otherwise decreased by one. After 20 trials, mean of recall time for true answers was computed. The subjects with high recall time showed prolonged latency of P300. A positive correlation was found between P300 latency and recall time. No correlation was found between N1, P2 and N2 latency or amplitude and recall time. These results suggest that memory problems are well correlated with the abnormalities of P300.

The Effects of Immobilization Stress on Electrodermal Activity and Brain Catecholamine Levels in Rats

The effects of immobilization stress on electrodermal activity (EDA); skin conductance response magnitude and rate, skin conductance level and habituation number, and brain catecholamine levels; norepinephrine (NE) and dopamine (DA) were investigated in rats. Electrodermal activity was recorded using constant current method. Brain catecholamine levels were determined by a spectrophotophlorometric method. Electrodermal activity parameters (except skin conductance level) increased during immobilization. It was observed that, during immobilization stress, the alteration of norepinephrine and dopamine levels in rat brain was related to cerebral region and the duration of immobilization stress. It was concluded that these electrodermal activity alterations can be attributed to the changes in central norepinephrine metabolism induced by immobilization.

EFFECT OF HYPERGLYCEMIA ON ELECTRODERMAL ACTIVITY IN DIABETIC RATS

This study investigated the relationship between hyperglycemia and electrodermal activity (EDA) parameters in streptozotocin (STZ) induced diabetic rats. The article evaluates the course of development of neurophysiological alterations in the peripheral nervous system in diabetic rats through EDA. Rats were made diabetic using a moderate dose of STZ (DI) and high dose (DII). The placebo group (P) was injected with physiological saline. EDA was recorded 1 h before the injection (beginning, 0, day), 1st day (one day after the injection) and 10th day. Skin conductance level (SCL) was lower in DII than P on the 1st and the 10th days. The SCL and SC fluctuation rate (SCFr) of DI were significantly lower on the 10th day compared to their first record. SC response rate (SCRr) was lower on the 10th day compared to the 1st day, in the DI. In the DI, SCL, SC fluctuation rate (SCFr) and SC response rate (SCRr) were lower on the 10th day compared to the 1st day. The DII was statistically higher in electrodermal non-responsiveness compared to other groups on the 1st day. The results obtained show that hyperglycemia affects the peripheral nervous system, and EDA parameters are affected by blood glucose level. It is suggested that EDA is a simple and non-invasive electrophysiological method in early diagnosis of diabetic neuropathy.

The relation between skin conductance level and plus-maze behavior in male mice

The present study examined the correlation between anxiety scores and skin conductance level in 29 male Swiss Albino mice. Skin conductance (SC) was recorded with the SC unit and IBM-AT computer. Anxiety scores of mice were obtained from the elevated plus-maze test. The main result of the present study indicates that SC levels (SCLs) are negatively correlated with plus-maze behavior scores (both entries and time spent on the open arms). Our results are consistent with the findings which suggests that the higher the anxiety level the higher the SCL. This study further demonstrates the utility of SCL as a measurement for identifying anxiety in mouse. The interrelation between SCLs and plus-maze scores and possible explanations of the results are discussed.

Effect of PUVA therapy on electrodermal activity parameters in vitiligo patients

UNLABELLED Recent electrophysiological studies on autonomic dysfunction in vitiligo patients show an autonomic dysfunction as measured by absent sympathetic skin response (SSR). Nothing is known about the reversibility of these autonomic parameters with treatment. The present study examined how Electrodermal Activity (EDA) parameters were affected from vitiligo illness before PUVA therapy and whether any electrophysiological gains acquired from PUVA therapy would influence the progression of the condition itself. We studied in 14 healthy subjectS and 14 patients with generalized vitiligo before and after treatment. EDA was recorded with a skin conductance unit connected to a personal computer. Before treatment, skin conductance level (SCL) and habituation number (HN) was higher in vitiligo group than control groups. After treatment, SCL and HN were decreased nearly to normal value. Before and after treatment, prevalence of non-responsivity was higher in vitiligo group than controls. CONCLUSION The sympathetic nervous system might have a particular role in the pathogenesis of vitiligo. Thus, patients with vitiligo may have changes to EDA parameters that are reversible to great extent with PUVA therapy. EDA is a useful method of studying the autonomic dysfunction in humans.

SEX-RELATED DIFFERENCES IN TIME ESTIMATION AND THE ROLE OF EXPECTANCY

In this study, using auditory sequences, the authors designed an examination with three phases of stimulus-driven attention that is based on the possibility that involuntarily time shifts of attention are caused by nonunique stimulus properties. The purpose was to investigate whether attending and temporal expectancies are influenced by stimuluss properties and by sex. In each phase, an auditory stimulus train was presented, and the participant was asked to tap rhythmically in order to anticipate every fifth stimulus (or, in the third phase, the lack of it). The time between button pressing and stimulus onset was measured using a computer. Time estimation was accepted as a false response if the subject responded before 150 ms or 150 ms later from onset stimulus time. Error numbers were greater in Phase 3 and there was no significant difference between the male and female subjects for any of the phases when error numbers were compared. On the other hand, males pressed the button more accurately than females. Time estimation performance was affected by sex and expectancy-related motor responses are very important for time estimation.