Cem Atbaşoğlu

Aspects of foot preference: differential relationships of skilled and unskilled foot movements with motor asymmetry.

In this research different aspects of foot preference were examined in 50 participants. The relationship between foot preference, hand preference, and hand/foot-tapping performance was analysed in detail. For foot preference, a practical behavioural test consisting of 14 daily foot movements was developed. After statistical analysis, five items were dropped. The test–retest reliabilities of the nine-item foot preference test and the foot-tapping task were found to be high. The factor analysis indicated a two-factor structure (skilled and unskilled foot movements). Foot preference in skilled and unskilled movements was correlated with hand preference and foot/hand-tapping speed. This correlation was found to be higher in skilled movements than in unskilled movements. Additionally, foot preference for skilled movements was strongly lateralised. The results indicate that the motor control of fine movements is similar for upper and lower limbs. The fact of lateralisation indicates that skilled and unskilled foot movements utilise different pathways. We propose that the asymmetrical lateral (corticospinal) pathway controls skilled movements while the medial pathways control unskilled movements. We therefore suggest that both skilled and unskilled foot tasks should be evaluated separately in order to assess foot preference.

Cognitive control of a simple mental image in patients with obsessive–compulsive disorder

The nature of obsessions has led researchers to try to determine if the main problem in obsessive-compulsive disorder (OCD) is impaired inhibitory control. Previous studies report that the effort to suppress is one of the factors that increase the frequency of obsessive thoughts. Based on these results and those of the present study that suggest inferior parietal lobe (IPL) abnormality in OCD and findings of a recent study that reported the importance of the right posterior parietal cortex in cognitive control of a simple mental image, the present cognitive control paradigm study aimed to determine whether there is a difference in brain dynamics between OCD patients and non-obsessive controls while performing tasks that necessitate cognitive control of a simple mental image, and whether the right posterior parietal region is one of the regions in which a difference in activity between the OCD patients and controls would be observed. Functional brain imaging was performed while the participants attempted to suppress, imagine, or manipulate a mental image. The general linear model showed that there was a main effect of group and main effect of task. Accordingly, in all contrasts (suppression minus free-imagination, erasing minus free-imagination, and imagination minus free-imagination), the right IPL, right posterior cingulate cortex, and right superior frontal gyrus activity were lower in the OCD patients than in the healthy controls. These results and the observed correlations between activity levels, and symptom and subjective performance scores are discussed. In conclusion, the results of the present study and those of previous studies suggest that the main problem in OCD might be difficulty activating the right frontoparietal networks during tasks that require cognitive control, which might result in the intrusiveness of obsessive thoughts.

Metabolic Effects of Olanzapine and Quetiapine: A Six-Week Randomized,Single Blind, Controlled Study

The objective of this study is to compare the course of metabolic effects of olanzapine and quetiapine, two atypical antipsychotics with similar structure and receptor binding affinities but clinically observed different metabolic ef- fects. This 6 week, single blind, randomized, controlled study was carried out during a structured treatment protocol in a female inpatient service, thus enabled to control effects of energy expenditure and other life style related factors. Subjects were randomly assigned into olanzapine (n=15) and quetiapine (n=15) groups. Weight and calorie intake (CI) were meas- ured daily. Symptom severity and serum leptin levels (SLL) were measured biweekly. Serum lipids were measured at baseline and 6th week. Olanzapine treatment was associated with more severe weight gain (F=11.2, p<0.01), increase in CI (F=8.1, p<0.01) and a more disturbed lipid profile than quetiapine. The course of SLL were similar between the groups (F=1.39, p=0.26). Weight, CI and SLL changed in a similar pattern within the groups but the patterns were different for each drug, suggesting that the two drugs have different mechanisms for weight change. The explanation probably involves different affinities for 5HT2C receptors leading to different patterns of CI which we propose as possible targets of inter- vention to manage antipsychotic induced weight gain.

Total exposure duration and proximity of cessation of cannabis use predict severity of sub-clinical psychotic symptoms among former users

In a non-clinical military enrolment setting, former cannabis users (N=81), compared to substance-naïve controls (N=132), endorsed markedly elevated rates of schizotypy subscale scores on the Schizotypal Personality Questionnaire (SPQ). Total duration of exposure and proximity of cessation of cannabis use also had an important impact on the severity of psychosis-like symptoms.

How is cognitive control of a simple mental image achieved? An fMRI study.

The aim of this study was to determine the brain regions associated with suppressing the image of an object. We used functional magnetic resonance imaging (fMRI) during five mental tasks (imagining, suppressing, erasing, free thinking and resting) performed by the subjects. The analysis showed that the suppressing, erasing and imagining conditions all activated the parietal and prefrontal regions to a different extent. These results suggest that the regions associated with cognitive control were also activated while a simple mental process was performed. Additionally, the results showed that the parietal lobe is the key region for the suppression of a mental image.