Biomedical subjects

Erhan Nalçaci

Publications and source records attributed to Erhan Nalçaci.

5 recordsLinked to original sources

PubMed2006

Directional preferences in turning behavior of girls and boys.

Turning biases in humans and animals are known to be related to dopaminergic asymmetry between the brain hemispheres. A laboratory method, in which turning preference was evaluated, was adapted based upon the turning of the subject toward a particular sound in a square room. One of the aims of this study was to investigate the reliability of this method with children, and the other aim was to research the turning preference in boys and girls. 31 children between 7 and 13 yr. old volunteered as subjects, and 17 subjects were retested. The subjects tended significantly to turn leftward (60.1%), and fewer girls (53.7%) turned to the left than boys (66.2%). The correlation between the test and the retest was significant (r=.79, p< .01). Most studies have indicated that humans in childhood and adulthood exhibit left-turning preference, but conflicts between the results obtained on different types of rotation tasks have suggested that hemispheric dopaminergic activity might affect preference. That needs study.

Acoustic Stimulation↗

PubMed2004

Time-frequency analysis of visual evoked potentials for interhemispheric transfer time and proportion in callosal fibers of different diameters.

This study is an extension of the experimental research of Nalçaci et al., who presented 16 subjects with a reversal of checkerboard pattern as stimuli in the right visual field or left visual field and recorded EEG at O1, O2, P3, and P4. They applied the chosen bandpass filters (4-8, 8-15, 15-20, 20-32 Hz) to the VEPs of subjects and obtained four different components for each VEP. The first aim of this study is to improve the previous report using some methods in time-frequency domain to estimate interhemispheric delays and amplitudes in a time window. Using the improved estimates of interhemispheric delays, the second aim is to estimate the proportion of callosal fibers of different diameters that are activated by visual stimuli by comparing amplitudes of VEPs in different frequency bands. If the relation between frequency components of VEP and delays for callosal fibers of different dimension were reliable, it would give us an opportunity to deal with amplitude of bandpass-filtered VEPs in order to see approximately the proportion of these fibers activated by a certain stimulus. By using frequency-dependent shifts in time and maximizing the cross correlation of direct VEP (DVEP-VEP obtained from contralateral hemisphere)-indirect VEP (IVEP-VEP obtained from ipsilateral hemisphere) pairs in the time-frequency domain, we examined the delay not only at P100 and N160 peaks but along a meaningful time interval as well. Furthermore, by shifting back the IVEP according to the delay estimated at each time window, both the amplitudes and energies of the synchronized DVEP-IVEP pairs were compared at the chosen frequency bands. The percentages of IVEPs at each band was then examined further in conjunction with the distribution of axon diameters in the posterior pole of the CC, questioning the relation between the distributions of the axon diameters and activations at each band. We established an energy definition to express the activation in the fibers. When the energy percentages of IVEPs in theta and alpha were totaled, they were found to be between 76.2% and 81.6%, which is close to the value 74-77% for fibers of 0.4-1 microm in diameter obtained from anatomical study of human CC. The sum of energy percentages in the beta1 and beta2 bands was between 20.1% and 24.2%, which probably reflects the proportion of activation of callosal fibers 1-3 microm in diameter.

Adult↗

PubMed2003

Line bisection task performance and resting EEG alpha power.

Neurologically normal subjects generally err to the left of veridical center when performing a line bisection task, a phenomenon termed "pseudoneglect." We hypothesized that resting electroencephalogram (EEG) alpha oscillations may show relationships with attentional mechanisms and give some clues about the underlying mechanisms of pseudoneglect. We recorded resting EEGs of 41 subjects and tested them with a paper-pencil line bisection task. Our results showed that line bisection scores of men (n=18) were less biased and their performance was higher compared to those of women (n=20), but these differences only approached significance. The eyes open resting EEG alpha power of women was significantly and positively correlated with their line bisection performance. In general, significant relationships were related to the left hand performance when the lines were presented in the left hemispace. Greater resting alpha power was correlated with lower absolute bisection score or, in other words, higher bisection performance. Greater alpha power also correlated with diminished leftward bisection bias (or reduced pseudo-neglect). The resting EEG alpha of men was weakly associated with bisection performance. Results discussed in terms of Kinsbourne's activation-orientation theory and Basar's view on brain oscillations.

Adult↗

PubMed2003

[Reliability and validity of Turkish version of magical ideation scale in university students].

OBJECTIVE: Schizoptypal disorder shares many clinical, neuropsychological and neurophysiological features with schizophrenia and is included in the schizophrenia spectrum. Patients with schizotypal disorder or individuals with mild schizotypal features are therefore highly valuable in the study of neuropsychological and neurophysiological characteristics of psychosis, and in particular schizophrenia, as they are likely to be free of the potential confounding factors of medication, chronic hospitalization and manifest psychosis. We report here the psychometric properties of the Turkish version of the Magical Ideation Scale (MIS), a self-report questionnaire that focuses on delusion-like beliefs and hallucination-like experiences and that has been used to quantify an important dimension of schizotypy. METHOD: Internal consistency and high cut-off scores were studied in 332 medical students. Forty-three students were readministered the scale 3 weeks later, and 96 received the Paranormal Belief Scale-R (PBS-R) along with the MIS, in order to measure test-retest reliability and convergent validity, respectively. RESULTS: The internal consistency of the scale is satisfactory with a Cronbach alpha coefficient of 0.78. Test-retest scores are highly correlated (r= 0.84). The high cut-off score is 21 for males, 23 for females, and 22 for the whole sample. Convergent validity was established by the significant correlation between the total MIS and PBS-R scores (r= 0.61). CONCLUSIONS: The scale is valid and reliable for studies that require a standard quantification of schizotypal signs and symptoms in young university students.

Adolescent↗

PubMed2002

[Reliability and validity of a handedness questionnaire].

OBJECTIVE: In this study, the validity and reliability of the hand preference item of a 13-item questionnaire adapted from Chapman and Chapman (1987) were investigated. METHOD: This questionnaire requires subjects to indicate which hand they usually use for various actions as follows: writing, drawing, throwing, using a hammer, using a toothbrush, using an eraser on paper, using scissors, holding a match when striking it, stirring a can of paint, using a spoon, using a screwdriver, twisting off the lid of a jar, and using a knife. Each item was scored as "1" for right, "2" for either, or "3" for left, and the handedness of subjects was scored from 13 (the strongest right-hand preference) to 39 (the strongest left-hand preference). In this study, 449 subjects filled in the questionnaire, and 43 subjects attended the test-retest study 3 weeks after the first examination. In order to determine the validity of the questionnaire, fine motor performance was measured using a finger tapping task, and the eye and foot preferences of the subjects were evaluated. RESULTS: The test-retest reliability (r=.993) and internal consistency (Cronbach's Alpha=.97) were found to be high. In item-total score analysis, the best single item was "using a hammer", while the worst item was "twisting off the lid of a jar". Factor analysis yielded two factors, skilled and unskilled activities. Handedness scores were found to show a significant correlation with foot preference scores and the dominance score of the finger tapping task. CONCLUSION: The results suggest that the handedness questionnaire is reliable and valid in measuring handedness.

English Abstract↗