Kaya Oguz

Reduced left uncinate fasciculus fractional anisotropy in deficit schizophrenia but not in non-deficit schizophrenia

Aims:  Schizophrenia is a psychiatric disorder manifesting with heterogeneous symptom clusters and clinical presentations. The deficit syndrome is the condition defined by the existence of primarily negative symptoms, and patients with the deficit syndrome differ from non‐deficit patients on measures of brain structure and function. In the current study, by using diffusion tensor imaging (DTI), we investigated the frontotemporal connectivity that is hypothesized to differ between deficit and non‐deficit schizophrenia.

Three techniques for automatic extraction of corpus callosum in structural midsagittal brain MR images: Valley Matching, Evolutionary Corpus Callosum Detection and Hybrid method

Abstract Corpus callosum (CC) is an important structure for medical image registration. We propose three novel fully automated for the extraction of CC. Our first algorithm, Valley matching (VM), is based on fixed searched range in histogram processing and uses prior anatomical information for locating CC. The second one, Evolutionary CC Detection (ECD), based on genetic algorithm presents a new fitness function that uses anatomical ratios, instead of fixed prior knowledge without the need for preprocessing. The final one, called Evolutionary Valley Matching (EVM), takes advantages of the strong points of the first and second algorithms. The search space defined for ECD is reduced by VM which uses crowding method to find the peaks in the multi-modal histogram. Another important contribution of this study is that there is no existing method using genetic algorithm for extracting CC. Our proposed algorithms perform with the success rates up to 95.5%.

Automatic registration of structural brain MR images to MNI image space

Disease diagnosis has been made by experts examining the images obtained by magnetic resonance imaging (MRI) technique, the disease process is observed using images taken at different times. Brain MR images are registered to the standard brain atlases because the human brain has a complex structure and varies from person to person. Corpus Callosum (CC) has a big importance for medical image registration because it can be easily distinguished on T1-weighted structural brain MR images and does not vary prominently between individuals. In this study, from the midsagittal brain MR image that belongs to the patient CC is detected fully automatically via Valley Matching (VM) Algorithm. The contribution of this study is registration of patients MR image onto the Montreal Neurological Institute (MNI) image space by using automatically detected reference points.

Facial emotion recognition in remitted depressed women

Although major depressive disorder (MDD) is primarily characterized by mood symptoms, depressed patients have impairments in facial emotion recognition in many of the basic emotions (anger, fear, happiness, surprise, disgust and sadness). On the other hand, the data in remitted MDD (rMDD) patients is inconsistent and it is not clear that if those impairments persist in remission. To extend the current findings, we applied facial emotion recognition test to a group of remitted depressed women and compared to those of controls. Analyses of variance results showed a significant emotion and group interaction, and in the post hoc analyses, rMDD patients had higher accuracy rate for recognition of sadness compared to those of controls. There were no differences in the reaction time among the patients and controls across the all the basic emotions. The higher recognition rates for sad faces in rMDD patients might contribute to the impairments in social communication and the prognosis of the disease.

Genetic imaging study with [Tc-99m] TRODAT-1 SPECT in adolescents with ADHD using OROS-methylphenidate

Aim: To examine theeffects on the brain of 2‐month treatment withamethylphenidate extended‐release formulation (OROS‐MPH) using [Tc‐99m] TRODAT‐1SPECT in a sample of treatment‐naïve adolescents with Attention Deficit/Hyperactivity Disorder (ADHD). In addition, to assess whether risk alleles (homozygosity for 10‐repeat allele at the DAT1 gene were associated with alterations in striatal DAT availability. Methods: Twenty adolescents with ADHD underwent brain single‐photon emission computed tomography (SPECT) scans with [Tc‐99m] TRODAT‐1 at baseline and two months after starting OROS‐MPH treatment with dosages up to 1 mg/kg/day. Severity of illness was estimated using the Clinical Global Impression Scale (CGI‐S) and DuPaul ADHD Rating Scale‐Clinician version (ARS) before treatment,1 month and 2 months after initiating OROS‐MPH treatment. Results: Decreased DAT availability was found in both the right caudate (pretreatment DAT binding: 224.76 ± 33.77, post‐treatment DAT binding: 208.86 ± 28.75, p = 0.02) and right putamen (pre‐treatment DAT binding: 314.41 ± 55.24, post‐treatment DAT binding: 285.66 ± 39.20, p = 0.05) in adolescents with ADHD receiving OROS‐MPH treatment. Adolescents with ADHD who showed a robust response to OROS‐MPH (n = 7) had significantly greater reduction of DAT density in the right putamen than adolescents who showed less robust response to OROS‐MPH (n = 13) (p = 0.02). However, between‐group differences by treatment responses were not related with DAT density in the right caudate. Risk alleles (homozygosity for the 10‐repeat allele of DAT1 gene) in the DAT1 gene were not associated with alterations in striatal DAT availability. Conclusion: Two months of OROS‐MPH treatment decreased DAT availability in both the right caudate and putamen. Adolescents with ADHD who showed a robust response to OROS‐MPH had greater reduction of DAT density in the right putamen. However,our findings did not support an association between homozygosity for a 10‐repeat allele in the DAT1 gene and DAT density, assessedusing[Tc‐99m] TRODAT‐1SPECT. HighlightsMethylphenidate decreased DAT availability in both right caudate and putamen.Robust response to Methylphenidate greatly reduced DAT density in right putamen.No relation between homozygosity of 10‐repeat allele in DAT1 gene and DAT density was observed.

Robust activation detection methods for real-time and offline fMRI analysis

We propose two contributions with novel approaches to fMRI activation analysis. The first is to apply confidence intervals to locate activations in real-time, and second is a new metric based on robust regression of fMRI signals. These contributions are implemented in our four proposed methods; Instantaneous Activation Method (IAM), Instantaneous Activation Method with Past Blocks (IAMP) for real-time analysis, Task Robust Regression Distance Method (TRRD) for the new metric with robust regression and Instantaneous Robust Regression Distance Method (IRRD) for both contributions. For comparison, a statistical offline method called Task Activation Method (TAM) and a correlation analysis method are also implemented. The methods are initially evaluated with synthetic data generated using two different approaches; first using varying hemodynamic response function signals to simulate a wide range of stimuli responses, along with a Gaussian white noise, and second using no activity state data of a real fMRI experiment, which removes the need to generate noise. The methods are also tested with real fMRI experiments and compared with the results obtained by the widely used SPM tool. The results show that instantaneous methods reveal activations that are lost statistically in an offline analysis. They also reveal further improvements by robust fitting application, which minimizes the outlier effect. TRRD has an area under the ROC curve of 0,7127 for very noisy synthetic images, is reaching up to 0,9608 as the noise decreases, while the instantaneous score is in the range of 0,6124 to 0,8019 in the same noise levels.