Browsing by Author "Gonul, Ali Saffet"

Now showing 1 - 5 of 5

The Effects of Late-Onset Depression on Brain Activity During an Episodic Memory Task
(Turkish Neuropsychiatry Assoc-Turk Noropsikiyatri Dernegi, 2025) Gulec, Zeynep Naz; Ercan, Melis; Erdogan, Yigit; Oguz, Kaya; Uyar, Aslihan; Burhanoglu, Birce Begum; Gonul, Ali Saffet
Introduction: Late-onset depression (LOD) has been implicated in irreversible cognitive decline, potentially mirroring early Alzheimer's Disease (AD) pathology. This study aimed to investigate brain activity differences during an episodic memory (EM) task in LOD patients compared to healthy controls (HC). Methods: We recruited 15 LOD patients and 13 HC matched for age and gender. Participants completed a face-name association task during functional magnetic resonance imaging (fMRI) focusing on both the encoding and retrieval phases of EM. Results: The statistical contrast between the groups revealed that the HC group showed increased activity in the left visual association cortex (VAC) and left caudate compared to the LOD group during the encoding task. During the face recognition task, the HC group showed increased activity in the right caudate, and during the name recognition task, they showed increased activity in the right frontal eye field (FEF) compared to the LOD group. Conclusion: The differences observed between the HC and LOD groups in the VAC, caudate, and FEF suggest early changes in maintaining attention, goal-directed learning, EM formation, and coordination of information from storage to retrieval before apparent impairment develops in LOD. Although we did not find statistically significant activations in areas linked to increased vulnerability to AD, our findings of hypoactivation regions responsible for visual processing and attentional orienting in LOD patients are consistentwith hypoactivation patterns observed in AD patients in previous research. These results enhance our understanding of the neural mechanisms underlying memory impairments in LOD and their potential overlap with AD pathology.
Citation - WoS: 4
Citation - Scopus: 8
Emotional Context Effect on Recognition of Varying Facial Emotion Expression Intensities in Depression
(Elsevier, 2022-07) Yildirim-Celik, Hande; Eroglu, Seda; Oguz, Kaya; Karakoc-Tugrul, Gulser; Erdogan, Yigit; Isman-Haznedaroglu, Damla; Eker, Cagdas; Gonul, Ali Saffet
Background: Previous research has indicated that Major Depressive Disorder (MDD) patients have deficits in the process of facial emotion recognition. In most of these studies, isolated emotional faces were used, and the effect of the surrounding context of the face was neglected. We aimed to investigate how context emotion (sad or happy) affects facial emotion recognition and whether this effect is different in depressive individuals compared to the control group. Methods: Happy, sad, neutral facial expressions with congruent and incongruent visual contexts were presented to 51 MDD patients and 42 matched healthy controls. Emotional facial expressions are presented as morphs gradually expressing happiness or sadness with 40% and 80% intensity levels. Mean reaction time, mean accuracy rate, and mean emotion intensity rating score was calculated for each condition. Results: The performances on facial emotion intensity rating and accuracy rate were similar between MDD patients and controls. MDD patients were slower to recognize all facial emotions and to recognize facial emotions with emotionally incongruent backgrounds compared to congruent ones. Limitations: Antidepressant therapy of patients might have affected our results. Conclusions: Emotional contextual features have an important role in facial emotion recognition but this effect is independent of depression. Longer reaction time in depression may be related to some cognitive impairments.
Citation - WoS: 1
Gradual Loss of Social Group Support During Competition Activates Anterior Tpj and Insula but Deactivates Default Mode Network
(MDPI, 2023-10-25) Özkul, Burcu; Candemir, Cemre; Oğuz, Kaya; Eroğlu-Koç, Seda; Kizilates-Evin, Gozde; Ugurlu, Onur; Erdoğan, Yiğit; Gonul, Ali Saffet
Group forming behaviors are common in many species to overcome environmental challenges. In humans, bonding, trust, group norms, and a shared past increase consolidation of social groups. Being a part of a social group increases resilience to mental stress; conversely, its loss increases vulnerability to depression. However, our knowledge on how social group support affects brain functions is limited. This study observed that default mode network (DMN) activity reduced with the loss of social group support from real-life friends in a challenging social competition. The loss of support induced anterior temporoparietal activity followed by anterior insula and the dorsal attentional network activity. Being a part of a social group and having support provides an environment for high cognitive functioning of the DMN, while the loss of group support acts as a threat signal and activates the anterior temporoparietal junction (TPJ) and insula regions of salience and attentional networks for individual survival.
Citation - WoS: 1
Citation - Scopus: 1
Robust Activation Detection Methods for Real-Time and Offline Fmri Analysis
(Elsevier Ireland Ltd, 2017-06) Oguz, Kaya; Cinsdikici, Muhammed G.; Gonul, Ali Saffet
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 (TAM), Instantaneous Activation Method with Past Blocks (TAMP) 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. (C) 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Task-Dependent Functional Connectivity Changes in Response To Varying Levels of Social Support
(Cambridge Univ Press, 2024-09) Burhanoglu, Birce Begüm; Uslu, Özgül; Özkul, Burcu; Oğuz, Kaya; Eroğlu-Koç, Seda; Kizilates-Evin, Gozde; Candemir, Cemre; Gonul, Ali Saffet
Background Having social support improves one's health outcomes and self-esteem, and buffers the negative impact of stressors. Previous studies have explored the association between social support and brain activity, but evidence from task-dependent functional connectivity is still limited.Aims We aimed to explore how gradually decreasing levels of social support influence task-dependent functional connectivity across several major neural networks.Method We designed a social support task and recruited 72 young adults from real-life social groups. Of the four members in each group, one healthy participant (18 participants in total) completed the functional magnetic resonance imaging (fMRI) scan. The fMRI task included three phases with varying levels of social support: high-support phase, fair phase and low-support phase. Functional connectivity changes according to three phases were examined by generalised psychophysiological interaction analysis.Results The results of the analysis demonstrated that participants losing expected support showed increased connectivity among salience network, default mood network and frontoparietal network nodes during the fair phase compared with the high-support phase. During the low-support phase, participants showed increased connectivity among only salience network nodes compared with the high-support phase.Conclusions The results indicate that the loss of support was perceived as a threat signal and induced widespread increased functional connectivity within brain networks. The observation of significant functional connectivity changes between fair and high-support phases suggests that even a small loss of social support from close ones leads to major changes in brain function.