The goal of this study is to understand why some people become stuck in repetitive negative thinking, which is common among individuals with depression and anxiety. Repetitive negative thinking involves repeatedly focusing on negative events, worries, or problems. These thoughts can be difficult to control and may worsen emotional distress and daily functioning.

Researchers believe that repetitive negative thinking may be related to changes in how different brain networks communicate with each other. This study will examine how the brain responds during emotion regulation tasks in people who tend to ruminate compared with healthy individuals.

To do this, researchers will use a brain-imaging technique called functional near-infrared spectroscopy (fNIRS). This method measures brain activity using harmless infrared light while participants perform tasks on a computer.

The main questions this study aims to answer are:

How does the brain respond to emotional situations in people who experience repetitive negative thinking?

Are there differences in brain activity between people with depression or anxiety and healthy individuals during emotion regulation?

Participants will include 50 healthy volunteers and 50 individuals with depression or anxiety who experience repetitive negative thinking.

Participants will:

Wear a lightweight brain-imaging device (fNIRS) placed on the head to measure brain activity

Complete computer tasks involving emotional images and different emotion-regulation strategies, such as reinterpreting, suppressing, or distracting from emotions

Listen to different types of spoken feedback (criticism, praise, or neutral comments) and imagine receiving them from someone they know

Report their emotional feelings during the tasks

Complete several questionnaires about mood, thinking patterns, and emotional experiences

During the experiment, researchers will also record physiological responses such as heart activity and skin reactions, which are related to emotional responses.

The results of this study may help researchers better understand the brain mechanisms underlying rumination and may contribute to the development of more effective treatments for depression and anxiety.

Repetitive negative thinking (RNT), also known as rumination, is a key aspect of both depression and generalized anxiety disorder (GAD). RNT involves a pattern of repeated and uncontrollable negative thinking, often leaving individuals feeling trapped in a cycle of worrisome thoughts and gloomy ruminations. These cognitive processes can significantly impact both the emotional state and daily functioning of those suffering from it. In depression, RNT is often associated with constant rumination on negative events, past mistakes, and feelings of hopelessness. This repetitive and negative thinking often reinforces feelings of despondency and can further depress mood. In GAD, RNT manifests as persistent worry about numerous potential future dangers and problems, even when the actual threat is minimal.

RNT is considered an underlying mechanism involved in several psychiatric disorders. RNT not only amplifies the intensity of negative emotions but can also contribute to the duration and severity of psychological symptoms. Addressing RNT is increasingly recognized as a crucial target for both future research and clinical interventions. By better understanding the complex relationship between rumination and mental health disorders, we can not only elucidate the onset and progression of these disorders but also develop more targeted treatments aimed at disrupting the negative thinking patterns that characterize RNT.

Research has demonstrated abnormal neuronal activity in people with depression or GAD who also experience RNT. Previous studies using functional magnetic resonance imaging (fMRI) have demonstrated atypical functional connectivity (FC) and brain activity in specific regions of the Central Executive Network (CEN), the default mode network (DMN), and the Salience Network (SN) during computer-based tasks measuring emotion regulation in individuals with depression and GAD, compared to healthy controls.

For this reason, the focus of our research is on identifying the specific neural, cognitive, and emotional mechanisms that fuel and maintain rumination.

A promising approach for this research is Functional Near-Infrared Spectroscopy (fNIRS), an optical brain imaging technique that uses infrared light for functional neuroimaging. fNIRS measures brain activity by detecting shifts in the concentrations of oxidized and deoxidized hemoglobin, making it one of the most widely used non-invasive neuroimaging methods with remarkable temporal resolution. The primary goal of this study is to investigate differential brain responses during emotion regulation tasks in patients with RNT compared to healthy controls using fNIRS.

The research group will include both healthy controls (n = 50) and individuals with depression and anxiety who exhibit tendencies toward RNT (n = 50). The fNIRS device will be placed on the participants' heads to record brain activity, while two experimental paradigms will be used simultaneously to investigate emotion regulation: 1) Emotion Regulation Task; 2) Criticism Paradigm.

The Emotion Regulation Task initially involves two conditions: simple presentation of neutral images ("neutral viewing") and simple presentation of negative images ("negative viewing"). These conditions are presented sequentially, with the goal of measuring the engagement of the cognitive control network during emotional responses. Participants receive on-screen prompts before beginning each task in each condition. At this stage, a "Look" prompt is presented, asking participants to notice their feelings toward the neutral or negative image and respond naturally. At the end of each trial, participants are asked to rate their emotions at that moment. Additionally, the study includes three emotion regulation conditions, randomly assigned to each participant: positive reappraisal of negative images ("positive reappraisal"), suppression of feelings toward negative images ("suppression"), and distraction from negative images ("distraction"). For the "Reappraisal" prompt, participants are asked to reinterpret aversive images by creating a story to make the images less negative or even more positive. In the "Distraction" prompt, participants are asked to quickly determine whether a given mathematical equation hovering over negative images is correct or incorrect by pressing a button. In the "Suppression" prompt, , participants are expected to suppress their emotions regarding the image.

The Criticism paradigm involves participants listening to a series of auditory comments while focusing their gaze on a fixation cross displayed on a computer screen. These comments comprise three emotional tones: negative (criticism), positive (praise), and neutral. Each comment lasts 30 seconds and is alternated with 30 seconds of silence. All participants are exposed to the same comments and instructed to imagine that they are listening to someone who knows them very well. This section begins with two neutral comments, followed by two positive comments, and concludes with another two neutral comments followed by two negative comments.

Resting-state measurements are also performed before and after the emotion regulation task and the criticism paradigm.

Resting-state measurements are also performed before and after the emotion regulation task and the criticism paradigm.

During the computer task and resting state measurement, we collect physiological data regarding heart and skin functions. This includes measuring heart rate (ECG), cardiac activity (ICG), and skin reactions (SCR). These physiological measurements are linked to emotion regulation.

In addition, participants' behavioral measurements are assessed using various questionnaires, including demographic data, MINI-screening, HDRS (for patients only), PC, VAS-emotion, MAIA, BDI, STAI, PSWQ, LARSS, RRS, CERQ, PTQ, self-critical rumination.

Inclusion Criteria:

• Patient group: diagnosis of depression/GAD
• Healthy control group: no history of or current form of psychopathology

Patient group mainly consists of individuals diagnosed with depression or generalized anxiety disorder (GAD).