Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
If the negative emotions experienced in life become trauma, they affect daily life. Neuro-feedback technology has recently been introduced as a treatment, but many different neuro-feedback protocols and methods exits. This study conducted a meta-analysis of neuro-feedback training for post-traumatic stress disorder (PTSD) symptoms to evaluate the effects of functional magnetic resonance imaging (fMRI) and electroencephalogram (EEG)-based neuro-feedback training. A search of PubMed, the Cochrane Library, Web of Science, Science Direct, and ClinicalTrials.gov was conducted from January 2011 to December 2021. The studies’ quality was assessed using the Cochrane risk of bias tool and publication bias was assessed by Egger’s regression test. Seven studies that met the inclusion criteria were used for the systematic review and meta-analysis. EEG was more effective than fMRI for PTSD symptoms, and the effect on PTSD symptoms was higher than on anxiety and depression. There was no difference in the effectiveness of the training sessions. Our findings showed that EEG-based neuro-feedback training was more helpful for training PTSD symptoms. Additionally, the methods were also shown to be valid for evaluating clinical PTSD diagnoses. Further research is needed to establish a gold standard protocol for the EEG-based neuro-feedback training (EEG-NFT) method for PTSD symptoms.
Keywords: post-traumatic stress disorder, PTSD, PTSD symptoms, neuro-feedback training, NFTMany individuals fail to endorse their negative reactions at the time of an event [1]. It is estimated that one in ten people who experience trauma develop symptoms of post-traumatic stress disorder (PTSD) [2]. Like PTSD, mood indicators can comprise a loss of interest or pleasure in activities, guilt, or loneliness [3] and have abnormal brain activity patterns [4]. PTSD is characterized by re-experiencing a traumatic event and negative alterations in mood and cognition [1]. PTSD symptoms affect personal and social life conditions [5], and PTSD symptoms may vary in severity depending on the level of the symptoms the individual feels. The association between PTSD and deficits in emotion regulation is well established [6]. PTSD is treated using four main therapeutic techniques [7], which include cognitive behavioral therapy, exposure therapy, eye movement desensitization and reprocessing [EMDR], and pharmacotherapy [8]. However, there is no single standard treatment for PTSD [7] and, especially in the case of pharmacotherapy, 41% of the patients who receive the treatment fail to respond [4].
For PTSD, self-regulation, increased neuroplasticity, and the recapture of the brain’s functional network are the primary factors which are important in healing [9]. Neuro-feedback (NF) is a relatively new technique that allows us to target certain brain areas for developing neuroscience-guided therapy [10]. It is a form of behavioral training aimed at modifying the skills needed for the self-regulation of brain activity [11]. Thus, in an alternative way, the use of NF avoids the potential triggering of negative experiences pertaining to the trauma [3]. Several studies showed that NF could be helpful for patients with PTSD [9]. By allowing us to self-regulate our brain activity [12], neuronal activity and connectivity can be changed [8], indirectly resulting in behavioral changes [5]. Brain activity can be fed back in multiple ways using several neurophysiological methods (e.g., real-time functional magnetic resonance imaging [fMRI], magnetoencephalography [MEG], functional near-infrared spectroscopy [fNIRS], positron emission tomography [PET], and electroencephalogram [EEG]) [13,14]. These feedback techniques allow the participants to monitor, interact with, and manage their mental states [15] and current states of cognition [16] by rewarding desirable patterns of brain activity with visual, auditory [17], or representational forms such as graphs, numbers, video games, and moving objects [18].
PTSD symptoms derive from several areas of the brain. Abnormal contextual processing is often observed in patients with PTSD and it relies on the functional integrity of the medial prefrontal cortex (PFC), hippocampus, and amygdala [19]. A previous meta-analysis found that the medial PFC, including the amygdala and hippocampus, was implicated in PTSD [20]. Maild and colleagues (2009) showed that patients with PTSD had more amygdala activity and less activity in the PFC and hippocampus than healthy individuals [9]. The PFC is important for the regulatory capacity [9] and an increased amygdala activation was seen in all trauma-exposed individuals [6]. Additionally, PTSD symptom reduction was associated with an increase in anterior cingulate cortex (ACC) activation [6]. Kohn et al. (2014) considered the dorsal ACC (dACC) as a core node for emotion regulation [6]. In resting-state studies of PTSD, enhanced slow waves in the left temporal region and decreases in the right parietal cortex were reported [21].
Many different NF protocols and methods exist [4]. NF by both EEG and fMRI represents an emerging adjunctive treatment that allows participants to self-regulate their current neural states [22]. fMRI-NFT is a novel method [23] used to identify the associated brain structures [4] and EEG-NFT is another way to obtain information on the functional neuroanatomy related to clinical symptoms [4]. fMRI-NFT increases or decreases activity in specific cortical areas and has been used to modulate the neural correlates underlying psychopathology [22]. fMRI-based NF training (fMRI-NFT) for PTSD has also been used to modulate amygdala activity [24] and the ACC. In contrast, EEG-NFT is used to regulate more global neuro-signals, indicative of larger-scale brain oscillations [22]. EEG-based NF training (EEG -NFT) for PTSD is mainly used to regulate the power of alpha waves alone or both alpha and theta waves [24]. According to an EEG meta-analysis study, NF treatment and protocol characteristics were different in previous studies: some delivered daily treatment and others less frequent sessions, the duration of treatment varied, and the number of sessions and type of NF differed [8]. However, a previous study [23] reported that the clinical effect of NFT is still missing. Additionally, these two methods differ in NF, but the difference in their effectiveness is still unclear. Therefore, the present study aimed to evaluate the effects of fMRI-NFT and EEG-NFT with PTSD participants compared to sham-NFT and no intervention. The primary outcomes were PTSD symptoms, anxiety, and depression.
The studies were identified through comprehensive searches of PubMed, the Cochrane Library, Web of Science, Science Direct, and ClinicalTrials.gov databases conducted from January 2011 to December 2021. The search string was structured using the PICOS method: P (population) = the patients for PTSD, I (intervention) = neuro-feedback training, C (comparison) = sham, other cognitive training, control group, or no intervention, O (outcome) = PTSD symptoms, anxiety, depression, and S (study design) = randomized controlled trials (RCTs). The search terms were trauma OR (PTSD OR post-traumatic stress disorder) AND (neurofeedback training OR NF-training OR NFT).
We combined the search results from five different databases and deleted duplicate records. Studies were included if they met the following criteria: