Functional Alignment-Auxiliary Generative Adversarial Network-Based Visual Stimuli Reconstruction via Multi-Subject fMRI.

Functional Magnetic Resonance Imaging (fMRI) provides more precise spatial and temporal information to reconstruct stimulus images than other technologies that can be used to measure the human brain's neural responses. The fMRI scans, however, generally show heterogeneity among different subjects. The majority of the existing methods aim primarily at mining correlations between stimuli and evoked brain activity, disregarding the heterogeneity among subjects. Therefore, this heterogeneity will impair the reliability and applicability of multi-subject decoding results, leading to sub-optimal results. The present paper proposes the functional alignment-auxiliary generative adversarial network (FAA-GAN) as a novel multi-subject approach for visual image reconstruction that employs functional alignment to alleviate the heterogeneity between subjects. Our proposed FAA-GAN includes three key components: 1) a generative adversarial network (GAN) module for reconstructing visual stimuli, which consists of a visual image encoder as the generator that uses a nonlinear network to convert stimuli images into an implicit representation and a discriminator that generates the images comparable to the original images in detail; 2) a multi-subject functional alignment module, which is used to precisely align the individual fMRI response space of each subject in a common space to reduce the heterogeneity among different subjects; and 3) a cross-modal hashing retrieval module used for similarity retrieval of two modalities of data, i.e., the visual images and the evoked brain responses. Experiments on real-world datasets show that our FAA-GAN method does better than other state-of-the-art deep learning-based reconstruction methods with fMRI.

A comprehensive review on motion trajectory reconstruction for EEG-based brain-computer interface.

The advance in neuroscience and computer technology over the past decades have made brain-computer interface (BCI) a most promising area of neurorehabilitation and neurophysiology research. Limb motion decoding has gradually become a hot topic in the field of BCI. Decoding neural activity related to limb movement trajectory is considered to be of great help to the development of assistive and rehabilitation strategies for motor-impaired users. Although a variety of decoding methods have been proposed for limb trajectory reconstruction, there does not yet exist a review that covers the performance evaluation of these decoding methods. To alleviate this vacancy, in this paper, we evaluate EEG-based limb trajectory decoding methods regarding their advantages and disadvantages from a variety of perspectives. Specifically, we first introduce the differences in motor execution and motor imagery in limb trajectory reconstruction with different spaces (2D and 3D). Then, we discuss the limb motion trajectory reconstruction methods including experiment paradigm, EEG pre-processing, feature extraction and selection, decoding methods, and result evaluation. Finally, we expound on the open problem and future outlooks.

Deep Representational Similarity Learning for Analyzing Neural Signatures in Task-based fMRI Dataset.

Similarity analysis is one of the crucial steps in most fMRI studies. Representational Similarity Analysis (RSA) can measure similarities of neural signatures generated by different cognitive states. This paper develops Deep Representational Similarity Learning (DRSL), a deep extension of RSA that is appropriate for analyzing similarities between various cognitive tasks in fMRI datasets with a large number of subjects, and high-dimensionality - such as whole-brain images. Unlike the previous methods, DRSL is not limited by a linear transformation or a restricted fixed nonlinear kernel function - such as Gaussian kernel. DRSL utilizes a multi-layer neural network for mapping neural responses to linear space, where this network can implement a customized nonlinear transformation for each subject separately. Furthermore, utilizing a gradient-based optimization in DRSL can significantly reduce runtime of analysis on large datasets because it uses a batch of samples in each iteration rather than all neural responses to find an optimal solution. Empirical studies on multi-subject fMRI datasets with various tasks - including visual stimuli, decision making, flavor, and working memory - confirm that the proposed method achieves superior performance to other state-of-the-art RSA algorithms.

Predicting pediatric anxiety from the temporal pole using neural responses to emotional faces.

A prominent cognitive aspect of anxiety is dysregulation of emotional interpretation of facial expressions, associated with neural activity from the amygdala and prefrontal cortex. We report machine learning analysis of fMRI results supporting a key role for a third area, the temporal pole (TP) for childhood anxiety in this context. This finding is based on differential fMRI responses to emotional faces (angry versus fearful faces) in children with one or more of generalized anxiety, separation anxiety, and social phobia (n = 22) compared with matched controls (n = 23). In our machine learning (Adaptive Boosting) model, the right TP distinguished anxious from control children (accuracy = 81%). Involvement of the TP as significant for neurocognitive aspects of pediatric anxiety is a novel finding worthy of further investigation.

Detecting Presence of PTSD Using Sentiment Analysis From Text Data.

Rates of Post-traumatic stress disorder (PTSD) have risen significantly due to the COVID-19 pandemic. Telehealth has emerged as a means to monitor symptoms for such disorders. This is partly due to isolation or inaccessibility of therapeutic intervention caused from the pandemic. Additional screening tools may be needed to augment identification and diagnosis of PTSD through a virtual medium. Sentiment analysis refers to the use of natural language processing (NLP) to extract emotional content from text information. In our study, we train a machine learning (ML) model on text data, which is part of the Audio/Visual Emotion Challenge and Workshop (AVEC-19) corpus, to identify individuals with PTSD using sentiment analysis from semi-structured interviews. Our sample size included 188 individuals without PTSD, and 87 with PTSD. The interview was conducted by an artificial character (Ellie) over a video-conference call. Our model was able to achieve a balanced accuracy of 80.4% on a held out dataset used from the AVEC-19 challenge. Additionally, we implemented various partitioning techniques to determine if our model was generalizable enough. This shows that learned models can use sentiment analysis of speech to identify the presence of PTSD, even through a virtual medium. This can serve as an important, accessible and inexpensive tool to detect mental health abnormalities during the COVID-19 pandemic.

CACNB2 rs11013860 polymorphism correlates of prefrontal cortex thickness in bipolar patients with first-episode mania.

BACKGROUND: The ß2 subunit of the voltage-gated l-type calcium channel gene(CACNB2) rs11013860 polymorphism is a putative genetic susceptibility marker for bipolar disorder (BD). However, the neural effects of CACNB2 rs11013860 in BD are largely unknown. METHODS: Forty-six bipolar patients with first-episode mania and eighty-three healthy controls (HC) were genotyped for CACNB2 rs11013860 and were scanned with a 3.0 Tesla structural magnetic resonance imaging system to measure cortical thickness of prefrontal cortex (PFC) components (superior frontal cortex, orbitofrontal cortex, middle and inferior frontal gyri). RESULTS: Cortical thickness was thinner in patients on all PFC measurements compared to HC (p < 0.050). Moreover, we found a significant interaction between CACNB2 genotype and diagnosis for the right superior frontal cortical thickness (F = 8.190, p = 0.040). Bonferroni corrected post-hoc tests revealed that, in CACNB2 A-allele carriers, patients displayed thinner superior frontal thickness compared to HC (p < 0.001). In patients, CACNB2 A-allele carriers also exhibited reduced superior frontal thickness compared to CACNB2 CC-allele carriers (p = 0.016). LIMITATIONS: Lithium treatment may influence our results, and the sample size in our study is relatively small. CONCLUSIONS: Our results suggest that the CACNB2 rs11013860 might impact PFC thickness in patients with first-episode mania. These findings provide evidence to support CACNB2 rs11013860 involvement in the emotion-processing neural circuitry abnormality in the early stage of BD, which will ultimately contribute to revealing the link between the variation in calcium channel genes and the neuropathological mechanism of BD.

Multi-Objective Cognitive Model: a Supervised Approach for Multi-subject fMRI Analysis.

In order to decode human brain, Multivariate Pattern (MVP) classification generates cognitive models by using functional Magnetic Resonance Imaging (fMRI) datasets. As a standard pipeline in the MVP analysis, brain patterns in multi-subject fMRI dataset must be mapped to a shared space and then a classification model is generated by employing the mapped patterns. However, the MVP models may not provide stable performance on a new fMRI dataset because the standard pipeline uses disjoint steps for generating these models. Indeed, each step in the pipeline includes an objective function with independent optimization approach, where the best solution of each step may not be optimum for the next steps. For tackling the mentioned issue, this paper introduces Multi-Objective Cognitive Model (MOCM) that utilizes an integrated objective function for MVP analysis rather than just using those disjoint steps. For solving the integrated problem, we proposed a customized multi-objective optimization approach, where all possible solutions are firstly generated, and then our method ranks and selects the robust solutions as the final results. Empirical studies confirm that the proposed method can generate superior performance in comparison with other techniques.

WoCE: A framework for Clustering Ensemble by Exploiting the Wisdom of Crowds Theory.

The wisdom of crowds (WOCs), as a theory in the social science, gets a new paradigm in computer science. The WOC theory explains that the aggregate decision made by a group is often better than those of its individual members if specific conditions are satisfied. This paper presents a novel framework for unsupervised and semisupervised cluster ensemble by exploiting the WOC theory. We employ four conditions in the WOC theory, i.e., diversity, independency, decentralization, and aggregation, to guide both constructing of individual clustering results and final combination for clustering ensemble. First, independency criterion, as a novel mapping system on the raw data set, removes the correlation between features on our proposed method. Then, decentralization as a novel mechanism generates high quality individual clustering results. Next, uniformity as a new diversity metric evaluates the generated clustering results. Further, weighted evidence accumulation clustering method is proposed for the final aggregation without using thresholding procedure. Experimental study on varied data sets demonstrates that the proposed approach achieves superior performance to state-of-the-art methods.