Distributed and hierarchical neural encoding of multidimensional biological motion attributes in the human brain.

The human visual system can efficiently extract distinct physical, biological, and social attributes (e.g. facing direction, gender, and emotional state) from biological motion (BM), but how these attributes are encoded in the brain remains largely unknown. In the current study, we used functional magnetic resonance imaging to investigate this issue when participants viewed multidimensional BM stimuli. Using multiple regression representational similarity analysis, we identified distributed brain areas, respectively, related to the processing of facing direction, gender, and emotional state conveyed by BM. These brain areas are governed by a hierarchical structure in which the respective neural encoding of facing direction, gender, and emotional state is modulated by each other in descending order. We further revealed that a portion of the brain areas identified in representational similarity analysis was specific to the neural encoding of each attribute and correlated with the corresponding behavioral results. These findings unravel the brain networks for encoding BM attributes in consideration of their interactions, and highlight that the processing of multidimensional BM attributes is recurrently interactive.

A domain-general frontoparietal network interacts with domain-preferential intermediate pathways to support working memory task.

Working memory (WM) is essential for cognition, but the underlying neural mechanisms remain elusive. From a hierarchical processing perspective, this paper proposed and tested a hypothesis that a domain-general network at the top of the WM hierarchy can interact with distinct domain-preferential intermediate circuits to support WM. Employing a novel N-back task, we first identified the posterior superior temporal gyrus (pSTG), middle temporal area (MT), and postcentral gyrus (PoCG) as intermediate regions for biological motion and shape motion processing, respectively. Using further psychophysiological interaction analyses, we delineated a frontal-parietal network (FPN) as the domain-general network. These results were further verified and extended by a delayed match to sample (DMS) task. Although the WM load-dependent and stimulus-free activations during the DMS delay phase confirm the role of FPN as a domain-general network to maintain information, the stimulus-dependent activations within this network during the DMS encoding phase suggest its involvement in the final stage of the hierarchical processing chains. In contrast, the load-dependent activations of intermediate regions in the N-back task highlight their further roles beyond perception in WM tasks. These results provide empirical evidence for a hierarchical processing model of WM and may have significant implications for WM training.

IHCP: interpretable hepatitis C prediction system based on black-box machine learning models.

BACKGROUND: Hepatitis C is a prevalent disease that poses a high risk to the human liver. Early diagnosis of hepatitis C is crucial for treatment and prognosis. Therefore, developing an effective medical decision system is essential. In recent years, many computational methods have been proposed to identify hepatitis C patients. Although existing hepatitis prediction models have achieved good results in terms of accuracy, most of them are black-box models and cannot gain the trust of doctors and patients in clinical practice. As a result, this study aims to use various Machine Learning (ML) models to predict whether a patient has hepatitis C, while also using explainable models to elucidate the prediction process of the ML models, thus making the prediction process more transparent. RESULT: We conducted a study on the prediction of hepatitis C based on serological testing and provided comprehensive explanations for the prediction process. Throughout the experiment, we modeled the benchmark dataset, and evaluated model performance using fivefold cross-validation and independent testing experiments. After evaluating three types of black-box machine learning models, Random Forest (RF), Support Vector Machine (SVM), and AdaBoost, we adopted Bayesian-optimized RF as the classification algorithm. In terms of model interpretation, in addition to using common SHapley Additive exPlanations (SHAP) to provide global explanations for the model, we also utilized the Local Interpretable Model-Agnostic Explanations with stability (LIME_stabilitly) to provide local explanations for the model. CONCLUSION: Both the fivefold cross-validation and independent testing show that our proposed method significantly outperforms the state-of-the-art method. IHCP maintains excellent model interpretability while obtaining excellent predictive performance. This helps uncover potential predictive patterns of the model and enables clinicians to better understand the model's decision-making process.

Cortical encoding of rhythmic kinematic structures in biological motion.

Biological motion (BM) perception is of great survival value to human beings. The critical characteristics of BM information lie in kinematic cues containing rhythmic structures. However, how rhythmic kinematic structures of BM are dynamically represented in the brain and contribute to visual BM processing remains largely unknown. Here, we probed this issue in three experiments using electroencephalogram (EEG). We found that neural oscillations of observers entrained to the hierarchical kinematic structures of the BM sequences (i.e., step-cycle and gait-cycle for point-light walkers). Notably, only the cortical tracking of the higher-level rhythmic structure (i.e., gait-cycle) exhibited a BM processing specificity, manifested by enhanced neural responses to upright over inverted BM stimuli. This effect could be extended to different motion types and tasks, with its strength positively correlated with the perceptual sensitivity to BM stimuli at the right temporal brain region dedicated to visual BM processing. Modeling results further suggest that the neural encoding of spatiotemporally integrative kinematic cues, in particular the opponent motions of bilateral limbs, drives the selective cortical tracking of BM information. These findings underscore the existence of a cortical mechanism that encodes periodic kinematic features of body movements, which underlies the dynamic construction of visual BM perception.

Agent identity drives adaptive encoding of biological motion into working memory.

To engage in normal social interactions, we have to encode human biological motions (BMs, e.g., walking and jumping), which is one of the most salient and biologically significant types of kinetic information encountered in everyday life, into working memory (WM). Critically, each BM in real life is produced by a distinct person, carrying a dynamic motion signature (i.e., identity). Whether agent identity influences the WM processing of BMs remains unknown. Here, we addressed this question by examining whether memorizing BMs with different identities promoted the WM processing of task-irrelevant clothing colors. Two opposing hypotheses were tested: (a) WM only stores the target action (element-based hypothesis) and (b) WM stores both action and irrelevant clothing color (event-based hypothesis), interpreting each BM as an event. We required participants to memorize actions that either performed by one agent or distinct agents, while ignoring clothing colors. Then we examined whether the irrelevant color was also stored in WM by probing a distracting effect: If the color was extracted into WM, the change of irrelevant color in the probe would lead to a significant distracting effect on action performance. We found that WM encoding of BMs was adaptive: Once the memorized actions had different identities, WM adopted an event-based encoding mode regardless of memory load and probe identity (Experiment 1, different-identity group of Experiment 2, and Experiment 3). However, WM used an element-based encoding mode when memorized-actions shared the same identity (same-identity group of Experiment 2) or were inverted (Experiment 4). Overall, these findings imply that agent identity information has a significant effect on the WM processing of BMs.

Audiovisual correspondence facilitates the visual search for biological motion.

Hearing synchronous sounds may facilitate the visual search for the concurrently changed visual targets. Evidence for this audiovisual attentional facilitation effect mainly comes from studies using artificial stimuli with relatively simple temporal dynamics, indicating a stimulus-driven mechanism whereby synchronous audiovisual cues create a salient object to capture attention. Here, we investigated the crossmodal attentional facilitation effect on biological motion (BM), a natural, biologically significant stimulus with complex and unique dynamic profiles. We found that listening to temporally congruent sounds, compared with incongruent sounds, enhanced the visual search for BM targets. More intriguingly, such a facilitation effect requires the presence of distinctive local motion cues (especially the accelerations in feet movement) independent of the global BM configuration, suggesting a crossmodal mechanism triggered by specific biological features to enhance the salience of BM signals. These findings provide novel insights into how audiovisual integration boosts attention to biologically relevant motion stimuli and extend the function of a proposed life detection system driven by local kinematics of BM to multisensory life motion perception.

Ripples in the pond: Evidence for contagious cooperative role modeling through moral elevation and calling in a small pre-study.

Existing research has identified the importance of role models in the imitation of cooperative behaviors. This Pre-Study attempted to explore the contagion effects of cooperative models. Drawing on goal contagion theory, we proposed that encountering cooperative models could catalyze participants' cooperation when participants joined new groups without role models, and that moral elevation and calling would play a chain-mediating role in this process. To test the hypothesis, we designed a four-person public goods game consisting of two phases in which participants were formed into teams with different people in each phase. We randomly assigned 108 participants to either a consistent contributor (CC) or control condition. The only difference was that participants in the CC condition encountered a cooperative role model (i.e., CC) in the first phase, while those in the control group did not. The results moderately supported all hypotheses. Briefly, our findings provide empirical evidence supporting the two processes of goal contagion theory: when individuals encounter a CC, they first make inferences about the CC's goal, as reflected by moral elevation, and then adopt the model's prosocial goals (i.e., calling), resulting in increased cooperative behaviors in new groups. These findings could extend our understanding of the contagion effect of cooperative modeling, but require high-powered replication studies before such conclusions can be drawn.

Is the social chunking of agent actions in working memory resource-demanding?

Retaining social interactions in working memory (WM) for further social activities is vital for a successful social life. Researchers have noted a social chunking phenomenon in WM: WM involuntarily uses the social interaction cues embedded in the individual actions and chunks them as one unit. Our study is the first to examine whether the social chunking in WM is an automatic process, by asking whether social chunking of agent actions in WM is resource-demanding, a key hallmark of automaticity. We achieved this by probing whether retaining agent interactions in WM as a chunk required more attention than retaining actions without interaction. We employed a WM change-detection task with actions containing social interaction cues as memory stimuli, and required participants only memorizing individual actions. As domain-general attention and object-based attention are suggested playing a key role in retaining chunks in WM, a secondary task was inserted in the WM maintenance phase to consume these two types of attention. We reestablished the fact that the social chunking in WM required no voluntary control (Experiments 1 and 2). Critically, we demonstrated substantial evidence that social chunking in WM did not require extra domain-general attention (Experiment 1) or object-based attention (Experiment 2). These findings imply that the social chunking of agent actions in WM is not resource-demanding, supporting an automatic view of social chunking in WM.

Object-based encoding in visual working memory: A critical revisit.

Visual working memory (VWM) is responsible for the temporal retention and manipulation of visual information. It has been suggested that VWM employs an object-based encoding (OBE) manner to extract highly discriminable information from visual perception: Whenever one feature dimension of the objects is selected for entry into VWM, the other task-irrelevant highly discriminable dimension is also extracted into VWM involuntarily. However, the task-irrelevant feature in OBE studies might reflect a high capacity fragile VWM (FVWM) trace that stores maskable sensory representations. To directly compare the VWM storage hypothesis and the FVWM storage hypothesis, we used a unique characteristic of FVWM that the representations in FVWM could be erased by backward masks presented at the original locations of the memory array. We required participants to memorise the orientations of three coloured bars while ignoring their colours, and presented backward masks during the VWM maintenance interval. In four experiments, we consistently observed that the OBE occurs regardless of the presentation of the backward masks, except when even the task-relevant features in VWM were significantly interrupted by immediate backward masks, suggesting that the task-irrelevant features of objects are stored in VWM rather than in FVWM.

Emotion recognition dysfunction after anesthesia and cardiac surgery.

Cognitive dysfunction after anesthesia and surgery has long been recognized. Recently, researchers provided empirical evidence for social cognition dysfunction (SCD) after anesthesia and surgery. In the present study, we concentrated on the deficits in emotion recognition, one of the most important clinical perspectives in SCD, in patients who underwent cardiac surgery. Biological motion (BM) was considered as the stimulus of interest, and patients' abilities of BM emotion perception and action perception before and after anesthesia and surgery were examined. In total, 60 adult patients (40-72 years old) completed the BM recognition task, which required them to label the types of actions and emotions of perceived BM. The results showed that while action perception remained intact after cardiac surgery, 18.3% of patients exhibited deficits in emotion perception, further confirming the existence of SCD after anesthesia and surgery.

Event-based encoding of biological motion and location in visual working memory.

We make use of discrete yet meaningful events to orient ourselves to the dynamic environment. Among these events, biological motion, referring to the movements of animate entities, is one of the most biologically salient. We usually encounter biological motions of multiple human beings taking place simultaneously at distinct locations. How we encode biological motions into visual working memory (VWM) to form a coherent experience of the external world and guide our social behaviour remains unclear. This study for the first time addressed the VWM encoding mechanism of biological motions and their corresponding locations. We tested an event-based encoding hypothesis for biological motion and location: When one element of an event is required to be memorised, the irrelevant element of an event will also be extracted into VWM. We presented participants with three biological motions at different locations and required them to memorise only the biological motions or their locations while ignoring the other dimension. We examined the event-based encoding by probing a distracting effect: If the event-based encoding took place, the change of irrelevant dimension in the probe would lead to a significant distraction and impair the performance of detecting target dimension. We found significant distracting effects, which lasted for 3 s but vanished at 6 s, regardless of the target dimension (biological motions vs. locations, Experiment 1) and the exposure time of memory array (1 s vs. 3 s, Experiment 2). These results together support an event-based encoding mechanism during VWM encoding of biological motions and their corresponding locations.

Emotional states affect the retention of biological motion in working memory.

Retaining biological motion (BM), or the movements of animate entities, in working memory (WM) is critical to human social life. Moreover, as functioning members of society, we always process BM in a specific emotional state. However, no WM study to date has explored the influence of emotional state on processing BM in WM. As a first step, the current study examined the influence of emotional state on WM capacity for BM. We first induced a specific (positive, negative, or neutral) emotional state and then asked the participants to complete a WM task measuring WM capacity for BM. In Experiment 1, we found that a negative emotional state impaired WM capacity for BM relative to neutral and positive emotional states, with no difference between the latter 2. Experiment 2, adopting µ and α suppression as electroencephalogram (EEG) indices, further confirmed that a negative emotional state reduced the number of BM stimuli retained in WM. Overall, the current study suggests that a negative emotional state has a considerably negative effect on WM capacity for BM. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Social Cognitive Dysfunction in Elderly Patients After Anesthesia and Surgery.

Extensive studies have revealed that cognitive processing was impaired after anesthesia and surgery, particularly for the elderly patients. However, most of the existing studies focused on the general cognitive deficits (e.g., delayed neuro-cognitive recovery and POCD). Although diagnosis of social abilities has been used in various clinical fields, few studies have investigated the potential deficit on social cognition after anesthesia and surgery. The current study examined whether there was any social cognitive dysfunction after anesthesia and surgery. We achieved this by taking biological motion (BM) as the stimuli of interest, the perception of which has been taken as the hallmark of social cognition. The elderly patients (aged ≥ 60 years) were required to judge whether an upright BM stimulus appeared among the dynamic noises to test their social cognition, as well as do a Mini-Mental State Examination to test their general cognition. The two tests were performed at both 1-day before and 7-day after the surgery. Results showed that 31.25% of patients exhibited BM perception deficit after anesthesia and surgery relative to before anesthesia and surgery, implying that social cognitive dysfunction existed. Meanwhile, social cognitive dysfunction was independent from delayed neurocognitive recovery.

Retaining event files in working memory requires extra object-based attention than the constituent elements.

Retaining events containing action-related information in working memory (WM) is vital to daily activities such as action planning and social interaction. During processing of such events, action-related information is bound with other visual elements (e.g., colours) as event files. In this study, we explored whether retaining event files in WM consumes more attention than retaining the constituent elements. Considering that object-based attention underlies the rehearsal of static feature bindings in WM, we hypothesised that object-based attention played a key role in retaining event files in WM. As biological motion (BM) is one of the most frequently observed events in daily life, we employed BM-related event files as the tested stimuli. In separate blocks, we required participants to memorise BM, colours (or locations), or the binding between these elements (i.e., event files). Critically, we added an object-feature report task, which consumed object-based attention, during the WM maintenance phase. We predicted that the added secondary task would lead to larger impairment for BM event files than for the constituent elements. In line with this prediction, Experiments 1 and 2 consistently revealed a selective impairment to BM event files, which could not be attributed to an unbalanced number of elements between memory conditions (Experiment 3), or to the visual processing of a secondary task (Experiment 4). Taken together, these results suggest that object-based attention plays a pivotal role in maintaining event files in WM.

Relation Between Working Memory Capacity of Biological Movements and Fluid Intelligence.

Studies have revealed that there is an independent buffer for holding biological movements (BM) in working memory (WM), and this BM-WM has a unique link to our social ability. However, it remains unknown as to whether the BM-WM also correlates to our cognitive abilities, such as fluid intelligence (Gf). Since BM processing has been considered as a hallmark of social cognition, which distinguishes from canonical cognitive abilities in many ways, it has been hypothesized that only canonical object-WM (e.g., memorizing color patches), but not BM-WM, emerges to have an intimate relation with Gf. We tested this prediction by measuring the relationship between WM capacity of BM and Gf. With two Gf measurements, we consistently found moderate correlations between BM-WM capacity, the score of both Raven's advanced progressive matrix (RAPM), and the Cattell culture fair intelligence test (CCFIT). This result revealed, for the first time, a close relation between WM and Gf with a social stimulus, and challenged the double-dissociation hypothesis for distinct functions of different WM buffers.

Holding Biological Motion in Working Memory: An fMRI Study.

Holding biological motion (BM), the movements of animate entities, in working memory (WM) is important to our daily life activities. However, the neural substrates underlying the WM processing of BM remain largely unknown. Employing the functional magnetic resonance imaging (fMRI) technique, the current study directly investigated this issue. We used point-light BM animations as the tested stimuli, and explored the neural substrates involved in encoding and retaining BM information in WM. Participants were required to remember two or four BM stimuli in a change-detection task. We first defined a set of potential brain regions devoted to the BM processing in WM in one experiment. We then conducted the second fMRI experiment, and performed time-course analysis over the pre-defined regions, which allowed us to differentiate the encoding and maintenance phases of WM. The results showed that a set of brain regions were involved in encoding BM into WM, including the middle frontal gyrus, inferior frontal gyrus, superior parietal lobule, inferior parietal lobule, superior temporal sulcus, fusiform gyrus, and middle occipital gyrus. However, only the middle frontal gyrus, inferior frontal gyrus, superior parietal lobule, and inferior parietal lobule were involved in retaining BM into WM. These results suggest that an overlapped network exists between the WM encoding and maintenance for BM; however, retaining BM in WM predominately relies on the mirror neuron system.

Binding biological motion and visual features in working memory.

Working memory mechanisms for binding have been examined extensively in the last decade, yet few studies have explored bindings relating to human biological motion (BM). Human BM is the most salient and biologically significant kinetic information encountered in everyday life and is stored independently from other visual features (e.g., colors). The current study explored 3 critical issues of BM-related binding in working memory: (a) how many BM binding units can be retained in working memory, (b) whether involuntarily object-based binding occurs during BM binding, and (c) whether the maintenance of BM bindings in working memory requires attention above and beyond that needed to maintain the constituent dimensions. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM and presented the participants colored BM in a change detection task. We found that working memory capacity for BM-color bindings is rather low; only 1 or 2 BM-color bindings could be retained in working memory regardless of the presentation manners (Experiments 1-3). Furthermore, no object-based encoding took place for colored BM stimuli regardless of the processed dimensions (Experiments 4 and 5). Central executive attention contributes to the maintenance of BM-color bindings, yet maintaining BM bindings in working memory did not require more central attention than did maintaining the constituent dimensions in working memory (Experiment 6). Overall, these results suggest that keeping BM bindings in working memory is a fairly resource-demanding process, yet central executive attention does not play a special role in this cross-module binding.