Semantic processing in comatose patients with intact temporal lobes as reflected by the N400 event-related potential

Brain-computer interfaces and human factors: the role of language and cultural differences-Still a missing gap?

Brain-computer interfaces (BCIs) aim at the non-invasive investigation of brain activity for supporting communication and interaction of the users with their environment by means of brain-machine assisted technologies. Despite technological progress and promising research aimed at understanding the influence of human factors on BCI effectiveness, some topics still remain unexplored. The aim of this article is to discuss why it is important to consider the language of the user, its embodied grounding in perception, action and emotions, and its interaction with cultural differences in information processing in future BCI research. Based on evidence from recent studies, it is proposed that detection of language abilities and language training are two main topics of enquiry of future BCI studies to extend communication among vulnerable and healthy BCI users from bench to bedside and real world applications. In addition, cultural differences shape perception, actions, cognition, language and emotions subjectively, behaviorally as well as neuronally. Therefore, BCI applications should consider cultural differences in information processing to develop culture- and language-sensitive BCI applications for different user groups and BCIs, and investigate the linguistic and cultural contexts in which the BCI will be used.

Aloud real- time reading of intensive care unit diaries: A feasibility study

OBJECTIVES

Memories of frightening/delusional intensive care unit experiences are a major risk factor for subsequent psychiatric morbidity of critical illness survivors; factual memories are protective. Systematically providing factual information during initial memory consolidation could mitigate the emotional character of the formed memories. We explored feasibility and obtained stakeholder feedback of a novel approach to intensive care unit diaries whereby entries were read aloud to the patients right after they were written to facilitate systematic real time orientation and formation of factual memories.

RESEARCH METHODOLOGY

Prospective interventional pilot study involving reading diary entries aloud. We have also interviewed involved stakeholders for feedback and collected exploratory data on psychiatric symptoms from patients right after the intensive care stay.

SETTING

Various intensive care units in a single academic center.

MAIN OUTCOME MEASURES

Feasibility was defined as intervention delivery on ≥80% of days following patient recruitment. Content analysis was performed on stakeholder interview responses. Questionnaire data were compared for patients who received real-time reading to the historical cohort who did not.

RESULTS

Overall, 57% (17 of 30) of patients achieved the set feasibility threshold. Following protocol adjustment, we achieved 86% feasibility in the last subset of patients. Patients reported the intervention as comforting and appreciated the reorientation aspect. Nurses overwhelmingly liked the idea; most common concern was not knowing what to write. Some therapists were unsure whether reading entries aloud might overwhelm the patients. There were no significant differences in psychiatric symptoms when compared to the historic cohort.

CONCLUSION

We encountered several implementation obstacles; once these were addressed, we achieved set feasibility target for the last group of patients. Reading diary entries aloud was welcomed by stakeholders. Designing a trial to assess efficacy of the intervention on psychiatric outcomes appears warranted.

IMPLICATIONS FOR CLINICAL PRACTICE

There is no recommendation to change current practice as benefits of the intervention are unproven.

Connecting and considering: Electrophysiology provides insights into comprehension

The ability to rapidly and systematically access knowledge stored in long-term memory in response to incoming sensory information-that is, to derive meaning from the world-lies at the core of human cognition. Research using methods that can precisely track brain activity over time has begun to reveal the multiple cognitive and neural mechanisms that make this possible. In this article, I delineate how a process of connecting affords an effortless, continuous infusion of meaning into human perception. In a relatively invariant time window, uncovered through studies using the N400 component of the event-related potential, incoming sensory information naturally induces a graded landscape of activation across long-term semantic memory, creating what might be called "proto-concepts". Connecting can be (but is not always) followed by a process of further considering those activations, wherein a set of more attentionally demanding "active comprehension" mechanisms mediate the selection, augmentation, and transformation of the initial semantic representations. The result is a limited set of more stable bindings that can be arranged in time or space, revised as needed, and brought to awareness. With this research, we are coming closer to understanding how the human brain is able to fluidly link sensation to experience, to appreciate language sequences and event structures, and, sometimes, to even predict what might be coming up next.

A pilot study of trained ICU doulas providing early psychological support to critically ill patients

Background

Over a third of critical illness survivors suffer from mental health problems following hospitalization. Memories of delusional experiences are a major risk factor. In this project, ICU doulas delivered a unique positive suggestion intervention targeting the vulnerable time period during critical illness when these memories are formed.

Methods

Adult critically ill patients were recruited for this single-arm, prospective pilot study. These ICU patients received a positive suggestion intervention daily during their ICU stay in parallel with their medical treatment. The intervention was designed to be delivered over a minimum of two sessions. Feasibility was defined as intervention delivery on ≥ 70% of ICU days after patient enrollment. As a secondary analysis, psychometric questionnaires were compared to those of a historic control cohort of patients receiving standard care in the ICU using adjusted linear regression models.

Results

Of the 97 patients who received the intervention and were alive at the end of their ICU course, 54 were excluded from analyses mostly for having received only one session because of a short ICU length of stay of < 2 days, transitioning to comfort care or not wanting to answer the study questionnaires. Forty-three patients who completed 2 or more sessions of the positive therapeutic suggestion intervention provided by two trained ICU doulas received it for a median of 4 days (IQR 3, 5), with each session lasting for a median of 20 min (IQR 14, 25). The intervention was delivered on 71% of days, meeting our pre-determined feasibility goal. Compared to historical controls (N = 299), patients receiving the intervention had higher severity of illness and longer length of stay. When adjusted for baseline differences, patients both with and without mechanical ventilation who received the intervention scored lower on the Hospital Anxiety and Depression Scale (HADS)—Depression subscale. The intervention was also associated with reduced HADS-Anxiety subscale among ventilated patients.

Conclusions

Positive therapeutic suggestion delivered by ICU doulas is feasible in the ICU setting. A randomized trial is warranted to better delineate the role that positive suggestion and ICU doulas may play in ongoing interprofessional efforts to humanize critical care medicine.

The study was registered on clinicaltrials.gov (NCT03736954) on 03/14/2018 prior to the first patient enrollment https://clinicaltrials.gov/ct2/show/NCT03736954?cond=ICU+Doulas+Providing+Psychological+Support&draw=2&rank=1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03856-3.

System of Psychological Support Based on Positive Suggestions to the Critically Ill Using ICU Doulas

Background:

Surviving critical illness often creates a lasting psychological impact, including depression, anxiety, and post-traumatic stress. Memories of frightening and delusional experiences are the largest potentially modifiable risk factor, but currently, there is no proven intervention to improve these inciting factors. Psychological support based on positive suggestion is a psychotherapeutic approach that can be provided even to patients in altered cognitive states and is therefore a viable psychotherapy intervention throughout the ICU stay. Traditional ICU care team members have limited time and training to provide such psychological support to patients. Doulas are trained supportive companions who have been effectively used to provide patient advocacy and emotional support in other clinical settings and may address this need. Our aim was to train and implement a psychological support based on positive suggestion program for the critically ill using doulas, and measure acceptance of this intervention through stakeholder feedback.

Methods:

Doula training included three objectives: an introduction to ICU practice structure and policies; education about fundamental aspects of critical care conditions and procedures; and didactic and hands-on learning experiences in effective use of psychological support based on positive suggestion in the critically ill. Doulas were evaluated at the end of their training and during subsequent clinical activities using competency-based assessments as well as through survey-based questions and interviews with key stakeholders.

Results:

The ICU doulas performed psychological support based on positive suggestion on 43 critically ill patients in the ICU setting. Stakeholder feedback from nurses, patients, and patient families was positive. The majority (28/32) of surveyed bedside ICU nurses reported that the doulas’ involvement was helpful for both patients and nurses alike. All interviewed family members offered positive comments about the ICU doula presence and of the 40 patients who recalled the intervention 37 found it comforting.

Conclusions:

Our program successfully trained two doulas to work effectively in the ICU setting performing patient-centered psychological support based on positive suggestion interventions. Their training improved their skill sets and was reported as beneficial by patients, families, and critical care nursing. This training program offers a proof of concept that could be applied in other medical centers, bringing doulas more commonly into the ICU practice to help humanize the experience for patients, families, and medical teams.

Stress and Fear: Clinical Implications for Providers and Patients (in the Time of COVID-19 and Beyond)

In light of the coronavirus disease 2019 pandemic, we explore the role of stress, fear, and the impact of positive and negative emotions on health and disease. We then introduce strategies to help mitigate stress within the health care team, and provide a rationale for their efficacy. Additionally, we identify strategies to optimize patient care and explain their heightened importance in today's environment.

Event-related potentials reflect prediction errors and pop-out during comprehension of degraded speech

Comprehension of degraded speech requires higher-order expectations informed by prior knowledge. Accurate top-down expectations of incoming degraded speech cause a subjective semantic 'pop-out' or conscious breakthrough experience. Indeed, the same stimulus can be perceived as meaningless when no expectations are made in advance. We investigated the event-related potential (ERP) correlates of these top-down expectations, their error signals and the subjective pop-out experience in healthy participants. We manipulated expectations in a word-pair priming degraded (noise-vocoded) speech task and investigated the role of top-down expectation with a between-groups attention manipulation. Consistent with the role of expectations in comprehension, repetition priming significantly enhanced perceptual intelligibility of the noise-vocoded degraded targets for attentive participants. An early ERP was larger for mismatched (i.e. unexpected) targets than matched targets, indicative of an initial error signal not reliant on top-down expectations. Subsequently, a P3a-like ERP was larger to matched targets than mismatched targets only for attending participants-i.e. a pop-out effect-while a later ERP was larger for mismatched targets and did not significantly interact with attention. Rather than relying on complex post hoc interactions between prediction error and precision to explain this apredictive pattern, we consider our data to be consistent with prediction error minimization accounts for early stages of processing followed by Global Neuronal Workspace-like breakthrough and processing in service of task goals.

Feasibility of a Behavioral Intervention to Reduce Psychological Distress in Mechanically Ventilated Patients

Many survivors of acute respiratory failure suffer from mood disorders following discharge from the hospital. We investigated the feasibility of intensivists delivering psychological support based on positive suggestion (PSBPS) to 20 intubated patients to reduce their psychological distress. Thirteen patients completed follow-up surveys. Of those, 9 remembered the intensive care unit physician talking to them, and 7 described it as comforting. Five patients (38%) met criteria for anxiety, depression, and acute stress. In comparison to historical controls, intervention may be associated with lower estimated odds of anxiety. PSBPS can be performed with patients in parallel with medical treatment to potentially reduce psychological morbidity and to humanize critical care. A larger randomized study is warranted to assess the efficacy of PSBPS.

Electrophysiological and Neuroimaging Studies - During Resting State and Sensory Stimulation in Disorders of Consciousness: A Review

A severe brain injury may lead to a disorder of consciousness (DOC) such as coma, vegetative state (VS), minimally conscious state (MCS) or locked-in syndrome (LIS). Till date, the diagnosis of DOC relies only on clinical evaluation or subjective scoring systems such as Glasgow coma scale, which fails to detect subtle changes and thereby results in diagnostic errors. The high rate of misdiagnosis and inability to predict the recovery of consciousness for DOC patients have created a huge research interest in the assessment of consciousness. Researchers have explored the use of various stimulation and neuroimaging techniques to improve the diagnosis. In this article, we present the important findings of resting-state as well as sensory stimulation methods and highlight the stimuli proven to be successful in the assessment of consciousness. Primarily, we review the literature based on (a) application/non-use of stimuli (i.e., sensory stimulation/resting state-based), (b) type of stimulation used (i.e., auditory, visual, tactile, olfactory, or mental-imagery), (c) electrophysiological signal used (EEG/ERP, fMRI, PET, EMG, SCL, or ECG). Among the sensory stimulation methods, auditory stimulation has been extensively used, since it is easier to conduct for these patients. Olfactory and tactile stimulation have been less explored and need further research. Emotionally charged stimuli such as subject’s own name or narratives in a familiar voice or subject’s own face/family pictures or music result in stronger responses than neutral stimuli. Studies based on resting state analysis have employed measures like complexity, power spectral features, entropy and functional connectivity patterns to distinguish between the VS and MCS patients. Resting-state EEG and fMRI are the state-of-the-art techniques and have a huge potential in predicting the recovery of coma patients. Further, EMG and mental-imagery based studies attempt to obtain volitional responses from the VS patients and thus could detect their command-following capability. This may provide an effective means to communicate with these patients. Recent studies have employed fMRI and PET to understand the brain-activation patterns corresponding to the mental imagery. This review promotes our knowledge about the techniques used for the diagnosis of patients with DOC and attempts to provide ideas for future research.

Development of a point of care system for automated coma prognosis: a prospective cohort study protocol

INTRODUCTION

Coma is a deep state of unconsciousness that can be caused by a variety of clinical conditions. Traditional tests for coma outcome prediction are based mainly on a set of clinical observations. Recently, certain event-related potentials (ERPs), which are transient electroencephalogram (EEG) responses to auditory, visual or tactile stimuli, have been introduced as useful predictors of a positive coma outcome (ie, emergence). However, such tests require the skills of clinical neurophysiologists, who are not commonly available in many clinical settings. Additionally, none of the current standard clinical approaches have sufficient predictive accuracies to provide definitive prognoses.

OBJECTIVE

The objective of this study is to develop improved machine learning procedures based on EEG/ERP for determining emergence from coma.

METHODS AND ANALYSIS

Data will be collected from 50 participants in coma. EEG/ERP data will be recorded for 24 consecutive hours at a maximum of five time points spanning 30 days from the date of recruitment to track participants' progression. The study employs paradigms designed to elicit brainstem potentials, middle-latency responses, N100, mismatch negativity, P300 and N400. In the case of patient emergence, data are recorded on that occasion to form an additional basis for comparison. A relevant data set will be developed from the testing of 20 healthy controls, each spanning a 15-hour recording period in order to formulate a baseline. Collected data will be used to develop an automated procedure for analysis and detection of various ERP components that are salient to prognosis. Salient features extracted from the ERP and resting-state EEG will be identified and combined to give an accurate indicator of prognosis.

ETHICS AND DISSEMINATION

This study is approved by the Hamilton Integrated Research Ethics Board (project number 4840). Results will be disseminated through peer-reviewed journal articles and presentations at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT03826407.

Perspectives of physicians and nurses on identifying and treating psychological distress of the critically ill

PURPOSE

Survivors of critical illness are frequently unable to return to their premorbid level of psychocognitive functioning following discharge. Therefore, we aimed to evaluate the burden of psychological trauma experienced by patients in the intensive care unit (ICU) as perceived by clinicians to assess factors that can impede its recognition and treatment in the ICU.

MATERIALS AND METHODS

Two distinct role-specific Web-based surveys were administered to critical care physicians and nurses in medical and surgical ICUs of 2 academic medical centers. Responses were analyzed in the domains of psychological trauma, exacerbating/mitigating factors, and provider-patient communication.

RESULTS

A survey was completed by 43 physicians and 55 nurses with a response rate of 62% and 37%, respectively. Among physicians, 65% consistently consider the psychological state of the patient in decision making; 77% think it is important to introduce a system to document psychological state of ICU patients; 56% would like to have more time to communicate with patients; 77% consistently spend extra time at bedside besides rounds and often hold patient's hand/reassure them. Notably, for the question about the average level of psychological stress experienced by a patient in the ICU (with 0=no stress and 100=worst stress imaginable) during initial treatment stage and by the end of the ICU stay, median assessment by both physicians and nurses was 80 for the initial stress level and 68 for the stress level by the end of the ICU stay. Among nurses, 69% always try to minimize noise and 73% actively promote patient's rest. Physicians and nurses provided multiple specific suggestions for improving ICU environment and communication.

CONCLUSIONS

Both physicians and nurses acknowledge that they perceive that critically ill patients experience a high level of psychological stress that persists throughout their period of illness. Improved understanding of this phenomenon is needed to design effective therapeutic interventions. Although the lack of time is identified as significant barrier to ameliorating patient's psychological stress, the majority of clinicians indicate that they attempt to provide interventions to achieve this goal.

The relationship between brain reaction and English reading tests for non-native English speakers

This research analyzed the brain activity of non-native English speakers while engaged in English reading tests. The brain wave event-related potentials (ERPs) of participants were used to analyze the difference between making correct and incorrect choices on English reading test items. Three English reading tests of differing levels were designed and 20 participants, 10 males and 10 females whose ages ranged from 20 to 24, voluntarily participated in the experiment. Experimental results were analyzed by performing independent t-tests on the ERPs of participants for gender, difficulty level, and correct versus wrong options. Participants who chose incorrect options elicited a larger N600, verifying results found in the literature. Another interesting result was found: For incorrectly answered items, different areas of brain showing a significant difference in ERPs between the chosen and non-chosen options corresponded to gender differences; for males, this area was located in the right hemisphere whereas for females, it was located in the left. Experimental results imply that non-native English speaking males and females employ different areas of the brain to comprehend the meaning of difficult items.

Promoting the use of personally relevant stimuli for investigating patients with disorders of consciousness

Sensory stimuli are used to evaluate and to restore cognitive functions and consciousness in patients with a disorder of consciousness (DOC) following a severe brain injury. Although sophisticated protocols can help assessing higher order cognitive functions and awareness, one major drawback is their lack of sensitivity. The aim of the present review is to show that stimulus selection is crucial for an accurate evaluation of the state of patients with disorders of consciousness as it determines the levels of processing that the patient can have with stimulation from his/her environment. The probability to observe a behavioral response or a cerebral response is increased when her/his personal history and/or her/his personal preferences are taken into account. We show that personally relevant stimuli (i.e., with emotional, autobiographical, or self-related characteristics) are associated with clearer signs of perception than are irrelevant stimuli in patients with DOC. Among personally relevant stimuli, music appears to be a promising clinical tool as it boosts perception and cognition in patients with DOC and could also serve as a prognostic tool. We suggest that the effect of music on cerebral processes in patients might reflect the music's capacity to act both on the external and internal neural networks supporting consciousness.

The reliability of the N400 in single subjects: implications for patients with disorders of consciousness

Functional neuroimaging assessments of residual cognitive capacities, including those that support language, can improve diagnostic and prognostic accuracy in patients with disorders of consciousness. Due to the portability and relative inexpensiveness of electroencephalography, the N400 event-related potential component has been proposed as a clinically valid means to identify preserved linguistic function in non-communicative patients. Across three experiments, we show that changes in both stimuli and task demands significantly influence the probability of detecting statistically significant N400 effects - that is, the difference in N400 amplitudes caused by the experimental manipulation. In terms of task demands, passively heard linguistic stimuli were significantly less likely to elicit N400 effects than task-relevant stimuli. Due to the inability of the majority of patients with disorders of consciousness to follow task commands, the insensitivity of passive listening would impede the identification of residual language abilities even when such abilities exist. In terms of stimuli, passively heard normatively associated word pairs produced the highest detection rate of N400 effects (50% of the participants), compared with semantically-similar word pairs (0%) and high-cloze sentences (17%). This result is consistent with a prediction error account of N400 magnitude, with highly predictable targets leading to smaller N400 waves, and therefore larger N400 effects. Overall, our data indicate that non-repeating normatively associated word pairs provide the highest probability of detecting single-subject N400s during passive listening, and may thereby provide a clinically viable means of assessing residual linguistic function. We also show that more liberal analyses may further increase the detection-rate, but at the potential cost of increased false alarms.

Robust discrimination between EEG responses to categories of environmental sounds in early coma

Humans can recognize categories of environmental sounds, including vocalizations produced by humans and animals and the sounds of man-made objects. Most neuroimaging investigations of environmental sound discrimination have studied subjects while consciously perceiving and often explicitly recognizing the stimuli. Consequently, it remains unclear to what extent auditory object processing occurs independently of task demands and consciousness. Studies in animal models have shown that environmental sound discrimination at a neural level persists even in anesthetized preparations, whereas data from anesthetized humans has thus far provided null results. Here, we studied comatose patients as a model of environmental sound discrimination capacities during unconsciousness. We included 19 comatose patients treated with therapeutic hypothermia (TH) during the first 2 days of coma, while recording nineteen-channel electroencephalography (EEG). At the level of each individual patient, we applied a decoding algorithm to quantify the differential EEG responses to human vs. animal vocalizations as well as to sounds of living vocalizations vs. man-made objects. Discrimination between vocalization types was accurate in 11 patients and discrimination between sounds from living and man-made sources in 10 patients. At the group level, the results were significant only for the comparison between vocalization types. These results lay the groundwork for disentangling truly preferential activations in response to auditory categories, and the contribution of awareness to auditory category discrimination.

N400 predicts recovery from disorders of consciousness

OBJECTIVE

Patients with the unresponsive wakefulness syndrome (UWS; formerly vegetative state) or in a minimally conscious state (MCS) open their eyes spontaneously but show no (UWS) or only marginal (MCS) signs of awareness. Because these states can become permanent, residual information processing capacities need to be determined, and reliable outcome predictors need to be found. We assessed higher-order cortical information processing in UWS or MCS in a large group of patients using electroencephalographic event-related potentials (ERPs) and determined their long-term prognostic value for recovery.

METHODS

Cognitive ERPs elicited by sound (P300) and speech (N400) were used to assess information processing in 92 behaviorally unresponsive patients diagnosed as in the state of either UWS (n=53) or MCS (n=39). ERPs were assessed with a clinical standard evaluation method and a computerized method, the t-continuous wavelet transform. The patients' clinical outcome was followed up between 2 and 14 years after discharge from the rehabilitation center.

RESULTS

Within the first year of the disease, many patients showed an intact P300 and several also an N400, indicating considerable residual information processing. At clinical follow-up, about 25% of the patients recovered and regained communicative capabilities. A highly significant relationship between N400, but not P300, presence and subsequent recovery was found.

INTERPRETATION

Results specify cognitive capabilities in disorders of consciousness, and determine their prognostic value. Specifically the N400 ERP is suggested as an important tool to assess information-processing capacities that can predict the likelihood of recovery of patients in UWS or MCS.

Attention and semantic processing during speech: an fMRI study

This fMRI study was conducted to investigate whether language semantics is processed even when attention is not explicitly directed to word meanings. In the "unattended" condition, the subjects performed a visual detection task while hearing semantically related and unrelated word pairs. In the "phoneme" condition, the subjects made phoneme judgements between prime and target words, and in the "word" condition, they indicated whether the words in each word pair were semantically related or unrelated. In the word condition, stronger activity was obtained for unrelated than related words in the superior temporal gyrus/sulcus (STG/STS), lingual/fusiform gyri and cuneus, whereas in the phoneme condition no such effect was observed. However, during the unattended condition, stronger activity was found in the right STG. Our results suggest that both semantic judgement of word pairs and their passive hearing activate the same neural networks but this activation is more restricted in the passive hearing.