Demographic Features, Physical Examination Findings, and Medication Use in Hospitalized, Delirious Patients With and Without COVID-19 Infection: A Retrospective Study.

BACKGROUND: Delirium is common in the setting of infection with severe acute respiratory syndrome coronavirus 2. Anecdotal evidence and case reports suggest that patients with delirium in the setting of Coronavirus 2019 (COVID-19) may exhibit specific features, including increased tone, abulia, and alogia. OBJECTIVE: To determine whether differences exist in sociodemographic and medical characteristics, physical examination findings, and medication use in delirious patients with and without COVID-19 infection referred for psychiatric consultation. METHODS: We undertook an exploratory, retrospective chart review of 486 patients seen by the psychiatry consultation service at a tertiary care hospital from March 10 to May 15, 2020. Delirious patients were diagnosed via clinical examination by a psychiatric consultant, and these patients were stratified by COVID-19 infection status. The strata were described and compared using bivariate analyses across sociodemographic, historical, objective, and treatment-related variables. RESULTS: A total of 109 patients were diagnosed with delirium during the study period. Thirty-six were COVID-19+. Median age was 63 years and did not differ between groups. COVID-19+ patients with delirium were more likely to present from nursing facilities (39% vs 11%; Fisher's exact test; P = 0.001) and have a history of schizophrenia (11% vs 0%; Fisher's exact test; P = 0.011). Myoclonus (28% vs 4%; P = 0.002), hypertonia (36% vs 10%; P = 0.003), withdrawal (36% vs 15%; P = 0.011), akinesia (19% vs 6%; P = 0.034), abulia (19% vs 3%; P = 0.004), and alogia (25% vs 8%; P = 0.012) were more common in COVID-19+ patients. COVID-19+ delirious patients were significantly more likely to have received ketamine (28% vs 7%; P = 0.006), alpha-adrenergic agents besides dexmedetomidine (36% vs 14%; P = 0.014), and enteral antipsychotics (92% vs 66%; P = 0.007) at some point. CONCLUSIONS: Patients with COVID-19 delirium referred for psychiatric consultation are more likely to reside in nursing facilities and have a history of schizophrenia than delirious patients without COVID-19. Patients with delirium in the setting of COVID-19 may exhibit features consistent with akinetic mutism. Psychiatrists must assess for such features, as they may influence management choices and the risk of side effects with agents commonly used in the setting of delirium.

Absence of conditioned responding in humans: A bad measure or individual differences?

Skin conductance response (SCR) is often used as an index of conditioned fear. SCR has been shown to be highly variable, and absence of SC reactivity is sometimes used as criteria for excluding data. It is, however, possible that low or no SC reactivity is the result of a distinct biological signature that underlies individual differences in SCR reactivity. This study examined neural correlates associated with the near absence of SCR conditionability. Archival data from 109 healthy adults aged 18-60 years were pooled. All individuals had participated in a fear conditioning protocol in a fMRI environment, during which two cues were partially reinforced (CS+) with a shock and a third cue was not (CS-). Using SCR to the conditioned stimuli and differential SCR (CS+ minus CS-), we created two groups of 30 individuals: low conditioners (defined as those showing the smallest SCR to the CS+ and smallest differential SCR) and high conditioners (defined as those showing the largest SCR to the CS+ and largest differential SCR). Our analyses showed differences in patterns of brain activations between these two groups during conditioning in the following regions: dorsal anterior cingulate cortex, amygdala, subgenual anterior cingulate cortex, and insular cortex. Our findings suggest that low or absent SCR conditionability is associated with hypoactivation of brain regions involved in fear learning and expression. This highlights the need to be cautious when excluding SCR nonconditioners and to consider the potential implications of such exclusion when interpreting the findings from studies of conditioned fear.

Reprint of: "Demographic factors predict magnitude of conditioned fear".

There is substantial variability across individuals in the magnitudes of their skin conductance (SC) responses during the acquisition and extinction of conditioned fear. To manage this variability, subjects may be matched for demographic variables, such as age, gender and education. However, limited data exist addressing how much variability in conditioned SC responses is actually explained by these variables. The present study assessed the influence of age, gender and education on the SC responses of 222 subjects who underwent the same differential conditioning paradigm. The demographic variables were found to predict a small but significant amount of variability in conditioned responding during fear acquisition, but not fear extinction learning or extinction recall. A larger differential change in SC during acquisition was associated with more education. Older participants and women showed smaller differential SC during acquisition. Our findings support the need to consider age, gender and education when studying fear acquisition but not necessarily when examining fear extinction learning and recall. Variability in demographic factors across studies may partially explain the difficulty in reproducing some SC findings.

Demographic factors predict magnitude of conditioned fear.

There is substantial variability across individuals in the magnitudes of their skin conductance (SC) responses during the acquisition and extinction of conditioned fear. To manage this variability, subjects may be matched for demographic variables, such as age, gender and education. However, limited data exist addressing how much variability in conditioned SC responses is actually explained by these variables. The present study assessed the influence of age, gender and education on the SC responses of 222 subjects who underwent the same differential conditioning paradigm. The demographic variables were found to predict a small but significant amount of variability in conditioned responding during fear acquisition, but not fear extinction learning or extinction recall. A larger differential change in SC during acquisition was associated with more education. Older participants and women showed smaller differential SC during acquisition. Our findings support the need to consider age, gender and education when studying fear acquisition but not necessarily when examining fear extinction learning and recall. Variability in demographic factors across studies may partially explain the difficulty in reproducing some SC findings.

Characterization of fear conditioning and fear extinction by analysis of electrodermal activity.

Electrodermal activity (EDA) is a measure of physical arousal, which is frequently measured during psychophysical tasks relevant for anxiety disorders. Recently, specific protocols and procedures have been devised in order to examine the neural mechanisms of fear conditioning and extinction. EDA reflects important responses associated with stimuli specifically administrated during these procedures. Although several previous studies have demonstrated the reproducibility of measures estimated from EDA, a mathematical framework associated with the stimulus-response experiments in question and, at the same time, including the underlying emotional state of the subject during fear conditioning and/or extinction experiments is not well studied. We here propose an ordinary differential equation model based on sudomotor nerve activity, and estimate the fear eliciting stimulus using a compressed sensing algorithm. Our results show that we are able to recover the underlying stimulus (visual cue or mild electrical shock). Moreover, relating the time-delay in the estimated stimulation to the visual cue during extinction period shows that fear level decreases as visual cues are presented without shock, suggesting that this feature might be used to estimate the fear state. These findings indicate that a mathematical model based on electrodermal responses might be critical in defining a low-dimensional representation of essential cognitive features in order to describe dynamic behavioral states.

Neuroscience of fear extinction: implications for assessment and treatment of fear-based and anxiety related disorders.

Current exposure-based therapies aimed to reduce pathological fear and anxiety are now amongst the most effective interventions for trauma and anxiety related disorders. Nevertheless, they can be further improved to enhance initial and long-term outcomes. It is now widely accepted that a greater understanding of the neurobiological mechanisms of fear extinction is needed to further develop and identify novel effective targeted treatments as well as prevention strategies for fear-based and anxiety-related disorders. Guided by elegant mechanistic, cellular, and molecular preclinical reports, data from imaging studies are beginning to shape our understanding of how fear is quelled in the human brain. In this article, we briefly review the neural circuits underlying fear extinction in rodents and healthy humans. We then review how these circuits may fail to extinguish fear in patients with anxiety disorders. We end with a discussion examining how fear extinction research may lead to significant advances of current therapeutics for anxiety disorders.