COVID-19 consequences on motivational functioning: an ecological investigation of the role of momentary gustative-olfactory sensitivity and tonic heart rate variability

Background: Deficits in motivational functioning, including impairments in reward learning or reward sensitivity, are common in psychiatric disorders characterized by anhedonia, as in case of depression [1]. This transdiagnostic construct has been defined as the inability to experience pleasure in previously rewarding activities and stimuli and has been repeatedly associated with lower levels of tonic Heart Rate Variability (HRV), a measure of vagal modulation of the heart [2]. Anhedonia and depressive symptoms have been exacerbated by Coronavirus disease 2019 (COVID-19) pandemic in the general population. In line with previous evidence which report gustatory and olfactory disturbances (i.e., hyposensitivity) in psychopathological conditions particularly characterized by anhedonic symptoms, as for depression [3], the present study examined whether anosmia and ageusia (respectively defined as loss of smell and loss of taste sensitivity) two key consequences of Coronavirus disease 2019, could predict anhedonia. Methods: 114 healthy individuals (81 females) filled out a series of self-report scales assessing indices of psychological well-being (i.e., depression, anxiety, and stress; anticipatory and consummatory pleasure) and an experiential questionnaire investigating dispositional smell and taste sensitivity, followed by a laboratory session in which resting Heart Rate Variability (as a potential predictor of anhedonic behavior) was assessed and they were asked to perform the Probabilistic Reward Task (PRT) [4]. The Probabilistic Reward Task is a well-validated signaldetection task reflecting participants’ reward-related functioning and is considered a proxy of anhedonic behavior [5]. Task performance, operationalized by response bias (i.e., a measure of systematic preference to choose the most frequently rewarded stimulus) provides an objective measure of the ability to modulate adaptive behavior as a function of reinforcement history. The research protocol ended with a 4-days ecological momentary assessment of daily ratings of smell and taste sensitivity to food. Results: Multilevel analyses highlighted that lower tonic Heart Rate Variability (ß = .28; p < .001) and lower stable (trait-like) levels of smell and taste sensitivity (ß = .22; p < .05) independently and simultaneously predicted impaired performance on the Probabilistic Reward Task. Moreover, tonic Heart Rate Variability was not significantly associated with the trait-like common component of taste and smell sensitivity. Conclusions: The main strength of the study is the implementation of an ecological momentary assessment design to assess taste and smell sensitivity. Moreover, to our knowledge, this is the first study showing the association between resting Heart Rate Variability and performance on an objective task assessing anhedonic behavior such as the Probabilistic Reward Task. Considering that Heart Rate Variability represented a predictor of resilience during pandemic, as well as for psychopathology in general, and that ageusia and anosmia are two of the most frequent and relevant COVID-19 symptoms, the present study provides insight into the general worldwide exacerbation of mental health issues due to COVID-19 pandemic.