Prefrontal dysfunction in post-COVID-19 hyposmia: an EEG/fNIRS study

Livio Clemente; Marianna La Rocca; Nicola Quaranta; Lucia Iannuzzi; Eleonora Vecchio; Antonio Brunetti; Eleonora Gentile; Michele Dibattista; Simona Lobasso; Vitoantonio Bevilacqua; Sebastiano Stramaglia; Marina de Tommaso

doi:10.3389/fnhum.2023.1240831

Prefrontal dysfunction in post-COVID-19 hyposmia: an EEG/fNIRS study

Front Hum Neurosci. 2023 Sep 27:17:1240831. doi: 10.3389/fnhum.2023.1240831. eCollection 2023.

Affiliations

¹ Department of Translational Biomedicine and Neuroscience (DiBraiN), University of Bari Aldo Moro, Bari, Italy.
² M. Merlin Inter-university Physics Department, University of Bari, Bari, Italy.
³ Laboratory of Neuroimaging, Keck School of Medicine of USC, USC Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA, United States.
⁴ Department of Electrical and Information Engineering, Polytechnic University of Bari, Bari, Italy.

^# Contributed equally.

Abstract

Introduction: Subtle cognitive dysfunction and mental fatigue are frequent after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, characterizing the so-called long COVID-19 syndrome. This study aimed to correlate cognitive, neurophysiological, and olfactory function in a group of subjects who experienced acute SARS-CoV-2 infection with persistent hyposmia at least 12 weeks before the observation.

Methods: For each participant (32 post-COVID-19 patients and 16 controls), electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) data were acquired using an integrated EEG-fNIRS system during the execution of a P300 odd-ball task and a Stroop test. The Sniffin' Sticks test was conducted to assess subjects' olfactory performance. The Montreal Cognitive Assessment (MoCA) and the Frontal Assessment Battery (FAB) were also administered.

Results: The post-COVID-19 group consisted of 32 individuals (20 women and 12 men) with an average education level of 12.9 ± 3.12 years, while the control group consisted of 16 individuals (10 women and 6 men) with an average education level of 14.9 ± 3.2 years. There were no significant differences in gender (X² = 0, p = 1) or age between the two groups (age 44.81 ± 13.9 vs. 36.62 ± 11.4, p = 0.058). We identified a lower concentration of oxyhemoglobin (p < 0.05) at the prefrontal cortical level in post-COVID-19 subjects during the execution of the Stroop task, as well as a reduction in the amplitude of the P3a response. Moreover, we found that post-COVID-19 subjects performed worst at the MoCA screening test (p = 0.001), Sniffin's Sticks test (p < 0.001), and Stroop task response latency test (p < 0.001).

Conclusions: This study showed that post-COVID-19 patients with persistent hyposmia present mild deficits in prefrontal function, even 4 months after the end of the infection. These deficits, although subtle, could have long-term implications for quality of life and cognitive wellbeing. It is essential to continue monitoring and evaluating these patients to better understand the extent and duration of cognitive impairments associated with long COVID-19.

Keywords: anosmia; cognitive dysfunction; event related potentials; long COVID-19; near infra-red spectroscopy.

Grants and funding

The study was supported by Pon 4frailty, Mur, Italy, NextGeneration EU (NGEU) (MUR), National Recovery and Resilience Plan (NRRP), and project MNESYS (PE0000006) – (DN. 1553 11.10.2022).