Assessment and Scientific Progresses in the Analysis of Olfactory Evoked Potentials

Abstract

The human sense of smell is important for many vital functions, but with the current state of the art, there is a lack of objective and non-invasive methods for smell disorder diagnostics. In recent years, increasing attention is being paid to olfactory event-related potentials (OERPs) of the brain, as a viable tool for the objective assessment of olfactory dysfunctions. The aim of this review is to describe the main features of OERPs signals, the most widely used recording and processing techniques, and the scientific progress and relevance in the use of OERPs in many important application fields. In particular, the innovative role of OERPs is exploited in olfactory disorders that can influence emotions and personality or can be potential indicators of the onset or progression of neurological disorders. For all these reasons, this review presents and analyzes the latest scientific results and future challenges in the use of OERPs signals as an attractive solution for the objective monitoring technique of olfactory disorders.

Keywords: ERPs; OERPs; anosmia; brain; electroencephalography; grand averaging; hyposmia; olfactory dysfunction; olfactory evoked potentials; smell.

Figure 1

Examples of OERPs: peak amplitude is measured from baseline (0 $\mathsf{\mu }$V) and peak latency from stimulus onset (0 ms).

Figure 2

International 10–20 system (channel reduction). EEG activity related to olfactory is recorded with electrodes placed in the midline (orange line) at the Fz, Cz and Pz sites.

Figure 3

Grand averaging and its construction. In the ERP-image plot, each single trial is encoded as a colored line, warm colors representing positive activity and cool colors, negative activity.

Figure 4

Taxonomy of the potential and application fields of OERP, resulting from the review of the literature.

Figure 5

OERPsfor different examples of young and older subjects. OERP amplitude of an older participant is smaller and the peak latency is longer than that of a young participant [57].

Figure 6

OERPfor a normal control subject and for a patient with Alzheimer’s disease (age 79), recorded at Pz position [83].

Figure 7

Comparison of the parameters of OERP components of multiple sclerosis patients and healthy controls in [85].