Exploring brain functional connectivity in patients with taste loss: a pilot study

Abstract

Purpose: In a previous neuroimaging study, patients with taste loss showed stronger activations in gustatory cortices compared to people with normal taste function during taste stimulations. The aim of the current study was to examine whether there are changes in central-nervous functional connectivity in patients with taste loss.

Methods: We selected 26 pairs of brain regions related to taste processing as our regions of interests (ROIs). Functional magnetic resonance imaging (fMRI) was used to measure brain responses in seven patients with taste loss and 12 healthy controls as they received taste stimulations (taste condition) and water (water condition). The data were analysed using ROI-to-ROI functional connectivity analysis (FCA).

Results: We observed weaker functional connectivity in the patient group between the left and right orbitofrontal cortex in the taste condition and between the left frontal pole and the left superior frontal gyrus in the water condition.

Conclusion: These results suggested that patients with taste loss experience changes of functional connectivity between brain regions not only relevant to taste processing but also to cognitive functions. While further studies are needed, fMRI might be helpful in diagnosing taste loss as an additional tool in exceptional cases.

Keywords: Functional connectivity; Gustation; Taste loss; fMRI.

Fig. 1

Experimental design. The first four conditions of one session are shown in the figure with 10 volumes (3 s for each volume) recorded for each condition

Fig. 2

Two functional connections in the patient group were significantly weaker than in the control group. One was between the right and the left orbital frontal cortex (OFC) in the taste condition [T (17) = 6.79, connection threshold: p < 0.05, p-FWE corrected, left panel], another one was between the left Frontal Pole (FP) and the left Superior Frontal Gyrus (SFG) in the water condition [T (17) = 5.16, connection threshold: p < 0.05, p-FWE corrected, right panel]

Fig. 3

An ROI-to-ROI connectivity (RRC) matrix of one single-subject of taste condition created by the CONN toolbox. Each element in an RRC matrix is defined as the Fisher-transformed bivariate correlation coefficient (z-score) between a pair of ROI BOLD time series. We pre-defined 52 regions of interest (ROIs) and the calculated z-scores form a 52-by-52 matrix (the z-score was not calculated between one ROI and itself). The squares are shown/coloured when z-scores were above + 0.25 or below − 0.25