The effect of low-level toluene on working memory maintenance has its own neural network basis rather than the...

Working memory (WM) involves different neural network mechanisms that underlie the encoding of external stimuli and the active maintenance of non-external stimulus information. We have demonstrated that short-term exposure to 70-ppb toluene impairs the encoding network. However, its role in the maintenance network remains unclear. Twenty-three healthy youths were recruited and exposed to 0, 17.5, 35, and 70 ppb toluene in a closed environmental chamber for 4 h to clarify the effect of low indoor toluene concentrations on WM-maintaining brain networks. A visual WM test was conducted after the exposure, and electroencephalogram signals were collected during WM maintenance. Directional transfer functions were used to construct the maintenance network, and the functional connectivity (FC) changes were compared at different toluene concentrations. The FC strength was significantly highest in the frontal region during WM maintenance and was concentrated in the Fz channel. The FC outflow strength of the frontal region and Fz channel increased significantly with increasing of toluene concentration. The FC strength of the Fz channel flowing to the F3, Fp2, P4, and O2 channels was significantly enhanced with increasing toluene concentration. The enhancement of intrafrontal and frontal-posterior connectivity during maintenance was attributed to the increased demand for executive control of inhibitory interference caused by low toluene concentrations. The effects of low-concentration toluene exposure on WM maintenance have an independent neural network basis rather than being a continuation of network changes during encoding.