Cholinergic dysfunction might affect backward masking performance: evidence from schizophrenia

Abstract

In visual backward masking, a briefly presented target is followed by a mask, which decreases performance on the target. We hypothesized that recurrent processing amplifies neural response to the briefly presented target if no mask follows and that this recurrent processing is interrupted when the mask is presented. In this case, neuromodulation, for example of the cholinergic system, may enhance the neural responses to the target. Hence, if neuromodulation is dysfunctional, masking should be strongly deteriorated. Here, we tested schizophrenia patients, a population that is known to have deficits in the cholinergic system, in a masking paradigm while recording their EEG. We found evidence for two mechanisms of neuromodulation: reduced N1 amplitudes and increased trial-by-trial N1 variability. First, N1 amplitudes correlated with performance, and the two were strongly reduced in patients compared to healthy controls. Second, we estimated the N1 variability using a two-step graph-based method and found that patients had higher N1 peak latency variability than controls. After correcting for the latency variability, patients still showed smaller N1 amplitudes than controls. Hence, N1 amplitudes are both diminished and highly variable in patients. Our results suggest that cholinergic system deficits might impair backward masking performance, which is reflected in the EEG N1 component.

Meeting abstract presented at VSS 2018