Autonomic Correlates of Letter Cancelation Task: What the Attention Load May Evoke?

OBJECTIVE: Attention can be assessed through Letter cancelation tasks (LCT) that employ visuospatial selection and appropriate motor responses. We examined the performance in the LCT with increasing attention load, and determined the related autonomic changes. METHODS: Autonomic parameters were estimated in healthy males at baseline and during three different cognitive load conditions using the LCT. RESULTS: Results revealed a statistically significant difference (n = 30) in the percent accuracy (χ2(2) = 15.2, p < .001) and percent omission (χ2(2) = 13.3, p = 0.001) with the increasing challenge in the LCT. The vagally-mediated measures of heart rate variability were significantly decreased with the commencement of the task revealing a parasympathetic withdrawal. The respiratory sinus arrythmia was decreased, and the photoplethysmography amplitude was significantly reduced (χ2(3) = 14.2, p = 0.003) as the attention demand increased. CONCLUSION: The performance declined with the increasing attention load. LCT evokes autonomic perturbations though overall autonomic variability does not change remarkably.