Effect of walking slope on cognitive performance. Electrophysiological evidence of dual-task interference.

The neural basis of cognitive-motor dual-tasking (CMDT), which involves the simultaneous performance of motor and cognitive tasks, has received increasing attention. However, the electrophysiological impact of walking complexity on concurrent cognitive performance remains unclear. This study examined how walking slope modulates cognitive performance and event-related potentials during a visuomotor discrimination task requiring a simple manual keypress response to target stimuli while walking on a treadmill. Twenty healthy adults (20-36 years) completed the task under three slope conditions (downhill -11%, flat 0%, uphill +11%) while electroencephalogram was recorded. Behavioral results showed preserved accuracy across conditions, with slower response times during downhill walking relative to uphill walking. Early sensory processing was strongly affected by locomotor complexity: both uphill and downhill walking elicited larger P1 amplitudes and reduced N1 amplitudes relative to flat walking. In contrast, late cognitive processing indexed by the P3 was largely preserved, although the differential P3 was selectively reduced during uphill walking, suggesting selective redistribution of resources under the highest energetic and cognitive load, consistent with a possible capacity-sharing account. Uphill walking was perceived as the most physically and cognitively demanding condition, while the lowest mean state-anxiety score was observed after uphill walking. Overall, these findings indicate that locomotor complexity selectively modulates early sensory and attentional processing during CMDT, while higher-order decision processes appear relatively preserved. The results are consistent with models of flexible resource allocation and provide insights relevant to the design of motor-cognitive training and rehabilitation protocols.