With generative artificial intelligence (GenAI) becoming increasingly prominent in creative work relying on divergent thinking, concerns arise about overreliance and its potential to erode human creativity. While the impact of GenAI is intensively researched for decision-making, critical thinking, and problem-solving—with both immediate and long-term effects observed—research is scant regarding divergent thinking. We address this gap by proposing an experimental study with a twofold objective: evaluating (1) how neurophysiological activity (measured directly with EEG and indirectly with eye-tracking) varies when ideating alone, with GenAI, or with a human peer, and (2) how a divergent thinking session with GenAI influences creative potential and brain activity during subsequent solo ideation. We seek to contribute to the understanding of human-GenAI creative collaboration dynamics and to inform the design of neuroadaptive systems that enhance, rather than undermine human creativity over time.