Electrical conductivity measurements on well-characterized materials in the laboratory allow accurate interpretations of high-conductivity anomalies within the lithosphere and asthenosphere, both affected by substantial deformation over geological times. However, only a few experiments so far have measured rock conductivity during controlled deformation at high pressures (≥ 1 GPa) and temperatures (500-1000 °C). Here we report the first successful deformation experiments performed in a new-generation Griggs-type apparatus adapted for electrical measurements. The experiments were conducted on samples of Åheim dunites at a confining pressure of 1 GPa and temperatures of 500, 650 and 800 °C. Our results show very different electrical responses in the elastic and plastic regimes. Stress and strain can significantly impact the electrical conductivity of peridotites by changing the thickness, number or geometry of grain boundaries. At fixed P-T conditions, the electrical conductivity varies within an order of magnitude during elastic loading and unloading, which motivates to reappraise interpretations of electrical anomalies in mantle rocks, at least in tectonically active regions. Upon additional development to achieve deformation up to 4 GPa (≃ 120 km depth), the design presented here opens a fully new research field, which will help to more deeply understand electrically conductive anomalies in rocks under stress at depth, notably within the lower crust, upper mantle and subducting slabs.