Dynamic cerebral autoregulation (CA) describes the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (ABP). We tested the hypothesis that the efficiency of dynamic CA is increased by brain activation paradigms designed to induce hemispheric lateralization. Continuous recordings of cerebral blood flow velocity (CBFV) (bilateral, middle cerebral artery (MCA)), ABP, ECG, and end-tidal CO₂ (EtCO₂) were performed in 14 right-handed healthy subjects (aged 21-43 years), in the seated position, at rest and during 10 repeated presentations (30 s on-off) of a word generation and a constructional puzzle. During rest or activation non-stationarities were not found. Transfer function analysis of the ABP(input)-CBFV(output) relationship was performed for the 10 separate segments of data with duration 51.2 s during activation and compared with baseline data. During activation, the coherence function below 0.05 Hz was significantly increased for the right MCA recordings for the puzzle tasks compared to baseline values (0.36 ± 0.16 vs 0.26 ± 0.13, p<0.05), and for the left MCA for the word paradigm (0.48 ± 0.23 vs 0.29 ± 0.16, p<0.05). In the same frequency range, the puzzle paradigm led to significant increases in gain for both the right (0.69 ± 0.37 vs 0.46 ± 0.32 cm.s^-1.mmHg^-1, p<0.05) and left hemispheres (0.61 ± 0.29 vs 0.45 ± 0.24 cm.s-1.mmHg^-1, p<0.05), and for the left hemisphere during the word tasks (0.66 ± 0.31 vs 0.39 ± 0.15 cm.s-1.mmHg^-1, p<0.01). Significant reductions in phase were observed during activation with the puzzle for both right (-0.04 ± 1.01 vs 0.80 ± 0.86 radians, p<0.01) and left hemispheres (0.11 ± 0.81 vs 0.57 ± 0.51 radians, p<0.05) and for the right hemisphere during the word paradigm (0.05 ± 0.87 vs 0.64 ± 0.59 radians, p<0.05). Brain activation also led to changes in the temporal pattern of the CBFV step response. We conclude that transfer function analysis suggests important changes in dynamic CA during mental activation tasks.