Recent observations, suggesting that subpulse drifting, pulse nulling and profile mode-changes are related phenomena, are reviewed and it is argued that these are associated with global changes in the magnetosphere. Long simultaneous multi-frequency observations are useful to test this premise as is illustrated by the preliminary results from a recent study of PSR B0031–07, B0809+74 and B2319+60. Such observations for a larger sample of pulsars will be useful to constrain recent models, invoking global changes in the pulsar magnetosphere, proposed to explain observations demonstrating association of spin-down changes with profile mode-changes.
