  We have studied the single pulse emission from two pulsars, PSR B0844-35 and
PSR B1758-29, over a wide frequency range of 300-750 MHz using the uGMRT. The
two pulsars have relatively wide profiles with multiple components, that are a
result of the line of sight traversing near center of the emission beam. In
both pulsars the single pulse sequences show the presence of two distinct
emission states, where the profiles become much brighter at the center with
prominent core components during one of the modes, while in the other mode the
single pulses show odd-even subpulse drifting with periodicity around 2$P$, $P$
being the rotation period of the pulsar. The centrally bright mode was seen for
10 percent of the observing duration in PSR B0844-35, which usually lasted for
short durations of around 10 pulses, but had two longer sequences of around 100
pulses. On the contrary the centrally bright mode was dominant in PSR B1758-29
and was seen for around 60 percent of the observing duration. PSR B1758-29 also
showed period amplitude modulations of 60-70$P$ in both modes. The mode
changing in these two pulsars facilitates investigation of the sparking process
in the inner acceleration region, dominated by non-dipolar magnetic fields. The
change in the surface magnetic field configurations likely results in the
emission mode change.
