In 2006 Sharma & Dorman measured the P1 response in deaf children who received cochlear implants at different ages to examine the limits of plasticity in the central auditory system. Those who received cochlear implant stimulation in early childhood (younger than 3.5 years) had normal P1 latencies. Children who received cochlear implant stimulation late in childhood (younger than seven years) had abnormal cortical responses latencies. However, children who received cochlear implant stimulation between the ages 3.5 and 7 years revealed variable latencies of the P1. Sharma also studied the waveform morphology of the P1 response in 2005 and 2007. She found that in early implanted children the P1 waveform morphology was normal. For late implanted children, the P1 waveforms were abnormal and had lower amplitudes when compared to normal waveform morphology. In 2008 Gilley and colleagues used source reconstruction and dipole source analysis derived from high density EEG recordings to estimate generators for the P1 in three groups of children: normal hearing children, children receiving a cochlear implant before the age of four, and children receiving a cochlear implant after the age of seven. Findings concluded that the waveform morphology of normal hearing children and early implanted children were very similar.