Research on the marmoset auditory system has shown that ________.
1) there is plasticity in the auditory cortex but it requires many thousands of trials to see the effects in brain scans.
2) neurons in A1 are not required to detect changes in pitch
3) there is plasticity in the auditory cortex and it only requires a small number of trials to see the change.
4) neurons in A1 are required to detect changes in pitch