Complex sentence: While at the Menninger clinic he studied patients with schizophrenia, and discovered a unique relationship between them and their mothers; this led to his concept of differentiation of self, which is autonomy from others and separation of thoughts from feelings.
Split into simpler sentences: While at the Menninger clinic he studied schizophrenic patients and discovered a unique relationship between the patients and their mothers. This relationship led to his concept of differentiation of self which is autonomy from others and separation of thoughts from feelings.