A 25-year-old man presents to the neurology outpatient clinic with complaints of weakness of all four limbs for the last 2 days. He had a diarrheal illness 2 weeks ago that resolved after taking antibiotics. On examination, his speech and higher mental functions are intact. He also has bilateral facial nerve palsy. Power in both upper and lower limb muscles was 3/5 with absent reflexes and mute plantars. Which of the following abnormalities would be expected in the nerve conduction studies at this time?