A Level Biology Edexcel: Topic 5 - 8: how did Katz and Crowley identify the innate structure of the column of dominance of the occipital lobe?

Question

how did Katz and Crowley identify the innate structure of the column of dominance of the occipital lobe?

seremi amune · Accepted Answer

they worked with ferrets 
injected labelled tracers 
this showed that the columns of dominance were formed before the critical period

How did Katz and Crowley identify the innate structure of the column of dominance of the occipital lobe?