Talk:Critical period

I have put a few relatively minor comments in square brackets in the main article. I thought it was a very good summary. As a visual scientist I would have found it interesting to have had a bit more amplification of the evidence for critical periods in other modalities, e.g. speech. Perhaps some references could be provided for those topics, also I would have found references to a few relevant non-review but recent papers on visual system critical period topics (intrinsic signal imaging, 2-photon studies, fMRI of human) useful.

Author to reviewer B

Thanks for your most useful comments.

I have changed properties to physiology in section 2, para 1. The shrinkage of cells in the LGN does not affect their physiology, as far as we know, and the changes in physiology that have been found are relatively minor. I believe that all of Robert Hess’s fMRI data is from the visual cortex, and not from the LGN.

I have added the He et al study on rearing in the dark to the mechanisms section, where I think that it is more relevant than here.

The interactions between the movement pathway and the form and color pathway take place primarily at higher levels of the system, so I feel that to bring this in for development at the level of layer IV is a complication that one does not want to raise in a Scholarpedia article.

The experiments on ocular dominance and direction selectivity were done in the cat, where cells in layer IV have orientation and direction selectivity, but the combination of left and right eye input is much larger at higher layers, and it is the binocularity that produces selectivity for depth that is relevant, not the existence of separate left and right eye columns. However, I agree that the logic is arguable, and that the critical period for the disruption of stereopsis in the cat has not been established, so I have left the last sentence out. I have also added a sentence about White and Fitzpatrick and Katz and Crowley.

I did not mean to suggest a causal relationship between the end of the critical period and puberty – I was using a shorthand way of describing when the end of the critical period is in different species. I actually looked for a causal relationship by manipulating testosterone and cortisol in cats and did not find much. It would be very interesting to study the question in macaques or humans.

I have added references to imprinting, and the ability for infants to distinguish sounds in other languages.

I have added the White and Fitzpatrick reference to optical imaging, which is the main one on the use of this technique for develoment. The main references that I know about fMRI for visual deprivation in humans are those of Robert Hess on amblyopia, but I don't know of anything that relates to the critical period. Does the reviewer know something that I have missed?

Other comments have been incorporated.