This is an excellent review of area V1 for Scholarpedia. It is very accessible to the general reader and, at the same time, it provides enough detail. Most of the important topics on V1 organization and function are addressed in the review.
Thanks for these comments and for the suggestions below. I have tried to take them all on board, though the article is already much longer than suggested by the guidelines, so I did not add many words.
Perhaps, a topic that could be also mentioned is the effect of monocular deprivation on V1 functional architecture. Monocular deprivation leads to dramatic changes in V1 wiring, a finding that has clinical implications. There is no need to devote too much space to this topic, as it is covered in other chapters of Scholarpedia. However, it should be mentioned somewhere.
I have added a paragraph on this important topic (“Functional architecture shows marked changes during development…”), and added links to the Scholarpedia article “Critical period”.
The review could also provide a brief description of horizontal connections that can span several millimeters of cortex in the superficial layers of area V1. Although the functional role and organization of these connections are still matter of debate, they are likely to play an important role in V1 function.
I have added a paragraph about this topic as well (“Yet another area of study concerns the role of long-range horizontal axons…”).
The rest of my comments are purely cosmetic and are described below.
I would consider changing the following sentences:
‘The main task of V1 is to process visual inputs from the LGN and send the results of this processing to higher visual areas’. It could be argued that an important task of area V1 is to send rapid signals to subcortical targets (e.g. superior colliculus) to trigger a behavior (e.g. moving the eyes) in parallel to sending the information to higher cortical areas. A possible alternative sentence could be: ‘The main task of V1 is to process visual inputs from the LGN and send the results of this processing to higher visual areas and subcortical structures.
‘V1 also sends some output to multiple brain regions, including superior colliculus, pulvinar, and pons.’ Although the feedback to LGN is mentioned in the following sentence, it seems confusing not to include LGN in the first sentence, as the LGN is one of the major V1 subcortical targets. A possible alternative sentence could be: ‘V1 also projects to subcortical structures including LGN, superior colliculus, pulvinar and pons.’
‘Feedback inputs from other cortical areas arrive in superficial layers, principally in layer 1.’ This statement could be misinterpreted. It is true that most cortical areas send feedback inputs to layer 1 of area V1. However, IT is the only area whose feedback projection is restricted to this layer. Other cortical areas such as V2 and MT send strong feedback to layers 2+3, 4B, 5 and 6. Perhaps, it would be better to say that ‘Most feedback inputs from other cortical areas arrive in superficial layers of area V1.’
‘In primates, this distinction between layers can be further refined. For instance layer 4 of V1 is divided into sublayers 4A, 4B, 4Cα, and 4Cβ. LGN inputs arrive in 4C, and segregate depending on the source: magnocellular LGN cells to 4Cα and parvocellular cells to 4Cβ.’ The Koniocellular LGN inputs are not mentioned in the review and they are likely to become increasingly important, as we learn more about them! A short sentence mentioning these inputs may be appropriate. For example: ‘The Koniocellular LGN cells project to layer 4A and the superficial layers of the cortex.’