Different areas of the gray matter are responsible for different neural functions, such as vision, audition, somatosensory, motor, language, etc. The various functional cortical areas can communicate with each other through the connections formed by the white matter underneath the gray matter.
Brodmann area 17 is the primary visual cortex, also known as the striate cortex or V1, as shown in here:
Some other higher visual areas, called extrastriate areas, including V2, V3, V4, V5 (also called medial-temporal MT) are shown here:
Note that all there visual areas are just patches of various sizes and locations on the cortex, and they are all connected as shown in this unfolded and flattened visual cortex: