...studies that show that every part of the cortex does essentially the same thing!
I would be much interested in seeing these studies - Although the brain is plastic and inter-individual differences can be substantial, it is generally accepted that functional regions are well defined in terms of their anatomical locations and brain mapping was, and still is, a field of research in its own right.
tiny areas of neocortex [were studied]
have been done, and showing
what it does
Notable examples include singe-unit recordings (cellular level - as tiny as you can get) that mapped the primary visual cortex (V1) and auditory cortex (AI). Such studies have shown that V1 contains retinotopic maps, and AI contains tonotopic maps, i.e., these studies showed that each region in the retina projects to a well-defined and neatly organized region in V1 (e.g., Cowey, 1979), and well-defined anatomical locations in the cochlea project to well-defined and well organized regions in AI (e.g., Ozaki & Hashimoto, 2007).
what information it contains
is hard to answer, as the brain is not a hard disk that can be read back. However, studies on Alzheimer patients do reveal that old memories are often relatively spared, while new ones fail to be stored properly, indicating indirectly what information the affected cortex contains.
- Cowey, Quarterly J Exp Psychol; 31(1): 1-17
- Ozaki & Hashimoto, Can J Neurol Sci (2007); 34(2): 146-53