How good is the macaque monkey model of the human brain?

Macaque monkeys are widely used in order to understand the mechanisms of the human brain. But humans have capacities not found in monkeys, and their brains differ in important ways, for example in the proportions of different regions and in microstructure. However, this does not mean that we must abandon the monkey model, only that wherever possible, we should test whether generalizations can be made. One strategy is to use fMRI to visualize activations in humans, and compare these with activations in monkeys. Where the results are the same, we can then use information from single unit recording in those areas to suggest the mechanisms by which those areas perform their functions in the human brain.