Fig. 4.

Human prefrontal gray matter scales in volume as expected for its number of neurons. Each graph shows how the total V_GM in the prefrontal (A), intermediate (B), and occipital regions (C) in each species scales with the number of neurons in the cortical regions. Plotted functions exclude the human data points (in black). Exponents are (A, prefrontal) 1.290 ± 0.118 (r² = 0.960, P = 0.0001), (B, intermediate) 1.349 ± 0.173 (r² = 0.924, P = 0.0006), and (C, occipital) 1.285 ± 0.210 (r² = 0.872, P = 0.0017). Notice that the human cortex has the expected V_GM for the local number of neuron in each of the three cortical regions, including the prefrontal cortex.