A quantitative dendritic analysis of four functionally distinct areas of human cerebral cortex

Recent investigations have begun to elucidate the function of dendritic arbors, revealing that the geometry of dendrites and the presence of dendritic spines play important roles in both simulated and actual dendritic function (Midtgaard, 1994). The present study attempts to correlate dendritic complexity with cortical function under the assumption that connectivity in a local cortical area may determine its more holistic functional properties. Two human brains (ages: 23 and 69 years) were used for the present study. Four cortical areas (Brodmann\u27s [1908] areas 3, 1, and 2; area 22; area 44; and area 10), respectively representing Benson\u27s four levels of cortical function (primary, unimodal, heteromodal, and supramodal; 1993, 1994), were stained with the modified rapid Golgi technique (Scheibel & Scheibel, 1978). Twenty supragranular pyramidal cells per cortical level were selected (N = 80). Basilar dendritic systems were analyzed using the Neurolucida computer/microscope interface system (Microbrightfield, Inc.). Dendritic measures, which included total dendritic length (TDL), mean dendritic length (MDL), dendritic segment count (DSC), dendritic spine number (DSN), and dendritic spine density (DSD), were used to determine dendritic complexity. All dendritic measures, with the exception of MDL, increased from primary to supramodal cortex. The present findings are consistent with previous research correlating dendritic measures and cortical function (Larsen, Wainwright, Swanson, & Jacobs, 1994; Scheibel, Conrad, Perdue, Tomiyasu, & Wechsler, 1990; Scheibel et al., 1985) and suggest that dendritic extent is related to the functional capabilities of human cerebral cortex