The Journal of Neuroscience, 0000, 20:RC117:1-5
RAPID COMMUNICATION
Pyramidal Cells, Patches, and Cortical Columns: a Comparative
Study of Infragranular Neurons in TEO, TE, and the Superior
Temporal Polysensory Area of the Macaque Monkey
Guy N.
Elston and
Marcello G. P.
Rosa
Vision, Touch, and Hearing Research Centre, Department of
Physiology and Pharmacology, The University of Queensland, Queensland,
4072 Australia
The basal dendritic arbors of layer III pyramidal neurons are known
to vary systematically among primate visual areas. Generally, those in
areas associated with "higher" level cortical processing have
larger and more spinous dendritic arbors, which may be an important
factor for determining function within these areas. Moreover, the
tangential area of their arbors are proportional to those of the
periodic supragranular patches of intrinsic connections in many
different areas. The morphological parameters of both dendritic and
axon arbors may be important for the sampling strategies of cells in
different cortical areas. However, in visual cortex, intrinsic patches
are a feature of supragranular cortex, and are weaker or nonexistent in
infragranular cortex. Thus, the systematic variation in the dendritic
arbors of pyramidal cells in supragranular cortex may reflect intrinsic
axon projections, rather than differences in columnar organization. The
present study was aimed at establishing whether cells in the
infragranular layers also vary in terms of dendritic morphology among
different cortical areas, and whether these variations mirror the ones
demonstrated in supragranular cortex. Layer V pyramidal neurons were
injected with Lucifer yellow in flat-mounted cortical slices taken from
cytoarchitectonic areas TEO and TE and the superior polysensory
area (STP) of the macaque monkey. The results demonstrate that cells in
STP were larger, had more bifurcations, and were more spinous than
those in TE, which in turn were larger, had more bifurcations and were
more spinous than those in TEO. These results parallel morphological variation seen in layer III pyramidal neurons, suggesting that increasing complexity of basal dendritic arbors of cells, with progression through higher areas of the temporal lobe, is a general organizational principle. It is proposed that the differences in
microcircuitry may contribute to the determination of the functional signatures of neurons in different cortical areas. Furthermore, these
results provide evidence that intrinsic circuitry differs across
cortical areas, which may be important for theories of columnar processing.
Key words:
intracellular injection; Lucifer yellow; extrastriate; visual; cortex; dendrite; spine
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