Resumen de Non-homogeneous spatial configuration of vibrissae cortical representation in layer IV of the barrel somatosensory cortex
Eliana Guic, Ximena Carrasco, Eugenio Rodriguez, Ignacio Robles, Michael M. Merzenich
In the present experiments we studied exclusive and overlapping cortical representational áreas of the vibrissae in layer IV cells, across the entire barrel subfield of the rat somatosensory cortex, looking for evidences that would challenge the present assumptions of homogeneity and symmetry among cortical columns in this sensorial system. Our main findings were that in layer IV of the rat barrel cortex: A) Size of vibrissae cortical representational áreas (X=0.4174mm²; SD=0.025) was not homo geneous, vibrissae in dorsal rows (A-B) had significantly smaller áreas than those in ventral rows (D-E), a pattern that repeated itself in ares 1-4. B) This difference arises from vibrissal representational overlap, and not from variations in exclusive zones, which are surprisingly homogeneous in size across the barrel cortex (X=0.079mm²; SD=0.0075); C) The extent of overlapping cortical áreas varied systematically, with intra-row overlapping áreas having a predominant bias (71.4% of total overlapping) independent of área sizes. Accordingly, vibrissae shared receptive fields with an average of 1.15 vibrissae in the same row and 0.38 in the same are. Barrel cortex has been viewed operationally as a conglomérate of essentially homogenous cortical columns that interact equivalently in the are and row dimensions. Our simple but global cortical reconstructions show that this predominant view should be revised. We postúlate that the vibrissae/barrels spatial disposition in rows and ares has a relevant functional meaning, related to different sensory capabilities.
