In vivo intracellular recording and labeling of neurons in the forepaw barrel subfield (FBS) of rat somatosensory cortex: possible physiological and morphological substrates for reorganization.

We examined the physiological properties and morphology of neurons in the forepaw barrel subfield (FBS) in somatosensory cortex (SI) of adult rats using in vivo intracellular recording and biocytin labeling techniques. Our results show that both pyramidal and non-pyramidal type spiny neurons can be activated with short latency by peripheral stimulation. FBS neurons within individual barrels receive both suprathreshold and subthreshold convergent input from one or more forepaw digits and pads. We hypothesize that some of these subthreshold inputs may be elevated to firing level by some, as yet unknown, mechanism(s) following peripheral deafferentation. Examination of the relationship between the dendritic pattern of labeled neurons and individual barrels within the FBS suggests that neurons with dendrites extending into neighboring barrel bands may serve as a possible morphological substrate for immediate reorganization.