In the primary somatosensory cortex of the mouse there are approximately 35 cytoarchitectonic units, named ‘barrels’ (Woolsey & Van der Loos 1970), per hemisphere. There are also about 150 similar, but smaller, barrels. Each of the 35 large barrels is held to be the cortical endstation of the projections from one of the similar number of mystacial vibrissae on the animal’s contralateral muzzle. These barrels are arranged in a pattern that is topologically equivalent to the pattern of the whiskers. There are five rows of whiskers and of barrels, named A, B, C, D and E, and four whiskers and barrels that straddle the ends of the rows named α, β, γ and δ. Morphological data obtained from mice (Woolsey & Van der Loos 1970; Van der Loos & Woolsey 1973) together with physiological data obtained from the rat (Welker 1971) contributed to the recognition of the relation between whiskerpad and barrelfield. A whisker and its corresponding barrel bear the same letter-number combination rather as on a chessboard. (For a review, see Van der Loos (1976
b
).)In what follows, analyses referred to are on mice, unless otherwise stated.
Responses of neurons in the primary somatosensory cortex to itch- and pain-producing stimuli in rats
