Dendritic trees and cutaneous receptive fields of adjacent spinocervical tract neurones in the cat.

1. The relationship between the dendritic trees and the receptive fields of adjacent spinocervical tract neurones were studied using the intracellular injection of horseradish peroxidase in chloralose‐anaesthetized, paralysed, cats. 2. Fourteen pairs of neurones were successfully stained and the receptive fields of twelve pairs were also defined. Five of the pairs were ‘rostrocaudal pairs’, i.e. in line within +/‐ 50 micrometer of each other in the rostrocaudal axis of the cord. Nine of the pairs were ‘mediolateral pairs’, i.e. in line within +/‐ 50 micrometer of each other in the mediolateral axis of the cord. 3. For twelve pairs of stained neurones, for which the receptive fields were described, a correspondence was found between the organization of their dendritic trees and their receptive fields. 4. All five rostrocaudal pairs of neurones had interdigitating dendritic trees together with overlapping receptive fields. 5. Of the seven mediolateral pairs, four had receptive fields which overlapped and interdigitating dendritic trees. The remaining three had separate receptive fields and non‐interdigitating dendritic trees. 6. The results are discussed in relation to previous work on the columnar organization of the receptive fields of s.c.t. neurones and the columnar organization of hair follicle afferent fibre terminals in the spinal cord. The hypothesis is advanced that the receptive fields of most s.c.t. neurones are defined by their connexions with hair follicle afferent fibres such that along the mediolateral axis spatial separation of the dendritic trees of s.c.t. neurones is crucial for receptive field separation.