ON THE MATTER OF RULES - PAST-TENSE FORMATION AND ITS SIGNIFICANCE FOR COGNITIVE NEUROSCIENCE

If neuronal models are successful, they will account for specifically human complex behaviours. Most of these behaviours can be described as governed by rules. In recent years, much effort has been spent to elu cidate the neuronal basis of rules, and many researchers have focussed on modelling rules and regularities underlying language, particularly those relevant for past-tense formation. After introducing problems p osed by Fast-tense formation, important aspects of recent controversie s between connectionists and linguists concerning the nature of rules will be reviewed and analysed on the basis of elementary simulations. It is argued that modular networks with varying connection probabiliti es between their layers would be ideal for modelling learning and proc essing of past-tense formation, The motivation for postulating such ne tworks comes from neurobiological models of language and from neuroana tomical data about cortico-cortical connectivity. Furthermore, such mo dular networks may explain double dissociations of regular and irregul ar past-tense formation in neurological patients, as reported in recen t neuropsychological publications. It is concluded that past-tense for mation does not pose problems to pattern associators, given that some structure is built into the network which approximates wirings in the human cortex.