Visual receptive fields (RFs) are small areas of the visual field where a stimulus induces a responses of a particular neuron from the visual system. RFs can be mapped using reverse crosscorrelation technique, which produces raw matrices containing both spatial and temporal information about the RF. Though this technique is frequently used in electrophysiological experiments, it does not allow formal comparisons between RFs obtained under different experimental conditions. In this paper we propose the use of Generalised Additive Models (GAM) including complex interactions, to obtain smoothed spatio-temporal versions of RFs. Moreover, the proposed methodology also allow for the statistical comparisons of the RFs obtained across various experimental conditions. Data analysed here derive from studies of neurons' activity in the visual cortex of behaving monkeys. Our results suggest that the GAM-based technique proposed in this paper can be a flexible and powerful tool for assessing receptive field properties.