Additional studies have also provided further evidence for the role of the nucleus accumbens on sexual behaviour in rats. In a study conducted by Wood et al., male rats were divided into three conditions, and were presented with a cotton ball laden in either saline (control group), estrous vaginal smear of a familiar female (experimental group), and estrous vaginal smear of a novel female (experimental group). In this experiment, the role of the nucleus accumbens was characterized through recording neuronal activity of single cells in this area of the brain. Results from this study showed a greater proportion of neuronal activation when initially presented with a novel estrus stimulus in comparison to familiar estrus stimulus. Subsequent presentations of the novel estrus stimulus did not show an increase neuronal activity.