The addictive substances share some ability to induce lasting structural changes in the central nervous system, specifically in regions implicated in reinforcement-motivation. Situational elements associated with the intake of these substances become attractive or outgoing incentives. In short, sensitization maintains the addictive behaviour, beyond or independently of other motivational elements (e.g., the rewarding effect of substances) or aversive properties specific to the situation of abstinence. This model of Robinson and Berridge (2003) would be different from the proposed theories of incentive or homeostatic theories.