Motivation and Desire by William J. Freed

Author:William J. Freed
Language: eng
Format: epub
ISBN: 9783031104770
Publisher: Springer International Publishing

11.4 Aversion, Novelty, and Movement

Dopamine neurons are involved not only in “wanting;” aversive events can increase the activity of dopamine neurons as well (Anstrom et al. 2009; McCullough et al. 1993; Salamone 1994; Young 2004). Blocking dopamine interferes with how animals respond to aversive events (Acquas and Di Chiara 1994; Fenu et al. 2001). There is also evidence that dopamine neurons are involved in aversive experiences in human subjects (see Salamone and Correa 2012). For example, a part of the brain that receives input from substantia nigra dopamine neurons was activated in an experimental task involving learning motivated by electric shock in human subjects (Delgado et al. 2011). Thus, the reader should be aware that what dopamine neurons do, and particularly what separate groups of dopamine neurons do, is more complex than simply signaling “reward.”

Willingness to overcome obstacles to obtain or accomplish something is the essence of motivation. Animals may eat food that is provided, without a requirement for work to obtain it, even if the nucleus accumbens or the VTA-nucleus accumbens that is part of the dopamine system is damaged (Salamone et al. 2007). If the dopamine system is destroyed entirely, animals do not eat (Ungerstedt 1971a). Even in this case, it has been argued that the animals might still like food, but they are unable or unwilling to exert the effort required to eat. Without dopamine, an animal may experience pleasure, but the pleasure has no motivational consequence.

Other parts of the brain and other systems are also, of course, involved in motivation; the dopamine system does not work in isolation (Wise and Bozarth 1984). For example, the orbitofrontal cortex (OFC) provides information about the expected value of potential rewards (Chap. 13), thus coordinating with dopamine neurons to guide behavior (Sharpe and Schoenbaum 2016; Takahashi et al. 2009, 2011, 2017).

Novelty is an important concept in the context of motivation and in the function of dopamine neurons. In this context, novel means an experience novel to that individual. Novel events are more salient than those that are repeated or routinary. Novelty is important for reward and learning (Xu et al. 2021; Houillon et al. 2013) and for the function of dopamine neurons (Costa et al. 2014; Hazy et al. 2010).

One explanation of how dopamine neurons signal novelty, motivation, and movement, which on the face of it are seemingly separate functions, comes from Montague, Schultz, and Dayan (Montague et al. 1996; Schultz et al. 1997; Schultz 2001, 2007). Dopamine neurons produce a very short-term (seconds) message, which signals unexpected rewards, and a somewhat longer-term (minutes) message, which may be more important for reward in general, as well as generally salient events. One model suggests that slower dopamine responses are related to effort or response vigor (Niv et al. 2007). This will be considered in more detail in Chap. 13. It should also be mentioned that what dopamine does to control motivation is complex and still not entirely understood (see Dayan and Balleine 2002). In fact, the short-term response may signal novelty rather than reward per se (Redgrave and Gurney 2006).

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