Do “good” things motivate us? Positive Affect & Appetitive Motivation Psychology 320

Recap… The six “E’s” Evolution Environment Earlier Life Emotion Expectation Everyone Else

The Fourth “E”… Kinda What is “Affect”? What do we mean by that? Differentiate “Affect” from “Effect” “Affect” = Active Influence ”Effect” = End Result Affect is changing – Effect is final In Psychology, what do we mean by “Affect”? In Psychology, what do we mean by “Valence”? So… how then can “Affect” influence behavior?

”Affect” – A system for driving survival Operant Conditioning and Survival What are the key drivers in Operant Conditioning? What biological systems may drive these? How can those systems also work with Classical Conditioning? What is the relationship with survival? (I.e. Think Evolution!)

What is the system for positive affect? Simply stated – it is the aptly named – “reward system” or more often by neuroscientists, the “reward pathway”. It is made mostly of the: Nucleus Accumbens (NAcc) – Ventral Striatum Ventral Tegmental Area (VTA) PFC Caudate & Putamen – Dorsal Striatum Substantia Nigra Together – these make up the (more specifically named) “mesolimbic pathway” Basically, this pathway projects dopamine from the VTA and Substantia Nigra to all other regions

Nucleus Accumbens Dopamine is released into the NAcc from the VTA Stimulating NAcc – studies (rats, levers, and doing nothing else) “Thus, acting in diverse terminal fields [in NAcc], dopamine confers motivational salience (“wanting”) on the reward itself or associated cues” - Deckers Therefore, anything that sufficiently stimulates dopamine in the NAcc will increase the strength of “wanting” And of course… the delivery of dopamine to the NAcc elicits the sensation of “pleasure” NOTE: We’ll talk about “wanting” vs “liking/pleasure” later – may not always be the same… Hence why this is referred to as “the pleasure center”

Nucleus Accumbens Not surprisingly, the nucleus accumbens sends inhibitory projections to the PFC If pleasure is good enough – why should we need to think about it? Why decide? “Don’t think about this… just do it!" Dangerous connotations here… So what kinds of things bring about “pleasure”… Well, wouldn’t that be anything “good”? Much like “fear” underlies negative affect, “pleasure” underlies positive affect

Addiction – A brief aside Recall the rats and lever-pressing for nucleus accumbens stimulation “Addiction” can be defined biologically as the compulsive and irrational continuance of a behavior despite negative consequence. “Drugs of addiction” are appropriately named because of their effects on the mesolimbic pathway and NAcc. For instance: Cocaine inhibits the uptake of dopamine, allowing more to stay in the synapse Heroine, Morphine, Oxycontin, Hydrocodone, etc – stimulate activity in the NAcc by way of activating opioid receptors and basically, leading to more dopamine and/or general activity of the nucleus accumbens These drugs (and others) hijack the reward system.

Illustration of the various ways in which drugs of abuse can influence this pathway… mechanisms are not important here… just see that its happening

”Affect” – A system for driving survival Operant Conditioning and Survival What are the key drivers in Operant Conditioning? What biological systems may drive these? How can those systems also work with Classical Conditioning? What is the relationship with survival? (I.e. Think Evolution!)