Ray has written about the uselessness of the authoritarian concept of "protocol" as a guide of behavior, thinking and living in general. Ray's motto instead is that the only valid protocol would be something along the lines of "perceive, think, act".
This study seems to establish that low serotonin (high dopamine) is key to being able to act according to Ray's motto. High serotonin, on the other hand, was associated with a protocol-like thinking and behavior, which the study calls "flexible, goal-directed responding". The paper also cites studies showing that serotonin is implicated in punishment and behavioral inhibition, as well as guilt, shame and depression.
Btw, I find it funny that they call the "goal-directed responding" "flexible" while the "stimulus-response habitual response" is viewed as rigid and inflexible.
"...Previous studies have yielded contradictory results about the interaction of dopamine (DA) and 5-HT in this balance. It has been suggested that DA biases behavior towards habitual responding, with 5-HT offsetting this phenomenon and directing the balance toward more flexible, goal-directed responding. However, previous research in animals and humans suggests roles for DA in both goal-directed and habitual action (De Wit et al., 2012). Furthermore, 5-HT has been implicated in punishment and behavioral inhibition and, more specifically, a reduced incentive motivation when 5-HT is low (Sanders et al., 2007; Cools et al., 2008; Hebart and Gläscher, 2014). Therefore, the relative and multiple roles of DA and 5-HT in the balance of goal-directed and habitual responding are unclear."
http://ijnp.oxfordjournals.org/content/ ... yv050.full
"...The paper by Worbe et al. (2015), which was recently published in this journal, focuses on the effects of acute tryptophan (TRP) depletion (ATD), a neurodietary physiological method to decrease central nervous 5-HT synthesis in humans for a short period of time, on the balance between hypothetical goal-directed and habitual systems. In this particular study conducted in healthy adult volunteers, a short-term serotonergic deficit induced by ATD was associated with a shift of behavioral performance towards habitual responding, the magnitude of which was predicted by a steeper decline in plasma levels of TRP, the physiological precursor amino acid of 5-HT. This finding is of particular relevance, as it shows that central nervous 5-HT function modulates the balance between goal-directed and stimulus-response habitual systems of behavioral control. In particular, Worbe et al. (2015) used the de Wit methodology to disentangle the role of 5-HT in goal-directed vs habitual action with careful controls for its other actions. They used ATD, which is a widely used translational research method, to lower serotonergic function with a TRP-deficient beverage (Young et al., 1985; Hood et al., 2005; Zepf et al., 2014). The authors showed that after an ATD challenge, subjects increased responding for devalued stimuli during the slip-of-action stage, indicating a devaluation of the outcome without changes in response-outcome learning. This effect implies a shift in the balance of action toward habitual responding during ATD. One useful feature of the present study was the use of several controls for other potential actions of 5-HT. No differences for valuable outcomes were found between groups, in contrast to previous reports suggesting insensitivity to reward value after pharmacological 5-HT reduction (Rogers et al., 2003; Line et al., 2014). Furthermore, ATD had no effect during a control test of response disinhibition, while other studies indicated a dual role of 5-HT in negative affect and behavioral inhibition (Cools et al., 2008)."
This study seems to establish that low serotonin (high dopamine) is key to being able to act according to Ray's motto. High serotonin, on the other hand, was associated with a protocol-like thinking and behavior, which the study calls "flexible, goal-directed responding". The paper also cites studies showing that serotonin is implicated in punishment and behavioral inhibition, as well as guilt, shame and depression.
Btw, I find it funny that they call the "goal-directed responding" "flexible" while the "stimulus-response habitual response" is viewed as rigid and inflexible.
"...Previous studies have yielded contradictory results about the interaction of dopamine (DA) and 5-HT in this balance. It has been suggested that DA biases behavior towards habitual responding, with 5-HT offsetting this phenomenon and directing the balance toward more flexible, goal-directed responding. However, previous research in animals and humans suggests roles for DA in both goal-directed and habitual action (De Wit et al., 2012). Furthermore, 5-HT has been implicated in punishment and behavioral inhibition and, more specifically, a reduced incentive motivation when 5-HT is low (Sanders et al., 2007; Cools et al., 2008; Hebart and Gläscher, 2014). Therefore, the relative and multiple roles of DA and 5-HT in the balance of goal-directed and habitual responding are unclear."
http://ijnp.oxfordjournals.org/content/ ... yv050.full
"...The paper by Worbe et al. (2015), which was recently published in this journal, focuses on the effects of acute tryptophan (TRP) depletion (ATD), a neurodietary physiological method to decrease central nervous 5-HT synthesis in humans for a short period of time, on the balance between hypothetical goal-directed and habitual systems. In this particular study conducted in healthy adult volunteers, a short-term serotonergic deficit induced by ATD was associated with a shift of behavioral performance towards habitual responding, the magnitude of which was predicted by a steeper decline in plasma levels of TRP, the physiological precursor amino acid of 5-HT. This finding is of particular relevance, as it shows that central nervous 5-HT function modulates the balance between goal-directed and stimulus-response habitual systems of behavioral control. In particular, Worbe et al. (2015) used the de Wit methodology to disentangle the role of 5-HT in goal-directed vs habitual action with careful controls for its other actions. They used ATD, which is a widely used translational research method, to lower serotonergic function with a TRP-deficient beverage (Young et al., 1985; Hood et al., 2005; Zepf et al., 2014). The authors showed that after an ATD challenge, subjects increased responding for devalued stimuli during the slip-of-action stage, indicating a devaluation of the outcome without changes in response-outcome learning. This effect implies a shift in the balance of action toward habitual responding during ATD. One useful feature of the present study was the use of several controls for other potential actions of 5-HT. No differences for valuable outcomes were found between groups, in contrast to previous reports suggesting insensitivity to reward value after pharmacological 5-HT reduction (Rogers et al., 2003; Line et al., 2014). Furthermore, ATD had no effect during a control test of response disinhibition, while other studies indicated a dual role of 5-HT in negative affect and behavioral inhibition (Cools et al., 2008)."