IYO, What is the role of phasic dopamine vs tonic dopamine in the speech block (i.e., the failure to execute the speech plan)?

IYO, What is the role of phasic dopamine vs tonic dopamine in the speech block (i.e., the failure to execute the speech plan)? As per the title. Refer to the following research studies. Serious responses only, please. Kindly focus on the research findings in your replies. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ [Google search](https://www.google.com/search?q=phasic+vs+tonic+dopamine) (phasic vs tonic dopamine) [Google search ](https://www.google.com/search?q=%22phasic%22+%22dopamine%22+%22stuttering%22)("phasic" "dopamine" "stuttering") [Per Alm ](https://pubmed.ncbi.nlm.nih.gov/34924974/)(Phd): (The Dopamine System and Automatization of Movement Sequences: A Review With Relevance for Speech and Stuttering) >*"The review indicates that a primary mechanism for the automatization of movement sequences is the merging of isolated movements into chunks that can be executed as units. In turn, chunks can be utilized hierarchically, as building blocks of longer chunks. It is likely that these mechanisms apply also to speech, so that frequent syllables and words are produced as motor chunks. It is further indicated that the main learning principle for sequence learning is reinforcement learning, with the phasic release of dopamine as the primary teaching signal indicating successful sequences. It is proposed that the dynamics of the dopamine system constitute the main neural basis underlying the situational variability of stuttering."* [Oren Civier and Frank H Guenther](https://pmc.ncbi.nlm.nih.gov/articles/PMC3775364/): (Computational modeling of stuttering caused by impairments in a basal ganglia thalamo-cortical circuit involved in syllable selection and initiation) [VRT hypothesis](https://www.researchgate.net/publication/352029918_STUTTERING_DOPAMINE_AND_INCENTIVE_LEARNING): (Stuttering, dopamine, and incentive learning) >*"In this appendix, I discuss some recent developments in my understanding of the role that dopamine plays in enabling us to respond appropriately to the various stimuli we encounter in our lives, and I propose that phasic fluctuations in synaptic dopamine may play a key role in the moment-to-moment regulation of the availability of our speech plans for motor execution.*" [Per Alm](https://www.sciencedirect.com/science/article/abs/pii/S0021992404000280): (Stuttering and the basal ganglia circuits: a critical review of possible relations) > *"The dopamine neurons in the substantia nigra pars compacta (SNc) project to the striatum, providing a dense dopaminergic input. Normally these neurons have a tonic firing rate, providing a low, well-regulated, extracellular level of dopamine (Schultz, 1998). An interesting aspect is that the dopamine neurons have been found to show rapid variations of their firing rate according to the situation. Increased release of dopamine in the striatum has been shown to strengthen active synapses between cortical and striatal neurons, and to facilitate learning of behaviors (Reynolds et al., 2001).* >*The reward prediction error model states that the dopamine neurons vary their firing rate in relation to prediction of rewards. Events that are more rewarding than predicted will increase the release of dopamine, while omission of a predicted reward will lead to reduction of dopamine release. These errorrelated responses of the dopamine neurons would make them suited to constitute a teaching signal for learning of behavioral responses, with strengthening of behaviors that were more rewarding than predicted and weakening of behaviors that failed to produce the predicted reward.* >*This model of dopamine variation might be relevant for automatization of speech motor patterns, since (a) reward-related variation in the dopamine release has been found in the putamen (Schultz, 2000), which is the sensorimotor region of the striatum, and (b) simulation of a neural network indicates that the reward-related changes of dopamine release constitute an excellent teaching signal for learning of sequential movements (Suri & Schultz, 1998). Such a mechanism would be of interest in relation to the development and treatment of stuttering. A negative emotional experience of stuttering could be described as an event that was less rewarding than predicted, thereby reducing dopamine release and weakening the motor program for the intended speech sequence that failed. This mechanism might result in a ‘‘vicious circle,’’ where negative experiences of stuttering lead to increased stuttering. On the other hand, positive emotional experiences of a functional speech pattern would tend to strengthen the automaticity of this pattern."* [Usler ](https://scholar.google.com/citations?view_op=view_citation&hl=en&citation_for_view=hpaHKlYAAAAJ:5nxA0vEk-isC)(Phd): (An Active Inference Account of Stuttering Behavior) >*"Active inference, a predictive processing theory of sentient behavior, provides a potential account for understanding the core behaviors and diverse phenomena of stuttering. Stuttering likely arises from disruptions in action-perception cycling that facilitate the fluent sequential production of syllables. More specifically, aberrantly high sensory precision to speech-related predictions may cause the abrupt inhibition of syllable initiation, resulting in the hallmark stuttering ‘block.’ Moreover, active inference elucidates the perplexing contextual variability of stuttering behavior, such as the effects of adaptation, consistency, and distraction. Importantly, this account holds significant clinical implications for stuttering treatment, offering novel avenues for intervention."* [Belujon and Anthony A. Grace](https://royalsocietypublishing.org/doi/10.1098/rspb.2014.2516): (Regulation of dopamine system responsivity and its adaptive and pathological response to stress) >"*DA neurons display an irregular, single-spike firing pattern (or ‘tonic’ activity), as well as a burst firing pattern (or ‘phasic’ activity) \[43,44\]. The phasic pattern is dependent on glutamatergic afferent input \[44\], in particular those arising from the pedunculopontine tegmentum (PPTg) \[45\]. Phasic burst firing is believed to be the behaviourally salient output of the DA system that modulates goal-directed behaviour (for review, see \[39\]), and phasic changes in bursting occur in response to a conditioned stimulus, or after a primary reward, and have been shown to mediate prediction error response in conscious primates \[46\] and rats \[47\]. Although spontaneous motor behaviour is absent and sensory processing is dampened in anaesthetized animals, and burst discharge to a stimulus response is non-existent, as shown during the deep sleep phase in cats \[48\], burst properties and tonic discharge and their regulation are comparable with those observed in behaving animals \[49,50\]. It should be noted that in anaesthetized rats, burst discharge has been observed in response to a visual stimulus after disinhibition of the superior colliculus \[51\]. Moreover, in awake behaving animals, spontaneous bursts have the same properties as bursts produced in response to a stimulus \[49\]. In addition, drugs that block burst firing, such as NMDA antagonists injected into the VTA \[52\], also interfere with learned responses \[53\]. Therefore, spontaneous bursts studied in anaesthetized animals are analogous in form and regulation with bursts produced in response to a stimulus in awake behaving animals."* [Arnold et al](https://academic.oup.com/cercor/article/26/4/1539/2367130): (Dopaminergic Modulation of Cognitive Preparation for Overt Reading: Evidence from the Study of Genetic Polymorphisms) *"Conclusions* *Intermediate levels of mesocortical dopaminergic neuromodulation facilitate preparatory interactions between the mPFC and the dorsal striatum during task-set generation for overt speaking. However, cognitive processes that underlie the generation of affective prosody and engage the left IFG show linear effects that relate more directly to a negative interaction between prefrontal tonic and subcortical phasic dopamine. Thus, intermediate dopamine levels in mesial prefronto-striatal loops ensure a balance between cognitive flexibility and stability in setting up and maintaining task-sets. If additional cognitive flexibility is required, lateral prefrontal cortices are more easily recruited in case genetic polymorphisms favor cortical tonic and subcortical phasic dopamine signaling. Finally, functional COMT Val158Met effects are not restricted to cognitive processes involving prefrontal cortices, but are also observed in the sensorimotor speech system in which dopamine may gate temporal integration of auditory feedback in addition to its well-known effects in motor control.*"