scholarly journals Dopamine role in learning and action inference

2019 ◽  
Author(s):  
Rafal Bogacz
Keyword(s):  
Basal Ganglia ◽  
Dopaminergic Neurons ◽  
Habit Formation ◽  
Action Planning ◽  
Mammalian Brain ◽  
Prediction Errors ◽  
Dopamine Depletion ◽  
Motor Plan ◽  
Directed System ◽  
Different Parts

AbstractThis paper describes a framework for modelling dopamine function in the mammalian brain. In this framework, dopaminergic neurons projecting to different parts of the striatum encode errors in predictions made by the corresponding systems within the basal ganglia. These prediction errors are equal to differences between rewards and expectations in the goal-directed system, and to differences between the chosen and habitual actions in the habit system. The prediction errors enable learning about rewards resulting from actions and habit formation. During action planning, the expectation of reward in the goal-directed system arises from formulating a plan to obtain that reward. Thus dopaminergic neurons in this system provide feedback on whether the current motor plan is sufficient to obtain the available reward, and they facilitate action planning until a suitable plan is found. Presented models account for dopaminergic responses during movements, effects of dopamine depletion on behaviour, and make several experimental predictions.

scholarly journals Dopamine role in learning and action inference

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Rafal Bogacz
Keyword(s):  
Basal Ganglia ◽  
Dopaminergic Neurons ◽  
Habit Formation ◽  
Action Planning ◽  
Mammalian Brain ◽  
Prediction Errors ◽  
Dopamine Depletion ◽  
Directed System ◽  
The Difference ◽  
Different Parts

This paper describes a framework for modelling dopamine function in the mammalian brain. It proposes that both learning and action planning involve processes minimizing prediction errors encoded by dopaminergic neurons. In this framework, dopaminergic neurons projecting to different parts of the striatum encode errors in predictions made by the corresponding systems within the basal ganglia. The dopaminergic neurons encode differences between rewards and expectations in the goal-directed system, and differences between the chosen and habitual actions in the habit system. These prediction errors trigger learning about rewards and habit formation, respectively. Additionally, dopaminergic neurons in the goal-directed system play a key role in action planning: They compute the difference between a desired reward and the reward expected from the current motor plan, and they facilitate action planning until this difference diminishes. Presented models account for dopaminergic responses during movements, effects of dopamine depletion on behaviour, and make several experimental predictions.

The Relative Vascularity of Different Areas of the Mammalian Brain

1937 ◽  
Vol 83 (346) ◽  
pp. 510-511 ◽  
Author(s):  
A. Colin P. Campbell
Keyword(s):  
Nervous System ◽  
Basal Ganglia ◽  
Rat Brain ◽  
Cerebellar Cortex ◽  
Extensive Study ◽  
Mammalian Brain ◽  
Rabbit Brain ◽  
Human Brains ◽  
The Brain ◽  
Different Parts

Though many of the earlier workers made statements based on general impressions from injected preparations about the relative vascularity of different parts of the brain, only comparatively recently has an attempt been made to measure and express numerically the capillary development in different areas, by methods similar to those used by Krogh in studying the vascularity of muscle. Craigie has made an extensive study of the rat brain by such methods, Cobb, and Cobb and Talbot have investigated certain areas of the rabbit brain, and Dunning and Wolf certain parts of the nervous system of the cat. In the present paper a personal investigation (undertaken at the suggestion of Dr. Cobb) is reported, comparing the basal ganglia, cerebral and cerebellar cortex of the cat as regards capillary vascularity. The capillaries were demonstrated by Indian ink injection, and results expressed in millimetres of capillary per cubic millimetre of tissue. Substantiating observations were made on similar areas of monkey and human brains, but without attempting accurate measurement as in the cat material.

Dynamic Changes in the Cortex-Basal Ganglia Network After Dopamine Depletion in the Rat

2008 ◽  
Vol 100 (1) ◽  
pp. 385-396 ◽  
Author(s):  
Cyril Dejean ◽  
Christian E. Gross ◽  
Bernard Bioulac ◽  
Thomas Boraud
Keyword(s):  
Basal Ganglia ◽  
Local Field ◽  
Signal Transmission ◽  
Local Field Potentials ◽  
Cellular Level ◽  
Cortical Activation ◽  
Field Potentials ◽  
Dopamine Depletion ◽  
Indirect Pathway ◽  
Before And After

It is well established that parkinsonian syndrome is associated with alterations in the temporal pattern of neuronal activity and local field potentials in the basal ganglia (BG). An increase in synchronized oscillations has been observed in different BG nuclei in parkinsonian patients and animal models of this disease. However, the mechanisms underlying this phenomenon remain unclear. This study investigates the functional connectivity in the cortex-BG network of a rodent model of Parkinson's disease. Single neurons and local field potentials were simultaneously recorded in the motor cortex, the striatum, and the substantia nigra pars reticulata (SNr) of freely moving rats, and high-voltage spindles (HVSs) were used to compare signal transmission before and after dopaminergic depletion. It is shown that dopaminergic lesion results in a significant enhancement of oscillatory synchronization in the BG: the coherence between pairs of structures increased significantly and the percentage of oscillatory auto- and cross-correlograms. HVS episodes were also more numerous and longer. These changes were associated with a shortening of the latency of SNr response to cortical activation, from 40.5 ± 4.8 to 10.2 ± 1.07 ms. This result suggests that, in normal conditions, SNr neurons are likely to be driven by late inputs from the indirect pathway; however, after the lesion, their shorter latency also indicates an overactivation of the hyperdirect pathway. This study confirms that neuronal signal transmission is altered in the BG after dopamine depletion but also provides qualitative evidence for these changes at the cellular level.

scholarly journals Changes in excitability properties of ventromedial motor thalamic neurons in 6-OHDA lesioned mice

2020 ◽  
Author(s):  
Edyta K Bichler ◽  
Francesco Cavarretta ◽  
Dieter Jaeger
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Basal Ganglia ◽  
Potassium Current ◽  
Cellular Level ◽  
Inhibitory Input ◽  
Dopamine Depletion ◽  
Thalamic Nuclei ◽  
Adult Mice ◽  
Motor Thalamus

AbstractThe activity of basal ganglia input receiving motor thalamus (BGMT) makes a critical impact on motor cortical processing, but modification in BGMT processing with Parkinsonian conditions have not be investigated at the cellular level. Such changes may well be expected due to homeostatic regulation of neural excitability in the presence of altered synaptic drive with dopamine depletion. We addressed this question by comparing BGMT properties in brain slice recordings between control and unilaterally 6-OHDA treated adult mice. At a minimum of 1 month post 6-OHDA treatment, BGMT neurons showed a highly significant increase in intrinsic excitability, which was primarily due to a decrease in M-type potassium current. BGMT neurons after 6-OHDA treatment also showed an increase in T-type calcium rebound spikes following hyperpolarizing current steps. Biophysical computer modeling of a thalamic neuron demonstrated that an increase in rebound spiking can also be accounted for by a decrease in the M-type potassium current. Modeling also showed that an increase in sag with hyperpolarizing steps found after 6-OHDA treatment could in part but not fully be accounted for by the decrease in M-type current. These findings support the hypothesis that homeostatic changes in BGMT neural properties following 6-OHDA treatment likely influence the signal processing taking place in basal ganglia thalamocortical processing in Parkinson’s disease.Significance StatementOur investigation of the excitability properties of neurons in the basal ganglia input receiving motor thalamus (BGMT) is significant because they are likely to be different from properties in other thalamic nuclei due to the additional inhibitory input stream these neurons receive. Further, they are important to understand the role of BGMT in the dynamic dysfunction of cortico – basal ganglia circuits in Parkinson’s disease. We provide clear evidence that after 6-OHDA treatment of mice important homeostatic changes occur in the intrinsic properties of BGMT neurons. Specifically we identify the M-type potassium current as an important thalamic excitability regulator in the parkinsonian state.

scholarly journals Effects of Dopamine Depletion on Network Entropy in the External Globus Pallidus

2009 ◽  
Vol 102 (2) ◽  
pp. 1092-1102 ◽  
Author(s):  
Ana V. Cruz ◽  
Nicolas Mallet ◽  
Peter J. Magill ◽  
Peter Brown ◽  
Bruno B. Averbeck
Keyword(s):  
Basal Ganglia ◽  
Globus Pallidus ◽  
Dopamine Depletion ◽  
Information Coding ◽  
Logistic Regression Models ◽  
Firing Rates ◽  
Before And After ◽  
Network Entropy ◽  
Coding Capacity

Dopamine depletion in cortical-basal ganglia circuits in Parkinson's disease (PD) grossly disturbs movement and cognition. Classic models relate Parkinsonian dysfunction to changes in firing rates of basal ganglia neurons. However, disturbances in other dynamics of neural activity are also common. Taking both inappropriate firing rates and other dynamics into account and determining how changes in the properties of these neural circuits that occur during PD impact on information coding are thus imperative. Here, we examined in vivo network dynamics in the external globus pallidus (GPe) of rats before and after chronic dopamine depletion. Dopamine depletion led to decreases in the firing rates of GPe neurons and increases in synchronized network oscillations in the β frequency (13–30 Hz) band. Using logistic regression models, we determined the combined and separate impacts of these factors on network entropy, a measure of the upper bound of information coding capacity. Importantly, changes in these features in dopamine-depleted rats led to a significant decrease in GPe network entropy. Changes in firing rates had the largest impact on entropy, with changes in synchrony also decreasing entropy at the network level. Changes in autocorrelations tended to offset these effects because autocorrelations decreased entropy more in the control animals. Thus it is possible that reduced information coding capacity within basal ganglia networks may contribute to the behavioral deficits accompanying PD.

scholarly journals Subsecond dopamine fluctuations in human striatum encode superposed error signals about actual and counterfactual reward

2015 ◽  
Vol 113 (1) ◽  
pp. 200-205 ◽  
Author(s):  
Kenneth T. Kishida ◽  
Ignacio Saez ◽  
Terry Lohrenz ◽  
Mark R. Witcher ◽  
Adrian W. Laxton ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Decision Making ◽  
Parkinson's Disease ◽  
Animal Models ◽  
Large Body ◽  
Reward Processing ◽  
Dopamine Neurons ◽  
Model Organisms ◽  
Mammalian Brain ◽  
Prediction Errors

In the mammalian brain, dopamine is a critical neuromodulator whose actions underlie learning, decision-making, and behavioral control. Degeneration of dopamine neurons causes Parkinson’s disease, whereas dysregulation of dopamine signaling is believed to contribute to psychiatric conditions such as schizophrenia, addiction, and depression. Experiments in animal models suggest the hypothesis that dopamine release in human striatum encodes reward prediction errors (RPEs) (the difference between actual and expected outcomes) during ongoing decision-making. Blood oxygen level-dependent (BOLD) imaging experiments in humans support the idea that RPEs are tracked in the striatum; however, BOLD measurements cannot be used to infer the action of any one specific neurotransmitter. We monitored dopamine levels with subsecond temporal resolution in humans (n = 17) with Parkinson’s disease while they executed a sequential decision-making task. Participants placed bets and experienced monetary gains or losses. Dopamine fluctuations in the striatum fail to encode RPEs, as anticipated by a large body of work in model organisms. Instead, subsecond dopamine fluctuations encode an integration of RPEs with counterfactual prediction errors, the latter defined by how much better or worse the experienced outcome could have been. How dopamine fluctuations combine the actual and counterfactual is unknown. One possibility is that this process is the normal behavior of reward processing dopamine neurons, which previously had not been tested by experiments in animal models. Alternatively, this superposition of error terms may result from an additional yet-to-be-identified subclass of dopamine neurons.

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