Contributions of Dopamine to Vocal Learning

Introduction:

It has been hypothesized that the presence of learning stimuli improves understanding since it is a well-known theory that midbrain dopamine (DA) neurons in mammals behave differently when exposed to stimuli compared to the predicted behavior. Therefore, the study has been designed to ascertain whether or not DA encourages learning potentially boosting knowledge. The songbird was chosen as a test subject because researchers were interested in its vocal development and behavioral traits. The birds were subjected to noise training, and it was investigated to determine if prelesion and postlesion had any impact on the variety of their voice or the number of songs they sang each day. Data analysis was carried out quantitatively analyzing the behavior of the songbird with regard to voice variation and number of songs as per the experiments.

Hypothesis goals:

To establish a possible cause to reinforcement learning

To study the impact of Dopamine (DA) in sensor motor learning

To establish the impact of DA in vocal learning

Analysis:

Since the NE concentrations were less than the NE concentrations in the sham hemisphere by 2%, added to the fact that the injection of 6-OHDA did not affect the hemispheres shows that noradrenergic inputs input did not influence the findings from the study.

6-OHDA did not have any effect on neuronal stomata of area X while on the sham injections it had. 6-OHDA reduces the effect of dopaminergic inputs and has no negative effect on the neuronal cells within the basal ganglia. Lesion effect on the loss of dopaminergic neurons

Examination of lesion induction to the loss of dopaminergic neurons shows done by counting TH-positive cell bodies in the midbrain VTA/SNc compared to the effect of a lesion on noradrenergic neurons established through counting the TH-positive cells in LC cells showed no significant change with a p-value of p > 0.8. The post hoc tests, however, showed that the loss of TH-positive neurons caused by the injection of 6-OHDA, is not statistically significant due to a reliance on a very small representative sample of 0.1 and could be taken to occur by chance.

The loss of dopaminergic innervations in area X:

The loss of dopaminergic innervations in area X had no effect on the quality of the song meaning that 6-OHDA did not affect the number of songs sang and that any change is not statistically significant and can be said to occur by chance since the p-value is > 0.05.

The structure of the song was also not affected by lesions since it remained the same for a bird a particular bird before and after injection with a lesion. 6-OHDA caused has inconsistent change that cannot be accounted for statistically in syllable pitch.

An increase in DA in area X in female samples reduces acoustic variability there is a possibility that reducing DA with 6-OHDA is likely to increase the variability even more.

Since Parkinson's disease leads to reduced vocal variability, 6-OHDA lesions are highly likely to reduce vocal variability.

There was no effect of the pitch by prelesion at p < 0.05 value indicating highly significant.

Therefore, although 6-OHDA lesions lead to 50% decrease in DA, there is no significant evidence to show that it led to acoustic variability.

6-OHDA reduces learning by far at about > 50% as compared with learning on based on sham injections.

6-OHDA lesioned birds also significantly reduce learning as compared to sham-lesioned birds.

The size location of lost dopaminergic within area X was found not to be related to the TH stain reduction.

Evaluation:

The small dataset is likely to yield unreliable results leading to the wrong inferences and conclusions.

The limitation of the number of songs produced per day which was a limitation to the study likely to yield the wrong results.

The use of 6-OHDA impeded the research since lesions were only confined to specific locations.

The process of learning was impaired to that of voice variability and the two are negatively correlated.

Strengths of the study:

The study was undertaken with the necessary high technological techniques required to extract the most accurate results.

The use of a songbird was high re-study recommended since t is was readily available and allowed by the Emory University Animal Care and Use Committee.

The statistical tests are very powerful and the power was high and likely to provide accurate results.

The methodology and procedure were well organized and lead well to conclusions.

Weaknesses of Study:

The chemicals used in the experiment were counter reacting resulting into wrong results and eventually the wrong results and conclusions.

The design involved so many complex parameters making it difficult to draw the lines between interactions and to infer the findings and conclusions.

Works Cited

Ali F, Otchy TM, Pehlevan C, Fantana AL, Burak Y, O¨ lveczky BP (2013) The basal ganglia is necessary for learning spectral, but not temporal, features of birdsong. Neuron 80:1–13.

CrossRef Medline Andalman AS, Fee MS (2009) A basal ganglia-forebrain circuit in the songbird biases motor output to avoid vocal errors. Proc Natl Acad Sci U S A 106:12518 –12523.

Kang UJ, Zhuang X (2010) Dopamine-dependent motor learning insight into Levodopa’s long-duration response. Ann Neurol 67:639 –647. CrossRef Medline Bottjer SW, Altenau B (2010)

Parallel pathways for vocal learning in basal ganglia of songbirds. Nat Neurosci 13:153–155.

CrossRef Medline Brainard MS, Doupe AJ (2000) Interruption of a basal ganglia-forebrain circuit prevents plasticity of learned vocalizations. Nature 404:762–766. CrossRef Medline

Canopoli A, Herbst JA, Hahnloser RH (2014) A higher sensory brain region is involved in reversing reinforcement-induced vocal changes in a songbird.