Essay Sample on Psychology: Expository Paper

The field of neuroimaging and genetics studies is one of the fastest-advancing medical fields. The technological advances and new research discoveries have fueled a new understanding of the neurology and human genome. One area that has benefited from that new expansion is the understanding of Attention-Deficit/Hyperactivity Disorder (ADHD). According to Bush et al. (2005), functional neuroimaging techniques have begun to provide unprecedented windows on the neurobiology of ADHD. There are four different methods of neuroimaging used to study ADHD that utilize functional MRI, Positron Emission Tomography (PET), Single Photon-Emission Computed Tomography (SPECT), electroencephalography (EEG), and genetic studies to provide information on factors related to ADHD.

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Functional MRI

Functional MRI(f- MRI) is one of the most recent functional imaging methods. According to Bush et al., (2005), the method is advantageous over other functional methods because it is a non-invasive method that does not require exposure to ionizing radiation for the subjects. Functional MRI does not need injections or inhalations. Therefore, it is favorable for repeated use on children hence facilitating longitudinal, developmental, and drug studies. Functional MRI allows for the performance of tasks in either blocked or event-related manner, which gives more flexibility in task design because of its spatial and temporal resolution.

In the short timespan that functional MRI has been around, it has made some significant findings concerning ADHD. A consistent theme in the fMRI literature is the dorsal anterior cingulate cortex (dACC) dysfunction (Bush et al., 2005). The dACC, which is also called “cognitive dysfunction,” plays a significant role in attention, motor control, reward-based decision-making, and cognition. Studies utilizing fMRI found that dACC was hypofunctional in ADHD adults.

PET

PET methods happen to be flow-dependent, but others can measure cerebral metabolism. According to Albajara-Sáenz et al. (2019), PET technology usually provides metabolic and functional information. ADHD-related information from the technology includes dopamine and striatal dopamine neurotransmitters. PET studies on ADHD have focused on identifying dopamine levels in the body. Dopamine has a significant role concerning ADHD in that a dysfunction of the dopaminergic system influences the pathophysiology of the disorder.

Neuropsychological findings related to ADHD that have utilized PET technology have shown that ADHD patients have higher dopamine levels. According to Albajara-Sáenz et al., (2019), an analysis of studies that have utilized PET technology reveals that ADHD groups have 14 percent higher dopamine density than the control groups. However, the PET has been supplanted by the f-MRI because of its superior temporal and spatial resolution.

SPECT

The main difference between SPECT and PET is that the former measures gamma rays, while the latter measures photons and use the information in the creation of internal organs. Photon is a small amount of energy that is produced when positrons react with electrons in the body, to annihilate each other (National Institute of Health, 2016). Although SPECT findings have also focused on the neurotransmitters, (Albajara-Sáenz et al., 2019), the first SPECT studies concentrated on basal ganglia (Albajara-Sáenz et al., (2019). Unfortunately, ADHD studies such as Lou et al. (1998) that use the SPEC technique have been plagued by inadequate or small control group. However, Kim et al., (2001), made a useful contribution by reporting methylphenidate increased regional cerebral blood flow in DLPFC, caudate, and thalamus bilaterally in previously treatment-naïve children and adolescents with ADHD.

EEG

EEG techniques have failed to display the spatial resolution that is necessary for studying brain structures without ambiguity. The technique involves a computer-assisted spectral analysis of the EEG signal, with relative and absolute quantification of the beta, alpha, theta and delta frequencies, and sometimes, measures of coherence (Bush et al., 2005). According to Hughes and John (1999), there are ample studies that have distinguished ADHD subjects from control subjects, with ADHD being characterized by theta excess and beta slowing.

Genetic Studies

There are different perspectives and understandings of how genes cause variation in brain structure and function. According to Faraone and Larsson (2019), genes play a significant role in the etiology of ADHD and its comorbidity with other disorders. Family and twin studies have shown that ADHD runs in the family (Chen et al., 2008). ADHD has a 74 percent heritability, which has inspired the search for susceptibility genes (Faraone and Larsson, 2019). Gene-wide association studies (GWAS) such as Neale et al. (2010) have identified genetic loci at the genome-wide level of statistical significance. According to Faraone and Larsson (2019), genetic studies have indicated that more than thirty percent of ADHD heritability is due to a polygenic component comprising many common variants, each having small effects.

Conclusion

The marriage between neuroimaging and genetic studies has given a new understanding of the causes and treatment of ADHD. PET and SPECT studies have alluded to the relationship between high dopamine content in ADHD patients and previous treatment with stimulants.

References

Albajara Sáenz, A., Villemonteix, T., & Massat, I. (2019). Structural and functional neuroimaging in attentiondeficit/hyperactivity disorder. Developmental Medicine & Child Neurology, 61(4), 399-405.

Bush, G., Valera, E. M., & Seidman, L. J. (2005). Functional neuroimaging of attention-deficit/hyperactivity disorder: a review and suggested future directions. Biological psychiatry, 57(11), 1273-1284.

Chen, W., Zhou, K., Sham, P., Franke, B., Kuntsi, J., Campbell, D., ... & Altink, M. (2008). DSMIV combined type ADHD shows familial association with sibling trait scores: A sampling strategy for QTL linkage. American journal of Medical Genetics part B: Neuropsychiatric Genetics, 147(8), 1450-1460.

Faraone, S.V., & Larsson, H. (2019). Genetics of attention deficit hyperactivity disorder. Mol Psychiatry 24, 562–575. https://doi.org/10.1038/s41380-018-0070-0Hughes J.R, John E.R (1999): Conventional and quantitative electroencephalography

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National Institute of Health. (2016, July). Nuclear Medicine. https://www.nibib.nih.gov/science-education/science-topics/nuclear-medicine.

Kim B.N, Lee, J.S, Cho S.C, Lee D.S (2001): Methylphenidate increased regional cerebral blood flow in subjects with attention-deficit/hyperactivity disorder. Yonsei Med J 42:19 –29.

Lou H.C, Andresen J, Steinberg B, McLaughlin T, Friberg L (1998): The striatum in a putative cerebral network activated by verbal awareness in normals and in ADHD children. Eur J Neurol 5:67–74.

Neale B.M, Medland S, Ripke S, Anney R.J, Asherson P, Buitelaar J, et al. Case-control genome-wide association study of attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc, Psychiatry. 2010;49:906–20.