Written By Rianna Tanase
Essential molecules called neurotransmitters, serve as the brain's and nervous system's communication bridges. By transmitting signals between nerve cells, or neurons, these chemicals serve critical roles in mood regulation, motor control, learning, memory, and other essential processes.
The function of neurotransmitter systems in Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) is one complicated and varied aspect of these neurodevelopmental disorders. While our understanding of the underlying neurobiological mechanisms is still evolving, researchers have examined the roles that various neurotransmitters play in the manifestation of symptoms associated with ADHD and ASD.
Below is a summary of the functions that neurotransmitter systems perform in each condition:
SEROTONIN
The neurotransmitter serotonin is linked to mood regulation and social conduct. Its role in the intricate neuro neural pathways of Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) is significant.
In Autism Spectrum Disorder (ASD), serotonin:
Studies on ASD have indicated that changes in serotonin levels may be a factor in the challenges that sufferers with the disorder encounter when interacting with the community. Inability to establish and maintain social relationships is one of the characteristics of ASD, which has been connected to low serotonin levels. Another trait common by people with ASD is repetitive activity, which has similarly been linked to disruptions in serotonin pathways. Mulder et al. (2004), discovered that blood serotonin levels were lower in people with ASD than in neurotypical people.
Serotonin in Attention Deficit/Hyperactivity Disorder (ADHD):
The role of serotonin in ADHD is less understood because research has yielded inconsistent findings. Despite historically trailing dopamine, serotonin is not completely disregarded in ADHD studies. Certain aspects of ADHD symptoms, particularly those related to attention and impulse control, may be made worse by modifications in serotonin function, according to some study. Studies looking at serotonin levels in ADHD sufferers have shown conflicting results. Although certain studies indicate alterations in serotonin function, these findings have not been consistently validated for the entire group of ADHD patients. The varied outcomes of research emphasise the complex interplay of neurotransmitters in ADHD.
DOPAMINE
Dopamine is a neurotransmitter, or chemical messenger, found in the brain and central nervous system that is vital to numerous physiological and psychological functions. It is connected to the brain's reward system, motor control, emotional regulation, learning, attention, and other important processes.
Dopamine deficiency in ASD:
The dopamine equilibrium in the brain is disrupted by variations and mutations in the dopamine transporter (DAT). Research like that done by Gizer et al. (2009) sheds light on the genetic foundations of features associated with ASD that are impacted by dysregulation of dopamine. Animal models have been used to illustrate the complex relationship between hereditary and environmental factors that leads to the development of behaviours similar to ASD.
Dopamine Deficiency in ADHD:
Dopamine, often referred to as the "motivation molecule," plays a pivotal role in initiating and completing tasks. In individuals with ADHD, a dopamine deficiency can lead to challenges in functions such as planning, prioritisation, and sustained attention. Research underscores that individuals with low levels of dopamine may exhibit a tendency to focus more on the difficulty of a task rather than the potential reward associated with its completion. Research
conducted by Volkow et al. (2009) utilising neuroimaging techniques demonstrated lower levels of dopamine receptors in the brains of individuals with ADHD. This finding aligns with the notion that dopamine dysregulation contributes to the challenges in motivation and attention observed in ADHD. The link between dopamine deficiency and difficulties in task initiation and completion further emphasises the central role of dopamine
RATIO BETWEEN GLUTAMATE AND GABA
The neurobiology of Autism Spectrum Disorders (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) is heavily influenced by the complex connections of glutamate and gamma-aminobutyric acid (GABA), two fundamental neurotransmitters. Examining how the ratio of these neurotransmitters influences executive processes, attention management, and behavioural patterns will help us understand the complexities of these medical conditions.
Glutamate and GABA in Focus:
Researchers delved into the prefrontal cortex, the neural command centre responsible for executive functions, to unravel the role of glutamate and GABA. Executive functions encompass planning, organisation, prediction, and attention – critical aspects of cognitive control. An imbalance in the glutamate-to-GABA ratio in this region has been implicated in the manifestation of challenges observed in ASD and ADHD.
In addition to neurotransmission, glutamate and GABA play critical roles in brain development and cognitive function. An overabundance of glutamate in comparison to GABA has been linked to increased hyperactivity and trouble concentrating, both of which are classic symptoms of neurodevelopmental problems.
Prefrontal Cortex and Executive Functions:
To further understand the role of glutamate and GABA, researchers looked into the prefrontal cortex, the brain's command centre for executive functions.
Executive functions include planning, organisation, prediction, and attention, all of which are required for cognitive control. An imbalance in the glutamate-to-GABA ratio in this region has been linked to difficulties associated with ASD and ADHD.
Sensorimotor Areas and GABA Levels:
Researchers discovered reduced GABA levels in ASD-related sensorimotor areas, which may point to a link to altered sensory processing. The correlation between decreased GABA levels and less "filtering" of touch information highlights the unique relationship between neurotransmitter balance and sensory experiences in people with ASD.
GABA, Glutamate, and ADHD Development:
Proper neural development depends on an appropriate balance of GABA and glutamate. Nonetheless, an imbalance could play a role in the emergence of ADHD. Research examining the genetic foundations has shown that differences in glutamate and GABA-related genes are correlated with the severity of symptoms and ADHD. Gao et al. (2017) especially investigated the glutamate-to-GABA ratio in ADHD patients. The results indicated that this ratio was out of balance, supporting the theory that neurotransmitter imbalances play a role in the development of symptoms associated with ADHD. Genetic research has confirmed the link with ADHD, including studies looking at mutations in the glutamate and GABA genes.
OXYTOCIN
The hormone oxytocin, sometimes referred to as the "love hormone" or "bonding hormone," is frequently connected to anomalies in social behaviour and neurodevelopment. The relationship between neurological, environmental, and hereditary factors explains the complex link between oxytocin and neurodevelopmental issues. Even while oxytocin is frequently correlated with emotionality, trust, and social connection, it is affected by a wide range of situational factors that are unique to each individual.
Oxytocin in ADHD:
Contrary to its prominence in social bonding, recent research challenges the notion of a direct association between blood oxytocin levels and ADHD tendencies in healthy adults (Neurosci Lett, 2020). This highlights the complexity of oxytocin's role in ADHD, suggesting that the link between oxytocin and behavioural traits may not be as straightforward in neurotypical individuals.
Oxytocin in ASD:
The data from 31 studies are synthesised in a systematic review that presents a compelling picture of ASD. Children diagnosed with autism spectrum disorder are reported to have lower blood oxytocin levels than their neurotypical counterparts. The present study illustrates the potential significance of oxytocin in the context of ASD, indicating a potential association between low oxytocin levels and the unique social challenges related to ASD. Beyond its physiological effects, oxytocin plays a role in every nuance of social interactions. The relationship between decreased oxytocin levels and reduced social bonding becomes a focus of study in ASD, a condition characterised by social difficulties.
Focused intervention studies are made possible by the increasing amount of research on blood oxytocin levels and autism spectrum disorders. Understanding the precise pathways via which oxytocin influences social behaviour in people with ASD may prove useful in developing new approaches to therapy.
To sum up, neurotransmitter systems are important components of the complex network of neurodevelopmental diseases. They have an impact on several aspects of emotion, behaviour, and mental processes in roles that go beyond traditional ones. Understanding the intricate role that neurotransmitters play in ASD and ADHD can help improve diagnosis, treatment, and, ultimately, the quality of life for individuals who struggle with these neurodevelopmental conditions.
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