Essay Sample on Neuroimaging and Autism Spectrum Disorder: Impact of Subcortical Structures

Introduction

Today, it is estimated that Autism spectrum disorder (ASD) affects one in every 59 children in the U.S. (Autism and Developmental Disabilities Monitoring Network, 2018). Autism spectrum disorder (ASD) is a neurodevelopmental disorder which is characterized by restricted repetitive behaviours (RRBs) and continuous deficits in social communication. Recently, neuroimaging studies suggest that subcortical structures impact sensorimotor learning and control, and are linked with Autism spectrum disorder. Subcortical structures are a unit of different neural forms deep within the brain, which comprise limbic structures, pituitary glands, basal ganglia, thalamus, cerebellum, and diencephalon. They are involved in complex actions such as emotion, pleasure, memory, and hormone production. As such, they are the information hub of the nervous system. They modulate and relay information that passes through various parts of the brain. Moreover, there is a flexible association between the environment and the brain creating the basis for our learning ability. All creatures including people acquire information about the environment through sensory organs such as skin, tongue, nose, eyes, ears, etc., and react to stimuli by carrying out some actions with muscle movements in some instances. Hence, sensorimotor learning and control are a person's capability to interrelate with the surrounding by translating the sensory world and reacting to it with the motor system. The smoothness or efficacy of the action improves with practice, which is sensory-motor learning and control. The paper aims to critically evaluate whether subcortical and deep-brain structures influence sensorimotor learning and control, and connected with Autism spectrum disorder.

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Subcortical Structures Influences on Sensorimotor Learning and Control

Motor Control

Sensorimotor learning is imperative for daily behaviour. It is used for learning new skills and maintaining retained behavioural capabilities. It is regulating a person's movement through the nervous system. People learn how to move a cursor on a laptop screen. Due to sensory areas slow feedback, the brain has formed the ability to predict (Lalazar & Vaadia, 2008). Most of the human behaviours are modified via sensorimotor learning (Makino et al., 2016). For instance, to brake a car while driving in traffic an individual require to know the skill to approximate the traffic flow. As such, when a person notes the traffic slowing, the visual data initiates a motor reaction to brake the car. People also learn the skill of smoothly controlling the brake. As shown by this example, even relatively easy behaviours include a multi-level learning process. As such, there are neural changes that occur during sensorimotor learning. According to Makino et al., (2016) the brain must select a circuit that can dependably form the target movement. Thus, studies have implicated cerebellum and basal ganglia for the choice of suitable motor movement (Makino et al., 2016). Specifically, the cerebellum facilitates learning founded on error signals, while basal ganglia specialize in reinforcing learning. Therefore, it is the combined efforts of these subcortical structures that permit the selection of an appropriate target behaviour and corresponding circuit.

Imitating

Speech is one of the dynamic sensorimotor skills, and vocal learning engages both the cerebellum and the basal ganglia. Human infants learn to talk by imitating the talking of other people around them. With time, they know how to harmonize the movements of their breathing muscles and vocal cords to create particular sounds. Young aspiring singers go via the same process to learn singing. Therefore, similar brain regions including, cortex, basal ganglia, and cerebellum enhance vocal learning in aspiring musicians and infants. According to Pidoux et al., (2018), these subcortical structures implicitly relate through their specific loops with brainstem networks and thalamocortical. Besides, they also interact directly through subcortical pathways. However, in vocal learning cerebellum presents a robust effort to a song linked basal ganglia in the nucleus in zebra finches. The study posits that cerebellar signs are conveyed to the basal ganglia through a disynaptic connection via the thalamus and transmitted to the premotor nucleus that controls song production and to their cortical target (Pidoux et al., 2018). Further, cerebellar lesions weaken young people's song learning. As such, subcortical interactions between basal ganglia and cerebellum contributes to sensory learning and control. Basal ganglia and cerebellum help people learn and perform movements.

Movements Planning

Motor movement is the movement of muscles with the aim of carrying out a particular action. Basal ganglia are embroiled in the planning of a movement based on the memory of either the outcome or movement, but the cerebellum is more directly implicated in consideration of movement execution changes. As such, feedback control helps the motor network to respond to the sensory effort that shows the different forms of the planned movement. An experiment to classify brain parts that are engaged in learning by trial and error found that throughout motor learning there were alterations in the chance of moving at a certain point in the sequence and also there were adjustments in the variability of the response times and the mean response times (Jueptner et al., 1997). As such, the study established that basal ganglia perform a part in specifying the movement in planning, retention, or selection of the movement to be done (Jueptner et al., 1997). However, the study shows that the cerebellum is directly engaged with the parameters of performing movements than the basal ganglia. The study established that there is a significant relationship between the cerebellum degree of activation and the rate of psychomotor movements (Jueptner et al., 1997). Thus, the outcomes imply that cerebellum action is more closely connected to the psychomotor skills than basal ganglia. This is in line with other studies that established that micro-stimulations create movements if applied to the cerebellum area, nut not the basal ganglia area (Buford et al., 1996).

Motor Learning

Motor learning explains how people acquire motor skills. Neuroscience research has assisted to show the crucial nature of behaviours influenced or controlled by the limbic structures. According to Umphred & West (2001), limbic network and cognitive impairment involvement can cause many errors in the motor responses even though the motor system is intact. Therefore, developing a probable set of complex behavioural responses to the external and internal influences; this alertness is relayed to an ascending pathway through the thalamus, the limbic structures, and the cerebral cortex (Umphred & West, 2001). As such, to move from the general arousal state to the selecting movement requires transmission of information to and from the limbic network, thalamus, and cortex. Therefore, there is intertwining dependence among cognitive skills and limbic essential for any kind of learning and the simultaneous, sequential, and multiprogramming of motor movement (Umphred & West, 2001). People need to analyze correctly their external and internal environment requiring action on a task. Brooks (1986) posits that the limbic system assists in motor learning. Hence, interactions between the sensorimotor-related systems are important for learning what to do in a motor task and how to do it appropriately (Brooks, 1986). The limbic structures create a need-directed motor activity and communicate the intent through the motor system, which is a crucial step in normal motor function.

At the subcortical level, the cerebellum, and basal ganglia are interconnected. The dentate nucleus in the cerebellum is the cause of dense disynaptic projection to the striatum (Bostan & Strick, 2018). Similarly, the subthalamic nucleus in the basal ganglia is the basis of the dense disynaptic projection of the cerebellar cortex. A study found that the cerebral cortex, cerebellum, and the basal ganglia form an integrated network (Bostan & Strick, 2018). Thus, this system is well structured so that the affective, motor and cognitive areas of every node in the system are unified. As such, this indicates why abnormal action at any node can have system-wide impacts.

Autism Spectrum Disorder

ASD involves various brain abnormalities. Disorders within this spectrum are distinguished by a deficit in communication and social skills, repetitive and stereotyped behaviour and a broad range of deficits in cognitive functions (Rogers et al., 2013). A study found that participants with ASD exhibited enhanced working connectivity between subcortical structures that is basal ganglia and thalamus, and primary sensory system (Cerliani et al., 2015). A higher score of such connections was related to the acuteness of autistic behaviours. As such, impairments that are related to ASD in the connection between subcortical areas and primary sensory cortices imply that the sensory processes they abnormally subserve affect the brain's ability to process information in people with the condition (Cerliani et al., 2015). Thus, this leads to hypersensitivity or hyposensitivity and problems in regulating an individual's behaviour.

Contemporary studies suggest that abnormalities of the cerebellum that are involved in the prefrontal cortex and cognitive function significantly influence autism. Autism is caused by several factors such as genetics, perinatal or prenatal environment. According to Hallmayer (2011), approximately 61-90%n of people inherit autism. However, despite the etiology, the developmental pathology of the cerebellum enacts a key part in ASD and autism. According to Rogers et al., (2013) impaired cerebello-cortical circuit underlies ASD symptoms. Some autistic rodents models applied in the study show behavioural and cerebellar irregularities that are similar to those commonly spotted in individuals diagnosed with autism (Rogers et al., 2013). As such, this study provides an improved comprehension of the neurochemical and the behavioural effect of alterations in the cerebello-cortical system in autism. Research evidence indicates that the cerebellum also performs an active role in cognitive function. In patients diagnosed with ASD their cerebellum is functionally and structurally abnormal (Rogers et al., 2013). Besides, disorders that have similar symptoms with autism also have genetic mutations linked with anomalous cerebellar development (Hallermayer, 2011). Other disorders that are linked with cerebellar abnormalities within the autism spectrum include Asperger's syndrome connected with low gray matter volume and low cerebellar volume (Rogers et al., 2013). Therefore, in ASD spectrum cerebellum is functionally abnormal and therefore, directly associated with autistic symptoms.

Irregularities of the thalamus are related to autism. In people, without any neuro problems, total brain volume is significantly associated with the volume of the thalamus (Rogers et al., 2013). However, in people diagnosed with ASD, this correlation does not exist. As such, the volume of the thalamus in autism spectrum individuals decreases. Thus, thalamus plays a role in motor abnormalities as reported in previous studies.

In the autism spectrum disorders, both the cerebellum and basal ganglia are affected in their motor and non-motor systems. In people developing normally, the basal ganglia perform a key function in movement coordination, sensory modulation and processing, eye movement, action chaining, inhibition control, and eye-hand coordination. However, in auti...