The Significant Contribution of Neuroimaging Techniques to Understanding the Anatomy and Functions of the Brain

Neuroimaging has become an invaluable method in many scientific fields, gaining significant power for understanding human brain development and its relationship with behaviour, thoughts, and actions. It is used to test hypotheses about normal developmental processes such as memory, cognitive control, emotion, goal-directed behaviour, social cognition, and language, while also making a major contribution to understanding atypical processes in developmental neuropsychiatric disorders. Among others, the pathophysiology of attention deficit/hyperactivity disorder (ADHD), autism spectrum disorders, schizophrenia, bipolar disorder, obsessive-compulsive disorder, and even anxiety and depressive disorders is investigated using neuroimaging techniques (Rumsey & Ernst, 2009).

Scientific curiosity to understand the human brain, its functionality, and its value for human development led to the creation of neuroimaging techniques, beginning in the 19th century with the ‘human circulation balance’ through to ‘high-density event-related potentials’ (HD-ERP), ‘magnetic resonance imaging’ (MRI), computed tomography (CT), and ‘positron emission tomography’ (PET), and on to functional MRI, which provides the opportunity to follow changes in the developing brain. Neuroimaging techniques allow researchers and clinicians to learn about differences between the normally developing brain and the brain with abnormalities or damage, as well as to show which brain parts are activated during specific activities, behaviours, or emotional states (Rumsey & Ernst, 2009).

In connection with the continuous improvement of neuroimaging techniques and the growing popularity of cognitive science, researchers in the early 1970s introduced a new scientific field called cognitive neuroscience, a term which describes the aim of explaining how mental and cognitive functions arise from brain activity (Wickens, 2009). Cognitive neuroscience encompasses several disciplines which have a direct relationship with the significant contribution of neuroimaging to knowledge about brain development and function.

Studies of language using PET have brought many new findings which have revolutionised previous assumptions about Wernicke’s and Broca’s areas. For instance, measuring blood flow in the cerebral cortex of students performing four language-related tasks led Posner and Raichle (1994) to conclude that the brain area responsible for language has a wider range than previously stated by the Wernicke-Geschwind model (Wickens, 2009). Their findings also inform our understanding of speech comprehension, connecting activity in Wernicke’s area while a participant heard spoken words. However, Wernicke’s area does not participate in reading or generating verbs from nouns. According to Wickens (2009), many studies confirm these statements. Furthermore, several studies using fMRI analysis have found that the area responsible for generating verbs from nouns is Broca’s area (Sahin et al., 2006).

Pulvermüller (2000) revealed findings about brain activity related to the connection between increased activity in the motor cortex controlling a specific body part and a verb related to that body part. The researchers demonstrated an association between leg-related words and activation of the motor cortex controlling leg movements, as well as between face-related words and activation of the face region.

Due to the high difficulty of using fMRI with infants and small children, Electroencephalography (EEG) and Magnetoencephalography (MEG) techniques are used to take measurements, for example, of early language development as well as infant object recognition, processing, and categorisation (Gliga & Mareschal, 2007). EEG and MEG measure the brain’s electrical activity and can be used to monitor the temporal unfolding of object processing in real time (Gliga & Mareschal, 2007).

Infant learning during object exploration and subsequent recognition of these objects, in terms of theta activity, was tested by Begus, Southgate, and Gliga (2015) using EEG. The researchers concluded that while infants were exploring, differences in frontal theta-band oscillations predicted differential subsequent recognition of these objects in a preferential-looking test (Begus et al., 2015). It was concluded that this relationship is not related to the time an infant spent on manual exploration of an object. While behavioural measurements of learning processes in infants, such as visual attention, can yield useful conclusions, it must be underlined that theta activity may lead to many useful discoveries about infant learning development (Begus et al., 2015).

The rapid development of research in various fields of neuroscience, including neurocognitive functions, aims to learn the biological correlates of mental phenomena. Numerous neuroimaging studies have provided rich data that have changed views on brain language control. Very often, PET techniques measure the effects of brain damage in patients with aphasia. PET studies have shown activation of the frontal part of the upper temporal gyrus during a person’s analysis of a compound sentence. It has been shown that damage to this area (Brodmann area 22) leads to impairments in generating the grammatical structure of sentences (Gazzaniga, Ivry, & Mangun, 1998).

Results from studies using MRI techniques show a dramatic increase in total brain volume from birth to the teenage years (Johnson & de Haan, 2015). Despite general assumptions about increasing brain volume, there is dramatic postnatal growth of synapses, dendrites, and fibre bundles (Strelau & Doliński, 2008).

Researchers use functional magnetic resonance imaging (fMRI) to study working memory, mainly focusing on visuospatial working memory (VSWM). Event-related fMRI studies by Kwon et al. (2002) and Klingberg et al. (2002) revealed that the superior frontal sulcus (SFS) and the intraparietal sulcus (IPS), strongly implicated in VSWM in adults, are increasingly engaged over childhood. Olesen et al. (2003), while comparing fMRI and diffusion tensor imaging (DTI) data, concluded that increased fractional anisotropy in fronto-parietal white matter – suggestive of increased strength of anatomical connectivity between these regions – is positively correlated with blood-oxygen-level-dependent (BOLD) activation in the SFS and IPS and with VSWM capacity. Consequently, this led to the conclusion that increased interaction between the SFS and IPS during development is of great importance for improvements in VSWM (Edin et al., 2007).

Olesen, Klingberg, and colleagues (2003) conducted a VSWM study with a distraction period, asking participants to ignore stimuli appearing in different locations on a screen. The researchers found greater SFS activation in children than in adults during the distraction period, whereas decreased SFS activation occurred in VSWM studies with no distracting stimuli. These findings suggest that adults are more effective than children at ignoring irrelevant stimuli (Olesen et al., 2007).

According to Rumsey and Ernst (2009), neuroimaging studies have shown the anterior temporal pole, the medial prefrontal cortex, and the right ventrolateral prefrontal cortex are associated with sadness, with no difference between children and adults in the activated regions. Stuss (1992) suggests the development of the PFC plays a crucial role in the development of emotion regulation. The PFC is among the last areas to mature, a structural change demonstrated by longitudinal MRI studies of humans from childhood to adulthood. Maturation is described as an increased ability to filter and restrain irrelevant information and to react more readily to relevant events. Bunge et al. (2002) propose that the development of increased higher-order cognitive abilities appears during the maturation of the PFC. The researchers concluded that children are more prone to interference effects.

The thesis that understanding the emotions and motives of others is largely automatic and intuitive corresponds to recent neuroimaging data, indicating that brain activity while observing other people’s behaviour, reflecting defined emotions, is very similar to that which occurs when we ourselves experience these emotions. Singer conducted an experiment with 16 emotionally connected couples (Singer et al., 2004). The experiment involved one partner being placed in an fMRI scanner with their brain activity recorded in two situations: 1) when the partner received an unpleasant electrical shock applied by a hand-held electrode and the subject observed the shock on a screen, and 2) when the same person received the shock in the scanner. When this person was in pain, a significant part of the limbic system was activated. Similar activations were recorded when the partners were experiencing pain and the test subjects were only observing them. The fact that the same structures react during real and observed pain may be the basis of empathy, as Singer argues.

Improvements in neuroimaging techniques work together with different fields of medicine, resulting in groundbreaking discoveries. Important discoveries in immunology have broadened understanding of the evaluation of demyelinating disease and its differentiation (Tillema & Pirko, 2013). High-resolution images from MRI have made this technique the most important, next to clinical symptoms, for the prognosis, monitoring, and treatment of demyelinating disease. MRI is performed without exposing the patient to ionising radiation, making it a recognised non-invasive and safe method. Neuroimaging has started to play a very important role in diagnosing multiple sclerosis (MS). Furthermore, the frequent use of MRI in medicine has led to the incidental discovery of radiologically isolated syndrome (RIS), which over time could develop into MS (Tillema & Pirko, 2013). Asymptomatic white matter lesions discovered during RIS diagnosis suggest demyelination (based on radiological criteria). However, these incidental white matter lesions cannot be strictly diagnosed as MS because of the lack of clinical symptoms. Thus, neuroimaging helps differentiate many diseases and symptoms, leading to the discovery of treatments for specific conditions (Leahy & Garg, 2013).

To investigate the causes of autism, many researchers have tested whether there is evidence for dysfunction of mirror neurons or if there is no association with the disorder. People with Autism Spectrum Disorders (ASD) are characterised by deficits in social skills and have problems with communication. Difficulties with proper imitation, theory of mind, language, and even empathy are understood as the most common characteristics of ASD. A study by Oberman et al. (2005) was performed based on the assumption that mirror neuron dysfunction is closely associated with ASD. Therefore, the researchers conducted a study using EEG to test their hypothesis. As Oberman et al. (2005) stated, the reflection of mirror neuron activity can be seen in EEG oscillations in the mu frequency (8–13 Hz) over the sensorimotor cortex. A significant mu suppression was observed while high-functioning individuals with ASD performed self-executed hand movements, thus confirming the hypothesis.

The majority of brain abnormalities associated with developmental disorders are not specific to one disorder. For instance, an atypical cerebellum has been reported for autism, Fragile-X, Williams syndrome (WS), and dyslexia, as shown by researchers using fMRI. Neuroscientists focus on abnormalities shared across several developmental disorders (Johnson & de Haan, 2015).

Research on abnormal mental states using neuroimaging has developed methods to test functional cognitive control, emotional processing, and working memory, in the same way as testing normally developed brain parts without lesions. Using neuroimaging techniques, researchers test damaged brain areas responsible for causing illness (Rumsey & Ernst, 2009).

According to Rumsey and Ernst (2009), many psychiatric neuroimaging studies focus on using these techniques to elucidate the pathophysiology, early detection, and prediction of schizophrenia. Based on the results of a study by Gottesman and Gould (2003), brain changes can be considered endophenotypes strictly associated with schizophrenia, present during every period of the illness. However, this cannot be considered applicable to all major psychotic illnesses. Moreover, issues related to investigating systematic differences in brain structures in the schizophrenic population are caused by the inherent differentiation of its brain structure itself. During the analysis of MRI studies on schizophrenia, researchers account for the effects of drug and alcohol abuse on MRI brain morphology to match patients with similar images.

Pharmacology and treatment for patients with mental illness have been refined due to the valuable use of neuroimaging techniques. For instance, mood-stabilising medication associated with the up-regulation of neurotrophic and neuroprotective factors in the mammalian frontal cortex (Manji et al., 2000) suggests that such medications can protect the brain against abnormal changes and may even reverse the effects of these abnormalities.

Neuroimaging has had a remarkable influence on understanding the functional capabilities of specific brain parts in terms of normal developmental stages as well as pathological changes in brain structure, enabling diagnosis, monitoring, and treatment applicable to specific diseases. Imaging has its origins in the 19th century, and since then, its various techniques have constantly improved. Relatively recently, computerised neuroimaging such as PET, MRI, or fMRI has allowed researchers to study images of the brain non-invasively, to find active parts during specific tasks, to determine which part is responsible for particular behaviours during learning or perception testing, and to consider which part is responsible for a specific disease during brain lesion analysis and clinical symptom assessment, or even in the absence of any asymptomatic abnormalities. There is no doubt that the discovery and continual development of neuroimaging techniques have contributed to many fascinating discoveries regarding brain and body development (Rumsey & Ernst, 2009).