Cognitive Neuroscientists use a variety of imaging technologies to view the structure and function of the brain. By this, the origin of mental processes and behaviour can be inferred. Although many behaviours are learned through experience and environmental factors, our biology plays a critical part in the origin of such behaviours. Techniques such as TMS, MEG, PET and EEG are a few of many techniques used to investigate this. The main arguments to be explored are what research methods are and what they entail, and what can these methods tell us about the biological bases of behaviour and mental processing.
The first potential research method which can be used to investigate biological basis of behaviour is TMS. Transcranial Magnetic Stimulation is a modern brain stimulation technique (Martin, Carlson & Buskist, 2013). TMS is frequently used to treat mood disorders such as depression (Shubin, Segal, Smith & Robinson, 2019). The process of TMS involves placing an electromagnetic coil on the scalp, temporarily activating areas of the brain by passing electrical currents through the brain. Application of multiple electrical pulses is called repetitive TMS. The magnetic pulses travel through the skull and stimulate brain cells which can improve communication different areas in the brain. Positively, TMS is a non-invasive treatment, as well as not requiring any type of medication/anaesthesia prior to the process (Smith, 2019). Therefore, we could suggest people are more likely to attend their sessions as fears may arise from invasive procedures. However, as a drawback of this treatment includes the time that’s required for it, which is up to 30 sessions over a 6-week period (Shubin et al, 2019). Patients may feel this to be an inconvenience in their day-to-day lives. Minor physical disadvantages occur from TMS, such as skin redness at site of the coil’s placement, and mild discomfort such as headache. In addition, a main usage of TMS is to study localisation of function. As this technique stimulates brain cells, as well as being able to temporarily lesion certain areas (Shubin et al, 2019), we can correlate these findings to investigate the biological basis of behaviour. For example, it was suggested that people who listen to speech may comprehend what a speaker is saying when his/her articulatory gestures are activated. Using TMS, Fadiga, Craighero, Buccino & Rizzolatti (2002) found that there was an increase of motor-evoked potentials recorded from participants tongue muscles (during speech listening) when the words heard strongly involved tongue movements. This is known as the motor theory of speech perception (Liberma & Mattingly, 1985). The use of TMS here was able to infer a link between the mental process of speech perception and our behaviour, with the (magnetic) stimulation of the motor cortex.
Secondly, MEG scans are a research method which could be used to investigate biological basis of behaviour. Magnetoencephalography measures brain function. This technique involves using a SQUID (superconducting quantum interference device) which is immersed in liquid helium, to detect activity of magnetic fields generated by neurons (Martin et al 2013). It’s used to localise sources of activity, which is later plotted on a 3D image of the brain. A strength of this method is that it’s non-invasive. Similarly, to TMS, there may be an increase in patient attendance due to this. Another strength is that it has high temporal and spatial resolution. This provides accurate timing of neuronal activity in the brain and displays a very clear structural perspective for researchers to analyse (Singh, 2014). In addition, it’s also found to be more accurate at localization of cerebral activity, compared to other research methods such as EEG (Ebersole & Ebersole, 2010). Even though high precision is a great feature of MEG, it’s increased sensitivity can be affected by slight movements, consequently causing disruptions in the results. Therefore, it’s not as easy to perform MEG scans on patients who cannot cooperate fully e.g. children. Furthermore, MEG scans are most commonly used in the evaluation of epileptic patients, measuring magnetic fields from the entire head and locating the sources of epileptic spike (Ebersole, 1996). For example, a study by Otsubo et al (2002) aimed to discover whether the spatial distribution of spike sources determined by MEG provided reliable information for planning surgery and predicting their outcomes in epileptic patients. They concluded that MEG accurately found epileptogenicity, the gradual process by which a normal brain develops epilepsy (Pitkanen, Lukasiuk, Dudek & Staley, 2015). This therefore suggests MEG’s ability to locate the biological basis of epileptic spikes, consequently preventing possible strokes in epileptic patients.
Another type of research method adopted by cognitive neuroscientists is MRI. Magnetic Resonance Imaging measures brain structure, by using magnetic fields and radio waves. When magnetic fields are passed over the head, referberations are picked up by hydrogen molecules. The scanner can then convert the activity into a structural image (Martin et al 2013). One of the strengths in MRI is the ability to pick up structures such as cartilage, ligaments, tendons etc. when assessing the body due to its high spatial resolution. This is great in comparison to CT scans for example, that mainly images bone (Pedersen, Weber & Ostergaard, 2012). Another advantage of MRI is that it is highly sensitive, e.g. the ability to identify microbleeds in the brain (as recognised by Kidwell & Hsia, 2006), recognising acute strokes in patients. However, a disadvantage of MRI is motion artifact. This is when blurring or streaking appears on the scan due to the voluntary/involuntary movement of a patient (Rowbotham & Grainger, 2011). An interesting capability of MRI is to correlate disorders such as PTSD (post-traumatic stress disorder) with the areas of the brain (the hippocampus). Kitayama, Vaccarino, Kutner, Weiss & Bremner 2005, stated that through a meta-analysis of MRI and PTSD studies, it was shown that adult with chronic PTSD have smaller hippocampal capacity, compared to healthy subjects and traumatized subjects without PTSD. Thus, inferring the biological basis of PSTD and its symptoms.
Lastly, PET scans are also used by cognitive neuroscientists to recognise the biological bases of behaviour and mental processing. Positron Emission Tomography (PET) Measures brain function (brain metabolism, glucose consumption and blood flow). Patients are injected with radioactive substance, which contains a positron emitter (Turkington, 2010), entering the brain and travelling to active cells. Patients enter a cylindrical scanner, which then examines the amount of oxygen (blood flow travelling to) consumed by neurons (Martin et al, 2013).
One of the main strengths of PET scans are that it has high degrees of accuracy and sensitivity (Lammertsma, 2001). This is linked to higher diagnostic accuracy; even more so when in combination with Computed Tomography (CT) (Nehmeh & Erdi, 2008). Despite this, a disadvantage to this technique is due to its radio activity, meaning only certain people can take part. Individuals such as premenopausal women, pregnant women or small children and babies cannot. Thus, limiting potential research of PET around brain development in early years (Martin et al, 2013). Furthermore, PET is a high-cost technique, which can run into millions of pounds to run (Martin et al, 3013). One way in which this type of research method is used to explore the biological basis of behaviour and mental processing was studied by Volkow & Tancredi (1987). Using PET, psychiatric patients (known for their history of violent behaviour) were shown to have blood flow and metabolic abnormalities in their left temporal lobe. As well as this, two of the four patients had ‘derangement’ in the frontal cortex. This displays the utility of PET in investigating possible brain abnormalities that could lead to violent behaviour.
The methods used by neuroscientists can all, in some way, research the biological bases of behaviour and mental processing. It became evident here that the different techniques share some similar advantages and disadvantages. For example, all methods apart from PET are non-invasive methods, (Smith, 2019;. which can be viewed positively by those patients who may suffer from anxiety of medical procedures such as these. Additionally, there is high sensitivity in MEG and MRI, however these supposed advantages can be viewed as a weakness (in MRI, motion artifact can occur). MEG and MRI also share an excellent spatial resolution, making their diagnosis more likely to be accurate.