TMS or Transcranial Magnetic Stimulation is considered as the last resort in the field of neuroscience and psychology when rest of the treatments to deal with the patient’s depression fails to show any benefit. It is a noninvasive procedure, which improve the symptoms of depression requires the magnetic fields in stimulating the nerve cells in the brain. The process initiates with the placement of an electromagnetic coil in the forehead against the scalp, which delivers a magnetic pulse to stimulate the nerve cells in the region of the brain that controls the moods and depression. The following study will identify the advantages and disadvantages of using TMS and the strengths of the procedure. It will further look into the rage of application of TMS. The study will be supported with an empirical example.
Stewart et al. (2001) in their paper concluded that TMS applied on the posterior BA37 of the left hemisphere very much disrupt picture naming but leaving the word reading, non-word reading and color naming unaffected. BA37 is the area of posterior inferior temporal cortex, which controls multiple functional role of human brain. Their study identified no delay in the naming when TMS was implemented over the vertex or the analogous right hemispheric site precludes an explanation in terms of a non-specific effect of TMS. The impact of TMS on phonological process remains unaffected. The evidence from the study that reflects that the reading of words, non-word reading remains unaffected can verify this statement. These skills require high level of phonological process. It will be false to assume the picture-naming deficit as a result of interference with the semantic processing. It is because the semantic lexicon also help in word reading.
Hence, the disturbance that the participants are facing in naming pictures is an outcome of TMS. The functional imaging and object identification gets affected by the lesions in the particular area. It is due to the activity in the posterior BA37 of the left hemisphere. Hence, the study concludes that technique produces a specific picture naming deficit. This suggests that the left hemispheric posterior BA37 is essential in object identification. Hence, TMS considerably controls and stimulates the neurons in the brain that can help the psychologists and neurologists in dealing with the patients with high depression symptoms.
TMS or Transcranial Magnetic Stimulation has various utility in the field of neuroscience. It exceeds the limits of other similar methods utilized in the field. For example, in EEG, the electrical activity of in the neurons generates a fluctuation in the electrical field. TMS operates in the opposite direction, where the current is passed cleverly through designed loopy wires to activate or deactivate a considerable number of neurons without breaking the skin.
Berlim, Van den Eynde and Daskalakis (2013) pointed out that the significance of the TMS’s non-invasive manipulation can never be overstated. Experiment based on the observation alone falls prey to the fact that any observed relation between two events that is observed could always be explained by another unobserved variable. Changing the putative causes being tracked can confidently state a directional, casual relationship, passing over Hume’s objection with a glance at Goodman’s resolution of the problem of induction. In other words, this increases the capability of the practitioner from merely observing the brain activity to controlling and willingly modifying it.
However, on a later study, Berlim et al. (2014) mentioned that the greater responsibilities come with superior power. Though, many believe the TMS is superior to previous existing methods of manipulation like injecting pharmacological agents, there is no compact assurance of the safety. The outcome of the method remains unjustified till date. Hence, risks remain in the procedure that led many neuroscientists and psychologists to remain unconvinced about the safety, reliability and reversibility TMS.
TMS’s mechanism is still a mystery. Scientists failed to explain how exactly the method works, which makes it difficult to mechanically interpret the results.
Moreover, most of the TMS labs tend to move the coils around by hand unless they get a desired effect due to the monetary concerns and anatomical variations. Hence, it becomes impossible for the experimenter to repeat the process as it is done manually. In other words, reproducibility is minimum in case of using TMS, as it is always the case when the critical piece of the experimental apparatus is the experimenter him or herself (Berlim et al., (2014).
As identified in a paper by Rush University Medical Center (2010) the technique delivers high frequency of magnetic field pulse to a focused segment of the brain for stimulating the locations of the brain related to depression. The high accuracy of the techniques helps the practitioner in stimulating only the desired portion of the brain keeping the remaining area unaffected. The pulse delivered through TMS techniques matches the intensity of the magnetic field generates during a MRI imaging scan. These repetitive explosions of magnetic energy implemented via scalp excite the neurons in the local level and in adjacent areas of the brain. The patients who failed to find any kind of benefit from the conventional antidepressant medication can be treated with the TMS as it reflects its important for these cases. A consistent routine of antidepressant medication later to the TMS implementation can help maintaining the benefits in most of the patients. The utility of the technique is further spotted by FDA and has approved the device. The process does not require any anesthesia or sedation like other techniques and the patient being treated with TMS remains awake and alert during the procedure being implemented.
The method has helped the experts in understanding the function of the pathological human brain. They have identified various applications of TMS in the field of cognitive neuroscience. They are as follows.
Applying TMS over the primary cortices helps to measure the response to single-pulse. This helps in examining the cortical excitability. The evoked responses can be dependent variable such as motor phosphene intensity for visual cortex, potential for motor cortex or TMS intensity threshold essential to draw out those responses.
It can further help in behavioral, cognitive or even brain image testing. An administration of ten to fifteen minutes of repetitive low frequency of TMS before and after the test helps in identifying the cognitive state of the participant.
Moreover, short trains of single pulse of high frequency of repetitive TMS can help understand the ongoing cortical activity and briefly interfere with it. TMS is applied on the patient while they are engaged in activity or behavioral tasks. The comparison of the performance reflected by the individual with and without TMS demonstrates that the stimulation greatly impact on the performance.
It can be concluded from the above discussion that the utility of Transcranial Magnetic Stimulation in the field of neuroscience is limitless. It has the potential to treat the patients with depression without applying antecedents and enables the patients to be conscious while the procedure is being performed. It can be counted as the greatest strength of the technique. However, the actual mechanism of TMS is still unrevealed in the world of neuroscience that compromises the safety of the patients and increases the risk factors. This restricts considerable number neuroscientists from relying on the technique and implements it on their patients. Moreover, the coil needs to be adjusted manually on the scalp of the patients. This restricts the procedure for repetition and duplicity. However, the FDA found the technique useful and has approved the neuroscientists and psychologists to implement it on the patients.
Berlim, M. T., Van den Eynde, F., & Daskalakis, Z. J. (2013). Clinically meaningful efficacy and acceptability of low-frequency repetitive transcranial magnetic stimulation (rTMS) for treating primary major depression: a meta-analysis of randomized, double-blind and sham-controlled trials. Neuropsychopharmacology, 38(4), 543-551.
Berlim, M. T., Van den Eynde, F., Tovar-Perdomo, S., & Daskalakis, Z. J. (2014). Response, remission and drop-out rates following high-frequency repetitive transcranial magnetic stimulation (rTMS) for treating major depression: a systematic review and meta-analysis of randomized, double-blind and sham-controlled trials. Psychological medicine, 44(2), 225-239.
Rush University Medical Center. (2010, October 13). Long-term benefits of transcranial magnetic stimulation for depression supported by new study. ScienceDaily. Retrieved November 16, 2017 from www.sciencedaily.com/releases/2010/10/101012114052.htm
Stewart, L., Meyer, B. U., Frith, U., & Rothwell, J. (2001). Left posterior BA37 is involved in object recognition: a TMS study. Neuropsychologia, 39(1), 1-6.