The Learning Zone
Is human brain function dictated by our DNA?
The mind and brain: is human brain function dictated by our DNA or is it a result of experience?
Can the mind influence, through experience, the way brain function evolves in the course of our lives, or is brain specialization written in our genes? In other words is free will an illusion or a reality?
Although the question is still open, recent experiments with the deaf and blind have been key to show that the mind and experience play a role and an important one too, modifying significantly human brain function and structures, a phenomenon referred to as neuroplasticity. And whilst the role of DNA is certainly very important, this brief article shows that the influence of our thoughts is paramount to the way our brain changes after birth.
The data done with the deaf comes from several studies. These all indicated that their brain changed in many ways with respect to subjects who could hear normally:
- they had a better peripheral vision than normal
- they had a larger area of visual cortex associated with motion
- they also had more activity in areas associated with multiple sensory inputs.
But the finding that was the most surprising was that the auditory cortex was processing peripheral vision and motion!! In other words the auditory cortex had not just been left standing idle, but had instead been actively involved in tasks, like peripheral vision and motion, which are limited to the visual cortex in subjects who could hear normally.
Similar observations were made with people who were blind since birth. Here it was discovered that peripheral hearing was better and that sounds were stimulating part of the visual cortex.
Other studies in blind people learning Braille showed even more interesting results: when a blind person learned how to read Braille there was an increase in the somatosensory cortex assigned mainly to the index finger (used to feel Braille) and the motor cortex associated with the side-to-side motion increased in size. Now, by momentarily knocking out these specific regions by using a technique called transcranial magnetic stimulation, the person couldn’t read Braille any longer. This showed that it was not just a correlation but that it was actually causal, in other words the areas that had been temporarily knocked out, were enabling the person to read Braille.
The last finding which is really worth mentioning, showed that blind volunteers have an improved capacity to recall words, and that it was the visual cortex that became activated when they actively accomplished this task. However this was not observed in controls, in other words in subjects who could see normally. This result is extremely important because it shows that the visual cortex did not shift from one sensory function to another (like from seeing hearing to a tactile sense) but it was instead involved in a non-sensory function, a higher level task, a task as complex as language !!
To summarize, this article clearly shows how multiple studies reach the same conclusions : various parts of the brain have the capacity to engage in tasks that are completely different to what they were originally destined for and brain function results from experience. Before we conclude though, it is important to stress the important role attention plays in this process. All the experiments described involved subjects actively engaged in tasks that required significant levels of attention. Had they undertaken the same tasks passively, the outcomes would have certainly been different. In other words, key to neuroplasticity1 is the role of attention: passively hearing sounds (for example) is not going to expand one’s cortex as actively paying attention to them. This stresses again the role of our mind, and certainly provides new food for thought about the mind and brain puzzle. To know more, watch this space for forthcoming articles!!
1Neuroplasticity: the ability to change the structure and functioning of the brain through experiences and the conscious use of directed thought
By the Horizon Research Foundation editorial board