Does Memory Reside in the Brain? (Part 3)
like all planetary reflections. The power was difficult to evaluate but appeared incoherent; the female students complained of having no power in their legs, they could stand up, but then fell to the ground. Upon mental state examination, there were no psychotic symptoms or bizarre visual experiences, but there was an impressive emotional abnormality. All the children showed a complete absence of concern for their symptoms and laughed and joked inappropriately. This was in marked contrast to the anxiety and concern of the school authorities and parents. All symptoms in every child resolved within 24/48 hours of hospital admission. Hematological investigations and viral studies on 27 of the children were completely normal. None of the teachers were affected and there were no cases in the adjacent village.
Does memory reside in the brain? (Part 3)
In the two previous issues we described more than a dozen provocative yet very valid reasons to affirm that memory does not certainly reside in the brain. We want to continue here presenting other and new points of reflection on this matter.
The brain does not seem to have any mechanism for reading a memory. On a typical laptop computer, a read-write head handles both the work of reading information from a hard disk and the work of writing information. There is nothing similar in the brain, nor does there seem to be anything similar to some component of the brain that does the work of reading information from some part of the brain. Let's imagine that our brain has memory information stored in a particular place. How could that information be read? There is no component in the brain that moves to different places when remembering something. In the absence of a better idea, it is often hypothesized that synaptic patterns store memories, suggesting that the arrangement of synapses could somehow be a code that specifies memories. But we might note that the brain does not appear to have anything similar to a synaptic pattern reader.
Brain noise. There is so much noise in the brain, with each neuron bombarded by signals from thousands of other neurons, that if a brain had to somehow read a stored memory, it would be rapidly drowned by all the neural noise. We can use the term signal drowning for what happens when there are so many signals from so many sources that a particular signal is effectively drowned. For an example we can consider the case of a malfunctioning television that would show all television channels simultaneously on a single screen, or a malfunctioning radio that would play simultaneously the music and words of every station at the same time. In the cortex we witness exactly this signal drowning, because each neuron emits a signal very frequently, about once per second or more, and each neuron is directly connected to more than a thousand other neurons.
Brain signal drowning is effectively a problem to solve. Given the simultaneous number of signals present in each neuron, a brain signal can hardly travel for more than a few centimeters without destroying the signal$^{25}$ (Fig. 5).
Absence of activity. If you are retrieving memories from your brain when you recall something, we would expect there to be detectable signs of such brain activity. But we cannot detect anything different in our body when we are working hard to remember something. When the heart works harder, we have a clear physical sign of this: an increase in heart rate that can be noticed by checking the pulse. But when we work hard to retrieve memories, we do not have the feeling that something in our head is working harder. Brain scanning studies provide no solid evidence that the brain is working harder or doing something different during human recall activity. Studies on neural correlates of memory recall have subjected subjects to brain scanning while performing recall and recognition tasks$^{26,27,28}$. The average percentage signal variation reported was about 1 part in 200 or 400. Such results show no evidence