Thursday, January 9, 2014

Origin of the mind

Traditionally, we explain human behavior in terms of “mental activity”. We believe that our actions are the result of emotions, attitudes, conscious thinking and personality. Subsequently, the brain has been regarded as a “Swiss penknife”, each anatomical part being a specialized tool for a certain faculty, the same faculties we found in the psychology textbooks. But what is the nature of this taxonomy, how was it established and how sure of its validity are we?

This theoretical scheme is known to be grounded in the philosophical heritage of Ancient Greece. Now, 2000 years after Plato and Aristotle, various authors argue that the use of concepts extracted from traditional psychology hinders the understanding of brain functions and instead of trying to match the brain activity with psychology textbooks we should rather try to understand the actual function of different brain networks, the representations they entail and the processes they employ.
Recently I have published a neuroscience book called Origin of the mind; From viruses to beliefs whose objective is to uncover the actual basis of behavior and what we traditionally call “mental activity”, the way in which they develop whilst interacting with the environment and how they have evolved. Here are briefly presented some topics coved in my book.

Data from neuroscience have shown that what we call “beliefs” or conscious thoughts regarding a certain situation or activity are not generated by an independent Self, as philosophers and psychologists claim, but instead, within the brain circuits involved in dealing with actions. The conscious Self with its belief system seems to be a construction of the brain networks responsible with perception of environment and with learning movements.
Traditionally, decision making is regarded as being separate from action planning. However, recent neurophysiological studies suggest that potential action plans aimed at multiple targets, are simultaneously represented in multiple motor areas of the cortex. Selecting one target – or “the decision” – involves the same cerebral mechanism as the one involved in action planning, the two of them functioning in an integrated manner. While making decision about actions, the signal related to the value of an action is encoded in cerebral regions involved in movement generation, thus suggesting that decision-making and action generation share a common level of neural organization.
There is sufficient proof to demonstrate that the ability to mentally represent our future works hand in hand with the ability to represent our past. Thus, episodic memory can be regarded as the capacity to picture ourselves in time, both in the past and in the future. Evidence from clinical psychology, developmental psychology and neuropsychology congruently points toward this hypothesis. Representing future episodes requires a system that can flexibly recombine details of past events. Recalling implies that pieces of stored information are recombined and not that past events are sequentially unfolded in the same form as they have been lived before. Subsequently, episodic memory builds future events by extracting and recombining stored information, thus simulating a new event. Novel memories cannot be constructed in the absence of recalling past memories, whereby the information associated with the present perception gains significance and organization. Memory updating only occurs when the brain enters a labile state. The new information will subsequently become apparent based on this substrate. Studies have shown that re-exposure to the initial context is absolutely necessary for the purpose of rewriting an old memory according to the coordinates of the novel information. As a result, one needs to know and understand the actual functional organization of the brain in order to explain and facilitates its performance, such as that associated with learning or relearning (i.e., “extinction”, in the case of phobia or addiction). 
Related with the above statement, experimental data has revealed that the ability to recall information is not independent from what we traditionally call “perception”, “imagination” or “attention” but rather shares an intimate relation with them. The “perceptual-mnemonic” theory of the brain implies that it may not be constructive to make a distinction between “perception” and “memory” as mental functions, as they may seem to be from introspection. Instead, they should be regarded as different manifestations of a common neural substrate.
Various experimental data suggests a strong neuronal connection between romantic love and the drug-generated euphoric state. As a result, numerous authors have distinctly formulated a strong connection between attachment and addiction. Furthermore, regardless of whether we are talking about people, drugs, activities or the things that we like, end up modifying the architecture of our brains by reinforcing the already existing synapses and creating novel synapses, synaptic buttons and newborn neurons. Contrary to the beliefs shaped a few decades ago, the development of the brain as an organ does not cease when reaching adolescence. It modifies its circuits in the course of a lifetime by adding novel neurons and creating new synapses and losing others. These long-lasting alterations represent the basis underlying the mental content that defines us as individuals, or what psychologists term “Self”. Hence, what psychologists call “Self” is in fact, a sum of connectivity networks – or hubs – that are formed in the brain as a consequence of exposure to experiences. Furthermore, these alterations are responsible with the formation of novel memories. These changes occur by virtue of epigenetic mechanisms that alter chromatin and DNA in neurons exposed to external information. Subsequently, our experiences may affect the lives of our grandchildren. Therefore, the “memory” of an event can be passed from one generation to the other. A simple stimulus from our environment may turn on or shut down certain genes. Subsequently, this change may be transmitted to offspring, thus affecting the genes of the species.
According to genetic data, it seems that the brain evolved from molecules derived from endogenous viruses that have lost their initial function, and were instead co-opted to create genetic diversity and aid genome expansion – a process known as exaptation. Considering these origins, the nervous and immune systems hold functional similarities. One of them refers to the process of generating novel neurons and synapses, which are maintained consequently to exposure to information during a sensitive or critical period, similarly to the process underlying T and B lymphocytes in the adaptive immune system. It seems that the nervous system, akin to the immune system, underlies a selection in terms of identity and neuronal connectivity occurring both throughout development and during processes associated learning and with brain regeneration. Therefore, it can be assumed that the nervous system, similarly to the immune system, evolves in situ as a consequence of experience. Once they are “marked” with a certain category of information, cells in these systems undergo epigenetic modifications by virtue of which they become dependent upon that information. Subsequently, they will attempt to update and defend that information every time they get the chance, thus preventing its “dislocation” by other pieces of information (or cognitive immunity). This mechanism is similar to the one responsible with creating addiction modules, which were initially genetic. In more advanced organisms, they subsequently added the epigenetic dimension, thus determining what we call, learning. Life experiences are reflected in the brain in the form of the “Self”, similarly to the immune Self, while the nervous system defends this construction in the same way the immune system defends the organism against antigens.  

No comments:

Post a Comment