|
|
|
Mainstream 3
Further summaries and reviews of books, papers and articles on mainstream consciousness theories The Executive Brain Elkonon Goldberg Oxford University Press ISBN 13-978-0-19-515630-0 (pbk) The author emphasises that the frontal lobes of the brain are crucial to purposeful behaviour, such as, identifying objects, making complex decisions, creating plans to achieve objectives, and monitoring the outcome of actions directed at these goals. These are the executive functions of the brain that co-ordinate the activities of other neural regions. The ability to appraise our own actions and the actions of others arises in the frontal lobes, and damage in these areas leads to a loss of judgement, even if performance on on formal intelligence tests is unaffected, and movement and perception is normal. This part of the brain is much more developed in humans than in other mammals. One feature that distinguishes human from animal behaviour is that human behaviour is more proactive, and is driven to a good extent by plans and aspirations extending beyond the mere term. To do this, the brain has to take certain elements of past experiences, and reconfigure them into possible future scenarios. Thus the human brain must go beyond mere representation, to perform a manipulation of representations. Damage to the frontal lobes can lead to a lack of organised or purposeful behaviour in previously coherent individuals. In Goldberg's view, the right hemisphere of the brain is better equipped to deal with novel situations, and the left hemisphere is more suited to routine tasks. It is suggested that novel tasks processed in the right hemisphere are later transferred to the left hemisphere as they become routine. In this he argues from the effects to the right hemisphere, and also from other circumstances, for instance that most people process music mainly in the right hemisphere, but trained musicians switch to using the left hemisphere. Blood flow in the frontal lobes is higher when they are dealing with the novel tasks. As tasks are learnt, the focus moves from the right and frontal areas, to the left and rear areas of the cortex. Frontal lobe activity is strong when tasks are novel, and subsides as they become routine. Studies have identified the medial region of the prefrontal cortex, as being important for introspection into other mental states, or for thinking about the internal mental states of other people. The frontal cortex is also seen as integrating information about the organism itself and information about the external world. The author goes onto argue against the concept of categories of object being coded into circumscribed locations of the brain. He points out the ability to identify objects as part of a category, such as a dress or a dog, inspite of enormous variations in the actual appearance of such objects, is a fundamental cognitive ability, essential to navigating the world. With some types of brain damage, the patient has their sensory processing intact, but lacks this paarticular ability, although only in one modality, so, for instance, they lack it in vision, but retain it in touch. The cortical areas that are damaged in these cases are adjacent to the relevant sensory cortex. From this, it is argued that the different sensory components (visual, auditory etc.) of the perception of an object are distributed in different parts of the cortex. The author describes this relationship as gradiental, in that the regions involved are next to, and graduate out from, the regions for handling sensory input. It is also suggested that the cortical representation of words for objects is closely linked in the brain to the cortical representation of the objects themselves. The author claims that both the popular and academic approaches to memory are incorrect. Both approaches see memory as an exercise in memorisation and subsequent recall, as an end in itself.In real life, internal needs require us to hold onto certain information in the short-term or working memory. The choice of what to hold onto in working memory is driven by the frontal lobes. This is because the frontal lobes control the selection of information in order to allow the organism to operate. However, the necessary information is not in the frontal lobes, but in other regions of the brain. The 'what is it?' question is handled by a conjunction of the occipital and temporal lobes, while the spatial 'where is it?' question is handled by a conjunction of the occipital and parietal lobes. The memories for 'what?' are formed and stored within the occipital/temporal system, and the memories for 'where?' within the occipital/parietal system. Studies show that these areas of the cortex are accessed from different areas of the frontal lobes. The author contrasts much academic decision making with real life decision making. Real life has both deterministic questions, such as 'what is the right telephone number' and uncertain decisions, such as 'what shall I wear?' Patients with frontal lobe damage have difficulty with uncertain questions, rather than deterrministic questions. In other words, frontal lobes are vital in a free choice decision. With dementia, the decline in dealing with uncertain or ambigous decisions begins earlier, than it does for deterministic choices. The author emphasises how some mental diseases are rooted in abnormality in the patient's biochemistry or neural structure. This is the case with schizophrenia, depression, obsessive-compulsive disorder, attention deficit disorder and Tourette's syndrome. The frontal lobes are usually involved, partly because they can reflect damage elsewhere in the brain. In early Alzheimer's frontal lobe damage is reflected in a reduced ability to take decisions. Patients with frontal lobe damage may perform satisfactorily on tests of particular cognitive functions, but show deficits when it is necessary to combine skills into goal-directed action. The symptoms of damage to particular parts of the frontal lobes are different. Damage to the dorsolateral area produces difficulty in initiating behaviour, or of stopping if behaviour is once initiated. The frontal lobes are thus essential for the maintenance of drive and motivation. Patients with frontal lobe damage have problems with their ability to plan or anticipate the consequences of their actions, while damage to other brain regions does not have this effect. Such patients are also more prone to be distracted from intended tasks by their environment. Opposite to the dorsolateral syndrome is the orbitofrontal syndrome. Here the patients are emotionally uninhibited, and oscillate between euphoria and rage, and again do not anticipate the consequences of their actions. The prefrontal is seen as the association cortex of the frontal lobes, which are the action lobes, while regions in the rear of the brain comprise the association cortex of the sensory areas, and encode information about the external world. The prefrontal cortex is seen as selecting parts of the posterior sensory and association cortex that need to be brought into action, at any particular moment. This is achieved by pathways that descend from the prefrontal to the ventral stem, which as part of the reticular activating system can selectively activate cortical regions. Break down anywhere in this triangular system can cause mental health problems. Linked to the prefrontal is the anterior cingulate cortex. This region of the cortex is involved with emotions, in particular with inhibiting distress, by restraining the amygdala. Consciousness and freewill: Goldberg's book provides an interesting insight into the importance of the functioning of the frontal lobes. However, there is one surprising gap. Although much of the book is about the ability to initiate behaviour, and to choose between advantageous and disadvantageous courses of action, consciousness and freewill do not even make it into the index. The nearest the author comes to discussing these issues is a scattering of references to there being no need for Cartersian ideas about the functioning of the brain. It is not clear whether this is supposed to be sufficient to dispose of the consciousness question. Perhaps we should be thankful, since the reader does not have to plough through what now seems to be an obligatory final chapter, where an author borrows from convenient philosophers to prop up standard ideas on the insignificance of consciousness. Goldberg was trained in the former Soviet Union, where the establishment was probably even less friendly to speculations about consciousness, than was mid 20th century western science. However, it highlights a persistent problem for consciousness studies that a book of this kind can simply ignore the subject. |
| Email: quantum-mind@blueyonder.co.uk Copyright © Quantum Mind 2010. Web design by 7Soft.co.uk. |