There is no doubt that the central nervous system (CNS), and in particular the brain, is the "seat" of the biological processes that underlie human identity and personality, and thus a person's character and mental capacities. It is of central importance for our behaviour, perceptions, thoughts and feelings and regulates body functions such as heart rate, muscle responses and control of our immune system. It works in conjunction with both our bodies and the outside world. It is the organ of our personhood and, in this respect, it is a unique and indispensable organ for human self-consciousness.5 Alternatively, one can say that our mind is our brain in action. Without this action the human mind is gone.
Small differences in the structure and organisation of the brain lead to different functional capacities and, therefore, to differences in mental and physiological processes directed by and derived from the brain. Such differences underlie differences in personality between individuals. These differences are only partially determined by the genotype as even identical twins differ in functional capacities and personality. Neurodegenerative and traumatic disorders obviously alter the organisation of the nervous system and,
5 This uniqueness is further explained by the (albeit fictional) thought experiment of human brain transplantation. The result will be that the brain donor will see him-/herself as having received a new body. On the other hand, the recipient 'person' will cease to exist. Brain transplantation, therefore, does not exist or should be defined as body transplantation.
therefore, the functioning of the brain. Cell implantations in the brain and gene transfer to brain cells which aim to restore brain functions will never be able to restore the structure and organisation of the brain prior to the impact of the disease or trauma. Therefore, unwanted physiological and mental side effects will occur on the recipient of any form of intervention. However, these side effects may be very subtle and will not necessarily be obvious in normal daily life.
This chapter will focus on interventions in the brain in the field of restorative neurosurgery. The goal of these interventions is tissue repair or the introduction of physical changes in brain chemistry in order to relieve the symptoms of certain diseases. Neurodegenerative diseases like Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), as well as acquired nervous trauma as the result of a stroke or spinal cord injury, are the first candidate diseases for such approaches. The neural grafting of fetal brain cells (neurotransplantation) in PD and HD patients was the first experimental clinical treatment explored because precise aims could be formulated for these interventions (implanting nerve cells to deliver dopamine and supplementing interneurons in the striatum of the brain in the respective cases). Clinical research is less advanced for other neurodegenerative diseases and in the field of brain trauma, where the target for restoration is larger or less well-known. In these cases, the potential target for intervention in the CNS is largely unknown and this is crucial knowledge for any restorative neurosurgery. In principle, if a brain disorder can be pinpointed to a particular (local) cellular or molecular origin, or a target site for regeneration can be identified, then cell or gene therapy may be possible. For psychiatric disorders incompatible with normal life, which are potentially caused by a multiplicity of interrelated factors, cellular and molecular interventions in the brain may not be feasible unless one finds a specific target which can be reached through the efficient treatment of a particular sub-symptom. This may not be unrealistic as nowadays the deletion of single genes in trans-genic animals can show dramatic behavioural effects in areas such as drug dependency, anxiety, depression and fear conditioning, indicating the possibility of existing primary targets.
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Have you ever been envious of people who seem to have no end of clever ideas, who are able to think quickly in any situation, or who seem to have flawless memories? Could it be that they're just born smarter or quicker than the rest of us? Or are there some secrets that they might know that we don't?