Summary

This chapter explores puzzling paradoxes that apply to two major neurological diseases. The first involves allergies which range in severity from allergic rhinitis, which may cause only mild discomfort, to allergic asthma which can be life-threatening. It has been repeatedly demonstrated that people with malignant brain tumours have fewer allergies than people who do not. The reasons for this association are unknown, but it is possible that allergies reflect an active immune system that is also able to destroy nascent tumours. Alternatively, it is well known that malignant brain tumours suppress antitumour immunity, so it is possible that they suppress allergies as well. The second paradox involves cigarette smoking, well known to cause lung cancer, heart disease, chronic respiratory disease and other harmful effects that have been extensively documented. Yet cigarette smokers have a lower risk of Parkinson's disease than do people who have never smoked cigarettes. Epidemiologic evidence indicates that this paradox is not an artefact, but that cigarette smokers actually enjoy lower risks of Parkinson's disease as a result of smoking. These reduced risks probably result from nicotine's observed protective effects on the nervous system.

Introduction

Conventional wisdom maintains that an illness or assault on one organ should not have a beneficial effect on another. Yet in neurology, as in other branches of medicine, there are cases where harm to one biological system appears to benefit another. This chapter focuses on the protective effects of allergy on glioma, and of smoking on Parkinson's disease.

Summary

In neurological conditions, the major sets of paradoxical cognitive phenomena generally take one of five forms: (1) enhanced cognitive performance of neurological patients vis-à-vis neurologically intact individuals (‘lesion facilitation’), and (2) alleviation or restoration to normal of a particular cognitive deficit following the occurrence of a second brain lesion (‘double-hit recovery’). (3) A third set of paradoxical cognitive phenomena represents what may be termed ‘hinder–help effects’, where a variable that produces facilitation or detriment of performance in healthy participants results in opposite effects in neurological patients. (4) A fourth form of paradox relates to anomalies in the usual relationship between the presence/size of a brain lesion and the degree of cognitive deficit (‘lesion–load paradox’). (5) A fifth paradox is where there may appear to be direct or indirect benefits for long-term neurological outcome as the result of specific cognitive deficits being present (‘paradoxical positive outcome’). Discussion of neurological conditions will mainly be concerned with the first two sets of paradoxical phenomena, although the remaining three sets will also be reviewed briefly. In psychiatric disorders, analogous paradoxical phenomena have mainly been found in instances of enhanced cognitive performance in conditions such as depression and schizophrenia vis-à-vis healthy control participants, and also in reports of ‘post-traumatic growth’ after a major psychiatric illness or negative life events.

Introduction

As outlined in Chapter 1, the study of brain–behaviour relationships from cases of cerebral pathology has traditionally been embedded in the lesion-deficit model.

The study of the human brain has been variously referred to as ‘the last great frontier’, or a challenge equivalent to that of understanding the universe. Cosmology and neuroscience, in fact, probably have some things in common. Our galaxy, the Milky Way, has thousands of millions of stars, and some commentators have conjectured that the number of stars in the Milky Way may be similar to the number of cells in the human brain. In the past two decades, imaging and sensing technologies have transformed both the field of neuroscience and the field of cosmology. Perhaps a more interesting analogy is in the realm of awareness and human consciousness. With our current awareness mechanisms, we are usually only aware of a tiny amount of cognitive activity that mediates human behaviour – many cognitive and perceptual inferences take place at an unconscious level, we often fail to realize how our perceptions and beliefs may not be completely based on reality, and we often fool ourselves into believing that we have free will and full responsibility for all our thoughts and actions (Frith, 2007). Similarly, in the case of cosmology, with our eyes alone we are only aware of a tiny part of our galaxy, and if we were to take our perceptions literally, we would fall for the simple delusion that the sun moves round the earth.

Summary

Paradoxes abound in nature and in the realm of the human condition. Paradoxes have been evident in fields of science – from plant biology to human biology to physics – and in areas of human endeavour, ranging through political, literary and social activities. Paradoxes often represent instances where current knowledge may be deficient, and thus predictions based on such knowledge may be inconsistent with actual events or findings. At the level of scientific methodology, paradoxical phenomena offer powerful opportunities to test models and conceptual frameworks, and to enable true ‘paradigm shifts’ in certain areas of scientific inquiry. Insights from paradoxical phenomena in clinical sciences not only help us to understand mechanisms of function and dysfunction, they also provide clues as to therapeutic strategies, which may alleviate impairment and disability resulting from disease and injury. In addition, they may contribute towards a more positive, humanistic view of diverse states of the human condition.

Introduction

The word paradox is derived from the Greek: the prefix para means contrary or opposed, and doxos means opinion. The Shorter Oxford English Dictionary (2002) includes amongst its definitions of paradox ‘a seemingly absurd or self-contradictory statement or proposition which, when investigated or explained, may prove to be well-founded or true’. In his philosophical treatise on paradoxes, Sainsbury (2009) has highlighted the paradoxical nature of paradoxes themselves: ‘Paradoxes are fun.

Summary

We consider how a number of interventions that would normally interfere with function have paradoxically improved symptoms in patients with neurological conditions. These include distorting reality, constraining patients' ability to perform everyday tasks, impeding vision, temporarily disabling healthy brain tissue, and distracting patients from the task at hand. We argue that the effects of these diverse interventions can be understood within a general framework of brain function that emphasizes competition for limited capacity resources. We discuss how this competition can be biased to produce rehabilitation benefits.

Introduction

Neurorehabilitation refers to any intervention that aims to reduce impairment caused by brain injury, disease or developmental abnormality. It also refers to techniques that help compensate for such impairments or that facilitate adjustment (Wilson,1996). Much that is effective in rehabilitation is far from paradoxical. People relearn and improve through practice, encouragement and the setting of incremental, achievable goals (e.g. Wilson et al., 2009). Where full restoration of a function is not possible, as is often the case, compensatory aids such as diaries and communication devices can facilitate independence (Kime, 2006; Kapur and Wilson, 2009). Patients and families can gain comfort, perspective and realistic hope from discussion with professionals and other patients.

In line with the focus of this book, here we concentrate on particular interventions that under normal circumstances may be considered deleterious or contrary to perceived wisdom, but which have been shown to reduce or offset impairment in people with brain injuries.

Summary

Paradoxical findings relating to the human brain have implications for our understanding of the workings of the normal brain, and for how normal functioning may be enhanced. Paradoxical findings may also have implications for how we can prevent and detect brain disease, and how we may best repair and rehabilitate the damaged brain. The brain may best be modelled as a nonlinear device, which relies on dynamic synchrony and balance between neural systems. Damage to the brain may upset this dynamic state, and repair may often entail interventions that restore a degree of synchrony and balance. In this final chapter, we propose 10 principles of brain function that can help accommodate paradoxical phenomena, and we also speculate on paradoxical therapeutic interventions that may be beneficial to human brain functioning.

Introduction

If we can be forgiven a degree of owner's pride, the human brain is quite extraordinary. A three-pound mass of jelly-like material is the only entity in the universe (that we know of) which can form and test theories about that universe. It can also speculate about structures much smaller or larger than it can possibly see. It might be thought that, when it comes to studying itself, the brain would have a number of inherent advantages, being on home turf, as it were. It is certainly true that we are very familiar with what the brain can achieve.

Amnesia and organic memory impairment are commonly seen after many types of brain injury including degenerative disorders, head injury, anoxia and infections of the brain. If severe, amnesia is often more handicapping in everyday life than severe physical problems.

People with the classic amnesic syndrome show an anterograde amnesia (AA), i.e. they have great difficulty learning and remembering most kinds of new information. Immediate memory, however, is normal when this is assessed by forward digit span or the recency effect in free recall. There is usually a period of retrograde amnesia (RA), that is a loss of information acquired before the onset of the amnesia. This gap or period of RA is very variable in length and may range from a few minutes to decades. Previously acquired semantic knowledge about the world and implicit memory (remembering without awareness or conscious recollection) are typically intact in amnesic subjects. As the majority of patients with severe memory disorders present with additional cognitive problems such as attention deficits, word finding problems or slowed information processing, those with a classic amnesic syndrome are relatively rare.

Nevertheless, people with a ‘pure’ amnesic syndrome and people with more widespread cognitive deficits tend to share certain characteristics. In both cases, immediate memory is reasonably normal; there is difficulty in remembering after a delay or distraction; new learning is difficult and there is a tendency to remember things that happened a long time before the accident or illness better than things that happened a short time before.