On the representation of semantic and motor knowledge. Evidence from brain damaged patients

When we think of an apple, do we actually feel the same as when we eat it? The central theme of this work is to understand whether the permanent representation of an object corresponds to a reactivation of sensations we perceived when we actually had it in our hands. A recent debate in cognitive neuroscience, in fact, is concerned with the possibility that the neural systems that mediate overt action and sensory experience are causally involved in the neural representation of actions and real objects. On the other hand, more classical models postulate a relative separation between the how system and the what system, the former being more related to action, the latter more related to visual and semantic object representation. Such a classical view does not deny that the two streams normally have a close interaction but, based on neuropsychological and behavioral evidence, it holds that they can work separately in the case of selective brain damage or in particular experimental conditions. In this thesis I will explore the possible role of the motor processes in understanding objects and actions by studying brain damaged patients performing a series of action- and object-related tasks. In Chapter I, I will briefly introduce the literature on the relationship between actions and concepts of both healthy and brain damaged subjects. Chapter II reports a study on a group of 37 stroke patients who have been tested for their ability to recognize and use objects, as well as to recognize and imitate actions. In this group I found double dissociations suggesting that these tasks depend on separable cognitive processes. In Chapter III, I will describe a double dissociation study in which we compared the performance of two patients with apraxia with that of two patients with semantic impairment, and I will show how the object knowledge of the latter patients decline in time although they maintained relatively good ability to use objects. Finally, in Chapter IV I will analyze the performance of a new series of apraxic patients on a set of tasks aimed at testing a computational model which accounts for the errors that apraxic patients make when using objects. The results will not completely fit with the embodied theories of knowledge. Rather, they are compatible with \u201cdisembodied\u201d models that postulate a separation between the object conceptual knowledge and the sensory-motor input and output systems

Exploring aspects of memory in healthy ageing and following stroke

Memory is critical for everyday functioning. Remembering an event with rich detail requires the ability to remember the temporal order of occurrences within the event and spatial locations associated with it. But it remains unclear whether it also requires memory for the perspective from which we encoded the event, whether these three aspects of memory are affected following stroke, and which are the key brain regions upon which they rely. These questions are explored in this thesis. In the first study presented here, I examined young and elderly healthy subjects with an autobiographical memory interview and a 2D spatial memory task assessing self-perspective, and found no correlation between performance on these tasks. In the second experimental study, by assessing stroke patients on a 3D spatio-temporal memory task, I found that damage to the right intraparietal sulcus was associated with poorer memory for temporal order. However, voxelwise analyses detected no association between parietal lobe regions and accuracy in the egocentric condition of this task, or between medial temporal lobe regions and accuracy in the allocentric condition, one possible reason being that performance was near ceiling. In the third experimental study, by assessing a considerably larger group of stroke patients on a spatial memory task, I found that, as a group, patients performed worse than healthy controls, and performance was correlated with an activities of daily living scale. A spatial memory network was identified in right (but not left) hemisphere stroke patients. These findings provide evidence that spatial memory impairment is common after stroke, highlight its potential functional relevance, and increase our understanding of which regions are critical for remembering temporal order and spatial information. Furthermore, they suggest a dissociation between the mechanisms underpinning recall of 2D scenes over relatively short intervals versus remembering of real-life events across periods of many years.Open Acces

Handbook on clinical neurology and neurosurgery

HANDBOOKNEUROLOGYNEUROSURGERYКЛИНИЧЕСКАЯ НЕВРОЛОГИЯНЕВРОЛОГИЯНЕЙРОХИРУРГИЯThis handbook includes main parts of clinical neurology and neurosurgery

Unawareness of paralysis following stroke: an existential-phenomenological inquiry into the paradox of anosognosia

We inescapably experience the world through our body. Yet as our embodiment itself is the background of all our everyday experience, it appears to be experienced quietly. We tend to take for granted that our body is present in and contributing to all experience, as we also tend to take for granted the feeling that it belongs to us and it is under our control. However, certain neuropsychological disorders that arise after damage to the right hemisphere of the brain serve as a reminder that these feelings and intuitions cannot always be taken for granted. What is more ‘counter-intuitive’ than someone who is unaware of the fact that they can no longer move half their body? Or someone who cannot recognise their own arm or, leg as theirs? These disorders have troubled neurology, philosophy and psychology since the time of Charcot, Janet, Freud and Babinski and continue to represent frequent, largely unmet and poorly studied clinical challenges. The present thesis aims to explore from an interdisciplinary vantage point the way in which the body is experienced in people with such neuropsychological disorders following a stroke. More specifically, it aims to complement current scientific perspectives on these disorders with existential-phenomenological ideas regarding the experience of embodiment in these patients, with particular emphasis on the ‘pre-reflected’ dimensions of embodiment and their derivatives in mental life as highlighted by the philosopher Merleau-Ponty. The empirical part of the thesis involves behavioural and neuroimaging methodologies from the field of neuropsychology, including two case series and one single case study (total N = 14). Three hypotheses inspired by the early writings of Merleau-Ponty on embodiment were explored in these three studies, respectively: (a) whether patients with motor unawareness have a ‘pre-reflective’ awareness of their deficits; (b) whether such forms of pre-reflective awareness may paradoxically contribute to their explicit unawareness and (c) whether insights generated by the above two studies could be translated to a psychophysical intervention that can help a patient recover her explicit awareness of her paralysis. The results of these studies confirmed all three hypotheses, with some theoretical constraints that are discussed in each chapter. More generally, the results of these studies are discussed in relation to both scientific and philosophical theories of body awareness and most importantly in relation to clinical challenges and the scope of existential counselling psychology. I argue that these disorders allow a unique insight into how existential, counselling and psychotherapeutic psychology can position its practice in relation to some of these paradoxical ways of being-in-the-world that are not habitually so ‘visible’, unless revealed by brain damage. These considerations apply particularly to the more general paradox of psychotherapeutic clients who frequently come to therapy consciously hoping to change their habitual ways of being-in-the-world while implicitly, yet with almost equal force, they may hope not to change their commitment to the world

Effects of cholinesterase inhibition on brain function

Pharmacological-functional imaging provides a non-invasive method by which the actions of neurotropic drugs on the human brain can be explored. Simply put, it assesses how neural activity patterns associated with cognitive functions of interest are modified by a drug challenge. Since one of the most widely-used cognitive-enhancing drugs in clinical practice are cholinesterase inhibitors, this thesis applies pharmacological functional imaging to the question of understanding how such drugs work - both in healthy people and dementia. The experiments in this thesis describe how brain activations – as revealed by functional magnetic resonance imaging (fMRI) – are modulated by the cholinesterase inhibitor physostigmine, during tasks designed to isolate sensory, attentional, and memory processes. While non-human and human psychophysical studies suggest that all three of these cognitive functions are under the control of the endogenous cortical cholinergic system, understanding how neurobiological models of cholinergic function translate into human brain activation modulations is unclear. One main question that is particularly relevant in this regard, that recurs through all the experiments, is how physostigmine-induced neuromodulations differ between sensory-driven ‘bottom-up’, and task-driven ‘top-down’, brain activations. The results are discussed with reference both to non-human physiological data and to existing human cholinergic-functional imaging studies (fifty studies published to date), which are themselves reviewed at the outset. Furthermore, assumptions based upon the physical and physiological principles of pharmacological functional imaging, being critical to interpretation, are discussed in detail within a general methods section

Towards a structure of insight: a clinical and conceptual analysis

The concept of insight in mental illness is explored with the objective of developing a structural model of insight. This model, in turn, aims to provide a framework allowing the different clinical phenomena subsumed under the term 'insight' to be identified in a systematic manner. It is through the identification of, and differentiation between, such clinical phenomena that further progress can be made in the determination of the possible neurobiology underlying the different aspects of insight and insightlessness. The thesis is divided into 2 sections. The first section (chapters 1-5) examines and analyses the notion of insight into mental illness from its historical development as an independent concept to the ways in which insight has been conceptualised and explored in clinical psychiatry and related disciplines. The second section (chapters 6-8) focuses on developing a model for the structure of insight. This section represents an integration of both conceptual and empirical work. Thus, the issues arising from the analysis in the first section are examined critically in order to determine possible theoretical components to the concept of insight as a whole. The empirical work draws on 2 studies undertaken to explore insight clinically and which help to support some of the theoretical distinctions made between the constituents of insight. (Abstract shortened by ProQuest.)

Category deficits and paradoxical dissociations in Alzheimer's disease and Herpes Simplex Encephalitis

Original article can be found at: http://www.mitpressjournals.org Copyright Massachusetts Institute of Technology Press [Full text of this article is not available in the UHRA]Most studies examining category specificity are single-case studies of patients with living or nonliving deficits. Nevertheless, no explicit or agreed criteria exist for establishing category-specific deficits in single cases regarding the type of analyses, whether to compare with healthy controls, the number of tasks, or the type of tasks. We examined two groups of patients with neurological pathology frequently accompanied by impaired semantic memory (19 patients with Alzheimer's disease and 15 with Herpes Simplex Encephalitis). Category knowledge was examined using three tasks (picture naming, naming-to-description, and feature verification). Both patient groups were compared with age-and education-matched healthy controls. The profile in each patient was examined for consistency across tasks and across different analyses; however, both proved to be inconsistent. One striking finding was the presence of paradoxical dissociations (i.e., patients who were impaired for living things on one task and nonliving things on another task). The findings have significant implications for how we determine category effects and, more generally, for the methods used to document double dissociations across individual cases in this literature.Peer reviewe

Processing events : investigating event conceptualisation in aphasia

Some people with aphasia may have difficulty in talking about events because of trouble in processing situations in a language-ready fashion. A number of models of language production include a level at which messages are shaped to the demands of a particular language system. However, the relation between such conceptual processing and production in aphasia has been less fully explored. This study takes an empirical approach, investigating the relationship between the verb and sentence difficulties of six people with aphasia and their conceptualisation of events. Following a range of preparatory assessments, so individuals were hypothesised to have some difficulty in conceptualising events for language. Three novel tests were then devised to explore the skills of these individuals, and in one case, the whole group, in more detail. One test examines participants' focus over pictured situations, through their naming of the people and objects involved. A second probes the adoption of perspective over a particularly problematic situation type, investigating the effect of visual and linguistic cues on verb production. The third test focuses on gesture, exploring the relationship between verbal description and the production of action gestures. One participant's drawing of simple events was also probed using a recently developed assessment (Sacchett, 2005). In each case the results point to some differences between the participants with aphasia and a group of non-brain damaged speakers, thus providing support for the psychological reality of the notion of 'thinking for speaking' (Slobin, 1996) in aphasia. In addition, the test findings bring to light some previously hidden processing strengths. However, they also highlight the difficulty both of designing valid tests in this area and of accurately interpreting their results. The discussion considers the implications of the findings for therapy in aphasia, and for our understanding of the relationship between language loss and event conceptualisation