Improving our understanding of speech and language outcome in neurosurgery patients

Malignant gliomas remain incurable and result in more years of life lost than any other tumours. Surgical resection is strongly recommended but carries a risk of causing functional impairment. This thesis aims to demonstrate how state-of-the-art functional magnetic resonance imaging (fMRI) language paradigms can contribute to neurosurgical planning. The first three experiments use a multitask fMRI language paradigm to functionally segregate left posterior temporal and left posterior frontal regions involved in the perception and production of speech. Experiment 1 demonstrated three functionally distinct responses in the left posterior superior temporal sulcus (STS), left temporo-parietal junction and anterior ascending terminal branch of the left STS. Experiment 2 validates these findings in an independent group of participants, increasing confidence that they are robust. Experiment 3 dissociates the response of three different parts of the left premotor cortex during speech production. Experiment 4 shows that left posterior temporal regions are more consistently activated, in neurotypical controls, when a picture naming task presents pairs of objects rather than single objects. Further work could therefore test whether paired object naming is a more sensitive task for pre- and intra-operative language mapping. Finally, Experiment 5 found that successful reading before and after surgery, in two patients with gliomas affecting the left temporo-parietal junction, enhanced activation in bilateral perirhinal regions that were associated with semantic identification of visually presented objects in neurotypical controls. Future studies can now test whether patients who undergo resection of the left temporo-parietal junction have better reading, post-surgery, when bilateral perirhinal activation is enhanced prior to surgery. Taken together, this work expands our knowledge of the functional anatomy of language, proposes a new way of utilising fMRI data from neurotypical controls to tailor pre- and intra-operative language mapping strategies and provides an insight into how the reading system reorganises itself after brain damage

Empirical and methodological investigations into novelty and familiarity as separate processes that support recognition memory in rats and humans

There is a prevalent assumption in the recognition memory literature that the terms “novelty” and “familiarity” are words ascribed to differing extremities of a single memory strength continuum. The aim of the current thesis was to integrate experimental methodologies across human and rodents to further investigate novelty processing at both a cognitive and neural level, and assess whether it is dissociable from familiarity processing. This dissociation was questioned at a cognitive level in human participants in Experiments 1 to 3 and at a neural level in rats in Experiment 4 and 5. Participants were found to differentially assess novelty and familiarity when making confidence judgements about the mnemonic status of an item (Experiment 1). Additionally, novelty and familiarity processing for questioned items were found to be dissimilarly affected by the presence of a concurrent item of varying mnemonic statuses (Experiment 2 and 3). The presence of a concurrent familiar item did not impact novelty processing in the perirhinal cortex (Experiment 4 and 5), yet disrupted the neural networks established to be differentially engaged by novelty and familiarity (Experiment 5). These findings challenge the assumption that the terms “novelty” and “familiarity” relate to a single recognition memory process. Finally, to allow integration of the findings from the human and rodent experiments, the relationship between measures or recognition memory obtained from spontaneous object recognition (SOR) task in rats and recognition memory measures estimated from signal-detection based models of recognition memory in humans was investigated (Experiment 6 and 7). This revealed that novelty preference in the SOR was positively correlated to measures of recognition memory sensitivity, but not bias. Thus, this thesis argues for the future inclusion of a novelty as a dissociable process from familiarity in our understanding of recognition memory, and for the integrations of experimental methodologies used to test recognition memory across species

A dual-route model of proactive interference in working memory and its application in schizotypy

Proactive interference (PI), the negative impact of previously encoded information on the ability to represent current information that is similar in some way, has recently been shown to impair working memory (WM) performance. In this thesis, two types of interference were separated, one related to the content of encoded information, the other to contextual aspects of encoded information. Context-related interference was altered by a manipulation of context, and was related to a quadratic serial position curve. This type of interference was related to the process of recollection, and was argued to be mediated by an associative mechanism in WM. Content-related interference was altered by a manipulation of content. This type of interference was related to the process of familiarity, and is argued to be mediated by a binding mechanism in WM. A further differentiation between the two types of interference was demonstrated in their relationship to positive and negative schizotypy traits. Current theories of the relationship between PI and WM suggest that it is mediated by a unitary process or mechanism. The findings here demonstrate the validity of a dual-route description of this relationship. In addition, they show the potential of distinguishing between a binding mechanism and an associative mechanism within the WM system. Finally, they demonstrate how this distinction between binding and associating may benefit an understanding of the relationship between schizotypy traits and cognition

Segmentation of experience and episodic memory across species

How continuous ongoing perceptual experience is processed by the brain and mind to form unique episodes in memory is a key scientific question. Recent work in Psychology and Neuroscience has proposed that humans perceptually segment continuous ongoing experience into meaningful units, which allows the successful formation of episodic memories. Despite accumulating work demonstrating that non- human animals also display a capability of episodic-‘like’ memory, whether non-human animals segment continuous ongoing experience into ‘meaningful’ episodic units is a question that has not been fully explored. Hence, the main goal of the research in this thesis aims to address whether a comparable segmentation process (or processes) of continuous ongoing experience occurs for non-human animals in their formation of episodic-like memory, as it does for humans in their formation of episodic memory. Chapter 2 argues that, similarly to humans, rats can use top-down like prediction-error processing in segmenting for subsequent memory to guide behaviour in an episodic-like spontaneous object recognition task. Chapter 3 suggests that mice readily incorporate conspecific-contextual information using episodic-like memory processing, indicating that conspecifics can act as a segmentation cue for non-human animals. Chapter 4 highlights that humans and rodents may similarly segment continuous ongoing experience during turns made around spatial boundaries. Chapter 5 argues that individual place cells can represent content of episodic nature, with the theoretical implication of this being discussed in relation to episodic memory. Thus, the results presented in this thesis, as well as re-interpretation of previous literature, would argue in favour of non-humans segmenting their experience for episodic-like memory. Finally, the evidence is evaluated in the context of whether episodic-like memory in non-human animals is simply just episodic memory as experienced in humans

On the role of the hippocampus in the acquisition, long-term retention and semanticisation of memory

Institute for Adaptive and Neural ComputationA consensus on how to characterise the anterograde and retrograde memory processes that are lost or spared after hippocampal damage has not been reached. In this thesis, I critically re-examine the empirical literature and the assumptions behind current theories. I formulate a coherent view of what makes a task hippocampally dependent at acquisition and how this relates to its long-term fate. Findings from a neural net simulation indicate the plausibility of my proposals. My proposals both extend and constrain current views on the role of the hippocampus in the rapid acquisition of information and in learning complex associations. In general, tasks are most likely to require the hippocampus for acquisition if they involve rapid, associative learning about unfamiliar, complex, low salience stimuli. However, none of these factors alone is sufficient to obligatorily implicate the hippocampus in acquisition. With the exception of associations with supra-modal information that are always dependent on the hippocampus, it is the combination of factors that is important. Detailed, complex information that is obligatorily hippocampally-dependent at acquisition remains so for its lifetime. However, all memories are semanticised as they age through the loss of detailed context-specific information and because generic cortically-represented information starts to dominate recall. Initially hippocampally dependent memories may appear to become independent of the hippocampus over time, but recall changes qualitatively. Multi-stage, lifelong post-acquisition memory processes produce semanticised re-representations of memories of differing specificity and complexity, that can serve different purposes. The model simulates hippocampal and cortical interactions in the acquisition and maintenance of episodic and semantic events, and behaves in accordance with my proposals. In particular, conceptualising episodic and semantic memory as representing points on a continuum of memory types appears viable. Support is also found for proposals on the relative importance of the hippocampus and cortex in the rapid acquisition of information and the acquisition of complex multi-model information; and the effect of existing knowledge on new learning. Furthermore, episodic and semantic events become differentially dependent on cortical and hippocampal components. Finally, as a memory ages, it is automatically semanticised and becomes cortically dependent

Brain Computations and Connectivity [2nd edition]

This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read on the Oxford Academic platform and offered as a free PDF download from OUP and selected open access locations. Brain Computations and Connectivity is about how the brain works. In order to understand this, it is essential to know what is computed by different brain systems; and how the computations are performed. The aim of this book is to elucidate what is computed in different brain systems; and to describe current biologically plausible computational approaches and models of how each of these brain systems computes. Understanding the brain in this way has enormous potential for understanding ourselves better in health and in disease. Potential applications of this understanding are to the treatment of the brain in disease; and to artificial intelligence which will benefit from knowledge of how the brain performs many of its extraordinarily impressive functions. This book is pioneering in taking this approach to brain function: to consider what is computed by many of our brain systems; and how it is computed, and updates by much new evidence including the connectivity of the human brain the earlier book: Rolls (2021) Brain Computations: What and How, Oxford University Press. Brain Computations and Connectivity will be of interest to all scientists interested in brain function and how the brain works, whether they are from neuroscience, or from medical sciences including neurology and psychiatry, or from the area of computational science including machine learning and artificial intelligence, or from areas such as theoretical physics

Cortical contributions to landmark integration in the rodent head direction system

Head direction (HD) cells in the rodent brain can use visual information about surrounding landmarks to ‘reset’ their represented orientation, to keep it aligned with the world (a process called landmark anchoring). This implies HD cells receive input from the visual system about the surrounding panorama and its landmarks. Which features in a panorama are used by the HD system? Can HD cells integrate raw luminance input from across the panorama, as might be subserved by subcortical visual processing? Alternatively, do HD cells need discretised landmarks with features, requiring more elaborate visual landmark processing and recognition? I present work addressing how visual information reaches the HD circuit in rats. In the first experiment, we ask whether HD cells require discrete landmarks to anchor to visual panoramas. We record HD cells in a landmark anchoring paradigm using a visual panorama containing a single gradient shifting gradually from black to grey to black. Although there was evidence HD cells could integrate information from this scene, cue control was weak and less reliable than anchoring to visual landmarks with edges. In the second experiment, I present HD cell recordings in rats with lesions of the lateral geniculate nucleus, the thalamic relay of the cortical visual pathway, to test whether subcortical vision is sufficient for landmark-anchoring. HD cells in these animals showed impaired anchoring to cue cards, and lesion extent correlated with the severity of the impairment. Together, these findings indicate that the cortical visual pathway is necessary for intact and stable landmark anchoring to visual cues. Although this process can use entire visual panoramas, it may be more precise if distinct features are available in the scene. Landmark processing in the brain may be complex, and further work could probe whether direct projections from visual cortex provide this information to the HD circuit

Object Recognition

Vision-based object recognition tasks are very familiar in our everyday activities, such as driving our car in the correct lane. We do these tasks effortlessly in real-time. In the last decades, with the advancement of computer technology, researchers and application developers are trying to mimic the human's capability of visually recognising. Such capability will allow machine to free human from boring or dangerous jobs