Search Results

The pathophysiological process of Alzheimer's disease (AD) is thought to begin years, perhaps even decades, prior to the point of clinical diagnosis. Novel functional magnetic resonance imaging (fMRI) techniques have the potential to detect very early brain dysfunction that may predict cognitive decline and subsequent diagnosis of dementia. fMRI studies of subjects at risk for AD have been somewhat inconsistent, with some studies suggesting there may be a period of paradoxical “hyperactivity” very early in the course of prodromal AD, particularly in the hippocampus. It remains unclear whether early functional alterations are compensatory in the setting of early AD pathology or are sensitive indicators of neuronal toxicity. The combination of molecular and functional imaging techniques should prove valuable in elucidating the relationship between AD pathology and brain network dysfunction, and ultimately in predicting clinical decline.

This chapter examines the arguments that claim that human antisocial behavior—notably impulsivity, aggression, and related forms of criminal conduct—have neurobiological roots. While neurobiological evidence from genomics or functional brain imaging is likely to have limited traction in the criminal courtroom itself, a new diagram is nonetheless emerging in the criminal justice system as it encounters developments in the neurosciences. This does not entail a challenge to doctrines of free will or an exculpatory argument that “my brain made me do it,” as some have suggested. Rather it is developing around the themes of susceptibility, prediction, and precaution that have come to infuse many aspects of criminal justice systems as they have come to focus on questions of risk—risk assessment, risk management, and risk reduction.

Neuroimaging plays a major role in furthering our understanding of the orbitofrontal cortex (OFC). This chapter presents some of the technical challenges, limitations, and potential solutions with regard to using Magnetic Resonance Imaging (MRI) to study the OFC. The proximity of the OFC to the sinus results in signal loss and distortion due to inhomogeneity in magnetic susceptibility. Several techniques have proven useful in reducing signal loss and distortion including shorter echo times, thinner slice acquisitions, shimming, post-processing distortion correction using field maps, reduced data acquisition methods, parallel imaging, use of rapid acquisition trajectories including reverse spiral and spiral in-out sequences, gradient compensation, and tailored radiofrequency pulses. The advantages and disadvantages of each of these imaging techniques are discussed.

This chapter reviews advances in elucidating functional specialization for depth processing by the human brain while recognizing the complexity of the problem. It starts by discussing the conceptual and methodological challenges faced when investigating the neural circuits that process depth signals. It then reviews evidence for the specialization of different cortical areas in processing individual depth cues. Finally, it discusses work examining the representation of 3D structure from a combination of signals. The tenet of the chapter is that linking functional magnetic resonance imaging recordings with psychophysical measurements provides a strong basis from which to test the cortical representation of 3D structure.

This chapter reviews optical brain imaging and electrophysiology in the context of other available methodologies as they apply to aging research. Both methods emphasize the temporal aspects of the brain phenomena underlying cognition and thus allow for a closer parallel with cognitive studies using a mental chronometry approach to the study of aging. However, these two methods differ in the amount of localization information they provide, with electrophysiological methods yielding a coarser spatial description of brain activity and optical imaging meshing temporal and spatial information at a finer level. The spatial resolution of optical imaging may be close to that reached with functional magnetic resonance imaging (fMRI) or positron emission tomography (PET), especially when data from a number of subjects are combined, which leads to a loss of resolution for all techniques.

Neuroimaging techniques are among those most relied upon to tell us about the neural functions that underlie human behavior. Brain imaging evidence is the neuroscience evidence most likely to be introduced in legal proceedings. This chapter introduces magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) techniques, and lays out their capabilities and limitations. It also introduces principles of good experimental design and analysis, which are key components of fMRI experimentation, and essential to understand if one is to appreciate the significance of neuroimaging research. We conclude this chapter with a detailed discussion of common misconceptions regarding the interpretation of neuroimaging results, and a brief practical guide for interrogating the quality of neuroimaging research as well as its potential relevance to legal matters.

This chapter addresses the different roles of the left and right anterior insular cortex (AIC). It begins by noting evidence that the left AIC and the right AIC were activated asymmetrically in many of the functional magnetic resonance imaging (fMRI) studies mentioned in the preceding chapters. The chapter then details two recent reviews that document a consistent pattern of asymmetric activation of the amygdala and insular cortex, as well as the gender differences that had obscured this pattern. The accumulated evidence from years of work in psychology shows that electroencephalographic activation in the left frontal hemisphere correlates with positive affect and approach motivation, and that activation in the right frontal hemisphere correlates with negative affect, cortisol release, sympathetic arousal, and avoidance motivation. The chapter also describes evidence that supports the opponent inhibition model and the nature of emotional imbalance.

Previous studies on declarative memory function in epilepsy using functional magnetic resonance imaging (fMRI) have primarily pursued two aims: the localization or lateralization of the seizure focus and the reorganization of declarative memory functions; and the pre-surgical prediction of memory outcome after surgical resection within the temporal lobe (TL). It has been demonstrated that medial temporal lobe (MTL) activation patterns differ between left- and right-sided MTL epilepsy patients, which in turn can be differentiated from healthy control subjects. It has further been shown that the functional integrity of the ipsilesional as well as the contralesional MTL can contribute to the prediction of memory outcome after surgery. Recently, the evaluation of alterations of MTL connectivity patterns, as assessed with fMRI, has gained some attention. It has been demonstrated that circumscribed brain damage, like hippocampal sclerosis, may exert effects on functionally connected but remote regions. However, in contrast to pre-surgical language fMRI, memory fMRI in most centres has not been established as a standard pre-surgical diagnostic tool. This chapter argues in favour of further development of the technique and considers memory fMRI to be potentially informative, especially regarding pre-operative prediction of memory outcome and, therefore, patient counselling.

Most brain-computer interfaces (BCIs) currently under development use the brain's electrical signals. Nevertheless, nonelectrical metabolic signals also have potential for use in BCI development. Two methods currently available for measuring brain metabolic activity that are of greatest immediate interest for BCI development are: functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI). fNIRS has the advantages of being noninvasive and inexpensive. fMRI has the advantages of being noninvasive and providing very high spatial resolution. This chapter focuses on BCIs based on fNIRS and fMRI methods. It reviews the fundamental principles underlying their use, the factors important in their use for BCIs, the kinds of BCI applications that are most promising, and possible future directions and challenges.

This chapter concentrates on the representation of pain in the human brain, covering relevant work from neuroelectric and neuromagnetic source imaging (ESI and MSI), functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), positron emission (PET), and single photon emission computed tomography (SPECT) performed in healthy humans during acute pain, as well as studies performed in chronic pain sufferers. The focus is on the central imaging of pain in humans, although animal studies will be included when necessary. The chapter discusses persistent research questions and methodological developments related to imaging the central representation of pain in humans.

This chapter presents excerpts from the Jülich workshop, which represent the main issues that arise when one attempts to reconcile the multiple perspectives that currently exist on Broca's region. Topics covered include anatomy and localization, diversity of functional analyses of language, representation and processing, language development, functional connectivity, functional imaging, and lesion studies.

The clinical spectrum of hippocampal dysfunction encompasses a wide range of neuropsychiatric symptoms. The present chapter aims at addressing the hippocampal involvement in the most common form of memory disorders, that is Alzheimer’s disease (AD), focusing on neurobiological changes revealed by structural and functional imaging. AD results in progressive brain atrophy and inevitable neurological deterioration. Routine clinical evaluation of cognitively impaired elderly subjects includes structural computed tomography or magnetic resonance imaging (MRI), and, for example, the presence of atrophy in the hippocampus and other medial temporal lobe memory structures strongly supports the diagnosis of AD. Clinical functional MRI has proved to be an interesting tool in investigating the neural correlates of cognitive impairment characteristic of AD in vivo and has provided novel insights into the pathognomonic alterations in the hippocampal formation and related whole-brain memory networks. In addition to clinical AD, this chapter reviews recent advances in our understanding of the neuroimaging correlates of subjects at increased risk to develop AD, such as subjects with amnestic mild cognitive impairment and cognitively intact elderly subjects carrying the apolipoprotein E ε4 allele, focusing again on the most intensively studied structure, the hippocampus. Large-scale, worldwide, multimodal imaging studies on predictors of AD are ongoing and there is great hope that imaging of the hippocampus and related memory structures would facilitate early diagnosis of AD and other dementias as well as improve treatment options of these devastating diseases in the near future.

This chapter presents a synopsis of the representation of language functions in the brain with a focus on disorders based on three sources of information: lesion studies (i.e., what is known from the effects of pathology upon language behaviour in patients); the anatomical interpretation of normal function based on physiological measurements during language operations in healthy subjects; and a combination of the two; namely, physiological measurements recorded during language processing in aphasic patients.

In order to survive, most animals including humans need to be able to learn and adapt flexibly their behavior so that optimal choices can be made in an uncertain environment. This chapter reviews functional neuroimaging and neuropsychological studies on the nature of the orbitofrontal cortices (OFC) contribution to adaptive and flexible behavior in humans. These studies indicate that the OFC encodes the reward and punishment value of stimuli, maintains flexible representations of predicted reward and punishment value (using both stimulus substitution and CS-specific coding mechanisms), encodes errors in reward prediction, and signals future behavioral choice. The OFC shows heterogeneous response profiles with distinct regions mediating each of these functions. The relationship of the OFC to other brains regions processing reward is also discussed.

This chapter addresses the recent findings from studies of visual motion processing, eye movements, and reading. It specifically outlines the brain-imaging studies that have studied cortical responses to visual motion. It then provides studies that explore the cortical control of reading and evidence for the involvement of cortical areas in reading disabilities. It assesses the current findings on functional imaging of human cortical responses to visual motion. In addition, it deals with the influences associated with stimulus properties. The results of many groups suggest that several cortical areas respond selectively to visual motion. Different visual areas also respond to complex optic flow fields. Moreover, the data indicate that changes in the subject's attention can modify the blood oxygen level-dependent (BOLD) response to visual stimulation. Attention to different aspects of moving stimuli can lead to differences in the response. The role of pursuit eye movements in motion perception and the resultant pattern of BOLD responses are also considered. The task-dependent effects of pro- and anti-saccades, variations in the amplitude and frequency of saccades, and the difference between saccadic eye movements and smooth pursuit are also explained. Finally, it describes the results linked to reading and disorders of reading.

Musical imagery, or the deliberate use of imagination by musicians, has traditionally been viewed and considered as the ability to imagine sounds even when no audible sounds are present. However, imagery as used by musicians involves not only sounds but also the physical movements required to create sounds, a ‘view’ of the score or an instrument, and the emotions a musician wishes to express in performance. Current research is considering imagery use for functions including developing and enhancing expressivity during practice and performance, assisting with learning and memorizing music, pre-experiencing performance situations, and assisting in the prevention and treatment of playing-related injuries. A growing body of research employing functional magnetic resonance imaging (fMRI) suggests that functional equivalence exists between live and imagined performances within the auditory and motor systems involved in musical performance. This chapter explores the theories and findings this research has produced, together with the implications such findings have for performing musicians. Beyond understanding imagery at a functional level, the ways in which musicians engage with imagery are also of particular interest.

This chapter reviews functional imaging and electrophysiological studies addressing the cerebral organization of speech motor control. Functional imaging studies, based upon the production/repetition of lexical and non-lexical mono- or polysyllabic items, point at a ‘minimal brain network’ of motor aspects of speech production, encompassing the supplementary motor area (SMA) within the medial wall of the frontal lobe, opercular parts of the precentral gyrus and posterior components of the inferior frontal gyrus (Broca's area), the anterior insula at the floor of the lateral sulcus, the ‘mouth region’ of the primary sensorimotor cortex, the basal ganglia, thalamus, and the cerebellar hemispheres. Depending upon task demands and the selected activation contrasts, hemodynamic responses of other cerebral structures such as the superior temporal gyrus and lower parietal areas may emerge as well. Most noteworthy, functional imaging techniques now begin to provide new insights into the pathomechanisms of dysarthric deficits such as abnormalities of speaking rate in Parkinson's disease or in cerebellar ataxia.

Hippocampal sclerosis (HS) is the commonest cause of temporal lobe epilepsy which accounts for 3–50% of all epilepsy syndromes. This chapter reviews the pathological substrate of HS and mesial temporal sclerosis and how this relates to epileptogenesis and seizures. It then discusses the clinical picture of different forms of temporal lobe epilepsy and common findings on electroencephalography and imaging. Invasive and non-invasive diagnostic tools assessing epileptogenicity of the hippocampus are reviewed. Finally, the chapter presents an overview of management options available for patients with temporal lobe epilepsy.