(p. xiii) An explosive proliferation of brain imaging methods began toward the closing of the 20th century and continues unabated ever since. Some methods, like magnetic resonance imaging (MRI), reveal with ever-increasing clarity gross structural and microstructural details of the anatomy of the brain. Others, like positron emission tomography (PET), reveal the distribution of receptors for particular neurotransmitters over its entire volume. Still others, like diffusion tensor imaging (DTI), allow us glimpses of the functional integrity of white matter tracts. Finally, methods such as magnetoencephalography and magnetic source imaging (MEG, MSI) enable us to capture the extremely rapid traffic of signaling activity among neurons and, in conjunction with the MRI, enable us to visualize the structures in which that traffic transpires. Moreover, methods like PET or single photon emission tomography (SPECT), which have also evolved in parallel, make it possible to visualize differential rates of metabolism in the different brain structures, and methods like functional MRI (fMRI) and PET make it possible for us to image local blood flow rates in different brain regions contingent on the rates of neuronal metabolism and signaling.
Those methods that capture rapidly changing brain events (electrophysiological, metabolic, and hemodynamic) go by the name of functional brain imaging methods. They are used with increasing frequency in the field of systems neuroscience in general and of neuropsychology in particular for the following three main purposes: first, for the purpose of disclosing the brain processes necessary for the various behavioral and psychological functions or their constituent operations (whether cognitive, linguistic, or affective); second, for the purpose of visualizing aspects of brain activity uniquely associated with various behavioral and psychological states and traits, both normal and pathological; and, occasionally, third, for visualizing brain activity patterns specific to products of psychological functions such as particular concepts or percepts.
For the purpose of visualizing the neurophysiological aspects of behavioral or psychological traits and states, the distribution of specific receptors and the functional integrity of white matter tracts, the methods of PET and DTI are acquiring increasing importance.
Judging from the sheer volume of research output in the field of cognitive neurosciences, neuropsychology, and related fields, it appears that functional neuroimaging, especially through the use of fMRI that furnishes correlations between the state of the brain and specific aspects of behavior and mentation, has become the method of choice on par with the time-honored clinical method that furnishes (p. xiv) causal links between the brain and aspects of behavior and mentation. The complementarity of the two methods holds promise for solving a host of riddles of abiding theoretical and, at times, of urgent practical interest.
But, unlike the clinical method and other interventional methods of similar formal structure (e.g., methods involving experimental lesions, whether permanent or reversible, such as those produced by direct cortical stimulation) with which virtually all neuropsychologists are familiar, the functional neuroimaging methods remain largely opaque to most by virtue of their rapidly evolving technical aspects, their relative novelty, and their complexity. As a result, many cognitive psychologists and neuropsychologists are not in a position to appraise critically the research output of the functional neuroimaging they encounter in the professional literature or use the methods efficiently. And that inability results, quite often, in the accumulation of nonreplicable data and in the drawing of unwarranted inferences from such data as are available. (For relevant critiques and cautionary notes for the proper use and interpretation of functional neuroimaging, see, e.g., Papanicolaou, 2007; Logothetis, 2008; Aue, Lavelle, & Cacioppo, 2009).
To ameliorate matters, in the first part of this volume, we will describe the technologies for collecting relevant data, we will recount the techniques of deriving functional images from them, and, most importantly, we will systematically juxtapose the basic facts (whether technical or physiological) and the principles on which the correct use of the former and the requisite choice of the latter depends. Our emphasis on basic principles is motivated by the following two considerations: first, by the fact that both techniques and technologies evolve at extremely rapid rates so that many considered state-of the-art today will be dated by tomorrow, whereas the basic facts and principles alluded to earlier, although not immutable, are amended at a much slower pace. Second, because the facts and principles in question constitute the basis for the methods already in use and provide the necessary pragmatic constraints that should guide their improvement. Details of the various techniques and technologies are, of course, also important and will be covered in the first part of this book in sufficient detail to enable the reader to interpret reports in the literature involving these methods. In the second part of the book, an assessment of new knowledge gained and old ideas strengthened through the use of functional neuroimaging will be presented.
Aue, T., Lavelle, L. A., & Cacioppo, J. T. (2009). Great expectations: What can fMRI research tell us about psychological phenomena? International Journal of Psychophysiology, 73(1), 10–16. doi: 10.1016/j.ijpsycho.2008.12.017Find this resource:
Logothetis, N. K. (2008). What we can do and what we cannot do with fMRI. Nature, 453(7197), 869–878. doi: 10.1038/nature06976Find this resource:
Papanicolaou, A. C. (2007). What aspects of experience can functional neuroimaging be expected to reveal? International Journal of Psychophysiology, 64(1), 101–105.Find this resource: