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This volume is the second in "The Downstate Series of Research in Psychiatry." It is aseries devoted to the presentation of sig nificant research with relevance for both clinicians and researchers in the multiple subfields of psychiatry. This book focuses on the interactions between psychic phenomena and physical processes as studied by evoked brain potentials. It presents material concerned with physiological and psychological unifying processes, as weIl as research concerning technology and methods of obtaining meaningful measurements. As such it is representative of biological psychiatry at its best. Thus, it represents another step in new directions in psychiatric research but not an unanticipated direction. Scientific investigation into the human psyche took an unex pected turn when Sigmund Freud in the last part of the 19th Century turned his attention from neurological concerns to those of psychol ogy. His first attempts at explanations as noted in the "project," included a heavy emphasis on the biological substrate of behavior.
The major objective of the research effort has been to study the relationship between human sensory mechanisms and their perceptual correlates, as reflected in evoked cortical potentials. The visual evoked potential (VEP) complex and motor evoked potentials (MEPs) have been of particular interest.
From August 25 - 28, 1978 a conference on averaged evoked po tentials was held at Konstanz, West Germany. Research on human evoked potentials has progressed rapidly in the past decade, and a series of international conferences have served to maintain com munication between active workers in the field. Among the organiza tions that have a tradition of supporting such mUlti-national com munication are the North Atlantic Treaty Organization Scientific Affairs Division, the u.s. Office of Naval Research and the German Research Society (Deutsche Forschungsgemeinschaft). We have been fortunate to have the support of all three. In the early stages of planning, a committee was formed composed of Professors Rudolph Cohen (Konstanz), Otto Creutzfeldt (Goettingen), John Desmedt (Brussels), A.M. Halliday (London), Anthony Remond (Paris) and Herbert Vaughan (New York). A call for papers was circulated as widely as possible, and this committee carried out the difficult task of selecting a limited number of participants from a large number of excellent abstracts. At the same time Professor Cohen of the University of Konstanz was generous enough to shoulder the task of playing host to the conference. His thoughtful arrangements contributed enormously to the comfort of the participants. He and his colleagues also engi neered an ideal ambience for sharing of ideas and observations, while the University of Konstanz generously provided audio-visual support.
Two experiments investigated a change in the late positive activity (200 to 550 msec) of the visual evoked potential (VEP). This 'P2-effect, ' maximal at the occiput, appeared related to cognitive aspects of information processing. Results did not support an interpretation of the P2-effect in cognitive terms (Experiment 1) but rather in terms of shifts in cortical arousal and in expectancy (Experiment 2). In both studies, subjects viewed letter-pair stimuli, e.g., HH or bD, responding when they saw a stimulus (SIGHT task), or when they determined whether the two letters were the same or different in either size or name (SIZE and NAME tasks). Reaction times increased from the SIGHT to the SIZE to the NAME task, objectifying the increase in task complexity. The P2-effect occurred with the increase in task complexity from the SIGHT to the SIZE task, but did not increase further in the NAME task or show asymmetry in relation to lateralized processing. In Experiment 2, slow wave shifts were observed. These slow waves revealed subject-specific ranges of cortical arousal. The P2-effect appeared to result primarily from continued or noncontinued expectancy following stimulus reception. This work demonstrates the difficulty involved in controlling for and evaluating the effects of shifts in cortical arousal and in expectancy during cognitive information processing. The results are relevant to the question of CNV-P300 dissociability.
This book covers all aspects of evoked potentials (EPs) utilized clinically in evaluating the functional integrity of somatosensory, auditory, motor, and visual pathways in the nervous system. It explores techniques needed to correctly perform EPs, and discusses these clinical neurophysiological tests that are performed in academic institutions and large community hospitals. Concise and comprehensive, this case-study rich text is divided into five chapters. Beginning with basic principles of evoked potential recording, the first chapter discusses signal enhancement and limitations of signal averaging. Chapter two then provides an overview of brainstem auditory EPs. Subsequent chapters then present visual EPs and somatosensory evoked potentials. Finally, the book concludes with clinical applications of transcranial magnetic stimulation, as well as a brief discussion of the techniques of transcranial electrical motor evoked potentials during intraoperative monitoring. Clinical Evoked Potentials: An Illustrated Manual functions as an essential reference for neurologists neurosurgeons, anesthesiologists, clinical neurophysiologists, and EP technologists, who are involved with the recording and interpretation of EPs primarily for diagnostic purposes.
Considerable evidence exists that visual sensory information is analyzed simultaneously along two or more independent pathways. In the past two decades, researchers have extensively used the concept of parallel visual channels as a framework to direct their explorations of human vision. More recently, basic and clinical scientists have found such a dichotomy applicable to the way we organize our knowledge of visual development, higher order perception, and visual disorders, to name just a few. This volume attempts to provide a forum for gathering these different perspectives.