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Experimental paradigms and psychopathology
EXPERIMENTAL Chairman:
PARADIGMS
AND PSYCHOPATHOLOGY
D. PAPAKOSTOPOULOS
Burden Neurologrcul Institute,
Bristol, U.K.
Contributors: Stuart BUTLER (University of Birmingham) Geoff BARRETT (National Hospital) Hutch CURREY (Burden Neurological Institute) Demetrios PAPAKOSTOPOULOS (Burden Neurological
Institute)
Regardless of the nature of brisk, peripheral stimuli, the recordable response to this input to a normal peripheral nerve is a compound action potential with a triphasic waveform. This triphasic waveform is a consistent, readily identifiable and enduring feature of this response. However, in contrast the same stimulus may generate endless type of waveforms when the response to them is recorded from the scalp or brain. In fact this multiplicity of waveform can be seen in recordings from implanted electrodes sampling only a square ~llimeter of human cortex. Indeed this square millimeter of cortex does not need any stimulation to generate endless types of waveforms which are referred to as intrinsic activities. In the peripheral nervous system, the cardiovascular system or the electrodermal system, a controlled change in experimental conditions will result in a quantifiable modification of only some parameters (e.g. latency, amplitude etc.) of the ‘standard waveforms’ generated by these systems. Under such conditions the relationships of cause and effect can be repeatedly observed and finally understood. However, in the level of the alert human cortex, apparently trivial change in experimental conditions can drastically alter the shape of the related evoked waveforms together with the underlying intrinsic activities and sustained potentials. The term experimental paradigm, instead of experimental condition, could be used to refer to situations leading to alteration of ‘basic waveform’. Under these circumstances it is apparent that comparative quantification of the altered waveforms with the originals is necessarily based on arbitrary criteria as different entities are being compared. Therefore it has been very difficult to establish any relationship between the different types of activities. Because of these difficulties most investigators choose to study each particular brain waveform in isolation from the others. This is accomplished by utilising particular experimental paradigms, hopefully repeatable between- and withinsubjects. The criteria by which a particular investigator chooses experimental paradigms and the merits and achievements of each chosen one in clinical application and research in psychopathology is the subject of the workshop.
Stuart Butler will discuss paradigms suitable to be studied with intrinsic activities (EEG); Geoff Barrett will discuss paradigms with semanting and non-semanting single stimuli (EPs and ERPs); Hutch Curry will discuss paradigms with paired stimuli (CNVs); and Demetrios Papakostopoulos will discuss paradigms with self-paced tasks (BP, MCP, SPP). Although discussion is the objective, monologue could be the result.
PARADIGMS
AND PSYCHOPATHOLOGY
D. PAPAKOSTOPOULOS
Burden Neurologrcul Institute,
Bristol, U.K.
Contributors: Stuart BUTLER (University of Birmingham) Geoff BARRETT (National Hospital) Hutch CURREY (Burden Neurological Institute) Demetrios PAPAKOSTOPOULOS (Burden Neurological
Institute)
Regardless of the nature of brisk, peripheral stimuli, the recordable response to this input to a normal peripheral nerve is a compound action potential with a triphasic waveform. This triphasic waveform is a consistent, readily identifiable and enduring feature of this response. However, in contrast the same stimulus may generate endless type of waveforms when the response to them is recorded from the scalp or brain. In fact this multiplicity of waveform can be seen in recordings from implanted electrodes sampling only a square ~llimeter of human cortex. Indeed this square millimeter of cortex does not need any stimulation to generate endless types of waveforms which are referred to as intrinsic activities. In the peripheral nervous system, the cardiovascular system or the electrodermal system, a controlled change in experimental conditions will result in a quantifiable modification of only some parameters (e.g. latency, amplitude etc.) of the ‘standard waveforms’ generated by these systems. Under such conditions the relationships of cause and effect can be repeatedly observed and finally understood. However, in the level of the alert human cortex, apparently trivial change in experimental conditions can drastically alter the shape of the related evoked waveforms together with the underlying intrinsic activities and sustained potentials. The term experimental paradigm, instead of experimental condition, could be used to refer to situations leading to alteration of ‘basic waveform’. Under these circumstances it is apparent that comparative quantification of the altered waveforms with the originals is necessarily based on arbitrary criteria as different entities are being compared. Therefore it has been very difficult to establish any relationship between the different types of activities. Because of these difficulties most investigators choose to study each particular brain waveform in isolation from the others. This is accomplished by utilising particular experimental paradigms, hopefully repeatable between- and withinsubjects. The criteria by which a particular investigator chooses experimental paradigms and the merits and achievements of each chosen one in clinical application and research in psychopathology is the subject of the workshop.
Stuart Butler will discuss paradigms suitable to be studied with intrinsic activities (EEG); Geoff Barrett will discuss paradigms with semanting and non-semanting single stimuli (EPs and ERPs); Hutch Curry will discuss paradigms with paired stimuli (CNVs); and Demetrios Papakostopoulos will discuss paradigms with self-paced tasks (BP, MCP, SPP). Although discussion is the objective, monologue could be the result.