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Relationships between motor potentials and CNV
706
INTERNATIONAL FEDERATION - 7TH CONGRESS
three-field tachistoscope was observed throughout with fixation maintained upon the center of a cross inscribed in a circle. The change in the figure, which constituted the Si, was effected by having an open sector pointing right or left. In the information situation the S d of high or low pitch carried information agreeing with that in the Si and thus allowed the subject to prepare for the correct response following Si. In the noinformation situation the Sd was always of high pitch and simply marked time until the Si. Instructions to the subject determined whether Sd would be informational or not. Cortical evoked potentials were recorded from somatosensory and vertex scalp electrodes, using long time-constant amplifiers. Averages were obtained by means of a CAT computer. Reaction times were measured from the Si. Results show that there are significant differences in the nature of the CNV under the different conditions.
146. Relationships between motor potentials and CNV.-K. Syndulko (Los Angeles, Calif., U.S.A.). The purpose of this experiment was to determine what relationships exist between the motor potential (MP) and the contingent negative variation (CNV). Each human subject was studied under three different conditions. Condition I was a choice reaction time task in which the subject was instructed to make a right or left hand movement, after presentation of one of two visual patterns. Condition I! involved the same stimuli and responses, but included a tone stimulus preceding both visual stimuli by 1 sec. In Condition III the tone was high or low indicating which of the two visual patterns was to follow and allowing the subject to anticipate the specific responses he was to make. The visual stimuli were presented via 2 channels of a 3-channel tachistoscope. The third channel was used to display a continuously present fixation point. Subjects were given practice trials before each of the three conditions. Steady potential changes were recorded at sites presumed to overlie the motor hand area of each hemisphere as well as from points anterior and posterior to the motor sites, from the vertex and from a site on the forehead to monitor eye movements. EMG activity was recorded from forearm muscles involved in the response. Both MPs and CNVs were averaged either backward from the response or foreward from the warning stimulus. The plan of the experiment permitted comparison of motor potentials which are assumed to arise from a specific locus, and CNVs, which are
assumed to have a different distribution. Condition I provides an imperative stimulus to a motor response but without warning and anticipation, Condition II provides only general expectancy and a pre-imperative stimulus period favoring CNV, and Condition III provides a specific and directed motor expectancy favoring the MP.
147. Behavioral and electrophysioiogical responses in a two flash discrimination task in the cat.-C, K. Peck (Los Angeles, Calif., U.S.A.). The purpose of this study was to train cats to discriminate two brief flashes presented as a pair from a single flash and then to reduce the temporal interval between the paired flashes until discrimination of two from one was no longer possible. Electrodes implanted in the optic tract, lateral geniculate body and the visual cortex permitted concurrent recording of responses to the visual stimuli. The behavioral task associated with this visual temporal discrimination involved a "go/no-go" procedure. On each trial the stimulus was either a single flash or a pair of flashes separated by a variable interval. During initial training the interflash interval was 250 msec but was subsequently reduced to a value as low as 20 msec which was well below the behavioral threshold at approximately 75 msec. Stimuli were presented only when the cat faced a transparent plastic panel upon which the flashes appeared. On any one trial the stimulus was repeated at 1.5 sec intervals until 5 stimuli had been presented or until the cat pressed the panel. A press following a paired flash provided a milk reward; a press following a single flash delayed the start of the next trial 15 sec. Fairly stable behavioral thresholds have been obtained and data will be presented concerning these and associated electrical responses to the flashes at each of the levels of the visual system sampled. Of particular interest is the question whether separation of the responses to the two flashes occurs when the behavioral discrimination is just possible as opposed to when it is not.
148. Polygraphy and its applications in the study of stabilized medullary lesions.-A. Heilporn (Brussels, Belgium). The author presents findings from 500 cases of medullary lesions all with chronic and severe sequelae. Special emphasis is laid on changes in the vasomotor and thermoregulatory functions, in blood pressure and cardiac rhythm, in their relation to type and level of the lesion. Polygraphic recordings were made simultaneously from regions above and below the level of the lesion under conditions of rest and of varying body positions and body temperature. Emphasis is
INTERNATIONAL FEDERATION - 7TH CONGRESS
three-field tachistoscope was observed throughout with fixation maintained upon the center of a cross inscribed in a circle. The change in the figure, which constituted the Si, was effected by having an open sector pointing right or left. In the information situation the S d of high or low pitch carried information agreeing with that in the Si and thus allowed the subject to prepare for the correct response following Si. In the noinformation situation the Sd was always of high pitch and simply marked time until the Si. Instructions to the subject determined whether Sd would be informational or not. Cortical evoked potentials were recorded from somatosensory and vertex scalp electrodes, using long time-constant amplifiers. Averages were obtained by means of a CAT computer. Reaction times were measured from the Si. Results show that there are significant differences in the nature of the CNV under the different conditions.
146. Relationships between motor potentials and CNV.-K. Syndulko (Los Angeles, Calif., U.S.A.). The purpose of this experiment was to determine what relationships exist between the motor potential (MP) and the contingent negative variation (CNV). Each human subject was studied under three different conditions. Condition I was a choice reaction time task in which the subject was instructed to make a right or left hand movement, after presentation of one of two visual patterns. Condition I! involved the same stimuli and responses, but included a tone stimulus preceding both visual stimuli by 1 sec. In Condition III the tone was high or low indicating which of the two visual patterns was to follow and allowing the subject to anticipate the specific responses he was to make. The visual stimuli were presented via 2 channels of a 3-channel tachistoscope. The third channel was used to display a continuously present fixation point. Subjects were given practice trials before each of the three conditions. Steady potential changes were recorded at sites presumed to overlie the motor hand area of each hemisphere as well as from points anterior and posterior to the motor sites, from the vertex and from a site on the forehead to monitor eye movements. EMG activity was recorded from forearm muscles involved in the response. Both MPs and CNVs were averaged either backward from the response or foreward from the warning stimulus. The plan of the experiment permitted comparison of motor potentials which are assumed to arise from a specific locus, and CNVs, which are
assumed to have a different distribution. Condition I provides an imperative stimulus to a motor response but without warning and anticipation, Condition II provides only general expectancy and a pre-imperative stimulus period favoring CNV, and Condition III provides a specific and directed motor expectancy favoring the MP.
147. Behavioral and electrophysioiogical responses in a two flash discrimination task in the cat.-C, K. Peck (Los Angeles, Calif., U.S.A.). The purpose of this study was to train cats to discriminate two brief flashes presented as a pair from a single flash and then to reduce the temporal interval between the paired flashes until discrimination of two from one was no longer possible. Electrodes implanted in the optic tract, lateral geniculate body and the visual cortex permitted concurrent recording of responses to the visual stimuli. The behavioral task associated with this visual temporal discrimination involved a "go/no-go" procedure. On each trial the stimulus was either a single flash or a pair of flashes separated by a variable interval. During initial training the interflash interval was 250 msec but was subsequently reduced to a value as low as 20 msec which was well below the behavioral threshold at approximately 75 msec. Stimuli were presented only when the cat faced a transparent plastic panel upon which the flashes appeared. On any one trial the stimulus was repeated at 1.5 sec intervals until 5 stimuli had been presented or until the cat pressed the panel. A press following a paired flash provided a milk reward; a press following a single flash delayed the start of the next trial 15 sec. Fairly stable behavioral thresholds have been obtained and data will be presented concerning these and associated electrical responses to the flashes at each of the levels of the visual system sampled. Of particular interest is the question whether separation of the responses to the two flashes occurs when the behavioral discrimination is just possible as opposed to when it is not.
148. Polygraphy and its applications in the study of stabilized medullary lesions.-A. Heilporn (Brussels, Belgium). The author presents findings from 500 cases of medullary lesions all with chronic and severe sequelae. Special emphasis is laid on changes in the vasomotor and thermoregulatory functions, in blood pressure and cardiac rhythm, in their relation to type and level of the lesion. Polygraphic recordings were made simultaneously from regions above and below the level of the lesion under conditions of rest and of varying body positions and body temperature. Emphasis is