A subcortical correlate of P300 in man

Event-related potentials in visual and auditory target detection tasks were recorded simultaneously from the scalp, somatosensory thalamus and periaqueductal gray in a chronic pain patient with electrodes implanted subcortically for therapeutic purposes. Short latency tactile responses confirmed the location of the thalamic electrodes.Rare auditory stimuli which were detected by the subject were accompanied by a prominent P300 component at the scalp, and by negative activity at the subcortical sites with the same latency as the scalp positivity. This activity was not seen in responses to frequent non-target stimuli and was not dependent on an overt motor response.Similarly, rare visual stimuli generated a scalp P300 and negative activity subcortically; both scalp and subcortical waves had a longer latency than in the auditory experiment. The reaction time was similarly longer to visual targets.These data are inconsistent with a hippocampal generator for P300, but are consistent with a generator in the thalamus or more dorsally located structures.     

Effect of apomorphine injection into the nucleus accumbens on the limb preference in manipulation movements in rats

The concentration of dophamine and its derivates is known to correlate with the degree of handedness in manipulative movements in rodents. In this work we studied a possibility to changing handedness in rats by injection of a dopamine agonist into the nucleus accumbens. Retrieving food from a horizontal tube was used to determine the limb preference (10 food retrievals by the preferred limb). Then apomorphine was injected into the n. accumbens ipsilateral to the preferred limb in the course of 7 days. The same volume of buffer solution was injected into the contralateral n. accumbens. Just after the last injection the limb preference was tested. It was shown that the chronic injection of the non-specific agonist of dophamine receptors significantly changed the limb preference.     

Tendon displacements during voluntary and involuntary finger movements

In the human hand, independent movement control of individual fingers is limited. One potential cause for this is mechanical connections between the tendons and muscle bellies corresponding to the different fingers. The aim of this study was to determine the tendon displacement of the flexor digitorum superficialis (FDS) of both the instructed and the neighboring, non-instructed fingers during single finger flexion movements. In nine healthy subjects (age 22–29 years), instructed and non-instructed FDS finger tendon displacement of the index, middle and ring finger was measured using 2D ultrasound analyzed with speckle tracking software in two conditions: active flexion of all finger joints with all fingers free to move and active flexion while the non-instructed fingers were restricted. Our results of the free movement protocol showed an average tendon displacement of 27 mm for index finger flexion, 21 mm for middle finger flexion and 17 mm for ring finger flexion. Displacements of the non-instructed finger tendons (≈12 mm) were higher than expected based of the amount of non-instructed finger movement. In the restricted protocol, we found that, despite minimal joint movements, substantial non-instructed finger tendon displacement (≈9 mm) was still observed, which was interpreted as a result of tendon strain. When this strain component was subtracted from the tendon displacement of the non-instructed fingers during the free movement condition, the relationship between finger movement and tendon displacement of the instructed and non-instructed finger became comparable. Thus, when studying non-instructed finger tendon displacement it is important to take tendon strain into consideration.     

Na+, K(+)-ATPase inhibitory activity of fractionated urine during changes in dietary sodium intake in man

Na+, K(+)-ATPase inhibitory activity in urine fractionated by HPLC was quantified in 7 normotensive male subjects during changes in dietary sodium intake. Subjects were studied on free sodium intake for 2 days, on low sodium intake (2 g/day) for 3 days, on high sodium intake (22 g/day) for 4 days and subsequently on normal sodium intake (6 g/day) for 2 days. Na+, K(+)-ATPase inhibitory activity in fraction 10 eluted with 17% acetonitrile by reverse-phase HPLC was 12.3 +/- 5.2% (mean +/- S.D.) on free sodium intake, 8.7 +/- 9.8% on the 3rd day of low sodium intake, 61.2 +/- 6.6% on the 4th day of high sodium intake, and 20.5% +/- 0.7% on the 2nd day of the normal sodium intake. Changes in Na+, K(+)-ATPase inhibitory activity of fraction 10 were closely associated with those in urinary sodium excretion. These results suggest that an endogenous Na+, K(+)-ATPase inhibitor(s) which plays a physiological role in the control of sodium and water balance may exist in this particular fraction.     

Differential sensitivity of the kinesthetic and visual sensory system during complex motor activity in man]

Sportsmen of different specialities were examined by the A. V. Zavyalov method (1962) for differential sensitivity of their kinesthetic and visual analysers. It has been shown that the characteristics of differential sensitivity of the analysers are dissimilar in representatives of different kinds of sport. For example, pentathlon and basketball sportsmen exhibit in their kinesthetic analyser the greatest number of minimum increases of sensation, namely 30.2 and 21.4 respectively, while those not engaged in any sport, 15.0. The characteristics of intersensory optico-kinesthetic relationships has been established. Closest correlation has been recorded among pentathlon sportmen, volley-ballers and fencers. The dynamics of differential sensitivity of analysers is differently manifested, depending on the subjects' age.     

Effect of early sensory experience on the exploratory activity in adult animals

It was previously found that the exploratory activity of adult Wistar rats with their vibrissae cut in the period from 9 to 20 postnatal days was characterized by lower intragroup variability in comparison with control rats [3]. The present study has shown that the earlier limitation of species-specific afferentation (whisker trimming on postnatal days 2–9) does not induce such changes. We conclude that high plasticity of the brain during the early postnatal period provides better adaptation to the deficit of sensory information.     

Effects of finger markers on the kinematics of reaching movements in young children and adults

Kinematic studies to date have not considered in what ways surface markers may affect the performance of the analyzed motion. This neglect is particularly apparent in studies of prehensile movements involving surface markers attached to the fingers. In order to specify any such effects, a range of kinematic parameters derived from simple reach-to-grasp movements, both with and without finger markers, by 3-year old children and adults were analyzed. Finger markers affected both the spatial and temporal nature of the children's reaching performance as revealed by a more temporally segmented reaching path, an age-atypically straighter reaching path, and an increased time to establish a pincer grip. The reaching movements made by the adults were unaffected in terms of the kinematic parameters employed.     

Conditioning of slow electrocortical activity evoked by sensory stimulation and by a reflex movement in man]

Slow cerebral waves are recorded from 10 adults during an experiment consisting of the application of isolated or coupled sensorial stimulations, the weak sound occuring 880 msec prior to the strong light when coupled. Prior to coupling, the stimulations evoke on the vertex generally negative slow waves which would indicate an orientation reaction. After coupling, the responses to sound become constantly negative and are considered as waves described as "negative contingent variations". To the contrary, responses to light are inverted and become constantly positive. Such a phenomenon equally observed during experiments consisting of sound coupled to a reflex movement recalls the resolution of the negative contingent variation, the decision wave and the motor potentiel that accompanies the execution of voluntary movement, however here, it is produced during conditioning which does not require active motor participation by the subject. These results demonstrate that the simple coupling of two stimulations following the protocol developed by Pavlov provokes in man a complex collection of responses containing a motor component analogous to that which one observes in more elaborate experiments destined to prove the anticipation of the decision.     

Phase-dependence of breathing and finger tracking movements during normocapnia and hypercapnia

The coordination between breathing and other motor activities usually implies that the respiratory rhythm has become entrained by the rhythm of the simultaneous movement. Our hypothesis was that by increasing the respiratory drive, e.g. by hypercapnia, we would be able to reduce the subordination of breathing to other movements and, on the other hand, enhance effects of breathing on those movements. We investigated interactions between breathing and finger flexion movements in a visually controlled step-tracking procedure which allowed us to distinguish the mutual effects and to detect the dependence of these effects on the phase-relationship between breathing and movement. In contrast to our hypothesis, we found no large increase of the respiratory influences on finger movements during hypercapnia. A noteworthy difference to normocapnia was a shortening of the finger flexion time during the final stage of expiration which was associated with an increased frequency of coincidence between the end of flexion time and the transition from expiration to inspiration. On the other hand, the response of breathing to the finger movement increased when the tracking signal was presented at the beginning of inspiration. The results of the study disproved our hypothesis and demonstrated that, during hypercapnia, breathing can be even more susceptible to influences originating from motor control. Thus, they are in agreement with the findings of a previous study that the coordination between breathing and rhythmic limb movements becomes closer during hypercapnia.     

Voluntary finger movement in man: Cerebral potentials and theory

Three different brain potentials preceeding voluntary rapid finger flexion can be recorded from the skull surface by time reversed averaging. The early cortical activity preceding unilateral movement is bilateral and widespread (Bereitschaftspotential, BP). The same applies for the second potential (pre-motion positivity, PMP). Only the third potential (motor potential, MP) is unilateral and restricted to the contralateral motor cortex. In a total of 87 experiments with 39 subjects, the BP started on the average 750 ms (SD 360, SE 38.5) prior to rapid finger flexion. Its largest amplitude was found mid-parietally and averaged-5.3 V (SD 2.32, SE 0.4). Such amplitudes were found with averages of 800 and more movements per experiment. However, at the beginning of an experiment the BP is larger. Preceding finger movement, the BP was found bilaterally over the parietal and precentral cortex and over the midline. Over the frontal cortex, either no potential or positivity was recorded. In normal subjects, the BP always begins bilaterally and symmetrically. At parietal leads, it remains bilaterally-symmetrical. A slight contralateral preponderance begins about 400 ms prior to movement only over motor cortex, which becomes statistically significant at 150 ms. When comparing the parietal BP amplitude with the precentral amplitude on the ipsilateral side, where no superposition of the MP occurs, there is more negativity parietally than precentrally, although the parietal skull is about 11% thicker than the precentral. The BP is a negative shift of the cortical DC potential probably representing a preparatory process in the dendritic network of those cortical areas that are involved in the intended movement.The PMP is the next potential occurring 90–80 ms ( , SD 34.2, SE 2.95) prior to the first action potential in the contracting muscle (EMG). It was found in 85% of our subjects. The PMP has at its maximum, mid-parietally, a mean amplitude of +1.7 V (SD 1.6, SE 0.28). Like the BP, the PMP is bilateral and widespread in parietal and precentral leads of both sides and in the midline with a maximum at the anterior parietal region, despite the parietal skull being thicker than precentral. The short and the relatively constant onset time suggests that the PMP might reflect cortical activity (motor command) related to initiation of the tactually guided rapid finger movement under study.The MP starting 60–50 ms ( , SD 19.4, SE 3.1) prior to first activity in the agonist EMG is the last potential to occur and is the only unilateral potential: its localisation is limited to the hand area of the motor cortex contralateral to the moving finger. In bipolar recordings, contralateral versus ipsilateral precentral or contralateral precentral versus vertex, it appears as a sharp additional negativity. This additional negativity averaged-1.3 V (SD 0.64, SE 0.08). The MP reflects the motor cortical activity immediately preceding the movement.After movement onset, a complex potential is recorded, that is also seen with passive finger movement, largely representing a somatosensory (proprioceptive) evoked response. The possible meaning of the movement-related potentials is discussed in relation to a theory of central motor function.Supported by the Deutsche ForschungsgemeinschaftHabilitationsschrift of L.D. submitted to the Faculty of Clinical Medicine, University of Ulm (1974)