Multimodal responses of the nonspiking giant interneurons in the brain of the crayfish Procambarus clarkii

Three pairs of nonspiking giant interneurons (NGIs; G1, G2, and G3) of the crayfish brain responded with depolarizing and hyperpolarizing graded potentials to body tilt in roll to the ipsi- and contralateral sides in the dark. The higher and the larger the angle of body tilt, the larger was the amplitude of the geotactic responses. In ipsilaterally statocystectomized animals, all the NGIs responded with hyperpolarizing potentials only to the contralateral side-down tilt, whereas in contralaterally statocystectomized animals, they responded with depolarizing potentials only to the ipsilateral side-down tilt. In bilaterally statocystectomized animals, none of the NGIs responded to body tilt in the dark, but in the presence of an overhead light, they exhibited depolarizing and hyperpolarizing potentials in response to body tilt to the ipsi-and contralateral sides, respectively. All the NGIs responded with depolarizing and hyperpolarizing graded potentials to illumination of the contra- and ipsilateral eyes, respectively. The amplitude of these visual responses, however, varied in association with the amplitude of the geotactic response produced by body tilt. These results indicate that the NGIs integrate the sensory inputs from eyes and statocysts and that the interaction between sensory inputs from the left and right sensory organs with either the same modality or with different modalities enhance the directional sensitivity of NGIs as premotoneurons in the compensatory oculomotor system.     

Binocular visual integration in the crustacean nervous system

Although the behavioral repertoire of crustaceans is largely guided by visual information their visual nervous system has been little explored. In search for central mechanisms of visual integration, this study was aimed at identifying and characterizing brain neurons in the crab involved in binocular visual processing. The study was performed in the intact animal, by recording intracellularly the response to visual stimuli of neurons from one of the two optic lobes. Identified neurons recorded from the medulla (second optic neuropil), which include sustaining neurons, dimming neurons, depolarizing and hyperpolarizing tonic neurons and on-off neurons, all presented exclusively monocular (ipsilateral) responses. In contrast, all wide field movement detector neurons recorded from the lobula (third optic neuropil) responded to moving stimuli presented to the ipsilateral and to the contralateral eye. In these cells, the responses evoked by ipsilateral or contralateral stimulation were almost identical, as revealed by analysing the number and amplitude of the elicited postsynaptic potentials and spikes, and the ability to habituate upon repeated visual stimulation. The results demonstrate that in crustaceans important binocular processing takes place at the level of the lobula.     

Response characteristics of rat taste cells to potassium benzoate

The rat taste cells responded to K-benzoate solutions higher than the threshold concentrations (0.03-0.3 M) with a depolarizing receptor potential, but they responded to K-benzoate lower than the thresholds with a hyperpolarizing receptor potential. In either depolarizing or hyperpolarizing receptor potentials the rise time decreased with increasing amplitude, but the fall time increased with increasing amplitude. During generation of either depolarizing or hyperpolarizing receptor potentials the input resistance of taste cells decreased with increasing amplitude. Application of the mixtures of various concentrations of NaCl and 0.05 M K-benzoate resulted in a reduction of receptor potential amplitude, as compared with that evoked by application of NaCl alone. It is concluded that a depression of gustatory neural impulse frequency by low concentrations of K-benzoate is mainly due to the hyperpolarizing receptor potential of taste cells elicited by the K-benzoate solutions.     

Membrane resistance change of the frog taste cells in response to water and Nacl

The electrical properties of the frog taste cells during gustatory stimulations with distilled water and varying concentrations of NaCl were studied with intracellular microelectrodes. Under the Ringer adaptation of the tongue, two types of taste cells were distinguished by the gustatory stimuli. One type, termed NaCl-sensitive (NS) cells, responded to water with hyperpolarizations and responded to concentrated NaCl with depolarizations. In contrast, the other type of cells, termed water-sensitive (WS) cells, responded to water depolarizations and responded to concentrated NaCl with hyperpolarizations. The membrane resistance of both taste cell types increased during the hyperpolarizing receptor potentials and decreased during the depolarizing receptor potentials, Reversal potentials for the depolarizing and hyperpolarizing responses in each cell type were a few millivolts positive above the zero membrane potential. When the tongue was adapted with Na-free Ringer solution for 30 min, the amplitude of the depolarizing responses in the NS cells reduced to 50% of the control value under normal Ringer adaptation. On the basis of the present results, it is concluded (a) that the depolarizing responses of the NS and WS cells under the Ringer adaptation are produced by the permeability increase in some ions, mainly Na+ ions across the taste cell membranes, and (b) that the hyperpolarizing responses of both types of taste cells are produced by a decrease in the cell membrane permeability to some ions, probably Na+ ions, which is slightly enhanced during the Ringer adaptation.     

Ionic mechanisms of depolarizing and hyperpolarizing quinine receptor potentials in Paramecium caudatum

The ionic mechanisms of the depolarizing and the hyperpolarizing quinine receptor potentials in the ciliate Paramecium caudatum were examined by using a behavioral mutant strain. The depolarizing receptor potential was induced by stimulating the anterior end of the specimen, and the hyperpolarizing receptor potential by stimulating the posterior end. The amplitude of both the depolarizing and the hyperpolarizing receptor potentials increased linearly with logarithmic increase in quinine concentration applied. Threshold concentration for inducing the depolarizing receptor potential was lower than that for the hyperpolarizing one. The peak level of the depolarizing receptor potential shifted towards the depolarizing direction with increasing external Ca²⁺ concentration while that of the hyperpolarizing receptor potential shifted in the depolarizing direction with increasing external K⁺ concentration. Under voltage-clamp conditions, the specimen produced an inward current in response to anterior stimulation, and an outward current in response to posterior stimulation. Both the peak inward and the peak outward currents showed a linear relationship with membrane potential. Current-voltage relationships of the receptor currents indicated conductance increase during the application of quinine. The depolarizing quinine receptor potential appears to be produced by an activation of Ca²⁺ channels, and the hyperpolarizing quinine receptor potential by an activation of K⁺ channels. Accepted: 3 October 1997     

Depression of gustatory receptor potential in frog taste cell by parasympathetic nerve-induced slow hyperpolarizing potential

Parasympathetic nerve (PSN) innervates taste cells of the frog taste disk, and electrical stimulation of PSN elicited a slow hyperpolarizing potential (HP) in taste cells. Here we report that gustatory receptor potentials in frog taste cells are depressed by PSN-induced slow HPs. When PSN was stimulated at 30 Hz during generation of taste cell responses, the large amplitude of depolarizing receptor potential for 1 M NaCl and 1 mM acetic acid was depressed by approximately 40% by slow HPs, but the small amplitude of the depolarizing receptor potential for 10 mM quinine-HCl (Q-HCl) and 1 M sucrose was completely depressed by slow HPs and furthermore changed to the hyperpolarizing direction. The duration of the depolarizing receptor potentials depressed by slow HPs prolonged with increasing period of PSN stimulation. As tastant-induced depolarizing receptor potentials were increased, the amplitude of PSN-induced slow HPs inhibiting the receptor potentials gradually decreased. The mean reversal potentials of the slow HPs were approximately -1 mV under NaCl and acetic acid stimulations, but approximately -14 mV under Q-HCl and sucrose stimulations. This implies that when a slow HP was evoked on the same amplitude of depolarizing receptor potentials, the depression of the NaCl and acetic acid responses in taste cells was larger than that of Q-HCl and sucrose responses. It is concluded that slow HP-induced depression of gustatory depolarizing receptor potentials derives from the interaction between gustatory receptor current and slow hyperpolarizing current in frog taste cells and that the interaction is stronger for NaCl and acetic acid stimulations than for Q-HCl and sucrose stimulations.     

Motion analysis of leg joints associated with escape turns of the cockroach,Periplaneta americana

Considerable information is now available on the neural organization of the escape system of the American cockroach. To relate these data to the behavior, we need detailed information on the movements made at the principle leg joints that produce the turn. We used motion analysis of high speed video records to acquire such information. Records from both free ranging and tethered animals were analyzed. 1. We analyzed individual joint movements using a tethered preparation. Stimuli from 4 different angles around the animal were used. For all wind angles, the femur-tibia (FT) joint on the mesothoracic leg that is ipsilateral to the wind source extended while the contralateral mesothoracic FT joint flexed. This moved both of these legs laterally toward the wind source. In freely moving animals the FT movements provide forces that turn the animal away from the wind source. 2. The ipsilateral mesothoracic coxa-femur (CF) joint extended for all wind angles. The contralateral mesothoracic CF joint extended in response to most winds from the rear, but switched to flexion in response to wind from the side and front. As a result of these joint movements, rear wind resulted in rearward movements of the contralateral mesothoracic leg, while side and front wind resulted in more forward movements of that leg. 3. The CF and FT joints for both ipsilateral and contralateral metathoracic legs extended to wind from the rear and switched to flexion as the wind was placed at more anterior positions around the animal. In freely moving animals, extension of these joints would push the animal forward. Flexion would pull the animal backward. 4. Several of the joints showed correlations between rate of movement and initial joint angle. That is, joints that were already flexed at the onset of stimulation tended to move at a faster rate to a final position than joints that started at a more extended position. 5. Metathoracic FT and CF joints showed a high degree of positive correlation during the escape movements. Indeed, many curves showing movement of metathoracic FT and CF joints with time were virtually identical.     

A push-pull set of elastic strand stretch receptor neurons for the swimmeret in an isopod Bathynomus doederleini

There coexist two types of neuronal terminal processes attaching to elastic strands at the socket of the swimmeret in Bathynomus doederleini. One of the processes, stretch receptor I is derived from the 1st nerve root of the abdominal ganglion. The other, stretch receptor II is derived from the 2nd nerve root of the ganglion. Both axons of stretch receptors are very thick (30-60 micro m) at sites before the terminal arborization. Cell bodies of the stretch receptors are located in the ganglion of their own segments. The neuronal cell body of the stretch receptor I is located at the anterior half of the hemiganglion ipsilateral to the periphery, and the neuronal cell body of the stretch receptor II at the posterior half of the hemiganglion contralateral to the periphery. Their signaling modalities in response to swimmeret movements were analyzed from intracellular recordings from the cell bodies. Stretch receptor I produced a sustained hyperpolarizing potential in response to protraction of the swimmeret. Stretch receptor II produced a sustained depolarizing potential in response to the protraction, and moreover, generated spike potentials on the rising phase of the depolarizing potential according to its height and steepness. Both the stretch receptors are a push-pull set of elastic strand stretch receptors for the angular position and velocity of swimmeret movements.     

The steady-state distribution of gating charge in crayfish giant axons.

Progressive shifts of holding potential (Vh) in crayfish giant axons, from -140 to -70 mV, reduce gating currents seen in depolarizing steps (to 0 mV test potential) while proportionately increasing gating currents in hyperpolarizing steps (to -240 mV). The resulting sigmoid equilibrium charge distribution (Q-Vh curve) shows an effective valence of 1.9e and a midpoint of -100 mV. By contrast, Q-V curves obtained using hyperpolarizing and/or depolarizing steps from a single holding potential, change their "shape" depending on the chosen holding potential. For holding potentials at the negative end of the Q-Vh distribution (e.g., -140 mV), negligible charge moves in hyperpolarizing pulses and the Q-V curve can be characterized entirely from depolarizing voltage steps. The slope of the resulting simple sigmoid Q-V curve also indicates an effective valence of 1.9e. When the axon is held at less negative potentials significant charge moves in hyperpolarizing voltage steps. The component of the Q-V curve collected using hyperpolarizing pulses shows a significantly reduced slope (approximately 0.75e) by comparison with the 1.9e slope found using depolarizing pulses or from the Q-Vh curve. As holding potential is shifted in the depolarizing direction along the Q-Vh curve, an increasing fraction of total charge movement must be assessed in hyperpolarizing voltage steps. Thus charge moving in the low slope component of the Q-V curve increases as holding potential is depolarized, while charge moving with high apparent valence decreases proportionately. Additional results, together with simulations based on a simple kinetic model, suggest that the reduced apparent valence of the low slope component of the Q-V curve results from gating charge immobilization occurring at holding potential. Immobilization selectively retards that fraction of total charge moving in hyperpolarizing pulses. Misleading conclusions, as to the number and valence of the gating particles, may therefore be derived from Q-V curves obtained by other than depolarizing pulses from negative saturated holding potentials.     

Unit activity in the superior colliculus of the cat following passive eye movements.

Unit response in the superior colliculus and underlying structures has been examined in the choralose-anaesthetized cat following passive movement of an occluded eye. One group of units was sensitive to small saccadic movements, responded regardless of the initial postion of the eye, and in most instances responded to movements in opposit directions. A second numerically smaller group also responded when they eye was moved at saccadic velocity but only when the eye passed a fixed point. Such units with fixed positional thresholds were found following movements in both nasal and temporal directions as well as to both upward and downward movement. Both types of unit response were found after transection of the optic nerve and were also recorded when individual extraocular muscles were subjected to controlled stretch. It is assumed that most unit activity seen after passive movement of the occluded eye is due to activity in extraocular muscle receptors. In the deep layers of the superior colliculus responses to small eye movements were found to be due to the activation of very low threshold receptors sensitive to vibration in the facial area.     

Active sensing in a freely walking spider: look where to go

The Central American hunting spider Cupiennius salei, like most other spiders, has eight eyes, one pair of principal eyes and three pairs of secondary eyes. The principal eyes and one pair of the secondary eyes have almost completely overlapping visual fields, and presumably differ in function. The retinae of the principal eyes can be moved independently by two pairs of eye muscles each, whereas the secondary eyes do not have such eye muscles. The behavioural relevance of retinal movements of freely moving spiders was investigated by a novel dual-channel telemetric registration of the eye muscle activities. Walking spiders shifted the ipsilateral retina with respect to the walking direction before, during and after a turning movement. The change in the direction of vision in the ipsilateral anterior median eye was highly correlated with the walking direction, regardless of the actual light conditions. The contralateral retina remained in its resting position. This indicates that Cupiennius salei shifts it visual field in the walking direction not only during but sometimes previous to an intended turn, and therefore “peers” actively into the direction it wants to turn.     

Chemosensitivity of single smooth muscle cells to acetylcholine, noradrenaline, and histamine in vitro

Electrical responses to acetylcholine, noradrenaline, and histamine were recorded from solitary smooth muscle cells. Iontophoresis of each transmitter elicited three fast responses: a hyperpolarization, a depolarization, or a biphasic hyperpolarization-depolarization. Each transmitter activated a specific receptor since responses were specifically blocked by antagonists, two transmitters elicited different responses in solitary cells, and desensitization of response to one transmitter did not cause desensitization of responses to other transmitters. Responses were due to increased ion conductances since input resistance decreased during responses and reversal potentials were measured for depolarizing responses (-5 mV) and hyperpolarizing responses (-60 mV). Regional differences in transmitter sensitivity were mapped on solitary cells. Biphasic responses were due to simultaneous activation of receptors mediating hyperpolarizing responses and receptors mediating depolarizing responses which were segregated in the cell membrane. Noradrenaline enhanced action potential amplitude by regulation of voltage-dependent ion conductances. Finally, noradrenaline and histamine elicited periodic hyperpolarizing potentials, which may be due to increased intracellular Ca++.     

Coordination of wing motion and walking suggests common control of zigzag motor program in a male silkworm moth

The male silkworm moth, Bombyx mori, exhibits a zigzagging pattern as it walks upwind to pheromones. This species usually does not fly, but obvious wing-beating accompanies the pheromone-mediated walking. Males supported by a `sled', after having their legs removed, also moved upwind in a pheromone plume along zigzagging tracks, indicating that wing-generated thrust and torque result in locomotory paths similar to those observed from walking moths. Using a high-speed video system we investigated the correlation between the wing movements and zigzag walking. The wing ipsilateral to the direction of the turn showed a greater degree of retraction with respect to the contralateral wing. The timing of the wing retraction pattern was synchronized with changes of direction in the walking track. Coordination of wing movements and walking pattern was not dependent on visual feedback or sensory feedback generated from neck movements associated with turning. The results presented here, taken together with our previous studies of descending interneurons suggest that the coordination of wing movements with the walking pattern may result from the activity of a set of identified interneurons descending from the brain to the thoracic ganglia and/or may be coordinated by coupling of oscillating circuits for walking and wing beating. Accepted: 15 May 1997     

Load changes in limbs during orienting in non-restrained cats

We simultaneously investigated eye and head movements and postural adjustment during orienting by measuring load force exerted by four limbs in cats. When light is moved from the fixation point to the target position, the head first begins moving towards the target position, and the eye moves in the opposite direction due to the vestibulo-ocular reflex (VOR). Later, the eye moves quickly in the target direction by saccade, synchronous with the remaining rapid head orientation movement. Head movement is classified as either 'head rotation' or 'head translation'. During head rotation, the load force in ipsilateral limb to the target position decreased, and that in the contralateral limb increased. During head translation, on the contrary, load force in the ipsilateral limb increased and that in the contralateral limb decreased. This phenomenon was observed in fore- and hindlimbs. The latencies of head movement are very similar with those of the load force change in many trials, and in case in which the head movement has short latency, the amount of load force change is larger. In contrast, when head movement has long latency, the amount of load force change is smaller. In a previous study, we recorded two types of neurons from ponto-medullary reticular formation. The firing of these neurons was related with head movement. The cervical reticulospinal neuron (C-RSN) in ponto-medullary reticular formation got off collateral to both neck and forelimb motoneurons. These types were named phasic neuron (PN) and phasic sustained neuron (PSN). We discuss the relation between load changes and the two types of neurons and postural adjustment during orienting.     

The Intrinsic Electrophysiological Characteristics of Fly Lobula Plate Tangential Cells: III. Visual Response Properties

In this last paper in a series (Borst and Haag, 1996; Haag et al., 1997) about the lobula plate tangential cells of the fly visual system (CH, HS, and VS cells), the visual response properties were examined using intracellular recordings and computer simulations. In response to visual motion stimuli, all cells responded mainly by a graded shift of their axonal membrane potential. While ipsilateral motion resulted in a graded membrane potential shift, contralateral motion led to distinct EPSPs. For HS cells, simultaneous extracellular recorded action potentials of a spiking interneuron, presumably the H2 cell, corresponded to the EPSPs in the HS cell in a one-to-one fashion. When HS cells were hyperpolarized during ipsilateral motion, they mainly produced action potentials, but when they were hyperpolarized during contralateral motion only a slight increase of EPSP amplitude, could be observed. Intracellular application of the sodium channel blocker QX 314 abolished action potentials of HS cells while having little effect on the graded membrane response to ipsilateral motion. HS and CH cells were also studied with respect to their spatial integration properties. For both cell types, their graded membrane response was found to increase less than linearly with the size of the ipsilateral motion pattern. However, while for HS cells various amounts of hyperpolarizing current injected during motion stimulation led to different saturation levels, this was not the case for CH cells. In response to a sinusoidal velocity modulation, CH cells followed pattern motion only up to 10 Hz modulation frequency, but HS cells still revealed significant membrane depolarizations up to about 40 Hz.In the computer simulations, the compartmental models of tangential cells, as derived in the previous papers, were linked to an array of local motion detectors. The model cells revealed the same basic response features as their natural counterparts. They showed a response saturation as a function of stimulus size. In CH-models, however, the saturation was less pronounced than in real CH-cells, indicating spatially nonuniform membrane resistances with higher values in the dendrite. As in the experiments, HS models responded to high-frequency velocity modulation with a higher amplitude than did CH models.     

Photoreceptor Potentials of Opposite Polarity in the Eye of the Scallop, Pecten irradians

Intracellular recordings were obtained from single visual cells of the scallop, Pecten irradians. Two types of units are found. One type gives a graded, depolarizing response to light and the other a graded, hyperpolarizing response. The depolarizing cells are 2–3 log units more sensitive to light and have a longer latency than the hyperpolarizing type. At high light intensities the depolarizing cells are inactivated while the hyperpolarizing cells maintain their responses. When action potentials are seen they occur during illumination in depolarizing cells ("on" response) and after illumination in hyperpolarizing cells ("off" response). The evidence suggests that the depolarizing responses are from the microvilli-brearing proximal cells, and the hyperpolarizing responses from the ciliary-type distal cells of the retina, and that both responses are directly produced by light.     

Righting kinematics in beetles (Insecta: Coleoptera)

Twenty modes of stereotyped righting motions were observed in 116 representative species of coleoptera. Methods included cine and stereocine recording with further frame by frame analysis, stereogrammetry, inverse kinematic reconstruction of joint angles, stroboscopic photography, recording of electromyograms, 3D measurements of the articulations, etc. The basic mode consists of a search phase, ending up with grasping the substrate, and a righting, overturning phase. Leg coordination within the search cycle differs from the walking cycle with respect to phasing of certain muscle groups. Search movements of all legs appear chaotic, but the tendency to move in antiphase is still present in adjacent ipsilateral and contralateral leg pairs. The system of leg coordination might be split: legs of one side might search, while contralateral legs walk, or fore and middle legs walk while hind legs search. Elaborated types of righting include somersaults with the aid of contralateral or diagonal legs, pitch on elytra, jumps with previous energy storage with the aid of unbending between thoracic segments (well-known for Elateridae), or quick folding of elytra (originally described in Histeridae). Righting in beetles is compared with righting modes known in locusts and cockroaches. Search in a righting beetle is directed dorsad, while a walking insect searches for the ground downwards. Main righting modes were schematized for possible application to robotics.     

The contralateral coordination of walking legs in the crayfish Astacus leptodactylus

The coupling mechanisms which coordinate the movement of ipsilateral walking legs in the crayfish have been described in earlier investigations. Concerning the coupling between contralateral legs it was only known that these influences are weaker than those acting between ipsilateral legs. The nature of these coupling mechanisms between contralateral legs of the crayfish are investigated here by running left and right legs on separate walking belts at different speeds. The results show that coordination is performed by a phase-dependent shift of the anterior extreme position of the influenced leg. This backward shift leads to a shortening of both the return stroke and the following power stroke. As the coupling influence is only weak, several steps might be necessary to retain normal coordination after a disturbance. This corresponds to v. Holst's relative coordination. The influences act in both directions, from left to right and vice versa. However, one side may be more or less dominant. A gradient was found in the way that anterior leg pairs show less strong coordination than posterior legs. In some cases the coupling between diagonally neighbouring legs was found to be stronger than between contralateral legs of the same segment. The interpretation of this result is still open.     

On the invariance of visual stimulus efficacy with respect to variable spatial positions

Summary In the fly,Calliphora erythrocephala, visual stimuli presented in an asymmetrical position with respect to the fly elicit roll or tilt movements of the head by which its dorsal part is moved towards the light areas of the surroundings (Figs. 4–7). The influence of passive body roll and tilt (gravitational stimulus) on the amplitude of these active head movements was investigated for two types of visual stimuli: (1) a dark hollow hemisphere presented in different parts of the fly's visual field, and (2) a moving striped pattern stimulating the lateral parts of one eye only.The response characteristics of the flies in the bimodal situation in which the gravitational stimulus was paired with stimulation by the dark hollow hemisphere can be completely described by the addition of the response characteristics for both unimodal situations, i.e. by the gravity-induced and visually induced characteristics (Figs. 8, 9). Therefore, the stimulus efficacy of the dark hollow hemisphere is independent of (=invariant with respect to) the flies' spatial position. The advantage of this type of interaction between gravity and visual stimulation for the control of body posture near the horizontal is discussed.In contrast, the efficacy of moving patterns depends on (=non-invariant with respect to) the spatial position of the walking fly. Regressive pattern movements exhibit their stronger efficacy with respect to progressive ones only when the gravity receptor system of the legs is stimulated. The stronger efficacy of downward vs upward movements can only be demonstrated when the flies are walking horizontally, independently of whether the leg gravity receptor system is stimulated by gravity or not (Fig. 10).The results are discussed with respect (1) to the invariance and non-invariance of the efficacy of visual stimuli with respect to the direction of the field of gravity, (2) to the formation of reference lines by the gravitational field which are used by the walking fly to determine the orientation of visual patterns, and (3) to the possible location of the underlying convergence between gravitationally and visually evoked excitation. As all types of head responses occur only in walking flies, we also discussed the possible influences of some physiological processes like arousal, proprioceptive feedback during walking and various peripheral sensory inputs on the performance of behavioural responses in the fly (Fig. 11).     

Readiness potentials recorded from the scalp and depth leads.

Readiness potentials on voluntary hand movements were recorded from the scalp (C3, C4), premotor cortex, subcortical white matter and VL nucleus of the thalamus. Subjects were healthy right-handed men and patients with involuntary movement disorders. We obtained a slow negative shift of brain electrical potentials from the scalp and cortex preceding voluntary hand movements. The mean time interval between the onset of the readiness potential and the onset of motor activity (mean T) was 0.8 sec on right hand movements and 1.0 sec on left hand movements in healthy men. In cases with parkinsonism, the mean T value was 1.4 sec in patients with akinesia, 1.1 sec in those without akinesia. The amplitude of readiness potentials was higher in the scalp contralateral to the hand movement. The readiness potentials recorded from the VL nucleus and white matter were reversed in polarity from those of scalp and cortex. Simultaneous recordings from cortex and VL nucleus showed early onset of readiness potentials from the cortex by approximately 0.1 sec compared with the VL nucleus.