Brcrin Rrscurch Bulkfin,
Vol. 4, pp. 249-257. Printed
in
the U.S.A
Monkey Pyramidal Tract Neurons and Changes of Movement Parameters in Visual Tracking IKUMA
HAMADA
AND KISOU
KUBOTA
~ep~~rtrnent of ~e~ro~hys~~lo~y, Primate Reseureh ~~~st~tute,Kyoto ~ni~}er.~it~ Inuyarnu City, Aichi, 484. Japan (Received
29 September
1978)
HAMADA,
I. AND K. KUBOTA. Modey pwcrmidd fruct IIPU~O~I~S umi chmges of‘ mwemetit pcrrwnetet’.v in ~isurrl 4(Z) 249-257, 1979.-During a single-step visual tracking task of monkeys, parametric changes of the wrist extension-flexion movement and related discharge rate changes of pyramidal tract neurons (PTNs) of hand-arm motor area were studied. The task consisted of preparatory, precontraction, contraction and target periods. If the displacement amplitude was changed from narrow (l&20”) to moderate (40”) range, peak velocity, peak acceleration and contraction period increased linearly but precontraction period decreased slightly. In 61 movement-related PTNs, no linear relationships were found between PTN discharge rate during precontraction or contraction period and displacement amplitude, velocity, acceleration, precontraction period or contraction period. In less than 2(yTcof PTNs, however, correlations between mN discharge rate during precontraction period and velocity or acceleration were found in the moderate range task. It occurred less frequently in narrow range task. It is said in a visual tracking task that PTN activity is not dependent upon factors related to the task parameters. such as velocity, acceleration. Possible related factors were discussed.
f~[~~~i//,s. BRAIN RES. BULL.
Monkey
PTNs
Single step visual tracking
ICMS
IT HAS been observed that the pyramidal tract neurons (PTNs) of the hand-arm motor area of the monkey are activated prior to the onset of voluntary movement and that their rate of discharge is linearly related to the load applied to the contracting muscles [4]. It was inferred from this that those PTNs were functionally related to the voluntary movement, in such a fashion as to control the force exerted during the movement rather than the position of the moving part. This notion was further supported by findings in monkeys that the PTNs and non-PTNs of the finger motor area showed a rate change linearly related to the force produced during isometric contractions of finger muscles [9,19]. However, in a task requiring a stop before or after the movement only a weak relation was observed between discharge rates of unidentified motor cortex neurons and force [17]. Recently, PTN activity was shown to be related to a psychological factor referred to as instructing the direction of the coming movement or anticipation 1201. During push-pull arm movement in which a visual cue was presented prior to the GO signal, the visual cue itself induced PTN activity before onset of an instructed movement. In our laboratory, using a visual tracking task, involving wrist movement, PTN discharges have been observed in a period prior to GO signal for the movement at rates which correlate negatively with reaction time (precontraction period in the term used in [12]). This preparatory activity was ascribed to a subjective effect of the monkey to produce a quick voluntary action 18,121. It now thus appeared that the PTN activity is not only related directly to the motor output parameters such as force, but also, indirectly, to yet unclarified pre-motor activity of the subject such as expectation, preparation, will, ef-
Copyright ‘G 1979 ANKHO
Movement parameters
fort. Because of presence of these two factors in the PTN activity, it is expected that the preparatory and precontraction PTN activity will not show simple relations to the movement parameters themselves. However, correlation studies seemed necessary in order to determine the presence or absence of such relationship. At present extensive studies on this topic have not yet been attempted and brief reports are available in which some correlations with force (F), dF/dt, velocity or acceleration are shown in both PTNs and non-PTNs [10,17]. It will be shown in a single-step visual tracking movement performed with relatively weak torque force (30 G-cm) that the discharge rates during preparatory and precontraction periods are only occasionally correlated to the velocity or acceleration.
METHOD
Experimental procedures and data analyses are exactly the same as described in our previous study 17,121. Four rhesus monkeys performed a single-step visual tracking task at the wrist. Three of them, used for PTN recordings, are exactly the same monkeys used in previous study on the post-arcuate premotor neurons [12]. PTN samples are from monkeys utilized in a previous study (121. In the fourth monkey only parametric relations of the tracking movement were studied without head restraint. In monkeys for PTN recordings, relations between displacement amplitude and movement parameters were only studied while the PTN activities were recorded. Therefore, the fourth monkey was trained to collect sufficient data on above relations.
International Inc.-0361-9230/79/020249-09$01.40/O
During the task the monkey, sitting in the primate chair, rotated the vertical handle with his left hand over a range of about 110 degrees. Rotatory radius was 25-35 mm and was comparable to the distance from the joint axis at the wrist to the gripped handle. The animal faced a panel on which 12 light emitting diodes (LEDs; GL-50 RG, Sharp Co.) were arranged 2 cm apart in two horizontal levels. Each of LEDs of the lower level indicated an angular displacement zone of the rotating handle and each of 4 LEDs on the upper level indicated a target zone. The total displacement zone covered 64”, and was divided into eight positions (8”), each indicated by a light numbered from left to right, as pl to p8. A linear potentiometer (Copal, Type J45S, 50 K0; torque, 6 g-cm) coupled to the handle provided a mean for lighting a single LED when the handle was in the appropriate position. Maximal torque force produced transiently in order to rotate the handle was 30 g-cm, measured by a torque meter (JKT-200, Jido-keisoku, Saitama, Japan). Static force was practically zero. Since the total weight of the handle with its arm was 40 g, a force against inertial load was small. Also elastic or resistive load against the movement was negligibly small. Arm and shoulder movements were restrained the monkey to reach a handle through a Plexiglas tube (6 cm dia. x 10 cm length). The task was controlled by a minicomputer (PDP-11110) and its trial sequence was as follows: (a) The animal moved the handle into pl (or p8) zone, and a green light was activated. The handle was held in this start zone for a fixed preparatory (PREP) period lasting 0.5, 1.0 or 2.0 sec. (b) At the end of PREP period, pl (or p8) was illuminated by a red LED and a preselected target light was turned on simultaneously (GO signal). (c) From GO signal onset to the displacement onset was the precontraction (PRECON) period. And then the handle was moved during the contraction (CONTR) period to the target zone and the appropriate LEDs were lighted in sequence. The handle was held in the target zone for a target (TARG) period of 0.5, 1.O or 2.0 set before juice reward delivery. Each trial was coded by target zone number (e.g. T5), direction of movement (e.g. E or F). The target zone amplitudes were occasionally changed during experiment, reducing the each zone amplitude to ‘/z or ‘ir of standard amplitude (8”). Therefore, task mode is represented as e.g. TSFr12 (flexion task to the target p5 of which zone amplitude was 4”, therefore, central movable range was 32”). An over-movement of the handle out of the target zone resulted in signals to adjacent lights and adjusting of the position was necessary (over-shoot trials). This occurred in 5-l% of trials. All neurons to be described are recorded by glass-coated platinum microelectrodes and are PTNs identified by stimulating right pyramidal tract at the ponto-medullary junction via implanted bipolar electrodes. PTNs were recorded from the hand-arm motor area, as defined by Woolsey er ~1. [21] (cf. Fig. 1 of [12]). While activities of more than half of sampled PTNs were recorded, EMGs were recorded simultaneously via a pair of skin electrodes (Beckman) or intramuscularly inserted urethane-coated copper wires (60 pm dia.). Examined muscles were forearm flexors (N = 12), forearm extensors (26), biceps (4), triceps (5), deltoid (3), supra- and infra-spinatus muscles (5). As soon as a PTN was located, the experimental trials were initiated randomly shifting between flexion (F) and extension (E) movements using a 40” range (T6Fl or T3El). A trial series included between 15 and 40 trials. The experimental conditions were then altered by eliminating the PREP
period and/or the TARG period. Trials were then conducted with arbitrary variations in target positions and zone amplitudes and in durations of PREP and TARG periods (0.5, 1.0 and 2.0 set). At the end of each recording session from a single neuron, intracortical microstimulation ICMS; 330 Hz, 0.1 ms pulse width, 20 pulses: (1) was used to locate muscles activated from this focus and d
Vol. 4, pp. 249-257. Printed
in
the U.S.A
Monkey Pyramidal Tract Neurons and Changes of Movement Parameters in Visual Tracking IKUMA
HAMADA
AND KISOU
KUBOTA
~ep~~rtrnent of ~e~ro~hys~~lo~y, Primate Reseureh ~~~st~tute,Kyoto ~ni~}er.~it~ Inuyarnu City, Aichi, 484. Japan (Received
29 September
1978)
HAMADA,
I. AND K. KUBOTA. Modey pwcrmidd fruct IIPU~O~I~S umi chmges of‘ mwemetit pcrrwnetet’.v in ~isurrl 4(Z) 249-257, 1979.-During a single-step visual tracking task of monkeys, parametric changes of the wrist extension-flexion movement and related discharge rate changes of pyramidal tract neurons (PTNs) of hand-arm motor area were studied. The task consisted of preparatory, precontraction, contraction and target periods. If the displacement amplitude was changed from narrow (l&20”) to moderate (40”) range, peak velocity, peak acceleration and contraction period increased linearly but precontraction period decreased slightly. In 61 movement-related PTNs, no linear relationships were found between PTN discharge rate during precontraction or contraction period and displacement amplitude, velocity, acceleration, precontraction period or contraction period. In less than 2(yTcof PTNs, however, correlations between mN discharge rate during precontraction period and velocity or acceleration were found in the moderate range task. It occurred less frequently in narrow range task. It is said in a visual tracking task that PTN activity is not dependent upon factors related to the task parameters. such as velocity, acceleration. Possible related factors were discussed.
f~[~~~i//,s. BRAIN RES. BULL.
Monkey
PTNs
Single step visual tracking
ICMS
IT HAS been observed that the pyramidal tract neurons (PTNs) of the hand-arm motor area of the monkey are activated prior to the onset of voluntary movement and that their rate of discharge is linearly related to the load applied to the contracting muscles [4]. It was inferred from this that those PTNs were functionally related to the voluntary movement, in such a fashion as to control the force exerted during the movement rather than the position of the moving part. This notion was further supported by findings in monkeys that the PTNs and non-PTNs of the finger motor area showed a rate change linearly related to the force produced during isometric contractions of finger muscles [9,19]. However, in a task requiring a stop before or after the movement only a weak relation was observed between discharge rates of unidentified motor cortex neurons and force [17]. Recently, PTN activity was shown to be related to a psychological factor referred to as instructing the direction of the coming movement or anticipation 1201. During push-pull arm movement in which a visual cue was presented prior to the GO signal, the visual cue itself induced PTN activity before onset of an instructed movement. In our laboratory, using a visual tracking task, involving wrist movement, PTN discharges have been observed in a period prior to GO signal for the movement at rates which correlate negatively with reaction time (precontraction period in the term used in [12]). This preparatory activity was ascribed to a subjective effect of the monkey to produce a quick voluntary action 18,121. It now thus appeared that the PTN activity is not only related directly to the motor output parameters such as force, but also, indirectly, to yet unclarified pre-motor activity of the subject such as expectation, preparation, will, ef-
Copyright ‘G 1979 ANKHO
Movement parameters
fort. Because of presence of these two factors in the PTN activity, it is expected that the preparatory and precontraction PTN activity will not show simple relations to the movement parameters themselves. However, correlation studies seemed necessary in order to determine the presence or absence of such relationship. At present extensive studies on this topic have not yet been attempted and brief reports are available in which some correlations with force (F), dF/dt, velocity or acceleration are shown in both PTNs and non-PTNs [10,17]. It will be shown in a single-step visual tracking movement performed with relatively weak torque force (30 G-cm) that the discharge rates during preparatory and precontraction periods are only occasionally correlated to the velocity or acceleration.
METHOD
Experimental procedures and data analyses are exactly the same as described in our previous study 17,121. Four rhesus monkeys performed a single-step visual tracking task at the wrist. Three of them, used for PTN recordings, are exactly the same monkeys used in previous study on the post-arcuate premotor neurons [12]. PTN samples are from monkeys utilized in a previous study (121. In the fourth monkey only parametric relations of the tracking movement were studied without head restraint. In monkeys for PTN recordings, relations between displacement amplitude and movement parameters were only studied while the PTN activities were recorded. Therefore, the fourth monkey was trained to collect sufficient data on above relations.
International Inc.-0361-9230/79/020249-09$01.40/O
During the task the monkey, sitting in the primate chair, rotated the vertical handle with his left hand over a range of about 110 degrees. Rotatory radius was 25-35 mm and was comparable to the distance from the joint axis at the wrist to the gripped handle. The animal faced a panel on which 12 light emitting diodes (LEDs; GL-50 RG, Sharp Co.) were arranged 2 cm apart in two horizontal levels. Each of LEDs of the lower level indicated an angular displacement zone of the rotating handle and each of 4 LEDs on the upper level indicated a target zone. The total displacement zone covered 64”, and was divided into eight positions (8”), each indicated by a light numbered from left to right, as pl to p8. A linear potentiometer (Copal, Type J45S, 50 K0; torque, 6 g-cm) coupled to the handle provided a mean for lighting a single LED when the handle was in the appropriate position. Maximal torque force produced transiently in order to rotate the handle was 30 g-cm, measured by a torque meter (JKT-200, Jido-keisoku, Saitama, Japan). Static force was practically zero. Since the total weight of the handle with its arm was 40 g, a force against inertial load was small. Also elastic or resistive load against the movement was negligibly small. Arm and shoulder movements were restrained the monkey to reach a handle through a Plexiglas tube (6 cm dia. x 10 cm length). The task was controlled by a minicomputer (PDP-11110) and its trial sequence was as follows: (a) The animal moved the handle into pl (or p8) zone, and a green light was activated. The handle was held in this start zone for a fixed preparatory (PREP) period lasting 0.5, 1.0 or 2.0 sec. (b) At the end of PREP period, pl (or p8) was illuminated by a red LED and a preselected target light was turned on simultaneously (GO signal). (c) From GO signal onset to the displacement onset was the precontraction (PRECON) period. And then the handle was moved during the contraction (CONTR) period to the target zone and the appropriate LEDs were lighted in sequence. The handle was held in the target zone for a target (TARG) period of 0.5, 1.O or 2.0 set before juice reward delivery. Each trial was coded by target zone number (e.g. T5), direction of movement (e.g. E or F). The target zone amplitudes were occasionally changed during experiment, reducing the each zone amplitude to ‘/z or ‘ir of standard amplitude (8”). Therefore, task mode is represented as e.g. TSFr12 (flexion task to the target p5 of which zone amplitude was 4”, therefore, central movable range was 32”). An over-movement of the handle out of the target zone resulted in signals to adjacent lights and adjusting of the position was necessary (over-shoot trials). This occurred in 5-l% of trials. All neurons to be described are recorded by glass-coated platinum microelectrodes and are PTNs identified by stimulating right pyramidal tract at the ponto-medullary junction via implanted bipolar electrodes. PTNs were recorded from the hand-arm motor area, as defined by Woolsey er ~1. [21] (cf. Fig. 1 of [12]). While activities of more than half of sampled PTNs were recorded, EMGs were recorded simultaneously via a pair of skin electrodes (Beckman) or intramuscularly inserted urethane-coated copper wires (60 pm dia.). Examined muscles were forearm flexors (N = 12), forearm extensors (26), biceps (4), triceps (5), deltoid (3), supra- and infra-spinatus muscles (5). As soon as a PTN was located, the experimental trials were initiated randomly shifting between flexion (F) and extension (E) movements using a 40” range (T6Fl or T3El). A trial series included between 15 and 40 trials. The experimental conditions were then altered by eliminating the PREP
period and/or the TARG period. Trials were then conducted with arbitrary variations in target positions and zone amplitudes and in durations of PREP and TARG periods (0.5, 1.0 and 2.0 set). At the end of each recording session from a single neuron, intracortical microstimulation ICMS; 330 Hz, 0.1 ms pulse width, 20 pulses: (1) was used to locate muscles activated from this focus and d
