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Alterations in vector components of the velocity of the forepaw during switching of target-reaching in the cat
253
Neuroscience Research, 5 (1988) 253-257 Elsevier Scientific Publishers Ireland Ltd. NSR 00197
Short Communications
Alterations in vector components of the velocity of the forepaw during switching of target-reaching in the cat L.-G. Pettersson Department of Physiology, University of G~teborg, G~teborg (Sweden) (Received 27 April 1987; Accepted 26 September 1987)
Key words: Cat; Switching of target-reaching; Horizontal velocity component; Alteration
SUMMARY Switching of target-reaching in cats following a change in the location of the target is described kinematically as alterations in horizontal orthogonal velocity components. Alterations observed during real movement deviations are theoretically explained. Such deviations can be initiated by altering a single velocity component in isolation.
Cats are able to correct ongoing visually guided target-reaching with short response latencies following a change in the location of the target ~. To provide a kinematic description of such movement corrections, their velocity alterations in relevant motion directions have been studied and related to theoretical possibilities for modifying movement trajectories. The observations were made on 3 cats used by Alstermark et al.2 in a behavioural task described previously ~. In short: the cats were standing on platforms in front of two horizontal tubes with food (left = L, right = R tube) covered by locked opaque trap doors. The tubes were at the same horizontal level and the intercentre distance was 6 cm. Each tube could be illuminated and simultaneously unlocked during a predetermined time. The cats were trained to perform target-reaching to the illuminated tube and retrieve the food. Single trials, i.e. one tube illuminated during the entire movement (single L, single R trials), and switching trials, i.e. illumination switched to the other tube 50 ms after the onset of the movement (L ---,R, R ---,L trials), were given in pseudorandom series. During switching trials the animal had to modify its ongoing Correspondence: L.-G. Pettersson, Department of Physiology, University of GOteborg, P.O. Box 33031, S-400 33 GOteborg, Sweden. 0168-0102/88/$03.50 © 1988 Elsevier Scientific Publishers Ireland Ltd.
254
C
A I
1
i
i
|
|
I
.°
35 0
,~,,.o°
~°o. °o,
° ° ° °°
D
,
preop.
+y X
4
E
postop. 12
2 cmJ
2 cmI
Fig. 1. A and B: theoretical possibilities for moving the direction of the net velocity from L to R tube in L --, R trials. Net velocity with orthogonal components before and at the onset of movement modification is illustrated. A: ~'increase. B: ~ decrease. C, D and E: relative distribution ofL ~ R trials grouped according to onsets of velocity alterations. Black: ~ decrease preceding ~, increase. White: # increase preceding decrease. Dotted: simultaneous ~' increase and ~t decrease. Number of trials in each group indicated. C and D: two different cats. D and E: same cat before and after a transection of the axons of the C3-C4 propriospinal neurones.
movement to get the reward. During each movement, the position o f a light-emitting diode fastened to the wrist of the cat was registered by two cameras. Every 3rd ms cartesian (x,y,z) coordinates were calculated by a minicomputer, z-Axis = vertical axis, x-axis = horizontal sagittal axis, y-axis = horizontal transverse axis. The horizontal rectangular components of the velocity of the forepaw (x,~) were obtained by numerical differentiation o f x,y. Deviations of X,y during switching trials exceeding samples of X,~, from all corresponding single trials indicate a significant alteration in x,~, and thus a correction of the movement. Fig. 1 shows the two theoretically possible ways of initiating a turn of the net velocity from the L to the R tube; directly (shown in A) by increasing ~, itself or indirectly (shown in B) by decreasing X. Both of them increase the relative role of ~ in determining the direction of the movement. The latter indirect way requires that ~ at the onset of each
255
correction has a direction which if ~ is lowered will automatically cause an adequate deviation. In other words, ~ has to be directed towards the R-tube. Such a direction would be favoured by the asymmetrical position of the left forelimb platform, i.e. in front of L-tube (cf. Fig. 1A, B).
A m/s
~
~.
:2
\
~,
X]
J
'
"
ms
3o~
~oo
•
•°
B m/s
f •° °°'° °~N~ ° " °
Y
ms
3ob
Fig. 2. Velocity profiles from 2 L -* R trims. Onset of alteration in Jt and ~, marked by th.ick and thin arrow, respectively. A: ~" altered before ~. B: ~ altered before ~.
256 Examples of real L --} R trajectories with corresponding velocity profiles are given in Fig. 2. In all L --* R trials, in intact cats, R decreased (although rather moderately in Fig. 2A) and ~, increased as a response to the switched illumination. These reactions did sometimes occur simultaneously (range of latency between them 0-36 ms). The sideways movement was, however, usually initiated either by increasing y (Fig. 2A) or decreasing ~ (Fig. 2B). In both exemplified trajectories this evoked a clearly visible movement deviation, and a change in the other velocity component occurred only about 30 ms later. In the latter example (Fig. 2B) an appropriate deviation was initiated because, when R was decreased, ~ was already directed towards the R tube. In fact, ~¢ was always properly directed in the time interval where corrections usually occurred. Each cat used both of the available methods to initiate changes in the direction of its trajectories but with a preference for one of them (compare Fig. 1C, D). In one cat this preference was changed after a transection of the axons of the C3-C4 propriospinal neurones (compare Fig. 1D, E). Since y is initially directed away from the L tube only one way exists in order to initiate a turn of net velocity from the R to the L tube, and this is to reverse the direction of ~ (see Fig. 3A). The turn of net velocity from R to L tube due to a reversal in y is schematically illustrated in Fig. 3B for a constant R. A decrease in ~ before ~ has reversed would in this case counteract an appropriate turn of net velocity. In the extreme case (see Fig. 3C) a profound decrease in x in parallel with the reversal in ~?would turn the net velocity back towards the R tube. Two characteristic examples of velocity profiles from real R --} L trials are shown in Fig. 3D. Both profiles are characterized by a distinct reversal of ~, (thin arrows). For A
D B
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b ".". a
"'%'""
...,. M,
'~
¸
- - -
5 4 3 2 1 •
C •
..
ms
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y
2~
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°
..'."
Fig. 3. A: theoretical possibility for moving the direction of the net velocity from R to L tube in a R ~ L trial. B: schematic illustration ofy reversal (broken arrows) with ~ (broken arrows) constant, at 5 substeps. The turn of net velocity is shown as solid arrows. C: schematic illustration of ~, reversal with a parallel decrease in ~ at 2 substeps. Note the inappropriate turn of net velocity. D: velocity profiles from 2 real R --, L trials (thick profiles correspond to trajectory a).
257 trajectories with a high initial excentricity towards the R tube (e.g. trajectory a in Fig. 3D) the reversal in ~ was accompanied by a decrease in ~ (thick arrow) which was, however, not large enough to prevent an adequate turn of net velocity. For trajectories with less excentricity, the decrease in ~ was less pronounced and in some cases (e.g. trajectory b in Fig. 3D) the switched illumination did not induce a decrease in ~. Decomposing net velocity into orthogonal velocity components (~,~,~) describes the kinematics of switching of target-reaching. Alterations in ~ and ~ as initial responses to a change in the location of the target can be selected by each animal individually and their interrelation can be changed by transecting the axons of the C3-C4 propriospinal neurones - a system known to mediate the command for target-reaching 3. Accordingly the initial response depends on nervous control and not exclusively on e.g. mechanical properties of the forelimb. Both in L ~ R as well as R ~ L trials deviations can be initiated by an alteration in only one velocity component. Particularly prominent are certain R --, L trials where an entire reversal in the direction of one component (~) is performed, during which a change in the other is avoided. However, simultaneous alterations in ~,~, were sometimes found both in L ~ R and R ~ L trials - in all cases with an interrelation giving the required movement path. These findings suggest that appropriate changes in direction of target-reaching can be initiated by exerting forces (on the forelimb) affecting separately either ~ or ~,. The results for corrections in the horizontal plane can be extended to three-dimensions by assuming a similar capacity for affecting the ~. component in isolation. Since visually guided switching ot" target-reaching occurs with very short latencies, which are prolonged by transection of the tectospinal and tecto-reticulospinal systems, it has been suggested that the visuomotor relay is subcortical in the superior colliculus 2. If so, it is noteworthy that subcortical processing may give appropriate scaling of the velocity components during switching of target reaching.
ACKNOWLEDGEMENT This work was supported by the Swedish Medical Research Council (Project No. 94).
REFERENCES 1 Aistermark,B., Eide, E., G6rska, T., Lundberg, A., and Pettersson, L.-G.,Visuallyguided switchingof forelimb target reaching in cats, Acta Physiol. Scand., 120 (1984) 151-153. 2 Alstermark,B., G6rska, T., Lundberg,A., Pettersson,L.-G.and Walkowska,M., Effectof differentspinal cord lesions on visuallyguided switching of target-reachingin cats, Neurosci. Res., 5 (1987) 63-67. 3 Alstermark, B., Lundberg, A., NorrseU, U. and Sybirska,E., Integration in descendingmotor pathways controllingthe forelimbin the cat. 9. Differentialbehaviouraldefectsaiderspinal cord lesions interrupting defined pathways from higher centres to motoneurones,Exp. Brain Res., 42 (1981) 299-318.
Neuroscience Research, 5 (1988) 253-257 Elsevier Scientific Publishers Ireland Ltd. NSR 00197
Short Communications
Alterations in vector components of the velocity of the forepaw during switching of target-reaching in the cat L.-G. Pettersson Department of Physiology, University of G~teborg, G~teborg (Sweden) (Received 27 April 1987; Accepted 26 September 1987)
Key words: Cat; Switching of target-reaching; Horizontal velocity component; Alteration
SUMMARY Switching of target-reaching in cats following a change in the location of the target is described kinematically as alterations in horizontal orthogonal velocity components. Alterations observed during real movement deviations are theoretically explained. Such deviations can be initiated by altering a single velocity component in isolation.
Cats are able to correct ongoing visually guided target-reaching with short response latencies following a change in the location of the target ~. To provide a kinematic description of such movement corrections, their velocity alterations in relevant motion directions have been studied and related to theoretical possibilities for modifying movement trajectories. The observations were made on 3 cats used by Alstermark et al.2 in a behavioural task described previously ~. In short: the cats were standing on platforms in front of two horizontal tubes with food (left = L, right = R tube) covered by locked opaque trap doors. The tubes were at the same horizontal level and the intercentre distance was 6 cm. Each tube could be illuminated and simultaneously unlocked during a predetermined time. The cats were trained to perform target-reaching to the illuminated tube and retrieve the food. Single trials, i.e. one tube illuminated during the entire movement (single L, single R trials), and switching trials, i.e. illumination switched to the other tube 50 ms after the onset of the movement (L ---,R, R ---,L trials), were given in pseudorandom series. During switching trials the animal had to modify its ongoing Correspondence: L.-G. Pettersson, Department of Physiology, University of GOteborg, P.O. Box 33031, S-400 33 GOteborg, Sweden. 0168-0102/88/$03.50 © 1988 Elsevier Scientific Publishers Ireland Ltd.
254
C
A I
1
i
i
|
|
I
.°
35 0
,~,,.o°
~°o. °o,
° ° ° °°
D
,
preop.
+y X
4
E
postop. 12
2 cmJ
2 cmI
Fig. 1. A and B: theoretical possibilities for moving the direction of the net velocity from L to R tube in L --, R trials. Net velocity with orthogonal components before and at the onset of movement modification is illustrated. A: ~'increase. B: ~ decrease. C, D and E: relative distribution ofL ~ R trials grouped according to onsets of velocity alterations. Black: ~ decrease preceding ~, increase. White: # increase preceding decrease. Dotted: simultaneous ~' increase and ~t decrease. Number of trials in each group indicated. C and D: two different cats. D and E: same cat before and after a transection of the axons of the C3-C4 propriospinal neurones.
movement to get the reward. During each movement, the position o f a light-emitting diode fastened to the wrist of the cat was registered by two cameras. Every 3rd ms cartesian (x,y,z) coordinates were calculated by a minicomputer, z-Axis = vertical axis, x-axis = horizontal sagittal axis, y-axis = horizontal transverse axis. The horizontal rectangular components of the velocity of the forepaw (x,~) were obtained by numerical differentiation o f x,y. Deviations of X,y during switching trials exceeding samples of X,~, from all corresponding single trials indicate a significant alteration in x,~, and thus a correction of the movement. Fig. 1 shows the two theoretically possible ways of initiating a turn of the net velocity from the L to the R tube; directly (shown in A) by increasing ~, itself or indirectly (shown in B) by decreasing X. Both of them increase the relative role of ~ in determining the direction of the movement. The latter indirect way requires that ~ at the onset of each
255
correction has a direction which if ~ is lowered will automatically cause an adequate deviation. In other words, ~ has to be directed towards the R-tube. Such a direction would be favoured by the asymmetrical position of the left forelimb platform, i.e. in front of L-tube (cf. Fig. 1A, B).
A m/s
~
~.
:2
\
~,
X]
J
'
"
ms
3o~
~oo
•
•°
B m/s
f •° °°'° °~N~ ° " °
Y
ms
3ob
Fig. 2. Velocity profiles from 2 L -* R trims. Onset of alteration in Jt and ~, marked by th.ick and thin arrow, respectively. A: ~" altered before ~. B: ~ altered before ~.
256 Examples of real L --} R trajectories with corresponding velocity profiles are given in Fig. 2. In all L --* R trials, in intact cats, R decreased (although rather moderately in Fig. 2A) and ~, increased as a response to the switched illumination. These reactions did sometimes occur simultaneously (range of latency between them 0-36 ms). The sideways movement was, however, usually initiated either by increasing y (Fig. 2A) or decreasing ~ (Fig. 2B). In both exemplified trajectories this evoked a clearly visible movement deviation, and a change in the other velocity component occurred only about 30 ms later. In the latter example (Fig. 2B) an appropriate deviation was initiated because, when R was decreased, ~ was already directed towards the R tube. In fact, ~¢ was always properly directed in the time interval where corrections usually occurred. Each cat used both of the available methods to initiate changes in the direction of its trajectories but with a preference for one of them (compare Fig. 1C, D). In one cat this preference was changed after a transection of the axons of the C3-C4 propriospinal neurones (compare Fig. 1D, E). Since y is initially directed away from the L tube only one way exists in order to initiate a turn of net velocity from the R to the L tube, and this is to reverse the direction of ~ (see Fig. 3A). The turn of net velocity from R to L tube due to a reversal in y is schematically illustrated in Fig. 3B for a constant R. A decrease in ~ before ~ has reversed would in this case counteract an appropriate turn of net velocity. In the extreme case (see Fig. 3C) a profound decrease in x in parallel with the reversal in ~?would turn the net velocity back towards the R tube. Two characteristic examples of velocity profiles from real R --} L trials are shown in Fig. 3D. Both profiles are characterized by a distinct reversal of ~, (thin arrows). For A
D B
5 4 3 2 1
"'%'""
b ".". a
"'%'""
...,. M,
'~
¸
- - -
5 4 3 2 1 •
C •
..
ms
•' " ' ~ ' ~
y
2~
2
°
..'."
Fig. 3. A: theoretical possibility for moving the direction of the net velocity from R to L tube in a R ~ L trial. B: schematic illustration ofy reversal (broken arrows) with ~ (broken arrows) constant, at 5 substeps. The turn of net velocity is shown as solid arrows. C: schematic illustration of ~, reversal with a parallel decrease in ~ at 2 substeps. Note the inappropriate turn of net velocity. D: velocity profiles from 2 real R --, L trials (thick profiles correspond to trajectory a).
257 trajectories with a high initial excentricity towards the R tube (e.g. trajectory a in Fig. 3D) the reversal in ~ was accompanied by a decrease in ~ (thick arrow) which was, however, not large enough to prevent an adequate turn of net velocity. For trajectories with less excentricity, the decrease in ~ was less pronounced and in some cases (e.g. trajectory b in Fig. 3D) the switched illumination did not induce a decrease in ~. Decomposing net velocity into orthogonal velocity components (~,~,~) describes the kinematics of switching of target-reaching. Alterations in ~ and ~ as initial responses to a change in the location of the target can be selected by each animal individually and their interrelation can be changed by transecting the axons of the C3-C4 propriospinal neurones - a system known to mediate the command for target-reaching 3. Accordingly the initial response depends on nervous control and not exclusively on e.g. mechanical properties of the forelimb. Both in L ~ R as well as R ~ L trials deviations can be initiated by an alteration in only one velocity component. Particularly prominent are certain R --, L trials where an entire reversal in the direction of one component (~) is performed, during which a change in the other is avoided. However, simultaneous alterations in ~,~, were sometimes found both in L ~ R and R ~ L trials - in all cases with an interrelation giving the required movement path. These findings suggest that appropriate changes in direction of target-reaching can be initiated by exerting forces (on the forelimb) affecting separately either ~ or ~,. The results for corrections in the horizontal plane can be extended to three-dimensions by assuming a similar capacity for affecting the ~. component in isolation. Since visually guided switching ot" target-reaching occurs with very short latencies, which are prolonged by transection of the tectospinal and tecto-reticulospinal systems, it has been suggested that the visuomotor relay is subcortical in the superior colliculus 2. If so, it is noteworthy that subcortical processing may give appropriate scaling of the velocity components during switching of target reaching.
ACKNOWLEDGEMENT This work was supported by the Swedish Medical Research Council (Project No. 94).
REFERENCES 1 Aistermark,B., Eide, E., G6rska, T., Lundberg, A., and Pettersson, L.-G.,Visuallyguided switchingof forelimb target reaching in cats, Acta Physiol. Scand., 120 (1984) 151-153. 2 Alstermark,B., G6rska, T., Lundberg,A., Pettersson,L.-G.and Walkowska,M., Effectof differentspinal cord lesions on visuallyguided switching of target-reachingin cats, Neurosci. Res., 5 (1987) 63-67. 3 Alstermark, B., Lundberg, A., NorrseU, U. and Sybirska,E., Integration in descendingmotor pathways controllingthe forelimbin the cat. 9. Differentialbehaviouraldefectsaiderspinal cord lesions interrupting defined pathways from higher centres to motoneurones,Exp. Brain Res., 42 (1981) 299-318.