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[0] Evarts EV, Relation of pyramidal tract activity to force exerted during voluntary movement.J Neurophysiol 31:1, 14-27 (1968 Jan)

[0] BASMAJIAN JV, Control and training of individual motor units.Science 141no Issue 440-1 (1963 Aug 2)

[0] Evarts EV, Activity of pyramidal tract neurons during postural fixation.J Neurophysiol 32:3, 375-85 (1969 May)[1] Evarts EV, Relation of pyramidal tract activity to force exerted during voluntary movement.J Neurophysiol 31:1, 14-27 (1968 Jan)

[0] Fetz EE, Perlmutter SI, Prut Y, Functions of mammalian spinal interneurons during movement.Curr Opin Neurobiol 10:6, 699-707 (2000 Dec)

[0] Aflalo TN, Graziano MS, Relationship between unconstrained arm movements and single-neuron firing in the macaque motor cortex.J Neurosci 27:11, 2760-80 (2007 Mar 14)

[0] Moran DW, Schwartz AB, Motor cortical representation of speed and direction during reaching.J Neurophysiol 82:5, 2676-92 (1999 Nov)

[0] Sergio LE, Kalaska JF, Systematic changes in directional tuning of motor cortex cell activity with hand location in the workspace during generation of static isometric forces in constant spatial directions.J Neurophysiol 78:2, 1170-4 (1997 Aug)

[0] Cheney PD, Fetz EE, Functional classes of primate corticomotoneuronal cells and their relation to active force.J Neurophysiol 44:4, 773-91 (1980 Oct)

[0] Fu QG, Flament D, Coltz JD, Ebner TJ, Temporal encoding of movement kinematics in the discharge of primate primary motor and premotor neurons.J Neurophysiol 73:2, 836-54 (1995 Feb)

[0] Won DS, Wolf PD, A simulation study of information transmission by multi-unit microelectrode recordings.Network 15:1, 29-44 (2004 Feb)

[0] Li CS, Padoa-Schioppa C, Bizzi E, Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field.Neuron 30:2, 593-607 (2001 May)[1] Caminiti R, Johnson PB, Urbano A, Making arm movements within different parts of space: dynamic aspects in the primate motor cortex.J Neurosci 10:7, 2039-58 (1990 Jul)

[0] Kalaska JF, Cohen DA, Hyde ML, Prud'homme M, A comparison of movement direction-related versus load direction-related activity in primate motor cortex, using a two-dimensional reaching task.J Neurosci 9:6, 2080-102 (1989 Jun)

[0] Wetts R, Kalaska JF, Smith AM, Cerebellar nuclear cell activity during antagonist cocontraction and reciprocal inhibition of forearm muscles.J Neurophysiol 54:2, 231-44 (1985 Aug)

[0] Taira M, Boline J, Smyrnis N, Georgopoulos AP, Ashe J, On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional static isometric force.Exp Brain Res 109:3, 367-76 (1996 Jun)

[0] Amirikian B, Georgopoulos AP, Directional tuning profiles of motor cortical cells.Neurosci Res 36:1, 73-9 (2000 Jan)

[0] Georgopoulos AP, Kalaska JF, Caminiti R, Massey JT, On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.J Neurosci 2:11, 1527-37 (1982 Nov)

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ref: -0 tags: globus pallidus delong response tuning date: 02-24-2012 21:41 gmt revision:1 [0] [head]

PMID-4997823 Activity of Pallidal Neurons During Movement

  • GPe activity notably different from GPi.
    • "So characteristic were the discharge patterns of units in each segment that early in the course of the experiment ti be came apparent when the electrode entered and left each segment.
  • Two types of cells in GPe:
    • High frequency with periods of quiet (85%)
    • Low frequency with bursts.
  • Only one type in GPi: continuous HF discharge, 10-100 Hz, mean 63 Hz.
  • Mostly contralateral, ~ 15% ipsilateral related discharge.
  • Leg and arm responding units intermixed.
  • Conclusion: pallidus not involved in reflexes.
  • Substantia innominata = region posterior the pallidus, contains the nucleus basalis.
  • I'd really like to get recordings of this quality!

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ref: Evarts-1968.01 tags: Evarts motor control pyramidal tract M1 PTN tuning date: 01-16-2012 18:59 gmt revision:4 [3] [2] [1] [0] [head]

PMID-4966614[] Relation of pyramidal tract activity to force exerted during voluntary movement

  • PTNs with high conduction velocity tend to be silent during motor quiescence and show phasic activity with movement.
  • PTNs with lower axonal conduction velocities are active in the absence of movement; with movement they show both upward and downward modulations of the resting discharge.
  • many PTNs responded to a conditional stimulus before the movement.
  • in this study, they wanted to determine if phasic response was more correlated with displacement or with force.
    • did this with two different motions (flexion and extension) in two different force loads (opposing flexion and opposing extransion)
      • movements were slow (or at least nonballistic) and somewhat controlled - they had to last between 400 and 700ms.
      • monkeys usually carried out 3,000 cycles of the movement daily !!
  • "prior to the experiment, hte authour was biased to think that the displacement model (where the cortex commands a location/movement of the arm, which is then accomplished through feedback & feedforward mechanisms e.g. in the spinal cord) was correct; experimental results seem to indicate that force is very strongly represented in PTN population.
  • many PTN firing rates reflected dF/dt very strongly.
  • old, good paper. made with 'primitive' technology - but why do we need to redo this?

____References____

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ref: Chestek-2007.1 tags: M1 cortex reaching tuning date: 01-15-2012 22:08 gmt revision:1 [0] [head]

PMID-17913908[0] Single-Neuron Stability during Repeated Reaching in Macaque Premotor Cortex

  • Neural activity was predominantly stable over time in all measured properties: firing rate, directional tuning, and contribution to a decoding model that predicted kinematics from neural activity. The small changes in neural activity that we did observe could be accounted for primarily by subtle changes in behavior. We conclude that the relationship between neural activity and practiced behavior is reasonably stable, at least on timescales of minutes up to 48 h.
    • Makes sense.
    • Good for neuroprosthetics.

____References____

[0] Chestek CA, Batista AP, Santhanam G, Yu BM, Afshar A, Cunningham JP, Gilja V, Ryu SI, Churchland MM, Shenoy KV, Single-neuron stability during repeated reaching in macaque premotor cortex.J Neurosci 27:40, 10742-50 (2007 Oct 3)

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ref: BASMAJIAN-1963.08 tags: original BMI M1 human EMG tuning operant control Basmajian date: 01-05-2012 00:49 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-13969854[0] Control and Training of Individual Motor Units

  • humans have the ability to control the firing rate of peripheral motor units with a high resolution.
  • "The quality of control over anterior horn cells may determine the rates of learning" yup!
  • "Some learn such esquisite control that they soon can produce rhythms of contraction in one unit, imitating drum rolls etc"
  • the youngest persons were among both the best and worst learners.
  • after about 30 minutes the subject was required to learn how to repress the first unit and to recruit another one.
    • motor unit = anterior horn cell, its axon, and all the muscle fibers on which the terminal branches of the axon end. max rate ~= 50hz.
    • motor units can be discriminated, much like cortical neurons, by their shape.
    • some patients could recruit 3-5 units altogether - from one bipolar electrode!
      • in playback mode (task: trigger the queried unit), several subjects had particular difficulty in recruiting the asked-for units. "They groped around in their conscious efforts to find them sometimes, it seemed, only succeded by accident"
    • some patients could recruit motor units in the absence of feedback, but they were unable to explain how they do it.
  • 0.025 (25um) nylon-insulated Karma alloy EMG recording wire.
  • feedback: auditory & visual (oscilloscope).
  • motor units have a maximum rate, above which overflow takes place and other units are recruited (in accord with the size principle).
  • "The controls (are) learned so quickly, are so esquisite, are so well retained after the feedbacks are eliminated that one must not dismiss them as tricks"

____References____

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ref: Lilly-1958 tags: Lilly MEA original neural tuning date: 01-04-2012 02:15 gmt revision:4 [3] [2] [1] [0] [head]

bibtex: Lilly-1958 Correlations between Neurophysiological Activity in the Cortex and Short-Term Behavior in the Monkey

  • 610 channels in 'Susie'! Unable to record from all of them for lack of recording technology.
  • references the rest of his work.
  • Was able to elicit pretty dramatic and fascinating stimulation responses:
    • 'shrink' as if warding off a blow to the contralateral side of the head;
    • at an adjacent electrode we found a pattern called 'goose', this pattern involved the whole body, and the reaction looks as if the monkey had been forcefully, mechanically stimulated par anum.
    • both were accompanied by high arousal.
  • Suggest that behavioral frequency-of-use corresponds rounghly to cortical rank-area order.
  • Note that the wave velocity (as imaged by his bavatron) in cortex can vary dramatically, from 1 m/sec to 0.1 m/sec.
    • With practice, one can see the boundaries between the 'arm' and 'leg' regions quite easily.
  • Stated our problem quite concisely: "One of the large difficulties in correlating structure, behavior, and CNS activity is the spatial problem of getting enough electrodes, and small enough electrodes, \emph{in} there with minimal injury. (This is why he was usnig pial electrodes). Still another problem is getting enough samples from each electrode per unit time, over a long enough time, to see what goes on during conditioning or learning [...] s for the problem of the investigator's absorbing the data -- if he has adequate recording techniques, he has a lot of time to work on a very short recorded part of a given monkey's life."
  • no figures :-(
  • Lilly could publish. a b -- though he appears to have ADHD (perhaps from the LSD)
    • also see his homepage -- He died in 2001, but it's still up.
  • images/1016_1.pdf

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ref: Evarts-1969.05 tags: Evarts pyramidal tract motor control M1 tuning date: 01-03-2012 23:08 gmt revision:2 [1] [0] [head]

PMID-4977837[0] Activity of Pyramidal Tract neurons during postural fixation

  • Force was thus dissociated from displacement, and it was possible to determine whether PTN discharges were related to position or force.
  • for the majority of PTNs discharge frequency was related to to the magnitude and rate of change of force rather than to the joint position or the speed of joint movement (same as the MUA in the Kinarm data!!)
  • task was simple: just try to avoid joint movement.
  • in comparison to [1] where PTN were related to force under joint displacement, this task shows they are still related to force even when the joint angle is fixed.
  • used sharpened tungsten electrodes to record 102 pyramidal tract neurons.
  • monkeys were trained to do the tasks in their home cages (obviously weren't recorded there - need to be headposted)
  • I'm not sure how he determined if it was or was not a pyramidal tract neuron.

____References____

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ref: Fetz-2000.12 tags: motor control spinal neurons interneurons movement primitives Fetz review tuning date: 01-03-2012 23:08 gmt revision:4 [3] [2] [1] [0] [head]

PMID-11240278[0] Functions of mammalian spinal interneurons during movement

  • this issue of current opinion in neuro has many reviews of motor control
  • points out that the Bizzi results (they microstimulated & observed a force-field-primitive type organization)
    • others have found that this may be a consequence of decerebration + the structure of the biomechanical groupings of muscles. (see 'update').
  • intraspinal electrodes in the cat provide a secure and reliable method of eliciting forces and movements.
  • CM (corticomotor) cells more often represent synergistic groups of muscles, whereas premotor spinal interneurons are organized to target specific muscles.
    • CMs are therefore more strictly recruited for particular movements.
  • interneurons (IN) are, of course, arrayed in such a way so that antagonist and agonist muscles cross-inhibit eachother (for efficiency)
    • however, we are still able to control the endpoint impedance of the arm - how?
  • spinal interneurons modulate activity during wait period prior to movement!
    • there might be substantial interaction between the cortex and spinal cord.. subjects asked to imagine pressing a foot pedal showed enhanced reflexes in the involved soleus muscle.
      • cognitive priming?
  • spinal reflexes are strongly modulated in movement.

____References____

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ref: Aflalo-2007.03 tags: Graziano motor cortex M1 SUA macaque monkey electrophysiology tuning date: 01-03-2012 03:37 gmt revision:1 [0] [head]

PMID-17360898[] Relationship between Unconstrained Arm Movements and Single-Neuron Firing in the Macaque Motor Cortex

  • the best explanation of neuronal firing was the final mulijoint configuration of the arm - it accounted for 36% of the SUA variance.
  • the search for the 'correct' motor parameter (that neurons are tuned to) is an ill-posed experimental question because motor parameters are very intercorrelated.
  • they knock experiments in which the animals are overtrained & the movements limited - and they are right!
  • single electrode recording with cronically implanted steel chamber - e.g. it took a damn long time!
    • imaged the central sulcus through the dura.
    • verified location with single unit responses to palpation of the contralateral hand/arm (in S1) & microstimulation-evoked movements in M1.
  • used optotrak to measure the position of the monkey.
  • occasionally, the monkey attemptted to scratch the experimenter with fast semi-ballistic arm movement. heh. :)
  • movements were seprarated based on speed analysis - that is, all the data were analyzed as discrete segments.
  • neurons were inactive during periods of hand stasis between movements.
  • tested the diversity of their training set in a clever way: they simulated neurons tuned to various parameters of the motion, and tested to see if their analysis could recover the tuning. it could.
    • however, they still used unvalidated regression analysis to test their hypothesis. regression analysis estimates how much variance is estimated by the cosine-tuning model - it returns an R^2.
  • either averaged the neuronal tuning over an entire movement or smoothed the firing rate using a 10hz upper cutoff.
  • Moran & Schwartz' old result seems to be as much a consequence of averaging across trials as it is a consequence of actual tuning...
    • whithout the averaging, only 3% of the variance could be attributed to speed tuning.
  • i think that they have a good point in all of this: when you eliminate sources of variance (e.g. starting position) from the behavior, either by mechanical restraint or simple omission of segments or even better averaging over trials, you will get a higher R^2. but it may be false, a compression of the space along an axis where they are not well correlated!
  • a model in which the final position matters little, but the velocity used to get there does, has been found to account for little of the neuronal variance.
    • instead, neurons are tuned to any of a number of movements that terminate near a preferred direction.
  • observational studies of of the normal psontaneous behavior of monkeys indicate that a high proportion of time is spent using the arm as a postural device.
    • therefore, they expect that neurons are tuned to endpoint posture.
    • modeled the neuronal firing as a gaussian surface in the 8-dimensional space of the arm posture.
  • in comparison to other studies, the offset between neural activity and behavior was not significantly different, over the entire population of recorded neurons, from zero. This may be due to the nature of the task, which was spontaneous and ongoing, not cue and reaction based, as in many other studies.
    • quote: This result suggests that the neuronal tuning to posture reflects reatively more and anticipation of the future state of the limb rather than a feedback signal about a recent state of the limb.

____References____

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ref: Moran-1999.11 tags: electrophysiology motor cortex Schwartz Moran M1 tuning date: 01-03-2012 03:36 gmt revision:2 [1] [0] [head]

PMID-10561437[0] Motor cortical representation of speed and direction during reaching

  • velocity is represented in the motor cortex.
  • they developed an equation relating firing rate to the position and velocity.
  • EMG direction had significantly different tuning from the cortical activity
    • the effect of speed on EMG was also different.
  • used single-electrode recording - 1,066 cells!!
  • introduce the square-root transformation of the firing rate (from Ashe and Georgopolous 1994)

____References____

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ref: Fu-1993.11 tags: electrophysiology Ebner premotor motor tuning M1 date: 01-03-2012 03:34 gmt revision:1 [0] [head]

PMID-8294972 Neuronal specification of direction and distance during reaching movements in the superior precentral premotor area and primary motor cortex of monkeys. 1993

  • trained monkey to do center-out task, 48 targets (8 angles, 6 distances).
  • single-electrode recording of 197 neurons in the primary motor and secondary motor / premotor (in the superior precentral sulcus).
  • cells were mostly tuned to direction, and less to distance, in both the premovement and movement periods. distance tuning was much stronger in the movement period.
    • tuning was measure by average firing rate for the premovement, movement, and total periods.
  • long, very detailed!

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ref: Donoghue-1990.01 tags: Donoghue Suner Sanes rat motor cortex reorganization M1 tuning surprising date: 01-03-2012 03:30 gmt revision:4 [3] [2] [1] [0] [head]

PMID-2340869[0] Dynamic organization of primary motor cortex output to target muscles in adult rats. II. Rapid reorganization following motor nerve lesions.

  1. Map out the motor cortex into vibrissa and forelimb areas using ICMS.
  2. Implant a simulating electrode in the vibrissa motor cortex.
  3. Implant EMG electrodes in the forearm.
  4. Sever the buccal and mandibular branches of the facial nerve.
  5. stimulate, and wait for forearm EMG to be elicited by ICMS. Usually occurs! Why? Large horizontal axons in motor cortex? Uncovering of silent synapses, and homeostatic modulation of firing rates?

____References____

[0] Donoghue JP, Suner S, Sanes JN, Dynamic organization of primary motor cortex output to target muscles in adult rats. II. Rapid reorganization following motor nerve lesions.Exp Brain Res 79:3, 492-503 (1990)

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ref: -0 tags: Evarts force pyramidal tract M1 movement monkeys conduction velocity tuning date: 01-03-2012 03:25 gmt revision:3 [2] [1] [0] [head]

PMID-4966614 Relation of pyramidal tract activity to force exerted during voluntary movement.

  • One of the pioneering studies of electrophysiology in awake behaving animals; single electrode juice reward headposting: many followed.
  • {960} looked at conduction velocity, which we largely ignore now -- most highly mylenated axons are silent during motor quiescence and show phasic activity during movement.
    • Lower conduction velocity PTNs show + and - FR modulations. Again from [5]
  • [6] showed that PTN activity preceded EMG activity, implying that it was efferent rather than afferent feedback that was controlling the fr. as expected.
  • task: wrist flexion & extension under load.
  • task in monkey's home cage for a period of three months; monkeys carried out 3000 trials or more of the task (must have had strong wrists!)
  • Head fixated the monkeys for about 10 days prior unit recordings; "The monkeys learned to be quite cooperative in reentering the chair in the morning, since entrance to the chair was rewarded by the fruit juice of their choice (grape, apple, or orange). Indeed, some monkeys continued to work even in the presence of free water!
    • Maybe I should give mango some Hawaiian punch as well?
  • Mesured antidromic responses with a permanent electrode in the ipsilateral medullary pyramid.
  • Used glass insulated platinum-iridium electrodes [11]
  • traces are clean, very clean. I wonder if good insulation (in this case, glass) has anything to do with it?
  • controlled for displacement by varying the direction of load; PTNs seem to directly control muscles.
    • Fire during acceleration and movement for no load
    • Fire during load and co-contraction when loaded.
  • FR also related to δF/δt\delta F / \delta t : FR higher during a low but rising force than a high but falling force.
  • more than 100 PTN recorded from the precentral gyrus, but only 31' had clear and consistent relation to performance on the task.
    • 16 units on extension loads, 7 units flexion loads
    • It was only one joint afterall..
  • Cells responding to the same movement (flexion or extension) were often founf on the same vertical electrode tract.
  • Very little response to joint position.
  • Very clean moculations -- neurons are almost silent if there is no force production; FR goes up to 50-80Hz.
  • Prior to the exp Evart expected a position tuning model, but saw clear evidence of force tuning.
  • Group 1 muscle afferents have now been shown to project to the motor cortex of both monkey [1] and cat [9]. Make sense, as if the ctx is to control force, it needs feedback regarding its production.
  • Caveats: many muscles were involved in the study, mainly due to postural effects, and having one or two controls poorly delineates what is going on in the motor ctx.
    • Plus, all the muscles controlling the figers come into play -- the manipulandum must be gripped firmly, esp to resist extension loads.

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ref: Sergio-1997.08 tags: M1 force tuning kinematics dynamics Kalaska date: 01-03-2012 02:31 gmt revision:1 [0] [head]

PMID-9307146[0] Systematic changes in directional tuning of motor cortex cell activity with hand location in the workspace during generation of static isometric forces in constant spatial directions.

  • The discharge rate of all proximal-arm M1 cells was affected by both hand location and by the direction of static force. w/ interaction between force direction and hand location.
    • this is consistent with cortical units controlling muscle activity directly or through the spinal cord.
  • conclusion: M1 controls muscles directly and contributes to the transformation from extrinsic coordinates to muscle activations while coordinating limb movements.

____References____

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ref: Cheney-1980.1 tags: M1 kinematics dynamics tuning STA EMG Fetz date: 01-03-2012 02:30 gmt revision:3 [2] [1] [0] [head]

PMID-6253605[0] Functional classes of primate corticomotoneuronal cells and their relation to active force

  • monkeys made ramp and hold torque wrist movements/contractions.
  • corticomotoneuronal cells identified by clear postspike facilitation of rectified EMG activity.
  • all CM cells or PTNs were related to force - with a mixture/diversity of phasic, tonic, and ramp discharge rate profiles.
  • torque trajectory rather than velocity signal seems to be the primnary determinant of cell firing rate...
  • cells appear to be recruited at low force levels..with increasing rates as the torque increases.
  • high firing rates observed > 100!
    • and really low firing rate when there was no torque.

____References____

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ref: Fu-1995.02 tags: M1 motor tuning kinematics dynamic direction date: 01-03-2012 02:21 gmt revision:1 [0] [head]

PMID-7760138[0] Temporal encoding of movement kinematics in the discharge of primate primary motor and premotor neurons

  • 48 target 2D center out task
  • wanted to disambiguate temporal aspects of tuning vs. parallel (e.g. across a neuronal population) aspects of tuning.
  • On average we found a clear temporal segregation and ordering in the onset of the parameter-related partial R2 values: direction-related discharge occurred first (115 ms before movement onset), followed sequentially by target position (57 ms after movement onset) and movement distance (248 ms after movement onset).
  • therefore, the motor cortex seems to have strong temporal processing aspects. duh.
    • Probably explained by Todorov ...

____References____

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ref: -0 tags: todorov R2 M1 PV tuning bias decision boundaries controversy date: 12-22-2011 22:52 gmt revision:1 [0] [head]

PMID-11017160 Reply to One motor cortex, two different views

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ref: -0 tags: Georgopoulos 1988 population vector tuning date: 12-20-2011 01:13 gmt revision:1 [0] [head]

PMID-3411362[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.

  • This is the paper where they do predictions, and show that they can offline 'decode' 3D reaching movements.
    • Pretty spiffy 3D graphics, too.
  • Used three analyses to estimate variability of the population vector.
    • 1. Random sampling of the experimentally observed population (N= 475), using the mean discharge rate of each cell to each direction.
    • 2. Same cell population, but variability of discharge was drawn from a normal distro estimated from the mean and variance of the trial-to-trial recordings.
    • 3. Random sampling + trial-to-trial variability.
  • Plot 95% confidence interval over population size for the estimated direction; asymtopes at about 15%. Why not measured in steradians?
  • Figure 4 looks to have good SNR, and they look to be dataheads.
  • Use a bunch of different weighting functions to calculate the population vector; no numerical optimization?
    • best one basically looks like normalized, mean-removed firing rate.

____References____

[0] Georgopoulos AP, Kettner RE, Schwartz AB, Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population.J Neurosci 8:8, 2928-37 (1988 Aug)

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ref: -0 tags: Georgopoulos 1988 M1 population vector tuning 3D single unit date: 12-20-2011 00:58 gmt revision:2 [1] [0] [head]

PMID-3411363[0] Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.

  • In comparison to the first experiment, where they showed that movement direction was encoded by single units within M1, here they varied the starting position of the movements.
  • tonic discharge of many cells varied in and orderly fashion with the position at which the hand was actively maintained in space.
  • however, cell activity changes were the same independent of movement onset and dependent on movement direction.
    • similar but not that similar -- vary based on tonic firing rate. See figure 9.

____References____

[0] Kettner RE, Schwartz AB, Georgopoulos AP, Primate motor cortex and free arm movements to visual targets in three-dimensional space. III. Positional gradients and population coding of movement direction from various movement origins.J Neurosci 8:8, 2938-47 (1988 Aug)

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ref: Georgopoulos-1982.11 tags: Georgopoulos 1982 motor tuning cortex M1 population vector date: 12-19-2011 23:52 gmt revision:1 [0] [head]

PMID-7143039 On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex.

  • eight directions 45deg intervals, 2D joystick, frictionless, LED tarkets in a blocked randomized experimental design.
    • MK made simultaneous saccades; saccade latency 150-170ms.
      • some motor cells responded to visual movement.
    • EMG activity began ~80ms before movement.
    • monkeys used both arms.
  • bell-shaped or cosine tuning in 75% of the cells.
    • This has also been described in the saccade system in the paramedian pontine reticular formation (Henn and Cohen 1976), the mesencelphatic reticular formation (Buttner eta la 1977) and the internal medullary lamina of the thalamus (Schlag and Schlag-Ney 1977)
  • cells tended to cluster by tuning in depth.
  • cells tended to respond to movement & small corrections to movement, but did not necessarily respond to non-task related movement. "Yet these same cells were frequently silent during other movements which also involved contraction of the same muscles [as used in the task]"
  • cell discharge was much stronger during active movements than during passive manipulations.
  • 64% of cells were activated before the earliest EMG changes; 87% before the onset of movement.
  • The famous one, where the population vector was formalized / conceived / validated.
  • most neurons begin firing ~ 100ms before movement begins.
  • useda PDP11/20 minicomputer to control the LEDs & data recording.
  • Thach 1978 -- approxmately equal proportions of motor cortical cells were related to muscle activity, hans position, and direction of intended movement Thach 1978) PMID-96223
  • single electrode Pt/Ir recording 2-3Mohm; recordings made for 6-7 hours.
  • cite georgopoulos 1983 -- they propose distributed population coding.
  • point out that the central problem -- upon which some progress has been made - is the translation between visual and motor coordinate frames.

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ref: Won-2004.02 tags: Debbie Won Wolf spike sorting mutual information tuning BMI date: 12-07-2011 02:58 gmt revision:3 [2] [1] [0] [head]

PMID-15022843[0] A simulation study of information transmission by multi-unit microelectrode recordings key idea:

  • when the units on a single channel are similarly tuned, you don't loose much information by grouping all spikes as coming from one source. And the opposite effect is true when you have very differently tuned neurons on the same channel - the information becomes more ambiguous.

____References____

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ref: Li-2001.05 tags: Bizzi motor learning force field MIT M1 plasticity memory direction tuning transform date: 09-24-2008 22:49 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-11395017[0] Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field

  • this is concerned with memory cells, cells that 'remember' or remain permanently changed after learning the force-field.
  • In the above figure, the blue lines (or rather vertices of the blue lines) indicate the firing rate during the movement period (and 200ms before); angular position indicates the target of the movement. The force-field in this case was a curl field where force was proportional to velocity.
  • Preferred direction of the motor cortical units changed when the preferred driection of the EMGs changed
  • evidence of encoding of an internal model in the changes in tuning properties of the cells.
    • this can suppor both online performance and motor learning.
    • but what mechanisms allow the motor cortex to change in this way???
  • also see [1]

____References____

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ref: Kalaska-1989.06 tags: motor control direction tuning force Kalaska date: 04-09-2007 19:59 gmt revision:2 [1] [0] [head]

PMID-2723767[0] A comparison of movement direction-related versus load direction-related activity in primate motor cortex, using a two-dimensional reaching task.

  • comparison to georoplous task:
    • "We demonstrate here that many of these cells show similar large continuously graded changes in discharge when the monkey compensates for inertial loads which pull the arm in 8 different directions"
  • the mean activity of the sample population under any condition of movement direction and load direction can be described reasonably well by a simple linear summation of the movement-related discharge without any loads, and the change in tonic activity of the population caused by the load, measured prior to movement
  • their data support the dual kinematics/dynamics encoding in the motor cortex.
    • but, to me, the data also supports direct control of the muscles.

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ref: Wetts-1985.08 tags: Kalaska isometric motor control dentate cerebellum purkinje M1 pyramidal tract direction tuning date: 04-09-2007 19:54 gmt revision:0 [head]

PMID-3928831[0] Cerebellar nuclear cell activity during antagonist cocontraction and reciprocal inhibition of forearm muscles. by kalaska concering the interpositus dentate & isometric task.

  • the dentate nucleus sends afferents to the premotor areas. GABAergic inhibition from purkinje cells.
  • not so much tuning in the dentate nucleus as M1, but positive correlation was found.
  • Purkinje cells had a general low-order negative tuning to muscle activations.

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ref: Taira-1996.06 tags: 3D Georgopoulos SUA M1 force motor control direction tuning date: 04-09-2007 15:16 gmt revision:1 [0] [head]

PMID-8817266[0] On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional static isometric force.

  • 3D isometric joystick.
  • stepwise multiple linear regression.
  • direction of force is a signal especially prominent in the motor cortex.
    • the pure directional effect was 1.8 times more prevalent in the cells than in the muscles studied (!)

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ref: Amirikian-2000.01 tags: Georgopulos directional tuning motor cortex SUA electrophysiology date: 04-05-2007 16:34 gmt revision:2 [1] [0] [head]

PMID-10678534[0] Directional tuning profiles of motor cortical cells

  • trained the monkeys to move to 20 targets in a horizontal plane
    • the larger number of targets allowed a more accurate estimation of the tuning properties of the cells
    • measured tuning based on the spike count during movement.
  • typical r^2 = 0.7 for a modified cosine fit

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ref: Georgopoulos-1982.11 tags: georgopoulos kalaska caminiti M1 motor control tuning population_vector date: 04-05-2007 16:27 gmt revision:0 [head]

PMID-7143039[0] On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex

  • famous 8-target center out task
  • dot-product tuning
  • 75% of cells were found to be tuned.
  • posits the population code for directional movements - statistical summation & averaging, i presume.

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