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[0] Carmena JM, Lebedev MA, Henriquez CS, Nicolelis MA, Stable ensemble performance with single-neuron variability during reaching movements in primates.J Neurosci 25:46, 10712-6 (2005 Nov 16)

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ref: RodriguezOroz-2001.09 tags: STN SNr parkinsons disease single unit recording spain 2001 tremor oscillations DBS somatotopy organization date: 02-22-2012 18:24 gmt revision:12 [11] [10] [9] [8] [7] [6] [head]

PMID-11522580[0] The subthalamic nucleus in Parkinson's disease: somatotopic organization and physiological characteristics

  • Looks like they discovered exactly what we have discovered ... only in 2001. This is both good and bad.
    • From the abstract: "Neurones responding to movement were of the irregular or tonic type, and were found in the dorsolateral region of the STN. Neurones with oscillatory and low frequency activity did not respond to movement and were in the ventral one-third of the nucleus. Thirty-eight tremor-related neurones were recorded."
  • Again, from the abstract: "The findings of this study indicate that the somatotopic arrangement and electrophysiological features of the STN in Parkinson's disease patients are similar to those found in monkeys."
  • It may be that we want to test differential modulation / oscillation: look for differences between rest and activity, if there is sufficient support for both these in the files we have.
  • These people were much, much more careful about localization of their single-electrode tracks. E.g. they calculated electrode location relative the DBS electrode stereotatically, and referenced this to the postoperative MRI location of the treatment electrode.
  • Many more (32% of 350 neurons) responded to active or passive movement.
  • Of this same set, 15% (31 neurons) had a firing rate with rhythmical activity; 38 neurons had rhythmic activity associated with oscillatory EMG, but most of these were responsive to passive stimulation.
  • Autocorrelation of the neuronal bursting and tremor peaked at mean 7Hz, while autocorr. of EMG peaked at mean 5Hz.
  • This whole paragraph is highly interesting: ''The neuronal response associated with active movements was studied by simultaneous recording of neuronal EMG activity of the limbs. Five tremor-related neurons, recorded while a voluntary movement was performed, were available for analysis. Voluntary activation of a particular limb segment arrested the tremor. This was associated with a change in the discharges of the recorded neuron, which fired at a slower rate and in synchrony with the voluntary movement. On occasions, freezing of the voluntary movement ensued and tremor reappeared, changing the neuronal activity back to the typical 4-5Hz tremor-related activity. The cross-correlation analysis of two such neurons showed a peak frequency of 4.63 and 4.88 Hz for tremor-related activity, and 1.5 to 1.38 Hz during voluntary movement. Whether neuronal discharges in the STN preceded or followed EMG activity of the limbs could not be precisely established under the present conditions.
  • Somatotopic representation in the STN is expected from normal and MTPT-treated monkeys. Indeed, somatotopy is enhanced int he GPm of MTPT-treated monkeys.
    • This somatotopy is likely to result from organized afferent from the primary motor cortex (M1) to dorsolateral STN; this is the target of DBS treatment. Ventral and medial STN seems to project to associative and limbic cortical regions.
    • It seems they think the STN is generally not diseased, it is just a useful target for stimulating without evoked movement as in M1. This is consistent with optogenetic studies by Deisseroth [1].
    • Supporting this: "DBS of STN in Parkinson's disease improves executive motor functions, but aggravates conditional associative learning.
  • Interesting: In Parkinson's disease patients with tremor, Levy and colleagues found synchronization and a high firing rate (>10Hz) while recording pairs of neurons >600um apart.
  • Recordings of cortical activity through EEG and STN LFP showed significant coherence in the beta and gamma frequency bands during movement - consistent with corticosubthalamic motor projection. ... and suggest that the STN neurons involved in parkinsonian tremor are the same as the ones ativated during the performance of a voluntary movement. (! -- I agree with this.)
  • More: The reciprocal inhibitory-excitatory connections tightly linking the GPe and the STN may generate self-perpetuating oscillations.

Old notes:

  • this paper concentrates on STN electrophysiology in PD.
    • has a rather excellent list of references.
  • found a somatotopic organization in the STN, with most motor-related units more irregular and in the dorsolateral STN.
  • found a substantial fraction of tremor-synchronized neurons.
  • conclude that the somatotopic organization is about the same as in monkeys (?) (!)
  • M1 projects to STN, as verified through anterograde tracing studies. [1] These neurons increase their firing rate in response to passive movements.
  • there appears to be a relatively-complete representation of the body in the dorsolateral STN.

____References____

[0] Rodriguez-Oroz MC, Rodriguez M, Guridi J, Mewes K, Chockkman V, Vitek J, DeLong MR, Obeso JA, The subthalamic nucleus in Parkinson's disease: somatotopic organization and physiological characteristics.Brain 124:Pt 9, 1777-90 (2001 Sep)
[1] Gradinaru V, Mogri M, Thompson KR, Henderson JM, Deisseroth K, Optical deconstruction of parkinsonian neural circuitry.Science 324:5925, 354-9 (2009 Apr 17)

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ref: Kelly-2007.01 tags: MEA single electrode comparison CMU Utah date: 01-05-2012 22:07 gmt revision:1 [0] [head]

PMID-17215384[0] Comparison of recordings from microelectrode arrays and single electrodes in the visual cortex.

  • We found that the array yields good recordings on a large number of electrodes, with qualities comparable to those from single electrode recordings. On average, the recording quality is somewhat lower than that of single electrodes, but nonetheless is sufficient for assessing tuning properties such as the spatiotemporal receptive field and orientation tuning.

____References____

[0] Kelly RC, Smith MA, Samonds JM, Kohn A, Bonds AB, Movshon JA, Lee TS, Comparison of recordings from microelectrode arrays and single electrodes in the visual cortex.J Neurosci 27:2, 261-4 (2007 Jan 10)

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ref: Olson-2005 tags: Arizona rats BMI motor control training SVM single-unit left right closed-loop learning Olson Arizona date: 01-03-2012 23:06 gmt revision:1 [0] [head]

bibtex:Olson-2005 Evidence of a mechanism of neural adaptation in the closed loop control of directions

  • from abstract:
    • Trained rats to press left/right paddles to center a LED. e.g. paddles were arrow keys, LED was the cursor, which had to be centered. Smart rats.
      • Experiment & data from Olson 2005
    • Then trained a SVM to discriminate left/right from 2-10 motor units.
    • Once closed-loop BMI was established, monitored changes in the firing properties of the recorded neurons, specifically wrt the continually(?) re-adapted decoding SVM.
    • "but expect that the patients who use the devices will adapt to the devices using single neuron modulation changes. " --v. interesting!
  • First page of article has an excellent review back to Fetz and Schmidt. e.g. {303}
  • Excellent review of history altogether.
    • Notable is their interpretation of Sanchez 2004 {259}, who showed that most of the significant modulations are from a small group of neurons, not the large (up to 320 electrodes) populations that were actually recorded. Carmena 2003 showed that the population as a whole tended to group tuning, although this was imperfectly controlled.
  • Also reviewed: Zacksenhouse 2007 {901}
  • SVM is particularly interesting as a decoding algorithm as it weights the input vectors in projecting onto a decision boundary; these weights are experimentally informative.
  • Figure 7: The brain seems to modulate individual firing rate changes to move away from the decision boundary, or at least to minimize overlap.
  • For non-overt movements, the distance from decision function was greater than for overt movements.
  • Rho ( ρ\rho ) is the Mann-Whitney test statistic, which non-parametrically estimates the difference between two distributions.
  • δf(X t)\delta f(X_t) is the gradient wrt the p input dimensions o9f the NAV, as defined with their gaussian kernel SVM.
  • They show (i guess) that changes in ρ\rho are correlated with the gradient -- e.g. the brain focuses on neurons that increase fidelity of control?
    • But how does the brain figure this out??
  • Not sure if i fully understand their argument / support.
  • Conclusion comes early in the paper
    • figure 5 weakly supports the single-neuron modulation result.

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ref: Carmena-2005.11 tags: carmena BMI nicolelis single-unit variability 2005 date: 01-01-2012 17:31 gmt revision:2 [1] [0] [head]

PMID-16291944[0] Stable ensemble performance with single-neuron variability during reaching movements in primates.

  • correlation between the firing of single neurons and movement parameters was nonstationary over 30-60 minute recording sessions.
  • yet! you could get stable prediction of arm movements, suggesting that movement parameters are redundantly encoded.
  • this, in turn, implies that you do not need a stable recorded population for good predictions.
  • suggest that the variance itself could be a means of neuronal 'computation' or exploration based on perturbations.
    • later Carmena papers do not mention this.

____References____

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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)