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ref: -2004 tags: neural synchrony binding robot date: 09-13-2020 02:00 gmt revision:0 [head]

PMID-15142952 Visual binding through reentrant connectivity and dynamic synchronization in a brain-based device

  • Controlled a robot with a complete (for the time) model of the occipital-inferotemporal visual pathway (V1 V2 V4 IT), auditory cortex, colliculus, 'value cortex'.
  • Synapses had a timing-dependent assoicative BCM learning rule
  • Robot had reflexes to orient toward preferred auditory stimuli
  • Subsequently, robot 'learned' to orient toward a preferred stimuli (e.g. one that caused orientation).
  • Visual stimuli were either diamonds or squares, either red or green.
    • Discrimination task could have been carried out by (it seems) one perceptron layer.
  • This was 16 years ago, and the results look quaint compared to the modern deep-learning revolution. That said, 'the binding problem' is imho still outstanding or at least interesting. Actual human perception is far more compositional than a deep CNN can support.

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ref: Litvak-2011.02 tags: DBS MEG STN synchrony oscillations london connectivity beta basal ganglia date: 02-29-2012 19:59 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-21147836[0] Resting oscillatory cortico-subthalamic connectivity in patients with Parkinson’s disease

  • Used MEG plus LFP recordings of the STN.
  • Two spatially and spectrally separated networks were identified.
    • A temporoparietal-brainstem network was coherent with the subthalamic nucleus in the alpha (7-13 Hz) band,
    • whilst a predominantly frontal network was coherent in the beta (15-35 Hz) band.
  • Dopaminergic medication modulated the resting beta network, by increasing beta coherence between the subthalamic region and prefrontal cortex.
  • Idea of characterizing connectivity based on synchronization / comodulation: (Fries 2005).
  • Synchronization is exaggerated in Parkinson's disease (Sharott et al 2005b, Mallet et al 2008).
  • Some patients had dopamine dysregulation syndrome and medication-induced hypersexuality.
  • None of the > 45 Hz STN LFP patterns had a scalp pattern consistent with a cortical source.
  • Cortical source frequency not really that different between ON and OFF medication, except at maybe tremor frequencies.
  • But cortex drives the subthalamic area robustly.
    • That said, these patients were at rest.
    • Small difference between ON and OFF states possibly because they were at rest.
  • Both healthy subjects and those with parkinson's disease show resting connectivity between basal ganglia and the SMA, temporopareital area and parts of the prefrontal cortex. (Postuma and Dagher 2006); Helmich et al 2010).
  • Beta band coupling between cerebral cortex and subthalamic nucleus drops before and during movement (Cassidy et al 2002 PMID-12023312; Lalo et al 2008)
    • During imagination of movement (Kuhn et al 2008).
    • During action observation (Alegre et al 2010).
      • Is this consistent with the conflict / reinforcement learning hypothesis?
  • A big problem is determining if the oscillations are pathological or non-pathological
    • Impossible to control, since we cannot record from healthy humans.

____References____

[0] Litvak V, Jha A, Eusebio A, Oostenveld R, Foltynie T, Limousin P, Zrinzo L, Hariz MI, Friston K, Brown P, Resting oscillatory cortico-subthalamic connectivity in patients with Parkinson's disease.Brain 134:Pt 2, 359-74 (2011 Feb)

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ref: Goldberg-2002.06 tags: DBS PD MPTP synchrony date: 02-22-2012 18:25 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-12040070[0] Enhanced synchrony among primary motor cortex neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine primate model of Parkinson's disease.

  • In the (MPTP) parkinsonian state, MI neurons discharged in long bursts (sometimes >2 sec long). These bursts were synchronized across many cells but failed to elicit detectable movement, indicating that even robust synchronous MI discharge need not result in movement.
    • These synchronized population bursts were absent from the GP and were on a larger timescale than oscillatory synchrony found in the GP of tremulous MPTP primates, suggesting that MI parkinsonian synchrony arises independently of basal ganglia dynamics.
  • Specificity of M1 neurons decreased to passive movement; GP showed no decrease in specificity.
    • Might be because of decreased specificity in the first place.
  • Again suggests that it's not rates but dynamics that underly pathophysiology.
  • Evarts 1965, Porter and Lemon 1993: the normal execution of voluntary movement is correlated with an increase in the synchronous discharge of primary motor cortex neurons.
  • No decrease in M1 activity w/ single unit discharge in M1 in MPTP monkeys & metabolic studies.
  • PD corresponds to a loss in specificity in the globus pallidus in response to passive joint manipulation (Filion et all 1988; Boraud et al 2000).
  • Nissl stain stains both neurons and glia (figure 2)
  • ISI plots (here called auto-associative index) markedly different before / after MPTP.
  • M1 can commonly be micro-excited with as little as 5ua (Murthy and Fetz, 1996; Tokuno and Nambu 2000).
  • Temporal width of pathological synchornization on the order of tens to hundreds of milliseconds.
  • Hypothesize loss of functional segregation along parallel corticobasal ganglia circuits (Alexander et al 1986, DeLong 1990)

____References____

[0] Goldberg JA, Boraud T, Maraton S, Haber SN, Vaadia E, Bergman H, Enhanced synchrony among primary motor cortex neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine primate model of Parkinson's disease.J Neurosci 22:11, 4639-53 (2002 Jun 1)

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ref: Heimer-2006.01 tags: STN DBS synchrony basal ganglia reinforcement learning beta date: 02-22-2012 17:07 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-17017503[0] Synchronizing activity of basal ganglia and pathophysiology of Parkinson's disease.

  • They worry that increased synchrony may be an epi-phenomena of tremor or independent oscillations with similar frequency.
  • Modeling using actor/critic models of the BG.
  • Dopamine depletion, as in PD, resultis in correlated pallidal activity, and reduced information capacity.
  • Other studies have found that DBS desynchronizes activity -- [1] or [2].
  • Biochemical and metabolic studies show that GPe activity does not change in Parkinsonism.
  • Pallidal neurons in normal monkeys do not show correlated discharge (Raz et al 2000, Bar-Gad et al 2003a).
  • Reinforcement driven dimensionality reduction (RDDR) (Bar-Gad et al 2003b).
  • DA activity, through action on D1 and D2 receptors on the 2 different types of MSN, affects the temporal difference learning scheme in which DA represents the difference between expectation and reality.
    • These neurons have a static 5-10 Hz firing rate, which can be modulated up or down. (Morris et al 2004).
  • "The model suggests that the chronic dopamine depletion in the striatum of PD patients is perceived as encoding a continuous state where reality is worse than predictions." Interesting theory.
    • Alternately, abnormal DA replacement leads to random organization of the cortico-striatal network, eventually leading to dyskinesia.
  • Recent human studies have found oscillatory neuronal correlation only in tremulous patients and raised the hypothesis that increased neuronal synchronization in parkinsonism is an epi-phenomenon of the tremor of independent oscillators with the same frequency (Levy et al 2000).
    • Hum. might be.
  • In rhesus and green monkey PD models, a major fraction of the primate pallidal cells develop both oscillatory and non-oscillatory pair-wise correlation
  • Our theoretical analysis of coherence functions revealed that small changes between oscillation frequencies results in non-significant coherence in recording sessions longer than 10 minutes.
  • Their theory: current DBS methods overcome this probably by imposing a null spatio-temporal firing in the basal ganglia enabling the thalamo-cortical circuits to ignore and compensate for the problematic BG".

____References____

[0] Heimer G, Rivlin M, Israel Z, Bergman H, Synchronizing activity of basal ganglia and pathophysiology of Parkinson's disease.J Neural Transm Suppl no Volume :70, 17-20 (2006)
[1] Kühn AA, Williams D, Kupsch A, Limousin P, Hariz M, Schneider GH, Yarrow K, Brown P, Event-related beta desynchronization in human subthalamic nucleus correlates with motor performance.Brain 127:Pt 4, 735-46 (2004 Apr)
[2] Goldberg JA, Boraud T, Maraton S, Haber SN, Vaadia E, Bergman H, Enhanced synchrony among primary motor cortex neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine primate model of Parkinson's disease.J Neurosci 22:11, 4639-53 (2002 Jun 1)

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ref: work-2999 tags: autocorrelation poisson process test neural data ISI synchrony DBS date: 02-16-2012 17:53 gmt revision:5 [4] [3] [2] [1] [0] [head]

I recently wrote a matlab script to measure & plot the autocorrelation of a spike train; to test it, I generated a series of timestamps from a homogeneous Poisson process:

function [x, isi]= homopoisson(length, rate)
% function [x, isi]= homopoisson(length, rate)
% generate an instance of a poisson point process, unbinned.
% length in seconds, rate in spikes/sec. 
% x is the timestamps, isi is the intervals between them.

num = length * rate * 3; 
isi = -(1/rate).*log(1-rand(num, 1)); 
x = cumsum(isi); 
%%find the x that is greater than length. 
index = find(x > length); 
x = x(1:index(1,1)-1, 1); 
isi = isi(1:index(1,1)-1, 1); 

The autocorrelation of a Poisson process is, as it should be, flat:

Above:

  • Red lines are the autocorrelations estimated from shuffled timestamps (e.g. measure the ISIs - interspike intervals - shuffle these, and take the cumsum to generate a new series of timestamps). Hence, red lines are a type of control.
  • Blue lines are the autocorrelations estimated from segments of the full timestamp series. They are used to how stable the autocorrelation is over the recording
  • Black line is the actual autocorrelation estimated from the full timestamp series.

The problem with my recordings is that there is generally high long-range correlation, correlation which is destroyed by shuffling.

Above is a plot of 1/isi for a noise channel with very high mean 'firing rate' (> 100Hz) in blue. Behind it, in red, is 1/shuffled isi. Noise and changes in the experimental setup (bad!) make the channel very non-stationary.

Above is the autocorrelation plotted in the same way as figure 1. Normally, the firing rate is binned at 100Hz and high-pass filtered at 0.005hz so that long-range correlation is removed, but I turned this off for the plot. Note that the suffled data has a number of different offsets, primarily due to differing long-range correlations / nonstationarities.

Same plot as figure 3, with highpass filtering turned on. Shuffled data still has far more local correlation - why?

The answer seems to be in the relation between individual isis. Shuffling isi order obviuosly does not destroy the distribution of isi, but it does destroy the ordering or pair-wise correlation between isi(n) and isi(n+1). To check this, I plotted these two distributions:

-- Original log(isi(n)) vs. log(isi(n+1)

-- Shuffled log(isi_shuf(n)) vs. log(isi_shuf(n+1)

-- Close-up of log(isi(n)) vs. log(isi(n+1) using alpha-blending for a channel that seems heavily corrupted with electro-cauterizer noise.

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ref: KA/4hn-2009.02 tags: DBS synchrony STN PD bradykinesia rigidity berlin oxford beta date: 01-25-2012 03:47 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-19070616[0] Pathological synchronisation in the subthalamic nucleus of patients with Parkinson's disease relates to both bradykinesia and rigidity.

  • Synchronization prominent in PD 8-35 Hz, (Engel et al., 2005; Schnitzler and Gross, 2005; Uhlhaas and Singer, 2006; Hammond et al., 2007).
  • levodopa treatment suppressed LFP activity in the STN at 8 - 35 Hz.
  • Data suggests that levodopa-induced improvements in both rigidity and bradykinesia scale with the degree of suppression of oscillatory power in the STN LFP.
    • This is irrespective of the frequency that synchronization occurs.
    • consistent with the hypothesis that excessive synchronization in the cortico-BG system limits information coding capacity, as this would be the case irrespective of frequency.
  • In the MPTP primate, synchronization tends to occur at frequencies below 15 Hz. (Galvan and Wichmann, 2008).
  • Synchonization at higher frequencies (> 40 Hz) was associated with better motor improvement (Kuhn et al 2006)
    • Enchanced movement-induced gamma activity occurs with levodopa treatment (Androulidakis et al 2007).
  • Contrary to an early report (Levt et al 2000), there was relatively little evidence for an associateion between LFP activity in the beta band and rest tremor (Amiroving et al 2004, Kuhn et al 2006, Ray et al 2008, Weinberger et al 2006).
    • This does not refute an association between rest tremor and oscillatory frequencies below 8 Hz. CF EMG studies.
  • LFS at 10-20 Hz to the STN exacerbates Parkinson's disease, though this is somewhat unqualified (Timmerman et al 2004; Chen et al 2007; Eusebio et al 2007).
    • In some patients there was an increase in LFP energy in the ON state vs the OFF state at higher frequency.

____References____

[0] Kühn AA, Tsui A, Aziz T, Ray N, Brücke C, Kupsch A, Schneider GH, Brown P, Pathological synchronisation in the subthalamic nucleus of patients with Parkinson's disease relates to both bradykinesia and rigidity.Exp Neurol 215:2, 380-7 (2009 Feb)

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ref: Levy-2002.04 tags: DBS oscillations synchrony date: 01-19-2012 21:00 gmt revision:1 [0] [head]

PMID-11923450[0] Synchronized neuronal discharge in the basal ganglia of parkinsonian patients is limited to oscillatory activity.

  • simultaneous recording for pallidotomy or STN DBS.
  • In the five pallidotomy patients without limb tremor during the procedure, none of the 73 GPi pairs and 15 GPe pairs displayed synchronous activity. we got the same result
  • In the three pallidotomy patients with limb tremor, 6 of 21 GPi pairs and 5 of 29 GPe pairs displayed oscillatory synchronization in the frequency range of the ongoing limb tremor (3-6 Hz) or at higher frequencies (15-30 Hz).
  • Synchronized activity was not observed in the SNr (10 pairs).

____References____

[0] Levy R, Hutchison WD, Lozano AM, Dostrovsky JO, Synchronized neuronal discharge in the basal ganglia of parkinsonian patients is limited to oscillatory activity.J Neurosci 22:7, 2855-61 (2002 Apr 1)

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ref: Wyler-1985.08 tags: Wyler synchrony operant conditioning BMI date: 12-06-2011 06:36 gmt revision:1 [0] [head]

PMID-4041789 Synchrony between cortical neurons during operant conditioning.

  • Fetz and Baker showed that individual neurons recorded from the same electrode can modulate their firing upon operant conditioning either together, opposite, or independently.
  • Wyler has duplicated this result, and undertakes this further analysis to show that these pairs of neurons recorded from the same electrode show high degrees (67%) of tight 1ms synchrony.
  • This despite the fact that in 80% of cases the firing rates did not covary.
  • This suggests that they must have a common synaptic pathway.
  • Reference (and support) Lemon and Porter's finding that adjacent neurons respond to widely separated peripheral fields.

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ref: MAPlle-2009.03 tags: sleep spindles learning ripples LFP hippocampus neocortex synchrony SWS REM date: 03-25-2009 15:05 gmt revision:2 [1] [0] [head]

PMID-19245368[0] The influence of learning on sleep slow oscillations and associated spindles and ripples in humans and rats

  • Here we examined whether slow oscillations also group learning-induced increases in spindle and ripple activity, thereby providing time-frames of facilitated hippocampus-to-neocortical information transfer underlying the conversion of temporary into long-term memories.
  • No apparent grouping effect between slow oscillations and learning-induced spindles and ripples in rats.
  • Stronger effect of learning on spindles (neocortex) and ripples (hippocampus) ; less or little effect of learning on slow waves in the neocortex.
  • have a good plot showing their time-series analysis:

____References____

[0] Mölle M, Eschenko O, Gais S, Sara SJ, Born J, The influence of learning on sleep slow oscillations and associated spindles and ripples in humans and rats.Eur J Neurosci 29:5, 1071-81 (2009 Mar)

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ref: Eusebio-2009.05 tags: DBS STN beta gamma oscillations synchrony tremor review date: 03-23-2009 18:32 gmt revision:1 [0] [head]

PMID-19233172[0] Synchronisation in the beta frequency-band - The bad boy of parkinsonism or an innocent bystander?

  • Excessive synchronisation of basal ganglia neuronal activity in the beta frequency band has been implicated in Parkinson's disease
  • However, the extent to which beta synchrony has a mechanistic (rather than epiphenomenal) role in parkinsonism remains unclear, and the suppression of this activity by deep brain stimulation is contentious.
PMID-16289053[1] Intra-operative STN DBS attenuates the prominent beta rhythm in the STN in Parkinson's disease.
  • Beta rhythm for them = 11-30Hz. Observed in the LFP recorded from the DBS electrode itself.
  • This study shows for the first time that STN DBS attenuates the power in the prominent beta band recorded in the STN of patients with PD.

____References____

[0] Eusebio A, Brown P, Synchronisation in the beta frequency-band - The bad boy of parkinsonism or an innocent bystander?Exp Neurol no Volume no Issue no Pages (2009 Feb 20)
[1] Wingeier B, Tcheng T, Koop MM, Hill BC, Heit G, Bronte-Stewart HM, Intra-operative STN DBS attenuates the prominent beta rhythm in the STN in Parkinson's disease.Exp Neurol 197:1, 244-51 (2006 Jan)