An extended difference of coherence test for comparing and combining several independent coherence estimates: theory and application to the study of motor units and physiological tremor

Amjad, A.M.; Halliday, David M.; Rosenberg, J.R.; Conway, B.A.

doi:10.1016/s0165-0270(96)02214-5

Cited by 272 publications

(251 citation statements)

References 15 publications

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“…These findings suggest that the presence of high-frequency coherence during injured walking is mediated by common descending drive to this pair of antagonist muscles. The presence of high-frequency coherence in moderately strong subjects fits with previous studies demonstrating that EEG/EMG coherence, which can be disrupted by TMS to the motor cortex (Hasan and Nielsen 2004), occurs at this higher-frequency band (Brown and Marsden 2001). In contrast, noninjured control subjects exhibited little to no high-frequency coherence between antagonist muscles during walking as reported previously (Halliday et al 2003;Hansen et al 2001).…”

Section: Coherence In Noninjured Controlssupporting

confidence: 89%

“…originate in the motor cortex and was not seen in individuals with complete lesions. Throughout the study, we used a 95% confidence interval to assess significance of the coherence (Amjad et al 1997) (see horizontal line in Fig. 1B).…”

Section: Coherence Analysismentioning

confidence: 99%

“…EMG/EMG coherence between muscle pairs also contains both higher-and lower-frequency bands (Grosse et al 2002). The higher-frequency coherence in EMG/EMG recordings is thought to originate from the cortex, whereas the lowerfrequency component is thought to arise subcortically (Brown and Marsden 2001;Farmer et al 1993). For example, in subjects with complete spinal cord lesions, EMG/EMG coherence is only found in the lower-frequency band (peaks in coherence at 10 and 16 Hz in individual subjects) (Norton et al 2003(Norton et al , 2004, suggesting that the lower band is spinal in origin.…”

Section: Introductionmentioning

confidence: 99%

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Changes in Cortically Related Intermuscular Coherence Accompanying Improvements in Locomotor Skills in Incomplete Spinal Cord Injury

Norton

Gorassini

2006

Journal of Neurophysiology

148

133

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. Changes in cortically related intermuscular coherence accompanying improvements in locomotor skills in incomplete spinal cord injury. J Neurophysiol 95: 2580 -2589, 2006. First published January 11, 2006 doi:10.1152/jn.01289.2005. In human spinal cord injury, the neuronal mechanisms mediating the improvement of locomotor function in response to intensive treadmill training are not well understood. In this study, we examined if such recovery is mediated, in part, by increases in residual corticospinal drive to muscles of the leg during walking. To do this, we measured the coherence of electromyogram (EMG) activity between two antagonist muscles (intermuscular coherence), specifically at frequencies between 24 and 40 Hz, which is thought to indicate common drive to two muscles from corticospinal inputs. In 12 subjects with incomplete spinal cord injury, intermuscular coherence was measured between hamstrings and vastus lateralis EMG that was activated during walking on a motorized treadmill. Before training, appreciable coherence in the 24 -40 Hz frequency band was only present in subjects with moderate volitional motor strength in their leg muscles (n ϭ 8 subjects) compared with subjects with little or no leg muscle strength (n ϭ 4 subjects), reconfirming that 24 -40 Hz frequency coherence is likely mediated by common supraspinal inputs. After training, increases in 24 -40 Hz coherence only occurred in the eight subjects with moderate leg muscle strength who also exhibited improvements in locomotor recovery as assessed by the 21 point WISCI II scale (termed responders). In contrast, development of intermuscular coherence in the 24 -40 Hz frequency band did not occur in the four subjects with absent or weak muscle strength. These subjects also did not improve in their locomotor ability as reflected in unchanging WISCI II scores (termed nonresponders). Lower-frequency coherence (5-18 Hz), which is thought to contain common drive from spinal inputs, did not change in either group. In a subset of subjects that were previously assessed with transcranial magnetic stimulation (TMS) before and after training (n ϭ 5 responders and 3 nonresponders), there was a significant and positive relationship between increases in 24 -40 Hz coherence and increases in evoked muscle responses to TMS of the primary motor cortex. Taken together, increases in higher-frequency EMG coherence in subjects with residual voluntary muscle strength and its parallel relation to changes in TMS-evoked responses provides further evidence that improvements in locomotor function from treadmill training are mediated, in part, by increases in corticospinal drive to muscles of the leg during walking.

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Section: Coherence In Noninjured Controlssupporting

confidence: 89%

Section: Coherence Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Changes in Cortically Related Intermuscular Coherence Accompanying Improvements in Locomotor Skills in Incomplete Spinal Cord Injury

Norton

Gorassini

2006

Journal of Neurophysiology

148

133

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“…After averaging, the magnitude-squared coherence was obtained. Averaging complex valued coherency across trials is equivalent to the 'pooled coherence' procedure described in (Amjad et al, 1997). In addition to the coherence spectra, the Fourier-based power spectra of EEG channels C3 and CP3 and the rectified EMG were estimated.…”

Section: Discussionmentioning

confidence: 99%

The reorganization of corticomuscular coherence during a transition between sensorimotor states

2014

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Recent research suggests that neural oscillations in di↵erent frequency bands support distinct and sometimes parallel processing streams in neural circuits. Studies of the neural dynamics of human motor control have primarily focused on oscillations in the beta band (15 30 Hz). During sustained muscle contractions, corticomuscular coherence is mainly present in the beta band, while coherence in the alpha (8 12 Hz) and gamma (30 80 Hz) bands has not been consistently found. Here we test the hypothesis that the frequency of corticomuscular coherence changes during transitions between sensorimotor states. Corticomuscular coherence was investigated in twelve participants making rapid transitions in force output between two targets. Corticomuscular coherence was present in the beta band during sustained contractions but vanished before movement onset, being replaced by transient synchronization in the alpha and gamma bands during dynamic force output. Analysis of the phase spectra suggested a time delay from muscle to cortex for alpha-band coherence, by contrast to a time delay from cortex to muscle for gamma-band coherence, indicating a↵erent and e↵erent corticospinal interactions respectively. Moreover, alpha and gamma -band coherence revealed distinct spatial topologies, suggesting di↵erent generative mechanisms. Coherence in the alpha and gamma bands was almost exclusively confined to trials showing a movement overshoot, suggesting a functional role related to error correction. We interpret the dual-band synchronization in the alpha and gamma bands as parallel streams of corticospinal processing involved in parsing prediction errors and generating new motor predictions.

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“…Coherence spectra for a random pair of mPFC neurons, a random pair of BLA neurons and one random unit in each of mPFC and BLA were generated from each animal. Individual coherence spectra were then combined across animals to give pooled coherence estimates that examine the functional coupling of unit activity within mPFC, within BLA, or between mPFC and BLA across the population of animals in each group (Amjad et al, 1997). LFP coherence spectra from each experiment were also combined across animals in the same manner.…”

Section: Coherence Analysismentioning

confidence: 99%

Systemic administration of the benzodiazepine receptor partial inverse agonist FG‐7142 disrupts corticolimbic network interactions

Stevenson

Halliday

Marsden

et al. 2007

Synapse

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The medial prefrontal cortex (mPFC) and basolateral amygdala (BLA) coordinate various stress responses. Although the effects of stressors on mPFC and BLA activity have been previously examined, it remains unclear to what extent stressors affect functional interactions between these regions. In vivo electrophysiology in the anesthetized rat was used to examine mPFC and BLA activity simultaneously in response to FG-7142, a benzodiazepine receptor partial inverse agonist that mimics various stress responses, in an attempt to model the effects of stressors on corticolimbic functional connectivity. Extracellular unit and local field potential (LFP) recordings, using multielectrode arrays positioned in mPFC and BLA, were conducted under basal conditions and in response to systemic FG-7142 administration. This drug increased mPFC and BLA unit firing at the lowest dose tested, whereas higher doses of FG-7142 decreased various burst firing parameters in both regions. Moreover, LFP power was attenuated at lower (<1 Hz) and potentiated at higher frequencies in mPFC (1-12 Hz) and BLA (4-8 Hz). Interestingly, FG-7142 diminished synchronized unit firing, both within and between mPFC and BLA. Finally, FG-7142 decreased LFP synchronization between these regions. In a separate group of animals, pretreatment with the selective benzodiazepine receptor antagonist flumazenil blocked the changes in burst firing, LFP power and synchronized activity induced by FG-7142, confirming direct benzodiazepine receptor-mediated effects. These results indicate that FG-7142 disrupts corticolimbic network interactions via benzodiazepine receptor partial inverse agonism. Perturbation of mPFC-BLA functional connectivity induced by FG-7142 may provide a useful model of corticolimbic dysfunction induced by stressors.

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An extended difference of coherence test for comparing and combining several independent coherence estimates: theory and application to the study of motor units and physiological tremor

Cited by 272 publications

References 15 publications

Changes in Cortically Related Intermuscular Coherence Accompanying Improvements in Locomotor Skills in Incomplete Spinal Cord Injury

Changes in Cortically Related Intermuscular Coherence Accompanying Improvements in Locomotor Skills in Incomplete Spinal Cord Injury

The reorganization of corticomuscular coherence during a transition between sensorimotor states

Systemic administration of the benzodiazepine receptor partial inverse agonist FG‐7142 disrupts corticolimbic network interactions

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