Monday, January 24, 2011

Basics neuronal dynamics

Delta 0-1 Hz: neocortical, and thalamo-cortical networks.  Large-scale cortical integration.

Theta: subcortical and thalamo-cortical source, involved in a variety of cognitive functions (Hipo theta).

Alpha 8 - 13 Hz: amplitude is related to the level of cortical activation, strong alpha associated with coritcal & behavioural deactivation or inhibition; otherwise (1) highly specific perceptual, attentional, and memory processes.

cortically generated (Gross 2004 reported a large scale beta too), b/c of local strictness.  Mainly associated with motor, ERD before/during movement, rebound after the movement stopped.
Attention and higher cognitive functions.

cortically generated too (from intrinsic membrane properties of interneurons or from neocortical exitatory-inhibitory circuits)
* binding
* more recent --> human gamma frequency were reported for encoding, retention and retrieval of info independent of sensory modality.
Problem: small amplitude, similarity to muscle activity leaks into the sensors.

During cognitive efforts: * delta, theta, gamma ERS (pp. 3)
During cognitive processing: * alpha, beta ERD

Super-fast processes (a few ms level), i.e. Buzsaki and Draguhn, 2004; Dragoi and Buzsaki, 2006; Siapas et al., 2005

Varela et al., 2001 review on Phase synchronization

Phase synchronization

(1) Phase coupling over distance (phase-coherence)
(Nunez et al., 1997, 1999; or Rappelsberger, 1998)
  • pp 5, widespread coherence in gamma& alpha bands in conscious perception vs unpercepted stim (Rodriguez et al., 1999; Klopp et al., 2000; Mima et al., 2001).
  • pp 7,  (Sauseng et al., 2007a) midline theta, increased with task-demand (power diff independent of novelty), in line with literature on sustained attention, localized into ACC, cingulate motor area.   But long range fronto-parietal theta phase coherence was stronger in the novel condition.

(2) Phase synchronization acrossing different frequency (bi-coherence)
  • Network of diff size are supposed to oscillate at diff speed
  • High temporal preciseness of synch btw oscillations of diff freq can potentially explain how info btw mem sys can be exchanged in cortex。
    • instantaneous phase of a slower oscillation modulates the amplitude of a higher freq (Lakatos et al., 2005). delta --> theta, theta --> gamma, hierarchical organization.
    • in humans, theta --> gamma (Mormann et al., 2005; Demiralp et al., 2007a,b; Canolty et al., 2006).
    • theta --> alpha interact in combined working and long-term memo (Sauseng et al., 2002, theta from anterior to posterior during memo retrieval attempts. When visual items retrieved, the direction of theta reversed. At this theta reversal, upper alpha power decrease -- indicating successful retrieval)
    • Methods: Cross-freq phase synchronization (bi-coherence) - Schack: momory-load dependent increase of pase coupling btw prefrontal theta and posterior alpha.  Interpretation: prefrontal theta -> executive processes of working-memo, posterior alpha --> reactivated long-term memo traces (Ruchkin 2003) - thus, working and long-term memo interfacing (Schack 2005)
    • Sauseng (2008) theta-gamma coherence in pareital modulated by short-term memory load

(3) Phase-locking after stim presentation

  • Look up: 
    • Basar, E., 1999a. Brain Function and Oscillations I: Principles and Approaches. Springer, Berlin.
    • Basar, E., 1999b. Brain Functions and Oscillations, II: Integrative Brain Functions.Springer, Berlin.
  • pp 9, there are still ongoing debates over phase resetting or the classical evoked model, and Sauseng (2007b) these two cannot be dessociated <-- should take a look at this paper
  • Pase-locking index, Gruber 2005, Schack & Klimesch 2002

Event-related changes

Journal club presentation 1

Pfurtscheller Handbook page 7
(1) Evoked response: time-locked & Phase-locked, which could be found from simple averaging. It's the response of a stationary system to the external stimulus.
(2) Induced response: time-locked but NOT phase-locked, can only be extracted through non-linear methods (e.g. envelope detection or power spectral analysis). It could be understood as a change in the ongoing activity, resulting from the changes in the functional connectivity within the cortex.Various factors: may depend on modulating influence arising from neurochemical brain systems, on changes in the strength of synaptic interactions or on changes affecting the intrinsic membrane properties of local neurons.

functional meaning, Pfurtcheller handbook chapter 
Pfurtscheller's ERD during visual processing
Pfurtscheller's basic principles on ERD/ERS ◄═ important paper

Thomas F. Collura 
President of the International Society for Neurofeedback and Research (ISNR).
lecture: Foundations of Neuronal Dynamics & Z Scores 

100ms perception
200ms awareness
300ms differentiate
400ms detection

signal 60-70 ms reaches thalamus, then 100 to occipital, visual alpha: 10 Hz when resting or there is no visual stimulus

delta: 1-4 Hz

Theta: 4-7 Hz

alpha: 7 -15 Hz
high alpha or low beta SMR in SMC: 14 Hz, a very healthy, vigilant state, no body movement (physical relaxation), in SMC typical thalamo-cortical speed is 80 ms in resting, faster than the visual system.  (part 11 in the talk)

beta: 15 - 20 Hz more localized (memory recall), wax and wane, sinusoidal

high beta: 20 - 30 ms, thinking, intensive thinking, worrying, math, wax and waning

gamma: 40 Hz and above
*indicate sensory binding, perceptual binding (association)  high gamma synchrony in meditation experts, and clairvoyant subjects.  R. Davidson lab. 
* Gamma nested in theta



  1. Do you cite any of Collura's papers in your introduction?

  2. This is a very good intro to ERP and the meaning of different bands. I don't think I will cite any of his papers.
    But Pfurtscheller's 1994 1999 paper will be cited.

  3. Link to Pfurtscheller's papers added ↑