Presentation on theme: "Timing of Neural Events"— Presentation transcript:
1Timing of Neural Events Implications for Consciousness and BindingBy Jay Gunkelman, QEEG-DiplomateSBCGlobal.net
2Mind-Brain-Consciousness Any respectable Model must explain memory (both semantic and episodic), as well as “intention”, “attention”, Perception, “awareness”, “discrimination”, and “conscious awareness”, and predict whether a brain is conscious or not... Objectively... and show a method of binding spatially divergent areas of brain function into instantly functioning interlaced neural networks... On both hemispheres.The Model must use modern neuroscience, but be classically based and be generally understandable by the non-specialist (a criteria set by Wilder Penfield’s Mystery of the Mind).
3MemoryMemory Storage is holonomic, and stored as a distributed Gabor function (K. Pribram)Semantic memory is enhanced by increased higher frequency (11-13 Hz) thlamo-cortical alpha content (environmental samples per second) which is seen tonically in on-going spindles.Episodic memory is associated with a septo-hippocampal theta rhythm (Frontal Midline Theta; FMT), which is seen phasically, in brief bursts.
4For our “memory” to work, we need to have a relationship between our short term episodic memory and our long term memory. For detailed reference to EEG and memory, please see Klimesch’s work on theta, alpha and memory.ERP morphology can be created by an instantaneous phase lock of alpha and theta rhythms (Klimesch, 2004).This time-series represents the interaction between the limbic system’s phasic theta of the episodic memory system and the thalamo-cortical system’s semantic memory system, associated with high frequency alpha components.A mechanism for phase locking (synchronizing) of the EEG needs to be identified...
5BINDINGWe have a complex set of brain functional modules, and for us to be functional, we need to have areas work together for one task, and NOT to work together on others.... For example, when a verbal stimuli is given, and it has a semantic unexpected difference, frontal lobe areas evaluating the oddball semantic content engage, while perceptual inputs are attenuated parietally... Binding “in” and blocking “out” neural networks... See the ERPs:
6ERP’s spatio-temporal domain: An “unexpected semantic difference” elicits changes with a 400 milliseconds latency (D.Tucker, 1994)
7DC field gradients of 100-200 uV/mm are seen in animals. Implications of timing on candidates for “Binding’s” mechanism.Phase-locked gamma has been detected as early as 45 milliseconds in a cognitive task (Gurtubay et al, 2004) ... A bit late to be the binding agent creating the network for processing the data.DC fields can mediate neuronal synchronization on a time scale of one millisecond (E.R. John, 2005)Mediation of the EEG’s synchrony by the DC field requires a field gradient on the order of 100 uV/mm (Weaver, 1998).DC field gradients of uV/mm are seen in animals.(Caton, R., 1875).
8Perception is not continuous, but parsed into discrete packets by thalamic gating, with sensory stimuli enhanced in the negative phase and diminished in the positive phase of the alpha wave, making 10 Hz alpha actually function as 10 samples per second of the environment, with a 100 millisecond snapshot “frame”.A “perceptual frame”, which is from 75 to 100 ms. (Efron, 1970) is temporally quite similar to a “Micro-State” , which is 82 (+/- 4) ms (D. Lehmann, et al., 2004).The earliest components of ERPs correspond to perceptual signal detection. The N1 occurs at ms (thalamic arrival), and P1 at about 100 ms (perceptual cortical arrival).Initial sensory processing within the sensory association cortex is noted from 90 to 130 ms.
9The P2 is seen at about 200 milliseconds, and correlates with sensory “awareness”, but not full consciousness.Stimulus detections posteriorly are projected to prefrontal and parietal areas from 130 to 280 ms (Halgren, et al., Cerebral Cortex 2002).Phase-locked gamma activity appears between the parietal and prefrontal cortex at approximately ms in a cognitive task (Varela, 2000).Posterior temporal phase-locked gamma is seen at approximately 200 ms (Gurtubay, et al, 2004).
10The P-300 has two components: The P3A is seen frontally at ms, and the P3B appears parietally at ms. There is phase-locked gamma from ms, found only after the target stimuli (Gurtubay, et al., 2004).The N400 is associated with “unexpected semantic representation” (D. Tucker, 1994). The N450 is associated with semantic encoding (Hillyard & Mangun, 1987).The return of late evoked potential components is predictive of recovery from coma (Alter, John, & Ransohoff, 1990), as are the presence of “spindles” in coma... though many other EEG patterns in coma are either non-specific or offer poor prognosis.An ERP can be conceptualized as an approximation of one cycle of the construction of a “frame” of consciousness.
11Shifting attention volitionally shifts the ERP’s cortical distribution
12How many ERP cycles does it take to be conscious?? When the second element of a pair of sensory stimuli differs, an enhancement of the amplitude of the ERP takes place. This DC potential difference is considered a measurement of attention, and is referred to as “mismatch-negativity” (MMN).
14ERPs in normal and ADHD children in GO/NOGO task Amplitude of NOGO-GO difference wave is higher in normal children and depends of task performance in ADHD children (12-14 years old).The location of positive and negative picks in the difference wave remains the same for normal and ADHD children.Kropotov et al., in preparation
15The MMN data shows that in a conscious person, the recent past is continuously compared with the present, thus suggesting that consciousness is the remembered present. (Edelman (2001)An “echoic memory trace” serially compares events to a representation of the previous event (Naatanen, 2004). This has a duration of approximately 10 seconds, and is processed in the dorsolateral prefrontal cortex. (E.R. John, 2005).The implication is that consciousness requires two ERP “perceptual cycles”: one to perceive, and another to compare to the recalled present.
16Conscious awareness of an event is delayed about 500 ms, but this awareness is referred backward to the ‘event-stream’ onset (Libet 1979).This leaves us with the problem of “Binding”, and the implications of these observations of neural timing on the mechanisms capable of binding a spatially diverse neural network... “instantly”The only system fast enough for spatially distant neural network “phase binding” is the millisecond time frame of the DC field, not Gamma. (Gunkelman, 2004)
17Initiated by the DC field’s millisecond time domain synchronization effect, we see a bispectral relationship between Gamma and DC Field activity in the EEG... during consciousness.
18Gamma back-propagation and network phase locking ‘resonance’ is generated after a network is bound (John, 2005). (emphasis mine)The resonant DC fields and phase locked EEG rhythms yield consciousness, from within their “nested rhythms”.Nesting of frequencies constitutes a quantum effect observed in the EEG (J. Pop-Jordanov, 2004).
20Model summary:Consciousness is an emergent property, spawned from of the interaction betweenDC fields, in the realm of the mind, and2) EEG rhythms, in the realm of the brain...When mind and brain interact, with quantum nesting of rhythms... consciousness emerges.Consciousness is not alchemy... It is based solidly in modern neuroscience!
21Decrease of beta and Gamma synchrony in ADHD Normal is compared with ADHD, divided into high and low performance subgroups.“Go” stimuli elicited activity in beta (14-18 Hz) band.The degree and latency of beta synchronization varied with performance.The Gamma differences are apparent, with less gamma content associated with performance decreasesNote the modulated 6 Hz ‘nesting’ of Gamma in normal conscious functionData from J.Kropotov, 2000
22Bispectral data showing a locked neural network in parkinsonism
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25Timing of Neural Events Implications for Consciousness and BindingPresented by:Jay Gunkelman, QEEG-DiplomateSBCGlobal.net