The Brain Clock:

An Overview of Contemporary Research & Theory Regarding the Neuroscience of Brain-based Interval Timing & Its Relevance to Learning & Rehabilitation

Kevin McGrew, Ph.D.(aka, the “Time Doc”)

Institute for Applied Psychometrics LLC

(www.iapsych.com)

This presentation is based on some VERY broad stroke conclusions and interpretations drawn from reviewing some very technical and complex research across a large number of disciplines

e.g.……………………

There is MUCH more to this research

Check out “IQ BrainClock EWOK” for specifics

Goal of this presentation

To “connect-the-dots” across a diverse array of theoretical and empirical fields of study to advance possible explanations/hypotheses of the SMT/IM effect

Status of Mental Timing Research:Historical Note

In his chapter “The Problem of Serial Order in Behavior,” Karl Lashley (1951) was among the first neurophysiologists to broach the issue of temporal processing.

Temporal integration is not found exclusively in language; the coordination of leg movements in insects, the song of birds, the control of trotting and pacing in a gaited horse, the rat running the maze, the architect designing a house, and the carpenter sawing a board present a problem of sequences of action which cannot be explained in terms of succession of external stimuli.

(Mauk & Buonomano, 2004)

“We know the human brain contains some kind of clock, but determining its neural underpinnings and teasing apart its components have proven difficult.”

(Lewis & Walsh, 2005)

Time and space are the fundamental dimensions of our life/existence

We believe timing is the foundation for learning and memory,

It's hard to find any complex behavioral process that timing isn't involved in

To deal with time, organisms have developed multiple systems that are active over more than 10-12 orders of magnitude with various degrees of precision (see figure)

Duke Researcher’s Meck & Buhusi (2005)

Mental Timing Research: Importance

Mental Timing Research: Importance

Many actions (motor) manifest precise timing

(Zelaznik et al., 2005)

•The musicians in an orchestra time their movements to the gestures of the conductor

•The drag racer uses the countdown lights to anticipate the start of a race

•A pitcher must temporally coordinate muscular activity across different joints to ensure that the ball is delivered to a targeted region of the strike zone

Mental Timing Research:Has been implicated as important in human

learning and understanding a variety of clinical disorders. Examples include:

•Parkinson’s

•Huntington’s

•Schizophrenia

•ADHD

•Reading development and disorders (dyslexia/reading disabilities)

•Speech and language development and related disorders•Analogy – auditory processing of Morse code

•Musical abilities and performance

•Motor timing disorders

•Aspergers???

(See IQ BrainClock EWOKfor research)

Research suggests common dopamine link (e.g., dopaminergic disorders)

Mental Timing Research: Modifiability

Can the internal clock be “speeded up”

YES ! - (see review of Mauk & Buonomano, 2004; Droit-Volet, 2002; Penton-Voak, 1996; Weardon, 2005)

•“The neural mechanisms underlying timing can be fine-tuned with experience”

Select list of approaches

•Physical - drugs, changing body temperature•Environmental – repetitive streams of stimulation (clicks or flashes - flicker) prior to stimuli – to increase “arousal”

•SMT/IM ?????

Research has indicated that it is also possible to “slow down” the internal clock (Weardon, in press, 2007)

The study of the neural basis of temporal processing is in its infancy (Mauk & Buonomano, 2004)

Our timing abilities are impressive, diverse and worthy of investigation. But they are not very well understood. (Lewis, 2005)

In comparison with spatial stimuli, there is a significant gap in our understanding of how the brain discriminates simple temporal stimuli (Karmarkar & Buonomano, 2007)

Mental Timing Research: Caveats

Important developments since speaking to you last……

IQ Brain Clock Blog (www.ticktockbraintalk.blogspot.com

)

IQ Brain Clock EWOK(access via IQ Brain Clock Blog)

“Time Doc”

Timescales of temporal

processing

(Mauk & Buonomano, 2004)

Humans processtemporal information over scales of at least 10-12 orders of magnitude that have been categorized into 3-4 major timescale groups

Timing across different timescales (compilation of data from various human and animal studies – Buhusi & Meck, 2005)

Importance of interval timing (Buhusi & Meck,

2005)

SMT (IM) would be operating primarily at millisecond/interval

timing levels

Temporal processing -- the decoding of temporal information or the generation of timed motor responses.

Temporal processing: A definition(Mauk & Buonomano, 2004)

This is potentially “the” core construct and theoretical/research domain around which I believe the the “brain clock” and SMT (IM) research should be examined

The Time Doc concludes

Temporal processing: A definition(Mauk & Buonomano, 2004)

Temporal information/pattern from environment (e.g., music) --- generates action potentials that follow a beat (information is encoded in temporal domain)

(Note - If internal temporal codes are generated by the brain, they must be decoded or processed, like the external temporal patterns presented here.)

Action potential patterns must be decoded in order to decide whether the stimulus was played at a fast or slow tempo—or to generate a timed motor response

(spike patterns “encode”temporal information)

Automatic timing system

•Works in the millisecond range•Discrete-event (discontinuous) timing, esp. movement/motor tasks•Involves the cerebellum

Cognitively-controlled timing system

•Continuous-event timing•Requires attention and involvement of working memory•Involves the basal ganglia and related cortical structures

It is the “constellation of task characteristics that dictate which timing “circuits” of brain “systems”are invoked in a particular task performance (Lewis & Miall, 2006)

Two primary mental timing circuits

(Buhusi & Meck, 2005; Lewis & Miall, 2006)

I hypothesize that SMT interventions (e.g, IM) tap both the automatic and controlled cognitive timing systems (and related neurological structures and functions). SMT-based interventions typically involve a motor component (e.g., clapping hands together to the beat) and requires responding in terms of milliseconds. These characteristics would be associated with the automatic timing system.

However, although an individual (during SMT training) is trying to synchronze their tapping in terms of milliseconds, the duration between the continuous tones is more in the range of a second or so. Also, during initial stages of SMT, an individual's working memory is particularly taxed as one monitors the SMT visual and/or auditory feedback provided, makes a decision about whether they are responding "too fast" or "too slow", and then cognitively implements a correction to their "beat" behavior. These later characteristics are more characteristic of the cognitively controlled timing system.

So...it is my hypothesis that both the automatic and cognitively controlled timing systems of mental or interval time-keeping are involved with SMT-based interventions. It is possible that both are significantly active during early stages of SMT training and, with improvement and progress over time, the role of the cognitively controlled system decreases and the automatic system is more responsible.

The Time Doc speculates 11-4-06

SMT-based interventions (e.g., IM) may be operating on the cognitive and neurological mechanisms that underlie brain-based temporal processing. That is, SMT interventions may help facilitate the “fine-tuning” of the temporal resolution of the interal brain clock.

The Time Doc speculates 9-4-07

A domain-generalcognitive mechanism?

A number of domain (subject)-specific cognitive mechanisms?

OR….

A domain-general

cognitive mechanism?

•There is a long-standing tradition within psychological research to search for general principles or cognitive mechanisms that can be used to address all aspects of behavior and cognition.

•Not tied to any specific content or domain.

•An underlying mechanism that can be applied to a wide range of novel problems and domains of performance

•“Jack-of-all-trades” mechanisms (Chiappe & McDonald,2005)

•These are the mechanisms that may be captured by the notion of “g” (general intelligence), and include such cognitive mechanisms as executive function and working memory (Chiappe & McDonald, 2005) and a master internal mental clock (Buhusi & Meck, 2005)

• Searching for the “essence” of g has been the holy grail In intelligence research

•g is a domain general mechanism as it is not specific to any particular domain of knowledge or mental skill and appears to be independent of cultural context (Gottfrredson, 1998)

•Biological correlates of g include brain size, speed of nerve conduction, energy qualities of brain waves, etc.

•Research has suggested that people differ in g due to some form of differences in speed/efficiency (resolution) of neural processing (neural efficiency/oscillation hypothesis)

•Speed of information processing•Efficiency of the CNS

g (general intelligence)

•Most prominent paradigm for investigating g has been the use of elementary cognitive tasks (ECTs) (see Jensen)

•Reaction time (RT) measures (Hick paradigm; Hicks law)

•Decision time (DT)•Movement time (MT)•Metric is in milliseconds•No obvious intellectual content

•RT measures are believed to measure the speed with which the brain apprehends, integrates and evaluates information – speed of neural oscillations (Gottfredson, 1998; Hunt, 1999; Jensen, 1998a; Sternberg & Kaufman, 1998).

•Search continues for the underlying biological determinants

g (general intelligence)

g (general intelligence): Temporally based?

Rammsayer, T. & Brandler, S. (2007). Performance on temporal information processing as an index of general intelligence. Intelligence, 35, 127-139)

Important (seminal?) article that links mental clock, g-based

cognitive/IQ, and SMT/IM research ?

•Analyses suggested a unitary timing mechanism, referred to as temporal g.

•Performance on temporal information processing provided a more valid predictor of psychometric g than traditional reaction time measures

• r (with psychometric g) = .56 (temporal g) vs .34 (reaction time g)

•Findings suggest that temporal resolution capacity of the brain (as assessed with psychophysical temporal tasks) reflects aspects of neural efficiency associated with general intelligence.

Rammsayer & Brandler (2007)

Temporal g ?

•The notion of an internal master clock represents an alternative metaphor to account for the relationship between efficiency and speed of information processing and psychometric g. (Rammsayer & Brandler, 2006, in press)

•The concept of a hypothetical master clock has been introduced by Surwillo (1968).

•Proposed an internal clock mechanism in the central nervous system for coordination of different neural activities.

•Burle and Bonnet (1997, 1999) provided additional converging experimental evidence for the existence of some kind of master clock in the human information processing

Temporal g ?

•Temporal information processing models (Creelman, 1962; Gibbon, 1991; Rammsayer & Ulrich, 2001; Treisman et al., 1990; see Grondin, 2001 for review) are based on the central assumption of neural oscilliations (note – same central feature of Jensen’s neural efficiency theory of g) as a major determinant of timing performance.

•The higher the frequency (higher speed) of neural oscillations the finer the temporal resolution of the internal clock = greater timing accuracy (Rammsayer & Brandler; 2007)

Temporal g ?

According to the master internal clock theory:

•Higher clock speed/rate-

•Should enable an individual to perform a specific sequence of mental operations faster

•Decreases the probability of occurrence of interfering incidents (i.e., better inhibition – or conversely – increased disinhibition)

Higher clock speed/ratesuperior performance in cognitive tasks as well as in basic information processing skills.

Temporal g ?

•Research has suggested that that a unitary internal master clock accounts for performance across four major types of elementary timing experiences (Rammsayer & Brandler, 2006, in press).

•Interval duration or discrimination timing

•Rhythm perception and production

•Temporal-order judgment (TOJ)

•Simultaneity and successiveness

Temporal g ?

Rhythm Perception and Production: Types of Tasks Studied

Rammsayer’s temporal g tasks

Detection of rhythmic sequences

“Continuation” (non-tapping) tasks

“Synchronized” (tapping tasks)

Synchronization of movements with a sequence of external events has been studied for a long time. The simplest task, synchronization with a metronome that produces auditory sounds equally spaced in time, is well understood (Schulze, 2005)

Synchronized (tapping tasks) Theoretical Model

(Schulze et al., 2005)

Well described by the Wing- Kristofferson two- level model (Wing & Kristofferson, 1973) augmented by a linear phase-error correction mechanism

Central notions of model

•The assumption of an internal time keeper that controls the interval between taps and triggers the motor system correspondingly.

•Error correction mechanism is necessary because the timekeeper and the motor system are subject to temporal jitter

Most prominent and accepted “generic” model is the Pacemaker-Accumulator Model based On Scalar Timing/Expectancy Theory

Pacemaker-Accumulator Model basedOn Scalar Timing/Expectancy Theory

(Church, 1984; Gibbon et al., 1984; Meck, 1983)

The most prominent theory/model of time/temporal estimation*

Time duration judgments are performed by a modular information processing system composed of:

•Clock

•Memory

•Decision processes

* [Prominent does not mean exclusive – eg…see alternative MTS (multiple time scales) model that does NOT include internal pacemaker – instead time is based on length of decaying/fading memory traces]

(an oscillator) (a counter)

The “clock”level

Regularly generates or emits

neural ticks or pulses

“gaiting” switch from pacemaker to accumulator

Accumulates ticks/pulses that correspond to physical time

interval/duration (neural counting)

“dopaminergic pacemaker”

(an oscillator) (a counter)

The “memory”level

“Raw” representation of stimulus duration transferred to short-term or working memory

Includes “important times” or “standards (reference)” appropriate for task

(an oscillator) (a counter)

The “decision”level

Comparison made between contents of reference memory (the standard) and working memory (are they “close” ?).

Relies on a comparator that determines a response on the basis of a decision rule which involves a comparison between a value in the accumulator or working memory corresponding to the current duration with a value from reference memory

(an oscillator) (a counter)

Another common representationoff this model/theory

Pacemaker-Accumulator Model basedOn Scalar Timing/Expectancy Theory

(Church, 1984; Gibbon et al., 1984; Meck, 1983)

Important “cross-walk” links can be made between the PAM model

and contemporary cognitive, neuropsychological, and

intelligence research

(an oscillator) (a counter)

Pacemaker-Accumulator Model basedOn Scalar Timing/Expectancy Theory

(Church, 1984; Gibbon et al., 1984; Meck, 1983)

Analagous cognitive & intelligence contsructs

Working memory (Gsm-MS; MW)

Long-term storage and retrieval (Glr)

Executive function

Executive controlled attention

(an oscillator) (a counter)

What are the possible underlying neurological functions/structures involved?

A very very simplified review

Intelligence theory

•Cattell-Horn-Carroll (CHC) theory of cognitive abilities

Neuropsychological theory

•Executive functioning•Working memory•Controlled executive attention

What cognitive/neuropsychological mechanisms may be involved/affected?

“Big five” reciprocal frontal-subcortical circuits (loops/pathways)

•There are at least five big loops/circuits involved in the highest levels of self-management (Lichter & Cummings, 2001)

•These “loops” give rise to the complexity of goal-directed behavior

•All five circuits (motor, oculomotor, dorsolateral prefrontal, anterior cingulate) are related to the frontal lobe, basal ganglia, and thalamus (Hale & Fiorello, 2004)

•The frontal-striatal loop has been associated with timing related functions (Nobre & O’Reilly, 2004)

(Casey & Durston, 2006)

Example of a circuit/loop

Prefrontal cortex

• “Cognitively controlled timing activates the right hemispheric dorsolateral prefrontal cortex (DLPFC) more frequently than any other brain area” (Lewis & Miall, 2006)

Right Parietal cortex

Motor cortex areas

Cerebellum

Basal ganglia operating via frontal-striatal loop/network

Primary brain mechanisms involved in mental time-keeping/temporal processing

The executive function is a theorized cognitive system (cluster of skills) that controls and manages other cognitive processes (Baddeley & Hitch, 1974).

Executive functions include:

•Attention•Planning•Strategizing•Organizing•Flexibility•Monitoring•Evaluation•Change

Processes involved in mentaltiming are also thought to be components of EF (Welsh, 2001)

Has also been called the Supervisory Attention System (SAS; Norman & Shallice, 1986) and Executive Control (Posner and DiGirolamo (2000)

•Increased efficiency of working memory

•Increased ability to sustain and selectively divide attention for longer periods of time (executive/controlled attention)?

•Increased ability to filter or screen out distractions (increased selective attention)?

•Increased ability to inhibit impulsive responding (decreased disinhibition)?

•Increased ability to self-regulate/monitor mental operations (metacognition)?

•Increased efficiency of internal master clock (higher clock rate)

Hypothesized changes in specific cognitive efficiency/executive

functions due to increased temporal g (higher temporal mental clock resolution): Increased

“focus” or “cognitive efficiency”

What mechanism allows the integration of diverse brain networks to form coherent perceptions and output, with minimal (or even zero) time lag?

Evidence from both animal and human studies indicates that the phase synchrony of high frequency Gamma oscillations is a central mechanism in the integration and binding of geographically distinct brain activities (Phillips & Singer, 1997; Stankov et al., 2006).

At the level of the whole brain (i.e., collective populations of cells), greater phase synchronization of high frequency Gamma oscillations can differ from person to person -- may account for individual differences in measured cognitive ability.

Synchronous activity - the tuning-in of brain cell populations.

Another possible research connection?The “binding problem” (Stankov et al., 2006)

The internal brain clock as conductor metaphor

Brain clock synchronizes neural oscillations across diverse brain structures/locations

Think of conductor as executive function manager

The PFC has been likened to a switch operator in a railway system (Miller & Cohen; 2001.) [Also see “task switching” attention research summarized by Pashler et al., 2001)

“If several trains (different systems of representations or pathways) use the same bit of track to get where they are going (i.e., use the same output pathways when competing for expression in behavior), then a coordinator is needed to guide them safely to their destinations. Some trains must be stopped at the station; others may be stopped mid-route. Some will be allowed to go, and still others asked to speed up. The fastest train will use the track first (the system with the strongest activation pattern is expressed). The resource limitations of controlled attention are thought to reflect the properties of PFC function (Miller & Cohen, 2001) such that the fundamental computational properties of the PFC are likely related to the ability to control the trains.” (Barrett et al., 2004)

The internal brain clock as conductor metaphor

Brain clock as brain track (pathway) switch coordinator

A possible lay-person term for

controlled executive attention is focus

•“the concentration of attention or energy on something”

•“concentrate: direct one's

attention on something”

Controlled Executive Attention Model of Working Memory

Speed of mental information processing example (CHC info

processing model example task)

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The CHC Information Processing Model

Cognitive orAcademic Performance

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ExecutiveControlGs

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Stores of Acquired Knowledge

SMT (e.g. IM) is hypothesized to increase the efficiency of the “information processing loop” – increased “cognitive efficiency” due to increased efficiency/resolution of the internal mental clock---which results in greater “synchronization” or “path/track switch coordination”

Summary Comments

Mental timing is a domain-general mechanism important for human learning and memory and governs the temporal processing efficiency of the human information processing system

Key concepts relevant to understanding mental time-keeping and temporal processing, which may lie at the heart of SMT (IM)-based interventions, include

Summary Comments

•Internal master clock

•Faster clock speed/rate

•More coordinated/integrated/synchronized master clock (the “conductor”)•Increased “tuning in” or synchronization across brain activities/brain cell populations•Finer temporal resolution of internal clock (via higher frequency of neural oscillations)•Increased temporal g?

•Working memory –research suggests that time measurement and working tasks draw upon many of the same cognitive/brain resources

• e.g.- both are modulated by dopamine

•Executive functions, esp.•Controlled executive attention (“focus”)•Self-regulation/monitoring or metacognition (e.g., railroad switching efficiency)

Summary Comments

Other SMT (IM)-Specific Speculations

Anecdotal reports from treatment subjects suggests possible improvements in non-cognitive variables that have been demonstrated to positively impact school learning

Conative variables (work of Richard Snow et al.)

•Increased self-efficacy

•Confidence in ability to organize, execute, and regulate performance in order to solve problem or perform a task at a designated level of skill and ability

For consideration: Internal brain clock metaphors

Mental synchronization is all about timing