This document discusses contemporary research on the neuroscience of brain-based interval timing and its relevance to learning and rehabilitation. It provides an overview of research showing that the human brain contains an internal clock mechanism for temporal processing. Mental timing abilities have been implicated in various cognitive functions and clinical disorders. Research suggests there are both automatic and cognitively controlled timing systems in the brain. Some studies indicate the internal clock can be modified through experience. The relationship between temporal processing, intelligence, and synchronization-based interventions like Interactive Metronome is explored.

1. 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)

2. 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.……………………

3. There is MUCH more to this research

6. Check out “IQ Brain
Clock EWOK” for specifics

7. 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

8. 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)

9. “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)

10. 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

11. 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

12. 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 Brain
Clock EWOK
for research)
Research suggests common dopamine link
(e.g., dopaminergic disorders)

13. 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)

14. 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

15. 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”

16. Timescales of
temporal
processing
(Mauk &
Buonomano, 2004)
Humans process
temporal
information over
scales of at least
10-12 orders of
magnitude that
have been
categorized into 3-
4 major timescale
groups

17. 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

18. 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

19. 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)

20. 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)

21. 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

22. 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

23. A domain-general
cognitive mechanism?
A number of domain (subject)-specific
cognitive mechanisms?
OR….

24. 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)

25. • 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)

26. •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)

27. 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 ?

28. •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 ?

29. •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 ?

30. •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 ?

31. 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/ratesuperior performance in cognitive tasks
as well as in basic information processing skills.
Temporal g ?

32. •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 ?

33. 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)

34. 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

35. Pacemaker-Accumulator Model based
On 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)

36. 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)

37. 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)

38. 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)

39. Another common representation
off this model/theory

40. Pacemaker-Accumulator Model based
On 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)

41. Pacemaker-Accumulator Model based
On 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)

42. What are the possible underlying
neurological functions/structures involved?
A very very simplified review

43. 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?

44. “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)

45. (Casey & Durston, 2006)
Example of a circuit/loop

46. 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

47. 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 mental
timing 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)

48. •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”

49. 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)

50. The internal brain clock as conductor metaphor
Brain clock synchronizes neural oscillations across
diverse brain structures/locations
Think of conductor as
executive function manager

51. 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

52. 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

53. Speed of mental information
processing example (CHC info
processing model example task)

54. Fluid
Intelligence
Crystallized
Intelligence
Gen.Memory
&Learning
BroadVisual
Perception
BroadAuditory
Perception
BroadRetrieval
Ability
BroadCognitive
Speediness
Dec/Reaction
Time/Speed
Gf Gq Gsm Gv Ga Gs CDS GrwGc Glr
Fluid
Intelligence
Crystallized
Intelligence
Quantitative
Knowledge
Short-Term
Memory
Visual
Processing
Auditory
Processing
Long-Term
Retrieval
Processing
Speed
Correct
DecisionSpeed
Reading/
Writing
g
Cattell-HornCarroll
Cattell-Horn-Carroll (CHC) Model of
Human Cognitive Abilities
Gf Gy Gv Gs GtGc GrGu

55. The CHC Information Processing Model
Cognitive or
Academic Performance
Gsm
(MW)
Information Processing Loop
Cognitive
Efficiency
Executive
ControlGs
Gf
Glr
Ga
Gv
Thinking
Abilities
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”

56. Summary Comments

57. 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

58. •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

59. 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

60. For consideration: Internal brain
clock metaphors
Mental synchronization
is all about timing