Measures electrical activity of neurons near electrode tip

Single-electrodeRecording

The primary tool for investigation of brain-

behavior relationships for over 60 years

A useful tool for studying the details of properties of individual neurons. Ideal for an understanding at the level of individual neurons.

Less appropriate for studying networks and systems of neurons.

Does not allow measurements of the precise timing of activity between neurons that give insight into how they communicate and interact.

The classic single-electrode approach only allows indirect inferences about neural networks.

The result: a piecemeal understanding of brain function

A More Global View of Brain Function: FMRI. However….

FMRI measures patterns of blood flow to brain areas (the BOLD signal). Result of neurons needing energy (oxygen) when they fire electrical impulses (“action potentials”).

The Good:Provides a global view of which brain areas are engaged by a cognitive function.

The Bad:It takes five-six seconds for the BOLD signal to build. A lot can happen in the brain in 5-6 seconds.

Our approach: Multiple-electrode Recording in Monkeys Performing Cognitive-demanding Tasks

Electrode arrays with 500 um spacing to investigate

microcircuitry

Electrode arrays in different brain areas to investigate large-scale

networks.

Allows direct measurements of the networks that underlie cognition.

Brain waves are rhythmic, coordinated oscillations between neurons (1 – 100 Hz). They reflect how and when networks of neurons communicate.

They allow local networks of neurons to synchronize with one another and with distant networks. This allows the brain to orchestrate billions of neurons to produce elaborate behaviors.

The idea is that when neurons fire in synchrony with one another, they are better able to communicate than when they fire out of sync.

Mounting evidence that brain waves play a critical role in attention, working memory, memory storage, recall, learning, sequencing, planning and more. Abnormal brain waves are associated with neuropsychiatric disorders.

Brain Waves Play a Central Role in Brain Function

•Parkinson’s patients show increased beta band brain waves (which can be decreased by DA therapy)•Schizophrenia patients show decreased gamma band brain waves.•Guanfacine (ADHD treatment) increases brain wave (EEG) synchrony in rats.•Methylphenidate (ADHD) increases theta brain waves in the hippocampus.

Our Approach:Complex Behavioral Paradigms for Complex Cognition

1. We use monkeys. Primates have higher-level, and more flexible, cognition than other animals.

2. The Miller Lab are experts at animal training and design the most sophisticated behavioral paradigms in systems neurophysiology.

Learning of abstract categories and concepts

Rule learningMulti-taskingDecision-makingTask switchingReversal learningSequence memoryPlanningAttentionWorking Memory

“Cats vs dogs”Small numbers

Functional Endpoints: Proposed Project Our multiple electrodes and sophisticated behavioral paradigms can provide precise diagnostic tools for assessing the effects of guanfacine (and other drugs) on the mechanisms of cognition.

1. Our task: Enhancement of higher-order (prefrontal cortex-dependent) learningGuanfacine does not improve simple learning (subcortical or posterior cortical-dependent). It does improve many prefrontal cortex (PFC) dependent tasks, but its effects on PFC-dependent learning are not known.

We will use a learning task (conditional visuomotor learning) that is highly PFC dependent. Guanfacine, at the proper dose, should improve learning.

2. Multiple-electrodes offer a powerful diagnostic for directly measuring the effects of guanfacine on cognition.Arnsten and colleagues have provided elegant evidence that guanfacine improves communication in PFC microcircuits that underlie working memory (“delay”) activity. This was indirectly inferred from the activity of single neurons as well as detailed anatomy.

Multiple electrodes allow direct examination of the functioning of microcircuits. This gets directly at the network mechanisms underlying cognition and how they are improved by drug therapy.

Novel images

Familiar images

Fixation

Cue Delay Target onset

800 ms

500 ms 1000 ms Response

40 %

40 %

10 %

10 %

The Role of Dopamine (D1R) Receptors in the Prefrontal Cortex During Learning

Monkeys learned by trial and error to associate two novel visual cues with either an eye movement to the right or left

1 2 3 4 5 6 7 8 9 …

Injection schedules

Block number

Location of the injections and grid configuration

Saline 3 µlSCH 23390 (D1 antagonist) 30 µg in 3 µl

Infusion rate: 0.3 µl/min (3 µl in 10 minutes)

Baseline Drug Washout------------//-----------

1 2 3 4 5 6 7 8 9 …

Baseline Drug Washout------------//-----------

1 2 3 4 5 6 7 8 9 …

Baseline Drug Washout------------//-----------

Session type #1

Session type #2

Session type #3

Recording with Multiple Electrodes while Injecting a D1R Blocker

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cent

Cor

rect

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Trial From Block Switch-60 -40 -20 0 20 40 60

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cent

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rect

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Blocking D1R Receptors Impairs New Learning But Not Long-Term Memory

Performance novel associations Performance familiar associations

1

70

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90

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100

Baseline Saline Washout

Perc

ent c

orre

ct

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Baseline SCH Washout

Perc

ent c

orre

ct

ns

Saline

SCH23390

Baseline Washout

WashoutBaseline

Criterion

Chance

Blocking D1Rs Decreases Attention and Increases Impulsivity

1 2 30

20

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Fixation breaks per block Early trials per block

Baseline Treatment Washout Baseline Treatment Washout

SalineSCH

Effect on attention Effect on impulsivity

***

***

******

D1R blockade induces negative deflections on the LFPs

Injection

Neuronal avalanches are generated by super-synchronous activity

0 4 8 12 16 20 24 28-0.5

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plitu

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plitu

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Time (sec)

Avalanches appeared in 47 of 68 electrodes (~70% of 9 sessions)

Duration 18 ± 5min (~10-30 min)

Frequency of deflections0.44 ± 0.03 Hz (0.2-0.6 Hz)

Amplitude of deflections is huge: in most cases over 500 mV

Performance7 sessions with impairment: drops to 56 ± 15 %

Ampl

itude

(mV)

Blocking D1R Receptors Causes a Broad-Band Increase in PFC Brain Waves

Cue

Delay

Response

No

rma

lize

d s

pe

ctru

m d

B

BaselineSCH

Task Interval:

Brain wave frequency

No

rma

lize

d s

pe

ctr

um

dB

Abnormal brain waves are a bad thing

Puig, M.V. and Miller, E.K. (in preparation)

Functional Endpoints: Other Projects

1. Improve functioning of orbital frontal cortex (OFC) networksReversal learning is highly dependent on the OFC. By adding the requirement to reverse associations to our conditional visuomotor task, we can make it an OFC task. Guanfacine should improve reversal learning and our multiple electrodes can directly measure the network cellular basis for that improvement.

2. Guanfacine as an intelligence enhancerWe know that guanfacine improves working memory (WM) for a single to-be-remembered item and helps alleviate ADHD. Can it improve general intelligence?

The ability to hold a single item in WM does not correlate well with general intelligence and single item WM is not impaired in many neuropsychiatric disorders.

By contrast, WM capacity (how many items you can hold in WM simultaneously) correlates highly with intelligence measures and is reduced in virtually every neuropsychiatric disorder and in aging. In other words, WM capacity may be a great diagnostic of WM function.

Multiple-electrode neurophysiology provides a direct and powerful measure of the cellular basis for the network properties that underlie cognitive enhancements by guanfacine.

Cognitive capacity: How many things can you hold in mind simultaneously?

Individual differences in capacity limits can explain about 25-50% of the individual

differences in tests of intelligence

It is linked to normal cognition and intelligence:

Capacity is highest in younger adults and reduced in many neuropsychiatric disorders

Schizophrenia

Parkinson’s Disease

Vogel et al (2001); Gold et al (2003); Cowan et al (2006); Hackley et al (2009)www.ekmiller.org

Cognitive capacity is the bandwidth of cognition. It may be directly related to brain waves.

Guanfacine as an intelligence enhancer

The Miller Lab used cutting edge multiple-electrode technology to that has yielded the first neurophysiological insight in WM capacity limitations: gamma-band oscillations (brain waves) in the prefrontal cortex.

Siegel, Warden, and Miller (2009) showed that PFC gamma-band brain waves provide “memory slots” for holding multiple items in WM. WM capacity is due to a limited number of slots per wave.

In theory (soon to be tested), we can increase WM capacity by slowing down the brain wave frequency or increasing its amplitude. This could add 1-2 more memory slots and effectively increase general intelligence.

Functional Endpoints: Other Projects

Brain waves are central to brain function. They regulate communication between neurons and there is mounting evidence that they play specific and important roles in higher cognition. Abnormal brain waves are apparent in neuropsychiatric disorders.

Multiple-electrodes offer a new tool for directly measuring the effects of potential drug therapies on cognition. They allow direct examination of the functioning of microcircuits and large-scale networks of neurons. This gets directly at the network mechanisms underlying cognition.

The combination of cutting-edge multiple-electrode technology and sophisticated behavioral paradigms in monkeys can provide a powerful diagnostic of the cellular mechanisms that underlie cognitive enhancements by potential drug therapies.

CONCLUSIONS

What the Miller Lab can offer Shire1. Investigation of brain-pharmacology-neurophysiology relationships

using cutting-edge multiple-electrode recording techniques.The Miller Lab has invented and pioneered the use of multiple electrodes in behaving monkeys. This has yielded new and direct insight into the communication within networks of neurons during high-level cognition. This can provide a power diagnostic for assessing potential drug therapies.

2. Investigation of the highest levels of cognitive function using the most sophisticated animal training in neuroscience.Most neurophysiological studies of cognition use relatively basic tasks (“pay attention here.” “hold one thing in mind”) The Miller Lab has taken monkey training to a higher level than any other lab. We have taught monkeys to juggle multiple things in memory, anticipate and imagine forthcoming events, make cognitive decisions, to recognize abstract categories and concepts (“cat vs dog”, “same vs different”, numbers 1-5). More complex behavioral methods are needed to understand the pharmacology of truly intelligent behavior.

We can also apply this approach to a wide range of cognitive functions

Category Learning

Freedman, Riesenhuber, Poggio, and Miller (2001) ScienceFreedman, Riesenhuber, Poggio, and Miller (2002) J. NeurophysiologyFreedman, Riesenhuber, Poggio, and Miller (2003) J. NeuroscienceRoy, Riesenhuber, Poggio, and Miller (submitted)Cromer, Roy, Riesenhuber, Poggio, and Miller (in preparation)

Fundamental to normal human cognition because they imbue the world with meaning.

They allow discarding detailed information in favor of general concepts.

Disrupted in neuropsychiatric disorders such as autism, schizophrenia, and learning disorders.

Patients become mired in details (they lose the forest in the trees).

Freedman, Riesenhuber, Poggio, and Miller (2001) ScienceFreedman, Riesenhuber, Poggio, and Miller (2002) J. NeurophysiologyFreedman, Riesenhuber, Poggio, and Miller (2003) J. NeuroscienceRoy, Riesenhuber, Poggio, and Miller (submitted)Cromer, Roy, Riesenhuber, Poggio, and Miller (in preparation)

For example, my concept of dogs is inextricably linked to every dog I've ever known. It's as if I have a card catalog of dogs I have seen, complete with pictures, which continually grows as I add more examples to my video library.

Temple Grandin, Ph.D. Thinking in Pictures

Categories and Concepts

Category boundary

50%

Prototypes100% Cat

80% Cat Morphs

60% Cat Morphs

60% Dog Morphs 80% Dog

Morphs

Prototypes 100% Dog

“Cats” Versus “Dogs”

Learned categories: monkeys had no prior experience with cats and dogs and could learn to categorize the stimuli after their reassignment to arbitrary categories.

“cats”

“dogs”

category boundary

C1

C2

C3

D2

D3D1

Activity to individual stimuli along the 9 morph lines that crossed the category boundary

Single neuron:

0 0.5 1.0

Normalized firing rate

C1C1C1C2C2C2

C3C3

C3

D1D2D3D1D2D3

D2D3

D1

About 1/3 of Prefrontal Neurons Respond to Category Membership not Physical Appearance

Freedman, Riesenhuber, Poggio, and Miller (2001) ScienceFreedman, Riesenhuber, Poggio, and Miller (2002) J. NeurophysiologyFreedman, Riesenhuber, Poggio, and Miller (2003) J. Neuroscience

Theories of Prefrontal Cortex Function

Basal ganglia (striatum): Fast, reward-gated,

plasticity

Prefrontal cortex: Slower, reward-shaded, plasticity

Balance between advantages and disadvantages of slow and fast learning

Slower learning of more elaborate, generalized, less error-prone, representations that include the regularties across experiences.

Fast learning (“snapshots”) of the specific experiences that predict reward. Error prone.

The integrative anatomy of the PFC and BG allows rapid acquisition of the logic of a goal-directed task. This is a “roadmap” that specifies which pattern of “tracks” (neural pathways) are needed to solve a given task.

This pattern is activated and maintained in the PFC during task performance, producing “top-down” signals that bias the flow of activity in the cortex along task-relevant pathways.

Goal-directionOvercome habits

Flexibility

Miller, E.K. (2000) Nature Reviews Neuroscience, 1:59-65Miller, E.K. and Cohen, J.D. (2001) Annual Review of Neuroscience, 24:167-202

A switch operator in a system of railroad tracks:

Active

Inactive

BG loops PFC

Sensorycortex Motor

cortex

“Cue”

“Context”

Don’t answer

Answer

DA reward

Phonerings

At home

Guest

Goal-directionOvercome habits

Flexibility

A switch operator in a system of railroad tracks:

PFC

Sensorycortex Motor

cortex

“Cue”

“Context”

Don’t answer

Answer

Phonerings

At home

Guest

Active

InactiveMiller, E.K. (2000) Nature Reviews Neuroscience, 1:59-65

Miller, E.K. and Cohen, J.D. (2001) Annual Review of Neuroscience, 24:167-202

The integrative anatomy of the PFC and BG allows rapid acquisition of the logic of a goal-directed task. This is a “roadmap” that specifies which pattern of “tracks” (neural pathways) are needed to solve a given task.

This pattern is activated and maintained in the PFC during task performance, producing feedback signals that bias the flow of activity in the cortex along task-relevant pathways.

Goal-directionOvercome habits

Flexibility

A switch operator in a system of railroad tracks:

BG loops PFC

Sensorycortex Motor

cortex

“Cue”

“Context”

Don’t answer

Answer

DA reward

Phonerings

At home

Guest

Active

InactiveMiller, E.K. (2000) Nature Reviews Neuroscience, 1:59-65

Miller, E.K. and Cohen, J.D. (2001) Annual Review of Neuroscience, 24:167-202

The integrative anatomy of the PFC and BG allows rapid acquisition of the logic of a goal-directed task. This is a “roadmap” that specifies which pattern of “tracks” (neural pathways) are needed to solve a given task.

This pattern is activated and maintained in the PFC during task performance, producing feedback signals that bias the flow of activity in the cortex along task-relevant pathways.