Interictal fast ripples recorded from a dense microelectrode array in human epileptic neocortex
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Interictal Fast Ripples Recorded from a Dense Microelectrode Array in Human Epileptic Neocortex. Catherine Schevon , MD, PhD; Andrew Trevelyan, PhD; Robert Goodman, MD; Guy McKhann Jr , MD; Charles Schroeder, PhD; Ronald Emerson, MD June, 2009. I. II. III. IV. V. VI. WM.

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Interictal fast ripples recorded from a dense microelectrode array in human epileptic neocortex l.jpg
Interictal Fast Ripples Recorded from a Dense Microelectrode Array in Human Epileptic Neocortex

Catherine Schevon, MD, PhD; Andrew Trevelyan, PhD; Robert Goodman, MD; Guy McKhannJr, MD; Charles Schroeder, PhD; Ronald Emerson, MD

June, 2009


Slide2 l.jpg

I Array in Human Epileptic Neocortex

II

III

IV

V

VI

WM

Multielectrode Array (MEA)

NeuroPortTM, CyberkineticsNeurotechnology Systems, Foxboro, MA

(now Blackrock Microsystems, Salt Lake City, UT)

  • Covers 4 x 4 mm area

  • 96 contacts in a regular 10x10 grid

  • Depth 1 mm (Layer IV/V)

  • 400 micron spacing

  • Active tips 35-75 μm long x 3-5 μm radius

  • 30K samples/channel/sec

  • Implanted in epilepsy patients undergoing chronic intracranial EEG recording, in neocortex to be included in resection

  • Advantages:

    • Fine spatial/temporal resolution

    • Regular grid spacing

  • Limitations:

    • Records from one small area

    • One cortical layer per site


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“µEEG Array in Human Epileptic Neocortex”

iEEG

  • Microelectrode recording downsampled and aligned with clinical EEG recording

  • “Macrodischarges”

    • Correlate with iEEG epileptiform discharges

    • Appear widespread in µEEG

μEEG


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Array in Human Epileptic NeocortexMicrodischarges”


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30 ms Array in Human Epileptic Neocortex

40 ms

200 µV

200 µV

50 µV

50 µV

30 µV

30 µV

30 µV

30 µV

µEEG

µEEG

100-200 Hz

HFO associated with a macrodischarge

200-500 Hz

0.8 – 2 kHz

µEEG

µEEG

100-200 Hz

HFO associated with a microdischarge

200-500 Hz

0.8 – 2 kHz

1 second

1 second


Correlation with interictal events l.jpg
Correlation with interictal events Array in Human Epileptic Neocortex

Detections/min during sleep and association with paroxysmal µEEG features

Percentage of macrodischarges and microdischarges with associated HFOs


Detections by array location l.jpg
Detections by array location Array in Human Epileptic Neocortex


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85% of events were seen at a single channel

40 µV

50 ms


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11% of events occurred on a large scale

Almost all were found within the epileptogenic zone (ie not in Patient 1)

80% of these occurred with macrodischarges

40 µV

400 ms


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200 are detectedµV

50 ms

50 ms

µEEG

Site to site differences during a large scale event

100-200 Hz

200-500 Hz

0.8 – 2 kHz

µEEG

100-200 Hz

200-500 Hz

0.8 – 2 kHz


Conclusions and questions l.jpg
Conclusions and Questions are detected

  • HFOs and microdischarges are distinct phenomena

    • Evidence of different mechanisms underlying microdischarges and macrodischarges?

  • Large-scale HFOs

    • Arise from multiple simultaneous independent generators

    • Specific markers of the epileptogenic zone?

    • Selectively detected by sparse sampling or large sensors?

    • Evidence of an epileptic network?

  • Are fast ripples a primary event or a secondary local response (eg excitability)?


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Co-authors and colleagues are detected

Ron Emerson

Robert Goodman

Guy McKhann, Jr.

Charles Schroeder

Andrew Trevelyan

Allen Waziri

Julien Besle

Joe Isler

Anna Ipata

Elana Zion-Golumbic

Sara Inati

Peter Lakatos

Dan Friedman

Helen Scharfman

Michael Goldberg


Are all hfos created equal l.jpg
Are all HFOs created equal? are detected

  • Recording characteristics of Neuroport microelectrodes vsmicrowires or depth electrodes

  • Selective recording from cortical layers IV and V

  • Use of detection thresholds create the impression of a binary process


Hfo rates l.jpg
HFO rates are detected

  • Higher HFO rates (overall and max per channel) than seen with microwires or macroelectrodes but avg per channel similar

  • HFOs more frequent in epileptogenic zone (but N of 1 outside EZ…)

  • Almost all HFOs had a fast ripple component


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HFO duration are detected

Filtered 100-500 Hz activity in subset of channels

Average of all channels (what a macroelectrode would see?)


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