vent

elated

otentials

Decades of research suggest that bottlenose dolphins

utilize a complex system of communication, integral to

social interaction and survival. However, it is difficult to

assess signal complexity and function using behavioral

measures alone. Incorporating event-related

neurophysiological measures can enhance odontocete

cognitive, communicative

(1) Marine Mammal Behavior & Cognition Lab, University of Southern Mississippi, 118 College Dr #5025, Hattiesburg, MS, 39406, USA; (2) Department of Psychology, University of Kansas, 1415 Jayhawk Blvd., Lawrence, KS, 66045, USA; (3) ISPA, Rua Jardim do Tabaco 34, Lisboa, 1149-041, Portugal;

(4) Projecto Delfim, Centro Português de Estudo dos Mamíferos Marinhos, Rua Alto do Duque 45, Lisboa, 1400-009, Portugal; (5) Neuroscience & Bioacoustics, Communication Sciences & Disorders, University of Cincinnati Medical Center, 345A French East, 3202 Eden Ave, Cincinnati, OH, 45267, USA

Dominie Madonna Writt 1,2, Patrícia Rachinas-Lopes 3,4, Stan A. Kuczaj 1, Peter M. Scheifele 5, Manuel E. dos Santos 3,4

Advancing Cetacean Communication Research

NEUROPHYSIOLOGICAL INDICES OF COMPLEX SIGNAL PROCESSING IN BOTTLENOSE DOLPHINS, TURSIOPS TRUNCATUS

RESULTS

ERP

BACKGROUND

Acknowledgments: Many thanks are due Élio Vicente, Marco Braganca, and all the trainers and staff at Zoomarine (Algarve, Portugal) for their support and tireless efforts. Without their dedication this project would not have been possible. Additional financial support provided by a KU honors fellowship to the first author and through U.S. and Kansas State agencies. Thanks also to Joana Augusto for her invaluable

help with stimulus recording and equipment set-up and testing. Thanks to Jim Juola, Patricia Hawley, Andrea Greenhoot, Allard Jongman, and Michael Greenfield for their encouragement and advice in designing the project, and thanks for all the helpful feedback on previous research from colleagues in my field. I am also compelled to thank my amazing children, Gabe and Halle, who have managed so marvelously

throughout my dissertation journey. Their love and support is priceless! If you have any comments/questions/suggestions or are interested in discussing the potential application of ERP to your research programs, feel free to contact the first author , Dominie Writt, at dominie@cetaceanscience.com.

Component Property Differences Sensitive to Stimulus Expectancy & Complexity

~Ring-Cap & Tail (5-10 mm Ag/AgCl electrodes) ~Lubell EV-UW30 underwater speaker ~Cetacean Research Technology SQ26-MT hydrophone

METHODS

Ring-Cap New non-invasive

method of applying

multiple-electrode

arrays (similar to

caps used for

human research)

Preliminary analyses reveal probability-related positivities (left) similar across subjects and similar to previous findings by this team (above, collapsed across channel) that are sensitive to stimulus complexity and information-content.

The relative latency increase between the two positive peaks (~750 & 1300 ms pSO, left) observed following long-tone and whistle stimuli (1000 ms) and the positivities (620 & 740 ms pSO, above) previously isolated following short-tone stimuli (100 ms) could be related to:

~ Longer Stimulus Duration and/or ~ Increased Stimulus Integration Complexity due to:

◦ Processing Demands to Update Divergent Stimulus Types (Tone-to-Whistle or Whistle-to-Tone)

◦ Stimulus Complexity and/or ◦ Stimulus Relevance to Subject

The whistle-related late positive peak that is observed at all recording locations is only seen at the P4 electrode site when the whistle is played in reverse.

In addition, a significant negative deviation is observed at A3 following the presentation of reversed whistles.

research by providing an additional dependent variable for research in which overt

behavioral responses prove challenging to generate or interpret.

Exogenous evoked-potentials (EPs) have been well-established as cost-effective measures

of odontocete sensory processing, but endogenous (cognitive) event-related potentials

(ERPs) have yet to be established for dolphin cognition and communication research.

Oddball vs. Standard Whistles

A3

A3

FUTURE DIRECTIONS

STIMULI ~Tones (8 or 12 kHz) – 1000 ms

~Whistles: (most frequent during isolation) Type 1 (Apollo)

Type 2 (Ulisses)

~Altered Whistles

SESSIONS ~Random Blocks (2-4 min)

~Random ISI (1-2 sec)

~30-75 Traces/Condition

(collected over multiple sessions) Apollo (5 yrs)

Lotus (13 yrs)

Hugo (12 yrs)

SUBJECTS Male

ERP components can be collected noninvasively (using recording electrodes at the surface of the skin) from subjects in and out of the water.

To establish ERPs as useful measures of odontocete cognition, it is first necessary that stable neuro-electrical indexes of event-related processes be repeatedly isolated across research groups.

Previous work by our team1 revealed a Late Probability-Related Positivity (LPP, top left) resembling the P550 first isolated by Woods and colleagues2 (1986, bottom left) using more invasive recording methods; this positivity could reflect a stable dolphin ERP component that indexes endogenous context-updating processes similar to the well-established human P300 (top right). A P300-like LPP has also recently been isolated from a beluga whale by Scheifele and colleagues3 (bottom right).

Some of the endogenous context-updating processes reflected by the human P300 are sensitive to variations in signal complexity and meaning. If a dolphin LPP indexes similar processes, it could prove valuable for investigating dolphin communication systems.

Directional Electrode Placement System (DEPS)

*Placement units vary depending upon approximated EN measurements.

Similarly oriented, synchronously firing cortical pyramidal neurons can generate scalp-recordable dipole currents. Pyramidal cell illustration (left) adapted from Luck (Figure 1.4, 2005*).

Cognitive ERPs can reflect signals from multiple overlapping processes generated at different locations on the convoluted cortex.

ERPs are event-related neuro-electrical waveforms isolated by averaging multiple event trace recordings to retain relevant information and cancel out unrelated information.

Referenced Odontocete Electrophysiological Research* 1Writt, Rachinas-Lopes, Kuczaj, dos Santos, Scheifele (2009) 2Woods, Ridgway, Carder, & Bullock (1986) 3Scheifele & Kiehl (2008) 4Szymanski, Bain, Kiehl , Pennington, Wong, Henry (1999) 5Supin, Nachtigall, Pawloski, Au (2003) 6Mooney, Nachtigall, & Yuen (2006) 7Houser & Finneran (2006) 8Nachtigall, Supin, Pawloski, & Au (2004) 9Hernandez, Kuczaj, Houser, Finneran (2007) *see attachment for additional details

Late Probability-Related Positivities (LPPs) in three species: Top left, dolphin LPP (Writt & colleagues, 20091); bottom left, dolphin LPP (P550, Woods & colleagues, 19862); top right:: human P300 (Kraus & McGee, 1994); bottom right, beluga LPP (Scheifele, 20083).

(These data are comprised only of sessions in which one whistle was paired with one tone in either the standard or oddball condition; additional analysis including sessions with only whistles or only tones in both probability conditions will help to identify if any signal-type specificity exists and inform us about whether not the similarities in standard and oddball whistle waveforms are impacted by differences in the two whistle types.)

Recorded whistles elicit processing components unique from those elicited by tones and similarly complex nonsense whistles (reversed, below).

The first positive peak is present following tones in the oddball condition, but present for whistles in both the standard and oddball conditions (below).

A negativity 400-500 ms pSO (that could reflect acoustic processing similar to the human N1) is most prominent following whistle stimuli, regardless of oddball or standard condition.

Previous Findings

Surface recording locations for previous odontocete electrophysiological research translated into DEPS EN units, revealing similarities among ideal recording locations irrespective of subject size differences.

ERP RECORDING Synergy NPE5 bioamplifier – Band-pass filtered (0.06-50 Hz);

Sampling rate of 50 kHz; Continuous EEG recordings; Stimulus onset marked by custom-designed WhistleSTIM software; Processed & combined offline as individual traces

(-100 to 1600 ms post-stimulus onset, pSO)

Ring-Cap & Tail with 5 active electrodes at A3, A1L3, A1R3, P2, & P4

using a 2.5 DEPS EN unit (see description below)

P300s are commonly elicited using an Oddball Paradigm: Rare ODDBALL

stimuli randomly interspersed among repeated presentations of a STANDARD stimulus Oddball Paradigm

Testing equipment and component isolation with human subject.

The establishment (through replication) of a P300-like odontocete LPP and related cognitive ERP components (sensitive to

variations in signal meaning and complexity) could prove extremely valuable for investigating dolphin communication systems

via the (1) isolation, (2) identification, and (3) categorization of communication signals. Furthermore, understanding

how dolphins communicate will help us explore how they

survive in increasingly unpredictable, hostile environments. And

determining what aspects of the communication signal are most

vital for successful social coordination will help us determine

and mitigate any harmful effects related to anthropogenic noise.

Oddball (15%) Standard (85%)

WhistleSTIM

A Relative Referencing System: 10% of the Eye-to-Naris (EN) distance

= 1 EN UNIT

Step 1. Measure Posterior or Anterior from Naris (Posterior Margin)

2 EN UNITS posterior

Step 2. Measure Right or Left

2 EN UNITS right

Killer Whale (Orcinus orca)4 AEP - 17 cm posterior to blowhole ~ P3

Beluga (Delphinapterus leucas)3 LPP - 7.5 cm posterior to blowhole ~ P2

False Killer Whale (Pseudorca crassidens)5 AEP - 10 cm posterior to blowhole ~ P2

Infant Risso’s Dolphin (Grampus griseus)6 AEP - 3.5 cm posterior to blowhole and right of midline ~ P2R1

Bottlenose Dolphin (Tursiops truncatus)1,7,8,9 LPP - maximally recorded 9-10 cm posterior to blowhole ~ P4

AEP - 5-7 cm posterior to blowhole ~ P2-P3

AEP - 10 cm posterior to blowhole & 2 cm right of midline ~ P4R1

P50 - 4 cm posterior to blowhole & right/left of midline ~ P2L2 ~ P2R2

BLOWHOLE

Rare Whistles vs. Rare Tones Preliminary Analysis

Oddball (15%)

Standard (85%)

*solid vertical lines identify significant mean differences (p <.05)

Amplifier

Signal Averager

Ongoing EEG Event-Related Potential (ERP)