This research was supported by Grants R01AA15384 from the National Institute on Alcohol Abuse and Alcoholism and 5R01DA033809-02 from the National Institute of Drug Abuse to John J. Curtin.

The local ethics committee has approved the following procedure and all participants who have taken part in this procedure have given informed consent. For additional detail of psychophysiological measurement and stimulus presentation please see30,27.
1. Electromyography (EMG) Recording Preparation
<ol>
	<li>Ask the participant to wash their face thoroughly with soap, paying particular attention to the target sensor locations, which are located below one eye and in the middle of t...

The authors declare that they have no competing financial interests.

The Threat Probability Task can be used to study the expression of anxiety and fear by assessing startle potentiation to low probability (uncertain) and high probability (certain) threat of electric shock. The primary dependent measure and threat contingencies used in this task can be used with rodents, non-human primates and humans, thus, providing an excellent translational tool for studying the expression of negative affect13,18,40. Startle potentiation to threat of electric shock has clear connections to d...

The overall goal of the Threat Probability Task is to experimentally disentangle the expression of anxiety in response to low probability (i.e., uncertain) threats from fear in response to high probability (i.e., certain) threats. Uncertainty occurs when some aspect of a threat is poorly defined. While anxiety can be described in numerous ways, exacerbated responses to low probability or otherwise uncertain negative events is a distinguishing clinical symptom in anxiety disorders1,2. Furthermore, increased anxiety related physiological responding during uncertain threat of shock versus fear related physiological responding during certain threat of shock in laboratory tasks may provide a physiological marker for anxiety disorders3. Dampening of anxiety to uncertain threats specifically may be a critical component of the stress response dampening properties of drugs such as alcohol4-7. Increased anxiety during uncertain threat may mark a neuroadaptation in the brain&#8217;s stress circuitry following chronic drug use4,8. Thus, the Threat Probability Task provides an objective measure of negative affective and distinct emotional states (anxiety, fear) to use in research on psychopathology, substance use/abuse and affective science. As such, it can be a powerful tool for use by clinical and affective scientists interested in psychopathology etiology and individual differences in emotion.
Traditional methods used to study emotions in humans
Affective scientists have used numerous measures and paradigms to study human emotion9 but most of these do not provide the necessary precision found in the Threat Probability Task to parse anxiety from other negative emotions such as fear. For example, self-report is commonly used but it may suffer from demand characteristics and other forms of response bias. Participants may not be able to accurately distinguish between anxiety and fear, and the connection of their report to underlying neurobiological mechanisms is distal at best. Furthermore, self-report must often be conducted retrospectively since the process of introspection and report might otherwise alter participants&#8217; experience of the affective stimuli. Of course, retrospective report suffers from memory interference and degradation. Psychophysiologists often measure emotions during an affect manipulation that involves presentation of emotionally evocative pictures10. This picture viewing task is well validated, is less affected by the shortcomings of self-report, and has resulted in many important insights regarding individual differences in affective response and their contribution to psychopathology11,12. However, only broad negative affect is measured during this picture viewing task which does not allow for the study of distinct negative emotions such as anxiety and fear which can be measured with the Threat Probability Task. Affective neuroscientists frequently measure functional magnetic resonance imaging (fMRI) during tasks that elicit negative affect but these approaches may be too costly for many researchers. Furthermore, the spatial and temporal resolutions of fMRI methods are currently limited, making it difficult for fMRI to disentangle the neurological structures believed to be associated with anxiety versus other emotions. More importantly, a well-defined fMRI index of any type of negative affect has yet to be established.
Translational research with animals using the startle response
The Threat Probability Task is modeled after basic research with animals that provided the first example of the precision needed to disentangle anxiety from fear. Neuroscientists have used carefully controlled lesion studies with rodents to model anxiety and fear using differential responses to uncertain and certain cued threat of electric shock. This work has elucidated important differences in anxiety related responses to low probability, ambiguously defined, distal or otherwise uncertain shock versus fear related responses to highly probable, clearly defined, imminent certain shock13. Uncertain threats elicit freezing and hyper vigilance in animals, whereas certain threats elicit active avoidance, defensive attack, or both14. Imminent, certain threats focus attention on the threat itself, whereas distal, temporally uncertain threats encourage distributed attention to the overall environment15&#8211;17. Response to temporally uncertain threats appears to be sustained, whereas response to certain threats is phasic and time-locked to the threat13. In related work, lesion studies have shown that response to uncertain threats are selectively mediated by corticotrophin-releasing factor and norepinephrine pathways through the lateral divisions of the central nucleus of the amygdala and the bed nucleus of the stria terminalis18. Much of this work uses potentiation of the acoustic startle response as a primary dependent measure13, which is the same dependent measure used in the Threat Probability Task. The neurobiological substrates of the startle response circuit have been extensively studied with the discovery of clear connections to the brain structures active in responses to uncertain and certain threats19,20. The startle response can be assessed in numerous species which provides a powerful translational tool to study emotions. The startle response in humans occurs reflexively in response to a sudden and intense auditory stimulus. Startle is most often measured in humans by the placement of electromyography (EMG) electrodes on the orbicularis oculi (lid closing) muscle of the eye. Startle related EMG activity is potentiated when an organism is presented with a threatening stimulus such as an impending electric shock relative to non-threatening stimuli19.
The No-shock, Predictable-shock, Unpredictable-shock (NPU) task and threat uncertainty
The Threat Probability Task was inspired by Grillon and colleagues when these researchers introduced the use of startle potentiation to study anxiety and fear in humans with the No-shock, Predictable-shock, Unpredictable-shock (NPU) task21. In the Predictable condition of the NPU task, shocks are 100 percent cue-contingent and occur at a consistent, known time (end of brief cue presentation). In the Unpredictable condition of the NPU task, shocks are fully unpredictable. Patients with posttraumatic stress and panic disorders exhibit selectively increased startle potentiation during unpredictable but not predictable shock in the NPU task22,23. In other work, medications prescribed to treat anxiety have a greater effect on startle potentiation during unpredictable shock than during predictable shock in the NPU task24. In research on the anxiolytic effects of alcohol, Moberg and Curtin4 used the NPU task to demonstrate that a moderate dose of alcohol selectively reduces startle potentiation during threat of unpredictable but not predictable shock. Uncertainty is multifaceted and shocks in the unpredictable condition of the NPU task are uncertain in regards to both IF they are to occur (probability uncertainty) and WHEN they occur (temporal uncertainty). Many theories suggest that the WHEN dimension of uncertainty is critical in producing anxiety19. However, data from Curtin et al.5 suggests a common mechanism for the elicitation of anxiety across various types of uncertainty. The Threat Probability task described here manipulates uncertainty about IF a shock will occur while holding all other dimensions of uncertainty constant thus making clear what aspect of uncertainty is responsible for the effects the task presents. Tasks that use startle potentiation to cued threat are flexible and can also be modified by affective scientists to manipulate uncertainty about WHERE the shocks are going to occur25 and HOW BAD they will be7,26. Of all of these tasks, the Threat Probability Task is one of the easiest to interpret due to its focus on one dimension of uncertainty and most straightforward to implement due to its inclusion of only two threat uncertainty variants (low probability and high probability shock).
The Threat Probability Task
In the Threat Probability Task, the participant is seated approximately 1.5 m from a cathode ray tube (CRT) monitor. Threat cues are displayed on the monitor for 5 sec each with a variable duration ITI (range = 15-20 sec). Threat cues are divided into sets of two shock threat conditions and one no-threat condition (see Figure 1). In both threat conditions shocks of 200 msec duration are delivered at 4.5 sec into cue presentation times to the participant&#8217;s fingers. In the 100% threat probability condition, shocks are delivered during presentation of every cue. In 20% threat probability condition, shocks are delivered during presentation of 1 out of every 5 cues. The participant sees two sets (15 cues total) of each threat probability condition. The participant also sees two neutral sets of cues that signal no threat (no-threat cues; 15 cues total). Text displayed on the monitor informs the participant of the next set type. A label for the set type is displayed during the entire set in the upper left corner of the monitor. Different color cues are used for each condition to facilitate awareness of each set for the participant. Throughout the task, the stimulus presentation program presents the participant with acoustic startle probes in the form of 50 msec bursts of 102 dB white noise with near instantaneous rise time delivered through headphones. Acoustic startle probes are delivered at 4 sec into the presentation of a subset of the cues. Additional probes are delivered at 13 sec and 15 sec post cue offset during the ITIs to decrease the predictability of the probes. Before any presentation of visual stimuli, the task begins with the delivery of 3 acoustic startle probes to habituate the startle response immediately before main task measurement. Researchers balance the serial position of the acoustic startle probes across conditions within subjects in order to control for habituation and sensitization effects27,28. For an example of one fully counterbalanced series of trials for the Threat Probability Task see Supplementary Material.
The Threat Probability task has been used to demonstrate that low probability (uncertain) shock alone is sufficient to elicit anxiety and allow assessment of the anxiolytic effects of alcohol6. Preliminary research with dependent marijuana users suggests the Threat Probability Task can also be used to assess the effects of drug withdrawal29. Thus, the Threat Probability Task provides an easily implemented alternative to more expensive and less precise methods for the objective measure of distinct negative emotional states (e.g., anxiety and fear) for research on psychopathology, substance use/abuse, and broad affective science.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="63" rowspan="2" style="height:63px;width:216px;">Amplifier</td>
			<td rowspan="2" style="width:71px;">Numerous options</td>
			<td rowspan="2" style="width:119px;">N/A</td>
			<td rowspan="2" style="width:167px;">See Curtin, Lorenzo, and Allen (2007) for a list of vendors.&#160;&#160;</td>
		</tr>
		<tr height="21">
		</tr>
		<tr height="42">
			<td height="85" rowspan="2" style="height:85px;width:216px;">Small Ag/AgCl EMG Sensors</td>
			<td rowspan="2" style="width:71px;">Discount Disposables</td>
			<td rowspan="2" style="width:119px;">TDE-023-Y-ZZ-S</td>
			<td style="width:167px;">4mm, and 48in lead length</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.discountdisposables.com/</td>
		</tr>
		<tr height="42">
			<td height="85" rowspan="2" style="height:85px;width:216px;">Large Ag/AgCl EMG sensor</td>
			<td rowspan="2" style="width:71px;">Discount Disposables</td>
			<td rowspan="2" style="width:119px;">TDE-022-Y-ZZ-S</td>
			<td style="width:167px;">8mm, and 48in lead length</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.discountdisposables.com/</td>
		</tr>
		<tr height="21">
			<td height="64" rowspan="2" style="height:64px;width:216px;">Small electrode collars</td>
			<td rowspan="2" style="width:71px;">Discount Disposables</td>
			<td rowspan="2" style="width:119px;">TD-23</td>
			<td style="width:167px;">5mm</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.discountdisposables.com/</td>
		</tr>
		<tr height="21">
			<td height="64" rowspan="2" style="height:64px;width:216px;">Large electrode collars</td>
			<td rowspan="2" style="width:71px;">Discount Disposables</td>
			<td rowspan="2" style="width:119px;">TD-22&#160;&#160;</td>
			<td style="width:167px;">8mm</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.discountdisposables.com/</td>
		</tr>
		<tr height="211">
			<td height="211" style="height:211px;width:216px;">Shock box</td>
			<td style="width:71px;">Custom</td>
			<td style="width:119px;">Custom</td>
			<td style="width:167px;">See supplemental material for a circuit diagram for the custom shock box used by the Curtin laboratory. An example of a commerical shock box can be found at: http://www.psychlab.com/stim_SHK_shockers.html&#160;</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Alcohol pads</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">06-669-72</td>
			<td style="width:167px;">http://www.fishersci.com/ecomm/servlet/home?storeId=10652</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Exfoliant gel</td>
			<td style="width:71px;">Weaver and Company</td>
			<td style="width:119px;">NuPrep</td>
			<td style="width:167px;">http://www.weaverandcompany.com/index.html</td>
		</tr>
		<tr height="85">
			<td height="85" style="height:85px;width:216px;">Conductive Gel</td>
			<td style="width:71px;">Electro-Cap International</td>
			<td style="width:119px;">ECA E9</td>
			<td style="width:167px;">http://www.electro-cap.com/</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Gauze pads</td>
			<td style="width:71px;">Neuromedical Supplies</td>
			<td align="right" style="width:119px;">95000025</td>
			<td style="width:167px;">http://www.neuroscan.com/supplies.cfm</td>
		</tr>
		<tr height="85">
			<td height="85" style="height:85px;width:216px;">Blunt Needle</td>
			<td style="width:71px;">Electro-Cap International</td>
			<td style="width:119px;">E8B</td>
			<td style="width:167px;">http://www.electro-cap.com/</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Medical tape</td>
			<td style="width:71px;">Neuromedical Supplies</td>
			<td align="right" style="width:119px;">95000032</td>
			<td style="width:167px;">http://www.neuroscan.com/supplies.cfm</td>
		</tr>
		<tr height="42">
			<td height="64" rowspan="2" style="height:64px;width:216px;">Electrode Sterilizing Solution</td>
			<td rowspan="2" style="width:71px;">Emergency Medical Products:</td>
			<td rowspan="2" style="width:119px;">MX-2800</td>
			<td style="width:167px;">Gloves should be warn when handling metricide</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:167px;">http://www.buyemp.com</td>
		</tr>
		<tr height="126">
			<td height="169" rowspan="2" style="height:169px;width:216px;">Headphones</td>
			<td rowspan="2" style="width:71px;">Sennheiser</td>
			<td align="right" rowspan="2" style="width:119px;">4974</td>
			<td style="width:167px;">Head phones should be capable of repeatedly delivering startle probe&#8217;s at the level chosen by experimenters (e.g.,102 db)</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://en-us.sennheiser.com/</td>
		</tr>
		<tr height="84">
			<td height="127" rowspan="2" style="height:127px;width:216px;">Participant monitoring camera.</td>
			<td rowspan="2" style="width:71px;">PolarisUSA</td>
			<td rowspan="2" style="width:119px;">BC-660B</td>
			<td style="width:167px;">Infrared capable camera so participant can be monitored while lights are off in experiment room.</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.polaris.com/en-us/home.aspx</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Infrared panel</td>
			<td style="width:71px;">PolarisUSA</td>
			<td style="width:119px;">IR-TILE</td>
			<td style="width:167px;">http://www.polaris.com/en-us/home.aspx</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Video monitor for participant monitoring</td>
			<td style="width:71px;">Marshall Electronics</td>
			<td style="width:119px;">M-Pro CCTV 19</td>
			<td style="width:167px;">http://www.marshall-usa.com/IVS/monitors/M-Pro_CCTV_19.html</td>
		</tr>
		<tr height="42">
			<td height="85" rowspan="3" style="height:85px;width:216px;">Stimulus Computer</td>
			<td rowspan="3" style="width:71px;">Dell</td>
			<td rowspan="3" style="width:119px;">Dell Optiplex3010&#160;</td>
			<td style="width:167px;">Most modern computers appropriate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:167px;">http://www.dell.com/</td>
		</tr>
		<tr height="253">
			<td height="253" style="height:253px;width:216px;">Sound card (Stimulus computer)</td>
			<td style="width:71px;">Creative</td>
			<td style="width:119px;">70SB127000002</td>
			<td style="width:167px;">http://us.store.creative.com/Creative-Sound-Blaster-XFi-Titanium-HD/M/B0041OUA38.htm. The sound card delivers the startle probes. An example of a stand alone noise generator can be found at: http://www.psychlab.com/stim_TG_WN_sound.html#</td>
		</tr>
		<tr height="126">
			<td height="190" rowspan="2" style="height:190px;width:216px;">I/O card (Stimulus computer)</td>
			<td rowspan="2" style="width:71px;">Measurement Computing</td>
			<td rowspan="2" style="width:119px;">PCI-DIO24</td>
			<td style="width:167px;">I/O card allows control of shock box and communication of event markers (e.g., for startle probe occurrence) to data collection computer.</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:167px;">http://www.mccdaq.com/pci-data-acquisition/PCI-DIO24.aspx</td>
		</tr>
		<tr height="42">
			<td height="64" rowspan="2" style="height:64px;width:216px;">Stimulus control software</td>
			<td rowspan="2" style="width:71px;">Psychtoolbox</td>
			<td rowspan="2" style="width:119px;">N/A</td>
			<td style="width:167px;">Open source (free) toolbox based in Matlab</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:167px;">Psychtoolbox.org</td>
		</tr>
		<tr height="63">
			<td height="106" rowspan="2" style="height:106px;width:216px;">Computational platform for stimulus control and data reduction</td>
			<td rowspan="2" style="width:71px;">MathWorks</td>
			<td rowspan="2" style="width:119px;">N/A</td>
			<td style="width:167px;">Required to use Psychtoolbox and EEGLab (below)</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://www.mathworks.com/products/matlab/</td>
		</tr>
		<tr height="42">
			<td height="85" rowspan="3" style="height:85px;width:216px;">Data collection computer</td>
			<td rowspan="3" style="width:71px;">Dell</td>
			<td rowspan="3" style="width:119px;">Dell Optiplex3010</td>
			<td style="width:167px;">Most modern computers are appropriate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:167px;">http://www.dell.com/</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Psychophysiology acquisition software</td>
			<td style="width:71px;">Numerous options</td>
			<td style="width:119px;">N/A</td>
			<td style="width:167px;">See Curtin, Lorenzo, and Allen (2007) for a list of vendors.</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Stimulus Monitor</td>
			<td style="width:71px;">Acer</td>
			<td style="width:119px;">Acer AL1916W</td>
			<td style="width:167px;">http://us.acer.com/ac/en/US/content/group/monitors</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Data Collection Monitor</td>
			<td style="width:71px;">Acer</td>
			<td style="width:119px;">Acer AL1916W</td>
			<td style="width:167px;">http://us.acer.com/ac/en/US/content/group/monitors</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Participant CRT monitor</td>
			<td style="width:71px;">ViewSonic</td>
			<td style="width:119px;">P810</td>
			<td style="width:167px;">http://www.viewsonic.com/us/</td>
		</tr>
		<tr height="63">
			<td height="106" rowspan="2" style="height:106px;width:216px;">Data processing software</td>
			<td rowspan="2" style="width:71px;">EEGLab</td>
			<td rowspan="2" style="width:119px;">N/A</td>
			<td style="width:167px;">Open source (free) software package based in Matlab</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">http://sccn.ucsd.edu/eeglab/</td>
		</tr>
	</tbody>
</table>

using the threat probability task to assess anxiety and fear during uncertain and certain threat

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical components. Both anxiety and fear can be studied in the laboratory by measuring the potentiation of the startle reflex. The startle reflex is a defensive reflex that is potentiated when an organism is threatened and the need for defense is high. The startle reflex is assessed via electromyography (EMG) in the orbicularis oculi muscle elicited by brief, intense, bursts of acoustic white noise (i.e., &#8220;startle probes&#8221;). Startle potentiation is calculated as the increase in startle response magnitude during presentation of sets of visual threat cues that signal delivery of mild electric shock relative to sets of matched cues that signal the absence of shock (no-threat cues). In the Threat Probability Task, fear is measured via startle potentiation to high probability (100% cue-contingent shock; certain) threat cues whereas anxiety is measured via startle potentiation to low probability (20% cue-contingent shock; uncertain) threat cues. Measurement of startle potentiation during the Threat Probability Task provides an objective and easily implemented alternative to assessment of negative affect via self-report or other methods (e.g., neuroimaging) that may be inappropriate or impractical for some researchers. Startle potentiation has been studied rigorously in both animals (e.g., rodents, non-human primates) and humans which facilitates animal-to-human translational research. Startle potentiation during certain and uncertain threat provides an objective measure of negative affective and distinct emotional states (fear, anxiety) to use in research on psychopathology, substance use/abuse and broadly in affective science. As such, it has been used extensively by clinical scientists interested in psychopathology etiology and by affective scientists interested in individual differences in emotion.

The Threat Probability Task produces robust startle potentiation during both 100% (certain) probability and 20% (uncertain) probability threat cues (see Figure 6B). Previous results using this task show startle potentiation during the uncertain (20%) threat condition to be significantly increased above startle potentiation during high probability (100%) (certain) threat condition. Acute administration of a moderate does of alcohol (target blood alcohol concentration of 0.08%) produces selectively greater...

Watch this Scientific Journal Video about Using the Threat Probability Task to Assess Anxiety and Fear During Uncertain and Certain Threat at JoVE.com

Using the Threat Probability Task to Assess Anxiety and Fear During Uncertain and Certain Threat

Potentiation of the startle reflex is measured via electromyography of the orbicularis oculi muscle during low (uncertain) and high (certain) probability electric shock threat in the Threat Probability Task. This provides an objective measure of distinct negative emotional states (fear/anxiety) for research on psychopathology, substance use/abuse, and broad affective science.

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical ...

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Research

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Behavior

15.0K visualizações.  University of Wisconsin-Madison. Potentiation of the startle reflex is measured via electromyography of the orbicularis oculi muscle during low (uncertain) and high (certain) probability electric shock threat in the Threat Probability Task. This provides an objective measure of distinct negative emotional states (fear/anxiety) for research on psychopathology, substance use/abuse, and broad affective science. 