Download Developing Protocols to Study How Threats to

Developing Protocols to Study How Threats to the
Body are Detected and Capture Attention
Jennifer Roper, Jasmine Stephens, Suzanne van Arsdale, Dr. Dowman
Department of Psychology
Introduction
The ability to detect and orient towards threats to the body is critical for survival. Although
attentional bias towards threats to the body has been documented in many studies, its neural mechanisms
are largely unknown (see Mogg & Bradley 2003, 2004; and Öhman 2000 for reviews). Dowman has
reported electrophysiological and behavioral data suggesting threats to the body are detected by the dorsal
posterior insula. This threat detector activity is monitored by the medial prefrontal cortex, which signals
the lateral prefrontal to orient attention towards the threat (Dowman 2007a, 2007b). Artificial neural
network studies of this hypothesis have led to several unexpected predictions, such as the attentional bias
towards threat only being evident when the threat is presented outside the focus of attention (Dowman &
ben-Avraham 2008).
Threatening and non-threatening stimuli used by Dowman were strong and weak levels,
respectively, of electrical stimulation of the sural nerve (Dowman 2007a, 2007b). Consequently,
comparing threatening and non-threatening stimuli will be confounded by stimulus intensity. To alleviate
this confound, a protocol with a threatening and non-threatening stimuli of equal intensity was developed.
In this study, a trace classical conditioning paradigm was used to condition response to a weak electrical
stimulation (conditioned stimulus, CS) to equal the response of a strong electrical stimulation
(unconditioned stimulus, US). To accomplish this, threat was assigned to the weak levels of stimulation
by pairing them with a moderately painful stimulus. Two classical conditioning protocols were used:
discrimination training (Experiment 1) and paired vs. unpaired response (Experiment 2).
Methods: Experiments 1 and 2
Participants
The participants were 13 Clarkson University students (8 males, 5 females, mean age = 23.4, SD
= 6.4) who were paid for their participation. Prior to the experiment, each participant was given a detailed
explanation of the procedure and signed an informed consent document. The procedure was approved by
the Clarkson University Institutional Review Board.
Stimuli
The conditioned (CS) and unconditioned (US) stimuli were stimulation of the sural nerve at the
right ankle. Three stimulus levels were used, two of which were non-threatening: one stimulus produced a
light tapping sensation, the other produced a weak paresthesia sensation. The third stimulus was of a
strong, threatening level that produced a moderately painful sensation.
Recording Parameters
Conditioning was determined by measuring the spinal withdrawal reflex (R2) evoked by the sural
nerve electrical stimulus and by perceived unpleasantness of the conditioned stimuli.
Experiment 1: Discrimination Training
There were three conditions: habituation, acquisition and extinction. In habituation and extinction, the
CS+ and the CS- were presented alone, with only one type of CS presented in a trial. During acquisition,
the US followed the CS+ after a 500 ms stimulus onset asynchrony (SOA), whereas the CS- was given by
itself. The tap and paresthesia were pseudorandomly assigned to the CS+ and CS- and therefore
Jennifer Roper, Class of 2011
Jasmine Stephens: Class of 2010
Suzanne van Arsdale: Class of 2010
Robert Dowman
Honors Program
McNair scholar
Honors Program
Professor and Chair
Psychology
Psychology
Biomolec, Psychology, Chemistry and Biology
Department of Psychology
counterbalanced across subjects. If conditioning is successful, then the R2 and unpleasantness ratings will
be larger for the CS+ than the CS- during the acquisition phase.
Results
The R2 reflex amplitude evoked by the CS+ was slightly larger than that for the CS- during the
acquisition, but not during the extinction phase (Figure 1). Unpleasantness ratings did not appear to show
any conditioning effects, given there was no appreciable difference between the CS+ and CS- during the
acquisition phase (Figure 2). Conditioning was most likely inhibited due to poor discrimination between
the paresthesia and tapping sensation. It was noted that subjects had difficulty distinguishing between
CS+ and the CS-, which possibly interfered with conditioning. Due to unsuccessful conditioning with the
tapping CS and poor discrimination between conditioned stimuli, the tapping CS and discrimination
training were removed from the next experiment, and only the paresthesia was used as the CS in the trace
conditioning paradigm.
Figure 1
Average R2 reflex for CS- and CS+
Amplitude of R2 reflex (uV)
2.5
2
1.5
CS+
CS-
1
0.5
habituation
acquisition
extinction
0
1
2
3
Figure 2
Average unpleasantness ratings for CS+ and CS- in habituation,
acquistion and extinction
unpleasantness rating (0-100)
25
20
15
CS+
CS-
10
5
habituation
acquisition
extinction
0
1
2
3
Figure 2: Ratings are on a 100 mm visual analog scale. Maximum unpleasantness = 100
Jennifer Roper, Class of 2011
Jasmine Stephens: Class of 2010
Suzanne van Arsdale: Class of 2010
Robert Dowman
Honors Program
McNair scholar
Honors Program
Professor and Chair
Psychology
Psychology
Biomolec, Psychology, Chemistry and Biology
Department of Psychology
Experiment 2: Paired and Unpaired
The conditioned stimulus (CS) was weak paresthesia, the unconditioned stimulus (US)
moderately painful stimulation. There were four conditions: habituation, acquisition 1, acquisition 2, and
extinction. In the acquisition phases for the paired group, the US followed the CS by 500 ms. In the
unpaired group, the US randomly followed the CS 3.5 – 7.5 s with a mean of 5.4 s. Conditioning for the
paired and unpaired groups was measured via the R2 reflex amplitude and the perceived unpleasantness
rating.
Results
Figure 3. The average
R2 amplitudes for the
paired versus unpaired
groups, which showed a
small conditioning
effect.
Figure 4. The average
unpleasantness ratings
given by the subjects
were graphed and
determined to have no
conditioning effect.
The small R2 effect was slightly larger in the acquisition and even smaller in the extinction phase (Figure
3). The conditioning had no effect on the unpleasantness rating (Figure 4). If conditioning is successful,
then the R2 and unpleasantness ratings will be larger for the paired group than the unpaired group during
the acquisition phase. As seen in figures 3 and 4, this is clearly not the case.
Conclusions
Neither the Discrimination Training nor the Paired-Unpaired training resulted in assigning a
psychologically significant level of threat to the non-painful sural nerve stimuli. This protocol cannot,
Jennifer Roper, Class of 2011
Jasmine Stephens: Class of 2010
Suzanne van Arsdale: Class of 2010
Robert Dowman
Honors Program
McNair scholar
Honors Program
Professor and Chair
Psychology
Psychology
Biomolec, Psychology, Chemistry and Biology
Department of Psychology
therefore, be used to test the hypothesis generated by our artificial neural network model of threat
detection and orienting.
There are several reasons why conditioning was unsuccessful in the present study, but successful
in other studies using electrical stimuli as the CS and US (e.g. Diesch & Flor 2007). An important point is
other studies used delay conditioning, where the CS and US temporally overlap, in contrast to trace
conditioning as used in the present study, where the stimuli do not overlap. It is well known that trace
conditioning is not as effective as delay conditioning (Flaherty 1985). Another fundamental difference
between the successful conditioning studies and the present study is the duration of the stimuli: Diesch
and Flor (2007) used a US with a duration of 704 milliseconds, whereas our US was presented for only 17
milliseconds. These experimental factors could have led to unappreciable conditioning in the present
study.
References
Diesch, E., & Flor, H. (2007) Alteration in the response properties of primary somatosensory cortex
related to differential aversive pavlovian conditioning. Pain, 131, 171-180.
Dowman, R. (2007a). Neural mechanisms of detecting and orienting attention toward unattended
threatening somatosensory targets. I. Intermodal effects. Psychophysiology, 44, 407-419.
Dowman, R. (2007b). Neural mechanisms of detecting and orienting attention toward unattended
threatening somatosensory targets. II. Intensity effects. Psychophysiology, 44, 420-430.
Dowman, R. & ben-Avraham (2008). An artificial neural network model of orienting attention toward
threatening somatosensory stimuli. Psychophysiology, 45, 229-239.
Flaherty, C.F. (1985) Animal Learning and Cognition. New York: Alfred A. Knopf.
Lang, P.J., Bradley, M.M., Cuthbert, B.N. (1990) Emotion, attention and the startle reflex. Psychological
Review, 97, 377-395).
Mogg, K., Bradley, B.P. (2003) In: (P. Philippot, R.S. Feldman & E.J. Coats (Eds.) Nonverbal Behavior
In Clinical Settings. London: Oxford University Press, 127-143.
Mogg, K., & Bradley, B.P. (2004) A cognitive-motivational perspective on the processing of threat
information in anxiety. In: Cognition, Emotion and Psychopathology. Theoretical, Empirical and
Clinical Directions (J. Yiend, Ed.) New York: Cambridge University Press, 68-85.
Öhman, A. (2000) Fear and anxiety: evolutionary, cognitive, and clinical perspectives. In: M. Lewis &
J.M. Haviland-Jones (Eds.) Handbook of Emotions, New York: Guilford Press, pp. 573-593.
Jennifer Roper, Class of 2011
Jasmine Stephens: Class of 2010
Suzanne van Arsdale: Class of 2010
Robert Dowman
Honors Program
McNair scholar
Honors Program
Professor and Chair
Psychology
Psychology
Biomolec, Psychology, Chemistry and Biology
Department of Psychology