Startle Conditioning Research Articles

Mapping subcortical motor pathways in humans with startle-conditioned TMS

Subcortical motor pathways, such as the reticulospinal tract, are critical for producing and modulating voluntary movements and have been implicated in neurological conditions. Previous research has described the presence of ipsilateral motor evoked potentials (iMEPs) in the arm to transcranial magentic stimulation (TMS), and suggested they could be mediated by the uncrossed corticospinal tract or by ipsilateral cortico-reticulospinal connections. Here, we sought to elucidate the role of the reticulospinal tract in mediating iMEPs by assessing their modulation by a startling acoustic stimulus and mapping these responses across multiple upper limb effectors. In a first experiment, we delivered TMS at various intervals (1, 5, 10 and 15 ms) after a startling acoustic stimulus, known to excite the reticular formation, to elicit iMEPs in the arm. We observed robust facilitation of iMEP area when startle conditioning preceded TMS at the 10 ms interval. In a second experiment, we replicated our findings showing that both the area and number of iMEPs in the arm increases with startle conditioning. Using this technique, we observed that iMEPs are more prominent in the arm compared with the hand. In a third experiment, we also observed greater presence of iMEPs in flexor compared with extensor muscles. Together, these findings are consistent with properties of the reticulospinal tract observed in animals, suggesting that iMEPs primarily reflect reticulospinal activity. Our findings imply that we can use this approach to track modulation of cortico-reticulospinal excitability following interventions or neurological conditions where the reticulospinal tract may be involved in motor recovery.

Understanding emotional responses to visual aesthetic artefacts: the SECMEA mechanisms

While many models attempt to explain the aesthetic experience, most limit themselves to art as their focal point and only a few look into why we arrive at a certain response to a visual aesthetic object. This article attempts to offer an extension to the current models by focusing on the mechanisms that induce emotions in relation to visual aesthetic objects. It takes Juslin’s (2013) BRECVEM mechanisms – developed for the domain of music – as its basis. In this article, Juslin’s mechanisms are adapted to the visual domain, resulting in six different emotion-evoking mechanisms: startle reflex, evaluative conditioning, emotional contagion, mental imagery, syntactic expectancy and external appraisal. The authors give an overview of frameworks and empirical studies, demonstrating each of these mechanisms in relation to visual aesthetic objects (visual art as well as advertising and product design). The article’s focus on emotion-inducing mechanisms and existing empirical research provides a basis for improving empirical testing of emotional responses to a broad range of visual aesthetic objects.

A Flexible Platform for Monitoring Cerebellum-Dependent Sensory Associative Learning.

Climbing fiber inputs to Purkinje cells provide instructive signals critical for cerebellum-dependent associative learning. Studying these signals in head-fixed mice facilitates the use of imaging, electrophysiological, and optogenetic methods. Here, a low-cost behavioral platform (~$1000) was developed that allows tracking of associative learning in head-fixed mice that locomote freely on a running wheel. The platform incorporates two common associative learning paradigms: eyeblink conditioning and delayed tactile startle conditioning. Behavior is tracked using a camera and the wheel movement by a detector. We describe the components and setup and provide a detailed protocol for training and data analysis. This platform allows the incorporation of optogenetic stimulation and fluorescence imaging. The design allows a single host computer to control multiple platforms for training multiple animals simultaneously.

Startle Increases the Incidence of Anticipatory Muscle Activations but Does Not Change the Task-Specific Muscle Onset for Patients After Subacute Stroke.

Objectives: To demonstrate the task-specificities of anticipatory muscle activations (AMAs) among different forward-reaching tasks and to explore the StartleReact Effect (SE) on AMAs in occurrence proportions, AMA onset latency or amplitude within these tasks in both healthy and stroke population.Methods: Ten healthy and ten stroke subjects were recruited. Participants were asked to complete the three forward-reaching tasks (reaching, reaching to grasp a ball or cup) on the left and right hand, respectively, with two different starting signals (warning-Go, 80 dB and warning-startle, 114 dB). The surface electromyography of anterior deltoid (AD), flexor carpi radialis (FCR), and extensor carpi radialis (ECR) on the moving side was recorded together with signals from bilateral sternocleidomastoid muscles (SCM), lower trapezius (LT), latissimus dorsi (LD), and tibialis anterior (TA). Proportions of valid trials, the incidence of SE, AMA incidence of each muscle, and their onset latency and amplitude were involved in analyses. The differences of these variables across different move sides (healthy, non-paretic, and paretic), normal or startle conditions, and the three tasks were explored. The ECR AMA onset was selected to further explore the SE on the incidence of AMAs.Results: Comparisons between move sides revealed a widespread AMA dysfunction in subacute stroke survivors, which was manifested as lower AMA onset incidence, changed onset latency, and smaller amplitude of AMAs in bilateral muscles. However, a significant effect of different tasks was only observed in AMA onset latency of muscle ECR (F = 3.56, p = 0.03, η2p = 0.011), but the significance disappeared in the subsequent analysis of the stroke subjects only (p > 0.05). Moreover, the following post-hoc comparison indicated significant early AMA onsets of ECR in task cup when comparing with reach (p < 0.01). For different stimuli conditions, a significance was only revealed on shortened premotor reaction time under startle for all participants (F = 60.68, p < 0.001, = 0.056). Furthermore, stroke survivors had a significantly lower incidence of SE than healthy subjects under startle (p < 0.01). But all performed a higher incidence of ECR AMA onset (p < 0.05) than with normal signal. In addition, the incidence of ECR AMAs of both non-paretic and paretic sides could be increased significantly via startle (p ≤ 0.02).Conclusions: Healthy people have task-specific AMAs of muscle ECR when they perform forward-reaching tasks with different hand manipulations. However, this task-specific adjustment is lost in subacute stroke survivors. SE can improve the incidence of AMAs for all subjects in the forward-reaching tasks involving precision manipulations, but not change AMA onset latency and amplitude.

Effects of Acute Psychological and Physiological Stress on Rock Climbers.

Background: The aim of this study was to assess the effects that psychological and physiological stressors have on indoor rock climbers, as well as to identify sex differences. Methods: 14 intermediate rock climbers participated in the study, 10 males and 4 females. Mean age was 31 ± 8 years for males and 21 ± 2 years for females. Day 1 consisted of test familiarization and baseline measurements. Day 2 included two test conditions, startle and fatigue, separated by 20 min. In the startle condition, participants had to lead climb a route, and a loud audio stimulus was presented near the top of the climb. In the fatigue condition, participants were required to climb as fast as they could until muscular failure. The competitive state anxiety inventory second review (CSAI-2R) questionnaire was used to assess somatic anxiety, cognitive anxiety, and self-confidence. The four-square step test (FSST) was used to assess motor control, and cortisol levels were acquired via passive drool (PD). Results: Cortisol concentrations were highest in the pre-startle condition (1.72 μg/dL ± 0.66), and values decreased post-startle (1.67 μg/dL ± 0.74) and post-fatigue (1.42 μg/dL ± 0.72). However, cortisol concentrations increased post-startle in females (1.57 μg/dL ± 0.96). Somatic anxiety in males was significantly higher post-startle (16.36 ± 5.54) than pre-startle (14.23 ± 5.09). Females had significantly higher somatic anxiety post-startle (18.00 ± 8.76), and they had lower self-confidence levels (30.00 ± 5.89) than males. Conclusions: There are differences in the way that males and females prepare and respond to stressful situations. Furthermore, time of day may have had a significant impact on cortisol concentrations.

1074 Fear Reactivity And Sleep In Trauma-Exposed Males And Females With And Without PTSD

Abstract Introduction Sleep disturbance is considered central to mechanisms of PTSD development and maintenance, and fear learning protocols have been used as laboratory models to understand PTSD disease mechanisms. Some research indicates that fear learning may influence subsequent sleep, especially REM sleep, and that sleep may influence subsequent extinction. In this study, we examined the relationship of startle reactivity during conditioning and later extinction with objectively-measured sleep in PTSD-positive and negative subjects. Methods These analyses were performed as part of a larger study of PTSD and sleep. Thirty-four (34) trauma-exposed male and female participants with and without PTSD completed a fear-potentiated startle conditioning procedure at 9:45am, followed by a PSG-monitored nap (13:30-15:30), followed by an extinction protocol at 4:30pm. All visits were preceded by an adaptation nap visit at least 7 days prior. Eye-blink EMG was used to measure startle reactivity. Mixed-model analyses were performed in SPSS. Results PTSD-positive subjects had higher REM sleep duration (p&amp;lt;.05) and a trend towards shorter REM sleep latency (p=.06). There were no other group or sex effects on standard PSG sleep parameters. During conditioning, PTSD-positive status was associated with higher startle reactivity across stimulus types (p&amp;lt;.01), driven by increased reactivity in PTSD-positive vs. PTSD-negative females. A PTSD x sex interaction effect on startle reactivity showed the opposite effect in males (p&amp;lt;.01). Higher startle reactivity during conditioning predicted longer sleep latency during the subsequent nap (p&amp;lt;.05), but reactivity during conditioning and extinction did not otherwise show a relationship to standard PSG sleep measures. Conclusion These findings are consistent with previous research indicating REM sleep abnormalities as well as heightened fear responses in PTSD. While the observed relationship between higher startle and longer sleep latency is consistent with studies indicating that stress affects subsequent sleep, further research in larger samples is needed to understand causal mechanisms and to advance our understanding of sleep-PTSD mechanisms. Support VA Career Development Award-5IK2CX000871-05

Negative Emotion and Joint-Stiffness Regulation Strategies After Anterior Cruciate Ligament Injury.

Fear of reinjury after an anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with persistent deficits in knee function and subsequent injury. However, the effects of negative emotion on neuromuscular-control strategies after an ACL injury have remained unclear. To identify how negative emotional stimuli affect neural processing in the brain and muscle coordination in patients after anterior cruciate ligament reconstruction compared with healthy control participants. Case-control study. Neuromechanics laboratory. Twenty patients after unilateral anterior cruciate ligament reconstruction and 20 healthy recruits. Electrocortical θ (4-8 Hz) activity (event-related synchronization, % increased power relative to a nonactive baseline) at selected electrodes placed at the frontal (F3, Fz, F4) and parietal (P3, Pz, P4) cortices using electroencephalography, neurophysiological cardiac changes (beats/min), and subjective fear perceptions were measured, along with joint stiffness (Nm/°/kg) with and without an acoustic stimulus in response to 3 types of emotionally evocative images (neutral, fearful, and knee-injury pictures). Both groups had greater frontoparietal θ power with fearful pictures (Fz: 35.9% ± 29.4%; Pz: 81.4% ± 66.8%) than neutral pictures (Fz: 24.8% ± 29.7%, P = .002; Pz: 64.2 ± 54.7%, P = .024). The control group had greater heart-rate deceleration with fearful (-4.6 ± 1.4 beats/min) than neutral (-3.6 ± 1.3 beats/min, P < .001) pictures, whereas the ACLR group exhibited decreased heart rates with both the fearful (-4.6 ± 1.3 beats/min) and injury-related (-4.4 ± 1.5 beats/min) pictures compared with neutral pictures (-3.4 ± 1.4 beats/min, P < .001). Furthermore, during the acoustic startle condition, fearful pictures increased joint stiffness (Nm/°/kg) in the ACLR group at the midrange (0°-20°: 0.027 ± 0.02) and long range (0°-40°: 0.050 ± 0.02) compared with the neutral pictures (0°-20°: 0.017 ± 0.01, P = .024; 0°-40°: 0.043 ± 0.02, P = .014). Negative visual stimuli simultaneously altered neural processing in the frontoparietal cortices and joint-stiffness regulation strategies in response to a sudden perturbation. The adverse effects of fear on neuromuscular control may indicate that psychological interventions should be incorporated in neuromuscular-control exercise programs after ACL injury.

Autonomic responses to fear conditioning among women with PTSD and dissociation.

Individuals with posttraumatic stress disorder (PTSD) demonstrate alterations in autonomic responses to fear conditioning, such as exaggerated startle and poor fear inhibition. However, there is a paucity of research on fear conditioning among individuals with PTSD and dissociative symptoms, which represents 10-30% of those with PTSD. The current study used a fear-potentiated startle (FPS) conditioning paradigm to examine autonomic responses among women with PTSD and a range of dissociative symptoms. Participants included 39 women with PTSD and dissociation, and 53 women with PTSD with unknown levels of dissociation. The FPS paradigm consisted of conditioned stimuli associated and not associated with an aversive unconditioned stimulus. FPS response (eyeblink startle), electrocardiogram (ECG), and skin conductance response (SCR) were collected during the FPS paradigm. Compared to the PTSD-unknown dissociation sample, the PTSD-dissociation sample demonstrated significantly lower FPS during the last block of conditioning. Among the PTSD-dissociation sample, higher dissociation scores were associated with decreased FPS and SCR, and higher respiratory sinus arrhythmia (derived from ECG). Results suggest that autonomic responses to fear conditioning differ depending on the presence and severity of dissociative symptoms. Given that treatment response may differ depending on dissociative symptoms, it is important to understand the mechanisms that underlie different subtypes of PTSD and that may affect treatment response and outcome.

An acoustic startle alters knee joint stiffness and neuromuscular control.

Growing evidence suggests that the nervous system contributes to non-contact knee ligament injury, but limited evidence has measured the effect of extrinsic events on joint stability. Following unanticipated events, the startle reflex leads to universal stiffening of the limbs, but no studies have investigated how an acoustic startle influences knee stiffness and muscle activation during a dynamic knee perturbation. Thirty-six individuals were tested for knee stiffness and muscle activation of the quadriceps and hamstrings. Subjects were seated and instructed to resist a 40-degree knee flexion perturbation from a relaxed state. During some trials, an acoustic startle (50 ms, 1000 Hz, 100 dB) was applied 100 ms prior to the perturbation. Knee stiffness, muscle amplitude, and timing were quantified across time, muscle, and startle conditions. The acoustic startle increased short-range (no startle: 0.044 ± 0.011 N·m/deg/kg; average startle: 0.047 ± 0.01 N·m/deg/kg) and total knee stiffness (no startle: 0.036 ± 0.01 N·m/deg/kg; first startle 0.027 ± 0.02 N·m/deg/kg). Additionally, the startle contributed to decreased [vastus medialis (VM): 13.76 ± 33.6%; vastus lateralis (VL): 6.72 ± 37.4%] but earlier (VM: 0.133 ± 0.17 s; VL: 0.124 ± 0.17 s) activation of the quadriceps muscles. The results of this study indicate that the startle response can significantly disrupt knee stiffness regulation required to maintain joint stability. Further studies should explore the role of unanticipated events on unintentional injury.

Fear conditioning of SCR but not the startle reflex requires conscious discrimination of threat and safety

There is conflicting evidence as to whether awareness is required for conditioning of the skin conductance response (SCR). Recently, Schultz and Helmstetter (2010) reported SCR conditioning in contingency unaware participants by using difficult to discriminate stimuli. These findings are in stark contrast with other observations in human fear conditioning research, showing that SCR predominantly reflects contingency learning. Therefore, we repeated the study by Schultz and Helmstetter and additionally measured conditioning of the startle response, which seems to be less sensitive to declarative knowledge than SCR. While we solely observed SCR conditioning in participants who reported awareness of the contingencies (n = 16) and not in the unaware participants (n = 18), we observed startle conditioning irrespective of awareness. We conclude that SCR but not startle conditioning depends on conscious discriminative fear learning.

Fear-Conditioning Mechanisms Associated with Trait Vulnerability to Anxiety in Humans

SummaryInvestigations of fear conditioning in rodents and humans have illuminated the neural mechanisms underlying cued and contextual fear. A critical question is how personality dimensions such as trait anxiety act through these mechanisms to confer vulnerability to anxiety disorders, and whether humans' ability to overcome acquired fears depends on regulatory skills not characterized in animal models. In a neuroimaging study of fear conditioning in humans, we found evidence for two independent dimensions of neurocognitive function associated with trait vulnerability to anxiety. The first entailed increased amygdala responsivity to phasic fear cues. The second involved impoverished ventral prefrontal cortical (vPFC) recruitment to downregulate both cued and contextual fear prior to omission (extinction) of the aversive unconditioned stimulus. These two dimensions may contribute to symptomatology differences across anxiety disorders; the amygdala mechanism affecting the development of phobic fear and the frontal mechanism influencing the maintenance of both specific fears and generalized anxiety.

Auditory Startle Alters the Response of Human Subjects Exposed to a Single Whiplash-like Perturbation

Human volunteers were exposed to a single whiplash-like perturbation. To determine how muscle and kinematic responses are affected by the superposition of a rear-end collision and loud startling noise. Many whiplash studies use forward perturbations without reproducing the sound of a car crash. Loud sounds are known to evoke startle responses in the neck muscles and therefore could affect whiplash injuries. Sixty-five subjects (30 female, 35 male) were exposed to a single forward horizontal perturbation. Head and torso kinematics, and electromyographic activity in the sternohyoid, sternocleidomastoid, scalenus, and cervical paraspinal muscles were measured. Two awareness conditions (deceived and unaware subjects) nested in two startle conditions (with or without a 40 milliseconds, 124 dB sound) were tested. Startle and gender affected the amplitude and timing of numerous kinematic and muscle variables. Awareness affected only one muscle variable. Startled individuals exhibited greater peak head and trunk accelerations, increased activity of the cervical paraspinal muscles, and a reduced head retraction and trunk angle. An acoustic startle alters the neck muscle and kinematic responses and may be as important as gender in the genesis of whiplash injury.

Cultures of Moderation and Expression: Emotional Experience, Behavior, and Physiology in Chinese Americans and Mexican Americans.

Ethnographic accounts suggest that emotions are moderated in Chinese cultures and expressed openly in Mexican cultures. The authors tested this notion by comparing subjective, behavioral, and physiological aspects of emotional responses to 3 (warned, unwarned, instructed to inhibit responding) aversive acoustic startle stimuli in 95 Chinese Americans and 64 Mexican Americans. Subjective reports were consistent with ethnographic accounts; Chinese Americans reported experiencing significantly less emotion than Mexican Americans across all 3 startle conditions. Evidence from a nonemotional task suggested that these differences were not artifacts of cultural differences in the use of rating scales. Few cultural differences were found in emotional behavior or physiology, suggesting that these aspects of emotion are less susceptible to cultural influence.

Postural and eye-blink indices of the defensive startle reflex

Postural and eye-blink reactions to acoustic startle probes were examined in 24 volunteers, who completed two blocked conditions (baseline, startle). A postural reaction during the startle condition demonstrated a reflexive movement in the anterior–posterior direction, which was not observed during the baseline condition. This reflexive response was positively associated with the eye-blink reflex, such that larger blink magnitude related to greater posterior movement. These findings were not observed for postural movements in the medial–lateral direction. The results suggest that a measurable postural reaction may be observed following a startling acoustic stimulus, which may reflect generalized bodily flexion associated with a preparatory behavioral response.

Startle response is dishabituated during a reaction time task.

Recent experiments pairing a startling stimulus with a simple reaction time (RT) task have shown that when participants are startled, a prepared movement may be triggered earlier in comparison to voluntary initiation (Carlsen et al. 2003, in press; Siegmund et al. 2001; Valls-Solé et al. 1999). The use of this paradigm in experiments may provide new insights into processes that control rapid voluntary actions. However, because the startle response habituates with repeated exposure to the startling stimulus, its use in experiments may be limited. Previously Brown et al. (1991) and later Siegmund et al. (2001) noted that individuals habituate to a startling stimulus at different rates depending on the required activity level of the participant in the task. The present experiment was designed to determine the rate at which participants habituate to a startle during the completion of a RT task. Participants completed 100 trials in which an active wrist extension to a target was performed as fast as possible following an auditory tone. An unexpected 124 dB auditory startle stimulus accompanied the imperative stimulus in 20 of these trials. For the duration of the experiment, startle response electromyographic (EMG) activity continued to be produced in the sternocleidomastoid muscle (SCM) indicating that habituation was not complete after 20 startle trials. Furthermore RT in the startle condition was significantly shorter than control RT. However, findings indicate that when a measurable EMG burst in the SCM was present, RT was significantly shorter than when no SCM burst was present.

Differential startle reactivity following central CCK-8S and systemic boc CCK-4 administration in mice: Antecedent stressor history and testing condition.

The influence of intraventricular cholecystokinin-8S (CCK-8S) and systemic N-t-Boc-Trp-Met-Asp-Phe-amide (Boc CCK-4) was evaluated in the acoustic and fear-potentiated startle paradigms in CD-1 mice. In the light + tone startle condition. CCK-8S increased startle 168 hr after administration, compared with saline. In the tone startle condition, CCK-8S decreased startle immediately and 24 hr after administration, compared with saline. Among nonshocked mice, CCK-8S increased startle at 48 and 168 hr, compared with saline. In the light + tone condition, 5 microg Boc-CCK-4 did not influence startle, whereas 15 microg Boc CCK-4 decreased startle immediately, 24 hr, and 48 hr following administration. Results demonstrate that antecedent environmental experiences interact with subsequent pharmacological challenges in provoking the temporal expression of alterations in startle magnitude.

Contextual fear-potentiated startle conditioning in humans: Replication and extension

Contextual fear-potentiated startle conditioning in humans: Replication and extension

Contextual fear‐potentiated startle conditioning in humans: Replication and extension

Contextual fear conditioning was examined using the startle reflex in two groups of participants over two sessions separated by 1/2 h. The conditioned stimulus (CS) was paired (paired group) or not (unpaired group) with an unpleasant shock during conditioning. The paired group showed conditioning to the CS that was well retained over the retention interval. Session I intertrial interval startles--a measure of contextual conditioning--were greater in the unpaired compared to the paired group. Context conditioning was retained in Session 2 and was present before the shock electrodes were attached. Self-rating of state anxiety, arousal, and pleasure indicated differential changes in mood from Session 1 to Session 2 in the two groups, with the unpaired group showing relatively greater negative affects compared to the paired group. These results indicate that unpredictable shocks lead to greater context conditioning as measured by startle and self-reports.

Laying hen behavior. 1. Effects of cage type and startle stimuli

The well-being of commercial laying hens plays an important role in egg production. Behaviors such as pacing, displaced preening, increased aggression, and redirected activities have been associated with stress in poultry. This study was conducted to determine whether two strains of commercial layers, reported to differ in level of excitability, behave differently in two types of commercial cages. DeKalb Delta and Hy-Line W36 hens, 40 to 45 wk of age, were housed six to eight per cage in open or solid-sided cages, at an equal density between cages. For each strain, there were six cages per cage type for a total of 24 cages. In the first five experiments, behavioral data were obtained at a distance of 1 m by instantaneous or scan sampling. These experiments included hen behavior in both types of cages with and without the presence of frustrating or startle conditions. Some significant differences in behavior existed within experiments but not consistently among all experiments. Sampling method did not affect reliability of data collection. Two trials were then conducted to determine whether the length of time to return to normal activity after a startle stimulus is influenced by the cage type or strain. In the first startle experiment, DeKalb hens returned to normal activity more quickly than did Hy-Line hens (P = 0.07); this strain difference was not found when the experiment was repeated. Cage type did not appear to affect the behavior of birds adversely, although neither cage type appeared to confer an advantage. No clear differences were found in behavior by strain or by strain within cage.

Acoustic Startle and Fear-Potentiated Startle in Alcohol-Preferring (P) and -Nonpreferring (NP) Lines of Rats

The objective of the present study was to determine whether alcohol-preferring P and -nonpreferring NP rats differ in their acoustic startle response and in fear-potentiated startle. In Experiment 1, male P and NP rats were tested on the startle response to acoustic stimuli ranging from 90–115 dB. Experiments 2 and 3 examined fear-potentiated startle and extinction of the response. In Experiment 2, rats received two light foot shock training sessions separated by 3–4 h. Testing consisted of ten acoustic startle (115 dB) and fear-potentiated startle (light preceding the acoustic startle) presentations administered every 24 h for 9 consecutive days. To test potentiated startle learning under reduced training conditions, a single training session was administered in Experiment 3, and a single within-session extinction test of 50 startle and 50 potentiated startle trials occurred the following day. Results of Experiment 1 indicated that P and NP rats did not differ in startle at any of the acoustic intensities tested. Following fear-potentiated startle conditioning in Experiment 2, however, both acoustic startle and potentiated startle responding were consistently greater in P than NP rats over most of the first 6 test days with P rats having approximately a 100% greater acoustic startle and 50–100% greater potentiated startle response. Moreover, following a single training session in Experiment 3, only P rats showed significant fear-conditioned startle. Additionally, P rats exhibited a 50–100% elevated acoustic startle response over that observed in NP rats. Taken together, the data indicate that, although experimentally naive male P and NP rats show similar acoustic startle responses, P rats become more responsive to both startle-alone and potentiated startle stimuli following fear conditioning. The change in general startle reactivity of the P rat following aversive conditioning, along with facilitated light foot shock learning, suggests that stress exposure may be an important variable in examining associations between anxiety and alcohol drinking behavior.