Holger Hecht

Brain activation to phobia-related pictures in spider phobic humans: an event-related functional magnetic resonance imaging study

Using event-related functional magnetic resonance imaging we investigated blood oxygen level dependent brain activation in spider phobic and non-phobic subjects while exposed to phobia-related pictures (spiders) and non-phobia-related pictures (snakes and mushrooms). In contrast to previous studies, we show significantly increased amygdala activation in spider phobics, but not in controls, during presentation of phobia-relevant visual stimuli. Furthermore, phobia-specific increased activation was also found in the insula, the orbitofrontal cortex and the uncus. Our study confirms the role of the amygdala in fear processing and provides insights into brain activation patterns when animal phobics are confronted with phobia-related stimuli.

Eye Movements and Behavioral Responses to Threatening and Nonthreatening Stimuli During Visual Search in Phobic and Nonphobic Subjects

Spider-phobic and nonphobic subjects searched for a feared/fear-relevant (spider) or neutral target (mushroom) presented in visual matrices of neutral objects (flowers). In half of the displays, the mushroom target was paired with a spider distractor, or a spider target was paired with a mushroom distractor. Although all subjects responded faster to the neutral target than to the feared/fear-relevant target, phobics were slower to respond than nonphobics when a mushroom target was presented with a spider distractor. Their eyes appeared to be drawn to the feared distractor before fixating neutral targets. A further experiment indicated no group differences when subjects merely judged the homogeneity of matrices. Thus, threat seems to capture the attention of phobics only when it is part of a background that subjects are explicitly instructed to ignore.

Why humans deviate from rational choice

Rational choice theory predicts that humans always optimize the expected utility of options when making decisions. However, in decision-making games, humans often punish their opponents even when doing so reduces their own reward. We used the Ultimatum and Dictator games to examine the affective correlates of decision-making. We show that the feedback negativity, an event-related brain potential that originates in the anterior cingulate cortex that has been related to reinforcement learning, predicts the decision to reject unfair offers in the Ultimatum game. Furthermore, the decision to reject is positively related to more negative emotional reactions and to increased autonomic nervous system activity. These findings support the idea that subjective emotional markers guide decision-making and that the anterior cingulate cortex integrates instances of reinforcement and punishment to provide such affective markers.

The influence of the magnitude, probability, and valence of potential wins and losses on the amplitude of the feedback negativity.

We assessed the influence of the variables outcome potential, feedback valence, magnitude, and probability on the amplitude of the feedback negativity (FN). Outcome potential was defined as the a priori valence of an upcoming feedback, that is, is there a potential win or potential loss? All these variables have been studied previously, although never together, but the findings have been contradictory. We analyzed the event-related potential (ERP) after feedback presentation in a reinforcement-learning task to examine the effects of all the variables on feedback negativity. Our results show that outcome potential, feedback valence, probability, and magnitude all influence feedback related ERPs. Taken together, the findings suggest that ERPs in the time range of the feedback negativity are primarily driven by positive outcomes (reinforcement) rather than negative outcomes (punishment).

Laser-evoked potentials to noxious stimulation during hypnotic analgesia and distraction of attention suggest different brain mechanisms of pain control

Psychological accounts of hypnosis have hypothesized that hypnosis and attention might share similar mechanisms and that hypnosis simply represents an extensive state of reduced attention. This assumption implies that reports of pain and electrocortical brain responses to painful stimulation should be similarly reduced when subjects are exposed to suggestions of hypnotic analgesia (HA) or requested to distract their attention from painful stimuli (distraction of attention: DA) as compared to a control condition (CC). To test this hypothesis, we recorded event-related electrical brain potentials to noxious laser-heat stimuli and pain reports during HA, DA, and CC from subjects highly susceptible to hypnotic suggestions. Pain reports were significantly reduced during HA and DA as compared to CC. The amplitudes of the late laser-evoked brain potential (LEP) components N200 and P320 were also significantly smaller during DA than during CC. However, no significant difference of these late LEP amplitudes was obtained for HA as compared to CC. Results indicate that hypnotic analgesia and distraction of attention represent different mechanisms of pain control and involve different brain mechanisms.

Acupuncture Decreases Somatosensory Evoked Potential Amplitudes to Noxious Stimuli in Anesthetized Volunteers

The effect of acupuncture on pain perception is controversial. Because late amplitudes of somatosensory evoked potentials (SEPs) to noxious stimuli are thought to correlate with the subjective experience of pain intensity, we designed this study to detect changes of these SEPs before and after acupuncture in a double-blinded fashion. Sixteen volunteers were anesthetized by propofol and exposed to painful electric stimuli to the right forefinger. Then, blinded to the research team, the acupuncture group (n = 8) was treated with electric needle acupuncture over 15 min at analgesic points of the leg, whereas the sham group (n = 8) received no treatment. Thereafter, nociceptive stimulation was repeated. SEPs were recorded during each noxious stimulation from the vertex Cz, and latencies and amplitudes of the N150 and P260 components were analyzed by analysis of variance. P260 amplitudes decreased from 4.40 ± 2.76 &mgr;V (mean ± sd) before treatment to 1.67 ± 1.21 &mgr;V after treatment (P < 0.05), whereas amplitudes of the sham group remained unchanged (2.64 ± 0.94 &mgr;V before versus 2.54 ± 1.54 &mgr;V after treatment). In conclusion, this double-blinded study demonstrated that electric needle acupuncture, as compared with sham treatment, significantly decreased the magnitudes of late SEP amplitudes with electrical noxious stimulation in anesthetized subjects, suggesting a specific analgesic effect of acupuncture.

Dissociation of Pe and ERN/Ne in the conscious recognition of an error.

We evaluated the relationship between conscious awareness and the ERN/Ne and Pe in a digit entering task. On each trial, participants rated the accuracy of their responses on a three-point scale (incorrect, unsure, correct). The ERN/Ne was present on incorrect trials judged as incorrect. The Pe was evident on the same trials but also on correct and incorrect trials judged as unsure. We propose that the ERN/Ne occurs when there is an incorrect execution of a correct motor plan and the representation of the correct response is available for comparison with the actual response. The mismatch information that results from this comparison can be transferred to the Pe process and conscious awareness. However, the Pe process and conscious awareness do not only depend on this transfer of information from the ERN/Ne process. The Pe also occurs when there is uncertainty about the correctness of the motor plan, whether or not the plan is, in fact, correct.

Brain activation upon selective stimulation of cutaneous C- and Aδ-fibers

Thermal and nociceptive cutaneous stimuli activate the brain via two types of nerve fibers, slightly myelinated Adelta-fibers with moderate conduction velocity and unmyelinated C-fibers with slow conduction velocity. Differences in central processing upon selective stimulation of these two fiber types in healthy human subjects still remain poorly understood. By means of event-related functional magnetic resonance imaging the present study investigated brain activation in response to stimulation of Adelta- and C-fibers in healthy subjects. We used the stimulation of tiny skin areas to perform a selective stimulation upon cutaneous C-fibers. Besides similar activation in several brain areas in response to both kinds of stimulation, we observed pronounced brain activation to selective C-fiber stimulation as compared to Adelta-fiber stimulation in the right frontal operculum and anterior insula. Based on a putative function of these structures we suggest that the C-fiber system might be engaged in homeostatic and interoceptive functions in a manner other than the Adelta-fiber system, producing a signal of greater emotional salience.

Drive for thinness and attention toward specific body parts in a nonclinical sample

Objective: To examine the differences between participants scoring high versus low on a drive for thinness construct concerning their visual attention toward specific body parts. We hypothesized that participants scoring high on the drive for thinness subscale would show increased attention to body regions, which are important in the assessment of body weight and thinness like the waist, hips, legs, and arms. Method: We examined eye-gaze behavior of a nonclinical sample of 51 male and female college students with an eye-tracking system as they were looking at pictures of young, attractive males and females. In addition, we used the Eating Disorder Inventory to measure drive for thinness. Results: Participants with increased scores on the drive for thinness subscale looked longer and more often to the waist, hips, legs, and arms as compared with low scorers. In addition, they showed decreased attention toward the head or face. Conclusion: The results indicate that participants scoring high on drive for thinness show an attentional bias toward body regions that are associated with assessing changes in weight. However, they neglected the face, which is the most important source of social and affective information when looking at others. EDI = Eating Disorder Inventory; GLM = general linear model.

An electrophysiological analysis of coaching in Blackjack.

Recent research has demonstrated that a negative deflection in the event-related potential (ERP) that is usually elicited by errors, negative performance feedback, and monetary losses, and which has been associated with response monitoring and reinforcement learning, is also present when we observe others. In the present study we aimed to extend these findings to the domain of coaching behavior. In many contexts of human social life, advice is given by experts to novices, e.g., teachers or parents to scholars or children. However, their advice is sometimes rejected. Here we show that a rejection of ones advice elicits the same negative potential as when one receives negative feedback about ones own behavior.