Hemispheric asymmetry and human associative learning: interactions with attention.

Electrophysiological CNS-processes related to associative learning in humans

OBJECTIVES: Multiple chemical sensitivity is a poorly understood syndrome in which various symptoms are triggered by chemically unrelated, but often odorous substances, at doses below those known to be harmful....

Biased Intensity Judgements of Visceral Sensations After Learning to Fear Visceral Stimuli: A Drift Diffusion Approach.

Endogenous pain modulation has been studied with the conditioned pain modulation (CPM) paradigm with large differences in the magnitude of the CPM effect. We hypothesized that differences in CPM effects might be associated with differences in blood pressure responses to the conditioning stimulus when comparing the CPM effects using two different conditioning stimuli. A single-blind repeated-measures design with block-randomization was applied on 25 healthy male subjects. The test stimulus (TS; tonic heat pain for 120 s) was first presented alone, thereafter in parallel with a conditioning stimulus (CS). Conditioning stimuli were either a cold pressor test (CPT) or equally painful ischaemic muscle pain (ISC), both lasting 120 s. Finger blood pressure and heart rate were recorded continuously. Data were analysed in a linear mixed model framework with CS type (CPT or ISC) and conditioning (TS or TS + CS) as independent factors. An inhibitory CPM effect was found for both types of conditioning (p < 0.001). The CPM effect was larger during CPT conditioning compared with ISC conditioning (p = 0.001). No association with the concomitant cardiovascular response (blood pressure and heart rate) was found (p > 0.34). Cold pressor pain CS induces larger CPM effects than ischaemic pain CS. The larger CPM effect is, however, not associated with a larger blood pressure response. Other factors related to the CS should be investigated to understand why different CS modalities give different CPM effects.

Cerebral Dominance in Musicians and Nonmusicians

Past research has shown that presenting unconditional stimuli (US) during extinction training, either paired with the conditional stimulus (CS) or explicitly unpaired, can reduce spontaneous recovery and slow the re-acquisition of conditional fear. Whether contextual renewal of conditioned fear as indexed by electrodermal responses and self-report measures of anxiety and CS evaluations is also reduced after presentation of paired or unpaired USs during extinction training is currently unclear. Three groups of participants (Paired, Unpaired, Standard Extinction) completed a sequence of habituation, acquisition, extinction, renewal, and re-acquisition phases. During extinction, five CS-US pairings were presented in group Paired, whereas five US were presented alone in group Unpaired. No US were presented during standard extinction. For all groups, extinction was conducted in a context that was different from that of the other phases. Extinction of differential electrodermal responding was evident in groups Unpaired and Standard, but not in group Paired. Contextual renewal and fast re-acquisition, as indexed by differential electrodermal responding, were evident in group Standard, but not in group Unpaired and differential electrodermal responding persisted in group Paired. After extinction, self-reported anxiety was higher in groups Paired and Unpaired, but differential CS evaluations were evident in group Paired only. The current results suggest that presenting additional unpaired USs during extinction training strengthens extinction and protects against the renewal of differential electrodermal responding.

Attentional bias to threat has been almost exclusively examined after participants experienced repeated pairings between a conditioned stimulus (CS) and an aversive unconditioned stimulus (US). This study aimed to determine whether threat-related attentional capture can result from observational learning, when participants acquire knowledge of the aversive qualities of a stimulus without themselves experiencing aversive outcomes. Non-clinical young-adult participants (N = 38) first watched a video of an individual (the demonstrator) performing a Pavlovian conditioning task in which one colour was paired with shock (CS+) and another colour was neutral (CS−). They then carried out visual search for a shape-defined target. Oculomotor measures evidenced an attentional bias toward the CS+ colour, suggesting that threat-related attentional capture can ensue from observational learning. Exploratory analyses also revealed that this effect was positively correlated with empathy for the demonstrator. Our findings extend empirical and theoretical knowledge about threat-driven attention and provide valuable insights to better understand the formation of anxiety disorders.

Conditioning Go/NoGo signals, which determine the triggering stimulus conditional value, were presented to healthy adult subjects (n = 35) in the pause between the target (facial expression) and triggering stimuli. The response of the low-frequency α rhythm to conditioning stimuli was more pronounced in the left hemisphere. The coherence of cortical low-frequency alpha potentials increased 5–7 s after presenting both positive and negative conditioning (Go/NoGo) stimuli (i.e., immediately before the triggering stimulus). These data confirm the assumption that the development of differentiation requires not less functional activity than the development of a positive conditional response. The modulation of cortical activity after presenting Go/NoGo stimuli is mediated primarily by the thalamocortical system of selective attention. The coherence of θ rhythm after the presentation of positive conditioning stimuli was more pronounced in the medial cortical areas, which was apparently determined by the emotional memory function.

Avoidance and alerting behaviors and accompanying physiological responses, including changes in heart rate (HR), are core components of negative emotion. Investigations into the neural mechanisms underlying the regulation and integration of these responses require animal models that simultaneously measure both the physiological and behavioral components of emotion. A primate model is of particular importance in view of the well developed prefrontal cortex of primates, and this region's critical role in emotion regulation and the etiology of affective disorders. Therefore, we have developed a simple aversive conditioning paradigm to assess, simultaneously, cardiovascular and behavioral responses in the marmoset (Callithrix jacchus). Validation of the paradigm was achieved by (1) comparing conditioned responses to a predictive cue with pseudoconditioned responses to a nonpredictive cue; (2) assessing the acquisition of conditioning following lesions of the amygdala, a region essential for associative learning in humans and rats; and (3) determining the contributions of the sympathetic and parasympathetic nervous system to the conditioned autonomic responses. Marmosets acquired conditioned HR and behavioral responses in the conditioned, but not the pseudoconditioned or amygdala lesioned groups. Conditioned HR accelerations were reduced by both parasympathetic and sympathetic blockade. Thus, a model of associative learning of mild negative emotion in the marmoset has been validated by psychological, neurological, and pharmacological investigation. Future studies will determine the role of the prefrontal cortex in the regulation of these negative emotional responses, to provide insights into the neuropathology of affective disorders.

Impaired ability to form associations between negative events in gambling and aversive somatic reactions may be a predisposing factor for pathological gambling. The current study investigated whether a group of pathological gamblers and a control group differed in aversive classical conditioning. A differential aversive classical conditioning paradigm, which consisted of three phases. In the habituation phase, one 850-Hz tone stimulus and one 1500-Hz tone stimulus were presented three times each in random order. In the acquisition phase, the two tones were presented 10 times each in random order, and one was always followed by a 100-dB burst of white noise. In the extinction phase the two tones were presented three times each without the white noise. University laboratory testing facilities and out-patient treatment facilities. Twenty pathological gamblers and 20 control participants. Duration of seven cardiac interbeat-intervals (IBIs) following tone offset, gambling severity, tobacco and alcohol use, anxiety and depression. No group differences were found in the habituation and acquisition phases. However, a significant group × stimuli × trials × IBIs interaction effect was found in the extinction phase (P < 0.049). Follow-up analysis indicated that the pathological gamblers did not show aversive classical conditioning, but that the control group did. Pathological gamblers have a diminished capacity to form associations between aversive events and stimuli that predict aversive events. Aversion learning is likely to be an ineffective treatment for pathological gamblers.

Despite extensive research on conditioned pain modulation (CPM), uncertainties remain regarding the role of cognitive mechanisms, such as attentional focus, distraction, and intrinsic a priori expectations, and the most optimal CPM protocol design (parallel vs. sequential). This study examined whether these cognitive factors influence CPM efficacy, and whether CPM magnitude differs between a parallel and sequential protocol. Seventy-two healthy adults participated in this randomised cross-over study undergoing CPM evaluation, that is, pain pressure threshold assessment (=test stimulus) in response to hot water immersion (=conditioning stimulus (CS)) during four experimental protocols, that is, a neutral parallel protocol, a neutral sequential protocol, a sequential protocol with attentional focus on the CS-induced pain intensity, and a sequential protocol with attentional distraction from the CS. Pain expectations were recorded before each protocol. Focusing attention on the CS during CPM assessment resulted in smaller CPM magnitudes compared to no attentional manipulation or distracting from the CS. Distracting from the CS did not affect CPM magnitude compared to no attentional manipulation, nor did a priori expectations. Although CPM magnitudes were not statistically different between the parallel and sequential CPM protocol, a sequential protocol provides higher mean magnitudes and responder rates. Since attentional focus on the CS reduces CPM efficacy, it is recommended to not rate the CS pain intensity during CS application to prevent a reduction of the inhibitory effect. Furthermore, a sequential protocol is recommended over a parallel protocol as a 'cleaner' representation of pain modulation free of attentional sources of biases. Conditioned pain modulation (CPM) is an important biomarker reflecting pain processing, however, there is a high variability in CPM response, making it important to gain insight into the influencing factors and mechanisms of CPM. The results of this study suggest that attentional focus on the conditioning stimulus influences CPM magnitude, whereas a distraction task and intrinsic a priori expectations do not. In both therapeutic and preventive approaches, it is of great interest for clinicians to positively address factors influencing CPM. ClinicalTrials.gov identifier: NCT05161286.

Hemispheric asymmetries were investigated with various auditory techniques in several groups of subjects. The first study was a dichotic listening experiment in which two separate musical chords were presented simultaneously one to each ear of right-handed males. The subjects were required to listen to the chord stimuli and then recognize them from a multiple choice of four chords heard immediately following the dichotic presentation. More chords were recognized from the left ear than from the right implying right cerebral dominance for this task. In a similar test, dichotic presentation of melodies showed no difference between the ears. It was hypothesized that the subjects in this case were identifying the tune segments on the basis of rhythmic rather than pitch cues. It was suggested that the right hemisphere is superior to the left in processing stimuli that are non-temporal. Musical expression was investigated in patients who had transiently lost the function of one hemisphere following intracarotid amytal injection. It was observed that after right hemisphere depression, singing was devoid of pitch at a time when speech was only minimally disturbed. Conversely, singing was much less affected than speech after left hemisphere depression. This differential effect of amytal depression is supportive of the idea that the right hemisphere is used for pitch control in singing whereas the left hemisphere is used expressly for speech. Singing was also studied in two young patients with surgical hemispherectomies for non-infantile causes. One patient who had a right hemisphere removal with no evidence of aphasia, sang most songs poorly. He also failed pitch discrimination tests wherein he could not distinguish two tones that were separated by an interval of less than one musical step. Another patient with a left hemispherectomy produced the opposite results. She had great difficulties in expressive speech yet could sing with excellent pitch control and intonation. These cases support the previous conclusion that the right hemisphere is necessary for correct pitch production in singing. Dichotic listening studies on patients with complete surgical division of the corpus callosum indicated that the right hemisphere also had some capacity to understand and manually express verbs and verbal commands. This was evidenced in instances where only the command presented to the left ear was manually performed at a time when another command presented simultaneously to the right ear was the only one that was verbally reported. The indication is that the right hemisphere understood and performed the required action when the left hemisphere was apparently unaware. However, it was also shown that for most dichotic verbal tests the left hemisphere still has dominant control over the right. Dichotic listening studies also indicated that the left hemisphere could separately monitor stimuli in the ipsilateral along with stimuli in the contralateral pathway. This was contradictory to previous conclusions that the contralateral pathway suppresses the ipsilateral in dichotic competition. Response time studies carried out in these callosum-sectioned patients investigated organization of the two cortical systems that separately analyzed stimuli from the two ascending paths. It was found that response times for repeating words to the right ear were faster than for words in the left ear. Control tests showed the cause of this difference was not in delay of transmission in ascending routes, nor in differences of perception in the two systems. It was deduced .that the cause was an asymmetrical process of memory retrieval for translation into motor impulses to the speech apparatus.

The C50m response: Conditioned magnetocerebral activity recorded from the human brain

Do Word-Processing Problems Cause Social Anxiety?

We aimed to examine mechanistically the observed foraging differences across two honey bee, Apis mellifera, subspecies using the Proboscis Extension Response (PER) assay. Specifically, we compared differences in appetitive reversal learning ability between honey bee subspecies:Apis mellifera caucasica(Pollman), andApis mellifera syriaca(Skorikov) in a “common garden” apiary. It was hypothesized that specific learning differences could explain previously observed foraging behavior differences of these subspecies: A.m. caucasica switches between different flower color morphs in response to reward variability, and A.m. syriaca does not switch. We suggest that flower constancy allows reduced exposure by minimizing search and handling time, whereas plasticity is important when maximizing harvest in preparation for long winter is at a premium. In the initial or Acquisition phase of the test we examined specifically discrimination learning, where bees were trained to respond to a paired conditioned stimulus with an unconditioned stimulus and not to respond to a second conditioned stimulus that is not followed by an unconditioned stimulus. We found no significant differences among the subspecies in the Acquisition phase in appetitive learning. During the second, Reversal phase of the experiment, where flexibility in association was tested, the paired and unpaired conditioned stimuli were reversed. During the Reversal phaseA. mellifera syriacashowed a reduced ability to learn the reverse association in the appetitive learning task. This observation is consistent with the hypothesis that A.m. syriaca foragers cannot change the foraging choice because of lack of flexibility in appetitive associations under changing contingencies. Interestingly, both subspecies continued responding to the previously rewarded conditioned stimulus in the reversal phase. We discuss potential ecological correlates and molecular underpinnings of these differences in learning across the two subspecies. In addition, in a supplemental experiment we demonstrated that these differences in appetitive reversal learning do not occur in other learning contexts.