Biomedical subjects

Tom Beckers

Publications and source records attributed to Tom Beckers.

18 recordsLinked to original sources

PubMed2006

Concomitant deficits in working memory and fear extinction are functionally dissociated from reduced anxiety in metabotropic glutamate receptor 7-deficient mice.

Metabotropic glutamate receptor 7 (mGluR7), a receptor with a distinct brain distribution and a putative role in anxiety, emotional responding, and spatial working memory, could be an interesting therapeutic target for fear and anxiety disorders. mGluR7-deficient (mGluR7-/-) mice showed essentially normal performance in tests for neuromotor and exploratory activity and passive avoidance learning but prominent anxiolytic behavior in two anxiety tests. They showed a delayed learning curve during the acquisition of the hidden-platform water maze, and three interspersed probe trials indicated that mGluR7-/- mice were slower to acquire spatial information. Working memory in the water maze task and the radial arm maze was impaired in mGluR7-/- mice compared with mGluR7+/+. mGluR7-/- mice also displayed a higher resistance to extinction of fear-elicited response suppression in a conditioned emotional response protocol. In a non-fear-based water maze protocol, mGluR7-/- mice displayed similar delayed extinction. These observed behavioral changes are probably not attributable to changes in AMPA or NMDA receptor function because expression levels of AMPA and NMDA receptors were unaltered. Extinction of conditioned fear is an active and context-dependent form of inhibitory learning and an experimental model for therapeutic fear reduction. It appears to depend on glutamatergic and higher-level brain functions similar to those involved in spatial working memory but functionally dissociated from those that mediate constitutional responses in anxiety tests.

Analysis of Variance↗

PubMed2006

Stronger renewal in human fear conditioning when tested with an acquisition retrieval cue than with an extinction retrieval cue.

It was previously demonstrated in our laboratory that conditioned fear in humans can renew after extinction, when this procedure took place in a different context (ABA-renewal [Vansteenwegen et al. (2005). Return of fear in a human differential conditioning paradigm caused by a return to the original acquisition context. Behaviour Research and Therapy, 43(3), 323-336]). Using the same experimental design, we now tested the power of retrieval cues to interact with this contextual renewal phenomenon. Two groups went through acquisition and extinction (in a different context). They were then tested in the original acquisition context and in the presence of a retrieval cue. In the acquisition-cue group, this cue previously featured during the acquisition procedure; in the extinction-cue group, the cue previously featured during the extinction procedure. As expected, renewal of conditioned electro-dermal responding and retrospective expectancy ratings was strongest in the acquisition-cue group. Theoretical and clinical implications of this finding are discussed.

Association Learning↗

PubMed2006

Reasoning rats: forward blocking in Pavlovian animal conditioning is sensitive to constraints of causal inference.

Forward blocking is one of the best-documented phenomena in Pavlovian animal conditioning. According to contemporary associative learning theories, forward blocking arises directly from the hardwired basic learning rules that govern the acquisition or expression of associations. Contrary to this view, here the authors demonstrate that blocking in rats is flexible and sensitive to constraints of causal inference, such as violation of additivity and ceiling considerations. This suggests that complex cognitive processes akin to causal inferential reasoning are involved in a well-established Pavlovian animal conditioning phenomenon commonly attributed to the operation of basic associative processes.

Animals↗

PubMed2005

Neurocognitive and psychotiform behavioral alterations and enhanced hippocampal long-term potentiation in transgenic mice displaying neuropathological features of human alpha-mannosidosis.

Mice with alpha-mannosidase gene inactivation provide an experimental model for alpha-mannosidosis, a lysosomal storage disease with severe neuropsychological and psychopathological complications. Neurohistological alterations in these mice were similar to those in patients and included vacuolations and axonal spheroids in the CNS and peripheral nervous system. Vacuolation was most prominent and evenly distributed in neuronal perikarya of the hippocampal CA2 and CA3 regions, whereas CA1 and dentate gyrus were weakly or not affected. Field potential recordings from CA1 region in hippocampal slices showed enhanced theta burst-induced long-term potentiation (LTP) in alpha-mannosidase-deficient mice. Longitudinal assessment in age-matched alpha-mannosidase-deficient and wild-type littermates, using an extended test battery, demonstrated a neurocognitive and psychotiform profile that may relate to the psychopathological alterations in clinical alpha-mannosidosis. Brainstem auditory-evoked potentials and basic neuromotor abilities were not impaired and did not deteriorate with age. Exploratory and conflict tests revealed consistent decreases in exploratory activity and emotional blunting in the knock-out group. alpha-Mannosidosis mice were also impaired in aversively motivated learning and acquisition of signal-shock associations. Acquisition and reversal learning in the water maze task, passive avoidance learning in the step-through procedure, as well as emotional response conditioning in an operant procedure were all impaired. Acquisition or shaping of an appetitive instrumental conditioning task was unchanged. Appetitive odor discrimination learning was only marginally impaired during shaping, whereas both the discrimination and reversal subtasks were normal. We propose that prominent storage and enhanced LTP in hippocampus have contributed to these specific behavioral alterations in alpha-mannosidase-deficient mice.

Animals↗

PubMed2005

Return of fear in a human differential conditioning paradigm caused by a return to the original acquistion context.

In a differential human fear conditioning paradigm evidence for ABA-renewal was obtained manipulating the lighting in the experimental room. During acquisition in either a dark or illuminated room, one neutral slide was sometimes paired with a loud aversive noise whereas another slide was not. Subsequently, extinction took place in the opposite lighting context. When afterwards the participants were tested again in the original acquisition context, measurements revealed a recovery of the conditioned electrodermal response and an increase in the retrospective verbal US-expectancy ratings. No response recovery was obtained in an AAA-group that received acquisition, extinction and test trials in one and the same context. Several theoretical explanations for this type of return of fear as well as implications for clinical practice are discussed.

Conditioning, Classical↗

PubMed2005

Blocking is sensitive to causal structure in 4-year-old and 8-year-old children.

In a contingency learning task, 4-year-old and 8-year-old children had to predict the outcome displayed on the back of a card on the basis of cues presented on the front. The task was embedded in either a causal or a merely predictive scenario. Within this task, either a forward blocking or a backward blocking procedure was implemented. Blocking occurred in the causal but not in the predictive scenario. Moreover, blocking was affected by the scenario to the same extent in both age groups. The pattern of results was similar for forward and backward blocking. These results suggest that even young children are sensitive to the causal structure of a contingency learning task and that the occurrence of blocking in such a task defies an explanation in terms of associative learning theory.

Child↗

PubMed2005

Outcome additivity and outcome maximality influence cue competition in human causal learning.

Recent research suggests that outcome additivity pretraining modulates blocking in human causal learning. However, the existing evidence confounds outcome additivity and outcome maximality. Here the authors present evidence for the influence of presenting information about outcome maximality (Experiment 1) and outcome additivity (Experiment 2) on subsequent forward blocking. The results of Experiment 3 confirm that, with outcome maximality controlled, outcome additivity affects backward blocking but not release from overshadowing. Finally, the results of Experiment 4 demonstrate that information about outcome additivity has a similar effect on forward blocking if presented after the blocking training instead of before. The results are compatible with the idea that blocking results from inferential processes at the time of testing and not from a failure to acquire associative strength during training.

Adolescent↗

PubMed2005

Further evidence for the role of inferential reasoning in forward blocking.

Previous studies on human causal learning (De Houwer & Beckers, 2003; De Houwer, Beckers, & Glautier, 2002) showed that secondary task difficulty (performing an easy vs. a difficult secondary task during the main causal learning task) and ceiling information (outcome occurs with a maximal vs. submaximal intensity) had an influence on forward blocking (i.e., lower causal ratings for cue T when AT+ trials are preceded by A+ trials than when no A+ trials are presented). We extended these studies by also examining self-reports of participants about the reasons behind their causal ratings. Blocking was found only for participants who reported an appropriate blocking inference. Furthermore, secondary task difficulty and ceiling information influenced the number of participants who reported an appropriate blocking inference. These findings point to a major impact of inferential reasoning in human causal learning.

Humans↗

PubMed2005

Further evidence for the role of mode-independent short-term associations in spatial Simon effects.

We examined the conditions under which short-term associations between stimuli and responses can produce spatial Simon effects. On location-relevant trials, participants gave neutral responses (i.e., they uttered the nonsense syllable "bee" or "boo") on the basis of whether the presented word had the meaning of "left" or "right." On location-irrelevant trials, they gave the same responses on the basis of the color of left and right squares. Performance on the location-irrelevant trials was affected by the match between the irrelevant location information and the location to which the correct response was assigned on the location-relevant trials. Experiment 1 showed that this extrinsic Simon effect was found only when the words on the location-relevant trials came from two different languages. In Experiment 2, we found an extrinsic Simon effect even when participants only received instructions about how to respond on location-relevant trials but no such trials were actually presented. Our findings suggest that task demands determine whether short-term associations are mode specific or mode independent and confirm that such associations can be set up as the result of instructions only.

Association↗

PubMed2005

Contrasting predictive and causal values of predictors and of causes.

Three experiments examined human processing of stimuli as predictors and causes. In Experiments 1A and 1B, two serial events that both preceded a third were assessed as predictors and as causes of the third event. Instructions successfully provided scenarios in which one of the serial (target) stimuli was viewed as a strong predictor but as a weak cause of the third event. In Experiment 2, participants' preexperimental knowledge was drawn upon in such a way that two simultaneous antecedent events were processed as predictors or causes, which strongly influenced the occurrence of overshadowing between the antecedent events. Although a tendency toward overshadowing was found between predictors, reliable overshadowing was observed only between causes, and then only when the test question was causal. Together with other evidence in the human learning literature, the present results suggest that predictive and causal learning obey similar laws, but there is a greater susceptibility to cue competition in causal than predictive attribution.

Adult↗

PubMed2005

Evidence for the role of higher order reasoning processes in cue competition and other learning phenomena.

When people judge the contingency between atarget cue and an outcome, they also take into account the contingency between the outcome and other cues with which the target cue co-occurred. Several authors have argued that such cue competition effects are due to higher order reasoning processes. We review the evidence that supports this hypothesis and discuss whether higher order reasoning might also play a role in other learning phenomena.

Association Learning↗

PubMed2003

Secondary task difficulty modulates forward blocking in human contingency learning.

The influence of a secondary task on forward blocking of human contingency ratings was examined. A smaller blocking effect was found when participants performed a highly demanding secondary task than when they performed a less demanding secondary task. The modulatory effect of secondary task difficulty was significant only when the secondary task was administered during both the learning and the test phase of the contingency judgement task. The results suggest that forward blocking in human contingency learning cannot be fully accounted for by associative processes. Instead, forward blocking seems to depend at least partially on deliberate deductive reasoning processes.

Cognition↗

PubMed2002

Automatic integration of non-perceptual action effect features: the case of the associative affective Simon effect.

In the first phase of Experiment 1, participants were instructed to move a response key up or down in response to a go signal. One of both responses was consistently followed by an aversive stimulus, whereas the other response was never followed by the aversive stimulus. In a subsequent test phase, the same responses had to be emitted according to the grammatical category (noun or adjective) of positive and negative target words. Results showed that the level of affective correspondence between the task-irrelevant positive or negative connotation of the target and the motivational significance of the effect of the correct response influenced performance. The results of Experiment 2 replicated those of Experiment 1, using alternating target-response assignment. These findings point to the integration of affective action effect feature codes in the cognitive representation of actions.

Association Learning↗

PubMed2002

Second-order backward blocking and unovershadowing in human causal learning.

De Houwer and Beckers (in press, Experiment 1) recently demonstrated that ratings about the relation between a target cue T2 and an outcome are higher when training involves CT1+ and T1T2+ followed by C+ trials than when training involves CT1+ and T1T2+ followed by C- trials. We replicated this study but now explicitly asked participants to rate the causal status of the cues both before and after the C+ or C- trials. Results showed that causal ratings for T2 were significantly higher after C+ trials than before C+ trials and that T2 received significantly lower ratings after C- trials than before C- trials. The results thus provide the first evidence for higher-order unovershadowing and higher-order backward blocking. In addition, the ratings for T1 revealed that first-order backward blocking (i.e., decrease in ratings for T1 as the result of C+ trials) was stronger than first-order unovershadowing (i.e., increase in ratings for T1 as the result of C- trials).

Adult↗

PubMed2002

Outcome and cue properties modulate blocking.

Participants saw a series of situations in which a cue (a light appearing at a certain position) could be followed by an outcome (a drawing of a tank that exploded) and were afterwards asked to rate the likelihood of the outcome in the presence of the cue. In Experiments 1 and 2, the compound cues AT and KL were always followed by the outcome (AT+, KL+). During an elemental phase that either preceded or followed the compound phase, Cue A was also paired with the outcome (A+). Cue T elicited a lower rating than Cues K and L when cues were described as being weapons but not when the cues were said to be indicators. The magnitude of this blocking effect was also influenced by whether the outcome occurred to a maximal or submaximal extent. Experiment 3 replicated the effect of cue instructions on blocking (A+, AT+) but showed that cue instructions had no impact on reduced overshadowing (B-, BT+). The results shed new light on previous findings and support probabilistic contrast models of human contingency judgements.

Cues↗

PubMed2002

Higher-order retrospective revaluation in human causal learning.

Previous studies demonstrated that participants will retrospectively adjust their ratings about the relation between a target cue and an outcome on the basis of information about the causal status of a competing cue that was previously paired with the target cue. We demonstrate that such retrospective revaluation effects occur not only for target cues with which the competing cue was associated directly, but also for target cues that were associated indirectly with the competing cue. These second-order and third-order retrospective revaluation effects are compatible with certain implementations of the probabilistic contrast model and with a modified, extended comparator model, but cannot be explained on the basis of a revised Rescorla-Wagner model or a revised SOP model.

Adult↗

PubMed2002

A review of recent developments in research and theories on human contingency learning.

Over the past 20 years, human contingency learning has resurfaced as an important topic within experimental psychology. This renewed interest was sparked mainly by the proposal that associative models of Pavlovian conditioning might also apply to human contingency learning--a proposal that has led to many new empirical findings and theoretical developments. We provide a brief review of these recent developments and try to point to issues that need to be addressed in future research.

Association Learning↗

PubMedDate not supplied

Extinction and renewal of Pavlovian modulation in human sequential Feature Positive discrimination learning.

Using a conditioned suppression task, we investigated extinction and renewal of Pavlovian modulation in human sequential Feature Positive (FP) discrimination learning. In Experiment 1, in context a participants were first trained on two FP discriminations, X-->A+/A- and Y-->B+/B-. Extinction treatment was administered in the acquisition context a (aaa group) or in a new context b (aba group), and comprised X-->A- extinction and Y- control trials. Discriminative X-->A/A responding was lost in both groups when tested in the extinction context, but partially recovered in the aba and not in the aaa group when tested in the acquisition context, suggesting extinction and renewal of extinguished modulation. The same was observed for the Y-->B/B control pair, however, questioning whether the loss of discriminative X-->A/A responding represented genuine extinction of modulation. In Experiment 2, including only aba groups, participants were trained in context a on two FP discriminations, X-->A+/A- and Y-->B+/B-, after which the group "Extinction" was exposed to X-->A- extinction trials in context b, whereas the group "Control" was exposed to X- control trials; concurrently, both groups received further Y-->B+/B- training. In the group Control, differential Y-->B/B and X-->A/A responding were acquired and maintained throughout the experiment. In the group Extinction, while Y-->B/B responding was also maintained throughout, differential X-->A/A responding disappeared because of X-->A- extinction treatment when tested in the extinction context b, but partially reappeared when tested in the acquisition context a. This evidences aba-renewal of extinguished modulation.

Adolescent↗