Kamin Blocking Effect Research Articles

Strawman argument characterises critique of Kamin blocking effect.

This commentary focuses on the robustness of the Kamin blocking effect (KBE) that Maes et al., based upon 15 failures to replicate, have questioned. This challenge to KBE robustness has not gone unaddressed. Soto outlined conceptual as well as methodological issues that cast doubt on the validity of the Maes et al. critique. Despite recognition of certain interpretive issues, Maes et al. have reaffirmed that their failures to replicate are meaningful and call out for further parametric scrutiny of KBE. Faced with such marked differences of opinion with regard to KBE robustness, the present commentary highlights certain methodological features that may have contributed to the Maes et al. failures to replicate: (a) Roles of stimulus salience and independence, (b) Multiple test trials, and (c) Reliance on a single control procedure. It is suggested that the existence of such methodological issues renders it fallacious to argue that the Maes et al. findings represent a true failure to replicate KBE. Instead, the present formulation contends that Maes et al. engaged in a strawman argument in which they have found fault with a distorted version of KBE rather than KBE itself. Although employing variations of paradigms that had earlier been seen to generate KBE, the presence of multiple methodological shortcomings was such as to effectively mask observance of KBE. In affirmation of the Soto's critique, the replication failure reported by Maes et al. is thus seen as unsurprising. Accordingly, the Maes et al. proposal to remove KBE as a "touchstone for our theories of elementary learning" is argued to be unwarranted. In the face of this protracted dispute, the positing of a strawman argument serves to further cast doubt upon the import of the Maes et al. replication failure, and consequently, to reaffirm KBE as a core phenomenon in the learning domain.

The nucleus accumbens and inhibition in the ventral tegmental area play a causal role in the Kamin blocking effect.

The discovery of Kamin blocking led to the idea that associative learning occurs only when there is a mismatch between actual and predicted outcomes, or prediction error. The neural substrates involved in regulating this prediction error during behavioral learning are still not fully elucidated. We investigated in rats the role of the ventral tegmental area and the nucleus accumbens in Kamin blocking. Our blocking paradigm involved three phases: appetitive classical conditioning of a lever cue, conditioning of a compound of the lever cue plus an auditory cue, and testing response to the auditory cue in extinction. We found that disruption of inhibition in the ventral tegmental area by bicuculline, or designer receptor mediated inactivation of the nucleus accumbens, during compound cue conditioning, attenuated Kamin blocking. These results suggest that inhibition in the ventral tegmental area and inhibitory output from the nucleus accumbens are necessary for blocking and make behaviorally significant contributions to the computation of reward prediction error. In addition, we found that inactivating the neurons in the nucleus accumbens during classical conditioning of the lever cue also attenuated blocking, without affecting classical conditioning of the lever. This indicates that learning in the nucleus accumbens is necessary for blocking and reward estimation. Our results reveal a causal role for nucleus accumbens modulated inhibitory inputs to the ventral tegmental area in the blocking effect and suggest that they contribute to computation of reward prediction error during associative learning.

Application of a Prediction Error Theory to Pavlovian Conditioning in an Insect.

Elucidation of the conditions in which associative learning occurs is a critical issue in neuroscience and comparative psychology. In Pavlovian conditioning in mammals, it is thought that the discrepancy, or error, between the actual reward and the predicted reward determines whether learning occurs. This theory stems from the finding of Kamin’s blocking effect, in which after pairing of a stimulus with an unconditioned stimulus (US), conditioning of a second stimulus is blocked when the two stimuli are presented in compound and paired with the same US. Whether this theory is applicable to any species of invertebrates, however, has remained unknown. We first showed blocking and one-trial blocking of Pavlovian conditioning in the cricket Gryllus bimaculatus, which supported the Rescorla–Wagner model but not attentional theories, the major competitive error-correction learning theories to account for blocking. To match the prediction error theory, a neural circuit model was proposed, and prediction from the model was tested: the results were consistent with the Rescorla–Wagner model but not with the retrieval theory, another competitive theory to account for blocking. The findings suggest that the Rescorla–Wagner model best accounts for Pavlovian conditioning in crickets and that the basic computation rule underlying Pavlovian conditioning in crickets is the same to those suggested in mammals. Moreover, results of pharmacological studies in crickets suggested that octopamine and dopamine mediate prediction error signals in appetitive and aversive conditioning, respectively. This was in contrast to the notion that dopamine mediates appetitive prediction error signals in mammals. The functional significance and evolutionary implications of these findings are discussed.

Unified principle of reinforcement in a neural-network model: Reply to N. T. Calvin and J. J. McDowell

An article published in Behavioural Processes (Calvin and McDowell, 2015) contemplated that the approach to neural networks developed by the present authors cannot simulate certain behavioral findings, notably the Kamin blocking effect and successive conditioning. Here we demonstrate that these concerns are unwarranted as an overall characterization of the approach. In addition, several other more general issues identified in the target article are addressed as well. These include the determination of network architectures, the assignment-of-credit problem, the potential for catastrophic interference, and the falsifiability of the model.

Abnormal prediction error is associated with negative and depressive symptoms in schizophrenia

Prediction error in learning is where learning occurs to the degree to which an outcome consequent to a stimulus is surprising. It has been suggested that abnormal use of prediction error in schizophrenia may underlie the formation of inappropriate associations giving rise to psychotic symptoms. Kamin blocking is a phenomenon that demonstrates prediction error. Kamin blocking is shown where prior learning about a stimulus A paired with an outcome retards learning about a stimulus B when presented subsequently as part of a stimulus compound AB paired with the same outcome. Prior studies have indicated reduced Kamin blocking in schizophrenia specifically in non-paranoid patients. It is however unclear how reduced Kamin blocking is associated with specific symptoms in schizophrenia. The present study examined Kamin blocking performance in a high functioning community-based sample of 34 people with schizophrenia and 48 controls closely matched for pre-morbid IQ. In these patients we measured Kamin blocking and symptoms using positive and negative symptom scales (PANSS) and Scale for the Assessment of Negative Symptoms (SANS) and Scale for the Assessment of Positive Symptoms (SAPS). Results confirmed that people with schizophrenia had significantly reduced Kamin blocking. Kamin blocking performance was associated with negative and depressive symptoms. These associations with symptoms were crucially not found with baseline associative learning or unblocking measures, confirming specificity to the Kamin blocking effect. These data demonstrate first that abnormal prediction error as assessed in the Kamin blocking task is associated with negative and depressive symptoms rather than positive symptoms in high functioning schizophrenia patients. Second this strongly suggests that reduced Kamin blocking may be useful as an animal model of specific relevance to negative and depressive symptoms in schizophrenia.

Mapping Pavlovian conditioning effects on the brain: blocking, contiguity, and excitatory effects.

Pavlovian conditioning effects on the brain were investigated by mapping rat brain activity with fluorodeoxyglucose (FDG) autoradiography. The goal was to map the effects of the same tone after blocking or eliciting a conditioned emotional response (CER). In the tone-blocked group, previous learning about a light blocked a CER to the tone. In the tone-excitor group, the same pairings of tone with shock US resulted in a CER to the tone in the absence of previous learning about the light. A third group showed no CER after pseudorandom presentations of these stimuli. Brain systems involved in the various associative effects of Pavlovian conditioning were identified, and their functional significance was interpreted in light of previous FDG studies. Three conditioning effects were mapped: 1) blocking effects: FDG uptake was lower in medial prefrontal cortex and higher in spinal trigeminal and cuneate nuclei in the tone-blocked group relative to the tone-excitor group. 2) Contiguity effects: relative to pseudorandom controls, similar FDG uptake increases in the tone-blocked and -excitor groups were found in auditory regions (inferior colliculus and cortex), hippocampus (CA1), cerebellum, caudate putamen, and solitary nucleus. Contiguity effects may be due to tone-shock pairings common to the tone-blocked and -excitor groups rather than their different CER. And 3) excitatory effects: FDG uptake increases limited to the tone-excitor group occurred in a circuit linked to the CER, including insular and anterior cingulate cortex, vertical diagonal band nucleus, anterior hypothalamus, and caudoventral caudate putamen. This study provided the first large-scale map of brain regions underlying the Kamin blocking effect on conditioning. In particular, the results suggest that suppression of prefrontal activity and activation of unconditioned stimulus pathways are important neural substrates of the Kamin blocking effect.

Impaired associative learning in chronic schizophrenics and their first-degree relatives: A study of latent inhibition and the Kamin blocking effect

The performance of chronic schizophrenic probands ( n=21), their first-degree schizotypal (22) and non-schizotypal (19) relatives, and normal controls (24), was measured in two associative learning paradigms, latent inhibition and the Kamin blocking effect. These paradigms assess the effects on learning of initial exposure to other learning contingencies. The normal subjects showed latent inhibition (retarded learning of an association between a burst of white noise and a visually displayed counter increment, if the subject had first been pre-exposed to the white noise without any other consequence) and Kamin blocking (retarded learning of an association between two visual stimuli, if the conditioned stimulus was presented simultaneously with a second, already conditioned stimulus). The schizophrenic probands and both the schizotypal and non-schizotypal relatives were severely impaired in basic associative learning, performing much worse than the normal subjects in the control conditions (i.e. those lacking stimulus pre-exposure of any kind) of both the latent inhibition and the Kamin paradigms and also showed a loss of the normal latent inhibition and Kamin blocking effects. The performance of the three clinically defined groups was statisitically indistinguishable. These findings contrast with previous reports of the performance of normal subjects classified as schizotypal by questionnaire, who are not impaired in basic associative learning, and are particularly fast to learn after stimulus pre-exposure. The results question the assumption that high schizotypy, as assessed by questionnaire, is like schizotypy in schizophrenic kin. The severe impairment in basic associative learning in schizophrenic patients and their kin warrants further investigation.

Disruption of the Kamin blocking effect in schizophrenia and in normal subjects following amphetamine

The Kamin blocking effect (KBE) is an established animal learning paradigm measuring selective processing, in which reduced blocking reflects allocation of greater processing resources to non-relevant information. Two KBE tasks are described below. Results from studies using the first (between-subjects) task indicate that KBE is abolished in acute schizophrenics with positive psychotic symptoms. It is also abolished in the relatives of schizophrenic subjects, although interpretation of this finding is hampered by poor performance of subjects in the control condition. The second (within-subjects) task indicated abolition of KBE in schizophrenic patients with positive psychotic symptoms. Administration of acute amphetamine to normal human subjects did not significantly disrupt performance on the first task. Whilst for the second task, although blocking was limited to placebo subjects, overall pre-exposure effects are not sufficiently strong to indicate specific drug effects.

An investigation into selective learning abilities in normal and attentionally disordered children using the Kamin blocking paradigm

Previous research is unclear about the ability of hyperactive subjects to engage in selective processing, although a failure in this system is a feature of the diagnosis of attention deficit hyperactivity disorder (ADHD; American Psychiatric Association, 1987). In the present study selective processing is tested, by means of a Kamin blocking task, in 60 normal and 20 ADHD children. The Kamin blocking effect was observed in both normal and ADHD male children. Female subjects (all of whom were normal children) failed to exhibit the Kamin blocking effect. Reports of incidental learning studies have indicated that hyperactive children process information in a more diffuse manner than controls. The present results indicate normal selective processing in hyperactive children. It is suggested that abnormalities in recall strategies, rather than information processing, may therefore explain incidental learning findings. The lack of blocking in female subjects was not expected, a possible reason for this is discussed, which can be tested by simple alterations to the current blocking task.

A simple (or simplistic?) cognitive model for schizophrenia

An approach which views schizophrenia as a disturbance of information processing appears promising as a way of linking biological and clininal aspects of the disorder. A review of research in this area led to the suggestion that the basic disturbance in schizophrenia is “a weakening of the influences of stored memories of regularities of previous input on current perception”. This formulation leads to the prediction that in certain circumstances, schizophrenics may perform better than normal subjects. Recent studies employing tasks derived from human experimental psychology provide evidence in support of the model. It is argued that the link between information processing disturbances and biological abnormalities may be facilitated by the use of paradigms derived from animal learning theory (latent inhibition and Kamin's blocking effect). On both tasks the pattern of performance of acute schizophrenics is consistent with the cognitive model. The ways in which such an information processing disturbance may lead to schizophrenic symptomatology are outlined, with particular reference to the formation and maintenance of delusional beliefs. The core cognitive abnormality may result from a disturbance in any of the brain structures involved in the prediction of subsequent sensory input. The proposed circuit, which draws heavily on Gray's model, implicates in particular the hippocampus and related areas and is consistent with studies of brain pathology in schizophrenia.

Loss of the Kamin blocking effect in acute but not chronic schizophrenics

Differences between research diagnostic criteria (RDC)-diagnosed acute and chronic schizophrenics and normal controls were studied using a Kamin blocking procedure. Blocking is an established animal learning procedure, thought by some researchers to reflect selective attention; decreased blocking indicates increased processing of irrelevant stimuli. It was predicted that this pattern would be obtained in acute schizophrenics, tested soon after admission, for two reasons: (1) evidence from previous clinical studies indicates that acute schizophrenics are more aware of nonsalient aspects of their environment than controls; and (2) blocking is disrupted in animals in a hyperdopaminergic state and restored by neuroleptic medication. This was the case: acute, but not chronic, schizophrenics showed disrupted blocking. This disruption was especially clear in those acute schizophrenics tested within 2 weeks of hospital admission. By the second test session (in a cross-over design), there was some evidence of normalization in performance in the acute schizophrenics. These findings are considered with regard to the dopamine hypothesis of schizophrenia.

The Kamin blocking effect, incidental learning and schizotypy (a reanalysis)

Performance of Kamin blocking and incidental learning tasks has been found to be significantly affected in acute, positively symptomatic, subjects. However, a previous study of normal subjects failed to show any relationship with schizotypy. The present study reanalyses these data in the light of Hewitt and Claridge's three-factor solution to Claridge's schizotypy scale. The ‘unusual perceptual experiences’ factor is found to be related to performance of both incidental learning tasks and there is a trend towards it being related to the second of two Kamin blocking tasks. Results suggest that this more sophisticated approach to schizotypy may enhance correspondence between findings in schizophrenic and ‘psychosis-prone’ normal subjects.

Latent inhibition and blocking

Conventional animal models of schizophrenia do not pretend to account for the symptoms of schizophrenia; i.e. they lack construct validity. Ellenbroek and Cools (1990) have reviewed a number of other models with construct validity for fundamental psychological processes, which are hypothesised to be deficient in schizophrenia. Two of these, Latent Inhibition (LI) and the Kamin Blocking effect (KB), essentially demonstrate the effects of prior learning on the formation of current associations. Animal studies have now shown that LI and KB are disrupted by increased dopaminergic activity, and restored by dopaminergic blockade. The present paper adds to the database described by Ellenbroek and Cools and discusses some further theoretical and practical issues. Specifically: (a) Kamin's blocking is disrupted in acute, but not in chronic schizophrenic subjects; (b) LI and KB are not simply examples of associative interference; (c) The masking task used in adult human studies of LI does not introduce an element of blocking as defined by Kamin's paradigm; (d) A direct study of "selective attention" in acute schizophrenia suggests that the impairment in LI and KB relates to the utilisation of experience about past regularities, rather than a generalised attentional deficit; (e) Recent studies, especially with nicotine, indicate that LI can be disrupted by drug administration during acquisition only; (f) It is now possible to study the release of dopamine, and of other transmitters in the nucleus accumbens and in other brain areas, during the behavioural paradigm of LI in rats. In this way it should be possible to determine directly the neuronal circuitry involved in LI (and KB): this approach could explain the link between the neuropathology and neuropharmacology of schizophrenia and its symptoms, besides providing more valid test procedures for evaluating potential neuroleptic drugs.

The neuropsychology of schizophrenia

AbstractA model is proposed for integrating the neural and cognitive aspects of the positive symptoms of acute schizophrenia, using evidence from postmortem neuropathology and neurochemistry, clinical and preclinical studies of dopaminergic neurotransmission, anatomical connections between the limbic system and basal ganglia, attentional and other cognitive abnormalities underlying the positive symptoms of schizophrenia, specific animal models of some of these abnormalities, and previous attempts to model the cognitive functions of the septohippocampal system and the motor functions of the basal ganglia. Anatomically, the model emphasises the projections from the septohippocampal system, via the subiculum, and the amygdala to nucleus accumbens, and their interaction with the ascending dopaminergic projection to the accumbens. Psychologically, the model emphasises a failure in acute schizophrenia to integrate stored memories of past regularities of perceptual input with ongoing motor programs in the control of current perception. A number of recent experiments that offer support for the model are briefly described, including anatomical studies of limbic-striatal connections, studies in the rat of the effects of damage to these connections, and of the effects of amphetamine and neuroleptics, on the partial reinforcement extinction effect, latent inhibition and the Kamin blocking effect; and studies of the latter two phenomena in acute and chronic schizophrenics.

The Kamin blocking effect, incidental learning and psychoticism

The Kamin blocking effect consists in impaired learning of an association between a conditioned stimulus (CS2) and an unconditioned stimulus (UCS) if CS2 is presented simultaneously with a different CS (CS1) already associated with the UCS. It is well established with animal but not human subjects. In the two experiments presented here, the effect was clearly demonstrated with UCS = a computer-presented yellow square, CS1 = a blue square and CS2 = a noise (Expt 1) or two smaller white squares (Expt 2). The Kamin effect has, by some theorists, been attributed to switching of attention away from CS2, which conveys only redundant information. If so, the size of the effect should co-vary with indices of selective attention commonly used with human subjects. As predicted, the blocking effect was found to be smaller in subjects who displayed a high degree of incidental learning in either of two tasks in which intentional vs. incidental learning corresponded to (1) words vs. word position, or (2) a target initial word letter vs. non-target initial letters. We report elsewhere that the blocking effect is absent in acute schizophrenics. In the present experiments, however, there was no systematic relation between any of four measures of psychoticism, or intelligence, and either the blocking effect or incidental learning.

Blocking of conditioned suppression with 1 or 10 compound trials

It is generally agreed that the Kamin blocking effect provides a differential test of the model of classical conditioning proposed by Rescorla and Wagner (1972), on the one hand, and the models proposed by Mackintosh (1975) and Pearce and Hall (1980), on the other. Specifically, if the blocking effect occurs with 1 compound trial, Rescorla and Wagner are supported. Experiment 1 showed that prior training with one element of a simultaneous compound stimulus prevented the added element from becoming conditioned with 10 compound trials when compared with a nonpretrained (Kamin) control. A pseudoconditioning control, which received no compound training, showed substantial suppression only on the first trial. A contextual conditioning control, which received unsignaled shock prior to compound training, was suppressed, suggesting a failure of conditioning to contextual cues. Experiment 2 demonstrated 1-compound-trial blocking using a simultaneous presentation of the compound elements. The importance of this support for the Rescorla-Wagner model is discussed in the light of other supportive studies and those which support alternative models of classical conditioning.

Blocking as a Retrieval Failure: Reactivation of Associations to a Blocked Stimulus

Conditioned lick suppression in rats was used to examine the effectiveness of three different “reminder” treatments in reactivating associations to a blocked stimulus in a Kamin blocking paradigm. Experiment I indicated that with our parameters prior tone-footshock pairings could block manifestation of a light-footshock association that would otherwise be evident following pairings of a light-tone compound stimulus with footshock. In Experiment II, exposure to either the US, the blocked stimulus (light), or the apparatus cues between the compound conditioning trials and testing decreased blocking. Experiments III(a) and III(b) replicated the unblocking effects seen in Experiment II and included control groups that received the identical training and reminder treatments except for the omission of the light from the compound stimulus. These latter animals failed to display behaviour comparable to the blocked and reminded subjects, thereby establishing the associative basis of suppression to the light in the animals reminded following treatment known to produce blocking. Experiment IV also replicated the results of Experiment II and included control groups that received identical light-tone compound trials and reminder treatments without prior conditioning to the tone alone. In these control groups, reminder treatments tended to disrupt rather than increase evidence of conditioning to the light. The results suggest that associations are formed to the added element of a compound despite prior conditioning to the initial element, and that failure on the test trial to retrieve these associations to the blocked CS, rather than a failure to attend to or learn about the added element, is at least in part responsible the Kamin blocking effect.

Pavlovian conditioning and human fear: An expectancy model

Behavior therapists have explained phobias in terms of the contiguity principle of Pavlovian conditoning, which holds that conditioning results from CS-US temporal pairings. This principle provides a problematic account of phobias because CS-US pairings are neither necessary nor sufficient for fear acquisition in humans and because it cannot explain the Kamin blocking effect, conditioned inhibition, cessation conditioning, and overexpectedness in infrahuman conditioning. An expectancy model is proposed as an alternative to the contiguity model. The expectancy model holds that what is learned in Pavlovian conditioning is an expectation regarding the occurrence or nonoccurrence of the US. The mediating expectacy process can become an elicitor of CRs, verbal reports of CS-US relations (awareness), and instrumental behavior. The Wagner-Rescorla formulas for describing the learning of CRs in Pavlovian conditioning are assumed to have important implications for stimulus expectancy learning. A four-process model of phobias is proposed: (1) danger expectancy, (2) anxiety expectancy, (3) negative reinforcement of avoidance, and (4) positive (self-) reinforcement of avoidance. Implications are discussed for CS exposure therapies, placebos, self-efficacy, and aversion-relief therapy.

The Kamin blocking effect with variable-duration CSs

The role of temporal uncertainty surrounding the time of US occurrence in Kamin’s two-stage blocking paradigm was studied. In Stage 1, stimulus A terminated with the onset of a .5-sec, 1-mA shock US; in Stage 2, a compound stimulus, AX, was similarly reinforced. For different groups of eight rats each, the duration of stimulus A and/or AX was either fixed or was varied from trial to trial. When the stimulus duration was fixed, it predicted the exact time of US onset; when it was varied, it did not. We suspected that uncertainty about the moment of US occurrence might enhance US “surprise.” If so, then blocking might be attenuated in the varied CS-duration conditions relative to the standard condition in which both A and AX were fixed. Within the range of temporal uncertainty studied here, however, no significant attenuation of blocking was observed.

Forgetting of a CS attribute in a conditioned suppression paradigm

Although a number of studies have demonstrated nearly complete retention of fear in a conditioned suppression task, they provide little information about the nature of the memory for the CS. The purpose of the present experiment was to investigate the retention of an attribute of a tonal CS that had been paired with shock and was thus capable of eliciting a conditioned emotional response (CER) in rats. The Kamin blocking effect was utilized to detect changes in the memory of CS attributes. Either 1 or 21 days following conditioning to a tone, separate groups of rats received compound conditioning in which either the original or a novel tone was combined with a light. Subsequent measurement of suppression to the added element (light) indicated that only the original CS produced blocking at the short delay, but that both original and novel tones resulted in blocking at the 21-day interval. This increase in the extent of blocking suggests that memory for specific attributes of the CS does diminish as a function of time.