Re-emergence of under-selected stimuli, after the extinction of over-selected stimuli in an automated match to samples procedure

Stimulus over-selectivity occurs when one of potentially many aspects of the environment comes to control behaviour. In two experiments, adults with no developmental disabilities, were trained and tested in an automated match to samples (MTS) paradigm. In Experiment 1, participants completed two conditions, in one of which the over-selected stimulus was established, and then extinguished by pairing the over-selected stimulus with a novel stimulus and reinforcing the novel stimulus. In the control condition no extinction took place. Experiment 2 replicated this experiment using a between subjects design. In both studies, it was found that when the over-selected cue was extinguished, previously under-selected cues re-emerged to control behaviour in a re-test phase. These findings suggest that over-selectivity is not simply due to an attentional deficit, and that the re-emergence of the under-selected stimuli suggests that the previously under-selected stimuli were learnt about. Moreover, the results suggest that extinction of over-selected cues may have potential applied benefit as an intervention.     

Extinction of Over-selected Stimuli Causes Emergence of Under-selected Cues in Higher-functioning Children with Autistic Spectrum Disorders

Two experiments examined whether over-selectivity is the product of a post-acquisition performance deficit, rather than an attention problem. In both experiments, children with Autistic Spectrum Disorder were presented with a trial-and-error discrimination task using two, two-element stimuli and over-selected in both studies. After behavioral control by the previously over-selected stimulus was extinguished, behavioral control by the previously under-selected cue emerged without direct training. However, this effect was only found in higher-functioning children, and not with more severely impaired children. These findings suggest that over-selectivity is not simply due to a failure to attend to all of the stimuli presented. They also suggest that extinction of over-selected stimuli may be a fruitful line of intervention for clinical intervention for some individuals.     

The Effect of Stimulus Salience on Over-selectivity

The influence of stimulus salience on over-selective responding was investigated in the context of a comparator theory of over-selectivity. In Experiments 1 and 2, participants were presented with two cards, each displaying two colors. In comparison to matched control participants, participants with Autistic Spectrum Disorder (ASD) demonstrated more over-selectivity, which increased when the stimuli differed in salience. In Experiment 3, the over-selected color was extinguished, and the previously under-selected color emerged to control behavior. The results suggest that stimuli of different salience may trigger over-selectivity in individuals with ASD, and provide preliminary support that this may be due to the action of an over-sensitive comparator mechanism functioning at the retrieval level of processing.     

The Effect of Concurrent Task Load on Stimulus Over-Selectivity

Stimulus over-selectivity is a phenomenon displayed by individuals with autism, and has been implicated as a basis for many autistic-spectrum symptoms. In four experiments, non-autistic adult participants were required to learn a simple discrimination using picture cards, and then were tested for the emergence of stimulus over-selectivity, both with and without a concurrent task. Greater stimulus over-selectivity was noted when participants completed the concurrent task. The results are discussed in relation to the implications for the development of a model of memory deficits in autism.     

Over-Selectivity is Related to Autism Quotient and Empathizing,But not to Systematizing

The relationships of autism quotient (AQ), systematizing (SQ), and empathizing (EQ), with over-selectivity were explored to assess whether over-selectivity is implicated in complex social skills, which has been assumed, but not experimentally examined. Eighty participants (aged 18–60) were trained on a simultaneous discrimination task (AB+CD?), and tested in extinction on the degree to which they had learned about both elements of the reinforced (AB) compound. Higher AQ and lower EQ scorers demonstrated greater over-selectivity, but there was no relationship between SQ and over-selectivity. These results imply that high AQ scorers perform similarly to individuals with ASD on this cognitive task, and that over-selectivity may be related to some complex social skills, like empathy.     

The effect of observing response procedures on the reduction of over-selectivity in a match to sample task: immediate but not long term benefits

Stimulus over-selectivity occurs when only one of potentially many aspects of the environment comes to control behavior. In three experiments, adult participants with no developmental disabilities were trained and tested in a match to samples (MTS) paradigm. Participants in Experiment 1 were assigned to one of two conditions, which differed on whether an observing response procedure was in place. Findings indicated that an MTS procedure can induce over-selectivity in this population if a time delay is included between sample and comparison. Over-selectivity emerged significantly more in the group who did not use an observing response procedure. In Experiments 2 and 3, participants were exposed to a re-test phase, in which the initial stimuli were presented again, but without the use of an observing response in either group. The observing response procedure only reduced over-selectivity when in place, but performance did not remain high following its withdrawal. This effect was noted regardless of the type of observing response procedure used (pointing versus naming). These findings suggest that an observing response procedure may be effective in reducing over-selectivity, however, these effects do not last post intervention, and that this may limit the clinical usefulness of the technique.     

The P300 wave of the human event-related potential.

The P300 wave is a positive deflection in the human event-related potential. It is most commonly elicited in an "oddball" paradigm when a subject detects an occasional "target" stimulus in a regular train of standard stimuli. The P300 wave only occurs if the subject is actively engaged in the task of detecting the targets. Its amplitude varies with the improbability of the targets. Its latency varies with the difficulty of discriminating the target stimulus from the standard stimuli. A typical peak latency when a young adult subject makes a simple discrimination is 300 ms. In patients with decreased cognitive ability, the P300 is smaller and later than in age-matched normal subjects. The intracerebral origin of the P300 wave is not known and its role in cognition not clearly understood. The P300 may have multiple intracerebral generators, with the hippocampus and various association areas of the neocortex all contributing to the scalp-recorded potential. The P300 wave may represent the transfer of information to consciousness, a process that involves many different regions of the brain.     

Over-selectivity as a learned response

An experiment investigated the effects of different levels of task complexity in pre-training on over-selectivity in a subsequent match-to-sample (MTS) task. Twenty human participants were divided into two groups; exposed either to a 3-element, or a 9-element, compound stimulus as a sample during MTS training. After the completion of training, both groups were tested on an MTS task using a novel 6-element compound sample stimulus. The level of over-selectivity at test was influenced by the training. Specifically, the group exposed to a more complex (9-element) training task displayed higher levels of over-selectivity at test than the group with a less complex training task. The results suggest that over-selectivity may be a learned response to complex situations, and are discussed with respect to theories and treatments for over-selectivity.     

Neurophysiological correlates of learning disabilities in Japan]

In the present study, we developed a new event-related potentials (ERPs) stimulator system applicable to simultaneous audio visual stimuli, and tested it clinically on healthy adults and patients with learning disabilities (LD), using Japanese language task stimuli: hiragana letters, kanji letters, and kanji letters with spoken words. (1) The origins of the P300 component were identified in these tasks. The sources in the former two tasks were located in different areas. In the simultaneous task stimuli, a combination of the two P300 sources was observed with dominance in the left posterior inferior temporal area. (2) In patients with learning disabilities, those with reading and writing disability showed low amplitudes in the left hemisphere in response to visual language task stimuli with kanji and hiragana letters, in contrast to healthy children and LD patients with arithmetic disability. (3) To evaluate the effect of methylphenidate (10 mg) on ADD, paired-associate ERPs were recorded. Methylphenidate increased the amplitude of P300.     

Attentional deficits in cocaine-dependent patients: converging behavioral and electrophysiological evidence

Although there are several reports of patients with cocaine dependence displaying cognitive deficits, the nature of their information processing deficits is not well characterized. In the present study, the attentional performance of cocaine-dependent patients (n=14) was examined and compared with that of healthy control individuals (n=15). Attention was assessed using an auditory oddball event-related task as well as the Continuous Performance Test (CPT, Identical Pairs version). The cocaine-dependent group displayed P300 amplitude reduction compared to controls. The group difference in P300 response latency did not reach significance. On the CPT, the cocaine-dependent patients displayed significantly poorer discriminability and greater errors of commission than the controls. There was a positive correlation between performance on the oddball event-related task and performance on the CPT. This investigation provides converging behavioral and electrophysiological evidence of attentional deficits in cocaine-dependent patients.     

P300 to high intensity stimuli during REM sleep.

OBJECTIVES: The P300 component of the auditory event-related potential (ERP) is a large amplitude positive wave peaking at approximately 300 ms following detection of a rare significant stimulus. Although P300 is typically only evoked when the subject attends to the stimulus, it may also be elicited in an awake, inattentive subject if the stimulus is sufficiently intrusive. We therefore employed an oddball task to determine if high intensity stimuli would elicit the P300 during sleep. METHODS: A loud 90 dB SPL tone pip was presented infrequently (P = 0.05) in a train of lower intensity 70 dB SPL standard stimuli. A multiple channel EEG was recorded from 8 good sleepers during a single night. RESULTS: A large amplitude parieto-central P300, peaking at 321 ms, was apparent in REM sleep to the loud deviant stimulus. In stage two non-REM sleep, a later positive wave, peaking at 446 ms, was apparent even after K-Complexes were removed from the average. This non-REM P450 was however maximum over occipito-parietal areas of the scalp. CONCLUSION: The presence of a P300 in REM sleep following a loud, rare stimulus indicates that sensory discrimination capabilities remain intact during this state. This may be associated with either pre- or conscious processing of relevant stimuli.     

Visual P300 and the self-directedness scale of the Temperament and Character Inventory

Reduced amplitude of the P300 event-related brain potential has been associated with several psychopathological conditions and is thought to represent brain dysfunction in such conditions. Predisposition to personality disorders and psychopathology in general is also associated with low scores on the self-directedness (SD) scale of the Temperament and Character Inventory. The present preliminary study investigated the relationship between amplitudes of P300 elicited by rare target stimuli in a visual oddball task and SD scores in 58 healthy participants. P300 was found to be significantly reduced in subjects with low SD, as supported by correlational analysis and by comparison of groups formed on the basis of SD scores. This finding may be relevant to prior findings indicating reduced P300 amplitudes in a variety of psychopathological conditions and suggests that a common vulnerability factor, reflected in the low SD personality scores, may contribute to the P300 reduction in psychiatric populations.     

Brief Report: The Effect of Delayed Matching to Sample on Stimulus Over-Selectivity

Stimulus over-selectivity occurs when one aspect of the environment controls behavior at the expense of other equally salient aspects. Participants were trained on a match-to-sample (MTS) discrimination task. Levels of over-selectivity in a group of children (4-18 years) with Autism Spectrum Disorders (ASD) were compared with a mental-aged matched typically-developing group. There was more over-selectivity in the ASD group. When retention intervals were added between the sample and comparisons in the MTS task, both groups showed an increased level of over-selectivity, with the ASD group showing a more pronounced effect.     

Endogenous event-related potentials in obsessive-compulsive disorder

Brain event-related potentials (ERPs) were used to investigate central nervous system (CNS) correlates of cognitive function in obsessive-compulsive disorder (OCD). ERPs of 10 unmedicated OCD patients and 10 normal controls were measured in an auditory "oddball" task. Increasing task difficulty resulted in longer N200 and P300 latencies in normal subjects, but not in OCD patients. Moreover, OCD patients displayed shorter P300 latency than normal controls for the more difficult discrimination conditions. This replicates prior findings of Beech et al. (1983) for a visual task. For both levels of task difficulty, OCD patients also showed greater negativity than normal controls in the N200 region, which extended into the subsequent slow wave region. Negativities in the N200 and slow wave regions were larger at sites over the left hemisphere than the right hemisphere. The enhanced negativities and reduced P300 latency in OCD patients are discussed in terms of current theories postulating cortical hyperarousal and left hemisphere involvement in OCD.     

Contribution of subregions of human frontal cortex to novelty processing

Novelty processing was studied in patients with lesions centered in either OFC or lateral pFC (LPFC). An auditory novelty oddball ERP paradigm was applied with environmental sounds serving as task irrelevant novel stimuli. Lesions to the LPFC as well as the OFC resulted in a reduction of the frontal Novelty P3 response, supporting a key role of both frontal subdivisions in novelty processing. The posterior P3b to target sounds was unaffected in patients with frontal lobe lesions in either location, indicating intact posterior cortical target detection mechanisms. LPFC patients displayed an enhanced sustained negative slow wave (NSW) to novel sounds not observed in OFC patients, indicating prolonged resource allocation to task-irrelevant stimuli after LPFC damage. Both patient groups displayed an enhanced NSW to targets relative to controls. However, there was no difference in behavior between patients and controls suggesting that the enhanced NSW to targets may index an increased resource allocation to response requirements enabling comparable performance in the frontal lesioned patients. The current findings indicate that the LPFC and OFC have partly shared and partly differential contributions to the cognitive subcomponents of novelty processing.     

Alcoholism risk, tobacco smoking, and P300 event-related potential.

OBJECTIVE: The P300 event-related potential (ERP) is sometimes larger for individuals at low- compared to high-risk for alcoholism. These effects are inconsistent, and how P300 is affected by tobacco smoking in the context of alcoholism risk is unknown. The present study used P300 to examine the inter-relationship between alcoholism heritability and smoking status. METHODS: P300 was elicited with a visual discrimination task from young adults at low- and high-risk for alcoholism. Half of the subjects in each risk category reported that they did not smoke cigarettes, and the other half reported that they smoked regularly, with equal numbers of male and female subjects assessed. ERPs were recorded, and subjects were instructed to respond only to an infrequently presented target stimulus that occurred in a series of standard and distracter stimuli. RESULTS: P300 amplitude from the target stimuli was larger for the low-risk compared to high-risk subjects overall. However, smoking status demonstrated even stronger effects, with non-smokers producing consistently larger component amplitudes than smokers and accounting for more variance than alcoholism risk. These group factors also significantly affected P300 scalp topography. No reliable alcoholism risk or smoking group effects were obtained for the ERPs from the other stimuli. CONCLUSIONS: The findings suggest that P300 measures of alcoholism risk in young adults are moderated by smoking status. Theoretical implications are discussed.     

Association of DRD4 exon III polymorphism with auditory P300 amplitude in 8-year-old children

Summary. Objectives: The present study was designed to investigate the association between the DRD4 genotype and auditory P300 amplitudes in a high-risk community sample. Methods: ERPs were elicited in 197 eight-year-olds (98 boys, 99 girls) using a passive and an active oddball task. Auditory stimuli of 60 dB HL were presented binaurally at 1000 (standard stimulus) and 2000 Hz (target stimulus), at a relative frequency ratio of 80:20. Two trial blocks of 250 stimuli each were collected. P300 amplitudes were analyzed from Fz, Cz and Pz. DNA was genotyped for the DRD4 exon III polymorphism. Results: A pattern of significant interactions of the DRD4 genotype with gender and experimental conditions was obtained. In both the active and the passive task, boys with at least one copy of the DRD4 7-repeat allele displayed significantly lower P300 amplitudes during the second trial block than boys carrying other alleles. Conclusions: This finding provides further evidence supporting a role of P300 amplitude reduction as an endophenotype for disinhibited psychopathology.     

On how P300 amplitude varies with the utility of the eliciting stimuli.

The bulk of the relevant evidence indicates that stimuli which elicit the P300 component of the human event-related potential (ERP) tend to be unexpected and task relevant. Yet, contradictory evidence has been presented which implied that P300 amplitude is modulated by the intensity difference between two equally relevant, equally probable feedback stimuli (Adams and Benson, 1973). The two experiments reported here were designed to clarify this contradiction. Subjects were instructed to press a button one second after a cue light. A tone at one of two intensities was presented 200 msec later indicating whether the time estimate was 'correct' or 'incorrect'. The magnitude of P300 varied as a function of the difference in intensity between S+ and S-; the smaller the difference, the smaller was P300, regardless of stimulus meaning (S+ or S-). We attribute this effect to the degree to which the subject chooses to utilize the tones in the performance of the time estimation task. In support of this hypothesis, we found that performance of the subjects as time estimators degraded as the difference between S+ and S- decreased. Moreover, a study of choice reaction times taken for the different pairings of S+ and S- showed that the stimulus pairs were not equally discriminable. It appears that as the S+/S- pairs become increasingly difficult to discriminate, their feedback value decreased and this decrease is positively correlated with a decrease in P300 amplitude. This interpretation received support from Exp. 2 in which the stimulus conditions were the same as in Exp. 1, but the subject's task was to count the "s+ stimuli. Here, when subject had no option but to process each individual stimulus, the P300 amplitude remained constant despite variations in S- intensity. Thus, it appears that task relevance must be defined in terms of the subject's behavior rather than by the experimenter's instructions to the subject.     

Effects of practice on the P300 in a Go/NoGo task.

Previous studies have reported that there are differences in latency and scalp topography between Go-P300 and NoGo-P300 in a Go/NoGo task. This study investigated whether these differences could be observed after intensive practice. Subjects performed the task at 1 session (200 trials) per day for 6 days. In session 1, P300 latency was significantly later to the NoGo stimuli than to the Go stimuli, while in session 6 P300 latency was significantly shorter to the NoGo stimuli than to the Go stimuli. Reaction time (RT) was significantly shortened by practice, but P300 latency to the Go stimuli was not affected by practice. The scalp topography of the P300 was not varied by practice, having a parieto-central distribution to the Go stimuli, a centro-parietal one to the NoGo stimuli. These findings show that the temporal relation between Go-P300 and NoGo-P300 can be apparently reversed by practice. Since the Go-P300 differed from the NoGo-P300 in the effects of practice, our results suggest the possibility that the Go-P300 and the NoGo-P300 may be functionally separate P300 components.     

The P300 component decreases in a bimodal oddball task in individuals with depression: An event-related potentials study

Objective

In this study, we investigated auditory-visual stimulation-induced P300 and examined whether P300 was differentially modulated between individuals with clinical depression and healthy controls. We hypothesized that the P300 component would significantly differ between individuals with depression and healthy individuals Specifically, we predicted that the P300 component induced by the bimodal oddball task would be significantly different from that induced by the unimodal task.