Untrained Stimuli Research Articles

Training-induced attentional bias alters the appearance of both trained and untrained stimuli

Training-induced attentional bias alters the appearance of both trained and untrained stimuli

Magnetic stimulation of visual cortex impairs perceptual learning

The ability to learn and process visual stimuli more efficiently is important for survival. Previous neuroimaging studies have shown that perceptual learning on a shape identification task differently modulates activity in both frontal-parietal cortical regions and visual cortex (Sigman et al., 2005;Lewis et al., 2009). Specifically, fronto-parietal regions (i.e. intra parietal sulcus, pIPS) became less activated for trained as compared to untrained stimuli, while visual regions (i.e. V2d/V3 and LO) exhibited higher activation for familiar shape. Here, after the intensive training, we employed transcranial magnetic stimulation over both visual occipital and parietal regions, previously shown to be modulated, to investigate their causal role in learning the shape identification task. We report that interference with V2d/V3 and LO increased reaction times to learned stimuli as compared to pIPS and Sham control condition. Moreover, the impairment observed after stimulation over the two visual regions was positive correlated. These results strongly support the causal role of the visual network in the control of the perceptual learning.

Teaching foundational perspective-taking skills to children with autism using the PEAK-T curriculum: single-reversal "I-You" deictic frames.

We taught basic perspective-taking tasks to 3 children with autism and evaluated their ability to derive mutually entailed single-reversal deictic relations of those newly established perspective-taking skills. Furthermore, we examined the possibility of transfers of perspective-taking function to novel untrained stimuli. The methods were taken from the PEAK-T training curriculum, and results yielded positive gains for all 3 children to learn basic perspective taking as well as for 2 of the 3 to derive untrained single-reversal I relations following direct training of single-reversal You relations. All participants demonstrated a transfer of stimulus function to untrained stimuli after the single-reversal deictic relations had been mastered.

The effect of a script-fading procedure on social interactions among young children with autism

BackgroundAutism is a disorder characterized by a severe deficit in social-interaction skills. The script-fading procedure is an effective behavior-analytic strategy for teaching social-interaction skills to people with autism. Within the script-fading literature, however, few researchers have established cues in the natural environment as the discriminative stimuli for social interactions. MethodThe purpose of this study was to replicate the script-fading procedure used by Brown, Krantz, McClannahan, and Poulson (2008) to teach children with autism to interact with each other, and to assess generalization across untrained stimuli. The three participants, ages 6–9 years, demonstrated deficits in peer-interaction skills. ResultsDuring the baseline condition, the participants either did not interact with one another or emitted a variable and unreliable number of interactions. With the introduction of the script-fading procedure, however, interactions increased systematically. Moreover, stimulus generalization data indicated that the script-fading procedure effectively transferred the discriminative control for interacting from the scripts to stimuli in the natural environment. ConclusionsThese findings demonstrated the effectiveness of the script-fading procedure in teaching children with autism to interact with their peers. In addition, this study showed that establishing cues in the natural environment as discriminative stimuli for social interactions is a successful strategy to teach social-interaction skills to people with autism.

Transferability of Training Benefits Differs across Neural Events: Evidence from ERPs.

Humans can show striking capacity limitations in sensorimotor processing. Fortunately, these limitations can be attenuated with training. However, less fortunately, training benefits often remain limited to trained tasks. Recent behavioral observations suggest that the extent to which training transfers may depend on the specific stage of information processing that is being executed. Training benefits for a task that taps the consolidation of sensory information (sensory encoding) transfer to new stimulus-response mappings, whereas benefits for selecting an appropriate action (decision-making/response selection) remain specific to the trained mappings. Therefore, training may have dissociable influences on the neural events underlying subsequent sensorimotor processing stages. Here, we used EEG to investigate this possibility. In a pretraining baseline session, participants completed two four-alternative-choice response time tasks, presented both as a single task and as part of a dual task (with another task). The training group completed a further 3,000 training trials on one of the four-alternative-choice tasks. Hence, one task became trained, whereas the other remained untrained. At test, a negative-going component that is sensitive to sensory-encoding demands (N2) showed increased amplitudes and reduced latencies for trained and untrained mappings relative to a no-train control group. In contrast, the onset of the stimulus-locked lateralized readiness potential, a component that reflects the activation of motor plans, was reduced only for tasks that employed trained stimulus-response mappings, relative to untrained stimulus-response mappings and controls. Collectively, these results show that training benefits are dissociable for the brain events that reflect distinct sensorimotor processing stages.

Alpha-band EEG activity in perceptual learning.

In studies of perceptual learning (PL), subjects are typically highly trained across many sessions to achieve perceptual benefits on the stimuli in those tasks. There is currently significant debate regarding what sources of brain plasticity underlie these PL-based learning improvements. Here we investigate the hypothesis that PL, among other mechanisms, leads to task automaticity, especially in the presence of the trained stimuli. To investigate this hypothesis, we trained participants for eight sessions to find an oriented target in a field of near-oriented distractors and examined alpha-band activity, which modulates with attention to visual stimuli, as a possible measure of automaticity. Alpha-band activity was acquired via electroencephalogram (EEG), before and after training, as participants performed the task with trained and untrained stimuli. Results show that participants underwent significant learning in this task (as assessed by threshold, accuracy, and reaction time improvements) and that alpha power increased during the pre-stimulus period and then underwent greater desynchronization at the time of stimulus presentation following training. However, these changes in alpha-band activity were not specific to the trained stimuli, with similar patterns of posttraining alpha power for trained and untrained stimuli. These data are consistent with the view that participants were more efficient at focusing resources at the time of stimulus presentation and are consistent with a greater automaticity of task performance. These findings have implications for PL, as transfer effects from trained to untrained stimuli may partially depend on differential effort of the individual at the time of stimulus processing.

Specificity of motion discrimination learning even with double training and staircase.

Visual perceptual learning has been traditionally characterized by its specificity. Namely, learning transfers little to many untrained stimulus attributes. This result of specificity is the basis for the inference that perceptual learning takes place in low-level visual areas in the brain. Recently, however, Xiao and colleagues (2008) demonstrated a double training technique that enabled complete transfer of learning in all tasks that were tested. This technique has since been applied to motion direction discrimination learning. Learning along one average direction has been found to transfer completely to a new average direction, along which only dot number discrimination had been trained (J. Y. Zhang & Yang, 2014). In the current study, we first repeated the J. Y. Zhang and Yang (2014) experiment in exact procedure, stimuli, and task. We then continued the double training to examine transfer in longer-term perceptual learning. To our surprise, in both our exact replication attempt and in our longer-term learning study, we could not find complete transfer. In fact, the transfer to the dot number discrimination direction was no greater than to an untrained control direction. We suggest that individual differences and subtle differences in experimental setup between J. Y. Zhang and Yang (2014) and our studies are too strong and common to determine whether or not the new double training technique can bring about complete transfer in motion discrimination learning.

Effects of production training and perception training on lexical tone perception – A behavioral and ERP study

The present study recorded both behavioral data and event-related brain potentials to examine the effectiveness of a perception-only training and a perception-plus-production training procedure on the intentional and unintentional perception of lexical tone by native English listeners. In the behavioral task, both the perception-only and the perception-plus-production groups improved on the tone discrimination abilities after the training session. Moreover, the participants in both groups generalized the improvements gained through the trained stimuli to the untrained stimuli. In the ERP task, the Mismatch Negativity was smaller in the post-training task than in the pre-training task. However, the two training groups did not differ in tone processing at the intentional or unintentional level after training. These results suggest that the employment of the motor system does not specifically benefit the tone perceptual skills. Furthermore, the present study investigated whether some tone pairs are more easily confused than others by native English listeners, and whether the order of tone presentation influences non-native tone discrimination. In the behavioral task, Tone2-Tone1 (rising-level) and Tone2-Tone4 (rising-falling) were the most difficult tone pairs, while Tone1-Tone2 and Tone4-Tone2 were the easiest tone pairs, even though they involved the same tone contrasts respectively. In the ERP task, the native English listeners had good discrimination when Tone2 and Tone4 were embedded in strings of Tone1, while poor discrimination when Tone1 was inserted in the context of Tone2 or Tone4. These asymmetries in tone perception might be attributed to the interference of native intonation system and can be altered by training.

Improving Vision Among Older Adults

A major problem for the rapidly growing population of older adults (age 65 and over) is age-related declines in vision, which have been associated with increased risk of falls and vehicle crashes. Research suggests that this increased risk is associated with declines in contrast sensitivity and visual acuity. We examined whether a perceptual-learning task could be used to improve age-related declines in contrast sensitivity. Older and younger adults were trained over 7 days using a forced-choice orientation-discrimination task with stimuli that varied in contrast with multiple levels of additive noise. Older adults performed as well after training as did college-age younger adults prior to training. Improvements transferred to performance for an untrained stimulus orientation and were not associated with changes in retinal illuminance. Improvements in far acuity in younger adults and in near acuity in older adults were also found. These findings indicate that behavioral interventions can greatly improve visual performance for older adults.

The effects of stimulus variability on the perceptual learning of speech and non-speech stimuli.

Previous studies suggest fundamental differences between the perceptual learning of speech and non-speech stimuli. One major difference is in the way variability in the training set affects learning and its generalization to untrained stimuli: training-set variability appears to facilitate speech learning, while slowing or altogether extinguishing non-speech auditory learning. We asked whether the reason for this apparent difference is a consequence of the very different methodologies used in speech and non-speech studies. We hypothesized that speech and non-speech training would result in a similar pattern of learning if they were trained using the same training regimen. We used a 2 (random vs. blocked pre- and post-testing) × 2 (random vs. blocked training) × 2 (speech vs. non-speech discrimination task) study design, yielding 8 training groups. A further 2 groups acted as untrained controls, tested with either random or blocked stimuli. The speech task required syllable discrimination along 4 minimal-pair continua (e.g., bee-dee), and the non-speech stimuli required duration discrimination around 4 base durations (e.g., 50 ms). Training and testing required listeners to pick the odd-one-out of three stimuli, two of which were the base duration or phoneme continuum endpoint and the third varied adaptively. Training was administered in 9 sessions of 640 trials each, spread over 4–8 weeks. Significant learning was only observed following speech training, with similar learning rates and full generalization regardless of whether training used random or blocked schedules. No learning was observed for duration discrimination with either training regimen. We therefore conclude that the two stimulus classes respond differently to the same training regimen. A reasonable interpretation of the findings is that speech is perceived categorically, enabling learning in either paradigm, while the different base durations are not well-enough differentiated to allow for categorization, resulting in disruption to learning.

Failure to observe untested derived stimulus relations in extinction: implications for understanding stimulus-equivalence formation.

Wilson and Hayes (1996) and Doughty, Kastner, and Bismark (2011) observed resurgence of past equivalence relations when newer equivalence relations were punished or extinguished, respectively. Their findings support the notion that deriving stimulus relations is a form of operant behavior. Although there is consensus regarding the operant nature of deriving untrained stimulus relations, the necessary and sufficient conditions that establish these relations remain unclear. For example, in the aforementioned work, the resurgent equivalence relations were tested earlier in each study. The present research investigated whether this resurgence of equivalence relations requires their initial testing. In Experiment 1, college students received arbitrary matching-to-sample training in Phase 1. After these baseline discriminations were established, equivalence testing was omitted. In Phase 2, four 4-member equivalence classes were established that were inconsistent with the Phase-1 training. These Phase-2 relations then were extinguished to test whether the equivalence relations consistent with Phase-1 training would occur. Unlike in earlier research, these untested relations did not occur reliably. This finding was replicated in Experiment 2, and additional tests of stimulus relatedness did not reveal any evidence of derived stimulus relations consistent with the Phase-1 training. The present research extends other findings suggesting that the equivalence-testing context helps establish these stimulus classes.

Plasticity in developing brain: active auditory exposure impacts prelinguistic acoustic mapping.

A major task across infancy is the creation and tuning of the acoustic maps that allow efficient native language processing. This process crucially depends on ongoing neural plasticity and keen sensitivity to environmental cues. Development of sensory mapping has been widely studied in animal models, demonstrating that cortical representations of the sensory environment are continuously modified by experience. One critical period for optimizing human language mapping is early in the first year; however, the neural processes involved and the influence of passive compared with active experience are as yet incompletely understood. Here we demonstrate that, while both active and passive acoustic experience from 4 to 7 months of age, using temporally modulated nonspeech stimuli, impacts acoustic mapping, active experience confers a significant advantage. Using event-related potentials (ERPs), we show that active experience increases perceptual vigilance/attention to environmental acoustic stimuli (e.g., larger and faster P2 peaks) when compared with passive experience or maturation alone. Faster latencies are also seen for the change discrimination peak (N2*) that has been shown to be a robust infant predictor of later language through age 4 years. Sharpening is evident for both trained and untrained stimuli over and above that seen for maturation alone. Effects were also seen on ERP morphology for the active experience group with development of more complex waveforms more often seen in typically developing 12- to 24-month-old children. The promise of selectively "fine-tuning" acoustic mapping as it emerges has far-reaching implications for the amelioration and/or prevention of developmental language disorders.

Beyond blindsight: properties of visual relearning in cortically blind fields.

Damage to the primary visual cortex (V1) or its immediate afferents results in a dense scotoma, termed cortical blindness (CB). CB subjects have residual visual abilities, or blindsight, which allow them to detect and sometimes discriminate stimuli with high temporal and low spatial frequency content. Recent work showed that with training, discriminations in the blind field can become more reliable, and even reach consciousness. However, the narrow spatiotemporal bandwidth of blindsight limits its functional usefulness in everyday vision. Here, we asked whether visual training can induce recovery outside the spatiotemporal bandwidth of blindsight. Specifically, could human CB subjects learn to discriminate static, nonflickering stimuli? Can such learning transfer to untrained stimuli and tasks, and does double training with moving and static stimuli provide additional advantages relative to static training alone? We found CB subjects capable of relearning static orientation discriminations following single as well as double training. However, double training with complex, moving stimuli in a separate location was necessary to recover complex motion thresholds at locations trained with static stimuli. Subjects trained on static stimuli alone could only discriminate simple motion. Finally, both groups had approximately equivalent, incomplete recovery of fine orientation and direction discrimination thresholds, as well as contrast sensitivity. These results support two conclusions: (1) from a practical perspective, complex moving stimuli and double training may be superior training tools for inducing visual recovery in CB, and (2) the cortically blind visual system can relearn to perform a wider range of visual discriminations than predicted by blindsight alone.

Generalization of negatively reinforced mands in children with autism.

Each day, people encounter stimuli they find unpleasant. Some children with autism may require systematic instruction to acquire the communication skills necessary to request the termination of such aversive stimuli. We taught 2 school-aged boys with autism a mand (e.g., signing "stop") that could be used to escape a variety of aversive stimuli. First, we employed a systematic assessment to identify aversive stimuli to use during training. We then conducted mand training sequentially across those stimuli until sufficient exemplars were trained for generalization to occur to untrained stimuli. For both participants, cross-stimulus generalization was observed after training with 2 stimuli. Participants manded for escape in the presence of aversive stimuli, but almost never manded in the presence of preferred stimuli or when the programmed stimuli were absent. In addition, we found an inverse relation between acquisition of the mand and engagement in problem behavior and evidence of generalization to nontraining contexts.

Transposition and its generalization in common marmosets.

Whether animals use relational cues in transposition tests has long been considered a controversial issue. In the present study, we examined whether common marmosets could generalize relational responses to untrained stimulus pairs and further apply these generalizations to unknown shapes. The subjects were trained to perform simple discrimination tasks using a pair of stimuli. The stimuli differed in size, and the subjects were required to select the larger or smaller of the 2 sizes, depending on the given contingencies. After experiencing several reversals, the subjects were examined using 2 different tests: transposition and shape generalization. In the transposition test trials, in which squares of different sizes than those used in the training trials were presented, the subjects selected the stimulus based on the relative size of the stimulus. In the shape generalization tests, sets of 5 novel shapes with the same relative sizes were presented with the training stimuli. The subjects' performance indicated successful transposition to the novel stimulus pairs, and further analysis showed that transposition was more likely to occur when the test stimuli shared physical features, such as the outer length and the number of line segments, with the trained stimuli. Thus, the present study demonstrated the robust ability of transposition in common marmosets based on relative size, both with and without common shape features, and offered a possible method for specifying the critical stimulus features through which transposition can be more readily observed.

Computer-based intervention for inferring facial expressions from the socio-emotional context in two children with autism spectrum disorders

Difficulties in understanding others’ emotions have been widely reported in autism spectrum disorders (ASDs). Many methodologies for evaluating the emotion recognition can be analyzed by matching-to-sample (MTS) procedures. When using movies of socio-emotional situations as sample stimuli, children with ASD have been found to have difficulties in understanding them. Furthermore, there are few intervention studies that have targeted understanding of socio-emotional situations in children with ASD. The present study examined whether two young children with ASD can acquire the relationships between movies of socio-emotional situations and pictures of facial expressions through computer-based MTS training. The movies of situations and pictures of facial expressions represented happy, surprised, angry and sad emotions. The child with ASD was required to select the picture of facial expression when presented with the movie of socio-emotional situations as a sample stimulus, and if so, whether these skills can be generalized to untrained stimuli. We used a multiple baseline design across participants, and the results demonstrated that both children learned the relationships and improved their performance with untrained stimuli. These findings are discussed in terms of procedures to increase the understanding of others’ emotions at an early developmental stage.

Visualizing cross sections: Training spatial thinking using interactive animations and virtual objects

In two experiments, we investigated the efficacy of a brief intervention that used interactive animation to train students to infer the two-dimensional cross section of a virtual three-dimensional geometric figure. Undergraduates with poor spatial ability were assigned to receive the intervention or to a control group. Compared to the control group, trained participants improved significantly on stimuli viewed during the intervention and demonstrated transfer to untrained stimuli. Results were considered with respect to two accounts of performance gains and transfer after spatial visualization training, an instance-based account and a process-based account. The instance-based account attributes performance gains to a larger store of memories and predicts no transfer to new stimuli or new spatial processes. The process-based account attributes performance gains to increased efficiency of mental processes and predicts transfer to new stimuli and tasks that share the same mental processes. The results of these experiments cannot be accounted for by an instance-based account alone. Performance gains and transfer in these experiments suggest that interactive animation and virtual solids are promising tools for training spatial thinking in undergraduates.

Dissociable mechanisms of speed-accuracy tradeoff during visual perceptual learning are revealed by a hierarchical drift-diffusion model.

Two phenomena are commonly observed in decision-making. First, there is a speed-accuracy tradeoff (SAT) such that decisions are slower and more accurate when instructions emphasize accuracy over speed, and vice versa. Second, decision performance improves with practice, as a task is learnt. The SAT and learning effects have been explained under a well-established evidence-accumulation framework for decision-making, which suggests that evidence supporting each choice is accumulated over time, and a decision is committed to when the accumulated evidence reaches a decision boundary. This framework suggests that changing the decision boundary creates the tradeoff between decision speed and accuracy, while increasing the rate of accumulation leads to more accurate and faster decisions after learning. However, recent studies challenged the view that SAT and learning are associated with changes in distinct, single decision parameters. Further, the influence of speed-accuracy instructions over the course of learning remains largely unknown. Here, we used a hierarchical drift-diffusion model to examine the SAT during learning of a coherent motion discrimination task across multiple training sessions, and a transfer test session. The influence of speed-accuracy instructions was robust over training and generalized across untrained stimulus features. Emphasizing decision accuracy rather than speed was associated with increased boundary separation, drift rate and non-decision time at the beginning of training. However, after training, an emphasis on decision accuracy was only associated with increased boundary separation. In addition, faster and more accurate decisions after learning were due to a gradual decrease in boundary separation and an increase in drift rate. The results suggest that speed-accuracy instructions and learning differentially shape decision-making processes at different time scales.

The influence of training on the attentional blink and psychological refractory period

A growing body of research suggests that dual-task interference in sensory consolidation (e.g., the attentional blink, AB) and response selection (e.g., the psychological refractory period, PRP) stems from a common central bottleneck of information processing. With regard to response selection, it is well known that training reduces dual-task interference. We tested whether training that is known to be effective for response selection can also reduce dual-task interference in sensory consolidation. Over two experiments, performance on a PRP paradigm (Exp. 1) and on AB paradigms (differing in their stimuli and task demands, Exps. 1 and 2) was examined after participants had completed a relevant training regimen (T1 practice for both paradigms), an irrelevant training regimen (comparable sensorimotor training, not related to T1 for both tasks), a visual-search training regimen (Exp. 2 only), or after participants had been allocated to a no-training control group. Training that had shown to be effective for reducing dual-task interference in response selection was also found to be effective for reducing interference in sensory consolidation. In addition, we found some evidence that training benefits transferred to the sensory consolidation of untrained stimuli. Collectively, these findings show that training benefits can transfer across cognitive operations that draw on the central bottleneck in information processing. These findings have implications for theories of the AB and for the design of cognitive-training regimens that aim to produce transferable training benefits.

The effect of computerised Verb Network Strengthening Treatment on lexical retrieval in aphasia

Background: A number of computerised treatments have been developed for aphasia, but few have remediated typing, an important functional task, and/or been implemented over the Internet via teletherapy, which can increase access to therapeutic services. The current study created a computerised version of Verb Network Strengthening Treatment (VNeST) and administered it via telerehabilitation over the Internet. VNeST is a semantic treatment which seeks to improve lexical retrieval of words through the conceptual connection between verbs and thematic roles. Previous iterations of VNeST have shown improvement in both spoken and written lexical retrieval for people with moderate and moderate-to-severe aphasia.Aims: This study investigates changes to lexical retrieval with four hierarchical outcome measures. The research questions were: Does treatment using Computerised VNeST (VNeST-C) result in pre- to post-treatment increases in: (1) spoken and typed lexical retrieval of trained (e.g., The farmer is weighing the apples.) and untrained words (e.g., The carpenter is measuring the lumber.) in a picture description task, (2) untreated single-word naming accuracy of nouns and verbs in spoken and typed modalities, (3) spoken and typed lexical retrieval as measured by informative words, efficiency of production and complete utterances within discourse, and (4) standardised measures of cognitive and language abilities?Methods & Procedures: Two people with aphasia were treated three times per week for 8 weeks using the VNeST-C program. A single-subject experimental design was used to evaluate changes in trained and untrained stimuli and tasks. Additional pre-treatment and post-treatment testing was also conducted.Outcomes & Results: Results indicate improvements on lexical retrieval during sentence production of trained and untrained stimuli. Additional improvement was observed for single-word naming of untrained nouns and verbs in spoken and typed modalities and standardised measures of aphasia and writing-by-hand. Limited generalisation to discourse was also observed, including a general increase in word output and decrease in typed neologisms.Conclusions: The results of this study suggest that the VNeST-C program and protocol have promise as a broadly generalising treatment for people with aphasia. With refinement of duration and intensity of the protocol, it may be a viable option for treating aphasia.