Perceptual Matching Research Articles

Picture recognition without picture identification: A method for assessing the role of perceptual information in familiarity-based picture recognition

The present study examined the claim that unidentifiable test-pictures are processed and recognized on a perceptual, as opposed to a conceptual, level. Using an extension of the recognition without identification paradigm (e.g., Cleary, A. M. & Greene, R. L. (2000). Recognition without identification. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 1063–1069; Peynircioglu, Z. F. (1990). A feeling-of-recognition without identification. Journal of Memory and Language, 29, 493–500), it was observed that when test-pictures were unidentifiable during a masked perceptual identification task, old-new discrimination occurred when the study-list consisted of pictures (Experiments 1–3), but not when the study-list consisted of picture names (Experiment 2) or when picture exemplars served as test-cues (Experiment 3). Results provide converging evidence that a study-test perceptual match is needed for the episodic recognition of unidentified test-pictures. Implications for the present paradigm as a tool for examining the role of perceptual information in recognition-familiarity are discussed.

Visual–spatial ability and fMRI cortical activation in surgery residents

Background We previously reported that a particular type of visual–spatial ability, mental rotation of visual forms, correlates with surgical performance in residents. In the current study, we used functional magnetic resonance imaging (fMRI) to identify patterns of cortical activation associated with mental rotation ability in those same residents. Methods Seventeen surgery residents underwent fMRI scan while performing a mental rotations test (MRT) and a perceptual matching task as a control (CON) for nonimagery components, such as visual attention. A contrast analysis (MRT greater than CON) revealed cortical regions engaged during mental rotation by all participants, and parametric statistical analysis identified regions having the strongest association with MRT performance. Results Significant bilateral (left greater than right) activation was seen in all participants for rotation-versus-perceptual CON contrast. Better MRT performance was associated with greater activation in several cortical regions related to visual imagery and motion processing. Comments Surgery residents represent a unique population in which to study individual differences in visual–spatial abilities and associated neural substrates because they may relate to technical skills. These findings suggest that variation in performance on spatially complex tasks involving imagery may reflect different spatial problem-solving strategies in surgery students.

Comparison of cognitive functions between people with silent and wild-type butyrylcholinesterase

In the human brain, butyrylcholinesterase (BuChE) is expressed in neurons and glia. For example, many nuclei in the human thalamus, with projections to the cerebral cortex, contain a large number of neurons with intense BuChE activity. Thalamocortical projections subserve a variety of cognitive functions. Due to genetic mutations, there are individuals who do not have detectable BuChE activity (silent BuChE). While the prevalence of silent BuChE is only 1:100,000 in European and American populations, it is 1:24 in the Vysya community in Coimbatore, India. To examine whether there are differences in cognitive functions between individuals with silent BuChE and those expressing normal BuChE (wild-type), twelve healthy individuals with silent BuChE and thirteen healthy individuals with wild-type BuChE, all from the Vysya community in Coimbatore, were tested for cognitive function using the Automated Neuropsychological Assessment Metrics test battery. The silent BuChE group was slightly faster on simple reaction tasks, but slower on a visual perceptual matching task. Furthermore, discriminant function analyses correctly classified 11/12 silent and 8/13 wild-type BuChE subjects (76% correct classification overall) based on BuChE status. Different profiles of cognitive test performance between individuals with silent and wild-type BuChE were observed. These observations suggest a function for BuChE in cognition.

Left size distortion (hyperschematia) after right brain damage

To quantitate a size distortion involving the side of space contralateral to the lesion (contralesional) in two right-brain-damaged patients. We studied two right-brain-damaged patients with lesions sparing the occipital lobe and a mild left neglect on target cancellation or line bisection. The lesions involved the temporoparietal region (Patient 1) and the basal ganglia and the insula (Patients 1 and 2). Patients were given drawing tasks and tasks requiring perceptual and visuomotor judgments of horizontal extent. In drawing objects such as a daisy both from memory and by copying, patients exhibited a disproportionate enlargement of the left-hand side of objects and added more left-sided petals to the drawn daisy. This pathologic behavior persisted when the patients were blindfolded and was likely to reflect a perceptual, rather than premotor, size distortion. In a task requiring the perceptual matching of two rectangles, patients underestimated the left-sided stimulus. In a visuomotor task requiring the reproduction of the horizontal extent of a segment, patients exhibited a hyperextension, when a leftward movement was required. We showed a disordered representation of extrapersonal space, possibly involving a contralesional relaxation of the spatial medium. The deficit does not arise at the level of retinotopic coordinate frames and is independent of unilateral spatial neglect.

Exemplar effects in the context of a categorization rule: Featural and holistic influences.

Brooks and colleagues (S. W. Allen & L. R. Brooks, 1991; G. Regehr & L. R. Brooks, 1993) have shown that the classification of transfer stimuli is influenced by their similarity to training stimuli, even when a perfect classification rule is available. It is argued that the original effect obtained by Brooks and colleagues might have resulted from two potential confounding variables. Once these confounds were controlled, the current authors did not replicate Brooks and colleagues' results in Experiment 1. Exemplar effects appeared in Experiment 2 when transfer stimuli were perceptually more similar to training stimuli than in Experiment 1. In Experiment 3, the authors obtained exemplar effects with separated stimuli, a finding that was not predicted by Brooks and colleagues' model. The authors suggest that a close perceptual match between training and transfer stimuli is necessary for the effect to occur, for both integrated and separated stimuli. The nature of this perceptual match, holistic or featural, is discussed.

Aspects of Pain, Its Assessment and Evaluation from An Acupuncture Perspective

Pain is a major clinical problem that causes great suffering for the individual and incurs costs for society. Accurate assessment and evaluation of perceived pain is necessary for diagnosis, for choice of treatment, and for the evaluation of treatment efficacy. The assessment of an individual's pain is a challenge since pain is a subjective, multidimensional experience, and assessment is based on the person's own self-report. The results are often varied, possibly due to inter-individual variation, but also in relation to gender and aetiology. A gold standard for pain assessment is still lacking, but rating scales, questionnaires, and methods derived from psychophysical concepts, such as threshold assessments and perceptual matching, are used. In the evaluation of pain and associated variables, both systematic and individual variation should be taken into account, as should pain-associated symptoms. Recommendations for pain treatment should be based on the patient's specific needs. Therefore, it is important to assess the level of perceived pain taking individual variation into account. The methods used should preferably have proved to be useful in randomised controlled trials, and analysis of pain assessment should consider its non-metric properties. In the future, the use of studies with a naturalistic protocol together with individual assessment of individual pain responses could increase the internal and external validity.

Masked and unmasked electrophysiological repetition effects of famous faces

We investigated immediate repetition effects of sequentially presented famous face pairs. The first face (F1) was presented masked or unmasked and preceded the second face (F2) with different SOAs (84 ms vs. 500 ms). Participants judged F2 with regard to either semantic category (actor vs. singer; indirect task) or perceptual match with F1 (same vs. different; direct task). Repetition shortened RT for unmasked but not for masked F1 conditions. In event-related brain potentials (ERPs), unmasked repetition effects were influenced by task and SOA and consisted a modulation of an occipitotemporal N170, an inferior temporal N250r (200–300 ms), a central–parietal N400 (300–500 ms), and a parietal P600 (500–800 ms). An early occipital negativity (onset ∼ 100 ms) was present at the 84-ms SOA but diminished in the 500-ms SOA condition, probably reflecting a fast decaying iconic memory trace. Masked repetition effects in the indirect task were limited to a significant early (100–150 ms) prefrontal/lateral frontal and central–parietal modulation, and a strong trend for a reduced N170 amplitude. This suggests that masked repetition modulated early visual processing but did not influence processes beyond ∼ 200 ms that reflect the access to facial representations and semantic information for people.

FMRI correlates of cortical specialization and generalization for letter processing

The present study used functional magnetic resonance imaging to examine cortical specialization for letter processing. We assessed whether brain regions that were involved in letter processing exhibited domain-specific and/or mandatory responses, following Fodor's definition of properties of modular systems (Fodor, J.A., 1983. The Modularity of Mind. The MIT Press, Cambridge, MA.). Domain-specificity was operationalized as selective, or exclusive, activation for letters relative to object and visual noise processing and a baseline fixation task. Mandatory processing was operationalized as selective activation for letters during both a silent naming and a perceptual matching task. In addition to these operational definitions, other operational definitions of selectivity for letter processing discussed by [Pernet, C., Celsis, P., Demonet, J., 2005. Selective response to letter categorization within the left fusiform gyrus. NeuroImage 28, 738–744] were applied to the data. Although the left fusiform gyrus showed a specialized response to letters using the definition of selectivity put forth by [Pernet, C., Celsis, P., Demonet, J., 2005. Selective response to letter categorization within the left fusiform gyrus. NeuroImage 28, 738–744], this region did not exhibit specialization for letters according to our more conservative definition of selectivity. Instead, this region showed equivalent activation by letters and objects in both the naming and matching tasks. Hence, the left fusiform gyrus does not exhibit domain-specific or mandatory processing but may reflect a shared input system for both stimulus types. The left insula and some portions of the left inferior parietal lobule, however, did show a domain-specific response for letter naming but not for letter matching. These regions likely subserve some linguistically oriented cognitive process that is unique to letters, such as grapheme-to-phoneme translation or retrieval of phonological codes for letter names. Hence, cortical specialization for letters emerged in the naming task in some peri-sylvian language related cortices, but not in occipito-temporal cortex. Given that the domain-specific response for letters in left peri-sylvian regions was only present in the naming task, these regions do not process letters in a mandatory fashion, but are instead modulated by the linguistic nature of the task.

The Role of Pitch Memory in Pitch Discrimination and Pitch Matching

Accurate control of vocal pitch (fundamental frequency) requires coordination of sensory and motor systems. Previous research has supported the relationship between perceptual accuracy and vocal pitch matching accuracy. The purpose of this study was to investigate the role of memory for pitch in pitch matching and pitch discrimination ability. Three experimental tasks were used. First, a pitch matching task was completed, in which the participants listened to target tones and vocally matched the pitch of the tones. The second task was a pitch discrimination task that required the participants to judge the pitch (same or different) of complex tone pairs. The third task was pitch discrimination with memory interference task that was similar to the pitch discrimination task except interference tones were added. Results of the pitch matching and pitch discrimination tasks yielded a significant correlation between these values. When there was memory interference, pitch discrimination ability was poorer, and there was no significant correlation between pitch discrimination and pitch matching. These results support earlier findings of a relationship between pitch discrimination and pitch matching abilities. The results also suggest a possible role of pitch memory in both tasks. These findings may have implications for abilities related to accurate pitch control.

Between- and Within-Individual Effects of Visual Contrast Sensitivity on Perceptual Matching, Processing Speed, and Associative Memory in Older Adults

Background: Although cross-sectional studies have demonstrated associations between visual contrast sensitivity and cognitive test performance, it remains unclear whether peripheral visual or perceptual factors explain the association. Objective: We aimed at determining whether reducing static contrast of the study stimuli would simulate the performance deficits on measures of processing speed and associative memory that are associated with aging. Methods: We investigated the mechanism by which vision and memory are associated in a sample of 91 volunteers aged 60–87 years. In tests of perceptual matching, digit-symbol matching, and associative memory, the level of static contrast of the stimuli was manipulated, with three contrast levels. The duration of stimuli presentation was also manipulated in the associative memory task in a full-factorial experimental design. Accuracy and response latencies (for correct trials) were measured. Results: Experimental results showed that within subjects, lower contrast was associated with longer latencies, indicating an effect on information processing speed. Regression analyses replicated previous findings of a moderate to strong association between visual contrast sensitivity and cognitive performance in cross-sectional studies. Conclusion: These results provide support for a theory in which visual aging is associated with slower encoding of information as well as being involved at a more central level.

On perceptual distortion minimization and nonlinear least-squares frequency estimation

In this paper, we present a framework for perceptual error minimization and sinusoidal frequency estimation based on a new perceptual distortion measure, and we state its optimal solution. Using this framework, we relate a number of well-known practical methods for perceptual sinusoidal parameter estimation such as the prefiltering method, the weighted matching pursuit, and the perceptual matching pursuit. In particular, we derive and compare the sinusoidal estimation criteria used in these methods. We show that for the sinusoidal estimation problem, the prefiltering method and the weighted matching pursuit are equivalent to the perceptual matching pursuit under certain conditions.

The time course of perception and retrieval in matching and recognition.

A four-part experiment was carried out to study the relationship between the time course of object-feature perception and the time course of retrieval of object information from memory. The experiment consisted of 2 perceptual matching tasks, and 2 perceptual recognition tasks. In all 4 tasks, participants provided speeded judgments of the identity of 2 objects. A stochastic feature-sampling model was used to estimate the time needed for feature perception and the time needed for retrieval of feature information. No evidence was found for a systematic relationship between perception times and retrieval times for individual features. Indeed, the model applications indicated that retrieval times were constant for different features, whereas perception rates varied across the features.

The Cingulate as a Catalyst Region for Global Dysfunction: a Dynamical Modelling Paradigm

The anterior cingulate (AC) often exhibits both structural and functional abnormalities in affective disorders. Neither the cause for this vulnerability nor its effect on behaviour is known. Due to its extensive connectivity, minor output changes from the AC may exert widespread consequences. A causal model describing coupling coefficients (effective connectivity) among several brain regions in healthy subjects performing a memory task inspired our work. This stationary causal analysis provides a theoretical framework for our nonlinear dynamical models. We tested the effects of global and local perturbations upon stability of a systems-level neural network of interconnected brain regions. Interactions between regions, represented by path coefficients, were modelled using connectivity matrices. We found that both characteristic behaviour and response to perturbation differed in networks representing perceptual matching and long-delay conditions. Owing to the highly interconnected character of the networks, activation of a few areas was sufficient to trigger characteristic patterns of behaviour. However, only perturbation of key regions resulted in global dysfunction. Likewise, recovery of function was possible by increasing output from some, but not all, regions. We suggest for this recovery to be context specific, conditional on the task, integrity of other regions and global properties such as neuronal excitability.

A comparison of the BOLD fMRI response to achromatic, L/M opponent and S-cone opponent cardinal stimuli in human visual cortex: I. perceptually matched vs contrast matched stimuli

Aims: Our primary aim was to compare the responsiveness of the different visual cortical areas to stimulation of the two cone opponent systems and the achromatic system. The appropriate contrast metric for the comparison of color and luminance sensitivity is unknown, however, and so our secondary aim was to investigate whether equivalent fMRI responses of each cortical area could better be predicted from perceptual matches (in multiples of detection threshold) or a direct contrast match (in cone contrast). Methods:MR images were acquired on a 4T Bruker MedSpec. Stimuli were sinewave counter-phasing rings (2Hz, 0.5cpd) cardinal for the selective activation of the L/M cone opponent (RG), S cone opponent (BY) and achromatic (Ach) systems. In different scans, stimuli were matched either at 25x detection threshold or in cone contrast (6%). We performed both stereotaxic and region of interest analyses on early visual areas (V1-V4v, and hMT+). Results: For stimuli presented in multiples of detection threshold, BOLD responses in areas V1, V2, V3/VP and V4v are greatest for BY stimuli and weaker for both RG and achromatic stimuli, with the BY response significantly higher than the RG. For the same stimuli matched in cone contrast, the RG and BY response is similar in these areas. The averaged color response (RG & BY) was no different from the achromatic response with the exception of V1, which had a greater averaged color than achromatic response. Conclusions:Perceptual visibility is not a good indicator of cortical activity across the RG, BY and achromatic mechanisms. fMRI BOLD signals are better predicted by cone contrast. Regardless of the metric, our data suggest a similar response to color (averaged RG & BY) and achromatic stimuli in V2, V3, VP and V4v. V1 shows a greater response to color, particularly with the cone contrast metric. Areas hMT+ and V3A do not follow these patterns and are discussed in a related abstract (Dumoulin et al).

Early processing deficits in object working memory in first-episode schizophreniform psychosis and established schizophrenia

While there are many studies showing working-memory deficits in schizophrenia there are only a few that disentangle impairments for working-memory subprocesses such as perceptual, attentional, mnemonic and executive function. In this study of delay-dependent memory, 55 patients with schizophreniform psychosis, 50 with established schizophrenia and 56 healthy controls were investigated. Using the delayed matching-to-sample task from the Cambridge Neuropsychological Test Automated Battery (CANTAB), performance deficits were found in both patient groups after controlling for age and pre-morbid IQ. Even after controlling for simultaneous matching-to-sample ability (i.e. perceptual matching), impaired performance in both patient groups was found as soon as the stimuli were no longer present. Impaired performance was not due to different types of errors in patients versus controls. Performance in both patient groups was comparable, except for a slight decrease of overall task performance. This suggests that the deficit is relatively stable during the course of the illness. Our results suggest a deficit in patients with psychotic illness in the initial processes necessary to actively maintain information, such as the ability to form an internal representation of complex objects.

Perceptual matching of identity between faces and video

Perceptual matching of identity between faces and video

Towards robot cultures?

The study of imitation and other mechanisms of social learning is an exciting area of research for all those interested in understanding the origin and the nature of animal learning in a social context. Moreover, imitation is an increasingly important research topic in Artificial Intelligence and social robotics which opens up the possibility of individualized social intelligence in robots that are part of a community, and allows us to harness not only individual learning by the single robot, but also the acquisition of new skills by observing other members of the community (robots, humans, or virtual agents). After an introduction to the main research issues in research on imitation in various fields (including psychology, biology and robotics), we motivate the particular focus of this work, namely the correspondence problem. We describe Action Learning for Imitation via Correspondences between Embodiments (Alice), an implemented generic framework for solving the correspondence problem between differently embodied robots. Alice enables a robotic agent to learn a behavioral repertoire suitable to performing a task by observing a model agent. Importantly, the model agent could possibly possess a different type of body, e.g. a different number of limbs or joints (implying different degrees of freedom), a different height, different sensors, a different basic action repertoire, etc. Previously, in a test-bed where the agents differed according to their possible movement patterns, we demonstrated that the character of imitation achieved will depend on the granularity of subgoal matching, and on the metrics used to evaluate success. In our current work, we implemented Alice in a new test-bed called Rabit where simple simulated robotic arm agents use various metrics for evaluating success according to actions, states, effects, or weighted combinations. We examine the roles of synchronization, looseness of perceptual matching, and of proprioceptive matching by a series of experiments. Also, we study how Alice copes with changes in the embodiment of the imitator during learning. Our simulation results suggest that synchronization and loose perceptual matching allow for faster acquisition of behavioral compentencies at low error rates. Social learning (broadly construed) plays a role as a replication mechanism for behaviors and results in variability when the transmitted behavior differs from the model’s behavior, thus providing the evolutionary substrate for culture and its pre-cursors. Social learning in robotics could therefore serve as the basis for culture in societies whose members include artificial agents. We address the use of imitative social learning mechanisms like Alice for transmission of skills between robots, and give first examples of transmission of a skill despite differences in embodiment of agents involved. In the particular setup, transmission occurs through a chain, as well as emerging in cyclic arrangements of robots. These simple examples demonstrate that by using social learning and imitation, (proto-)cultural transmission is possible among robots, even in heterogeneous groups of robots.

Perception-action interaction and bissection

Several studies using visually directed actions as indicators of perceived distance showed that people could accurately walk toward targets far up to 22m. Those results, summed up to those related to perceptual measures of perceived distance, showed that those responses were controlled by a single internal variable, namely visually perceived location. In the present study, we compared performance in bisection tasks, performed by open-loop walking or by perceptual matching. Observers (N=20) walked toward or adjust a pointer to the mean point of an egocentric distance (5, 10 or 15m), under binocular viewing. Results indicated accuracy on both responses, with no reliable differences between them, supporting the hypothesis of a single internal variable controlling action and perception. This invariant may be determined by a weighted set of sources of information.

Neural correlates of implicit object identification

The present study sought to assess neural correlates of implicit identification of objects by means of fMRI, using tasks that require matching of the physical properties of objects. Behavioural data suggests that there is automatic access to object identity when observers attend to a physical property of the form of an object (e.g. the object’s orientation) and no evidence for semantic processing when subjects attend to colour. We evaluated whether, in addition to neural areas associated with decisions to specific perceptual properties, areas associated with access to semantic information were activated when tasks demanded processing of the global configuration of pictures. We used two perceptual matching tasks based on the global orientation or on the colour of line drawings. Our results confirmed behavioural data. Activations in the inferior occipital cortex, fusiform and inferior temporal gyri in both tasks (orientation and colour) account for perceptual and structural processing involved in each task. In contrast, activations in the posterior and medial parts of the fusiform gyrus, shown to be involved in explicit semantic judgements, were more pronounced in the orientation-matching task, suggesting that semantic information from the pictures is processed in an implicit way even when not required by the task. Thus, this study suggests that cortical regions usually involved in explicit semantic processing are also activated when implicit processing of objects occurs.

Perceptual Matching for Assessment of Itch; Reliability and Responsiveness Analyzed by a Rank-Invariant Statistical Method

The aim of this study was to evaluate the reliability and responsiveness of a new device-perceptual matching by Matcher (Cefar Medical AB, Lund, Sweden)-in the assessment of the progress of experimentally induced itch as well as determine the reliability of the method in patients with skin disease and itch. The perceptual matching unit electrically stimulates the skin of the fingers in the left hand. When the amplitude of the sensation corresponded to that of the experienced itch, the subject was instructed to halt the stimulation and a value was automatically saved in the electronic device. A total of 36 healthy subjects and nine patients participated in the study. The healthy subjects were asked to rate the level of itch every 30 s during the first 5 min and thereafter every minute. The reliability was determined in a test-retest procedure of the time points 5, 10, and 15 min after induction of itching. To test the stability of the method, the first sensation of pain in healthy subjects without itch was determined every 10th minute during 60 min. In patients, the test-retest procedure was repeated within 5 min. Perceptual matching was found to be a reliable method of itch assessment, with no evidence for random individual disagreement between the assessments. The augmented rank order coefficient ra was excellent: 1.00 at 5 min; 0.99 at 10 min; and 1.00 at 15 min. There was a clear indication of responsiveness for detecting changes in itch over time, p<or=0.05. The perceptual matcher device can detect immediate changes in perceived itch and is also sensitive to gradual decreases after the induction of itch. The first sensation of pain in healthy subjects without itch was unaffected when assessed every 10th minute during 60 min. In patients, no evidence for random disagreement or systematic disagreement by group between repeated assessments was detected. The augmented rank order coefficient was high (0.98). In conclusion, Matcher measures itch intensity via perceptual matching with a high reliability and excellent responsiveness. The method is stable and can be recommended as an assessment tool for itch intensity both in experimental conditions as well as in patients with skin disease and itch.