The neural bases of price estimation: Effects of size and precision of the estimate.

People are often confronted with the need of estimating the market price of goods. An important question is how people estimate prices, given the variability of products and prices available. Using event-related fMRI, we investigated how numerical processing modulates the neural bases of retail price estimation by focusing on two numerical dimensions: the size and precision of the estimates. Participants were presented with several product labels and made market price estimates for those products. Measures of product buying frequency and market price variability were also collected. The estimation of higher prices required longer response times, was associated with greater variation in responses across participants, and correlated with increasing medial and lateral prefrontal cortex (PFC) activity. Moreover, price estimates followed Weber's law, a hallmark feature of numerical processing. Increasing accuracy in price estimation, indexed by decreasing Weber fraction, engaged the intraparietal sulcus (IPS), a critical region in numerical processing. Our findings provide evidence for distinguishable neural mechanisms associated with the size and the precision of price estimates.

Concept typicality responses in the semantic memory network.

For decades concept typicality has been recognized as critical to structuring conceptual knowledge, but only recently has typicality been applied in better understanding the processes engaged by the neurological network underlying semantic memory. This previous work has focused on one region within the network - the Anterior Temporal Lobe (ATL). The ATL responds negatively to concept typicality (i.e., the more atypical the item, the greater the activation in the ATL). To better understand the role of typicality in the entire network, we ran an fMRI study using a category verification task in which concept typicality was manipulated parametrically. We argue that typicality is relevant to both amodal feature integration centers as well as category-specific regions. Both the Inferior Frontal Gyrus (IFG) and ATL demonstrated a negative correlation with typicality, whereas inferior parietal regions showed positive effects. We interpret this in light of functional theories of these regions. Interactions between category and typicality were not observed in regions classically recognized as category-specific, thus, providing an argument against category specific regions, at least with fMRI.

Visual naming deficits in dyslexia: An ERP investigation of different processing domains.

Naming speed deficits are well documented in developmental dyslexia, expressed by slower naming times and more errors in response to familiar items. Here we used event-related potentials (ERPs) to examine at what processing level the deficits in dyslexia emerge during a discrete-naming task. Dyslexic and skilled adult control readers performed a primed object-naming task, in which the relationship between the prime and the target was manipulated along perceptual, semantic and phonological dimensions. A 3×2 design that crossed Relationship Type (Visual, Phonemic Onset, and Semantic) with Relatedness (Related and Unrelated) was used. An attenuated N/P190 - indexing early visual processing - and N300 - which index late visual processing - was observed to pictures preceded by perceptually related (vs. unrelated) primes in the control but not in the dyslexic group. These findings suggest suboptimal processing in early stages of object processing in dyslexia, when integration and mapping of perceptual information to a more form-specific percept in memory take place. On the other hand, both groups showed an N400 effect associated with semantically related pictures (vs. unrelated), taken to reflect intact integration of semantic similarities in both dyslexic and control readers. We also found an electrophysiological effect of phonological priming in the N400 range - that is, an attenuated N400 to objects preceded by phonemic related primes vs. unrelated - while it showed a more widespread distributed and more pronounced over the right hemisphere in the dyslexics. Topographic differences between groups might have originated from a word form encoding process with different characteristics in dyslexics compared to control readers.

Preserved Proactive Interference in Autism Spectrum Disorder.

In this study, we aimed to evaluate further the functioning and structuring of the semantic system in autism spectrum disorders (ASD). We analyzed the performance of 19 high-functioning young adults with ASD and a group of 20 age-, verbal IQ- and education-matched individuals with the Proactive Interference (PI) Paradigm to evaluate semantic functioning in ASD (Experiment 1). In Experiment 2, we analyzed the performances of both groups in a PI paradigm with manipulation of the level of typicality. In both experiments, we observed significant effects of trial and group but no trial by group interactions, which we interpreted as robust evidence of preserved PI (build up effect) that indicated the preservation of semantic mechanisms of encoding and retrieval.

Verbal fluency as a function of time in autism spectrum disorder: An impairment of initiation processes?

In the present study, we aimed to evaluate the hypothesis that the reported discrepancy in the performance of verbal fluency in individuals with autism spectrum disorder (ASD), characterized by an overall word productivity impairment with normal clustering and switching abilities, may be due to an initiation deficit. In the present study, we evaluated the temporal dynamics of both letter and semantic verbal fluency tasks in a sample of 20 young adults with high-functioning ASD compared with a sample of 20 gender-, age-, education-, and verbal-IQ-matched participants. We first compared both the word productivity and the qualitative analysis of clustering and switching abilities during the entire task to replicate the discrepancy reported in the literature. Importantly, we next analyzed both word productivity and clustering and switching abilities in two time intervals (0-30 s and 31-60 s), as it was our primary interest to evaluate the functioning of the initial component of word retrieval. Directly supporting the idea that the discrepancy found between an impairment in global word productivity combined with normal clustering and switching strategies is due to an activation and initiation deficit, we observed an abnormal performance for the ASD group in the first time period only. We interpreted these results to be preliminary findings of deficits in initiation processes in ASD.

Grasping with the eyes: the role of elongation in visual recognition of manipulable objects.

Processing within the dorsal visual stream subserves object-directed action, whereas visual object recognition is mediated by the ventral visual stream. Recent findings suggest that the computations performed by the dorsal stream can nevertheless influence object recognition. Little is known, however, about the type of dorsal stream information that is available to assist in object recognition. Here, we present a series of experiments that explored different psychophysical manipulations known to bias the processing of a stimulus toward the dorsal visual stream in order to isolate its contribution to object recognition. We show that elongated-shaped stimuli, regardless of their semantic category and familiarity, when processed by the dorsal stream, elicit visuomotor grasp-related information that affects how we categorize manipulable objects. Elongated stimuli may reduce ambiguity during grasp preparation by providing a coarse cue to hand shaping and orientation that is sufficient to support action planning. We propose that this dorsal-stream-based analysis of elongation along a principal axis is the basis for how the dorsal visual object processing stream can affect categorization of manipulable objects.

The contribution of fronto-parietal regions to sentence comprehension: insights from the Moses illusion.

To interpret a sentence, the reader must not only process the linguistic input, but many times has also to draw inferences about what is implicitly stated. In some cases, the generation and integration of inferred information may lead to semantic illusions. In these sentences, subjects fail to detect errors such as in "It was two animals of each kind that Moses took on the ark" despite knowing that the correct answer is Noah, not Moses. The relative inability to notice these errors raises questions about how people establish and integrate inferences and which conditions improve error detection. To unravel the neural processes underlying inference and error detection in language comprehension, we carried out an fMRI study in which participants read sentences containing true or false statements. The false statements either took the form of more obvious (i.e., clearly false) or subtle (i.e., semantic illusions) inconsistent relations. Participants had to decide if each statement was true or false. Processing semantic illusions relative to true and clearly false sentences significantly engaged the right inferior parietal lobule, suggesting higher demands in establishing coherence. Successful versus unsuccessful error detection revealed a network of regions, including right dorsolateral prefrontal cortex, orbitofrontal, insula/putamen and anterior cingulate cortex. Such activation was significantly correlated with overall response accuracy to the illusions. These results suggest that to detect the semantic conflict, people must inhibit the tendency to draw pragmatic inferences. These findings demonstrate that fronto-parietal areas are involved in inference and inhibition processes necessary for establishing semantic coherence.

The role of feature sharedness in the organization of semantic knowledge: insights from semantic dementia.

OBJECTIVE: The present study directly evaluated the impact of feature sharedness on the differences between superordinate and basic-level concepts observed in semantic dementia (SD) patients. METHOD: For this purpose, we studied a group of 6 SD patients and a group of 12 matched controls using a sentence verification task in which we orthogonally manipulated feature sharedness (more vs. less shared) and concept level (basic level vs. superordinate). RESULTS: Main results showed that the superordinate advantage in SD patients was observed for more shared features but not for less shared features (p < .05, η(p)2 = .36). CONCLUSION: These results directly support the role of feature sharedness in explaining the hierarchical organization of semantic knowledge and the specific to general pattern of knowledge deterioration in SD in particular.

Structural processing and category-specific deficits.

We evaluated the contribution of four structural dimensions (object parts, internal details, objects contours and variability of the representation), as a possible source of categorical processing differences and category-specific deficits. Importantly, these dimensions aggregate 22 different structural measures that have been proposed to describe the Snodgrass and Vanderwart (1980) picture set. Study 1 analysed the differences between the four dimensions across domains and categories. Study 2 investigated how these dimensions may contribute to the performance of two patients with category-specific deficits that have been reported previously in the literature (Farah et al., 1991). The results showed that living things were structurally more complex than non-living things, scoring higher in object parts and object contours. Regarding the variability of the representation, living things did not show much within-item diversity but did show more contour overlap and less visual similarity, the latter two qualities of living things being detrimental to object processing in a naming task. Parts, contours and variability of the representation also differentiated animals, fruits and vegetables and, to a certain degree, non-living things: animals had more parts, fruits had more object contours and non-living things had a lower variability of the representation (which was especially related to higher within-item diversity and lower contour overlap). The same three dimensions predicted patient performance. However, when structural dimensions were considered together with domain (living/non-living) and concept familiarity, only variability of the representation contributed significantly to patient performance.

The contributions of language and experience to the representation of abstract and concrete words: different weights but similar organizations.

In the present studies, we evaluated the contributions of language and sensorimotor information to the representation of abstract and concrete words and the possibility that the organizations of the two types of concepts follow different organizational principles: association, for abstract concepts, and semantic similarity, for concrete concepts. In Study 1, we examined the two strongest associates of concrete and abstract words from published free association norms. Study 2 then extended this analysis to individual data collected with a free association task. Language associations were more important for abstract than for concrete words, but for sensorimotor information no differences were observed between the two types of concepts. Also, no clear evidence was found for different qualitative organizational principles for abstract and concrete concepts. Multiple representational systems thus seem to be engaged in the conceptual processing of abstract and concrete concepts, while it remains to be investigated whether their representations follow different organizational principles.

Sensitivity and salience of form-function correlations of objects: evidence from feature tasks.

The present research evaluates the sensitivity and salience of form-function correlations in contrast with other types of feature correlations (function-function, form-form) in adults and using real object features (from tools and utensils). In Experiment 1, the participants judged the relation between the form and function features of tools. In Experiment 2, participants were asked to generate a second feature related to a given form or function feature. In Experiment 3, participants were asked to make a lexical decision in which form and function features were used as primes and targets. The results showed that even though participants were sensitive to form-function correlations, these were not particularly salient when compared with other feature-type correlations, notably function-function correlations. Our data underline the overall importance of function information to object representations and the impact of the statistical co-occurrence of features when processing object features.

The hierarchical organization of semantic memory: executive function in the processing of superordinate concepts.

Research on the processing of objects at different hierarchical levels has suggested that understanding superordinate concepts (e.g. fruit), relative to basic level concepts (e.g. apple), requires greater semantic control demands. Yet, it is unclear which factors underlie this difference in executive processing. We built on previous research showing that superordinate concepts have less shared features among their members and therefore may involve higher semantic control requirements. To test this hypothesis, we developed an fMRI study in which we orthogonally manipulated feature sharedness (more shared vs. less shared) and concept level (superordinate vs. basic) in a sentence verification task. Sentences involving less shared features, relative to more shared features, significantly engaged the L lateral PFC. Importantly, sentences that included superordinate concepts, relative to those with basic level concepts, also revealed a stronger response in L lateral PFC, along with posterior temporal gyrus activation. There was also a significant interaction between feature sharedness and concept level in several PFC regions and L posterior temporal areas. The results suggest that relative to basic level concepts, processing superordinate concepts requires extra semantic control in L lateral PFC to coordinate information that is less shared by other members of the category level. These findings demonstrate that feature sharedness impacts the neural basis of semantic knowledge, and is a critical dimension in the processing of superordinate concepts.

Naming from definition, semantic relevance and feature type: the effects of aging and Alzheimer's disease.

OBJECTIVE: The principal aim of the present study was to evaluate the impact of semantic relevance and feature type on the ability to name from definition. METHOD: Thirty-two normal young subjects (Study 1) and 20 probable Alzheimer's disease patients (pAD) with 20 matched older controls (Study 2) were tested with verbal definitions consisting of 4 features, combining feature type (sensory vs. nonsensory) and semantic relevance (high vs. low). The subjects were asked to provide a name corresponding to the definition and to select which individual features they considered most important in justifying their answer. RESULTS: Feature selection results showed that high-relevance features first (d = 2.13 in Study 1; d = 1.44 in Study 2) and nonsensory features second (d = 0.81 in Study 1; d = 0.36 in Study 2) were the main dimensions driving correct performance. Overall, naming performance was affected by the age of acquisition (AoA) of the concept, and differences between the groups in all measures were mainly quantitative. CONCLUSIONS: These findings suggest that semantic relevance and feature type are important feature dimensions in conceptual representation and in conceptual access and retrieval. Moreover, results suggest that the former dimension may be more important than the latter, at least in the case of naming from definition. Finally, these results extend previous findings with other tasks, supporting the importance of AoA for correct performance and suggesting that the poorer performance of pAD patients on semantic tasks may represent an exaggeration of difficulties found also in normal older subjects.

The effect of visual deprivation on the organization of conceptual knowledge: testing the grounded cognition hypothesis.

The present paper evaluates the effect of visual deprivation on the organization and retrieval of conceptual knowledge. The experimental study used the release from proactive interference (PI-release) paradigm. Early onset blind (EOB) and sighted (S) subjects were tested with this task and additional visual and nonvisual property retrieval cues. PI-release results showed that the visual cue was less effective for EOB individuals than for S individuals, whereas the nonvisual cue was similarly effective for EOB individuals and S individuals. Results support a grounded view of cognition where the organization of conceptual knowledge depends on the role that sensory and motor channels play in its acquisition.

Neural differences in the processing of true and false sentences: insights into the nature of 'truth' in language comprehension.

The inquiry on the nature of truth in language comprehension has a long history of opposite perspectives. These perspectives either consider that there are qualitative differences in the processing of true and false statements, or that these processes are fundamentally the same and only differ in quantitative terms. The present study evaluated the processing nature of true and false statements in terms of patterns of brain activity using event-related functional-Magnetic-Resonance-Imaging (fMRI). We show that when true and false concept-feature statements are controlled for relation strength/ambiguity, their processing is associated to qualitatively different processes. Verifying true statements activates the left inferior parietal cortex and the caudate nucleus, a neural correlate compatible with an extended search and matching process for particular stored information. In contrast, verifying false statements activates the fronto-polar cortex and is compatible with a reasoning process of finding and evaluating a contradiction between the sentence information and stored knowledge.

Conceptual knowledge in the brain: fMRI evidence for a featural organization.

The organization and representation of conceptual knowledge in the brain remains a controversial issue in terms of both neuropsychological and imaging evidence. We report the results of a functional magnetic resonance study in which the role of the most debated dimensions (domain and feature type) was evaluated through a concept-feature verification task. The scope of the task was to eliminate serious methodological concerns that weighed down previous imaging research in this area, and to allow more definitive conclusions regarding the specific contribution of these dimensions. The results show differential patterns of brain activity according to feature type (both motion and visual form/surface features) but not according to concept domain (living vs. nonliving things). These findings are in accord with a modality-specific account of conceptual knowledge organization in the brain, in which specific kinds of features (e.g. form, color, motion, etc) have differential importance for representing different concepts.

The general/specific breakdown of semantic memory and the nature of superordinate knowledge: insights from superordinate and basic-level feature norms.

The deterioration of semantic memory usually proceeds from more specific to more general superordinate categories, although rarer cases of superordinate knowledge impairment have also been reported. The nature of superordinate knowledge and the explanation of these two semantic impairments were evaluated from the analysis of superordinate and basic-level feature norms. The results show that, in comparison to basic-level concepts, superordinate concepts are not generally less informative and have similar feature distinctiveness and proportion of individual sensory features, but their features are less shared by their members. Results are in accord with explanations based on feature connection weights and/or concept confusability for the superordinate advantage cases. Results especially support an explanation for superordinate impairments in terms of higher semantic control requirements as related to features being less shared between concept members. Implications for patients with semantic impairments are also discussed.

Estimated age of acquisition norms for 834 Portuguese nouns and their relation with other psycholinguistic variables.

The main objective of this study is to report rated age of acquisition (AoA) norms for 834 nouns in Portuguese (European). AoA ratings were collected on a 7 point scale, generally following Gilhooly and Logie (1980) procedure with an 8 extra point for "don't know the word" answers. Results were analyzed considering AoA ratings and their standard deviations and considering the relationship between AoA ratings and other psycholinguistic variables (imageability, familiarity, written word frequency, concreteness, number of syllables and number of words). AoA ratings and their standard deviations were significantly and positively correlated, with early acquired word ratings showing higher agreement. Correlation and multiple regression analyses confirmed the major contribution of imageability and familiarity to AoA ratings obtained in other languages. The full database of AoA ratings and other psycholinguistic variables may be downloaded from www.psychonomic.org/archive or www.fpce.ul.pt/pessoal/ulfpfred/aoa.htm.

Specialization and semantic organization: evidence for multiple semantics linked to sensory modalities.

The present article reviews the case for multiple systems in semantic memory and empirically evaluates a multiple semantics proposal based on sensory modalities. In the experiments, a conceptual switching cost paradigm was used (Pecher, Zeelenberg, & Barsalou, 2003), in which participants verified properties for concepts and verification time was compared for target trials (e.g., a dog can bark) that were preceded by context trials of either the same or a different modality (e.g., a bee can buzz or a horse can have spots). Experiment 1 involved a modality switch while controlling for the concept's category and demonstrated that when modalities were switched, a processing cost was incurred that could not be attributed to the latter dimension. Experiment 2 further supported this conclusion by showing that, in a reverse situation, the cost incurred when category was switched was at least smaller. The results are discussed by considering possible alternative amodal explanations and other data that have shown the influence of sensory information in conceptual processing.