RESUMO
CRISPR-Cas defense systems have been coopted multiple times in nature for guide RNA-directed transposition by Tn7-like elements. Prototypic Tn7 uses dedicated proteins for two targeting pathways: one targeting a neutral and conserved attachment site in the chromosome and a second directing transposition into mobile plasmids facilitating cell-to-cell transfer. We show that Tn7-CRISPR-Cas elements evolved a system of guide RNA categorization to accomplish the same two-pathway lifestyle. Multiple mechanisms allow functionally distinct guide RNAs for transposition: a conventional system capable of acquiring guide RNAs to new plasmid and phage targets and a second providing long-term memory for access to chromosomal sites upon entry into a new host. Guide RNAs are privatized to be recognized only by the transposon-adapted system via sequence specialization, mismatch tolerance, and selective regulation to avoid toxic self-targeting by endogenous CRISPR-Cas defense systems. This information reveals promising avenues to engineer guide RNAs for enhanced CRISPR-Cas functionality for genome modification.
Assuntos
Sistemas CRISPR-Cas/genética , Elementos de DNA Transponíveis/genética , RNA Guia de Cinetoplastídeos/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Gammaproteobacteria/metabolismo , Filogenia , Regiões Promotoras Genéticas/genética , Fatores de Transcrição/metabolismo , Zigoto/metabolismoRESUMO
Humans' capacity to predict actions and to socially categorize individuals is at the basis of social cognition. Such capacities emerge in early infancy. By 6 months of age, infants predict others' reaching actions considering others' epistemic state. At a similar age, infants are biased to attend to and interact with more familiar individuals, considering adult-like social categories such as the language people speak. We report that these two core processes are interrelated early on in infancy. In a belief-based action prediction task, 6-month-old infants (males and females) presented with a native speaker generated online predictions about the agent's actions, as revealed by the activation of participants' sensorimotor areas before the agent's movement. However, infants who were presented with a foreign speaker did not recruit their motor system before the agent's action. The eyetracker analysis provided further evidence that linguistic group familiarity influences how infants predict others' actions, as only infants presented with a native speaker modified their attention to the stimuli as a function of the agent's forthcoming behavior. The current findings suggest that infants' emerging capacity to predict others' actions is modulated by social cues, such as others' linguistic group. A facilitation to predict and encode the actions of native speakers relative to foreign speakers may explain, in part, why infants preferentially attend to, imitate, and learn from the actions of native speakers.
Assuntos
Sinais (Psicologia) , Movimento , Masculino , Lactente , Adulto , Feminino , Humanos , Movimento/fisiologia , Idioma , Linguística , EletroencefalografiaRESUMO
Categorization is an essential cognitive and perceptual process, which happens spontaneously. However, earlier research often neglected the spontaneous nature of this process by mainly adopting explicit tasks in behavioral or neuroimaging paradigms. Here, we use frequency-tagging (FT) during electroencephalography (EEG) in 22 healthy human participants (both male and female) as a direct approach to pinpoint spontaneous visual categorical processing. Starting from schematic natural visual stimuli, we created morph sequences comprising 11 equal steps. Mirroring a behavioral categorical perception discrimination paradigm, we administered a FT-EEG oddball paradigm, assessing neural sensitivity for equally sized differences within and between stimulus categories. Likewise, mirroring a behavioral category classification paradigm, we administered a sweep FT-EEG oddball paradigm, sweeping from one end of the morph sequence to the other, thereby allowing us to objectively pinpoint the neural category boundary. We found that FT-EEG can implicitly measure categorical processing and discrimination. More specifically, we could derive an objective neural index of the required level to differentiate between the two categories, and this neural index showed the typical marker of categorical perception (i.e., stronger discrimination across as compared with within categories). The neural findings of the implicit paradigms were also validated using an explicit behavioral task. These results provide evidence that FT-EEG can be used as an objective tool to measure discrimination and categorization and that the human brain inherently and spontaneously (without any conscious or decisional processes) uses higher-level meaningful categorization information to interpret ambiguous (morph) shapes.
Assuntos
Eletroencefalografia , Percepção Visual , Humanos , Masculino , Feminino , Encéfalo , Cabeça , Estimulação Luminosa/métodosRESUMO
Current studies investigating electroencephalogram correlates associated with categorization of sensory stimuli (P300 event-related potential, alpha event-related desynchronization, theta event-related synchronization) typically use an oddball paradigm with few, familiar, highly distinct stimuli providing limited insight about the aspects of categorization (e.g. difficulty, membership, uncertainty) that the correlates are linked to. Using a more complex task, we investigated whether such more specific links could be established between correlates and learning and how these links change during the emergence of new categories. In our study, participants learned to categorize novel stimuli varying continuously on multiple integral feature dimensions, while electroencephalogram was recorded from the beginning of the learning process. While there was no significant P300 event-related potential modulation, both alpha event-related desynchronization and theta event-related synchronization followed a characteristic trajectory in proportion with the gradual acquisition of the two categories. Moreover, the two correlates were modulated by different aspects of categorization, alpha event-related desynchronization by the difficulty of the task, whereas the magnitude of theta -related synchronization by the identity and possibly the strength of category membership. Thus, neural signals commonly related to categorization are appropriate for tracking both the dynamic emergence of internal representation of categories, and different meaningful aspects of the categorization process.
Assuntos
Eletroencefalografia , Potenciais Evocados P300 , Humanos , Aprendizagem , Sincronização CorticalRESUMO
Humans make sense of the world by organizing things into categories. When and how does this process begin? We investigated whether real-world object categories that spontaneously emerge in the first months of life match categorical representations of objects in the human visual cortex. Using eye tracking, we measured the differential looking time of 4-, 10-, and 19-mo-olds as they looked at pairs of pictures belonging to eight animate or inanimate categories (human/nonhuman, faces/bodies, real-world size big/small, natural/artificial). Taking infants' looking times as a measure of similarity, for each age group, we defined a representational space where each object was defined in relation to others of the same or of a different category. This space was compared with hypothesis-based and functional MRI-based models of visual object categorization in the adults' visual cortex. Analyses across different age groups showed that, as infants grow older, their looking behavior matches neural representations in ever-larger portions of the adult visual cortex, suggesting progressive recruitment and integration of more and more feature spaces distributed over the visual cortex. Moreover, the results characterize infants' visual categorization as an incremental process with two milestones. Between 4 and 10 mo, visual exploration guided by saliency gives way to an organization according to the animate-inanimate distinction. Between 10 and 19 mo, a category spurt leads toward a mature organization. We propose that these changes underlie the coupling between seeing and thinking in the developing mind.
Assuntos
Cognição/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Adulto , Fatores Etários , Mapeamento Encefálico/métodos , Tecnologia de Rastreamento Ocular , Feminino , Fixação Ocular/fisiologia , Humanos , Lactente , Imageamento por Ressonância Magnética/métodos , Masculino , Estimulação Luminosa , Pensamento/fisiologia , Visão Ocular/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologiaRESUMO
Actions can be planned and recognized at different hierarchical levels, ranging from very specific (e.g., to swim backstroke) to very broad (e.g., locomotion). Understanding the corresponding neural representation is an important prerequisite to reveal how our brain flexibly assigns meaning to the world around us. To address this question, we conducted an event-related fMRI study in male and female human participants in which we examined distinct representations of observed actions at the subordinate, basic and superordinate level. Using multiple regression representational similarity analysis (RSA) in predefined regions of interest, we found that the three different taxonomic levels were best captured by patterns of activations in bilateral lateral occipitotemporal cortex (LOTC), showing the highest similarity with the basic level model. A whole-brain multiple regression RSA revealed that information unique to the basic level was captured by patterns of activation in dorsal and ventral portions of the LOTC and in parietal regions. By contrast, the unique information for the subordinate level was limited to bilateral occipitotemporal cortex, while no single cluster was obtained that captured unique information for the superordinate level. The behaviorally established action space was best captured by patterns of activation in the LOTC and superior parietal cortex, and the corresponding neural patterns of activation showed the highest similarity with patterns of activation corresponding to the basic level model. Together, our results suggest that occipitotemporal cortex shows a preference for the basic level model, with flexible access across the subordinate and the basic level.SIGNIFICANCE STATEMENT The human brain captures information at varying levels of abstraction. It is debated which brain regions host representations across different hierarchical levels, with some studies emphasizing parietal and premotor regions, while other studies highlight the role of the lateral occipitotemporal cortex (LOTC). To shed light on this debate, here we examined the representation of observed actions at the three taxonomic levels suggested by Rosch et al. (1976) Our results highlight the role of the LOTC, which hosts a shared representation across the subordinate and the basic level, with the highest similarity with the basic level model. These results shed new light on the hierarchical organization of observed actions and provide insights into the neural basis underlying the basic level advantage.
Assuntos
Lobo Occipital , Lobo Temporal , Humanos , Masculino , Feminino , Lobo Occipital/fisiologia , Lobo Temporal/fisiologia , Mapeamento Encefálico , Córtex Cerebral/fisiologia , Lobo Parietal , Imageamento por Ressonância Magnética , Reconhecimento Visual de Modelos/fisiologiaRESUMO
Neural activity in the lateral intraparietal cortex (LIP) correlates with both sensory evaluation and motor planning underlying visuomotor decisions. We previously showed that LIP plays a causal role in visually-based perceptual and categorical decisions, and preferentially contributes to evaluating sensory stimuli over motor planning. In that study, however, monkeys reported their decisions with a saccade to a colored target associated with the correct motion category or direction. Since LIP is known to play a role in saccade planning, it remains unclear whether LIP's causal role in such decisions extend to decision-making tasks which do not involve saccades. Here, we employed reversible pharmacological inactivation of LIP neural activity while two male monkeys performed delayed match to category (DMC) and delayed match to sample (DMS) tasks. In both tasks, monkeys needed to maintain gaze fixation throughout the trial and report whether a test stimulus was a categorical match or nonmatch to the previous sample stimulus by releasing a touch bar. LIP inactivation impaired monkeys' behavioral performance in both tasks, with deficits in both accuracy and reaction time (RT). Furthermore, we recorded LIP neural activity in the DMC task targeting the same cortical locations as in the inactivation experiments. We found significant neural encoding of the sample category, which was correlated with monkeys' categorical decisions in the DMC task. Taken together, our results demonstrate that LIP plays a generalized role in visual categorical decisions independent of the task-structure and motor response modality.SIGNIFICANCE STATEMENT Neural activity in the lateral intraparietal cortex (LIP) correlates with perceptual and categorical decisions, in addition to its role in mediating saccadic eye movements. Past work found that LIP is causally involved in visual decisions that are rapidly reported by saccades in a reaction time based decision making task. Here we use reversible inactivation of LIP to test whether LIP is also causally involved in visual decisions when reported by hand movements during delayed matching tasks. Here we show that LIP inactivation impaired monkeys' task performance during both memory-based discrimination and categorization tasks. These results demonstrate that LIP plays a generalized role in visual categorical decisions independent of the task-structure and motor response modality.
Assuntos
Lobo Parietal , Movimentos Sacádicos , Masculino , Animais , Lobo Parietal/fisiologia , Fixação Ocular , Tempo de Reação/fisiologia , Estimulação LuminosaRESUMO
Models of visual cognition generally assume that brain networks predict the contents of a stimulus to facilitate its subsequent categorization. However, understanding prediction and categorization at a network level has remained challenging, partly because we need to reverse engineer their information processing mechanisms from the dynamic neural signals. Here, we used connectivity measures that can isolate the communications of a specific content to reconstruct these network mechanisms in each individual participant (N = 11, both sexes). Each was cued to the spatial location (left vs right) and contents [low spatial frequency (LSF) vs high spatial frequency (HSF)] of a predicted Gabor stimulus that they then categorized. Using each participant's concurrently measured MEG, we reconstructed networks that predict and categorize LSF versus HSF contents for behavior. We found that predicted contents flexibly propagate top down from temporal to lateralized occipital cortex, depending on task demands, under supervisory control of prefrontal cortex. When they reach lateralized occipital cortex, predictions enhance the bottom-up LSF versus HSF representations of the stimulus, all the way from occipital-ventral-parietal to premotor cortex, in turn producing faster categorization behavior. Importantly, content communications are subsets (i.e., 55-75%) of the signal-to-signal communications typically measured between brain regions. Hence, our study isolates functional networks that process the information of cognitive functions.SIGNIFICANCE STATEMENT An enduring cognitive hypothesis states that our perception is partly influenced by the bottom-up sensory input but also by top-down expectations. However, cognitive explanations of the dynamic brain networks mechanisms that flexibly predict and categorize the visual input according to task-demands remain elusive. We addressed them in a predictive experimental design by isolating the network communications of cognitive contents from all other communications. Our methods revealed a Prediction Network that flexibly communicates contents from temporal to lateralized occipital cortex, with explicit frontal control, and an occipital-ventral-parietal-frontal Categorization Network that represents more sharply the predicted contents from the shown stimulus, leading to faster behavior. Our framework and results therefore shed a new light of cognitive information processing on dynamic brain activity.
Assuntos
Mapeamento Encefálico , Imageamento por Ressonância Magnética , Masculino , Feminino , Humanos , Lobo Occipital , Encéfalo , Cognição , Estimulação Luminosa , Percepção VisualRESUMO
Our brain excels at recognizing objects, even when they flash by in a rapid sequence. However, the neural processes determining whether a target image in a rapid sequence can be recognized or not remains elusive. We used electroencephalography (EEG) to investigate the temporal dynamics of brain processes that shape perceptual outcomes in these challenging viewing conditions. Using naturalistic images and advanced multivariate pattern analysis (MVPA) techniques, we probed the brain dynamics governing conscious object recognition. Our results show that although initially similar, the processes for when an object can or cannot be recognized diverge around 180 ms post-appearance, coinciding with feedback neural processes. Decoding analyses indicate that gist perception (partial conscious perception) can occur at â¼120 ms through feedforward mechanisms. In contrast, object identification (full conscious perception of the image) is resolved at â¼190 ms after target onset, suggesting involvement of recurrent processing. These findings underscore the importance of recurrent neural connections in object recognition and awareness in rapid visual presentations.
Assuntos
Estado de Consciência , Eletroencefalografia , Reconhecimento Visual de Modelos , Humanos , Feminino , Masculino , Eletroencefalografia/métodos , Adulto , Estado de Consciência/fisiologia , Adulto Jovem , Reconhecimento Visual de Modelos/fisiologia , Encéfalo/fisiologia , Encéfalo/diagnóstico por imagem , Reconhecimento Psicológico/fisiologia , Estimulação Luminosa/métodosRESUMO
Rare disruptions of the transcription factor FOXP1 are implicated in a human neurodevelopmental disorder characterized by autism and/or intellectual disability with prominent problems in speech and language abilities. Avian orthologues of this transcription factor are evolutionarily conserved and highly expressed in specific regions of songbird brains, including areas associated with vocal production learning and auditory perception. Here, we investigated possible contributions of FoxP1 to song discrimination and auditory perception in juvenile and adult female zebra finches. They received lentiviral knockdowns of FoxP1 in one of two brain areas involved in auditory stimulus processing, HVC (proper name) or CMM (caudomedial mesopallium). Ninety-six females, distributed over different experimental and control groups were trained to discriminate between two stimulus songs in an operant Go/Nogo paradigm and subsequently tested with an array of stimuli. This made it possible to assess how well they recognized and categorized altered versions of training stimuli and whether localized FoxP1 knockdowns affected the role of different features during discrimination and categorization of song. Although FoxP1 expression was significantly reduced by the knockdowns, neither discrimination of the stimulus songs nor categorization of songs modified in pitch, sequential order of syllables or by reversed playback were affected. Subsequently, we analyzed the full dataset to assess the impact of the different stimulus manipulations for cue weighing in song discrimination. Our findings show that zebra finches rely on multiple parameters for song discrimination, but with relatively more prominent roles for spectral parameters and syllable sequencing as cues for song discrimination.NEW & NOTEWORTHY In humans, mutations of the transcription factor FoxP1 are implicated in speech and language problems. In songbirds, FoxP1 has been linked to male song learning and female preference strength. We found that FoxP1 knockdowns in female HVC and caudomedial mesopallium (CMM) did not alter song discrimination or categorization based on spectral and temporal information. However, this large dataset allowed to validate different cue weights for spectral over temporal information for song recognition.
Assuntos
Sinais (Psicologia) , Aprendizagem por Discriminação , Tentilhões , Fatores de Transcrição Forkhead , Técnicas de Silenciamento de Genes , Vocalização Animal , Animais , Tentilhões/fisiologia , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Feminino , Aprendizagem por Discriminação/fisiologia , Vocalização Animal/fisiologia , Percepção Auditiva/fisiologia , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Estimulação AcústicaRESUMO
Categorization is our ability to flexibly assign sensory stimuli into discrete, behaviorally relevant groupings. Categorical decisions can be used to study decision making more generally by dissociating category identity of stimuli from the actions subjects use to signal their decisions. Here we discuss the evidence for such abstract categorical encoding in the primate brain and consider the relationship with other perceptual decision paradigms. Recent work on visual categorization has examined neuronal activity across a hierarchically organized network of cortical areas in monkeys trained to group visual stimuli into arbitrary categories. This has revealed a transformation of visual-feature encoding in early visual cortical areas into more flexible categorical representations in downstream parietal and prefrontal areas. These neuronal category representations are encoded as abstract internal cognitive states because they are not rigidly linked with either specific sensory stimuli or the actions that the monkeys use to signal their categorical choices.
Assuntos
Cognição/fisiologia , Tomada de Decisões/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Comportamento/fisiologia , Humanos , Estimulação Luminosa/métodosRESUMO
Ethnic out-group members are disproportionately more often the victim of misidentifications. The so-called other-race effect (ORE), the tendency to better remember faces of individuals belonging to one's own ethnic in-group than faces belonging to an ethnic out-group, has been identified as one causal ingredient in such tragic incidents. Investigating an important aspect for the ORE-that is, emotional expression-the seminal study by Ackerman and colleagues (2006) found that White participants remembered neutral White faces better than neutral Black faces, but crucially, Black angry faces were better remembered than White angry faces (i.e., a reversed ORE). In the current study, we sought to replicate this study and directly tackle the potential causes for different results with later work. Three hundred ninety-six adult White U.S. citizens completed our study in which we manipulated the kind of employed stimuli (as in the original study vs. more standardized ones) whether participants knew of the recognition task already at the encoding phase. Additionally, participants were asked about the unusualness of the presented faces. We were able to replicate results from the Ackerman et al. (2006) study with the original stimuli but not with more standardized stimuli.
Assuntos
Ira , Rememoração Mental , Adulto , Humanos , Reconhecimento Psicológico , Etnicidade , Expressão FacialRESUMO
Recently, gender-ambiguous (nonbinary) voices have been added to voice assistants to combat gender stereotypes and foster inclusion. However, if people react negatively to such voices, these laudable efforts may be counterproductive. In five preregistered studies (N = 3,684 adult participants) we found that people do react negatively, rating products described by narrators with gender-ambiguous voices less favorably than when they are described by clearly male or female narrators. The voices create a feeling of unease, or social disfluency, that affects evaluations of the products being described. These effects are best explained by low familiarity with voices that sound ambiguous. Thus, initial negative reactions can be overcome with more exposure.
Assuntos
Voz , Humanos , Feminino , Masculino , Adulto , Adulto Jovem , Estereotipagem , Percepção Social , Identidade de Gênero , Adolescente , Pessoa de Meia-IdadeRESUMO
It is commonly assumed that inner speech-the experience of thought as occurring in a natural language-is a human universal. Recent evidence, however, suggests that the experience of inner speech in adults varies from near constant to nonexistent. We propose a name for a lack of the experience of inner speech-anendophasia-and report four studies examining some of its behavioral consequences. We found that adults who reported low levels of inner speech (N = 46) had lower performance on a verbal working memory task and more difficulty performing rhyme judgments compared with adults who reported high levels of inner speech (N = 47). Task-switching performance-previously linked to endogenous verbal cueing-and categorical effects on perceptual judgments were unrelated to differences in inner speech.
Assuntos
Memória de Curto Prazo , Fala , Humanos , Masculino , Feminino , Adulto , Memória de Curto Prazo/fisiologia , Adulto Jovem , Julgamento/fisiologia , Pensamento/fisiologiaRESUMO
In word learning, learners need to identify the referent of words by leveraging the fact that the same word may co-occur with different sets of objects. This raises the question, what do children remember from "in the moment" that they can use for cross-situational learning? Furthermore, do children represent pictures of familiar animals versus drawings of non-existent novel objects as potential referents differently? This study examined these questions by creating learning scenarios with only two potential referents, requiring the least amount of memory to represent all co-present objects. Across three experiments (n > 250) with 4- and 6-year-old children, children reliably selected the intended referent from learning at test, though the learning of novel objects was better than familiar objects. When asked for a co-present object, children of all ages in the study performed at chance in all of the conditions. We discuss the developmental differences in cross-situational word learning capabilities with regard to representing different stimuli as potential referents. Importantly, all children used a propose-but-verify procedure for learning novel words even in the simplest of the learning scenarios given repeated exposure.
Assuntos
Aprendizagem , Aprendizagem Verbal , Criança , Humanos , Pré-Escolar , Probabilidade , Rememoração MentalRESUMO
Two processes describe racially ambiguous Black/White Biracial categorization-the one-drop rule, or hypodescent, whereby racially ambiguous people are categorized as members of their socially subordinated racial group (i.e., Black/White Biracial faces categorized as Black) and the ingroup overexclusion effect, whereby racially ambiguous people are categorized as members of a salient outgroup, regardless of the group's status. Without developmental research with racially diverse samples, it is unclear when these categorization patterns emerge. Study 1 included White, Black, and racially diverse Biracial children (aged 3- to 7-years) and their parents to test how racial group membership and social context influence face categorization biases. To provide the clearest test of hypodescent and ingroup overexclusion, White participants came from majority White neighborhoods and Black participants from majority Black neighborhoods (with Biracial participants from more racially diverse neighborhoods)-two samples with prominent racial ingroups. Study 2 aimed to replicate the parent findings with a separate sample of White, Black, Black/White Biracial, and Asian adults. Results suggest the ingroup overexclusion effect is present across populations early in development and persists into adulthood. Additionally, categorization was meaningfully related to parental context, pinpointing a pathway that potentially contributes to ingroup overexclusion. RESEARCH HIGHLIGHTS: White, Black, and racially diverse Biracial children and adults tended to categorize racially ambiguous Black/White Biracial faces as racial outgroup members, even if the outgroup was White. This contradicts most work arguing Black/White Biracial racially ambiguous people are more often seen as Black. Children and parents' categorizations were related, though children's categorizations were not related to socialization above and beyond parents' categorizations. Children showed similar categorization patterns across dichotomous and continuous measures.
Assuntos
Face , Grupos Raciais , Identificação Social , Inclusão Social , Adulto , Criança , Humanos , População Negra , População Branca , Pré-Escolar , AsiáticoRESUMO
Children tend to categorize novel objects according to their shape rather than their color, texture, or other salient properties-known as "shape bias." We investigated whether this bias also extends to the social domain, where it should lead children to categorize people according to their weight (their body shape) rather than their race (their skin color). In Study 1, participants (n = 50 US 4- and 5-year-olds) were asked to extend a novel label from a target object/person to either an object/person who shared the target's shape/weight, color/race, or neither. Children selected the shape-/weight-matched individual over the color-/race-matched individual (dobjects = 1.58, dpeople = 0.99) and their shape biases were correlated across the two domains. In Study 2, participants (n = 20 US 4- and 5-year-olds) were asked to extend a novel internal property from a target person to either a person who shared the target's weight, race, or neither. Again, children selected the weight-matched individual (d = 1.98), suggesting they view an individual's weight as more predictive of their internal properties than their race. Overall, results suggest that children's early shape bias extends into the social domain. Implications for weight bias and early social cognition are discussed. RESEARCH HIGHLIGHTS: Preschoolers extend novel labels based on people's weight rather than their race. Preschoolers infer internal features based on people's weight rather than their race. Shape biases are present, and correlated, across the social and object domains.
Assuntos
Viés , Peso Corporal , Pré-Escolar , Humanos , Grupos Raciais , SomatotiposRESUMO
To navigate their environment, infants rely on intersensory facilitation when unisensory perceptual demand is high, a principle known as inverse effectiveness. Given that this principle was mainly documented in the context of audiovisual stimulations, here we aim to determine whether it applies to olfactory-to-visual facilitation. We build on previous evidence that the mother's body odor facilitates face categorization in the 4-month-old brain, and investigate whether this effect depends on visual demand. Scalp electroencephalogram (EEG) was recorded in two groups of 4-month-old infants while they watched 6-Hz streams of visual stimuli with faces displayed every 6th stimulus to tag a face-selective response at 1 Hz. We used variable natural stimuli in one group (Nat Group), while stimuli were simplified in the other group (Simp Group) to reduce perceptual categorization demand. During visual stimulation, infants were alternatively exposed to their mother's versus a baseline odor. For both groups, we found an occipito-temporal face-selective response, but with a larger amplitude for the simplified stimuli, reflecting less demanding visual categorization. Importantly, the mother's body odor enhances the response to natural, but not to simplified, face stimuli, indicating that maternal odor improves face categorization when it is most demanding for the 4-month-old brain. Overall, this study demonstrates that the inverse effectiveness of intersensory facilitation applies to the sense of smell during early perceptual development. RESEARCH HIGHLIGHTS: Intersensory facilitation is a function of unisensory perceptual demand in infants (inverse effectiveness). This inverse relation between multisensory and unisensory perception has been mainly documented using audiovisual stimulations. Here we show that olfactory-to-visual facilitation depends on visual demand in 4-month-old infants. The inverse effectiveness of intersensory facilitation during early perceptual development applies to the sense of smell.
RESUMO
The relationship between language and thought is the subject of long-standing debate. One claim states that language facilitates categorization of objects based on a certain feature (e.g. color) through the use of category labels that reduce interference from other, irrelevant features. Therefore, language impairment is expected to affect categorization of items grouped by a single feature (low-dimensional categories, e.g. "Yellow Things") more than categorization of items that share many features (high-dimensional categories, e.g. "Animals"). To test this account, we conducted two behavioral studies with individuals with aphasia and an fMRI experiment with healthy adults. The aphasia studies showed that selective low-dimensional categorization impairment was present in some, but not all, individuals with severe anomia and was not characteristic of aphasia in general. fMRI results revealed little activity in language-responsive brain regions during both low- and high-dimensional categorization; instead, categorization recruited the domain-general multiple-demand network (involved in wide-ranging cognitive tasks). Combined, results demonstrate that the language system is not implicated in object categorization. Instead, selective low-dimensional categorization impairment might be caused by damage to brain regions responsible for cognitive control. Our work adds to the growing evidence of the dissociation between the language system and many cognitive tasks in adults.
Assuntos
Afasia , Idioma , Humanos , Adulto , Encéfalo/diagnóstico por imagem , Afasia/diagnóstico por imagemRESUMO
Real-world scenes consist of objects, defined by local information, and scene background, defined by global information. Although objects and scenes are processed in separate pathways in visual cortex, their processing interacts. Specifically, previous studies have shown that scene context makes blurry objects look sharper, an effect that can be observed as a sharpening of object representations in visual cortex from around 300 ms after stimulus onset. Here, we use MEG to show that objects can also sharpen scene representations, with the same temporal profile. Photographs of indoor (closed) and outdoor (open) scenes were blurred such that they were difficult to categorize on their own but easily disambiguated by the inclusion of an object. Classifiers were trained to distinguish MEG response patterns to intact indoor and outdoor scenes, presented in an independent run, and tested on degraded scenes in the main experiment. Results revealed better decoding of scenes with objects than scenes alone and objects alone from 300 ms after stimulus onset. This effect was strongest over left posterior sensors. These findings show that the influence of objects on scene representations occurs at similar latencies as the influence of scenes on object representations, in line with a common predictive processing mechanism.