The role of vision in the neural representation of unique entities

Impaired lexical access for unique entities in individuals with subjective cognitive decline

Subjective cognitive decline (SCD) may serve as an early indicator of Alzheimer's disease (AD). However, accurately quantifying cognitive impairment in SCD is challenging, mainly because existing assessment tools lack sensitivity. This study examined how tasks specifically designed to assess knowledge of famous people, could potentially aid in identifying cognitive impairment in SCD. A total of 60 adults with SCD and 60 healthy controls (HCs) aged 50 to 82 years performed a famous people verbal fluency task and a famous people naming task. In the famous people fluency task, the results showed that the individuals with SCD produced significantly fewer famous names in the total time allowed than the HCs, and this difference was also found in the first and the second time interval. In the famous people naming task, the performance of the SCD group was significantly lower than that of the HC group only in the more recent period of fame. Overall, these results suggest that retrieving the names of famous people was more difficult for people with SCD than for people without cognitive complaints. They also suggest that famous people verbal fluency and naming tasks could be useful in detecting cognitive decline at the preclinical stage of AD.

Developing cortex is functionally pluripotent: Evidence from blindness

How rigidly does innate architecture constrain function of developing cortex? What is the contribution of early experience? We review insights into these questions from visual cortex function in people born blind. In blindness, occipital cortices are active during auditory and tactile tasks. What 'cross-modal' plasticity tells us about cortical flexibility is debated. On the one hand, visual networks of blind people respond to higher cognitive information, such as sentence grammar, suggesting drastic repurposing. On the other, in line with 'metamodal' accounts, sighted and blind populations show shared domain preferences in ventral occipito-temporal cortex (vOTC), suggesting visual areas switch input modality but perform the same or similar perceptual functions (e.g., face recognition) in blindness. Here we bring these disparate literatures together, reviewing and synthesizing evidence that speaks to whether visual cortices have similar or different functions in blind and sighted people. Together, the evidence suggests that in blindness, visual cortices are incorporated into higher-cognitive (e.g., fronto-parietal) networks, which are a major source long-range input to the visual system. We propose the connectivity-constrained experience-dependent account. Functional development is constrained by innate anatomical connectivity, experience and behavioral needs. Infant cortex is pluripotent, the same anatomical constraints develop into different functional outcomes.

Similar representation of names and faces in the network for person perception

Person-knowledge encompasses the diverse types of knowledge we have about other people. This knowledge spans the social, physical, episodic, semantic & nominal information we possess about others and is served by a distributed cortical network including core (perceptual) and extended (non-perceptual) subsystems. Our understanding of this cortical system is tightly linked to the perception of faces and the extent to which cortical knowledge-access processes are independent of perception is unclear. In this study, participants were presented with the written names of famous people and performed ten different semantic access tasks drawn from five cognitive domains (biographic, episodic, nominal, social and physical). We used representational similarity analysis, adapted to investigate network-level representations (NetRSA) to characterise the inter-regional functional coordination within the non-perceptual extended subsystem across access to varied forms of person-knowledge. Results indicate a hierarchical cognitive taxonomy consistent with that seen during face-processing and forming the same three macro-domains: socio-perceptual judgements, episodic-semantic memory and nominal knowledge. The coordination across regions was largely preserved within elements of the extended system associated with internalised cognition but differed in prefrontal regions. Results suggest the elements of the extended system work together in a consistent way to access knowledge when viewing faces and names but that coordination patterns also change as a function of input-processing demands.

Norms for pictures of proper names: contrasting famous people and well-known places in younger and older adults

Proper names comprise a class of labels that arbitrarily nominate specific entities, such as people and places. Compared to common nouns, retrieving proper names is more challenging. Thus, they constitute good alternative semantic categories for psycholinguistic and neurocognitive research and intervention. The ability to retrieve proper names is known to decrease with aging. Likewise, their retrieval may differ across their different categories (e.g., people and places) given their specific associated knowledge. Therefore, proper names' stimuli require careful selection due to their high dependence on prior experiences. Notably, normative datasets for pictures of proper names are scarce and hardly have considered the influence of aging and categories. The current study established culturally adapted norms for proper names' pictures (N = 80) from an adult sample (N = 107), in psycholinguistic measures (naming and categorization scores) and evaluative dimensions (fame, familiarity, distinctiveness, arousal, and representational quality). These norms were contrasted across different categories (famous people and well-known places) and age groups (younger and older adults). Additionally, the correlations between all variables were examined. Proper names' pictures were named and categorized above chance and overall rated as familiar, famous, distinctive, and of high representational quality. Age effects were observed across all variables, except familiarity. Category effects were occasionally observed. Finally, the correlations between the psycholinguistic measures and all rated dimensions suggest the relevance of controlling for these dimensions when assessing naming abilities. The current norms provide a relevant aging-adapted dataset that is publicly available for research and intervention purposes.

fMRI-Indexed neural temporal tuning reveals the hierarchical organsiation of the face and person selective network

Recognising and knowing about conspecifics is vital to human interaction and is served in the brain by a well-characterised cortical network. Understanding the temporal dynamics of this network is critical to gaining insight into both hierarchical organisation and regional coordination. Here, we combine the high spatial resolution of fMRI with a paradigm that permits investigation of differential temporal tuning across cortical regions. We cognitively under- and overload the system using the rapid presentation (100-1200msec) of famous faces and buildings. We observed an increase in activity as presentation rates slowed and a negative deflection when inter-stimulus intervals (ISIs) were extended to longer periods. The primary distinction in tuning patterns was between core (perceptual) and extended (non-perceptual) systems but there was also evidence for nested hierarchies within systems, as well as indications of widespread parallel processing. Extended regions demonstrated common temporal tuning across regions which may indicate coordinated activity as they cooperate to manifest the diverse cognitive representation accomplished by this network. With the support of an additional psychophysical study, we demonstrated that ISIs necessary for different levels of semantic access are consistent with temporal tuning patterns. Collectively, these results show that regions of the person-knowledge network operate over different temporal timescales consistent with hierarchical organisation.

Intrinsic connectivity of anterior temporal lobe relates to individual differences in semantic retrieval for landmarks

Contemporary neuroscientific accounts suggest that ventral anterior temporal lobe (ATL) acts as a bilateral heteromodal semantic hub, which is particularly critical for the specific-level knowledge needed to recognise unique entities, such as familiar landmarks and faces. There may also be graded functional differences between left and right ATL, relating to effects of modality (linguistic versus non-linguistic) and category (e.g., knowledge of people and places). Individual differences in intrinsic connectivity from left and right ATL might be associated with variation in semantic categorisation performance across these categories and modalities. We recorded resting-state fMRI in 74 individuals and, in a separate session, examined semantic categorisation. People with greater connectivity between left and right ATL were more efficient at categorising landmarks (e.g., Eiffel Tower), especially when these were presented visually. In addition, participants who showed stronger connectivity from right than left ATL to medial occipital cortex showed more efficient semantic categorisation of landmarks regardless of modality of presentation. These results can be interpreted in terms of graded differences in the patterns of connectivity across left and right ATL, which give rise to a bilateral yet partially segregated semantic 'hub'. More specifically, right ATL connectivity supports the efficient semantic categorisation of landmarks.

Close yet independent: Dissociation of social from valence and abstract semantic dimensions in the left anterior temporal lobe

The anterior temporal lobe (ATL) is engaged in various types of semantic dimensions. One consistently reported dimension is social information, with abstract words describing social behaviors inducing stronger activations in the ATL than nonsocial words. One potential factor that has been systematically confounded in this finding is emotional valence, given that abstract social words tend to be associated with emotional feelings. We investigated which factors drove the ATL sensitivity using a 2 (social/nonsocial) × 2 (valenced/neutral) factorial design in an fMRI study with relatively high spatial resolutions. We found that sociality and valence were processed in different ATL regions without significant interactions: The social effect was found in the left anterior superior temporal sulcus (aSTS), whereas the valence effect activated small clusters in the bilateral temporal poles (TP). In the left ATL, the social- and valence-related clusters were distinct from another superior ATL area that exhibited a general "abstractness" effect with little modulation of sociality or valence. These subregions exhibited distinct whole-brain functional connectivity patterns during the resting state, with the social cluster functionally connected to the default mode network, the valence cluster connected to the adjacent temporal regions and amygdala, and the abstractness cluster connected to a distributed network including a set of language-related regions. These results of activation profiles and connectivity patterns together indicate that the way in which the left ATL supports semantic processing is highly fine-grained, with the neural substrate for social semantic effects dissociated from those for emotional valence and abstractness.

A Tri-network Model of Human Semantic Processing

Humans process the meaning of the world via both verbal and nonverbal modalities. It has been established that widely distributed cortical regions are involved in semantic processing, yet the global wiring pattern of this brain system has not been considered in the current neurocognitive semantic models. We review evidence from the brain-network perspective, which shows that the semantic system is topologically segregated into three brain modules. Revisiting previous region-based evidence in light of these new network findings, we postulate that these three modules support multimodal experiential representation, language-supported representation, and semantic control. A tri-network neurocognitive model of semantic processing is proposed, which generates new hypotheses regarding the network basis of different types of semantic processes.

Modality-independent encoding of individual concepts in the left parietal cortex

The organization of semantic information in the brain has been mainly explored through category-based models, on the assumption that categories broadly reflect the organization of conceptual knowledge. However, the analysis of concepts as individual entities, rather than as items belonging to distinct superordinate categories, may represent a significant advancement in the comprehension of how conceptual knowledge is encoded in the human brain. Here, we studied the individual representation of thirty concrete nouns from six different categories, across different sensory modalities (i.e., auditory and visual) and groups (i.e., sighted and congenitally blind individuals) in a core hub of the semantic network, the left angular gyrus, and in its neighboring regions within the lateral parietal cortex. Four models based on either perceptual or semantic features at different levels of complexity (i.e., low- or high-level) were used to predict fMRI brain activity using representational similarity encoding analysis. When controlling for the superordinate component, high-level models based on semantic and shape information led to significant encoding accuracies in the intraparietal sulcus only. This region is involved in feature binding and combination of concepts across multiple sensory modalities, suggesting its role in high-level representation of conceptual knowledge. Moreover, when the information regarding superordinate categories is retained, a large extent of parietal cortex is engaged. This result indicates the need to control for the coarse-level categorial organization when performing studies on higher-level processes related to the retrieval of semantic information.