Differential prefrontal–temporal neural correlates of semantic processing in children

This study used functional magnetic resonance imaging (fMRI) to examine brain–behavior correlations in a group of 16 children (9- to 12-year-olds). Activation was measured during a semantic judgment task presented in either the visual or auditory modality that required the individual to determine whether a final word was related in meaning to one of two previous words (e.g., found–tank–lost). The main finding was that higher performers (i.e., accuracy) were associated with more activation in posterior representational systems including the inferior and middle temporal gyri, whereas lower performers were associated with more activation in anterior regions including the inferior and middle frontal gyri. This pattern of results was interpreted as reflecting an elaborated semantic representational system in temporal areas for the high accuracy performers that allowed them to efficiently and accurately make meaning based judgments. The low accuracy performers may have an inaccurate or weakly interconnected semantic system that results in greater use of frontal areas in a feature selection process.     

Different patterns of recollection impairment in confabulation reveal different disorders of consciousness: A multiple case study

Recollection is used to refer to the active process of setting up retrieval cues, evaluating the outcome, and systematically working toward a representation of a past experience that we find acceptable.In this study we report on three patients showing different patterns of confabulation affecting recollection and consciousness differentially. All patients confabulated in the episodic past domain. However, whereas in one patient confabulation affected only recollection of events concerning his personal past, present and future, in another patient confabulation also affected recollection of impersonal knowledge. The third patient showed an intermediate pattern of confabulation, which affected selectively the retrieval of past information, both personal and impersonal. We suggest that our results are in favor of a fractionation of processes involved in recollection underling different disorders of consciousness.     

Neural correlates of comprehension and production of nouns and verbs in Chinese

This paper reports a conjunction analysis between semantic relatedness judgment and semantic associate generation of Chinese nouns and verbs with concrete or abstract meanings. The results revealed a verb-specific task-independent region in LpSTG&MTG, and task-dependent activation in a left frontal region in semantic judgment and the left SMG in semantic associate production. The observation of word class effects converged on Yu, Law, Han, Zhu, and Bi (2011), but contrasted with null findings in previous reports using a lexical decision task. While word class effects in the left posterior temporal cortices have been described in previous studies of languages with rich inflectional morphology, the significance of this study lies in its demonstration of the effects in these regions in a language known to have little inflectional morphology. In other words, differential neural responses to nouns and verbs can be observed without confounding from morphosyntactic operations or contrasts between actions and objects.     

Redundancy gain in semantic categorisation

Redundancy gain refers to the performance enhancements often associated with the presentation of redundant versus single targets (for example, faster, more accurate, or more forceful responses). Though predominantly observed in relatively simple tasks (e.g., stimulus detection), there have been some efforts to investigate similar phenomena in tasks involving higher level processing. We conducted three experiments aimed at determining (a) whether a redundancy gain would be evident in a task unambiguously requiring higher level processing (the semantic categorisation of visually-presented lexical stimuli), and (b) if so, what accounts might be appropriate to explain such findings. We found that redundancy gains are observed in such tasks, and we conclude that both coactivation and race models can account for these gains.     

Effects of Emotional Experience for Abstract Words in the Stroop Task

In this study, we examined the effects of emotional experience, a relatively new dimension of emotional knowledge that gauges the ease with which words evoke emotional experience, on abstract word processing in the Stroop task. In order to test the context‐dependency of these effects, we accentuated the saliency of this dimension in Experiment 1A by blocking the stimuli such that one block consisted of the stimuli with the highest emotional experience ratings and the other block consisted of the stimuli with the lowest emotional experience ratings. We attenuated the saliency of this dimension in Experiment 1B by intermixing the stimuli. We observed slower color naming performance for words with higher emotional experience ratings only in Experiment 1A, suggesting that the dimension of emotional experience is an aspect of semantic representation for abstract words but that its influence can be modulated by context. We interpret these results more generally using Vigliocco, Meteyard, Andrews, and Kousta's (2009) framework of semantic representation, and more specifically using Cohen, Dunbar, and McClelland's (1990) model of Stroop task performance.     

Age invariance in semantic and episodic metamemory: Both younger and older adults provide accurate feeling-of-knowing for names of faces

Age differences in feeling-of-knowing (FOK) accuracy were examined for both episodic memory and semantic memory. Younger and older adults either viewed pictures of famous faces (semantic memory) or associated non-famous faces and names (episodic memory) and were tested on their memory for the name of the presented face. Participants viewed the faces again and made a FOK prediction about future recognition of the name associated with the presented face. Finally, four-alternative forced-choice recognition memory for the name, cued by the face, was tested and confidence judgments (CJs) were collected for each recognition response. Age differences were not obtained in semantic memory or the resolution of semantic FOKs, defined by within-person correlations of FOKs with recognition memory performance. Although age differences were obtained in level of episodic memory, there were no age differences in the resolution of episodic FOKs. FOKs for correctly recognized items correlated reliably with CJs for both types of materials, and did not differ by age group. The results indicate age invariance in monitoring of retrieval processes for name–face associations.     

Increasing Levels of Semantic Verbal Fluency in Elderly English Adults

ABSTRACT

Analyses incorporating large independent population-based samples and identical measures are needed to investigate recent trends in cognitive function. Nationally representative independent cohorts of community living individuals in England aged 65 years or older from the MRC Cognitive Function and Ageing Study in 1991 (n = 9458) and the English Longitudinal Study of Ageing in 2002 (n = 5196) were compared. East Cambridgeshire participants aged 65–69 years in 1991 (n = 680) were also compared to an independent cohort examined in 1996 (n = 600). Semantic verbal fluency, as measured by the animal naming neuropsychological test, increased by 1.1 extra words a minute in England between 1991 and 2002 (95% CI 0.9, 1.3). A similar increase was also observed in East Cambridgeshire. Levels of semantic verbal fluency appear to have increased in the older English population, which may help to buffer the aging population from future increases in dementia.     

The time course of access to semantic information in high-performing older adults: Behavioral evidence for the hemispheric asymmetry reduction in OLDer individuals

ABSTRACT

The possibility that the HAROLD phenomenon (i.e., Hemispheric Asymmetry Reduction in OLDer adults) is manifested in the course of access to semantic information, in particular the meaning of emotional words, was investigated using the visual half-field priming paradigm. The time course of priming was tracked in the cerebral hemispheres across three SOAs: 150, 300, and 750 ms. The results showed older and young adults had the same level of accuracy. While priming occurred unilaterally in young participants, the pattern of priming in older participants appeared to be bilateral whenever it was present, that is, at the 300- and 750-ms SOAs. The delay in the appearance of priming in older adults may be due to an increase in sensory thresholds that causes older adults to need more time to encode stimuli and fully activate their semantic network. It is concluded that the bilateral pattern of priming in the presence of an equivalent level of performance in older adults provides behavioral evidence supporting the compensatory role of the HAROLD phenomenon for this particular task.     

Discriminating Semantic from Episodic Relatedness in Young and Older Adults

ABSTRACT

The ability of young (aged 18–30) and older (aged 60–80) adults to discriminate pre-experimental (semantic) from experimental (episodic) associations was examined. Participants studied a list containing semantically related and unrelated word pairs and then made either associative recognition (Experiments 1a and b) or semantic relatedness (Experiment 2) judgments at various response deadlines. For associative recognition judgments, both young and older adults benefited from semantic relatedness, leading to more hits for related than unrelated pairs, and at the long response deadline, older adults' performance on those pairs matched that of young participants. Also, both young and older adults demonstrated superior discrimination for unrelated lures whose members had originally been studied in related pairs – evidence for recall-to-reject processing in both age groups. In making semantic relatedness judgments, both young and older adults showed an episodic priming effect. When older adults can rely on long-standing associations, their performance resembles that of young adults – both in associative recognition and in episodic priming.