Journal of Cognitive Neuroscience最新文献

Whether small number magnitudes are inherently represented as lying to the left of larger ones, the space-number association (SNA), is an important issue in mathematical cognition. In this fMRI study, we used a go/no-go implicit association task to investigate the brain activity and functional connectivity underlying the SNA. Arabic digits lower or higher than 5 and left- or right-pointing arrows were alternated as central targets. In a single-code task condition, participants responded to a specific number magnitude and to all arrows or to a specific arrow direction and to all number magnitudes. In a joint-code (JC) condition, responses were provided after congruent, for example, "go when a number is lower than 5 or an arrow points left," or incongruent, for example, "go when a number is lower than 5 or an arrow points right," SNAs. The SNA was only found in the JC condition, where responses were faster with congruent instructions. Analyses of fMRI functional connectivity showed that the SNA was matched with enhanced excitatory inputs from ACC, the left TPJ, and the left inferior frontal gyrus to the left and right intraparietal sulcus (IPS). Incongruent JC trials were associated with enhanced excitatory modulation from ACC to the left and right IPS. These results show that the SNA is associated with enhanced activation of top-down brain control and changes in the functional interaction between the left and right IPS. We conclude that the SNA does not depend on an inherent and bottom-up spatial coding of number magnitudes.

Crossing a spatial boundary such as a doorway plays an important role in the temporal organization of episodic memory. However, despite the wealth of evidence showing that visual boundary structures in scenes affect our representation of space, no studies have tested the possibility that they also function as event boundaries even without active navigation. In this study, we used a nonnavigational scene-based memory task that required participants to remember a sequence of objects moving to various baskets in a scene. In the boundary condition, there was a freestanding boundary in the middle of the room, low enough to see the rest of the room beyond it. We found that the additional boundary within the scene was sufficient to trigger a larger response in the cortical visual scene network, the hippocampus, and their coordinated activity. These results suggest that active navigation across a spatial boundary such as a doorway into another room is not necessary to form an event boundary and that a visual representation of boundaries is sufficient to influence the organization of a hippocampal episodic memory.

Ungerleider and Mishkin, in their influential work that relied on detailed anatomical and ablation studies, suggested that visual information is processed along two distinct pathways: the dorsal "where" pathway, primarily responsible for spatial vision, and the ventral "what" pathway, dedicated to object vision. This strict division of labor has faced challenges in light of compelling evidence revealing robust shape and object selectivity within the putative "where" pathway. This article reviews evidence that supports the presence of shape selectivity in the dorsal pathway. A comparative examination of dorsal and ventral object representations in terms of invariance, task dependency, and representational content reveals similarities and differences between the two pathways. Both exhibit some level of tolerance to image transformations and are influenced by tasks, but responses in the dorsal pathway show weaker tolerance and stronger task modulations than those in the ventral pathway. Furthermore, an examination of their representational content highlights a divergence between the responses in the two pathways, suggesting that they are sensitive to distinct features of objects. Collectively, these findings suggest that two networks exist in the human brain for processing object shapes, one in the dorsal and another in the ventral visual cortex. These studies lay the foundation for future research aimed at revealing the precise roles the two "what" networks play in our ability to understand and interact with objects.

Early childhood is a critical period for episodic memory development, with sharp behavioral improvements between ages 4 to 7 years. Prior work has demonstrated this extensively with prompted memory tasks, but we explored performance on unprompted, free recall of a naturalistic experience in children, and how their performance relates to other cognitive measures. We asked children and adults to view a television episode, a naturalistic task for which there exists a ground truth, and assessed their free recall memory for the episode. Children's free recall performance improved dramatically with age, with many young children producing no verbal free recall whatsoever, although prompted recognition memory measures showed retention of material. However, the detail in free recall was related to both recognition and temporal order forced-choice memory performance in our full sample, showing agreement among memory measures. Free recall was strongly predicted by verbal skills, suggesting that children's sparse recall reflects verbal skill development rather than a pure mnemonic deficit. We propose that free recall has a more protracted developmental trajectory because it requires more substantial verbal skills as well as metacognitive skills that direct memory search, as compared with forced-choice memory tasks.