Cognition

Connectome stability and typicality as markers of cognitive performance

Although sustained attention and working memory are essential to daily life, individual abilities vary. Whole-brain fMRI functional connectivity is a useful tool for building brain-based markers of cognition and has been used to identify network models of sustained attention (Rosenberg et al., 2016) and working memory (Avery et al., 2020). Further, there is evidence that features of whole-brain functional connectivity patterns, or connectomes, are related to brain function (Kaufmann et al., 2017; Vanderwal et al., 2021). Here, we define three connectome features—stability, typicality, and discriminability—that characterize connectome similarity with oneself and within a group. We then test the extent to which these features predict sustained attention and working memory task performance in three independent datasets (total N=421). Results suggest that individuals with more stable (i.e., similar to oneself across fMRI runs) and typical (i.e., similar to the group-average) connectomes perform better on these tasks. These results demonstrate the utility of including whole-brain connectome features in developing predictive models of cognitive abilities such as sustained attention and working memory.

What is the bandwidth of perceptual experience? Evidence from virtual reality

How much information are we aware of in the visual world? While this question appears rather simple, answering it has been remarkably difficult and extremely controversial. Traditionally, researchers examine the limits of perceptual experience by changing individual items in a scene and seeing how often observers notice those changes (e.g., failing to notice a bowl disappearing/changing). Here, we took a different approach and asked how much we could alter an entire scene before observers noticed those global alterations. Specifically, we used a combination of standard psychophysics (i.e., computer displays) and gaze-contingent virtual reality (i.e., VR) to alter the scenes in one of two ways: 1) desaturating the periphery to render it entirely in black and white or 2) scrambling the periphery so much that no object could be detected or identified. Surprisingly, we found that observers routinely failed to notice drastic changes to that scene (e.g., presenting only 5% of the world in color while the rest was black and white, completely scrambling the periphery of a scene, etc.). Together, these results suggest that perceptual experience may be remarkably impoverished and that our intuitive sense of a detailed, colorful world is surprisingly incorrect.

How we know what not to think

Violence Exposure and Adolescents’ Autonomic Regulation

Interpersonal violence exposure is associated with adolescent maladjustment across the domains of mental health (e.g., traumatic stress), interpersonal functioning (e.g., conflictual relationships, dating violence, sexual risk behavior), and health risk behaviors (e.g., substance use, sexual risk). Substantial variability in the responses of adolescents presents a need to identify mechanisms that explain how and why interpersonal violence exposure leads to adjustment problems. Violence exposure is believed to alter autonomic nervous system (ANS) regulation in ways that contribute to functional impairments in cognition, emotion, and behavior. Alterations in ANS development following violence exposure may prime adolescents to perceive the social environment as threatening and promote maladaptive patterns of threat-related responses to non-violent stressors. Preliminary data from a short-term longitudinal study of adolescent girls with a history of interpersonal violence (IPV) exposure demonstrates that measures of autonomic cardiac control are related to violence exposure. I will also describe how utilizing a virtual reality paradigm can provide an ecologically valid framework for studying individual differences in adolescents’ stress regulation and associations with violence-related sequelae.

How hippocampal memory shapes, and is shaped by, attention

Attention modulates what we see and remember. Memory affects what we attend to and perceive. Despite this connection in behavior, little is known about the mechanisms that link attention and memory in the brain. One key structure that may be at the interface between attention and memory is the hippocampus. Here, I’ll explore the hypothesis that the relational representations of the hippocampus allow it to critically contribute to bidirectional interactions between attention and memory. First, I’ll show — in a series of human fMRI studies — that attention creates state-dependent patterns of activity in the hippocampus, and that these representations predict both online attentional behavior and memory formation. Then, I’ll provide neuropsychological evidence that hippocampal damage impairs performance on attention tasks that tax relational representations, particularly spatial relational representations. Furthermore, cholinergic modulation (from nicotine) may play a role enhancing this form of hippocampal attention and perception. Finally, I’ll demonstrate that hippocampal memories enable preparation for upcoming attentional states, particularly when those attentional states are guided by memory. Together, this line of work highlights the tight links between attention and memory – links that are established, at least in part, by the hippocampus.

Long-range respiratory and theta oscillation networks depend on spatial sensory context

Recent studies have shown widespread interactions between the nasally driven respiratory rhythm and neural oscillations in hippocampus and neocortex. With this study, we address how the respiratory rhythm interacts with ongoing slow brain rhythms across olfactory, hippocampal and visual systems in freely moving rats. Patterns of network connectivity change with behavioral state, with stronger interactions at fast and slow respiratory frequencies during foraging as compared to home cage activity. Routing of interactions between sensory cortices depends on the modality of spatial cues present during foraging. Functional connectivity analyses suggest strong bidirectional interactions between olfactory and hippocampal systems related to respiration and point to the piriform cortex as a key area for mediating respiratory and theta rhythms.

How memory meets perception during naturalistic scene understanding

As we navigate our visual world, what we see is seamlessly integrated with our memory of the broader environment. One long-standing puzzle in neuroscience is how perceptual and mnemonic systems – which are topographically distinct in the brain – interface to give rise to memory-guided visual experience. In this talk, I will present a series of studies using head-mounted virtual reality and fMRI to explore this question. First, we investigated the neural basis of scene perception and memory using fine-grained individual-subject fMRI. To our surprise, this analysis revealed a new network of brain areas that collectively bridge the scene perception and spatial memory systems of the human brain, the “place memory network” (Steel et al., Nat Coms, In Press). Specifically, we reveal three areas, each lying immediately anterior to a region of the scene perception network in posterior cerebral cortex, that selectively activate when recalling familiar real-world locations. Despite their close proximity to the scene-perception areas, network analyses show that these regions constitute a distinct functional network that interfaces with memory systems during naturalistic scene understanding. We hypothesize that these regions may provide remembered, contextual representations to support ongoing perception. In a second study, we use head-mounted virtual reality (VR) and behavior to test whether memory for a broad spatial environment, in fact, impacts ongoing scene perception in behavior. Using a priming paradigm, we show that a briefly presented scene view reinstates associated views of the panoramic environment, facilitating subsequent perception. Together, these studies illuminate how perceptual and mnemonic systems interact during naturalistic visual experience, and point to a new mechanistic step for understanding how the brain implements memory-guided visual behaviors in posterior cerebral cortex.

Do Hering’s sensations determine lexical color categories?

In principle, languages could create lexical color categories that partition color space in culture-specific ways. Nonetheless, the color categories in the lexicons of world languages are strikingly similar. Why is this so? One traditional explanation is based on Hering’s elemental sensations (redness, greenness, blueness and yellowness), which demarcate privileged regions of color space. Several recent studies have challenged the special status of Hering’s sensations. Are they the cause or the by-product of “red”, “green”, “blue” and “yellow” color categories of the Indo-European languages? Here, we describe the results of three studies that address this issue. The first two studies examined the understanding of Hering’s elemental sensations in subjects speaking languages that are missing terms for some of these sensations. Color naming by the Hadza people is sparse and distributed: most speakers do not use terms for all the Hering sensations (or most other basic color categories of IndoEuropean languages), yet each person uses a different subset of the terms. Thus, the language as a whole demonstrates a complete Hering lexicon, though no idiolect does so. Somali-speaking observers use a term “grue” that does not respect the color boundaries of the Hering color terms, and particularly their term for “yellow” often names colors of every hue. A third study examined the elemental sensations in English-speaking deuteranomalous trichromats. Their initial physiological encoding of color differed from that of color-normal observers. Nevertheless, their choices of broadband lights corresponding to the unique and binary hues of Hering’s theory were similar, but not identical, to those of color normal observers. These results highlight the importance of language in mediating color understanding but are inconsistent with the view that culture alone guides color category formation.