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
Humans have an unrivaled ability to represent and reason about unrealized possible actions – the vast infinity of things that were not (or have not yet been) chosen. This capacity is central to the most impressive of our capacities: causal reasoning, planning, linguistic communication, moral judgment, etc. Nevertheless, not a great deal is known about how we select possible actions that are worth considering from the infinity of unrealized actions that are better left ignored. I’ll review research across the cognitive sciences, and argue that the possible actions considered by default are those that are both likely to occur and generally valuable. I’ll then point to a unified theory of why, proposing that (i) across diverse cognitive tasks, the possible actions we consider are biased towards those of general practical utility, and (ii) a plausible primary function for this mechanism resides in decision making. I’ll end by presenting new empirical evidence for such a mechanism in decision making.
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.
Competing Motivational Processes: Autonomic Correlates and Behavioral Output
An organism’s willingness to expend energy is highly malleable and responsive to both internal and environmental perturbations. Motivation promotes physiological and behavioral prioritization driven by current needs. Goals associated with motivational states support processes that benefit daily life as well as long-term survival. Organisms are motivated by an expansive set of needs, ranging from balancing low-level metabolic processes to higher-order maintenance of social systems. Often as one motivation increases, organisms will de-prioritize other motivational processes and shift resources towards behavioral and physiological processes associated with current needs. With a focus on hunger, fatigue, and loneliness I will discuss how autonomic physiology can inform our understanding of how organisms prioritize behavior and survive in ever-changing environments.
A Task-Induced Functional Gradient of Adolescent Psychopathology
Scale-free brain activity occurs when a neural time-series has a high degree of self-similarity in the temporal domain, resulting in more smooth-looking fluctuations. Recent findings from human neuroimaging studies suggest that measures of scale-free brain activity can indicate the “health” of complex neural networks. Among these findings is evidence that less scale-free signals are associated with harder tasks, more novel tasks, poorer performance, increased age, and greater symptoms across a broad range of psychopathologies.
We build on this work and examine covariance between psychopathology and patterns of fMRI-based scale-free brain activity in 1,839 adolescents (9-10 years old) during a working memory task. In this study we use the Hurst exponent to measure the degree to which an individual fMRI BOLD time-series is scale-free. We find a hurst-psychopathology gradient which associates less scale-free brains with higher levels of psychopathology and worse working memory performance. This is in line with the expectations of previous research on hurst and psychopathology. We additionally ask how similar the spatial distribution of this gradient map is to spatial patterns of activations associated with psychological and cognitive terms. We find that the hurst-psychopathology gradient is positively correlated to terms related to task-specific cognition and negatively correlated to terms related to cue-response. This suggests that individuals with higher levels of psychopathology “look” like they are engaged more in task specific processing despite having worse performance. In contrast individuals with lower levels of psychopathology “look” like they are less engaged in task-specific processing despite having better performance.
Seeing Fruit on trees: the role of normalization in dynamic feature-linking
Vision, and other senses, must reconstruct a model of the outside world in a way that allows for action. Our nervous system must extrapolate from incomplete and ambiguous information to do so, as in the case of the transformation of the two retinas’ two-dimensional neural representation into a unified model of an ever-changing three-dimensional world.
The capacity for flexible perception is supported by sensory adaptation and attention, which culminate in a bias toward one possible percept over another. Implicit perceptual biases support an advantage for useful percepts from the inherently ambiguous retinal representations. Perceptual grouping is one well-characterized visual outcome that exemplifies biased perception by enhancing perceptual similarity. Until recently, grouped percepts have dominated accounts of ambiguity resolution, leaving other possible biases to be explored.
One published report supports the position that 1) A difference-enhancing bias exists to produce percepts of objects in view that are maximally different; and 2) A normalization account of perceptual grouping may explain dynamical feature-linking. Finally, four experiments are proposed to address A) how the visual system may use normalization to dynamically selects perceptual experience, B) To what extent does normalization acts globally, or locally, C) what is the influence of magnocellular and parvocellular antagonism in resolving ambiguous figures and ground, and D) can attention influence the resolution of ambiguity? Taken together, these data will provide insight into the neural computation the visual system performs on ambiguous representations to produce separable perceptual outcomes under different input statistics.
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.