Both a Gauge and a Filter: Cognitive Modulations of Pupil Size

Over 50 years of research have established that cognitive processes influence pupil size. This has led to the widespread use of pupil size as a peripheral measure of cortical processing in psychology and neuroscience. However, the function of cortical control over the pupil remains poorly understood. Why does visual attention change the pupil light reflex? Why do mental effort and surprise cause pupil dilation? Here, we consider these functional questions as we review and synthesize two literatures on cognitive effects on the pupil: how cognition affects pupil light response and how cognition affects pupil size under constant luminance. We propose that cognition may have co-opted control of the pupil in order to filter incoming visual information to optimize it for particular goals. This could complement other cortical mechanisms through which cognition shapes visual perception

Explorations, Vol. 3, No. 2

Cover: Edmund G. Schildknecht, Seated Figure, 1929, oil on canvas, 30” x 25”, acc. no. 85.6.31, bequest of Edmund G. Schildknecht Articles include: Reyes Syndrome Under Attack at UMaine, by MaryAnn Jerkofsky Maine Service Abroad: Using Labor Market Results for Planning Education and Training in Developing Countries, by David H. Clark Feeling and Form: Four American Paintings in the University of Maine Art Collection, by David Ebitz We Stand Corrected, Volume 3, Number 1, of EXPLORATIONS Confessions of a Comet Huckster, by Alan Davenport H.G. Wells: Socialist, Feminist, Polymath, Educator and Hero, by David C. Smith Supercritical Fluids and Their Interaction with Lignocellulosic Materials and Polymers, by Erdogan Kira

Explorations, Vol. 1, No. 1

Welcome to the first issue of Explorations, A Journal of Research at the University of Maine at Orono. Join us as we explore a representative selection of the pure and applied research of our faculty. At UMO, we believe that research can capture the imagination and invigorate the mind, as well as contribute directly to the quality of life of the citizens we serve. In this first issue, we have selected four areas of research that span the disciplines of biological and environmental sciences and the arts. This is but a small part of the research conducted by the faculty at UMO where research, teaching and public service activities support baccalaureate degree study in more than 85 fields and graduate study at the master’s and doctoral levels in more than 50 fields. Articles include: The DNA Molecule: Mapping its Mysteries, by R.D. Blake. The double helix is a thing of habit: simple computer programs are providing molecular biologists with portraits of the evolution of organisms and species. The Larch: Avoiding a critical shortage, by Katherine Carter. The curtain is rising on a stage set by a spruce budworm epidemic 70 years ago; clones from exotic larches may halt an economic tragedy. The Medieval Oliphant: Its Function and Meaning in Romanesque Secular Art, by David MacKinnon Ebitz. Rarely mentioned in art histories, elephant tusk sculpture added stateliness and grace to noble courts of the Middle Ages. RADON: noble gas? by Carole J. Bombard assisted by Stephen A. Norton. With epidemiological research in Maine, the United States becomes one of only three countries conducting studies to find the causal relationship between radon and cancer

Semi-orthogonal subspaces for value mediate a tradeoff between binding and generalization

When choosing between options, we must associate their values with the action needed to select them. We hypothesize that the brain solves this binding problem through neural population subspaces. To test this hypothesis, we examined neuronal responses in five reward-sensitive regions in macaques performing a risky choice task with sequential offers. Surprisingly, in all areas, the neural population encoded the values of offers presented on the left and right in distinct subspaces. We show that the encoding we observe is sufficient to bind the values of the offers to their respective positions in space while preserving abstract value information, which may be important for rapid learning and generalization to novel contexts. Moreover, after both offers have been presented, all areas encode the value of the first and second offers in orthogonal subspaces. In this case as well, the orthogonalization provides binding. Our binding-by-subspace hypothesis makes two novel predictions borne out by the data. First, behavioral errors should correlate with putative spatial (but not temporal) misbinding in the neural representation. Second, the specific representational geometry that we observe across animals also indicates that behavioral errors should increase when offers have low or high values, compared to when they have medium values, even when controlling for value difference. Together, these results support the idea that the brain makes use of semi-orthogonal subspaces to bind features together.Comment: arXiv admin note: substantial text overlap with arXiv:2205.0676

An inhibitory pull-push circuit in frontal cortex.

Push-pull is a canonical computation of excitatory cortical circuits. By contrast, we identify a pull-push inhibitory circuit in frontal cortex that originates in vasoactive intestinal polypeptide (VIP)-expressing interneurons. During arousal, VIP cells rapidly and directly inhibit pyramidal neurons; VIP cells also indirectly excite these pyramidal neurons via parallel disinhibition. Thus, arousal exerts a feedback pull-push influence on excitatory neurons-an inversion of the canonical push-pull of feedforward input

Individual differences in social information gathering revealed through Bayesian hierarchical models

As studies of the neural circuits underlying choice expand to include more complicated behaviors, analysis of behaviors elicited in laboratory paradigms has grown increasingly difficult. Social behaviors present a particular challenge, since inter- and intra-individual variation are expected to play key roles. However, due to limitations on data collection, studies must often choose between pooling data across all subjects or using individual subjects' data in isolation. Hierarchical models mediate between these two extremes by modeling individual subjects as drawn from a population distribution, allowing the population at large to serve as prior information about individuals' behavior. Here, we apply this method to data collected across multiple experimental sessions from a set of rhesus macaques performing a social information valuation task. We show that, while the values of social images vary markedly between individuals and between experimental sessions for the same individual, individuals also differentially value particular categories of social images. Furthermore, we demonstrate covariance between values for image categories within individuals and find evidence suggesting that magnitudes of stimulus values tend to diminish over time

Pupil Size as a Gateway Into Conscious Interpretation of Brightness

Although retinal illumination is the main determinant of pupil size, evidence indicates that extra-retinal factors, including attention and contextual information, also modulate the pupillary response. For example, stimuli that evoke the idea of brightness (e.g., pictures of the sun) induce pupillary constriction compared to control stimuli of matched luminance. Is conscious appraisal of these stimuli necessary for the pupillary constriction to occur? Participants' pupil diameter was recorded while sun pictures and their phase-scrambled versions were shown to the left eye. A stream of Mondrian patterns was displayed to the right eye to produce continuous flash suppression, which rendered the left-eye stimuli invisible on some trials. Results revealed that when participants were aware of the sun pictures their pupils constricted relative to the control stimuli. This was not the case when the pictures were successfully suppressed from awareness, demonstrating that pupil size is highly sensitive to the contents of consciousness

Preference for novel faces in male infant monkeys predicts cerebrospinal fluid oxytocin concentrations later in life

The ability to recognize individuals is a critical skill acquired early in life for group living species. In primates, individual recognition occurs predominantly through face discrimination. Despite the essential adaptive value of this ability, robust individual differences in conspecific face recognition exist, yet its associated biology remains unknown. Although pharmacological administration of oxytocin has implicated this neuropeptide in face perception and social memory, no prior research has tested the relationship between individual differences in face recognition and endogenous oxytocin concentrations. Here we show in a male rhesus monkey cohort (N = 60) that infant performance in a task used to determine face recognition ability (specifically, the ability of animals to show a preference for a novel face) robustly predicts cerebrospinal fluid, but not blood, oxytocin concentrations up to five years after behavioural assessment. These results argue that central oxytocin biology may be related to individual face perceptual abilities necessary for group living, and that these differences are stable traits