About

Michael Arcaro, PhD, is a faculty member in the Biomedical Graduate Studies at the Perelman School of Medicine at the University of Pennsylvania. His research combines neuroimaging, behavioral psychophysics, and electrophysiology to understand how intrinsic and experience-driven processes interact throughout development to shape brain organization and behavior. His current focus is on neural development supporting visual object recognition across mammalian species. His work explores how the mammalian brain's complex architecture, which varies in cyto- and chemo-architecture, connectivity, and functional response properties, supports perception and is shaped by experience. Dr. Arcaro's research aims to elucidate how environment influences neural development and how emerging neural architecture supports perception and behavior.

Research topics

• Neuroscience
• Psychology
• Computer science
• Cognitive psychology
• Biology

Selected publications

• Transformation-tolerant object recognition in tree shrews despite lacking a fovea

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-04-14

  articleOpen accessSenior author

  Abstract Object recognition depends on the ability to extract stable representations across changes in how they are viewed, yet it remains unclear how this capacity depends on visual acuity and cortical hierarchy. We combined behavioral testing and computational modeling to determine whether tree shrews, close relatives of primates with lower spatial acuity, can perform transformation-tolerant object recognition. Front-end modeling incorporating species-specific optics and photoreceptor sampling showed that, when scaled for acuity, tree shrew retinal filtering preserves the similarity structure of natural image categories relevant for object recognition. Behaviorally, tree shrews reliably discriminated complex objects across variations in position, scale, and viewpoint, including when embedded within natural scenes, and generalized to novel exemplars. Their recognition behavior was best explained by visual features emphasizing differences in global shape and size between objects and by representations from intermediate and deep layers of hierarchical neural network models. These results demonstrate that visual processing supporting object-level generalization can arise within visual systems lacking high-acuity front-end optics and establish the tree shrew as a key model for understanding the computational and evolutionary origins of high-level vision.

  PublisherDOI

• Cascading periods of language-related brain plasticity across early childhood

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-03-27

  articleOpen access

  Abstract Language is thought to have multiple sensitive periods in early childhood, but the neural basis of these sensitive periods is less understood. We leverage advances in in-vivo neuroimaging of plasticity, measuring the neural inhibition across the brain via Hurst exponent. Using two large datasets with children ages 10 months to 15 years (Baby Connectome Project: 10m-3y6m, 458 observations across n =222 children; Human Connectome Project-Development: 5-15y, n =324), we characterize the development of the Hurst exponent in language-related brain regions. In early childhood, Hurst increases in temporal and frontal language areas, and posterior regions develop earlier than anterior regions. In contrast, thalamic Hurst plateaus earlier, perhaps underlying the earliest language-related sensitive periods. Children with higher language-related skills show slower increases in cortical Hurst in early childhood, suggesting protracted plasticity. Later in childhood, cortical Hurst plateaus around age 9, suggesting a potential neural mechanism for age-related declines syntax learning. These results highlight a potential neural basis for cascading language-related sensitive periods. Research highlights Language has multiple, cascading sensitive periods, but the neural basis of these sensitive periods is not well-understood. We leverage advances in in-vivo neuroimaging to quantify plasticity in language-related brain regions across childhood via Hurst, a measure of inhibition. We find that Hurst increases (plasticity decreases) in a graded fashion, with posterior regions maturing before anterior regions. Thalamic hurst plateaus in the first year of life, while cortical Hurst plateaus at age 9, suggesting a neural basis for distinct language-related sensitive periods.

  PublisherDOI

• Functional organization of the human visual system at birth and across late gestation

  Open Science Framework · 2026-01-01

  articleOpen accessSenior author

  Code and summary data associated with "Functional organization of the human visual system at birth and across late gestation."

  PublisherDOI

• Geometric constraints in the development of primate extrastriate visual cortex

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-07

  articleOpen access

  Abstract Sensory systems are organized into topographic maps that shape information flow and computation across cortical circuits. Although the mechanisms establishing primary sensory maps are well characterized, how higher-order maps emerge across neocortex is unclear. Because the probability and strength of cortical connections fall off steeply with distance along a folded surface, the geometry of the cortex may be a major factor shaping the organization of higher-order maps. To test this in a well-characterized sensory system, we develop a growth model embedded in the folded surface geometry of the macaque visual cortex, using fMRI-defined V1 retinotopy as the sole functional anchor. Cortical organization emerges through algorithmic growth from primary visual cortex, governed by distance-dependent activity correlations and competition among developing projections. Without imposing areal boundaries, map orientations, or predefined topographic layouts, this process generates multiple retinotopic maps with systematic mirror reversals and smooth gradients that reflect key structural features of fMRI-derived extrastriate maps. Parameters estimated on a population template generalize across individual macaques, while individual cortical geometry accounts for fine-scale map variation around a common retinotopic scaffold. These results suggest that conserved growth rules acting on folded cortical surfaces produce stereotyped higher-order retinotopic organization under minimal explicit specification.

  PublisherDOI

• Alcohol impacts an fMRI marker of neural inhibition in humans and rodents

  NeuroImage · 2026-03-31

  articleOpen access

  • The fMRI Hurst exponent has been proposed as a marker of neural inhibition. • Alcohol was used to test the validity of the Hurst exponent across species. • Acute alcohol significantly reduced the cortical Hurst exponent in rats and humans. • Hurst reductions correlated with spatial distribution of GABAA receptor expression. • Results provide direct evidence linking the Hurst exponent to neural inhibition. Inhibitory neuronal activity is a key regulator of brain function and is implicated in numerous developmental and psychiatric disorders. However, measuring inhibition in vivo remains a challenge. The Hurst exponent of the fMRI signal has been shown to correlate spatially with cellular measures of neural inhibition, but there have been few causal tests of the relationship between the Hurst exponent and neural inhibition. Here, we used alcohol, a drug with known impacts on inhibition, as a way to evaluate the validity of the Hurst exponent as a marker of neural inhibition across rats and humans. In rats, acute alcohol administration significantly reduced the cortical Hurst exponent, with the spatial distribution of effects closely aligned with GABA A receptor expression. In humans, alcohol exposure similarly decreased the cortical Hurst exponent, particularly in regions with high GABA A receptor expression, demonstrating cross-species consistency. These results provide convergent in vivo evidence that the Hurst exponent is sensitive to pharmacologically induced changes in inhibitory neuronal activity.

  PublisherDOI

• Alcohol impacts an fMRI marker of neural inhibition in humans and rodents

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-05-13 · 1 citations

  preprintOpen access

  Abstract Acute alcohol consumption leads to cognitive and behavioral disinhibition that increase health and social risks, such as traffic fatalities and violence. Although rodent studies have shown that alcohol affects inhibitory neuronal activity, its relevance to humans remains largely unexplored. Here, we used the Hurst exponent—an fMRI-based marker of neural inhibition—to examine alcohol’s effects in both rats and humans. In rats, acute alcohol administration significantly reduced the cortical Hurst exponent, suggesting a decrease in inhibitory neuronal activity. This reduction was strongly correlated with the spatial distribution of GABA A receptor expression, highlighting the key role of these receptors in mediating alcohol’s effects. Similarly, in humans, acute alcohol consumption reduced the cortical Hurst exponent, especially in brain regions with high GABA A receptor expression. Our findings provide cross-species in vivo evidence that acute alcohol consumption modulates neural inhibition, offering new insights into the neural mechanisms underlying alcohol-induced behavioral modulation.

  PublisherOA PDFDOI

• Author response: Movies reveal the fine-grained organization of infant visual cortex

  2025-03-06

  peer-reviewOpen access

  How babies see the world is a mystery. They cannot share their experiences, and adults cannot recall this time. Clever experimental methods are needed to understand sensory processing in babies' brains and how variations from adults could cause them to have different experiences. However, finding ways to study infant brain structure and function has challenged scientists. Babies cannot complete many cognitive tasks used to assess adult brain activity. It can also be difficult to use imaging tools like magnetic resonance imaging (MRI) that require individuals to lay still for extended periods, which can be challenging for infants who are often wiggly and have short attention spans. As a result, many questions remain unanswered about infant brain organization and function. Recent technological advances have made it easier to study infant brain activity. Scientists have developed approaches allowing infants to watch a movie while being comfortably positioned in an MRI machine. Infants and toddlers will often happily watch a film for minutes at a time, enabling scientists to observe how their brains respond to what they see on the screen. Ellis et al. used this approach to assess the organization of the visual system in the brains of 15 infants while they watched movies during functional MRI. The researchers compared the infant scans with scans of adult brains who watched the same film, which revealed that babies’ brain activity is surprisingly structured and similar to that of adults. Moreover, the organization of the adult brain could predict the organization of the infant brain. Ellis et al. show that scanning infants while they watch movies can be a valuable way to study their brain activity. The experiments reveal important similarities in adult and infant visual processing, helping to identify the foundation on which visual development rests. The movie-watching experiments may also provide a model for scientists to study other types of infant perception and cognition. Movies can help scientists compare brain activity in typically developing infants to those with neurodevelopmental conditions, which could one day help clinicians create new avenues for diagnosis or treatment.

  PublisherDOI

• Functional organization of the human visual system at birth and across late gestation

  Neuron · 2025-09-22 · 1 citations

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Exploring the influence of binocular anti-coactivation on ocular dominance column formation beyond primary visual cortex

  Journal of Vision · 2025-07-15

  articleOpen access

  Inputs from the lateral geniculate nucleus segregate into ocular dominance columns in layer 4 of the macaque primary visual cortex (V1) via Hebbian mechanisms. Beyond V1 layer 4, most visual neurons are binocular. Research on developing frogs with transplanted third eyes revealed abnormal ocular dominance patterns despite lacking binocular overlap (Constantine-Paton et al., 1978). Inspired by this, we manipulated early visual experience in infant macaques to anti-correlate eye activity. Two macaques wore helmets with liquid crystal shutter lenses alternated at 0.1 Hz for the first postnatal year to test if anti-correlated activity induces ocular dominance columns beyond V1, providing insights into feature domain development in higher areas like the inferior temporal cortex. After rearing, one eye was injected with tetrodotoxin for 3 weeks, and ~500 sagittal sections (70 µm thick) were processed for cytochrome oxidase staining. We developed a pipeline to analyze ocular dominance columns in 2D slices and reconstruct 3D volumes of CO staining at different laminar depths (Oishi et al. 2024). Slices were co-registered and combined to construct a 3D histology volume, aligned to a reference MRI, revealing clear ocular dominance columns across the cortical surface extending beyond layer 4 of V1. To quantify column periodicity, visual areas in slices were segmented and flattened into 1D vectors, capturing staining intensity variations. Flattened 1D vectors were assembled into a cortical sheet, revealing the 2D column structure beyond V1. FFT analysis confirmed accurate reconstruction of columns in V1 and their presence beyond V1. The average column periodicity was 506.06±110µm in V1, 550.59±145µm in V2 ventral, and 554.98±137µm in V2 dorsal. The larger domains beyond V1 indicate that 1) Hebbian mechanisms act during development to segregate domains according to patterns of neuronal activity, even beyond primary sensory areas; and 2) hierarchical convergence creates larger domains (Nasr et al., 2016).

  PublisherDOI

• Modeling tree shrew high-level visual behaviors

  Journal of Vision · 2025-07-15

  articleOpen accessSenior author

  A hallmark of primate vision is the ability to quickly recognize objects despite considerable variations in how an object is projected onto the retina. However, the evolutionary origins of this behavior remain poorly understood. Among the closest relatives to primates, tree shrews (Tupaia belangeri) offer unique insights into the evolution of visual processing. Their extensive extrastriate cortex and visually guided behaviors represent key adaptations that may have supported advanced object recognition in primates. We trained three adult tree shrews on a match-to-sample task using stimuli previously used to demonstrate complex object recognition in humans, macaques, and marmosets. Like primates, tree shrews successfully identified objects across variations in position, size, and orientation, and when embedded in complex scenes. Moreover, behavioral performance was correlated across shrews, suggesting they utilize a common shape representation. To gain deeper insight into the representations driving their behavior, we compared tree shrew performance with predictions from visual processing models. We accounted for tree shrew optics using a front-end visual system model, ISETBio, then employed deep convolutional neural networks (DCNN) to probe the visual representations emerging from core features of the primate visual system—hierarchical connectivity and convolutional processing. We analyzed the correspondence between DCNN layer representations and tree shrew behavioral performance, finding that layers best predicting tree shrew performance varied with task complexity. While this provides insights into the depth of processing, it does not reveal which specific stimulus features drive tree shrew behavior. Moreover, the most diagnostic stimulus features for tree shrew behavior may not be captured by DCNNs. Therefore, we are testing models representing specific aspects of processing, including local texture (Gabor-jet model), structural shape (skeletal model), and visual saliency (SALICON). These findings help establish tree shrews as a model for high-level processing and offer insights not just about whether, but how they discriminate complex objects.

  PublisherDOI

Frequent coauthors

• Cameron T. Ellis

  57 shared

• Tristan S. Yates

  Yale University

  56 shared

• Nicholas B. Turk‐Browne

  Yale University

  56 shared

• Sabine Kästner

  31 shared

• Margaret S. Livingstone

  Harvard University

  31 shared

• Uri Hasson

  Neuroscience Institute

  17 shared

• Kendrick Kay

  Resonance Research (United States)

  12 shared

• Kevin S. Weiner

  University of California, Berkeley

  10 shared

Education

• PhD Psychology and Neuroscience, Psychology

  Princeton University

  2013