About

Stephen Engel is a professor of psychology at the University of Minnesota, with a Ph.D. in Psychology from Stanford University obtained in 1995. His research focuses on understanding how neurons in the human brain support visual perception, utilizing methods of cognitive neuroscience. His lab combines behavioral measurements with functional MRI and EEG to investigate the neural mechanisms underlying visual perception and plasticity in the visual system. Engel's work explores how the adult visual system can modify itself through visual adaptation and learning, including studies on the effects of altered reality using VR technology. His research includes examining how the visual system responds to environmental changes, such as the removal or enhancement of vertical lines, over various time periods. Additionally, he applies his findings to clinical therapies, investigating the use of altered reality to assist individuals with macular degeneration and applying neuroplasticity principles to treat conditions like strabismus and amblyopia.

Research topics

• Psychology
• Neuroscience
• Computer science
• Cognitive psychology
• Artificial intelligence

Selected publications

• Spatial remapping improves reading with simulated central field loss

  Journal of Vision · 2026-04-17

  articleOpen accessSenior author

  One way to potentially aid reading with central field loss (CFL) is to spatially remap text outside the scotoma to appear in functioning visual field locations. We tested spatial remapping using a sentence reading task with typically sighted readers and simulated scotomata. Participants read sentences with six different remapping strategies of shifting text around the scotoma and with simulated scotomata of three shapes to assess (a) whether spatial remapping improved reading speed generally and (b) whether customization of spatial remapping based on the shape of the simulated scotoma provided additional improvement. Faster reading was observed in at least one remapping condition compared to a no-remapping condition with a simulated scotoma in all participants, with an average improvement of 23.80%. Customization was also important; the remapping strategies that resulted in the fastest reading depended on the shape of the scotoma. The results showed a strong effect of remapping on reading speed. Thus, customizable spatial remapping can aid reading in the presence of a simulated scotoma and should be considered for evaluation in patients with CFL, where it can be used to shift text to areas with functioning visual capabilities.

  PublisherDOI

• Center-surround processing in psychosis

  Biological Psychiatry Cognitive Neuroscience and Neuroimaging · 2026-03-01

  article
  PublisherDOI

• The Motion Aftereffect in Visual Snow

  Journal of Vision · 2025-07-15

  articleOpen accessSenior author

  Visual snow (VS) is the perception of tiny flickering dots covering the visual field. VS is estimated to affect ~4% of the population and, when combined with other symptoms, can be disabling. VS likely arises from spontaneous (non-stimulus driven) activity in the visual pathways, but the specific regions involved are unknown. We sought to determine whether the neural activity producing VS arises at or before motion selective areas. The motion aftereffect (opposite-direction illusory motion perceived after adapting to motion) results from neural adaptation in motion selective regions including area V5/MT. If the activity generating VS reaches these neurons, the VS symptom should be susceptible to the motion aftereffect. Eleven participants with VS viewed high-contrast, horizontally drifting gratings on the left and right of a central fixation point. The gratings (0.3 cyc / degree, 2 Hz) drifted towards or away from the center, which should produce opposing aftereffects. Adapter duration varied across trials (1.6, 5, 15, or 45 sec, each repeated on 4 trials). The gratings were replaced with blank circles in which participants judged the motion of their VS. Participants pressed a button when the motion of the snow inside the circles matched, indicating the duration of the effect. To ensure participants with VS experienced a typical motion aftereffect for external stimuli, stationary square-waves were shown in a control condition. Most participants (10/11) reported that after adaptation, their VS moved in the opposite direction of the adapting gratings. Longer adapter durations resulted in longer-lasting effects (ANOVA F10,1 = 74.4, p = 6.1 ⨉ 10-6) following a power law, consistent with prior motion aftereffect literature. VS was susceptible to the motion aftereffect, indicating the neural activity responsible for snow reaches motion selective neurons, and therefore arises early in the visual pathways, at or before area V5/MT.

  PublisherDOI

• Visual snow: Symptomology and mechanisms

  Journal of Vision · 2025-07-15

  articleOpen accessSenior author

  Visual snow is a recently isolated and surprisingly common (~2-3% of the population) symptom where people continuously perceive tiny flickering dots covering their entire visual field. When combined with other commonly co-occurring symptoms it can interfere with daily activities. The details of visual snow’s symptomology and its underlying mechanisms are poorly understood, limiting the development of treatments. We recently provided the first detailed measurements of visual snow's appearance: Participants adjusted parameters of a simulation to match their symptom. On average, individual elements were very small and fast, and total contrast was low (~2.5% RMS). We also recently demonstrated that snow is dependent upon spontaneous neural activity in the visual system: In people with visual snow, adapting to high contrast external dynamic noise greatly reduced the strength of the snow (transiently) to the point that it disappeared in most observers, some of whom reported seeing the world without snow for the first time. Adaptation to visual noise reduces neural responsiveness in early visual cortex, suggesting that spiking there is necessary for the snow percept. And because effects were measured while viewing a blank screen, this activity must be spontaneous. Current work uses adaptation to identify precisely where and how the spontaneous activity arises, e.g. visual snow shows a motion aftereffect. Drawing upon expertise from the visual snow community, including one of us, was crucial for developing our experimental paradigms, which may in turn provide a window onto noise suppression processes in normally sighted individuals.

  PublisherDOI

• Visual Snow is Susceptible to the Motion Aftereffect

  2025-02-06

  preprintOpen accessSenior author

  Objective: For people with visual snow, the visual field is covered in faint flickering specks. Visual snow remains poorly understood and lacks effective treatments. The snow is likely produced by spontaneous (non-stimulus driven) activity in the visual system, but the specific neural mechanisms are not known. We hypothesize that the activity producing visual snow is present early in the visual pathways. Here, we tested whether it reaches motion selective areas, including V5/MT, using the motion aftereffect.Methods: Eleven participants with visual snow syndrome (VSS) adapted to high contrast drifting gratings on the left and right sides of a central fixation point, moving in opposite directions. After adaptation, participants judged motion visible in their visual snow viewed on a blank screen, pressing a button when the motion of the snow on both sides looked the same. The duration of the adapter gratings varied across trials (1.6 - 45 sec). In a control condition, we presented a stationary square wave pattern during the test period to confirm that participants with VSS experienced a typical motion aftereffect for external stimuli. Results: Following adaptation, most participants (10/11) reported that their visual snow moved in the opposite direction of the adapting gratings, as expected for the motion aftereffect. Longer adapter durations resulted in longer-lasting illusions and this relationship was linear on a log-log axis, consistent with the motion aftereffect literature. Conclusions: Visual snow is susceptible to the motion aftereffect, suggesting that the neural activity producing visual snow reaches motion selective neurons involved in perceiving the motion aftereffect, which are believed to include V5/MT. If visual snow arises before area V5/MT, our findings suggest this activity is propagated forward through the visual pathways. Pinpointing the neural origins of visual snow may facilitate the development of novel treatment approaches targeting specific visual brain areas or networks.

  PublisherDOI

• Cholinergic regulation of prolonged alcohol withdrawal differs by sex

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-12-16

  articleOpen access

  Acute alcohol withdrawal encompasses somatic withdrawal signs and increased negative affect. In prolonged alcohol withdrawal the somatic withdrawal signs have resolved but the increased negative affect persists. We investigated acute and prolonged alcohol withdrawal after 9 daily injections of 2.5 g/kg alcohol plus 4-methypyrazole, an alcohol dehydrogenase inhibitor, in male and female C57BL/6J mice, and examined whether nicotinic acetylcholine receptor (nAChR) drugs could attenuate withdrawal-induced negative affect. Male mice showed changing somatic withdrawal signs over time and negative affect that persisted at least 21 days into withdrawal. Pre-treatment with mecamylamine, a non-specific nAChR antagonist, or varenicline, a nAChR partial agonist, reduced withdrawal-induced anxiety- and compulsive-like behavior in the marble-burying test during prolonged withdrawal. In contrast, female mice did not exhibit somatic withdrawal signs or anxiety- or compulsive-like behaviors. Instead, female mice showed a deficit in social interaction that was not attenuated by mecamylamine. Alcohol clearance and sedation were not different between sexes, indicating that differences in withdrawal signs and negative affect are not confounded by differences in alcohol metabolism. These findings suggest that cholinergic drugs may be a promising therapeutic for withdrawal-induced negative affect in male, but not female, mice.

  PublisherOA PDFDOI

• Center-surround processing in psychosis

  medRxiv · 2025-08-19 · 1 citations

  preprintOpen access

  Purpose: People with psychotic psychopathology (PwPP) often experience subtle variations in visual perception, which can be quantified experimentally. In the contrast surround suppression illusion, a central pattern appears to have lower contrast in the presence of a surrounding pattern. PwPP typically show weaker contrast suppression from the surround than controls, but the mechanisms underlying this difference are still poorly understood. Methods: We assessed perceptual and neural surround suppression in 38 controls, 44 first-degree biological relatives of PwPP, and 64 PwPP as part of the Psychosis Human Connectome Project. To better understand neural mechanisms contributing to diminished surround suppression we quantified contrast discrimination thresholds and examined 7 tesla fMRI responses in the lateral geniculate nucleus (LGN), primary visual cortex (V1), and lateral occipital complex (LOC). Additionally, we measured the concentration of γ-aminobutyric acid (GABA; an inhibitory neurotransmitter) in occipital cortex using 7 T MR spectroscopy. Results: Responses in LOC showed the expected effect of weaker surround suppression in PwPP and relatives versus controls. However, in V1 we found no differences in surround suppression strength between controls, relatives, and PwPP. Additionally, we saw no behavioral evidence for reduced surround suppression in PwPP. Suppression metrics were not significantly correlated with occipital GABA levels or symptom measures. Multi-voxel pattern analysis of V1 fMRI responses revealed a group difference in decoding Surround vs. No Surround, with a trend toward lower accuracy in PwPP vs. controls. Conclusion: Our results suggest subtle differences in visual center-surround processing among people with schizophrenia. Possible explanations for the discrepancy with previous findings include differences in task design and the deployment of spatial attention across groups. Poorer decoding of center vs. surround may suggest neural representations of spatial context in V1 are less reliable in PwPP.

  PublisherOA PDFDOI

• Beyond Increasing Sample Sizes: Optimizing Effect Sizes in Neuroimaging Research on Individual Differences

  Journal of Cognitive Neuroscience · 2025-01-01 · 21 citations

  reviewOpen access

  Linking neurobiology to relatively stable individual differences in cognition, emotion, motivation, and behavior can require large sample sizes to yield replicable results. Given the nature of between-person research, sample sizes at least in the hundreds are likely to be necessary in most neuroimaging studies of individual differences, regardless of whether they are investigating the whole brain or more focal hypotheses. However, the appropriate sample size depends on the expected effect size. Therefore, we propose four strategies to increase effect sizes in neuroimaging research, which may help to enable the detection of replicable between-person effects in samples in the hundreds rather than the thousands: (1) theoretical matching between neuroimaging tasks and behavioral constructs of interest; (2) increasing the reliability of both neural and psychological measurement; (3) individualization of measures for each participant; and (4) using multivariate approaches with cross-validation instead of univariate approaches. We discuss challenges associated with these methods and highlight strategies for improvements that will help the field to move toward a more robust and accessible neuroscience of individual differences.

  PublisherOA PDFDOI

• The Preferred Retinal Locus for Reading in Central Vision Loss

  Investigative Ophthalmology & Visual Science · 2025-11-06 · 1 citations

  articleOpen access

  Purpose: People with central vision loss (CVL) often adopt a preferred retinal locus (PRL) for fixation outside the region of central loss. However, it is unknown how often the fixational PRL (fPRL) is used in reading. Here, we assessed if the reading PRL is in the same location as the fPRL. Methods: Participants read text on a computer screen. Reading was randomly interrupted by blanking the screen, and participants reported the word being read when the blanking occurred. The location of this word was compared to the fPRL location, measured with an eye tracker. If reading uses the fPRL, the two locations should overlap. We validated our method with 10 normally sighted controls for whom the fPRL and reading PRL should coincide at the fovea. We then tested 20 participants with CVL. Results: Control participants reported the word at the fPRL, or the next word, in 77.03% of trials. Participants with CVL reported the word at the fPRL, or the next word, on 70.45% of trials. Seventeen reported the word at the fPRL most frequently. Two reported the word to the right of the PRL most frequently, possibly due to a look-ahead strategy. One reported the word to the left of the fPRL most frequently, the target of many regressive saccades. Only one participant with CVL used a reading PRL remote from the fPRL, consistently reporting the word 2 degrees below the fPRL. Conclusions: Most of the participants with CVL in our sample used a reading PRL in close proximity to their fixation PRL.

  PublisherOA PDFDOI

• Visual Snow is Susceptible to the Motion Aftereffect

  2025-02-06

  preprintOpen access

  Objective: For people with visual snow, the visual field is covered in faint flickering specks. Visual snow remains poorly understood and lacks effective treatments. The snow is likely produced by spontaneous (non-stimulus driven) activity in the visual system, but the specific neural mechanisms are not known. We hypothesize that the activity producing visual snow is present early in the visual pathways. Here, we tested whether it reaches motion selective areas, including V5/MT, using the motion aftereffect.Methods: Eleven participants with visual snow syndrome (VSS) adapted to high contrast drifting gratings on the left and right sides of a central fixation point, moving in opposite directions. After adaptation, participants judged motion visible in their visual snow viewed on a blank screen, pressing a button when the motion of the snow on both sides looked the same. The duration of the adapter gratings varied across trials (1.6 - 45 sec). In a control condition, we presented a stationary square wave pattern during the test period to confirm that participants with VSS experienced a typical motion aftereffect for external stimuli. Results: Following adaptation, most participants (10/11) reported that their visual snow moved in the opposite direction of the adapting gratings, as expected for the motion aftereffect. Longer adapter durations resulted in longer-lasting illusions and this relationship was linear on a log-log axis, consistent with the motion aftereffect literature. Conclusions: Visual snow is susceptible to the motion aftereffect, suggesting that the neural activity producing visual snow reaches motion selective neurons involved in perceiving the motion aftereffect, which are believed to include V5/MT. If visual snow arises before area V5/MT, our findings suggest this activity is propagated forward through the visual pathways. Pinpointing the neural origins of visual snow may facilitate the development of novel treatment approaches targeting specific visual brain areas or networks.

  PublisherDOI

Recent grants

• NIH Grant R01EY011862

  NIH · $783k · 2007

• Mechanisms of long-term adaptation in visual cortex

  NSF · $454k · 2010–2014

• Testing and surpassing limits of adaptation in visual cortex

  NSF · $549k · 2016–2022

• REU Site: Summer Research in Neuroimaging for Cognitive Neuroscience

  NSF · $349k · 2018–2024

• NIH Grant R55EY011862

  NIH · $100k · 1999

Frequent coauthors

• Katherine E.M. Tregillus

  University of Minnesota

  33 shared

• Min Bao

  University of Chinese Academy of Sciences

  32 shared

• Sheng He

  Institute of Biophysics

  27 shared

• Juraj Mesík

  25 shared

• Junghee Lee

  University of Alabama at Birmingham

  23 shared

• Jonathan K. Wynn

  University of California, Los Angeles

  23 shared

• Michael F. Green

  University of California, Los Angeles

  23 shared

• Sucharit Katyal

  Inserm

  21 shared

Labs

• Engel Vision & Imaging LabPI