Library · Biology & lab methods
What Optogenetics & Neural Stimulation got wrong, from 21 theses
Summary written by a model from the records below: The records document technical, physical, and methodological limitations encountered when applying optogenetic and electrical neural stimulation techniques across diverse experimental models. Researchers frequently faced challenges including non-specific activation, poor light penetration or expression, kinetic mismatches, off-target behavioral artifacts, and severe animal or unit attrition. These records come from graduate theses, 2021 to 2024, each labeled with its degree where the repository states it, and each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Plus 10 problems the authors left open, listed at the end.
Failure modes, by theses reporting them
Select a mode to jump to its records.
Electrical stimulation causes non-specific activation and fails to scale across neuronal ensembles
Direct electrical stimulation requires high currents that trigger non-specific excitation and introduce co-transmitter confounding effects. Additionally, electrical techniques and collision tests cannot scale to selectively stimulate or record from individual neurons across entire populations.
Considered and rejected
Considered and rejected: Electrophysiology was rejected for functional circuit mapping in favour of all-optical calcium imaging paired with optogenetics because it cannot be scaled to populations.
Octopaminergic Regulation of Olfactory Discrimination in the Drosophila Larval Mushroom Body Calyx · Cambridge · PhD
Considered and rejected
Considered and rejected: Rejected using non-specific electrical stimulation of internal capsule to isolate corticothalamic EPSPs without co-transmitter confounding effects, replacing it with cell-type-specific optogenetic activation in Ntsr1-Cre mice.
The modulation of NREM sleep by corticotropin-releasing hormone through the thalamic reticular nucleus · EPFL · PhD
Tried and failed
temporal interference electrical stimulation applied to cortical neuronal modulation. Reason: Response strength did not depend on difference frequency or envelope amplitude independently of sum amplitude
Biophysical investigation of temporal interference neuromodulation · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected electrical stimulation collision tests for population-level connectivity inference because selective stimulation of individual neurons is not scalable across ensembles.
The Timescales of Transformation Across Brain Structures in the Thalamocortical Circuit · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected direct electric neural stimulation for localized VTA modulation due to high current thresholds (≥50 µA) causing non-specific excitation.
Multifunctional Wireless Gut-Brain Neurotechnology · MIT · PhD
Stimulation frequency and kinetic mismatches distort neural responses or provoke instability
Stimulating beyond opsin kinetic capabilities causes decaying responses, highly variable traces, or failure to reliably evoke neurotransmitter release. Selecting parameters outside narrow operational windows also risks entrainment artifacts, seizure-like activity, or unintended transitions from itch to pain.
Tried and failed
high frequency optogenetic stimulation applied to neuronal activity modulation. Outcome: no signal. Reason: optical stimulation frequency exceeded channelrhodopsin kinetics leading to decaying and uncorrelated responses
Multifunctional Wireless Gut-Brain Neurotechnology · MIT · PhD
Considered and rejected
Considered and rejected: Rejected optogenetics for steady-state rsfMRI mapping because light delivery over large areas is invasive and opsin-mediated activation imposes frequency-dependent entrainment rather than sustained baseline excitability changes.
Probing the mechanisms of fMRI dysconnectivity with chemogenetic-fMRI · University of Trento · PhD
Considered and rejected
Considered and rejected: Rejected optogenetic activation of MRGPRA3+ afferents in favor of metabotropic chemogenetic stimulation because fast optogenetic activation triggers pain rather than itch.
Trpc3 Antagonizes Contact Dermatitis-Induced Pruritus · Penn · PhD
Tried and failed
optogenetic stimulation parameter tuning applied to cortical seizure suppression. Outcome: unstable. Reason: frequencies and pulse widths outside a narrow window provoked seizure-like activity or had no effect
DEAFENING SILENCE: NOVEL ANTIEPILEPTIC TREATMENT FOR MEDICALLY REFRACTORY PARTIAL-ONSET EPILEPSY · Cornell · PhD
Considered and rejected
Considered and rejected: Decided against 4 Hz and 50 Hz optogenetic stimulation frequencies because 4 Hz did not reliably evoke dopamine and 50 Hz produced highly variable traces.
Mesolimbic dopamine and circuit level mechanisms in action initiation and restraint · Oxford · PhD
Insufficient light penetration, low expression, and weak signal output impair optogenetic efficacy
Light delivery to deep brain structures or engineered constructs is constrained by inadequate optical power density, weak expression, and poor three-dimensional penetrance. As a result, optogenetic activation can evoke significantly less transmitter release than electrical stimulation and produces weaker modulation than pharmacological approaches.
Tried and failed
optogenetic inhibition of targeted inhibitory neurons applied to modulating subcortical arousal circuitry. Outcome: worse than baseline. Reason: produced weaker and less reliable behavioral and neural modulation than pharmacological blockade or excitatory photoactivation
INTEGRATED CORTICO-MOTOR FEATURES ASSESS AROUSAL IN COMA EMERGENCE IN RODENTS · Cornell · PhD
Tried and failed
direct-contact micro-LED optogenetic stimulation applied to deep brain target neurons. Outcome: no signal. Reason: optical power density or light penetration was insufficient to modulate targeted deep neuronal activity
Sleep studies in mice - open and closed loop devices for untethered recording and stimulation · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected optogenetic contractility induction constructs (LARIAT, optoGEF-RhoA) for tissue-scale actuation in favor of optochemical blebbistatin photoconversion due to high background noise and poor 3D penetrance.
Mechanical principles of engineering fibrous tissues with programmable shape · EPFL · PhD
Considered and rejected
Considered and rejected: Rejected continuing with the EL222 (LOV-based) optogenetic system due to significantly lower luciferase expression compared to CRY2.
Entwicklung einer lichtinduzierten Proteinsynthese in optogenetisch aktivierbaren Säugerzellen für therapeutische Applikationen · Leibniz Universität Hannover · PhD
Viral delivery failures, low photo-tagging yields, and experimental hurdles cause heavy attrition
In vivo preparations frequently suffer high animal loss caused by lack of viral transduction, inaccurate cannula placement, surgical site infections, or suppressed baseline behavior. Researchers also face obstacles from low single-unit tagging yields across sessions, hardware limitations of pulse generators, and the necessity of genetic modification.
Considered and rejected
Considered and rejected: Two-phase optogenetic stimulation pattern was rejected for stimulating Tdc2-GAL4/CsChrimson neurons due to limitations of the custom pulse generator.
Octopaminergic Regulation of Olfactory Discrimination in the Drosophila Larval Mushroom Body Calyx · Cambridge · PhD
Considered and rejected
Considered and rejected: Rejected using optogenetic channelrhodopsin expression due to requirement for cell genetic modification.
Development of a Mechanically Active Biomaterial for Muscle Tissue Engineering · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected single-unit somatic/antidromic optogenetic photo-tagging for chronic multi-day experiments due to punishingly low yield (~1%) and inability to hold units across weeks
Neuromodulator recruitment during listening and learning in mice and humans. · Harvard · PhD
Lost to a baseline
In Cre-ON/Flp-ON optogenetic experiments targeting VMHvl-projecting MeApd GABA neurons, 6 out of 8 ChETA-expressing mice showed no spontaneous baseline aggression during resident-intruder testing and had to be excluded from primary analysis.
The role of medial amygdala inhibitory neurons in regulating social behavior · EPFL · PhD
Lost to a baseline
Experiment 2 (NAcSh D2R optogenetics): 6 females and 1 male in the eNpHR3.0 group were excluded due to lack of viral transduction (n=3), missed cannula placement (n=3), or optic fiber site infection (n=1).
Roles of sex and gonadal hormones in the modulation of risk-based decision making · UT Austin · PhD
Optical stimulation triggers sensory artifacts and off-target physiological disruptions
Targeted optical manipulation can generate spatially diffuse downstream activation rather than localized somatotopy and cause severe motor arrest instead of choice bias. Furthermore, stimulating light can create behavioral confounds by awakening subjects across genotypes or altering synaptically evoked spiking after opsin silencing.
Tried and failed
optogenetic inhibition of brainstem motor nuclei applied to probing choice bias and switching behavior. Outcome: no signal. Reason: caused non-specific bilateral motor arrest (miss trials) rather than directional choice bias or switching errors
Neural circuit mechanism of choice exploration in the basal ganglia · Harvard · PhD
Tried and failed
localized optogenetic stimulation for somatotopic mapping applied to basal ganglia projection pathways. Outcome: no signal. Reason: focal stimulation produced spatially diffuse downstream neuronal responses rather than discrete somatotopic activation
Substantia nigral activity in self-timed movements · Harvard · PhD
Considered and rejected
Considered and rejected: Rejected using halorhodopsin (NpHR) for optogenetic silencing due to reported problematic changes in synaptically evoked spiking activity following light activation.
Examination of a locus coeruleus to dentate gyrus noradrenergic circuit in aversive contextual processing · University of Washington · PhD
Considered and rejected
Considered and rejected: Decided against optogenetic activation assays because stimulating light inherently woke up flies across all genotypes.
Cross-species investigation of hypersomnia genetics: a role for synaptic adhesion molecules · Penn · PhD
Left open by the authors
Problems the authors named and did not get to.
Left open
Optogenetically stimulate axonal arbors of piriform feedback fibers in olfactory bulb slices to rescue trailing beta oscillations. Blocker: Requires wet lab, transgenic mice (Ntsr1-cre GN209), brain slice preparation, optogenetic stimulation rig, and MEA recording equipment
DYNAMICS OF SPIKE-TIMING AND GAMMA OSCILLATIONS IN THE OLFACTORY BULB · Cornell · PhD
Left open
Perform optogenetic influence mapping across varying visual stimulus contrasts and natural movies to test shifts from neural amplification to competition. Blocker: Requires two-photon optogenetic photostimulation and calcium imaging in transgenic mice (wet lab / physical optics rig).
Optical investigation of microcircuit computations in mouse primary visual cortex · Harvard · PhD
Left open
Test silent callosal synapses by measuring failure rates of AMPAR and NMDAR EPSCs under minimal optogenetic stimulation. Blocker: Requires a wet lab, animal models, electrophysiology rigs, and optogenetic apparatus
Experience-Dependent and Input-Specific Regulation of Neocortical Circuit Development by Genes Linked to Neurodevelopmental Disorders · UT Southwestern · PhD
Left open
Test intraneural optic nerve stimulation in non-human primates and assess phosphene localization through behavioral tasks. Blocker: Requires non-human primate animal facility, surgical implantation, behavioral testing setup, and specialized neural hardware
Investigation of electrical stimulation of the optic nerve for artificial vision · EPFL · PhD
Left open
Replace unpredicted background rewards with optogenetic stimulation/inhibition of dopamine fibers innervating the olfactory tubercle during contingency learning experiments. Blocker: Requires a wet lab, live mice, optogenetic apparatus, and specialized neural recording equipment
Neural circuit mechanisms underlying contingency learning · Harvard · PhD
Left open
Determine the functional logic and organizing principles of non-canonical striatonigral projections using electrophysiology and optogenetic stimulation. Blocker: Requires mouse in vivo electrophysiology wet lab, optogenetic stimulation hardware, and transgenic animal lines.
Substantia nigral activity in self-timed movements · Harvard · PhD
Left open
Train animals in a Pavlovian task using projection-specific dopamine optogenetic stimulation instead of water rewards to measure cortical belief dynamics. Blocker: Requires a wet lab, animal subjects, and optogenetic stimulation equipment.
Biological constraints and mechanisms for reinforcement learning · Harvard · PhD
Left open
Test whether non-human primate discrimination of retinotopic-scale optogenetic stimulation in V1 improves with behavioral training extended beyond two weeks. Blocker: Requires non-human primates, optogenetics/imaging rig, surgical preparation, and an animal behavior lab
Causal testing of the importance of V1 topography in coarse shape perception via spatially patterned optogenetics · UT Austin · PhD
Left open
Photostimulate fewer neural targets across more stimulation trials to quantify influence mapping on a single-pair basis. Blocker: Requires a wet lab, transgenic mice, two-photon imaging, and optogenetic photostimulation hardware.
Optical investigation of microcircuit computations in mouse primary visual cortex · Harvard · PhD
Left open
Perform optogenetic and chemogenetic manipulation of vCA1/vCA3 and LSCrhr2 neurons during arousal and defensive behavioral assays. Blocker: Requires a wet lab, animal subjects, stereotaxic surgeries, viral opsin vectors, and behavioral/photometry apparatus.
Threat processing via the septohippocampal system · Harvard · PhD
Who has worked on this
Authors of the public theses cited on this page, most-cited first.
- Atharva Sahasrabudhe · MIT · PhD · 2024
Multifunctional Wireless Gut-Brain Neurotechnology - Lingfeng Hou · Harvard · PhD · 2023
Substantia nigral activity in self-timed movements - Anna Jaffe · Harvard · PhD · 2022
Optical investigation of microcircuit computations in mouse primary visual cortex - Alex McLachlan · Cambridge · PhD · 2021
Octopaminergic Regulation of Olfactory Discrimination in the Drosophila Larval Mushroom Body Calyx - Sandra Alejanfra Romero Pinto · Harvard · PhD · 2024
Biological constraints and mechanisms for reinforcement learning - Lechen Qian · Harvard · PhD · 2024
Neural circuit mechanisms underlying contingency learning - Loredana Cumpana · EPFL · PhD · 2024
The modulation of NREM sleep by corticotropin-releasing hormone through the thalamic reticular nucleus - David Sastre Yagüe · University of Trento · PhD · 2024
Probing the mechanisms of fMRI dysconnectivity with chemogenetic-fMRI - Eric Zhang · University of Washington · PhD · 2024
Examination of a locus coeruleus to dentate gyrus noradrenergic circuit in aversive contextual processing - Kyla Mace · Penn · PhD · 2024
Cross-species investigation of hypersomnia genetics: a role for synaptic adhesion molecules - Salvador Ignacio Brito Matehuala · Harvard · PhD · 2023
Threat processing via the septohippocampal system - Sijia Gao · Cornell · PhD · 2023
INTEGRATED CORTICO-MOTOR FEATURES ASSESS AROUSAL IN COMA EMERGENCE IN RODENTS
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