@article {6897, title = {Procedures for behavioral experiments in head-fixed mice.}, journal = {PLoS One}, volume = {9}, year = {2014}, month = {2014}, pages = {e88678}, abstract = {

The mouse is an increasingly prominent model for the analysis of mammalian neuronal circuits. Neural circuits ultimately have to be probed during behaviors that engage the circuits. Linking circuit dynamics to behavior requires precise control of sensory stimuli and measurement of body movements. Head-fixation has been used for behavioral research, particularly in non-human primates, to facilitate precise stimulus control, behavioral monitoring and neural recording. However, choice-based, perceptual decision tasks by head-fixed mice have only recently been introduced. Training mice relies on motivating mice using water restriction. Here we describe procedures for head-fixation, water restriction and behavioral training for head-fixed mice, with a focus on active, whisker-based tactile behaviors. In these experiments mice had restricted access to water (typically 1 ml/day). After ten days of water restriction, body weight stabilized at approximately 80\% of initial weight. At that point mice were trained to discriminate sensory stimuli using operant conditioning. Head-fixed mice reported stimuli by licking in go/no-go tasks and also using a forced choice paradigm using a dual lickport. In some cases mice learned to discriminate sensory stimuli in a few trials within the first behavioral session. Delay epochs lasting a second or more were used to separate sensation (e.g. tactile exploration) and action (i.e. licking). Mice performed a variety of perceptual decision tasks with high performance for hundreds of trials per behavioral session. Up to four months of continuous water restriction showed no adverse health effects. Behavioral performance correlated with the degree of water restriction, supporting the importance of controlling access to water. These behavioral paradigms can be combined with cellular resolution imaging, random access photostimulation, and whole cell recordings.

}, issn = {1932-6203}, doi = {10.1371/journal.pone.0088678}, author = {Guo, Zengcai V and Hires, S Andrew and Li, Nuo and O{\textquoteright}Connor, Daniel H and Komiyama, Takaki and Ophir, Eran and Huber, Daniel and Bonardi, Claudia and Morandell, Karin and Gutnisky, Diego and Peron, Simon and Xu, Ning-long and Cox, James and Svoboda, Karel} } @article {6963, title = {Structural plasticity within the barrel cortex during initial phases of whisker-dependent learning.}, journal = {The Journal of Neuroscience}, volume = {34}, year = {2014}, month = {2014 Apr 23}, pages = {6078-83}, abstract = {

We report learning-related structural plasticity in layer 1 branches of pyramidal neurons in the barrel cortex, a known site of sensorimotor integration. In mice learning an active, whisker-dependent object localization task, layer 2/3 neurons showed enhanced spine growth during initial skill acquisition that both preceded and predicted expert performance. Preexisting spines were stabilized and new persistent spines were formed. These findings suggest rapid changes in connectivity between motor centers and sensory cortex guide subsequent sensorimotor learning.

}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.4919-12.2014}, author = {Kuhlman, Sandra J and O{\textquoteright}Connor, Daniel H and Fox, Kevin and Svoboda, Karel} } @article {6158, title = {The mechanical variables underlying object localization along the axis of the whisker.}, journal = {The Journal of Neuroscience}, volume = {33}, year = {2013}, month = {2013 Apr 17}, pages = {6726-41}, abstract = {

Rodents move their whiskers to locate objects in space. Here we used psychophysical methods to show that head-fixed mice can localize objects along the axis of a single whisker, the radial dimension, with one-millimeter precision. High-speed videography allowed us to estimate the forces and bending moments at the base of the whisker, which underlie radial distance measurement. Mice judged radial object location based on multiple touches. Both the number of touches (1-17) and the forces exerted by the pole on the whisker (up to 573 μN; typical peak amplitude, 100 μN) varied greatly across trials. We manipulated the bending moment and lateral force pressing the whisker against the sides of the follicle and the axial force pushing the whisker into the follicle by varying the compliance of the object during behavior. The behavioral responses suggest that mice use multiple variables (bending moment, axial force, lateral force) to extract radial object localization. Characterization of whisker mechanics revealed that whisker bending stiffness decreases gradually with distance from the face over five orders of magnitude. As a result, the relative amplitudes of different stress variables change dramatically with radial object distance. Our data suggest that mice use distance-dependent whisker mechanics to estimate radial object location using an algorithm that does not rely on precise control of whisking, is robust to variability in whisker forces, and is independent of object compliance and object movement. More generally, our data imply that mice can measure the amplitudes of forces in the sensory follicles for tactile sensation.

}, keywords = {Algorithms, Animals, Biological, Computer Simulation, Corneal Topography, Cues, Decision Making, Electron, Exploratory Behavior, Functional Laterality, Inbred C57BL, Male, Mice, Microscopy, Models, Physical Stimulation, Psychophysics, Scanning, Time Factors, Touch, Vibrissae}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.4316-12.2013}, author = {Pammer, Lorenz and O{\textquoteright}Connor, Daniel H and Hires, S Andrew and Clack, Nathan G and Huber, Daniel and Myers, Eugene W and Svoboda, Karel} } @article {6146, title = {Neural coding during active somatosensation revealed using illusory touch.}, journal = {Nature Neuroscience}, volume = {16}, year = {2013}, month = {2013 Jun 2}, pages = {958-65}, abstract = {

Active sensation requires the convergence of external stimuli with representations of body movements. We used mouse behavior, electrophysiology and optogenetics to dissect the temporal interactions among whisker movement, neural activity and sensation of touch. We photostimulated layer 4 activity in single barrels in a closed loop with whisking. Mimicking touch-related neural activity caused illusory perception of an object at a particular location, but scrambling the timing of the spikes over one whisking cycle (tens of milliseconds) did not abolish the illusion, indicating that knowledge of instantaneous whisker position is unnecessary for discriminating object locations. The illusions were induced only during bouts of directed whisking, when mice expected touch, and in the relevant barrel. Reducing activity biased behavior, consistent with a spike count code for object detection at a particular location. Our results show that mice integrate coding of touch with movement over timescales of a whisking bout to produce perception of active touch.

}, issn = {1546-1726}, doi = {10.1038/nn.3419}, author = {O{\textquoteright}Connor, Daniel H and Hires, S Andrew and Guo, Zengcai V and Li, Nuo and Yu, Jianing and Sun, Qian-Quan and Huber, Daniel and Svoboda, Karel} } @article {5200, title = {Automated tracking of whiskers in videos of head fixed rodents.}, journal = {PLoS Computational Biology}, volume = {8}, year = {2012}, month = {2012 Jul}, pages = {e1002591}, abstract = {

We have developed software for fully automated tracking of vibrissae (whiskers) in high-speed videos (\>500 Hz) of head-fixed, behaving rodents trimmed to a single row of whiskers. Performance was assessed against a manually curated dataset consisting of 1.32 million video frames comprising 4.5 million whisker traces. The current implementation detects whiskers with a recall of 99.998\% and identifies individual whiskers with 99.997\% accuracy. The average processing rate for these images was 8 Mpx/s/cpu (2.6 GHz Intel Core2, 2 GB RAM). This translates to 35 processed frames per second for a 640 px{\texttimes}352 px video of 4 whiskers. The speed and accuracy achieved enables quantitative behavioral studies where the analysis of millions of video frames is required. We used the software to analyze the evolving whisking strategies as mice learned a whisker-based detection task over the course of 6 days (8148 trials, 25 million frames) and measure the forces at the sensory follicle that most underlie haptic perception.

}, issn = {1553-7358}, doi = {10.1371/journal.pcbi.1002591}, author = {Clack, Nathan G and O{\textquoteright}Connor, Daniel H and Huber, Daniel and Petreanu, Leopoldo and Hires, Andrew and Peron, Simon and Svoboda, Karel and Myers, Eugene W} } @article {6294, title = {Nonlinear dendritic integration of sensory and motor input during an active sensing task.}, journal = {Nature}, volume = {492}, year = {2012}, month = {2012 Dec 13}, pages = {247-51}, abstract = {

Active dendrites provide neurons with powerful processing capabilities. However, little is known about the role of neuronal dendrites in behaviourally related circuit computations. Here we report that a novel global dendritic nonlinearity is involved in the integration of sensory and motor information within layer 5 pyramidal neurons during an active sensing behaviour. Layer 5 pyramidal neurons possess elaborate dendritic arborizations that receive functionally distinct inputs, each targeted to spatially separate regions. At the cellular level, coincident input from these segregated pathways initiates regenerative dendritic electrical events that produce bursts of action potential output and circuits featuring this powerful dendritic nonlinearity can implement computations based on input correlation. To examine this in vivo we recorded dendritic activity in layer 5 pyramidal neurons in the barrel cortex using two-photon calcium imaging in mice performing an object-localization task. Large-amplitude, global calcium signals were observed throughout the apical tuft dendrites when active touch occurred at particular object locations or whisker angles. Such global calcium signals are produced by dendritic plateau potentials that require both vibrissal sensory input and primary motor cortex activity. These data provide direct evidence of nonlinear dendritic processing of correlated sensory and motor information in the mammalian neocortex during active sensation.

}, keywords = {Animal, Animals, Behavior, Calcium, Dendrites, Inbred C57BL, Male, Mice, Motor Activity, Patch-Clamp Techniques, Pyramidal Cells, Sensation, Signal Transduction}, issn = {1476-4687}, doi = {10.1038/nature11601}, author = {Xu, Ning-long and Harnett, Mark T and Williams, Stephen R and Huber, Daniel and O{\textquoteright}Connor, Daniel H and Svoboda, Karel and Magee, Jeffrey C} } @article {4288, title = {Learning-related fine-scale specificity imaged in motor cortex circuits of behaving mice.}, journal = {Nature}, volume = {464}, year = {2010}, month = {2010 Apr 22}, pages = {1182-6}, abstract = {

Cortical neurons form specific circuits, but the functional structure of this microarchitecture and its relation to behaviour are poorly understood. Two-photon calcium imaging can monitor activity of spatially defined neuronal ensembles in the mammalian cortex. Here we applied this technique to the motor cortex of mice performing a choice behaviour. Head-fixed mice were trained to lick in response to one of two odours, and to withhold licking for the other odour. Mice routinely showed significant learning within the first behavioural session and across sessions. Microstimulation and trans-synaptic tracing identified two non-overlapping candidate tongue motor cortical areas. Inactivating either area impaired voluntary licking. Imaging in layer 2/3 showed neurons with diverse response types in both areas. Activity in approximately half of the imaged neurons distinguished trial types associated with different actions. Many neurons showed modulation coinciding with or preceding the action, consistent with their involvement in motor control. Neurons with different response types were spatially intermingled. Nearby neurons (within approximately 150 mum) showed pronounced coincident activity. These temporal correlations increased with learning within and across behavioural sessions, specifically for neuron pairs with similar response types. We propose that correlated activity in specific ensembles of functionally related neurons is a signature of learning-related circuit plasticity. Our findings reveal a fine-scale and dynamic organization of the frontal cortex that probably underlies flexible behaviour.

}, keywords = {Animal, Animals, Axonal Transport, Behavior, Chemical, Choice Behavior, Inbred C57BL, Learning, Male, Mice, Motor Cortex, Motor Neurons, Neural Pathways, Odors, Pyramidal Cells, Reward, Stimulation, Time Factors, Tongue}, issn = {1476-4687}, doi = {10.1038/nature08897}, author = {Komiyama, Takaki and Sato, Takashi R and O{\textquoteright}Connor, Daniel H and Zhang, Ying-Xin and Huber, Daniel and Hooks, Bryan M and Gabitto, Mariano and Svoboda, Karel} } @article {4289, title = {Neural activity in barrel cortex underlying vibrissa-based object localization in mice.}, journal = {Neuron}, volume = {67}, year = {2010}, month = {2010 Sep 23}, pages = {1048-61}, abstract = {

Classical studies have related the spiking of selected neocortical neurons to behavior, but little is known about activity sampled from the entire neural population. We recorded from neurons selected independent of spiking, using cell-attached recordings and two-photon calcium imaging, in the barrel cortex of mice performing an object localization task. Spike rates varied across neurons, from silence to \>60 Hz. Responses were diverse, with some neurons showing large increases in spike rate when whiskers contacted the object. Nearly half the neurons discriminated object location; a small fraction of neurons discriminated perfectly. More active neurons were more discriminative. Layer (L) 4 and L5 contained the highest fractions of discriminating neurons (\~{}63\% and 79\%, respectively), but a few L2/3 neurons were also highly discriminating. Approximately 13,000 spikes per activated barrel column were available to mice for decision making. Coding of object location in the barrel cortex is therefore highly redundant.

}, keywords = {Action Potentials, Afferent Pathways, Animal, Animals, Behavior, Biological, Brain Mapping, Calcium, Discrimination (Psychology), Inbred C57BL, Male, Mice, Models, Neurons, Physical Stimulation, ROC Curve, Somatosensory Cortex, Vibrissae}, issn = {1097-4199}, doi = {10.1016/j.neuron.2010.08.026}, author = {O{\textquoteright}Connor, Daniel H and Peron, Simon P and Huber, Daniel and Svoboda, Karel} } @article {2329, title = {Vibrissa-based object localization in head-fixed mice.}, journal = {The Journal of Neuroscience}, volume = {30}, year = {2010}, month = {2010 Feb 3}, pages = {1947-67}, abstract = {

Linking activity in specific cell types with perception, cognition, and action, requires quantitative behavioral experiments in genetic model systems such as the mouse. In head-fixed primates, the combination of precise stimulus control, monitoring of motor output, and physiological recordings over large numbers of trials are the foundation on which many conceptually rich and quantitative studies have been built. Choice-based, quantitative behavioral paradigms for head-fixed mice have not been described previously. Here, we report a somatosensory absolute object localization task for head-fixed mice. Mice actively used their mystacial vibrissae (whiskers) to sense the location of a vertical pole presented to one side of the head and reported with licking whether the pole was in a target (go) or a distracter (no-go) location. Mice performed hundreds of trials with high performance (\>90\% correct) and localized to \<0.95 mm (\<6 degrees of azimuthal angle). Learning occurred over 1-2 weeks and was observed both within and across sessions. Mice could perform object localization with single whiskers. Silencing barrel cortex abolished performance to chance levels. We measured whisker movement and shape for thousands of trials. Mice moved their whiskers in a highly directed, asymmetric manner, focusing on the target location. Translation of the base of the whiskers along the face contributed substantially to whisker movements. Mice tended to maximize contact with the go (rewarded) stimulus while minimizing contact with the no-go stimulus. We conjecture that this may amplify differences in evoked neural activity between trial types.

}, keywords = {Animals, Exploratory Behavior, Head Movements, Inbred C57BL, Mice, Movement, Physical, Restraint, Somatosensory Cortex, Space Perception, Touch, Vibrissae}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.3762-09.2010}, author = {O{\textquoteright}Connor, Daniel H and Clack, Nathan G and Huber, Daniel and Komiyama, Takaki and Myers, Eugene W and Svoboda, Karel} } @article {5249, title = {Reverse engineering the mouse brain.}, journal = {Nature}, volume = {461}, year = {2009}, month = {2009 Oct 15}, pages = {923-9}, abstract = {

Behaviour is governed by activity in highly structured neural circuits. Genetically targeted sensors and switches facilitate measurement and manipulation of activity in vivo, linking activity in defined nodes of neural circuits to behaviour. Because of access to specific cell types, these molecular tools will have the largest impact in genetic model systems such as the mouse. Emerging assays of mouse behaviour are beginning to rival those of behaving monkeys in terms of stimulus and behavioural control. We predict that the confluence of new behavioural and molecular tools in the mouse will reveal the logic of complex mammalian circuits.

}, keywords = {Action Potentials, Animal, Animals, Behavior, Brain, Mice, Neural Pathways, Somatosensory Cortex}, issn = {1476-4687}, doi = {10.1038/nature08539}, author = {O{\textquoteright}Connor, Daniel H and Huber, Daniel and Svoboda, Karel} } @article {4258, title = {Characterization and subcellular targeting of GCaMP-type genetically-encoded calcium indicators.}, journal = {PLoS One}, volume = {3}, year = {2008}, month = {2008 Mar 19}, pages = {e1796}, abstract = {

Genetically-encoded calcium indicators (GECIs) hold the promise of monitoring [Ca(2+)] in selected populations of neurons and in specific cellular compartments. Relating GECI fluorescence to neuronal activity requires quantitative characterization. We have characterized a promising new genetically-encoded calcium indicator-GCaMP2-in mammalian pyramidal neurons. Fluorescence changes in response to single action potentials (17+/-10\% DeltaF/F [mean+/-SD]) could be detected in some, but not all, neurons. Trains of high-frequency action potentials yielded robust responses (302+/-50\% for trains of 40 action potentials at 83 Hz). Responses were similar in acute brain slices from in utero electroporated mice, indicating that long-term expression did not interfere with GCaMP2 function. Membrane-targeted versions of GCaMP2 did not yield larger signals than their non-targeted counterparts. We further targeted GCaMP2 to dendritic spines to monitor Ca(2+) accumulations evoked by activation of synaptic NMDA receptors. We observed robust DeltaF/F responses (range: 37\%-264\%) to single spine uncaging stimuli that were correlated with NMDA receptor currents measured through a somatic patch pipette. One major drawback of GCaMP2 was its low baseline fluorescence. Our results show that GCaMP2 is improved from the previous versions of GCaMP and may be suited to detect bursts of high-frequency action potentials and synaptic currents in vivo.

}, keywords = {Action Potentials, Animals, Calcium, Hippocampus, Humans, Rats, Subcellular Fractions}, issn = {1932-6203}, doi = {10.1371/journal.pone.0001796}, author = {Mao, Tianyi and O{\textquoteright}Connor, Daniel H and Scheuss, Volker and Nakai, Junichi and Svoboda, Karel} }