The elevated plus maze is a well-established behavioral paradigm that measures anxiety through passive observation. It uses the mouse's innate tendency to spend time in enclosed spaces and their innate, unconditioned fear of open ones. A mouse is placed in the center of a maze that has two "closed" (walled) arms and two "open" arms. The time the mouse spends in the closed arms in compared to the time it spends in the open arms and this comparison serves as a measure of "anxiety" (the greater the ratio of closed-to-open, the greater the "anxiety" of the animal). 

The elevated zero maze can be thought of as a modification of the classic elevated plus maze. Like the plus maze, the zero maze measures "anxiety" (as opposed to exploration) by comparing the time spent by the mouse in the open versus closed sections. Due to its circular design, however, it does not have the ambiguous center area that the plus maze does. This allows for a more straightforward analysis of the mouse behavior. 

The forced swim test (also known as the Porsolt forced swim test) is used to measure depression-like behavior in mice. It is also sometimes referred to as the "despair test" for this reason. Mice are placed in a cylindrical container filled with water. The behavior of the mouse is recorded and then analyzed. "Floating" (i.e. when a mouse is immobile with its head above water) is said to indicate "helplessness" and is thus used as a measure of depression-like behavior (particularly because the test has been shown to be sensitive to the effects of depression-related drugs like SSRIs). This test must be conducted carefully as there is a risk of hypothermia. 

The light/dark box test is a commonly used test of anxiety-like behavior in mice (and other rodents). It is designed around a mouse's innate approach/avoidance conflict: the conflict between a mouse's drive to explore novel areas (approach) and aversion to brightly lit, open spaces (avoidance).  The test is done in an apparatus that consists of a "safe," dark compartment and an aversive, brightly lit compartment, both of which are connected via a small opening between them. In most experiments, the mouse is placed in the bright compartment and then allowed to explore the entire apparatus freely. The time the mouse spends in both compartments is measured as well at the mouse's latency to enter the dark compartment and the number of times it transitions between the two compartments. In addition, distance traveled (total and by compartment) is also measured. Traditionally, mice that are quicker to enter the dark compartment and spend less time in the bright compartment are thought of as being more "anxious," and the number of transitions between compartments has been used as an index of activity/exploration. Previous research has found that this test is sensitive to the effects of a variety of anxiolytic compounds.

The open field test is a well-established paradigm used to investigate anxiety-related activity compared to exploration-related activity. The time the mouse spends near the walls of the arena is compared to the time it spends in the center of the arena. Traditionally, mice that spend more time near the walls are thought to be more "anxious" than those who spend more time in the center. Time spent in the center and latency to enter the center are thought of as measures of exploration and boldness. Often times, however, the only measure analyzed by experimenters is the total distance traveled by the mouse. This often leads to some confounding of locomotion and exploration. To address this, experimenters may choose to examine the specific behavior of the mouse as it moves (rearing, nose-poking, hunched posture, etc.). Other factors experimenters may wish to consider before running an open field test are the potential effects of social isolation (from cage-mates) and choice (to enter a novel arena).

The tail suspension test is used to measure escape-oriented behaviors in mice suspended by their tails with tape. It is often used by investigators interested in depression related behaviors (particularly because the test has been shown to be sensitive to the effects of depression-related drugs like SSRIs). Mice are suspended by their tails for several minutes in a position where they cannot escape or hold onto nearby objects or surfaces. Immobility is used as a measure of depression-like behavior. The tail suspension test is sometimes considered a safer alternative to the forced swim test as it does not have the associated risk of hypothermia (although the tasks do have their differences). 

The Sucrose Preference Test  is a reward-based test used to investigate anhedonia in rodents. Anhedonia is the inability to feel pleasure in pleasurable activities or having a lack of interest in rewarding stimuli. In the Sucrose Preference Test Apparatus, the subjects are given access to two water modified serological pipettes (~25mL), one filled with 2% sucrose solution, which serves as the rewarding stimuli and the other with regular water. Rodents  naturally avidly consume sweet food when given the option between that and water. When exposed to stress-based models of depression (chronic mild physical stress, chronic social defeat, etc.), rodents fail to drink more sucrose solution than regular water.  Treatment with antidepressants has been shown to restore the preference for sucrose.

SR-LAB-Startle Response System

Measuring the startle response and its plasticity is a powerful way to examine the neural control of behavior. The startle response consists of involuntary contractions of the animal’s muscles in response to a sudden, intense stimulus. Startle response plasticity can serve as an operational measure to study the neural substrates underlying it. One aspect of startle response plasticity that is often examined is prepulse inhibition (PPI). PPI is a neurological phenomenon in which a weaker prestimulus (the prepulse) presented before the more intense starling stimulus (pulse), causes the organism to inhibit all or some of its startle response (to the pulse).

Conditioned place preference is used to test the motivation effects of events and experiences. During training, a mouse is placed in a chamber and exposed to a positive event or stimulus (food, drug administration, social interaction, etc.). In the other chamber, mice are exposed to a control event/stimulus.  Later, during testing, mice are placed in a neutral chamber and given access to the two chambers from training. The time spent in each chamber is assessed and used to measure whether or not the association formed in training resulted in a conditioned preference for the training chamber where the positive event/stimulus was presented. In order for the chambers to be easily differentiated by the mouse, unique environmental cues (CS) are present in both chambers (wallpaper, flooring, odor, etc.). As such, place preference arises from the CS (chamber/chamber "decor") - US (positive stimulus) association formed during training. Traditional conditioned place preference arenas are typically arranged so that the neutral chamber is between the two other chambers, and so that the mouse must pass through the neutral chamber in order to move between the other two chambers. This may result in confounds or scoring difficulty resulting from the time the mouse spends in the neutral chamber. Our conditioned place preference arena is set up so that the mouse may pass directly from one testing chamber to the other or through the neutral chamber. Access to any chamber can be restricted using a removable door; this allows for greater control by the experimenter. 

Along with the previously described conditioned place preference paradigm, variations may be conducted, including some that measure conditioned place aversion; extinction and reinstatement of the CS (chamber/chamber "decor") can also be measured. In addition, the chamber to be conditioned can be chosen in a biased (based on which chamber the mouse least "prefers" during free exploration) or unbiased (chosen by the researcher randomly).

FreezeScan System

Fear Conditioning paradigms allow investigators to examine both an organism’s memory of aversive events as well as their associated sensory and motor abilities. It, along with taste aversion, is one of the only types of learning/memory that can be observed after only a single trial. Conditioning is measured by documenting and comparing the bouts of ‘freezing’ behavior (lack of any movement other than respiration) a mouse displays at different times during the procedure. Cued fear conditioning measures a mouse’s memory of a discriminative stimulus previously used to cue an aversive event/stimulus (electric shock), while contextual fear conditioning measures a mouse’s memory of a context associated with an aversive event/stimulus. Fear conditioning paradigms require minimal equipment and are easily scored.

Optical Activity Monitor

Mice are placed into specially designed home cages with infrared photobeams to record locomotor activity. The configuration of the photobeams allows for the precise tracking of the animals' activity and generates a record of movement across the X, Y, and Z axes. This allows for the continuous monitoring of mouse behavior to compare differences across groups, strains, sexes, etc. Mice live in the modified home cages for a week and are provided with ad libitum food and water. A regular light-dark cycle allows for behavior to be compared across circadian periods. 

Mice in their home cage are placed inside a faraday cage under a controlled light/dark cycle and EEG/EMG activity recorded on implanted electrodes is continuously monitored through a multichannel tethered amplifier system. General activity levels and sleep state are scored based on the combined EEG and EMG activity across all channels.

Figure from Mang & Franken (2012)

The Barnes maze is a well-established paradigm used to study and measure spatial learning and memory. It is an alternative to the Morris Water Maze, which may not always be appropriate for use with all mouse strains due to its reliance on intact motor function and stamina (for swimming), and the additional stress involved from being a swimming task. Barnes maze consists of a circular table with several holes that can be blocked, baited, or equipped with an "escape box." In the classic paradigm, mice are placed on the maze (which is an innately "scary" open space) and they are recorded as they try to find the hole that contains the escape box (a "safe," enclosed compartment). External, spatial cues are placed on the walls of the room the maze is in to aid in this process. The mouse is placed on the maze in an opaque start box which makes the use of any egocentric spatial cues impossible. The latency to find the escape box and performance on a later probe test serve as measures of spatial memory in this task. 

The T-maze is an apparatus used for various learning tasks. It can be used as a passive observation task that measures various types of memory. A mouse is placed in the "starting" arm of the maze, facing away from the center. The entries into the other arms as well as number of arm alternations are recorded and used as a measure of working memory. In a slightly more complicated task, spatial memory can be assessed. Here, a mouse is placed in the "starting" arm of the maze with access to only one of the two other arms (both of which are marked by external, spatial cues). The mouse is allowed to explore freely. The next day, the mouse is again placed in the starting arm, but now has access to both of the other arms. The amount of time the mouse spends in the "novel" (previously blocked) arm is compared to time spent in the familiar arm and used as a measure of spatial memory. The T-maze can also be used for two-alternative choice paradigms with the addition of arm-baiting. 

The Y-maze can be used for all of the same tasks as the T-maze, but allows for the mouse to see both of the choice arms (and whatever they may contain) when standing in the center of the maze.

The balance beam is a narrow ‘walking bridge’ for mice to walk across to test balance and coordination. The beam sits between two elevated platforms, one of which is a covered end box that the mice are enticed to travel towards. Interchangeable beams (6, 12, 24, and 48mm) can be used in thinner and thinner intervals to manipulate the difficulty of the task, and the beam can be placed at an incline/decline if so desired. Latency to cross the center 80cm of the beam and the number of hind limb foot-slips are recorded for each mouse.

The DigiGait uses ventral plane videography instrumentation for gait analysis in laboratory animals. Ventral Plane Imaging (VPI) Technology continuously images the underside of the animals walking atop of the patented motorized transparent treadmill belt, generating “digital paw prints” and dynamic gait signals. These dynamic gait signals, generated for each of the 4 limbs, describe the posture and kinematics of the animals that reflect strength, balance, and coordination. The DigiGait can be used to record voluntary and treadmill walking over a range of walking and running speeds. Gait analysis is then performed reporting over 30 metrics of posture and locomotion.

The grip strength meter allows the study of neuromuscular functions in rodents by determining the maximum force displayed by an animal. Different attachments and protocols allow for the measurement of grip strength from different limbs. As grip strength is measured in gram force units, grip strength as a measurement can be normalized to each animals body weight (in grams). 

The Rotarod test is used to assess motor function (balance, endurance, grip strength, and motor coordination). Mice are placed on an elevated, rotating rod. Latency to fall is recorded for each mouse and used as a measure of motor function. The rod can either be made to rotate at a fixed speed or made to accelerate over time/trials. 

The NOR task is used to measure object memory using a task that takes advantage of a mouse's innate tendency to explore novel objects in their environment. After habituation, mice are placed in the NOR arenas along with two identical objects. They are allowed to explore freely and their behavior is recorded. 24 hours later, mice are again placed in the NOR arenas with two objects, but one of those objects is now novel. Mice are, again, allowed to explore freely and their behavior is recorded. The time spent exploring the novel object is compared to the time spent exploring the familiar object to assess object recognition memory. This procedure can be carried out in a way that is hippocampus independent (as detailed in Oliveira et al., 2015) if needed. 

The SOR task is used to measure spatial learning and memory using a task that takes advantage of a mouse's innate tendency to explore novel objects in their environment. After habituation, mice are placed in the SOR arenas along with either two identical OR three different objects. There is also a symbolic spatial cue on one wall of each arena to serve as a spatial landmark or reference point. They are allowed to explore freely and their behavior is recorded. 24 hours later, mice are again placed in the SOR arenas with the same objects, but one of those objects is now in a novel location. Mice are, again, allowed to explore freely and their behavior is recorded. The time spent exploring the moved object is compared to the time spent exploring the unmoved objects to assess the mouse's spatial memory.

All paradigms are done using either a 9-Hole Operant Box OR the Bussey-Saksida Mouse Touch Screen Chamber (both with Liquid Reward).

Autoshaping/Response Acquisition

_{Note: Autoshaping is not a form of operant conditioning, but can be used to teach an operant behavior.}

Autoshaping, conceptually, is an example of a complex behavioral reaction controlled by the steps of classical conditioning: the pairing of a conditioned stimulus (CS) and unconditioned stimulus (US) regardless of the actions of the subject. The best example of autoshaping comes from work done with pigeons: if a lighted key always turns on before a food reward is delivered, the pigeon will begin to respond to the lit key as it naturally does to the food reward, by pecking it. In this case, the key-pecking behavior has been taught through the means of classical conditioning alone. The sign-tracking (see PCA, below) of the lit-key results in responding directed to it. Because this natural responding (pecking) is also the desired operant response to a lit key, the pigeon has now acquired the response necessary to earn a reward in an operant conditioning procedure. Autoshaping in a mouse is much less straightforward, especially in a 9-hole operant chamber where sign-tracking is often illustrated by the mouse simply orienting to the hole light or moving close to it, rather than interacting with the hole itself. Too many presentations under these response-independent conditions can actually make response acquisition much more difficult. In addition, there are strain and sex differences in the amount that mice sign-track (rather than goal-track)(see Dickson et al., 2015). 

Response acquisition to nose-poking in a hole-equipped operant chamber has been shown previously by Baron & Meltzer (2001) in a method adapted from one in rats (Byrne et al., 1997). This procedure results in rapid response-acquisition (two days). 

Pavlovian Conditioned Approach (PCA)

_{Note: PCA is not actually a form of operant conditioning (although is can result in response acquisition).}

Pavlovian conditioned approach is a paradigm that assess Pavlovian sign-tracking: an established model of compulsiveness in addictive behavior (in humans). In mice, this is assessed through repeated pairings of a conditioned stimulus (CS) with the appetitive reward (the US). In a 9-hole operant chamber, the CS is the illumination of one of the nose-poke response holes (it is worth noting that this differs in form and mechanically from the CS in a lever-equipped operant chamber, most used in PCA, which is the insertion of the lever into the operant chamber). This pairing leads to the classical conditioning of sign-tracking conditioned response (ST CR), CS-directed approach, and goal-tracking conditioned response (GT CR), approach to the reward receptacle. Sign-tracking attributes incentive salience to reward-related cues which is thought to contribute to increased addiction vulnerability. Sign-tracking is also associated with impulsivity and cue-induced reinstatement of drug-seeking behavior. 

In some PCA paradigms (typically those involving a lever-equipped operant chamber) spontaneous response acquisition is observed. 

Basic Schedules of Reinforcement: Fixed Ratio (FR)

Fixed ratio schedules of reinforcement are those in which there is a fixed number of responses by the mouse required to earn a reward. Fixed ratio schedules result in high, steady responding and are best used when a new behavior is being learned. They typically lead to a brief pause in responding after reinforcement after which responding quickly resumes (usually in a "burst"). The acquisition of a fixed ratio schedule can be used to assess basic reward-driven learning.

Basic Schedules of Reinforcement: Variable Ratio (VR)

Variable ratio schedules of reinforcement are those in which a reward is delivered, on average, after a certain number of responses. For example, a variable ratio schedule of 10 would indicate that, on average, a reward is delivered after 10 responses, but the exact number of responses before a reward is delivered will vary on a trial-by-trial basis. For the mouse, the delivery of the reward is unpredictable. Variable ratio schedules result in high, steady, and long-lasting responding, making them best suited to maintaining previously learned behaviors. 

Motivation: Progressive Ratio (PR)

Progressive ratio schedules of reinforcement are those in which the number of responses required increases in an arithmetic sequence (i.e. 1, 2, 4, 8, 16, etc.). The response requirement can increase on every trial or after a certain (fixed) number of trials. The last trial where the ratio was completed and reinforcement delivered is defined as an individual mouse's "breakpoint." Breakpoints can be compared across mice, condition, strain, group, etc. to compare the (maintenance of) motivation to work for rewards. 

Five-Choice Serial-Reaction Time Task (5-CSRTT)

The 5-CSRTT is used to assess attention in mice and was designed to be a rodent version of the human Continuous Performance Task (CPT): a task that measures sustained and selective attention used to assess executive functioning. The mouse 5-CSRTT requires that a mouse learns to respond to the illumination of a response hole with a nose-poke. One of the nine response holes is briefly illuminated and the mouse must identify which hole was illuminated and respond to that hole with a nose poke. The shorter the illumination duration, the more difficult the task (as it requires greater attention to be paid). In addition, between trials there is an inter trial interval (ITI) during which the mouse must inhibit responding. The different kinds of responses/errors that the mouse can make in this task allow for separate measures of attention, impulsivity, and reaction time, which parallels the human CPT. This task is often used with mouse models of Schizophrenia, Alzheimer's, and Attention Deficit Disorders (among others). 

Five-Choice Continuous Performance Task (5C-CPT)

The 5C-CPT is an elaboration of the 5-CSRTT that more closely models the task parameters of the human CPT. In the 5-CSRTT, mice are trained to respond to a signal stimulus: the light that could appear at any of five locations (holes), which is consistent with the CPT. Incorrect responses (to a hole not illuminated) are said to be analogous to "false alarms" in the CPT. However, in the 5-CSRTT there is no way to measure "correct rejections," the contrary measure to false alarms; there are no non-signal trials presented. The 5C-CPT incorporates non-signal trials by requiring mice to inhibit responding on trials where lights appear in all five locations. 

Two-Choice Paired/Visual Discrimination Reversal (PD--Touchscreen ONLY)

The task involves learning that one of two shapes displayed simultaneously on the screen is correct. Touching the correct stimuli (S+) will be rewarded with food. Touching the incorrect stimuli (S-) will be punished with a timeout. Once the task has been learned, the stimuli are reversed so that the S+ stimuli now becomes the S- stimuli and vice versa. This reversal learning requires inhibition of prepotent responses and is known to be dependent on the prefrontal cortex.

Paired-Associate Learning Task (PAL--Touchscreen ONLY)

In humans a similar task has proved to be highly effective for the early detection of Alzheimer's disease (AD). A 1995 study using volunteers who thought they had memory issues [named the questionable dementia (QD) group] found that CANTAB PAL could discriminate who had AD at an early stage.

Location Discrimination (LD--Touchscreen ONLY)

The rodents are required to discriminate between two white squares on the screen. Responses to squares on one side of the screen will be rewarded, while responses on the other side of the screen will be punished with a time out period. The distance between the two squares is varied from trial to trial. Animals with lesions in the dorsal hippocampus were impaired when the locations were close together, but not when they were far apart. Once 7 out of 8 trials are responded to correctly, the correct side is reversed, adding a reversal learning component. It is sensitive to hippocampal lesions and associated with glutamate receptor regulation and signaling.

The three-chamber test is used to measure a mouse's sociability and interest in social novelty. Typically, mice prefer to spend time with other rodents (rather than alone) and investigate mice they do not recognize. In this task, mice go through a series of phases where their behavior is measured. First, they are placed in the center chamber and allowed to freely explore this chamber as well as the left and the right (both of which are empty). Next, mice can be put through a variety of tasks where they are placed in the center chamber and the left or right chamber contain either a mouse (novel or familiar) or an object (novel or familiar). In any of these variations, the subject mouse's behavior is recorded and time spent interacting or exploring the contents of the left or right chambers (mouse or object) is measured. Below is one example of a possible task set for this test:

_{Stanford Behavioral and Functional Neuroscience Laboratory}

Sociability and social interest are scored using measures of sniffing and time spent in chamber (left, right, or center). "Normal" mice tend to socialize and spend more time in a compartment containing a mouse than an object. An absence of this pattern of behavior indicates a social deficit in the subject mouse. 

The tube dominance task allows for the investigation of social hierarchy. It is a task that induces a social conflict to measure how mice react and which mouse will "win" in this situation. Dominance asserted in the tube task that results in winning has been correlated with "winning" in other such situations. The tube task can be used to measure dominance and submission between a single pair of mice, or can be used to fully "map out" the social ranking of an entire mouse group. During training, a mouse is allowed to run through the entire tube (and in some procedures: reach a food reward on the other side). On the testing day, two mice are put into the tube (which now has a divider in the center), one from each end. Once both mice reach the center divider, it is removed and the confrontation begins. The confrontation ends when one mouse forces the other out of the tube (all four feet out). The mouse remaining in the tube is declared the winner. 

A variation of the conditioned place preference paradigm (see main entry under "Classical Conditioning") can be carried out to assess a mouse's preference for social interaction. Here, a mouse is conditioned to associate one of the chambers with social interaction during training (by spending time in one of the choice chambers with another mouse). In testing, the preference for the socially conditioned chamber compared to the other (control) chamber is assessed. The relative reinforcement of social interaction can also be compared by having one chamber be associated with social interaction and one with another appetitive stimulus/event (e.g. a food reward).

The NCBC offers a standard housing room within the Core area of the barrier facility. Housing animals in this room minimizes the amount of transport required to move mice to and from the experimental rooms, reducing additional stress from transport. This housing room has a standard (per the greater OAR facility) housing rack with ventilation and a watering system. The housing room operates on a light cycle with lights ON at 900 and lights OFF at 2100. Investigators are responsible for all animal husbandry if housing mice in this room. 

The NCBC offers a housing room within the Core area of the barrier facility with an inverted light cycle. Housing animals in this room minimizes the amount of transport required to move mice to and from the experimental rooms, reducing additional stress from transport, and allows experimenters to run tests during the mouse's dark phase. This housing room has a standard (per the greater OAR facility) housing rack with ventilation and a watering system. The housing room operates on a light cycle with lights OFF at 900 and lights ON at 2100. Investigators are responsible for all animal husbandry if housing mice in this room.

The fully functional surgical suite contains two high precision Kopf mouse stereotactic instruments with accompanying isoflurane vaporizers / scavengers, microdrills, and injection pumps. One stereotaxic is equipped with dual ultra precise stereotaxic manipulators (Kopf Model 962) allowing simultaneous bilateral injections or cannula implantations. The other is equipped with a digital readout of stereotaxic position (Kopf Model 940) and a stereomicroscope.

The surgical suite also includes a perfusion/dissection hood equipped with a SomnoSuite low flow isoflurane vaporizer and perfusion pump.

The NCBC has a high performance Windows 10 workstation for analysis of large imaging datasets. The computer has an installation of Bitplane Imaris as well as Matlab, Python, Fiji, and Leica LAS X Core Offline. The workstation "specs" are:

• CPU: Dual 3.2 GHz 8-Core Xeon, 25 MB cache
• RAM: 512 GB
• GPU: NVIDIA Quadro P6000 24 GB
• Storage: 4 x 1 TB SSD RAID 0

Imaris is image analysis software developed by Bitplane that is specialized for rendering and analyzing multidimensional datasets, including those acquired on our lightsheet and confocal microscopes. It has a variety of sophisticated algorithms for measuring and quantifying co-localization of fluorophores in 3D; performing automated, semi-automated, or manual segmentation of cell structure (including neural processes); and rendering animations of complex imaging datasets. 

The NCBC currently has the following Imaris modules available for use: Imaris Stitcher, Imaris FilamentTracer, and ImarisColoc (colocalization). Imaris Stitcher allows for the precise and accurate stitching of multiple image tiles in XYZ. Imaris FilamentTracer can be used to automatically detect neurons and other filament-like structures in 2D, 3D, and 4D. ImarisColoc allows the user to quantify and document co-distribution of multiple stained biological components. 

See Imaris, Imaris Stitcher, Imaris FilamentTracer, and ImarisColoc to learn more.

The NCBC also has a Windows 10 workstation for video analysis of behavioral data using Ethovision XT or Freezescan software. 

Ethovision XT

Ethovision is a software program developed by Noldus you can use to perform experiments where the tracking of the mouse's location and/or behavior is necessary. It can be used with "live" or prerecorded video to measure the behavior, movement, and/or activity of any animal. The user defines the task parameters, defines the task arena and designates any focal areas, sets up the use of any accessories (i.e. optogenetics), and sets the detection parameters for tracking the subject mice. As such, it is an ideal program to use in tasks where the measurements of interest include: frequency of behavior, time spent in a set location, orientation towards, etc. Ethovision can also be used in optogenetics experiments (or others), allowing users to set the onset of the laser to occur when a certain behavior/movement/mouse location is detected. 

Learn more by visiting the official Ethovision site.

FreezeScan

FreezeScan is a software program developed by CleverSys that can automatically detect freezing in Fear (Threat) Conditioning experiments. It can be used with "live" or prerecorded video and eliminates the possible confounds that arise from manual scoring. The user defines the task parameters as well as the arena that is to be tracked for mouse freezing. Learn more by visiting the official FreezeScan site.