Learning to cricket hunt by the laboratory mouse (Mus musculus): Skilled movements of the hands and mouth in cricket capture and consumption.

Although the mouse (Mus musculus) is preyed upon by many other species of animals, it is also a predator and will hunt and consume crickets. There has been no previous description of how mice learn to hunt and no report on the extent to which they use their hands and mouth to assist prey capture and these were the objectives of the present study. Mice given one cricket each day displayed decreasing hunt times over 25-days for three phases of a hunt: investigate, in which a mouse explored and periodically encounter a cricket and often bit at it; pursue, in which a mouse's approach remained focused on the cricket until it was captured; and consume, in which the cricket was handled, decapitated, its core eaten, with its shell discarded. Although visual and auditory cues may contribute to locating a cricket, the vibrissae appeared to provide guidance in pursuit and capture when the cricket and mouse were proximate. Cricket capture involved extensive collaborative use of the mouth and the hands and mice could initiate capture with either the mouth or hands. Handling to eat involved manipulating the cricket into a head-up, ventrum-in position for decapitation and selective eating of the core of the cricket. The results are discussed in relation to mouse learning of a complex natural behavior, the use of tactile cues in the species-specific behavior of predation, and the contributions of the hands and mouth to predation.

Cholinergic upregulation by optogenetic stimulation of nucleus basalis after photothrombotic stroke in forelimb somatosensory cortex improves endpoint and motor but not sensory control of skilled reaching in mice.

A network of cholinergic neurons in the basal forebrain innerve the forebrain and are proposed to contribute to a variety of functions including cortical plasticity, attention, and sensorimotor behavior. This study examined the contribution of the nucleus basalis cholinergic projection to the sensorimotor cortex on recovery on a skilled reach-to-eat task following photothrombotic stroke in the forelimb region of the somatosensory cortex. Mice were trained to perform a single pellet skilled reaching task and their pre and poststroke performance, from Day 4 to Day 28 poststroke, was assessed frame-by-frame by video analysis with endpoint, movement and sensorimotor integration measures. Somatosensory forelimb lesions produced impairments in endpoint and movement component measures of reaching and increased the incidence of fictive eating, a sensory impairment in mistaking a missed reach for a successful reach. Upregulated acetylcholine (ACh) release, as measured by local field potential recording, elicited via optogenetic stimulation of the nucleus basalis improved recovery of reaching and improved movement scores but did not affect sensorimotor integration impairment poststroke. The results show that the mouse cortical forelimb somatosensory region contributes to forelimb motor behavior and suggest that ACh upregulation could serve as an adjunct to behavioral therapy for acute treatment of stroke.

The temporal choreography of the yo-yo movement of getting spaghetti into the mouth by the head-fixed mouse.

There is debate over whether single-handed eating movements, reaching for food and withdrawing the hand to place the food in the mouth, originated in the primate lineage or whether they originated in phylogenetically-earlier Euarchontoglires. Most spontaneous hand use in eating by the laboratory mouse (Mus domestica) involves both hands, and a central question is the extent to which the movements are symmetric. Here we describe an asymmetry of spontaneous single hand use by the head-fixed mouse in making the yo-yo hand movement of removing and replacing a piece of pasta (spaghetti) in the mouth for eating. We also describe the problem/solution of placing into the mouth the end of a held item that protrudes at some distance from the hand. Pasta-eating proceeds in bouts, and a bout starts with raising the hands, which are holding a piece of pasta, to place one end of the pasta in the mouth for biting. A bout ends with lowering the hands, still holding the pasta stem, while the pasta morsel that has been bitten off is chewed. Hand-lowering after the pasta is removed from the mouth is slow, concurrent and symmetric, both when the pasta is held by both hands and when it is held in one hand. Hand-raising to place the pasta in the mouth is fast, consecutive and asymmetric, both when the pasta is held in both hands and when it is held in one hand. Frame-by-frame analyses of the video record combined with kinematic analyses show that a preferred single hand not only directs one end of the pasta to the mouth but also readjusts the trajectory of the pasta if it misses the mouth. The specialized use of a single hand by the mouse, even when the hands are bilaterally engaged, and the corrective asymmetric movements with which one hand adjusts the pasta's trajectory with the other hand playing a supporting role, is discussed in relation to the idea that hand preference, specialization, and dexterity have somatosensory and preprimate origins.

Data-driven analyses of motor impairments in animal models of neurological disorders.

Behavior provides important insights into neuronal processes. For example, analysis of reaching movements can give a reliable indication of the degree of impairment in neurological disorders such as stroke, Parkinson disease, or Huntington disease. The analysis of such movement abnormalities is notoriously difficult and requires a trained evaluator. Here, we show that a deep neural network is able to score behavioral impairments with expert accuracy in rodent models of stroke. The same network was also trained to successfully score movements in a variety of other behavioral tasks. The neural network also uncovered novel movement alterations related to stroke, which had higher predictive power of stroke volume than the movement components defined by human experts. Moreover, when the regression network was trained only on categorical information (control = 0; stroke = 1), it generated predictions with intermediate values between 0 and 1 that matched the human expert scores of stroke severity. The network thus offers a new data-driven approach to automatically derive ratings of motor impairments. Altogether, this network can provide a reliable neurological assessment and can assist the design of behavioral indices to diagnose and monitor neurological disorders.

A mouse's spontaneous eating repertoire aids performance on laboratory skilled reaching tasks: A motoric example of instinctual drift with an ethological description of the withdraw movements in freely-moving and head-fixed mice.

Rodents display a spontaneous "order-common" pattern of food eating: they pick up food using the mouth, sit on their haunches, and transfer the food to the hands for handling/chewing. The present study examines how this pattern of behaviour influences performance on "skilled-reaching" tasks, in which mice purchase food with a single hand. Here five types of withdraw movement, the retraction of the hand, in three reaching tasks: freely-moving single-pellet, head-fixed single-pellet, and head-fixed pasta-eating is described. The withdraw movement varied depending upon whether a reach was anticipatory, no food present, or was unsuccessful or successful with food present. Ease of withdraw is dependent upon the extent to which animals used order-common movements. For freely-moving mice, a hand-to-mouth movement was assisted by a mouth-to-hand movement and food transfer to the mouth depended upon a sitting posture and using the other hand to assist food holding, both order-common movements. In the head-fixed single-pellet task, with postural and head movements prevented, withdraw was made with difficulty and tongue protrude movements assisted food transfer to the mouth once the hand reached the mouth. Only when a head-fixed mouse made a bilateral hand-to-mouth movement, a component of order-common eating, was the withdraw movement made with ease. The results are discussed with respect to the use of order-common movements in skilled-reaching tasks and with respect to the optimal design of tasks used to assess rodent skilled hand movement.

Tongue protrusions modify the syntax of skilled reaching for food by the mouse: Evidence for flexibility in action selection and shared hand/mouth central modulation of action.

Skilled reaching for food by the laboratory mouse has the appearance of an action pattern with a distinctive syntax in which ten submovements occur in an orderly sequence. A mouse locates the food by Sniffing, Lifts, Aims, Advances, and Shapes the hand to Pronate it over a food target that it Grasps, Retracts, and Withdraws to Release to its mouth for eating. The structure of the individual actions in the chain are useful for the study of the mouse motor system and contribute to the use of the mouse as a model of human neurological conditions. The present study describes tongue protrusions that modify the syntax of reaching by occurring at the point of the reaching action at which the hand is at the Aim position. Tongue protrusions were not related to reaching success and were not influenced by training. Tongue protrusions were more likely to occur in the presence of a food target than with reaches made when food was absent. There were vast individual differences; some mice always make tongue protrusions while other mice never make tongue protrusions. That the syntax of reaching can be altered by the insertion of a surrogate (co-occurring) movement adds to a growing body of evidence that skilled reaching is assembled from a number of relatively independent actions, each with its own sensorimotor control that are subject to central modulation. That tongue and hand reaching movements can co-occur suggests a privileged relation between neural mechanisms that control movements of the tongue and hand.

The syntactic organization of pasta-eating and the structure of reach movements in the head-fixed mouse.

Mice are adept in the use of their hands for activities such as feeding, which has led to their use in investigations of the neural basis of skilled-movements. We describe the syntactic organization of pasta-eating and the structure of hand movements used for pasta manipulation by the head-fixed mouse. An ethogram of mice consuming pieces of spaghetti reveals that they eat in bite/chew bouts. A bout begins with pasta lifted to the mouth and then manipulated with hand movements into a preferred orientation for biting. Manipulation involves many hand release-reach movements, each with a similar structure. A hand is advanced from a digit closed and flexed (collect) position to a digit extended and open position (overgrasp) and then to a digit closed and flexed (grasp) position. Reach distance, hand shaping, and grasp patterns featuring precision grasps or whole hand grasps are related. To bite, mice display hand preference and asymmetric grasps; one hand (guide grasp) directs food into the mouth and the other stabilizes the pasta for biting. When chewing after biting, the hands hold the pasta in a symmetric resting position. Pasta-eating is organized and features structured hand movements and so lends itself to the neural investigation of skilled-movements.

The Adverse Effects of Auditory Stress on Mouse Uterus Receptivity and Behaviour.

Stress during gestation has harmful effects on pregnancy outcome and can lead to spontaneous abortion. Few studies, however, have addressed the impact of gestational stress, particularly auditory stress, on behavioural performance and pregnancy outcome in mice. This study aimed to examine the effect of two types of gestational stress on uterus receptivity and behavioural performance. Pregnant C57BL/6 mice were randomly assigned to either auditory or physical stress conditions or a control condition from gestational days 12-16. The auditory stress regimen used loud 3000 Hz tone, while the physical stressor consisted of restraint and exposure to an elevated platform. Three behavioural tests were performed in the dams after weaning. Uterine receptivity was investigated by counting the number of sites of implantation and fetal resorption. Also, the offspring survival rates during the early postnatal period were calculated. Auditory stress caused an increase in anxiety-like behaviour, reduced time spent exploring new object/environment, and reduced balance when compared to the physical stress and control groups. Auditory stress also caused higher rates of resorbed embryos and reduction of litter size. Our results suggest that the adverse effect of noise stress is stronger than physical stress for both uterus receptivity and behavioural performance of the dams.

Organization of the reach and grasp in head-fixed vs freely-moving mice provides support for multiple motor channel theory of neocortical organization.

Multiple motor channel (MMC) theory of neocortical organization proposes that complex movements, such as reaching for a food item to eat, are produced by the coordinated action of separate neural channels. For example, the human reach-to-grasp act is mediated by two visuo-parieto-motor cortex channels, one for the reach and one for the grasp. The present analysis asked whether there is a similar organization of reach-and-grasp movements in the mouse. The reach-to-eat movements of the same mice were examined from high-shutter speed, frame-by-frame video analysis in three tasks in which the mice obtained equivalent success scores: when freely-moving reaching for food pellets, when head-fixed reaching for food pellets, and when head-fixed reaching for pieces of pasta. To reach, the mice used egocentric cues to vary upper arm movements in a task-appropriate manner to place an open hand on the food or to locate the food using a "touch-release-grasp" strategy. Although mice could not hand-shape offline when reaching, they could hand-shape using online touch-related cues from the mouth to manipulate the food at the mouth. That the reach can be performed offline in relation to egocentric cues whereas hand shaping for the grasp requires online cues supports the idea that for the mouse, as for primates, the reach and grasp are separate acts. The results are further discussed in relation to the use of the head-fixed behavioral procedure to identify the independent neural substrates of the reach and the grasp using mesoscale stimulation/imaging methods.