"On-line" monitoring of jaw movements in the pigeon

Peripheral Motor Dynamics of Song Production in the Zebra Finch

Singing behavior in songbirds is a model system for motor control of learned behavior. The target organs of its central motor programs are the various muscle systems involved in sound generation. Investigation of these peripheral motor mechanisms of song production is the first step toward an understanding of how different motor systems are coordinated. Here we review physiological studies of all major motor systems that are involved in song production and modification in the zebra finch (Taeniopygia guttata). Acoustic syllables of zebra finch song are produced by a characteristic air sac pressure pattern. Electromyographic (EMG) and sonomicrometric recording of expiratory muscle activity reveals that respiratory motor control is tightly coordinated with syringeal gating of airflow. Recordings of bronchial airflow demonstrate that most of the song syllables are composed of simultaneous independent contributions from the two sides of the syrinx. Sounds generated in the syrinx can be modified by the resonance properties of the upper vocal tract. Tracheal length affects resonance, but dynamic changes of tracheal length are unlikely to make a substantial contribution to sound modification. However, beak movements during song contribute to sound modification and, possibly, affect the vibratory behavior of the labia. Rapid beak aperture changes were associated with nonlinear transitions in the acoustic structure of individual syllables. The synergy between respiratory and syringeal motor systems, and the unique bilateral, simultaneous, and independent sound production, combined with dynamic modification of the acoustic structure of song, make the zebra finch an excellent model system for exploring mechanisms of sensorimotor integration underlying a complex learned behavior.

Squeaking with a sliding joint: mechanics and motor control of sound production in palinurid lobsters

The origin of arthropod sound-producing morphology typically involves modification of two translating body surfaces, such as the legs and thorax. In an unusual structural rearrangement, I show that one lineage of palinurid lobsters lost an antennal joint articulation, which transformed this joint from moving with one degree of freedom into a sliding joint with multiple degrees of freedom. With this sliding joint, `stick-and-slip' sounds are produced by rubbing the base of each antenna against the antennular plate. To understand the musculo-skeletal changes that occurred during the origin and evolutionary variation of this sound-producing mechanism, I examined joint morphology and antennal muscle anatomy across sound-producing and non-sound-producing palinurids. Plectrum movement and antennal muscle activity were measured in a sound-producing species, Panulirus argus. The promotor muscle pulls the plectrum over the file during sound-producing and non-sound-producing movements; a higher intensity of muscle activity is associated with sound production. The promotor muscle is larger and attaches more medially in sound-producing palinurids than in non-sound producers. In Panulirus argus, each shingle on the file has an additional ridge; in Palinurus elephas, the shingle surfaces are smooth. These differences in shingle surface features suggest variation in the stick-and-slip properties of the system. Translational motion permitted by the sliding joint is necessary for sound production; hence, the construction of a sliding joint is a key modification in the origin of this sound-producing mechanism.

Effects of primary reinforcement on pigeons' initial-link responding under a concurrent chains schedule with nondifferntial terminal links

The effect of primary reinforcement on initial-link responding under concurrent-chains schedules with nondifferential terminal links was assessed in 12 pigeons. The iniitial and terminal links were variable-interval schedules (always the same for both alternatives). The positions (left or right key) of the initial-link stimuli (red or green) were randomized while the correlation between color and food amount remained constant within each condition. The terminal-link stimuli were always presented on the center key. Except in two control groups and conditions, the terminal-link stimuli were the same color (nondifferential, blue or yellow). Over six conditions, the differences in food amont and the durations of the initial- and terminal-link schedules were manipulated. In 57 of 60 cases, birds generated choice proportions above .50 in favor of the initial-link stimlus that was correlated with the larger reinforcer. There was some indication that preference increased with shortened terminal-link durations. Because the terminal-link stimuli were nondifferential, differential responding in the initial links cannot be explained easily by conditioned reinforcement represented by the terminal-link stimuli. Thus, primiary reinforcement has a direct effect on initial-link responding in concurrent-chains schedules.

Eye-movement recording in freely moving animals

A new method is described for precise recording of eye movements in freely moving animals using Hall-effect devices. This inexpensive system, of small size and low weight, allows the analysis of horizontal and vertical components of saccadic eye movements, optokinetic nystagmus, slow tracking movements, eye vergence, etc., in unrestrained animals. A set of Hall-effect devices mounted in the skull is used to sense variations in the position of high-power miniature magnets fixed to the eye sclera. The output of the Hall-effect devices is amplified by operational amplifiers and collected through an analog-to-digital converter to be displayed on-line in a personal computer and stored for later analysis by specific software. Some examples of simultaneous body- and eye-movement recordings obtained in freely moving goldfish in different experimental situations are presented. This method would be useful in the recording of eye and gaze movements under natural conditions and for behavioural studies in freely moving animals.

A method for measuring eye movements using Hall-effect devices

A system for precise recording of eye position and movements in laboratory animals, by means of Hall-effect devices, is described. The system, useful in neurophysiological and neurobehavioral studies, allows the analysis of saccadic eye movements, optokinetic- and vestibular-induced nystagmus, slow tracking movements, eye vergences, and so forth. This small, light-weight, and inexpensive system uses a set of Hall-effect devices and associated electronics to sense variations in the position of high-power magnets fixed in the eye sclera or in scleral contact lenses. The output of the Hall-effect devices is amplified by operational amplifiers, collected through an A/D converter, and analyzed in a PC computer by specific software.

Conditioned 'prehension' in the pigeon: kinematics, coordination and stimulus control of the pecking response

Like human prehensile behavior, the pigeon's ingestive pecking response is elicited by visual stimuli conveying information about the location and size of the target. This information is used to generate localized ingestive pecks whose gapes are amplitude-scaled to seed size, prior to contact. We employed high-resolution, 'real-time' monitoring of head acceleration, jaw movements and terminal peck location to examine the kinematics, coordination and stimulus control of conditioned pecking. Conditioning procedures were used to bring pecking under the control of visual targets whose stimulus properties (size, location) were independently varied, while simultaneously monitoring pecking response parameters. Stimulus control of the transport component (peck localization) is extremely precise, even in the absence of a specific localization-dependent reinforcement contingency. Subjects also showed amplitude-scaling of gape size to the size of a visual target, but over a more restricted range than shown to food pellets of comparable sizes. Comparison of the kinematic profiles of conditioned and ingestive pecks suggests that conditioned pecking is functionally analogous to human 'pointing' rather than 'grasping' behavior.

Feed pecking in young chickens: new techniques of evaluation

Three techniques were compared: automated recording (A) of 2 h of feeding activities conveyed to a computer by constantly connected electronic balances, videotaping (V) of a closeup of the head of a chick during a feed-pecking session analyzed by focal sampling at reduced speed (16 times slower), strength of pecking (S) at feed particles recorded from a feeder-weight signal conveyed to a computer by a customized electronic balance at rapid speed (24 times/s). These techniques were applied to 16-18-day-old chicks fed either a complete feed or a split diet (whole grain wheat + a complementary feed). The two feeds had similar pellet forms. The complementary feed particles were eaten at a slower rate than the complete feed particles (A and V techniques). Wheat grains were pecked with a weaker measured strength than the pellets (technique S). Two pecks of three did not result in prehension of a feed particle and were categorized as "exploratory" pecks. For 75% of the time during a continuous pecking session the head of the chick was in a static position, suggesting a long period of observation of the feed between 2 consecutive pecks. Videotaping with slow-motion focal sampling (V) offers potential development for the study of food intake behavior of chickens.

Key-peck probability and topography in a concurrent variable-interval variable-interval schedule with food and water reinforcers

The relation between variables that modulate the probability and the topography of key pecks was examined using a concurrent variable-interval variable-interval schedule with food and water reinforcers. Measures of response probability (response rates, time allocation) and topography (peck duration, gape amplitude) were obtained in 5 water- and food-deprived pigeons. Key color signaled reinforcer type. During baseline, response rates and time allocations were greater to the food key than to the water key, and food-key pecks had larger gapes and shorter durations. Relative probability measures (for the food key) were increased by prewatering and decreased by prefeeding. Deprivation effects upon topography measures were apparent only when food- and water-key pecks were analyzed separately. Food-key gape amplitudes increased with prewatering and decreased with prefeeding. The clearest effect occurred with prewatering. There were no consistent effects upon water-key gapes. The key color-reinforcer relation was reversed for 3 pigeons to determine how response topography was modulated during the transition from food- to water-key pecks. Reacquisition was faster for the probability than for the topography measures. Analysis of gape-amplitude distributions during reversal indicated that response-form modulation proceeded through the generation of intermediate gape sizes.

Organization of afferent and efferent projections of the nucleus basalis prosencephali in a passerine, Taeniopygia guttata

The connections of nucleus basalis (NB) of the rostral forebrain of the zebra finch were investigated electrophysiologically and with anterograde and retrograde tracing methods to determine their functional organization, the sources of their pontine afferents, and the targets of their telencephalic efferents. The nucleus was found to be partitioned into three major components, a rostral lingual part that received a hypoglossal projection via a lateral subnucleus of the principal sensory trigeminal nucleus (PrV), a middle beak part that received a trigeminal projection via a medial subnucleus of PrV, and a caudal auditory part that received a short latency auditory projection via the intermediate nucleus of the lateral lemniscus. Beak NB also received a projection from a paralateral lemniscal nucleus, and the dorsocaudal part of auditory NB and the medially adjacent neostriatum also received a projection from a lateral subnucleus of the superior vestibular nucleus (VS). The efferent projections of each of the three major parts of NB were mainly to the adjacent neostriatum frontale (NF), which then provided projections to the lobus parolfactorius (exclusive of area X), the lateral archistriatum intermedium (Ail), and the lateral neostriatum caudale (NCl). Ail received a projection from NCl and provided terminal fields to the contralateral NCl and the NF. The major projections of Ail, however, descended bilaterally through the brainstem via the occipitomesencephalic tracts, with dense terminations in the medial spiriform nucleus and with extensive bilateral terminations throughout the lateral reticular formation of the pons and medulla. For the most part, jaw, tongue, and tracheosyringeal motor nuclei did not receive terminations. The results suggest that NB in zebra finch, like NB in pigeon and duck, is likely to be a major component of trigeminal sensorimotor circuitry involved in feeding and in other oral-manipulative behaviors. Results also show that the auditory component of NB is not directly linked to the vocal control system at telencephalic levels, but the possibility remains that the lingual, beak, and auditory parts of NB play a role in vocalization by multisynaptic influences on cranial nerve motor nuclei innervating various parts of the vocal tract.

Effects of food-pellet size on rate, latency, and topography of autoshaped key pecks and gapes in pigeons

Four pigeons responded under autoshaping contingencies in which different conditional stimuli (red or green keylights) were associated with unconditional stimuli of different magnitudes (large or small food pellets) over successive trials within a session. Both topography (beak opening or gape) and strength (rates and latencies of key pecks and gapes) of responding during the conditional stimuli depended on the magnitude of the correlated unconditional stimulus. Key-peck and gape rates were higher and latencies were shorter in large-pellet trials than in small-pellet trials. Gape amplitudes varied directly with pellet size, although conditional and unconditional gapes were larger than either pellet. These findings were replicated when the key colors were presented either on one or two keys and after reversals of the color-size correlations. Because the unconditional stimulus was varied through pellet size, magnitude was not confounded with food-access duration or quality. These results demonstrate the effects of the magnitude of the unconditional stimulus, in that rates and latencies of both key pecks (which are directed movements toward the key) and gapes (which are independent of the bird's position and key properties) varied with pellet size. Gape measures were unique in that two dimensions (response strength and topography) of a single response class varied simultaneously with magnitude.

Systematic changes in gaping during the ontogeny of pecking in ring doves (Streptopelia risoria)

Food pecking in the ring dove is a skilled prehensile response that is similar to, but simpler than, many other prehensile responses. Previous work has shown that this response is initially poorly executed and requires experience for its accurate direction and coordination. The response involves two components: the thrusting of the bird's head toward food, and the opening and closure of the beak around food. Here, this second component, called gape, is followed through development with a precise measurement system. Four squabs moved through a similar sequence of three gape topographies, each of which is more efficient in picking up seed, during development. The present outcome, together with other work, argues for a substantial contribution of experience with pecking to the development of food pecking. We discuss the implications of these findings for understanding the ontogeny of motor control and for understanding how experience affects behavioral development.

Autoshaping the pigeon's gape response: acquisition and topography as a function of reinforcer type and magnitude

The pigeon's key-pecking response is experimentally dissociable into transport (head movement) and gape (jaw movement) components. During conditioning of the key-pecking response, both components come under the control of the conditioned stimulus. To study the acquisition of gape conditioned responses and to clarify the contribution of unconditioned stimulus (reinforcer) variables to the form of the response, gape and key-contact responses were recorded during an autoshaping procedure and reinforcer properties were systematically varied. One group of 8 pigeons was food deprived and subgroups of 2 birds each were exposed to four different pellet sizes as reinforcers, each reinforcer signaled by a keylight conditioned stimulus. A second group was water deprived and received water reinforcers paired with the conditioned stimulus. Water- or food-deprived control groups received appropriate water or food reinforcers that were randomly delivered with respect to the keylight stimulus. Acquisition of the conditioned gape response frequently preceded key-contact responses, and gape conditioned responses were generally elicited at higher rates than were key contacts. The form of the conditioned gape was similar to, but not identical with, the form of the unconditioned gape. The gape component is a critical topographical feature of the conditioned key peck, a sensitive measure of conditioning during autoshaping, and an important source of the observed similarities in the form of conditioned and consummatory responses.

Dissecting the conditioned pecking response: an integrated system for the analysis of pecking response parameters

The conventional pecking response key, although an excellent transducer of response rate, can provide minimal information on the topography, coordination, or localization of conditioned pecking. We describe the hardware and software components of a system that, in addition to recording response rates, permits simultaneous "on-line" monitoring of head acceleration, jaw movement, terminal peck location, and duration of pecking response. Head movements are monitored with a miniature accelerometer, jaw movements with a magnetosensitive transducer, and peck location with modified touch screen technology. Initial experiments with the system suggest that it will be useful in studies of response differentiation, acquisition and maintenance of complex discriminations, and interaction of conditioned and unconditioned stimuli in the control of pecking response probability and response topography.

Jaw muscle (EMG) activity and amplitude scaling of jaw movements during eating in pigeon (Columba livia)

During each phase of the pigeon's eating sequence, jaw opening amplitude (gape) is adjusted to the size of the food object; first prior to contact (Grasping), again in positioning the food (Stationing), and finally, during its movement through the oral cavity (Intraoral Transport). Part I of this study examined jaw movement kinematics during ingestion of different size food pellets to determine the relative contribution of velocity and rise time variables. Part II specified the muscle activity patterns mediating each phase of the eating sequence, and determined how these patterns are modulated to produce adjustments of gape size. The relative contribution of velocity and rise time variables to the control of gape differs in each phase of the eating sequence. However, for any pellet size, variations in opening rise time may function in a compensatory manner to minimize gape "undershooting". Each phase of the eating sequence is mediated by a characteristic muscle activity pattern. The adjustment of gape size to pellet size involves systematic modulation of this pattern, and the parameters modulated differ in the different phases in a manner which may reflect the functional requirements of each phase.

Trigeminal deafferentation and prehension in the pigeon

During the grasping and manipulation phases of the pigeon's ingestive pecking behavior, jaw opening movements are scaled to the size of the target (food) object. To assess the contribution of beak mechanoreceptor afferents to the control of scaling we examined the effects of bilateral trigeminal deafferentation upon the kinematics of jaw opening trajectories. Deafferented subjects exhibited both a transient reduction in the accuracy of peck localization and a more persistent deficit in the effectiveness of their ingestive pecking response. However, they continued to exhibit the same classes of jaw movement described for the normal pigeon. The functional relation between target size and gape remained unchanged after deafferentation as did the relationships among kinematic variables controlling jaw opening. However, deafferentation produced small but significant increase in the absolute values of peak gape for both grasping and mandibulation which reflects an increase in peak opening velocity. The results are discussed in relation to the problem of sensory control of rapid targeted movements.

Prehension in the pigeon. I. Descriptive analysis

Eating in the pigeon involves a series of jaw movements some of which serve a prehensile function; i.e., they are utilized in the grasping and manipulation of objects. These prehensile behaviors are extremely brief (30-80 ms), produce an adjustment of jaw opening amplitude to the size of the food object, are mediated by an effector system involving a relatively small number of muscles and are amenable to both "reflexive" and "voluntary" control. This combination of structural simplicity and functional complexity suggests that the pigeon's jaw movements may provide a useful "model system" for the study of motor control mechanisms in targeted movements. The present report provides a classification of jaw opening movements occurring during eating and a preliminary determination of the extent to which each movement class is scaled to the size of the food object. Jaw movements were monitored during responses to spherical food pellets of six different sizes (3.2-11.1 mm in diameter) using a transducing system which produces a continuous record of gape (i.e., interbeak distance). Assignment to movement classes was then carried out using a computer-assisted scoring program. Functions relating jaw opening amplitude to target size were determined for each movement class. Four jaw movement classes were identified: Prepecks (just prior to pecking), Grasps (opening movements made during pecking but prior to contact with the target), Mandibulations (movements serving to position and transport the object within the buccal cavity) and Swallows. For two of these movement classes (Grasps, Mandibulations) jaw opening amplitude is scaled to pellet size but the scaling functions differ in ways that reflect the functional requirements of the two behaviors.(ABSTRACT TRUNCATED AT 250 WORDS)

A microcomputer-based system for multi-channel neurophysiological recording

A set of software utility programs is described which, in association with a microcomputer and a commercially available analog-to-digital converter may be used to acquire, store, manipulate and display large amounts of behavioral and/or physiological data in digitized form.

Analysis of head movement and position using hall effect devices

We describe a system for the analysis of head displacement and angle. This system utilizes an inexpensive array of Hall effect transducers and associated electronics. Computer analysis of the output of the system permits real time display of head angle, position and associated velocity measures.

Two-dimensional jaw tracking and EMG recording system implanted in the freely moving rabbit

A system for simultaneously recording mandibular position in the sagittal plane together with masticatory muscle activity was designed and tested in rabbits. Two small magnetic sensors were implanted in the maxillary bone and a powerful magnet made of a rare earth metal attached to the mandibular central incisors. The magnetic sensors detected the mandibular movements in the sagittal plane by movement of the magnet. Masseter EMG was recorded by fine wire electrodes and amplified by a specially designed amplifier. The necessary preamplifiers were assembled as an integrated circuit (IC) chip in a small housing. The signals from the preamplifier were then passed through a signal processing unit and taped on an instrumentation tape. The system was applied to the freely moving rabbit supplied with food and water during the night. It worked without any trouble for more than 24 h. Since the implanted magnetic sensors were stable for more than 4 months, long-term recording could be done by merely reimplanting the magnet, the cables and the EMG electrodes, which was simple.

An automatic pellet dispenser for precise control of feeding topography in granivorous birds

Design and construction of an automatic pellet dispenser for granivorous birds are described. The dispenser permits rapid pneumatic delivery of pellets (five pellets per second maximum) to one controlled position and does not interfere with simultaneous electrophysiological recording. In addition, the device continuously indicates presence or absence of a pellet in the delivery position. This automatic dispenser proved very effective in our studies of stereotyped topographies of feeding in granivorous birds, such as pigeons and chickens.

Grasping in the pigeon: mechanisms of motor control

A quantitative analysis of grasping in the pigeon suggests important functional similarities between the visuomotor controls of the avian beak and the primate hand. Beak-opening (gape) during eating is directly proportional to target size and the adjustment is completed prior to contact. The control of gape size involves variations in both the velocity and duration of jaw opening and these parameters are mediated by different effector systems (jaw muscles, neck muscles). Nerve section experiments were used to identify jaw motoneurons which are components of the final common path for grasping. Grasping in the pigeon approximates the functional complexity of mammalian visuomotor behavior but is mediated by a relatively simple effector system.