Rate Of Head Movements Research Articles

Complexity analysis of head movements in autistic toddlers.

Early differences in sensorimotor functioning have been documented in young autistic children and infants who are later diagnosed with autism. Previous research has demonstrated that autistic toddlers exhibit more frequent head movement when viewing dynamic audiovisual stimuli, compared to neurotypical toddlers. To further explore this behavioral characteristic, in this study, computer vision (CV) analysis was used to measure several aspects of head movement dynamics of autistic and neurotypical toddlers while they watched a set of brief movies with social and nonsocial content presented on a tablet. Data were collected from 457 toddlers, 17-36 months old, during their well-child visit to four pediatric primary care clinics. Forty-one toddlers were subsequently diagnosed with autism. An application (app) displayed several brief movies on a tablet, and the toddlers watched these movies while sitting on their caregiver's lap. The front-facing camera in the tablet recorded the toddlers' behavioral responses. CV was used to measure the participants' head movement rate, movement acceleration, and complexity using multiscale entropy. Autistic toddlers exhibited significantly higher rate, acceleration, and complexity in their head movements while watching the movies compared to neurotypical toddlers, regardless of the type of movie content (social vs. nonsocial). The combined features of head movement acceleration and complexity reliably distinguished the autistic and neurotypical toddlers. Autistic toddlers exhibit differences in their head movement dynamics when viewing audiovisual stimuli. Higher complexity of their head movements suggests that their movements were less predictable and less stable compared to neurotypical toddlers. CV offers a scalable means of detecting subtle differences in head movement dynamics, which may be helpful in identifying early behaviors associated with autism and providing insight into the nature of sensorimotor differences associated with autism.

Cat vocalization in aversive and pleasant situations

Vocalization may transmit information from the emitting animal, including information about his or her emotional state. This study aimed to compare the vocal and the behavioral responses of domestic cats during an aversive and a pleasant situation. A total of 74 cats (29 males and 45 females) in the city of Curitiba, Southern Brazil, participated in the study; 68 (26 males and 42 females) were divided into 2 treatments: an aversive situation (AS), which was a car transport event where the cat was in a crate, or a pleasant situation (PS), where the cat was offered a snack. The other animals (3 males and 3 females) participated in both situations. Behavioral signals and individual vocalizations were registered through video recordings and further evaluated in each scenario. Cats in the PS had a higher fundamental frequency of vocalizations (10.1%), a lower range of pitches (tessitura) (33.9%) and twice the rate of head movement rates as compared to AS. For call duration there was significant interaction between treatment and sex. Additionally, there were differences in the vocal parameters and the behavioral signals due to sex, age, and coat color. Females and kittens have higher fundamental frequencies may be due to anatomical characteristics. Solid-colored coated cats presented higher fundamental frequency than other coat colors. Overall, vocal parameters and behavioral signals seem useful indicators for studying the emotions of cats in different situations. Further studies are warranted to understand the subtleties of cat vocalization across sex, age, and coat color.

Optimization of 3D printing parameters with sodium alginate hydrogel

In order to obtain biologically compatible objects with mechanical properties close to living tissues, 3D printing with biocompatible sodium alginate hydrogel at room temperature on the modified desktop 3D printer Up! Mini (manufactured by PP3DP, China) was carried out. The standard print head was replaced with a special syringe-extruder to allow the extrusion of a hydrogel, the details of which were made by 3D printing from ABS plastic. Of the parameters, the standard material feed and print head movement rates were changed. For accurate reproduction of object sizes using 3D printing from this hydrogel the next parameters were established: the optimal concentration of sodium alginate in extruded hydrogel (2.5 wt.%); the composition of the “support” gelatin suspension, which was fixed on the printing table of a 3D printer and served as volumetric support for hydrogel (10 g of calcium chloride CaCl2 and 13.5 g of gelatin per 500 ml of distilled water). The method of its preparation includes 1 minute mixing of components blend, dispersion at 9000 rpm on IKA ULTRA-TURRAX T 25 digital disperser, 4 hours settling at 4 °C, 3 minutes centrifuging at 5500 rpm, removal of the supernatant. The optimal movement speed of the print head during 3D printing and the speed of extrusion of the hydrogel during the formation of the external perimeter of the printing object are 9–11 and 5 mm/s, respectively, as well as the speed of material extrusion during the formation of the internal filling of the model is 0.83 mm/s.

Atypical postural control can be detected via computer vision analysis in toddlers with autism spectrum disorder

Evidence suggests that differences in motor function are an early feature of autism spectrum disorder (ASD). One aspect of motor ability that develops during childhood is postural control, reflected in the ability to maintain a steady head and body position without excessive sway. Observational studies have documented differences in postural control in older children with ASD. The present study used computer vision analysis to assess midline head postural control, as reflected in the rate of spontaneous head movements during states of active attention, in 104 toddlers between 16–31 months of age (Mean = 22 months), 22 of whom were diagnosed with ASD. Time-series data revealed robust group differences in the rate of head movements while the toddlers watched movies depicting social and nonsocial stimuli. Toddlers with ASD exhibited a significantly higher rate of head movement as compared to non-ASD toddlers, suggesting difficulties in maintaining midline position of the head while engaging attentional systems. The use of digital phenotyping approaches, such as computer vision analysis, to quantify variation in early motor behaviors will allow for more precise, objective, and quantitative characterization of early motor signatures and potentially provide new automated methods for early autism risk identification.

Does retinal configuration make the head and eyes of foveate birds move?

Animals move their heads and eyes to compensate for movements of the body and background, search, fixate, and track objects visually. Avian saccadic head/eye movements have been shown to vary considerably between species. We tested the hypothesis that the configuration of the retina (i.e., changes in retinal ganglion cell density from the retinal periphery to the center of acute vision-fovea) would account for the inter-specific variation in avian head/eye movement behavior. We characterized retinal configuration, head movement rate, and degree of eye movement of 29 bird species with a single fovea, controlling for the effects of phylogenetic relatedness. First, we found the avian fovea is off the retinal center towards the dorso-temporal region of the retina. Second, species with a more pronounced rate of change in ganglion cell density across the retina generally showed a higher degree of eye movement and higher head movement rate likely because a smaller retinal area with relatively high visual acuity leads to greater need to move the head/eye to align this area that contains the fovea with objects of interest. Our findings have implications for anti-predator behavior, as many predator-prey interaction models assume that the sensory system of prey (and hence their behavior) varies little between species.

Changes in the integration of self motion and auditory spatial cues with age, hearing impairment, and use of hearing devices

To resolve a front/back confusion, listeners may use both the spectral cues associated with the pinnae and they may turn their heads and note the direction in which the signal moves. Since hearing impairment typically involves the loss of high frequency information, one might expect that hearing impaired listeners would be more reliant on self-motion cues. Such listeners, however, often wear hearing aids that alter binaural level cues, suggesting they may distort dynamic self-motion-related cues. To examine these interactions, we utilized a previously published front/back illusion [W.O. Brimijoin and M.A. Akeroyd, iPercept. 3(3), 179–182 (2012)]: the perceptual location of signals whose position is moved at twice the angular rate of head movements is opposite to its physical location. In normal-hearing listeners, the illusion is powerful but weakens with increasing low-pass filter cutoff frequency. We found that for hearing-impaired listeners, the illusion was effective at all cutoff frequencies. The effect of hearing aids was heterogeneous across listeners, but in no case was a listener returned to normal performance, suggesting that hearing aids are not only failing to provide the listener with spatially-informative spectral cues, but they may interfere with self-motion-related cues. [Work supported by MRC (U135097131) and the Chief Scientist Office (Scotland).]

Do Male and Female Cowbirds See Their World Differently? Implications for Sex Differences in the Sensory System of an Avian Brood Parasite

BackgroundMale and female avian brood parasites are subject to different selection pressures: males compete for mates but do not provide parental care or territories and only females locate hosts to lay eggs. This sex difference may affect brain architecture in some avian brood parasites, but relatively little is known about their sensory systems and behaviors used to obtain sensory information. Our goal was to study the visual resolution and visual information gathering behavior (i.e., scanning) of brown-headed cowbirds.Methodology/Principal FindingsWe measured the density of single cone photoreceptors, associated with chromatic vision, and double cone photoreceptors, associated with motion detection and achromatic vision. We also measured head movement rates, as indicators of visual information gathering behavior, when exposed to an object. We found that females had significantly lower density of single and double cones than males around the fovea and in the periphery of the retina. Additionally, females had significantly higher head-movement rates than males.ConclusionsOverall, we suggest that female cowbirds have lower chromatic and achromatic visual resolution than males (without sex differences in visual contrast perception). Females might compensate for the lower visual resolution by gazing alternatively with both foveae in quicker succession than males, increasing their head movement rates. However, other physiological factors may have influenced the behavioral differences observed. Our results bring up relevant questions about the sensory basis of sex differences in behavior. One possibility is that female and male cowbirds differentially allocate costly sensory resources, as a recent study found that females actually have greater auditory resolution than males.

Making heads turn: association between head movements during vigilance and perceived predation risk in brown-headed cowbird flocks

Models of antipredator vigilance show that animals should be more vigilant when in smaller groups, when neighbours are farther away, and when they occur at the edge rather than at the centre of a group. However, models fail to specify how animals are expected to look out for threats while actually scanning. We suggest that head movements during scanning may represent a way that animals can control the value of scanning while in groups. Head movements can be used to increase visual coverage (visual search) as well as bring features of the environment to more sensitive parts of the eyes (visual fixation). We conducted a seminatural experiment with brown-headed cowbirds, Molothrus ater , in which we manipulated group size and neighbour distance, and recorded vigilance for peripheral and central individuals. During scanning, the rate of head movements by peripheral individuals increased, probably to enhance visual coverage due to their higher perceived risk of predation. However, individuals that were farther apart and in smaller groups used a different scanning strategy by reducing their rate of head movements (e.g. increased the averaged time they spent holding a given head position steady), probably to fixate their gaze longer on neighbours. Visual fixation may be useful for obtaining social information about predation threats from the behaviour of groupmates. We show that (1) a vigilance metric associated with head movement behaviour, which is attuned to the visual system of a species, can provide novel information about vigilance in groups, and that (2) birds have different head movement strategies, probably associated with different visual targets, when the risk of predation is higher.

Testing the Terrain Hypothesis: Canada Geese See Their World Laterally and Obliquely

The distribution of ganglion cells in the retina determines the specific regions of the visual field with high visual acuity, and thus reflects the perception of a species’ visual environment. The terrain hypothesis proposes that animals living in open areas should have a horizontal visual streak across the retina with high ganglion cell density to increase visual acuity along the horizon. We tested this hypothesis in Canada geese (Branta canadensis) by assessing retinal topography, visual field configuration, and scanning behavior. We found that geese have an oblique rather than a horizontal visual streak across the retina: from a dorsal-nasal to a ventral-temporal position. Geese showed narrow blind areas, which increased the range of their lateral vision, and a relatively large degree of eye movement. Canada geese have relatively wide binocular fields and can see their bill tips. Goose head movement rates were low compared to species with a single fovea, and head movement rates increased in visually obstructed habitats. Canada geese have high acuity across their retina, which would allow them to simultaneously scan the ground and the sky when the head is up and parallel to the ground, as well as align the visual streak with the horizon when the head is tilted downwards. Their visual streak, along with their large eye size, may reduce the need for large amplitude head movements during vigilance bouts in visually unobstructed habitats. Overall, the visual system of geese combines features related to the detection of predators/conspecifics in open areas (visual streak, large lateral field, reduced head movements) as well as visual specializations that would allow for monitoring both the ground and sky (oblique streak) and for extracting and handling of food items (wide binocular fields, visualization of the bill tip).

Visual systems and vigilance behaviour of two ground-foraging avian prey species: white-crowned sparrows and California towhees

Predator–prey interactions are regulated by the ability of individuals to detect, and then approach or avoid, each other. In visually guided organisms, the prevalent view is that predators have large binocular visual fields and high acuity, whereas prey have wide lateral areas and low acuity, which could affect vigilance behaviour. We characterized the configuration of the visual system (visual fields, retinal topography, visual acuity) and vigilance behaviour (head movement rate) of two ground-foraging avian prey (white-crowned sparrow, Zonotrichia leucophrys, California towhee, Pipilo crissalis) with laterally placed eyes. We found that the binocular field of both species (45°) was actually wider than those of some of their avian predators. Both species also had a single retinal specialization (high ganglion cell density area) located in the centro-temporal sector of the retina, which projected into the lateral and frontal part of the head. Wide binocular fields may increase binocular contrast to detect and visually guide the bill towards prey items. Both species had wider lateral visual fields and faster head movement rates than some of their predators, probably to enhance detection and visual tracking of predators. California towhees made faster sideways movements of the head than did white-crowned sparrows, probably to cover visual space more quickly with their retinal specialization because of the comparatively lower spatial resolution of their retinal periphery. Alternatively, California towhees might move their heads more rapidly to monitor for potential risks (e.g. competitors, predators), as they rely mostly on personal information because of their degree of territoriality. Our findings suggest that the visual system and vigilance behaviour of these two avian prey species combine traits to enhance predator detection through large visual coverage and fast head movements, but also to enhance food detection at close range through enhanced binocular vision.

Hawk Eyes II: Diurnal Raptors Differ in Head Movement Strategies When Scanning from Perches

BackgroundRelatively little is known about the degree of inter-specific variability in visual scanning strategies in species with laterally placed eyes (e.g., birds). This is relevant because many species detect prey while perching; therefore, head movement behavior may be an indicator of prey detection rate, a central parameter in foraging models. We studied head movement strategies in three diurnal raptors belonging to the Accipitridae and Falconidae families.Methodology/Principal FindingsWe used behavioral recording of individuals under field and captive conditions to calculate the rate of two types of head movements and the interval between consecutive head movements. Cooper's Hawks had the highest rate of regular head movements, which can facilitate tracking prey items in the visually cluttered environment they inhabit (e.g., forested habitats). On the other hand, Red-tailed Hawks showed long intervals between consecutive head movements, which is consistent with prey searching in less visually obstructed environments (e.g., open habitats) and with detecting prey movement from a distance with their central foveae. Finally, American Kestrels have the highest rates of translational head movements (vertical or frontal displacements of the head keeping the bill in the same direction), which have been associated with depth perception through motion parallax. Higher translational head movement rates may be a strategy to compensate for the reduced degree of eye movement of this species.ConclusionsCooper's Hawks, Red-tailed Hawks, and American Kestrels use both regular and translational head movements, but to different extents. We conclude that these diurnal raptors have species-specific strategies to gather visual information while perching. These strategies may optimize prey search and detection with different visual systems in habitat types with different degrees of visual obstruction.

Visual coverage and scanning behavior in two corvid species: American crow and Western scrub jay

Inter-specific differences in the configuration of avian visual fields and degree of eye/head movements have been associated with foraging and anti-predator behaviors. Our goal was to study visual fields, eye movements, and head movements in two species of corvids: American crow (Corvus brachyrhynchos) and Western scrub jay (Aphelocoma californica). American crows had wider binocular overlap, longer vertical binocular fields, narrower blind areas, and higher amplitude of eye movement than Western scrub jays. American crows can converge their eyes and see their own bill tip, which may facilitate using different foraging techniques (e.g., pecking, probing) and manufacturing and handing rudimentary tools. Western scrub jays had a higher head movement rate than American crows while on the ground, and the opposite between-species difference was found when individuals were perching. Faster head movements may enhance the ability to scan the environment, which may be related to a higher perceived risk of predation of Western scrub jays when on the ground, and American crows when perching. The visual field configuration of these species appears influenced mostly by foraging techniques while their scaning behavior, by predation risk.

Visual fields, eye movements, and scanning behavior of a sit-and-wait predator, the black phoebe (Sayornis nigricans)

Foraging mode influences the dominant sensory modality used by a forager and likely the strategies of information gathering used in foraging and anti-predator contexts. We assessed three components of visual information gathering in a sit-and-wait avian predator, the black phoebe (Sayornis nigricans): configuration of the visual field, degree of eye movement, and scanning behavior through head-movement rates. We found that black phoebes have larger lateral visual fields than similarly sized ground-foraging passerines, as well as relatively narrower binocular and blind areas. Black phoebes moved their eyes, but eye movement amplitude was relatively smaller than in other passerines. Black phoebes may compensate for eye movement constraints with head movements. The rate of head movements increased before attacking prey in comparison to non-foraging contexts and before movements between perches. These findings suggest that black phoebes use their lateral visual fields, likely subtended by areas of high acuity in the retina, to track prey items in a three-dimensional space through active head movements. These head movements may increase depth perception, motion detection and tracking. Studying information gathering through head movement changes, rather than body posture changes (head-up, head-down) as generally presented in the literature, may allow us to better understand the mechanisms of information gathering from a comparative perspective.

Effects of Physical and Visual Access to Prey on Patch Selection and Food Search Effort in a Sit-and-Wait Predator, the Black Phoebe

Abstract. For sit-and-wait predators, a key factor influencing foraging decisions is the ability to detect and track prey, which is expected to vary with the physical and light properties of the environment. We assessed how changes in visual and physical prey availability altered perch selection and visual search activity (head-movement rate and bout length) in the Black Phoebe (Sayornis nigricans), a sit-and-wait flycatcher. We used an observational approach by studying individuals in foraging areas that varied in the ecological factors of interest across an urbanized landscape. Black Phoebes selected perches with high levels of tree and grass cover and low light intensity, which could increase access to prey and reduce predation risk. Visual searching for prey decreased as grass cover increased and tree cover decreased, likely because of less physical and visual obstruction. Visual searching increased with light intensity, probably as a result of the effects of glare, but chromatic contrast did not exer...

Effect of defensive behaviour by cattle on the feeding success and nutritional state of the tsetse fly, Glossina pallidipes (Diptera: Glossinidae)

AbstractTwo experiments were conducted at Galana Ranch, Kenya, which examined, under natural conditions, the relationships between the number of tsetse flies (Glossina pallidipes Austen) attracted to cattle, the rate at which the cattle made defensive movements, and the feeding success of the tsetse. The most frequent defensive movements were skin ripples and tail swishes, while leg kicks were of intermediate frequency, and head and ear movements were infrequent. In one experiment, the rate of skin ripples, but no other type of defensive movement, was significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was significantly (P < 0.004) correlated with the rate of leg kicks, more weakly with the rate of head movements (P < 0.07), and uncorrelated with the rates of other types of defensive movement. In the second experiment, the rates of skin ripples, tail swishes and leg kicks were significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was again significantly correlated to the rate of leg kicks (P < 0.03), more weakly to the rate of head movements (P < 0.04), and unrelated to the rates of other types of defensive movement. In neither experiment was there a significant relationship between the number of tsetse attracted to the cattle and the proportion that engorged, suggesting that any density-dependent feeding success was too weak to be detected. In experiment 1, the relative fat content of the male G. pallidipes that fed decreased as the rate of leg kicks increased, suggesting that when hosts are more active the sub-sample of tsetse that feed, out of those that approach, is both smaller and hungrier. There was no detectable effect of host defensive behaviour on the bloodmeal size of male G. pallidipes.