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PubMed1988

Development of orientation discrimination in infancy.

It has previously been found by us, with a visual evoked potential (VEP) measure, that orientation discrimination of dynamic patterns in infants can be demonstrated from around 6 weeks after birth. Experiments are reported in which orientation discrimination was measured behaviourally, in two infant control habituation procedures, with both dynamic and static patterns. When dynamic patterns identical to those in our previous VEP studies were used, the first positive evidence of orientation discrimination was found at around 6 weeks postnatally. The time course of both the VEP and the behavioural measures was similar. However, with static patterns, evidence of orientation discrimination by newborns was found if the infants were allowed to compare the habituated and novel orientations in a paired simultaneous comparison after habituation, but was not found when the habituated and novel stimulus were presented sequentially. The positive evidence of orientation discrimination in newborns supports the hypothesis that some form of orientationally tuned detectors can be used for discrimination of static patterns at birth. However, some developmental change over several weeks seems to be required before a positive electrophysiological VEP response can be measured for dynamic patterns changing in orientation.

Child Development↗
PubMedDate not supplied

Contextual modulation of orientation tuning contributes to efficient processing of natural stimuli.

It has been proposed that sensory neurons are adapted to the statistical structure of the natural environment in order to encode natural stimuli efficiently. While spatiotemporal correlations in luminance signals may be decorrelated by neurons in early visual processing stages, higher-order correlations, such as those in the orientation domain, are likely to persist in the input representation until the cortical level. In this study, we first examine orientation correlations in natural stimuli across brief time intervals and across nearby regions of space, and find strong correlations in both domains. We then examine contextual modulation of orientation tuning. We find that both temporal and spatial contexts exert a common influence on orientation tuning, shifting tuning away from the orientation of either the adapting (temporal) or surrounding (spatial) grating. Finally, we incorporate this context-mediated repulsive shift in orientation tuning into a model of cortical responses. We find that a direct result of the shift is a reduction of the redundancy in the population responses evoked by the orientation configurations that are most common in natural stimuli. Thus, cortical neurons may be adapted to the statistics of orientation in natural stimuli in order to increase the efficiency of natural stimulus representation.

Animals↗
PubMed2002

The organization of orientation selectivity throughout macaque visual cortex.

A double-label deoxyglucose technique was used to study orientation columns throughout visual cortex in awake behaving macaques. Four macaques were trained to fixate while contrastreversing, stationary gratings or one-dimensional noise of a single orientation or an orthogonal orientation were presented, during uptake of [14C]deoxyglucose ([14C]DG) or [3H]DG, respectively. The two orthogonal stimulus orientations produced DG-labeled columns that were maximally separated in the two isotope maps (inter-digitated) in four areas: V1, V2, V3 and VP. The topographic change from interdigitated to overlapping columns occurred abruptly rather than gradually, at corresponding cortical area borders (e.g. VP and V4v, respectively). In addition, the data suggest that orientation column topography systematically changes with retinotopic eccentricity. In V1, the orientation columns systematically avoided the cytochrome oxidase blobs in the parafoveal representation, but converged closer to the blobs in the foveal representation. A control experiment indicated that this was unlikely to reflect eccentricity-dependent differences in cortical spatial frequency sensitivity. A similar eccentricity-dependent change in the topography of orientation columns occurred in V2. In parafoveal but not foveal visual field representations of V2, the orientation columns were centered on the thick cytochrome oxidase stripes, extended into the adjacent interstripe region, but were virtually absent in the thin stripes.

Animals↗
PubMed2000

Perception of mirror symmetry reveals long-range interactions between orientation-selective cortical filters.

We investigated perceptual interactions between orientation selective cortical filters using a task in which the observer was to detect mirror symmetry in briefly flashed visual patterns composed of oriented Gabor elements. On each trial, the Gabor patches were randomly placed in one half of the stimulus region, and symmetry was generated by reflecting the positions of the patch centers across the vertical axis. A prespecified proportion of patches were in mirror symmetrical positions with the remaining patches placed at random positions. The perception of mirror symmetry was measured for three stimulus conditions: (1) same orientation (i.e. all the local Gabor elements were either vertical or horizontal), (2) mixed matching (i.e. the orientations could be randomly both vertical and horizontal with the constraint that the orientations in a mirror symmetrical pair were matching), and (3) mixed opposing (i.e. the orientations were both vertical and horizontal, but in a mirror symmetrical pair they were always orthogonal). We found that the perception of global symmetry was poorer (thresholds were elevated) when the local orientations of feature pairs were orthogonal than when they were matched. This result is consistent with the properties of the neurons in the corpus callosum, which selectively interconnect cortical filters with identical orientation specificity.

Brain Mapping↗
PubMed1992

Human vision combines oriented filters to compute edges.

The experiments examined the perceived spatial structure of plaid patterns, composed of two or three sinusoidal gratings of the same spatial frequency, superimposed at different orientations. Perceived structure corresponded well with the pattern of zero crossings in the output of a circular spatial filter applied to the image. This lends some support to Marr & Hildreth's (Proc. R. Soc. Lond. B 207, 187 (1980)) theory of edge detection as a model for human vision, but with a very different implementation. The perceived structure of two-component plaids was distorted by prior exposure to a masking or adapting grating, in a way that was perceptually equivalent to reducing the contrast of one of the plaid components. This was confirmed by finding that the plaid distortion could be nulled by increasing the contrast of the masked or adapted component. A corresponding reduction of perceived contrast for single gratings was observed after adaptation and in some masking conditions. I propose the outlines of a model for edge finding in human vision. The plaid components are processed through cortical, orientation-selective filters that are subject to attenuation by forward masking and adaptation. The outputs of these oriented filters are then linearly summed to emulate circular filtering, and zero crossings (zcs) in the combined output are used to determine edge locations. Masking or adapting to a grating attenuates some oriented filters more than others, and although this changes only the effective contrast of the components, it results in a geometric distortion at the zc level after different filters have been combined. The orientation of zcs may not correspond at all with the orientation of Fourier components, but they are correctly predicted by this two-stage model. The oriented filters are not 'orientation detectors', but are precursors to a more subtle stage that locates and represents spatial features.

Adaptation, Ocular↗
PubMed2005

A multichip aVLSI system emulating orientation selectivity of primary visual cortical cells.

In this paper, we designed and fabricated a multichip neuromorphic analog very large scale integrated (aVLSI) system, which emulates the orientation selective response of the simple cell in the primary visual cortex. The system consists of a silicon retina and an orientation chip. An image, which is filtered by a concentric center-surround (CS) antagonistic receptive field of the silicon retina, is transferred to the orientation chip. The image transfer from the silicon retina to the orientation chip is carried out with analog signals. The orientation chip selectively aggregates multiple pixels of the silicon retina, mimicking the feedforward model proposed by Hubel and Wiesel. The chip provides the orientation-selective (OS) outputs which are tuned to 0 degrees, 60 degrees, and 120 degrees. The feed-forward aggregation reduces the fixed pattern noise that is due to the mismatch of the transistors in the orientation chip. The spatial properties of the orientation selective response were examined in terms of the adjustable parameters of the chip, i.e., the number of aggregated pixels and size of the receptive field of the silicon retina. The multichip aVLSI architecture used in the present study can be applied to implement higher order cells such as the complex cell of the primary visual cortex.

Action Potentials↗
PubMed1997

Development of orientation preference maps in area 18 of kitten visual cortex.

We investigated the development of orientation preference maps in the visual cortex of kittens by repeated optical imaging from the same animal. Orientation maps became detectable for the first time around postnatal day (P) 17 and improved continuously in strength unitl P30, the time at which their appearance became adultlike. During this developmental period the overall geometry of the maps remained unchanged, suggesting that the layout of the orientation map is specified prior to P17. Hence, before the visual cortex becomes susceptible to experience-dependent modifications its functional architecture is largely specified. This suggests that the initial development and layout of orientation preference maps are determined by intrinsic processes that are independent of visual experience. This conclusion is further supported by the result that orientation maps were well expressed at P24 in binocularly deprived kittens. Because the appearance of the first orientation-selective neurons and the subsequent development of orientation preference maps correlated well with the time course of the expression and refinement of clustered horizontal connections, we propose that these connections might contribute to the specification of orientation preference maps.

Animals↗
PubMed1990

Disruption and recovery of the orienting response following shock or context change in preweanling rats.

Previous research has shown that placement of preweanling rats in an unfamiliar environment inhibits both heart rate and behavioral orienting responses to an auditory stimulus, and that the orienting response gradually reappears during the following 15 min. Four experiments designed to evaluate two potential explanations of this effect were conducted. If the arousal induced by an unfamiliar environment disrupts sensory information processing, so should the arousal induced by mild electric shock. In two experiments, the orienting response was inhibited in proportion to number of shocks received and rate of recovery was comparable to that observed in the unfamiliar environment. New environments also contain many unfamiliar stimuli which may overload the rats' limited information processing capacity. In two experiments a change in environmental stimulation was shown to inhibit the orienting response. Recovery of the orienting response followed the same time course as that seen following shock or placement in an unfamiliar environment. Although the results of this study clearly demonstrate environmental inhibition of the orienting response, they provide little support for either the "arousal" or the "information overload" hypotheses of orienting response inhibition. The implications of these data for current theoretical conceptualizations of the orienting response are discussed.

Acoustic Stimulation↗
PubMed1999

Control of spatial orientation of the angular vestibulo-ocular reflex by the nodulus and uvula of the vestibulocerebellum.

Eye velocity produced by the angular vestibulo-ocular reflex (aVOR) tends to align with the summed vector of gravity and other linear accelerations [gravito-inertial acceleration (GIA)]. Defined as "spatial orientation of the aVOR," we propose that it is controlled by the nodulus and uvula of the vestibulocerebellum. Here, electrical stimulation, injections of the GABAA agonist, muscimol, and single-cell recordings were utilized to investigate this spatial orientation. Stimulation, injection, and recording sites in the nodulus were determined in vivo by MRI and verified in histological sections. MRI proved to be a sensitive, reliable way to localize electrode placements. Electrical stimulation at sites in the nodulus and sublobule d of the uvula produced nystagmus whose slow-phase eye-velocity vectors were either head centric or spatially invariant. When head centric, the eye velocity vector remained within +/- 45 degrees of the vector obtained with the animal upright, regardless of head position with respect to gravity. When spatially oriented, the vector remained relatively constant in space in one on-side position, with respect to the vector determined with the animal upright. A majority of induced movements from the nodulus were spatially oriented. Spatially oriented movements were generally followed by after-nystagmus, which had the characteristics of optokinetic after-nystagmus (OKAN), including orientation to the GIA. After muscimol injections, horizontal-to-vertical cross-coupling was lost or reduced during OKAN in tilted positions. This supports the hypothesis that the nodulus mediates yaw-to-vertical or roll cross-coupling. The injections also shortened the yaw-axis time constant and produced contralateral horizontal spontaneous nystagmus, whose velocity varied as a function of head position with regard to gravity. Nodulus units were tested with static head tilt, sinusoidal oscillation around a spatial horizontal axis with the head in different orientations relative to the pitching plane, and off-vertical axis rotation (OVAR). The direction of the response vectors of the otolith-recipient units in the nodulus, determined from static and/or dynamic head tilts, were confirmed by OVAR. These vector directions lay close to the planes of the vertical canals in 7/10 units; many units also had convergent input from the vertical canals. It is postulated that the orientation properties of the aVOR result from a transfer of otolith input regarding head tilt along canal planes to canal-related zones of the nodulus. In turn, Purkinje cells in these zones project to vestibular nuclei neurons to control eye velocity around axes normal to these same canal planes.

Animals↗
PubMed1982

Noise effects in free recall with different orienting tasks.

Subjects were shown either a list of non-associated words or a list on which words could be organized into related groups. In Expt 1 either no orienting instructions were given or subjects had to rate the words for Pleasantness (semantic orienting task). The three-way interaction of noise x list type x orienting task was significant. Eighty-five dBC white noise compared with 65 dBC improved performance on the non-associated list with no orienting task and increased recall in the original sequence, but had the reverse effect with semantic orienting. With the associated list noise had no marked effects in the non-orienting condition, and improved performance in the orienting condition. It is concluded that in noise maintenance rehearsal tends to be adopted unless instructions induce an alternative strategy, and in the latter event noise reinforces use of the alternative strategy. In Expt 2, all subjects carried out a physical orienting task, rating the words for the sounds they contained. Noise aided performance on the non-associated list and impaired it on the associated list. This result is taken to be compatible with the above interpretation of noise effects.

Humans↗
PubMed2004

Origin of orientation-dependent asymmetries in vestibulo-ocular reflexes evoked by caloric stimulation.

A caloric stimulus evokes primarily a horizontal vestibulo-ocular reflex (VOR) when subjects are in a supine or prone orientation with the horizontal semicircular canal plane oriented vertically. In both monkeys and humans, the magnitude of VOR eye movements is greater in the supine than in the prone orientation, indicating that some factor or factors, other than the conventionally accepted convective stimulation of the horizontal canals, contributes to the generation of the VOR. We used long-duration caloric irrigations and mathematical models of canal-otolith interactions to investigate factors contributing to the prone/supine asymmetry. Binaural caloric irrigations were applied for 7.5 or 9.5 min with subjects in a null orientation with horizontal canals in the earth-horizontal plane (control trial), or with the subject's pitch orientation periodically changing between null, supine, and prone positions with each orientation held for 30 s (caloric step trial). The control trial responses identified a small response attributable to a direct thermal effect on vestibular afferent activity that accounted for only 15% of the observed prone/supine asymmetry. We show that the gravito-inertial force resolution hypothesis for sensory integration of canal and otolith information predicts that the central processing of canal and otolith information produces an internal estimate of motion that includes both a rotational motion component and a linear acceleration component. These components evoke a horizontal angular VOR and linear VOR, which combine additively in the supine orientation, but subtract in the prone orientation, thus accounting for the majority of the observed prone/supine asymmetry.

Adult↗
PubMed2002

Compensatory and orienting eye movements induced by off-vertical axis rotation (OVAR) in monkeys.

Nystagmus induced by off-vertical axis rotation (OVAR) about a head yaw axis is composed of a yaw bias velocity and modulations in eye position and velocity as the head changes orientation relative to gravity. The bias velocity is dependent on the tilt of the rotational axis relative to gravity and angular head velocity. For axis tilts <15 degrees, bias velocities increased monotonically with increases in the magnitude of the projected gravity vector onto the horizontal plane of the head. For tilts of 15-90 degrees, bias velocity was independent of tilt angle, increasing linearly as a function of head velocity with gains of 0.7-0.8, up to the saturation level of velocity storage. Asymmetries in OVAR bias velocity and asymmetries in the dominant time constant of the angular vestibuloocular reflex (aVOR) covaried and both were reduced by administration of baclofen, a GABA(B) agonist. Modulations in pitch and roll eye positions were in phase with nose-down and side-down head positions, respectively. Changes in roll eye position were produced mainly by slow movements, whereas vertical eye position changes were characterized by slow eye movements and saccades. Oscillations in vertical and roll eye velocities led their respective position changes by approximately 90 degrees, close to an ideal differentiation, suggesting that these modulations were due to activation of the orienting component of the linear vestibuloocular reflex (lVOR). The beating field of the horizontal nystagmus shifted the eyes 6.3 degrees /g toward gravity in side down position, similar to the deviations observed during static roll tilt (7.0 degrees /g). This demonstrates that the eyes also orient to gravity in yaw. Phases of horizontal eye velocity clustered ~180 degrees relative to the modulation in beating field and were not simply differentiations of changes in eye position. Contributions of orientating and compensatory components of the lVOR to the modulation of eye position and velocity were modeled using three components: a novel direct otolith-oculomotor orientation, orientation-based velocity modulation, and changes in velocity storage time constants with head position re gravity. Time constants were obtained from optokinetic after-nystagmus, a direct representation of velocity storage. When the orienting lVOR was combined with models of the compensatory lVOR and velocity estimator from sequential otolith activation to generate the bias component, the model accurately predicted eye position and velocity in three dimensions. These data support the postulates that OVAR generates compensatory eye velocity through activation of velocity storage and that oscillatory components arise predominantly through lVOR orientation mechanisms.

Animals↗
PubMed2005

Orientation tuning, but not direction selectivity, is invariant to temporal frequency in primary visual cortex.

The activity of neurons in primary visual cortex is influenced by the orientation, contrast, and temporal frequency of a visual stimulus. This raises the question of how these stimulus properties interact to shape neuronal responses. While past studies have shown that the bandwidth of orientation tuning is invariant to stimulus contrast, the influence of temporal frequency on orientation-tuning bandwidth is unknown. Here, we investigate the influence of temporal frequency on orientation tuning and direction selectivity in area 17 of ferret visual cortex. For both simple cells and complex cells, measures of orientation-tuning bandwidth (half-width at half-maximum response) are approximately 20-25 degrees across a wide range of temporal frequencies. Thus cortical neurons display temporal-frequency invariant orientation tuning. In contrast, direction selectivity is typically reduced, and occasionally reverses, at nonpreferred temporal frequencies. These results show that the mechanisms contributing to the generation of orientation tuning and direction selectivity are differentially affected by the temporal frequency of a visual stimulus and support the notion that stability of orientation tuning is an important aspect of visual processing.

Action Potentials↗
PubMed1976

Quantitative study of cortical orientation selectivity in visually inexperienced kitten.

1. Extracellular recordings were made from single units in the visual cortices of six kittens deprived of experience with pattern vision by binocular lid suture. 2. Selectivity for stimulus orientation was quantitatively assessed in 98 units; 90 responded selectively to the orientation of a moving bar stimulus, the remainder responding nonselectively or too poorly to classify. Cells in these visually inexperienced kittens were similar in their degree of selectivity for orientation to cells tested in adult cats. However, responses tended to be weaker and somewhat more erratic. 3. About half the cells in this simple responded to both directions of stimulus motion at the optimal orientation. Most of those responding to only one direction of motion were considered orientation rather than direction selective because they responded more strongly or more selectively to a moving bar than to a moving spot. 4. Cells appeared to be organized within the cortex in a pattern similar to that found in adult cats, with cells in one column selective for the same orientation, and adjacent column having similar preferred orientations. 5. It is concluded that selectivity for stimulus orientation in the cat's visual cortex is innately determined.

Animals↗
PubMed1985

Development of spatial receptive-field organization and orientation selectivity in kitten striate cortex.

The functional organization of the receptive field of neurons in striate cortex of kittens from 8 days to 3 mo of age was studied by extracellular recordings. A quantitative dual-stimulus technique was used, which allowed for analysis of both enhancement and suppression zones in the receptive field. Furthermore the development of orientation selectivity was studied quantitatively in the same cells. Already in the youngest kittens the receptive fields were spatially organized like adult fields, with a central zone and adjacent flanks that responded in opposite manner to the light stimulus. The relative suppression in the subzones was as strong as in adult cells. Both simple and complex cells were found from 8 days. The receptive fields were like magnified adult fields. The width of the dominant discharge-field zone and the distance between the positions giving maximum discharge and maximum suppression decreased with age in the same proportions. The decrease could be explained by a corresponding decrease of the receptive-field-center size of retinal ganglion cells. Forty percent of the cells were orientation selective before 2 wk, and the fraction increased to 94% at 4 wk. Cells whose responses could be attenuated to at least half of the maximal response by changes of slit orientation were termed orientation selective. The half-width of the orientation-tuning curves narrowed during the first 5 wk, and this change was most marked in simple cells. The ability of the cells to discriminate between orientations in statistical terms was weak in the youngest kittens due to a large response variability, and showed a more pronounced development than the half-width did. The orientation-tuning curves were fitted by an exponential function, which showed the shape to be adultlike in all age groups. Two kittens were dark reared until recording at 1 mo of age. The spatial receptive-field organization and the orientation selectivity in these kittens were similar to normal-reared kittens at 1 mo. The responsivity of the cells of the dark-reared kittens was lower, and the latency before firing was longer than in the normal-reared kittens of the same age, and these response properties were more similar to those in 1- to 2-wk-old normal kittens. Our results indicate that the spatial organization of the receptive field is innate in most cells and that visual experience is unnecessary for the organization to be maintained and for the receptive-field width to mature during the first month postnatally.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Visual orientation and spatial frequency discrimination: a comparison of single neurons and behavior.

Neurons in the visual cortex respond selectively to stimulus orientation and spatial frequency. Changes in response amplitudes of these neurons could be the neurophysiological basis of orientation and spatial frequency discrimination. We have estimated the minimum differences in stimulus orientation and spatial frequency that can produce reliable changes in the responses of individual neurons in cat visual cortex. We compare these values with orientation and spatial frequency discrimination thresholds determined behaviorally. Slopes of the tuning functions and response variability determine the minimum orientation and spatial frequency differences that can elicit a reliable response change. These minimum values were obtained from single cells using receiver operating characteristic (ROC) analysis. The average minimum orientation and spatial frequency differences that could be signaled reliably by cells from our sample were 6.4 degrees (n = 22) and 21.3% (n = 18), respectively. These values are approximately 0.20 of the average full tuning width at one-half height of the cells. Although these average values are well above the behaviorally determined thresholds, the most selective cells signaled orientation and frequency differences of 1.84 degrees and 5.25%, respectively. These values are of the same order of magnitude as the behavioral thresholds. We show that, because of slow fluctuations in a cell's responsivity, ROC analysis overestimates response variability. We estimate that these slow response fluctuations elevated our estimates of single cell "thresholds" by, on average, 30%. Our data point to an approximate correspondence between orientation and spatial frequency discrimination "thresholds" determined behaviorally and those estimated from the most selective single cortical cells. Interpretation of this quantitative correspondence is considered in the discussion.

Animals↗
PubMed1997

Reaching movements with similar hand paths but different arm orientations. II. Activity of individual cells in dorsal premotor cortex and parietal area 5.

Reaching movements with similar hand paths but different arm orientations. II. Activity of individual cells in dorsal premotor cortex and parietal area 5. J. Neurophysiol. 78: 2413-2426, 1997. Neuronal activity in primary motor cortex (MI) is altered when monkeys make reaching movements along similar handpaths at shoulder level with two different arm orientations, either in the natural orientation with the elbow positioned below the level of the shoulder and hand or in an abducted orientation with the elbow abducted nearly to shoulder level. The present study examines to what degree two other cortical areas, the dorsal premotor (PMd) and parietal area 5, also show modulation of cell activity related to arm geometry during reaching. The activity of most (89%) of the 207 cells in PMd recorded while monkeys made reaching movements showed a statistically significant change in activity between orientations [analysis of variation (ANOVA), P < 0.01]. A common effect of arm orientation on cell activity was a change in the overall level of discharge either before, during, and/or after movement (67%, ANOVA, task main effect, P < 0.01). Many cells (76%) showed a statistical change in their response to movement direction (ANOVA, task x direction interaction term, P < 0.01), including changes in dynamic range and changes in the preferred direction of cells that were directionally tuned in both arm orientations. Overall, these effects were similar qualitatively but not as strong quantitatively as those observed in MI. A sample of cells was recorded in area 5 of one monkey. Most (95%) of the 79 area 5 cells showed a change in activity when reaching movements were performed using different arm orientations (ANOVA, P < 0.01). As in PMd and MI, many area 5 cells (56, 71%) showed changes in their tonic discharge before, during, and/or after movement, and 70 cells (89%) showed changes in their response to movement direction (ANOVA, task x direction interaction term, P < 0.01). The observed changes in neuronal activity related to posture and movement in MI, PMd and area 5 demonstrate that single-cell activity in these cortical areas is not simply related to the spatial attributes of hand trajectory but is also strongly influenced by attributes of movement related to arm geometry.

Analysis of Variance↗
PubMed2003

Somatosensory organization and behavior in naked mole-rats I: vibrissa-like body hairs comprise a sensory array that mediates orientation to tactile stimuli.

Orientation guided by mechanosensory stimuli is a fundamental behavior that has been analyzed most effectively in simple systems, but has been difficult to assess in mammals. This study demonstrates that sparsely distributed sensory 'hairs' on the body of naked mole-rats provide an ideal detector array for the assessment of touch guided orienting behavior. Naked mole-rats are fully subterranean rodents that are functionally blind and lack fur. About 40 tactile hairs (resembling facial vibrissae) are found on each side of the body, and they are systematically organized in a grid-like pattern from head to tail. Deflection of a single body hair triggered a highly accurate orientation of the snout toward the point of stimulation, thus topographically organized motor behavior can be elicited from this sensory array. This orienting behavior is specific to the body hair system: touch of intervening skin evoked responses less reliably, and observed responses were not topographically organized. Orientation elicited from this array was accurate regardless of the head-to-body position at the time of hair stimulation indicating that the orienting motor score takes relative head position into account. The consistent pattern of these hairs coupled with robust orienting behavior indicates that this mammalian model provides an appropriately simple system for analyzing the neuronal basis of sensorimotor integration involved in tactile orienting behavior.

Animals↗