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PubMed2006

Photonic activation of disulfide bridges achieves oriented protein immobilization on biosensor surfaces.

Photonic induced immobilization is a novel technology that results in spatially oriented and spatially localized covalent coupling of biomolecules onto thiol-reactive surfaces. Immobilization using this technology has been achieved for a wide selection of proteins, such as hydrolytic enzymes (lipases/esterases, lysozyme), proteases (human plasminogen), alkaline phosphatase, immunoglobulins' Fab fragment (e.g., antibody against PSA [prostate specific antigen]), Major Histocompability Complex class I protein, pepsin, and trypsin. The reaction mechanism behind the reported new technology involves "photonic activation of disulfide bridges," i.e., light-induced breakage of disulfide bridges in proteins upon UV illumination of nearby aromatic amino acids, resulting in the formation of free, reactive thiol groups that will form covalent bonds with thiol-reactive surfaces (see Fig. 1). Interestingly, the spatial proximity of aromatic residues and disulfide bridges in proteins has been preserved throughout molecular evolution. The new photonic-induced method for immobilization of proteins preserves the native structural and functional properties of the immobilized protein, avoiding the use of one or more chemical/thermal steps. This technology allows for the creation of spatially oriented as well as spatially defined multiprotein/DNA high-density sensor arrays with spot size of 1 microm or less, and has clear potential for biomedical, bioelectronic, nanotechnology, and therapeutic applications.

Antibodies, Monoclonal↗

PubMed1990

Contrast discrimination cannot explain spatial frequency, orientation or temporal frequency discrimination.

Current models of spatial frequency (SF) and orientation discrimination are based on contrast discrimination data. In these "error propagation" models, the precision of all discrimination tasks is limited by "peripheral" noise in contrast-sensitive channels. Therefore, all discrimination thresholds should be proportional to the contrast Weber fraction delta c/c. To test this prediction, increment thresholds were measured for contrast, SF, orientation and temporal frequency (TF) for contrasts ranging from 2 to 50%. All measurements used the same stimuli, procedures and observers. For contrasts of 2% and higher, the contrast discrimination threshold delta c rises with approximately the 0.6 power of contrast, while SF and TF discrimination are independent of contrast. Furthermore, orientation discrimination is nearly independent of contrast at a SF of 4 cpd. No error-propagation model can explain these results. Therefore, SF and TF discrimination, and orientation discrimination at 4 cpd are limited by contrast-independent central noise.

Contrast Sensitivity↗

PubMed1996

The role of the nucleus in organogenesis: Part 2.

In a previous paper, it was proposed that the spatial orientation of stem cells was dependent on nucleus/nucleus contact. This proposition is discussed in more detail here. The correct spatial orientation of the cells making up the organs of the adult demands a molecular plan of some type to be encoded in the DNA, and it is suggested that the plan is encoded in the nontranscribed DNA. This DNA is present in the form of loops and folds, giving rise to a spatial array of enormous complexity, and the general belief is that the spatial array is dependent on sequence-specific proteins which firmly bind to the DNA. It is proposed that the binding proteins can also join the DNA of two adjacent stem-cell nuclei once nucleus/nucleus contact has been made, and in this way determine the spatial orientation of the future specialized cells. There is enough information encoded in the spatial arrays to correctly position the myriad of cells that make up the adult organism. If cell alignment is carried out by nuclear union, then the development of the neuron can be better understood. It is suggested that malignancy may be due to a fault in either the nontranscribed DNA responsible for spatial orientation or in the sequence-specific binding proteins.

Adult↗

PubMed1992

Binocular processing in the cat's dorsal lateral geniculate nucleus. III. Spatial frequency, orientation, and direction sensitivity of nondominant-eye influences.

The present experiments examined the extent to which binocular processing in the cat's dorsal lateral geniculate nucleus (LGN) depends upon the spatial frequency, orientation, and direction of movement of stimuli presented to the nondominant eye. In Experiment 1, we tested the effects of varying these stimulus parameters on the responses of LGN cells to nondominant-eye stimulation. Sixteen of 34 cells tested had statistically significant responses to the nondominant eye and, in agreement with a previous study (Guido et al. 1989), the responsive cells were spatial-frequency sensitive. However, there was little evidence for orientation or direction sensitivity in responses to the nondominant eye: changes in discharge with changes in stimulus orientation and direction were small and were statistically significant in only nine of the cells. In Experiment 2, we tested the effects of varying spatial frequency, orientation, and direction of movement of stimuli presented to the nondominant eye on its ability to influence responses to the dominant eye (i.e., on binocular interactions). The dominant eye was stimulated with the optimal spatial frequency for the cell being tested. For 22 of 45 cells tested, nondominant-eye stimulation had a statistically significant effect on the response to the dominant eye. Fourteen of these cells showed band-pass spatial-frequency sensitivity in the nondominant-eye influence, and eight showed low-pass spatial-frequency sensitivity. However, only 11 of the cells had statistically significant variations in their binocular interactions that depended on the orientation or direction of stimuli presented to the nondominant eye. Furthermore, even for those cells, the effect of varying orientation and direction was only about half as strong as the effect of varying spatial frequency. We conclude that binocular processing in the LGN, including responses to the nondominant eye and nondominant-eye influences on responses to the dominant eye, are affected significantly by the spatial frequency of the nondominant-eye stimulus and relatively little by stimulus orientation or direction of movement. The significance of these findings for understanding the functions of LGN binocular processing is discussed.

Analysis of Variance↗

PubMed1998

Relationship between selected orientation rest frame, circular vection and space motion sickness.

Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration.

Adult↗

PubMed1988

Geometry or not geometry? Perceived orientation and spatial layout in pictures viewed at an angle.

Cutting (1988) suggests that changes in the perceived orientations of pictured objects that occur with changes in viewing angle are caused by the geometrical changes that accompany these changes in viewing angle. His geometrical analysis does predict the differential rotation effect reported by Goldstein (1979, 1987), but fails to predict other important aspects of the data. Cutting's analysis does, however, support Goldstein's (1987) conclusion that in future research on picture perception it is important to clearly distinguish between the attributes of perceived orientation and spatial layout.

Depth Perception↗

PubMed1990

An analysis of neural spike-train distributions: determinants of the response of visual cortex neurons to changes in orientation and spatial frequency.

A previously unexploited method of examining neural spike-trains was applied to data obtained from cells in the visual cortex. Distributions of interspike intervals recorded extracellularly from cat visual cortex under four conditions were analyzed. Stimuli were gratings differing in orientation and spatial frequency. The probability density function of first passage time for a random walk with drift process, which is defined by its barrier height and drift coefficient, was used to characterize the generating process of axonal discharge under resting and stimulus conditions. Drift coefficient and barrier height were derived from the sample mean and standard deviation of the measured inter-spike intervals. For cells with simple receptive fields, variations in the drift coefficient were produced by changes in orientation and spatial frequency. Variations in barrier height were produced only by changes in orientation of the stimulus.

Animals↗

PubMed2006

Alerting and orienting in Alzheimer's disease.

Recently, researchers (E. Festa-Martino, B. R. Ott, & W. C. Heindel, 2004; A. Tales, J. L. Muir, A. Bayer, R. Jones, & R. J. Snowden, 2002; A. Tales, J. L. Muir, A. Bayer, & R. J. Snowden, 2002 have found significantly abnormal spatial orienting together with the abolishment of the alerting effect in Alzheimer's disease (AD). However, these research groups differed in their interpretation of the results. A. Tales, J. L. Muir, A. Bayer, R. Jones, and R. J. Snowden (2002) and A. Tales, J. L. Muir, A. Bayer, and R. J. Snowden (2002) explained their data in terms of two independent processes, whereas E. Festa-Martino et al. (2004) interpreted their findings as indicative of an inverse association, namely that the increased spatial orienting effect in AD was the direct result of the abolition of the phasic alerting effect. In this further study examining exogenous spatial orienting and phasic alerting, the authors present evidence to suggest that the increased spatial orienting effect in AD is not the result of a decreased phasic alerting effect.

Aged↗

PubMed1984

The effects of large orientation and spatial frequency differences on spatial discriminations.

We have examined two questions: (1) can the finest orientation discrimination be achieved only between stimuli with similar spatial frequency content? and likewise, (2) can the lowest spatial frequency discrimination thresholds be achieved only with parallel gratings? In 2 AFC tests we found that neither type of discrimination was affected by stimulus differences along the other dimension. However, some small decreases in method of adjustment matching accuracy were associated with large differences along the secondary dimensions. Considering the neurophysiological implications, these data suggest that fine orientation and spatial frequency discrimination can occur even though separate populations of neurones in the primary visual cortex may be activated by the two stimuli to be discriminated.

Discrimination, Psychological↗

PubMed2000

Sensitivity to contrast modulation depends on carrier spatial frequency and orientation.

We consider how the detection of second-order contrast structure depends on the orientation and spatial frequency of first-order luminance structure. For patterns composed of a bandpass noise carrier multiplied by a contrast envelope function, we show that sensitivity to the envelope varies in proportion to the spatial frequency of the carrier. For oriented carriers at low spatial-frequencies, detection of the contrast envelope is easier when the envelope and carrier are perpendicular, but this dependency diminishes as the spatial frequency of the carrier increases. These differences are not attributable to either the detection of side-bands, or the presence of spurious contrast structure in unmodulated carrier images. A final experiment measured envelope detection in the presence of noise masks. Results indicate that orientationally and spatially-band pass filtering precedes the detection of second-order structure.

Contrast Sensitivity↗

PubMed1983

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Rats with lesions of the medial frontal, orbital frontal, or parietal cortex were compared behaviorally with rats with complete removal of the neocortex and normal control rats on three spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all three tasks, thus providing a measure against which to compare the severity of the impairments observed following more restricted removals. Rats with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, rats with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were very poor at learning the water task. Rats with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate rats. The results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, the results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital (sulcal) frontal cortex play a dissociable role in the control of spatial orientation.

Animals↗

PubMed1982

Correlation between the preferred orientation and spatial frequency of neurones in visual areas 17 and 18 of the cat.

1. In seventy-six penetrations through areas 17 and 18 of the cat, neurones were regularly sampled at intervals of 100 micrometers and preferred orientation, optimal spatial frequency and resolving power were determined for each neurone in response to drifting sinusoidal gratings. 2. As already shown for area 17, in tangential penetrations through area 18, whenever the preferred orientation rotates progressively from cell to cell, the optimal spatial frequency tends to remain constant. 3. A statistical analysis on 1574 cells in areas 17 and 18 showed that for pairs of cells separated 200-300 micrometers along a track the difference in preferred orientation delta alpha and the difference in optimal spatial frequency delta f are not randomly distributed: cell pairs with small delta alpha are most likely to have large delta f and vice versa. 4. These findings indicate that in areas 17 and 18 neurones with the same optimal frequency are aligned along a direction orthogonal to the orientation columns. 5. The optimal spatial frequency, resolving power and the velocity cut-off were averaged for cells from different penetrations located in the same cortical layer or sublayer of area 18: mean optimal spatial frequency and acuity are highest in layer IV and lowest in layers II and V, while the velocity cut-off is highest in layers II and V and lowest in layer IV. 6. Our data suggest that the layering of cells according to optimal spatial frequency is a more subtle subdivision than the six histological layers.

Action Potentials↗

PubMed2001

Tuning for the orientation of spatial attention in dorsal premotor cortex.

We tested whether neuronal activity in the dorsal premotor cortex (PMd) reflected the orientation of selective spatial attention, as opposed to the target of a reaching movement, eye position and saccade direction. These four spatial variables were dissociated in two tasks, which both required that a monkey attend to a robot's location in order to know when to make a movement. However, the target of the reaching movement varied; it was the robot's location in one task, but a different location in the other task. Eye position was recorded, but not explicitly controlled. Of 199 PMd neurons sampled, 19% had activity related to eye position, and an overlapping 11% were related to saccade direction (totaling 24% of the PMd sample). Of the 152 PMd neurons that lacked oculomotor relationships, approximately 20% reflected the orientation of selective spatial attention. Attentional tuning may account, at least in part, for gaze-independent receptive fields and visuospatial, target or goal relationships in tasks involving stimulus-response incompatibility.

Animals↗

PubMed1984

Distribution of action potential durations in the canine left ventricle.

The distribution of action potential durations (APD) in the left ventricle were investigated and compared to the spatial orientation of the maximum T vector (MaxTv). Eight dogs with similar vectorcardiographic spatial orientations of MaxTv were used. Action potentials were recorded from 42 to 64 sites on each isolated endocardial and epicardial specimen with glass microelectrodes. Preparations included the entire left ventricular free wall. The APD50 and APD90 had similar distributions, but the APD90 distribution was less uniform in all 8 dogs. On the endocardium, APDs were longest between the roots of the papillary muscles, and progressively shorter toward the upper edge (base) where the shortest APDs were found. On the epicardium, APDs were longest in the lower lateral region, and gradually shortened, approximately concentrically, toward the anterior and posterior bases. APDs were longer in the endocardium than in the corresponding epicardium. Maximum APD endocardial-epicardial differences were found in the lower lateral region of the ventricular free wall. Results agree with reports of ventricular recovery properties in vivo, and partly account for the spatial orientation of the MaxTv. This study adds new details, and delineates the longest and shortest distributions of APDs.

Action Potentials↗

PubMed1979

Angle-matching illusions and perceived line orientation.

Spatial illusions which occur in angle-matching tasks were examined in six experiments using two different kinds of display. In experiments 1 and 2 illusory errors generally were in the direction predicted by Lennie's hypothesis which states that angle arms are attracted perceptually towards the oblique axes of space, although the display used in these experiments differed from Lennie's. However, experiment 3 showed that these errors might equally be explained by the addition of interactive effects between angle arms (tilt illusions). Parametric investigation of Lennie's figures (experiments 4 and 5) showed that thelargest angular illusion occurred with the largest angle used (45 degrees) and an intermediate line length (2 deg 7 min). These angular illusions were not explicable by the addition of tilt illusions (experiment 6), suggesting that different judgmental processes may underlie orientation and angle estimation.

Discrimination Learning↗

PubMed1998

Representation of orientation and spatial frequency in perception and memory: a choice reaction-time analysis.

Discrimination and short-term memory for the orientation of sinusoidal gratings that differed in spatial frequency, and for the spatial frequency of gratings that differed in orientation, were measured in a same-different task with 0-10 s interstimulus intervals (ISI) between test and reference stimuli. Introducing a difference between test and reference stimuli on a second dimension, or increasing ISI, did not impair spatial discrimination in terms of accuracy, but choice reaction times for correct decisions were prolonged by both manipulations. Results suggest that perceptual discrimination is based on representations in which orientation and spatial frequency are conjointly coded and that decisions are reached by a serial process scanning multiple-tuned, labeled channels; short-term memory may involve reactivation of these channels.

Analysis of Variance↗

PubMed2006

Presentation modality influences behavioral measures of alerting, orienting, and executive control.

The Attention Network Test (ANT) uses visual stimuli to separately assess the attentional skills of alerting (improved performance following a warning cue), spatial orienting (an additional benefit when the warning cue also cues target location), and executive control (impaired performance when a target stimulus contains conflicting information). This study contrasted performance on auditory and visual versions of the ANT to determine whether the measures it obtains are influenced by presentation modality. Forty healthy volunteers completed both auditory and visual tests. Reaction-time measures of executive control were of a similar magnitude and significantly correlated, suggesting that executive control might be a supramodal resource. Measures of alerting were also comparable across tasks. In contrast, spatial-orienting benefits were obtained only in the visual task. Auditory spatial cues did not improve response times to auditory targets presented at the cued location. The different spatial-orienting measures could reflect either separate orienting resources for each perceptual modality, or an interaction between a supramodal orienting resource and modality-specific perceptual processing.

Adult↗

PubMed1990

Visuospatial orientation in Parkinson's disease.

Visuospatial functioning in patients with Parkinson's disease was investigated using neuropsychological measures of basic visual perception, complex perceptual discrimination, and spatial orientation. Three subgroups of patients were described: (a) those with broadly impaired visuospatial abilities, (b) those with generally intact abilities, and (c) those whose performance on a task of spatial orientation was lower than their performance on a task of complex perceptual discrimination. These subgroup differences were also concordant with three other variables: age, duration of disease, and degree of dementia. It is suggested that decreases in spatial orientation functioning in Parkinson's disease may reflect the speed of progression of this disease.

Adult↗