Botulin toxins in the treatment of spasmodic torticollis

Hereditary nonpolyposis colorectal cancer (HNPCC) results from an inherited defect in one of the genes responsible for repair of errors that occur during DNA replication. Affected individuals have high risk for cancers of the colon and certain extracolonic sites. It appears that HNPCC patients form adenomas at about the same rate s the general population and there is some circumstantial evidence that adenoma is the precursor to colorectal carcinoma in the syndrome. It is hypothesized that HNPCC features accelerated progression from colonic adenoma to carcinoma, a process theoretically driven by the inability to repair DNA mismatches. Evidence in support of the "Aggressive Adenoma" in HNPCC is provided. We discuss our recommendations for colonoscopic surveillance on an annual basis for HNPCC gene-positive individuals, and for genetic counseling.     

Representation of spatial frequency and orientation in the visual cortex

Knowledge of the response of the primary visual cortex to the various spatial frequencies and orientations in the visual scene should help us understand the principles by which the brain recognizes patterns. Current information about the cortical layout of spatial frequency response is still incomplete because of difficulties in recording and interpreting adequate data. Here, we report results from a study of the cat primary visual cortex in which we employed a new image-analysis method that allows improved separation of signal from noise and that we used to examine the neurooptical response of the primary visual cortex to drifting sine gratings over a range of orientations and spatial frequencies. We found that (i) the optical responses to all orientations and spatial frequencies were well approximated by weighted sums of only two pairs of basis pictures, one pair for orientation and a different pair for spatial frequency; (ii) the weightings of the two pictures in each pair were approximately in quadrature (1/4 cycle apart); and (iii) our spatial frequency data revealed a cortical map that continuously assigns different optimal spatial frequency responses to different cortical locations over the entire spatial frequency range.     

Studies in space orientation: II. Perception of the upright with displaced visual fields and with body tilted.

(This reprinted article originally appeared in Journal of Experimental Psychology, 1948, Vol 38, 455–477. The following abstract of the original article appeared in PA, Vol 23:48.) The S was presented with a small tilted room, on the back wall of which was a rod which he had to adjust to the true upright. In a 1st test, judgments of the rod were obtained with body upright, and under 3 different conditions of the field: (1) The S, standing at a distance from the tilted scene, viewed it through a tube which restricted his view to the interior of the scene. (2) The S stood directly in front of the scene without a tube. (3) The S stood at a distance from the scene. Under all 3 conditions the perceived vertical and horizontal were displaced significantly in the direction of the axes of the tilted scene. When an outer upright field was present, as in the 3rd condition, the effect of the tilted scene upon the perceived upright diminished. In another experiment, judgments of the rod were obtained with body tilted, both to the same side as the field and to the opposite side. It was found that tilting the body resulted in an increased tendency to accept the tilted field as a basis for judging the upright… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of categorization in visual search for orientation.

Visual search for 1 target orientation is fast and virtually independent of set size if all of the distractors are of a single, different orientation. However, in the presence of distractors of several orientations, search can become inefficient and strongly dependent on set size (Exp 1). Search can be inefficient even if only 2 distractor orientations are used and even if those orientations are quite remote from the target orientation (e.g., 20° or even 40° away, Exp 2). Search for 1 orientation among heterogeneous distractor orientations becomes more efficient if the target orientation is the only item possessing a categorical attribute such as steep, shallow (Exp 3), tilted left or tilted right (Exp 4), or simply tilted (Exps 5 and 6). Orientation categories appear to be 1 of several strategies used in visual search for orientation. These serve as a compromise between the limits on parallel visual processing and the demands of a complex visual world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of spatial orientation in infancy.

The ability of infants at 6, 11, and 16 mo to keep track of their relationship to a place in space was assessed in 4 experiments with 72 Ss. Ss were trained to expect an event to occur to their right or left; they were then moved so that their view of the space was reversed. The direction in which they turned in anticipation of the event indicated whether they were coding the location egocentrically or objectively. In Exp I, a longitudinal study of 24 infants, significant shift with age from egocentric responding at 6 and 11 mo to objective responding at 16 mo was revealed, a change that data in Exp II indicated was not simply due to previous experience with the experimental space. In Exps III and IV, manipulation of the type of experience Ss had during training failed to decrease egocentric responding at 6 and 11 mo. The overall pattern indicated that a landmark had its greatest impact at 11 mo. The data support Piaget's theory that in coding location, young infants rely on past accommodations to an object rather than its relationship to other objects or the larger space. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of spatial attention in visual word processing.

Ss made lexical decisions on a target letter string presented above or below fixation. In Exps 1 and 2, target location was cued 100 msec in advance of target onset. Responses were faster on validly than on invalidly cued trials. In Exp 3, the target was sometimes accompanied by irrelevant stimuli on the other side of fixation; in such cases, responses were slowed (a spatial filtering effect). Both cuing and filtering effects on response time were additive with effects of word frequency and lexical status (words vs nonwords). These findings are difficult to reconcile with claims that spatial attention is less involved in processing familiar words than in unfamiliar words and nonwords. The results can be reconciled with a late-selection locus of spatial attention only with difficulty but are easily explained by early selection models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right hemisphere superiority in visual orientation matching.

"Same" or "different" judgments were made by 22 right-handed college students in 2 orientation matching tasks. In 1 task pairs of lines were presented 4. left or right of fixation. Reaction times for both "same" and "different" judgments were faster if stimulus pairs were presented to the left visual field, indicating superiority of the right hemisphere for handling spatial information. In the other task the orientation of a standard line, held in memory, was compared with the orientation of a single test line projected to the left or right of fixation. Results were in the same direction as before, although the right hemisphere superiority was significant only for the "different" responses. Data do not support the idea that "same" and "different" judgments need be differentially lateralized. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of spatial and nonspatial information in visual selection.

Even though it is undisputed that prior information regarding the location of a target affects visual selection, the issue of whether information regarding nonspatial features, such as color and shape, has similar effects has been a matter of debate since the early 1980s. In the study described in this article, measures derived from signal detection theory were used to show that perceptual sensitivity is affected by a top-down set for spatial information but not by a top-down set for nonspatial information. This indicates that knowing where the target singleton is affects perceptual selectivity but that knowing what it is does not help selectivity. Furthermore, perceptual sensitivity can be enhanced by nonspatial features, but only through a process related to bottom-up priming. These findings have important implications for models of visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature asymmetries in visual search: effects of display duration, target eccentricity, orientation and spatial frequency

In Experiments 1-3, we monitored search performance as a function of target eccentricity under display durations that either allowed or precluded eye movements. The display was present either until observers responded, for 104 msec, or for 62 msec. In all three experiments an orientation asymmetry emerged: observers detected a tilted target among vertical distracters more efficiently than a vertical target among vertical distracters. As target eccentricity increased, reaction times and errors augmented, and the set size effect became more pronounced, more so for vertical than tilted targets. In Experiments 4-7, the stimulus spatial properties were manipulated: spatial frequency; size; and orientation. The eccentricity effect was more pronounced for vertical than tilted targets and for high- than low-spatial frequency targets. This effect was eliminated when either the size, the size and orientation, or the size and spatial frequency were magnified (M-cortical factor). By increasing the signal-to-noise ratio, magnification reduced the extent of both asymmetries; it aided more the detection of tilted than vertical and of high- than low-spatial frequency targets. Experiments 4-7 indicate that performance improvement in the magnified conditions was due to the specific pairing of stimulus size with retinal eccentricity and not to the larger stimulus size of the magnified conditions. We conclude that stimulus size, orientation and spatial frequency influence the extent of the eccentricity effect and the efficiency of search performance.     

The retinotopy of visual spatial attention

We used high-field (3T) functional magnetic resonance imaging (fMRI) to label cortical activity due to visual spatial attention, relative to flattened cortical maps of the retinotopy and visual areas from the same human subjects. In the main task, the visual stimulus remained constant, but covert visual spatial attention was varied in both location and load. In each of the extrastriate retinotopic areas, we found MR increases at the representations of the attended target. Similar but smaller increases were found in V1. Decreased MR levels were found in the same cortical locations when attention was directed at retinotopically different locations. In and surrounding area MT+, MR increases were lateralized but not otherwise retinotopic. At the representation of eccentricities central to that of the attended targets, prominent MR decreases occurred during spatial attention.     

Decision processes in visual discrimination of line orientation.

The contribution of decision factors to the meridional variations in line orientation discrimination (OD) was determined for 2-alternative forced-choice experimental designs. With K. O. Johnson's (1980) formalization of decision processes in discrimination tasks, 3 decision factors were identified: decision rule, memory variance, and criterial noise. Exp I (with 13 Ss) showed the effect of experimental design on OD to be similar at horizontal and oblique standard orientations, indicating that the meridional variations in OD were not due to a decision rule anisotropy. In Exp II (with 5 Ss) the effect of the interstimulus interval was also found to be similar at both standard orientations, suggesting that the memory variance is isotropic in the orientation domain. Exps III and IV (with a total of 7 Ss) supported the hypothesis that the meridional variations in OD are not due to a criterial noise anisotropy. Results strongly suggest that the oblique effect in OD is due to sensorial factors rather than to decision factors. Therefore, they further support the hypothesis linking the anisotropy of the preferred orientation distribution of Area 17-S cells (a single physiologically defined class of cells in the primary visual cortex) and the meridional variations in OD. (58 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The computation of orientation statistics from visual texture

This paper examines how observers estimate the overall orientation of spatially disorganised textures containing variable orientation. Experiments used asymmetrical distributions of orientations to separate the predictions from different models of average orientation estimation. Stimuli were composed of two spatially intermingled sets of oriented patches, each set having Gaussian distributed element orientation. The threshold separation of the means of the two sets was determined for a variety of tasks. Discrimination of these textures from a reference composed of two sets with the same mean orientation was well predicted by discrimination of orientation variability. A single interval judgement of which set contained more elements required a greater separation of the set orientations and suggested that the sets must be resolved in the orientation domain for independent representation of their properties. That resolution is required to perform this task further suggests that orientational skew is not coded. Threshold offsets for judgement of average orientation were re-expressed as shifts of four candidate features for coding the central tendency of texel orientations. Comparison with similar thresholds for single distributions of orientations indicated that average orientation is assigned to the centroid of a set of orientation measures.     

Perception of auditory–visual temporal synchrony in human infants.

Using a habituation/test procedure, the author investigated adults' and infants' perception of auditory–visual temporal synchrony. Participants were familiarized with a bouncing green disk and a sound that occurred each time the disk bounced. Then, they were given a series of asynchrony test trials where the sound occurred either before or after the disk bounced. The magnitude of the auditory visual temporal asynchrony threshold differed markedly in adults and infants. The threshold for the detection of asynchrony created by a sound preceding a visible event was 65 ms in adults and 350 ms in infants and for the detection of asynchrony created by a sound following a visible event was 112 ms in adults and 450 ms in infants. Also, infants did not respond to asynchronies that exceeded intervals that yielded reliable discrimination. Infants' perception of auditory–visual temporal unity is guided by a synchrony and an asynchrony window, both of which become narrower in development. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perception and discrimination as a function of stimulus orientation: The "oblique effect" in man and animals.

A review of both behavioral and neurophysiological studies of orientation preferences indicates that performance for a large variety of perceptual tasks is superior for stimuli aligned in horizontal or vertical orientations, as compared to stimuli in oblique orientations. This phenomenon appears in the human adult and child and throughout the animal kingdom. Neurophysiological mechanisms for orientation analysis have been found in the higher visual pathways of many animals, and the suggestive evidence is compelling that these mechanisms underlie the orientation preferences reported behaviorally. Additional methods for determining the cause of these effects are suggested. (11 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Elastic interaction stresses: Part II. The influence of orientation on stresses generated in iso-axial bicrystals

The effects of four types of incompability on stresses generated in seven iso-axial bicrystals of 70-30 alpha brass subjected to tension were examined by finite element methods. The distribution of applied stress and resolved shear stresses was determined. The applied stress, { }, was higher at the interior than at the surface, while the resolved shear stresses were generally higher at the surface. For both applied { } and resolved shear stresses, the largest stresses occurred at the bicrystal boundaries. The effect of end constraints on a [213] oriented single crystal was found to create nonuniform stresses and strains, and an explanation for this behavior was proposed. The effect of orientation on the magnitude of grain boundary resolved shear stress, { }, and the relative extent (volume fraction) of enhanced grain boundary resolved shear stress,V _gb, were determined. The highest values of { } andV _gb were reached in different portions of the stereographic triangle. The elastic interactions producing this behavior were too complex to permit a simple interpretation. TZI-KANG CHEN formerly Graduate Student at Polytechnic University     

Aging and shifts of visual spatial attention.

Three experiments examined adult age differences in the efficiency of endogenous (voluntary) and exogenous (involuntary) attention shifts. Younger and older Ss performed a spatial cuing task in which abruptly onset peripheral cues (Exp 1) or central, symbolic cues (Exps 2 and 3) were presented before a target stimulus at intervals ranging from 50 to 250 msec. With peripheral cues, the magnitude of cuing effects was at least as great for older as for younger adults and followed a similar time course. Similar results were obtained with symbolic cues, although cuing effects for older adults varied with cue difficulty. The results suggest that cue encoding may decline with advancing age but that the efficiency of the shift process is preserved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the spatial distribution of visual attention.

A reanalysis of part of P. Podgorny and R. N. Shepard's (see record 1984-03057-001) data shows that reaction times (RTs) to attended and unattended squares are almost identical when the attended areas are nonunitary and that RTs are related to compactness for unitary attended areas but that this relation breaks down when attention is focused on nonunitary areas. The importance of the actual grid location of probes on RTs is also illustrated. The failure of compactness to reflect these aspects of the spatial nature of attention suggests that this metric is deficient when applied to the study of the spatial determinants of attention. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supramodality effects in visual and haptic spatial processes.

In this article, the authors investigated unimodal and cross-modal processes in spatial working memory. A number of locations had to be memorized within visual or haptic matrices according to different experimental conditions known to be critical in accounting for the effects of perception on imagery. Results reveal that some characteristics of the generated mental image remained strictly inherent to the modality in which information was acquired; in general, accuracy was higher when configurations were visually rather than haptically explored (Experiments 1 and 3). Interestingly, the same pattern emerged when the effects of simultaneous versus sequential processing of the stimuli inherent to vision and haptics were isolated from perceptual modality (Experiment 2). Supramodal elements were also identified (Experiment 3) that were specifically associated to the nature of the cognitive processes, regardless of the original characteristics of the sensory information. These data indicate that both unimodal modality-specific and higher order supramodal mechanisms are simultaneously used in spatial processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mapping conceptual to spatial relations in visual reasoning.

In 3 experiments, the authors investigated the impact of goals and perceptual relations on graph interpretation when people evaluate functional dependencies between continuous variables. Participants made inferences about the relative rate of 2 continuous linear variables (altitude and temperature). The authors varied the assignments of variables to axes, the perceived cause–effect relation between the variables, and the causal status of the variable being queried. The most striking finding was that accuracy was greater when the slope-mapping constraint was honored, which requires that the variable being queried be assigned to the vertical axis, so that steeper lines map to faster changes in the queried variable. The authors propose that graphs provide external instantiations of intermediate mental representations, enabling people to move from visuospatial representations to abstractions through the use of natural mappings between perceptual and conceptual relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)