A bibliometric study on trends in chiropractic research from 1920 to 2023.

OBJECTIVE: An increasing body of evidence suggests a positive role of chiropractic in the treatment of neuro-musculoskeletal disorders. This study aims to explore current research hotspots and trends, providing insights into the broad prospects of this field. METHODS: A bibliometric review was conducted on all chiropractic articles included in the Web of Science Core Collection before December 31, 2023. RESULTS: Over the past century, the volume of research in the field of chiropractic has been fluctuating annually, with four peaks observed in total. The United States, Canada, Australia, and the United Kingdom are leading countries. Chu, Eric Chun-Pu is the author with the most publications, while Bronfort, Gert has the highest total citation count. The University of Southern Denmark has produced the most publications, while Queens University - Canada is the most central institution. The Journal of Manipulative and Physiological Therapeutics is the journal with the most publications and citations, while the Journal of the American Medical Association is the most central journal. The two most-cited articles were both authored by Eisenberg DM. Emerging keywords include "chronic pain" and "skills". The theoretical mechanisms and scientific basis of chiropractic, its clinical practice and safety, education and training, integration with other disciplines, and patient experiences and satisfaction are the frontiers and hotspots of research. CONCLUSION: This study integrates bibliometric analysis to summarize the current state of research and global network centers in the field of chiropractic, further highlighting the hotspots and trends in this field. However, Individual and national rankings should be interpreted with caution due to our focus on Web of Science rather than PubMed.

Altered brain activities in mesocorticolimbic pathway in primary dysmenorrhea patients of long-term menstrual pain.

Background: Patients with primary dysmenorrhea (PDM) often present with abnormalities other than dysmenorrhea including co-occurrence with other chronic pain conditions and central sensitization. Changes in brain activity in PDM have been demonstrated; however, the results are not consistent. Herein, this study probed into altered intraregional and interregional brain activity in patients with PDM and expounded more findings. Methods: A total of 33 patients with PDM and 36 healthy controls (HCs) were recruited and underwent a resting-state functional magnetic resonance imaging scan. Regional homogeneity (ReHo) and mean amplitude of low-frequency fluctuation (mALFF) analysis were applied to compare the difference in intraregional brain activity between the two groups, and the regions with ReHo and mALFF group differences were used as seeds for functional connectivity (FC) analysis to explore the difference of interregional activity. Pearson's correlation analysis was conducted between rs-fMRI data and clinical symptoms in patients with PDM. Results: Compared with HCs, patients with PDM showed altered intraregional activity in a series of brain regions, including the hippocampus, the temporal pole superior temporal gyrus, the nucleus accumbens, the pregenual anterior cingulate cortex, the cerebellum_8, the middle temporal gyrus, the inferior temporal gyrus, the rolandic operculum, the postcentral gyrus and the middle frontal gyrus (MFG), and altered interregional FC mainly between regions of the mesocorticolimbic pathway and regions associated with sensation and movement. The anxiety symptoms are correlated with the intraregional activity of the right temporal pole superior temporal gyrus and FC between MFG and superior frontal gyrus. Conclusion: Our study showed a more comprehensive method to explore changes in brain activity in PDM. We found that the mesocorticolimbic pathway might play a key role in the chronic transformation of pain in PDM. We, therefore, speculate that the modulation of the mesocorticolimbic pathway may be a potential novel therapeutic mechanism for PDM.

Abnormal interhemispheric functional connectivity in patients with primary dysmenorrhea: a resting-state functional MRI study.

Background: Neuroimaging studies have confirmed that functional connectivity (FC) disruption of pain-related brain networks may contribute to the cerebral pathophysiology of primary dysmenorrhea (PDM). However, it remains unclear whether FC of symmetrical regions of bilateral hemispheres associated with PDM is abnormal. This functional MRI study aimed to explore the changes of voxel-mirrored homotopic connectivity (VMHC) and seed-based FC in patients with PDM. Methods: A cohort comprising patients with PDM (n=35) and healthy controls (HCs) (n=41) underwent resting-state functional MRI scans during their menstrual phase. Interhemispheric FC was compared between the two groups using VMHC analysis. Brain areas with significant group differences in VMHC were selected as seed regions for FC analysis. Correlation analysis was also conducted to examine the relationship between abnormal connectivity of brain regions and clinical measures of pain and anxiety. Results: Compared with healthy individuals, patients with PDM showed significantly enhanced VMHC in the bilateral orbital part of the superior frontal gyrus and the bilateral middle frontal gyrus. Subsequent seed-based FC analysis showed enhanced connectivity between the aforementioned areas and pain-related brain structures. Hyperconnectivity between the left middle frontal gyrus and the right cingulate gyrus in patients was negatively correlated with an increase in the visual analogue score (VAS) for pain (r=-0.341, P<0.05). Conclusions: Our findings indicate that ongoing dysmenorrhea is accompanied by abnormal interhemispheric functional coordination and enhanced connectivity in pain-related regions, attention networks, and the reward system. These findings may provide a novel perspective on the central mechanism of pain caused by PDM.

[Effect of oblique needling at Ashi-point on expression of MyoD1/Pax7 in mice with quadriceps femoris injury].

OBJECTIVE: To observe the effect of oblique needling at Ashi-point on behavior, and cell morphology, myogenic differentiation antigen (MyoD1) and paired box transcription factor Pax7 (Pax7) of quadriceps femoris tissue in quadriceps femoris injured mice. METHODS: A total of 24 C57BL/6 male mice were randomly divided into control, model, shallow insertion and deep insertion groups, with 6 mice in each group. The quadriceps femoris injury model was established by single intramuscular injection of 0.5% bupivacaine (BPVC). Twenty-four hours after modeling, mice of the two acupuncture groups were received oblique needling on the surface or through the muscle belly of quadriceps femoris for once, the oblique needling was lifted and inserted 3 times. The climbing pole test was conducted 24 h after modeling and 24 h after EA. Histopathological changes of quadriceps femoris was observed by H.E. staining. The expressions of MyoD1 and Pax7 were detected by immunohistochemistry. RESULTS: Compared with the control group, the score of climbing pole test was lower (P<0.01), and the expressions of MyoD1 and Pax7 significantly increased (P<0.01) in the model group. After the intervention and compared with the model group, the score of climbing pole test was higher (P<0.01), and the expressions of MyoD1 and Pax7 obviously increased (P<0.01) in the two acupuncture groups. The therapeutic effect of deep insertion group was apparently superior to that of shallow insertion group in up-regulating the climbing pole test score and expressions of MyoD1 and Pax7 (P<0.05, P<0.01). H.E. stain showed large areas of inflammatory infiltration, muscle cells swelling, atrophy, rupture, degeneration and necrosis, different cell sizes and morphologies, enlarged intervals, nuclear aggregation, deep nuclear staining, nuclear pyknosis, and hemorrhage in the model group, which was relatively milder in both needling groups. CONCLUSION: Oblique needling at Ashi-point can effectively promote the benign repair of injured quadriceps muscle and promote the recovery of exercise ability in mice, which may be associated with its effect in up-regulating the expression of MyoD1 and Pax7 protein. The role of deep insertion is superior to that of shallow insertion.

Needling on trigger point promotes muscle regeneration after bupivacaine injection induced injury.

Dry needling treatment has a promising relieving effect on Myofascial Pain Syndrome (MPS). In China, acupuncture practitioners use acupuncture needle instead to insert the "A-Shi" acupoint to treat MPS which is defined as the same as the trigger point of dry needling. This method has been applied for thousands of years in China. In this study, bupivacaine injection induced gastrocnemius muscle injury in mice. We applied the clinical improved needling method on animal model by making the angle between the skin and needle less than 30 degree. Animals got needling treatment 24 h later at the point where the bupivacaine was injected. Results of muscle H.E. staining showed that, compared to bupivacaine injection group without needling, acupuncture treatment group showed more intact muscle fibers, less inflammatory cell infiltration and fractured muscle fibers. By RNA sequencing analysis, our work firstly demonstrated that the physical stimulation of needling changed the gene expression of muscle tissue to accelerate the muscular regeneration process. Therefore, our study proved that simple needling at "A-Shi" acupoint promoted muscle regeneration and revealed underlying mechanisms of the beneficial effects of acupuncture and dry needle treatments.

[Comparison of therapeutic effect of soft-tissue relaxing needling and electroacupuncture for knee osteoarthritis].

OBJECTIVE: To compare the clinical efficacy of soft-tissue relaxing needling and electroacupuncture (EA) in the treatment of knee osteoarthritis (KOA), so as to explore a new and more effective therapy for KOA. METHODS: Forty patients with KOA who met our diagnostic criteria were randomly and equally divided into acupuncture group and soft-tissue relaxing needling (relaxing-needling) group. EA (20 Hz, a tolerable strength and duration of 20 min) was applied to the unilateral Neixiyan(EX-LE5) and Waixiyan(EX-LE5), and manual acupuncture stimulation was applied to Heding(EX-LE2), Xuehai (SP10), Xiyangguan (GB33), Liangqiu(ST34), Yanglingquan(GB34) and Yinlingquan(SP9) on the affected side by using uniform reinforcing-reducing technique. In the relaxing-needling group, after identifying the tender point and nodule-like or stiff-strip-muscle spot at the affected limb by palpation, we used filiform needles to insert into them, then, made a longitudinal separation or point-like pricking. The visual analog scale (VAS) pain score, knee flexion activity (range of motion, ROM), and the knee osteoarthritis severity (Lequesne index, composed of daily living, walking distance and pain) were measured before and after the treatment. The therapeutic effect was assessed by consulting the Guiding Principles for Researching New Drugs of Traditional Chinese Medicine (2002) and Criteria for Diagnosis and Assessment of Therapeutic Effect of Syndromes or Illnesses of Traditional Chinese Medicine (1994). RESULTS: After the treatment, the VAS score and Lequesne index were significantly decreased in both acupuncture and relaxing-needling groups (P<0.001), and the ROM score was considerably increased in both groups in comparison with their own pre-treatment (P<0.001). The difference values of VAS score and Lequesne index between pre- and post-treatment were significantly higher in the relaxing-needling group than in the acupuncture group (P<0.05). Of the two 20 cases in the relaxing-needling and acupuncture groups, 8 and 3 experienced a remarkable improvement in their symptoms, 10 and 13 were effective, 2 and 4 failed, with the effective rate being 90.0% and 80.0%, respectively. No significant difference was found between the two groups in the difference value of ROM score and the effective rate (P>0.05)．. CONCLUSION: Both relaxing-needling and EA therapies are comparable in the therapeutic effect for KOA, and the former is superior to the latter in reducing the joint pain and improving the knee joint locomotor function, thus being worthy of clinical application.

Dipole analysis of the influence of linear arrays of points on visually perceived eye level (VPEL).

Previous research has shown that a visual field consisting of as little as one peripherally located luminous line that is pitched from vertical in a dark field induces large changes in an observer's visually perceived eye level (VPEL). The effects of this severely reduced inducing stimulus are surprisingly close to the effects of a highly structured pitched visual field. In the present report we describe two experiments with inducing stimuli that were still further reduced to one or two linear arrays of points of light. The results show that the array's effect on VPEL increases as a negatively accelerated increasing function of the amount of stimulus (i.e., the length of the array, the number of points, and the interpoint separation). We propose a multiscale dipole model (MDM), which quantifies the effect of the array of points on VPEL in terms of dipoles of various lengths that activate orientation and size specific neurons in visual cortex. For example, when the number of points increases in an array of fixed length, dipoles of progressively shorter length are created within the overall length of the stimulus. The shorter dipoles stimulate additional orientation-selective neurons with smaller receptive fields whose neural activity adds to the activity generated by the larger dipoles up to a saturation limit. The functional relation between the psychophysical response and the number of dipoles can be modeled as a rectangular hyperbola, formally similar to equations that have been used to model saturation binding and enzyme velocity in biochemistry and contrast response functions in neurophysiology and psychophysics.

[The effect of acupuncture stimulation of Ashi-point on hepatocyte growth factor expression in the soft tissue in acute contusion rats].

OBJECTIVE: To observe the effect of acupuncture stimulation of Ashi-point on hepatocyte growth factor (HGF) protein expression in gastrocnemius muscle (GM) in rats with traumatic injury of GM, so as to reveal its mechanism underlying improvement of traumatic injury of skeletal muscle. METHODS: A total of 80 SD rats were randomly divided into normal control (n = 8), model, acupuncture control, and acupuncture treatment groups, and the latter 3 groups were further allocated to 0 h, 24 h and 48 h subgroups (n = 8 in each subgroup). The acute soft tissue contusion model was established by using 500 g-counterweight free falling hitting at the GM of the right leg (height 30 cm). The Ashi-point was punctured with a piece of filiform needle by penetrating the site beside the injured GM, and stimulated for about 5 seconds. For acupuncture control group, acupuncture was performed in the same Ashi-point in normal rats. Pathological changes of the focal GM were observed by H. E. staining and HGF protein expression of GM was detected by Western blot. RESULTS: H.E. staining showed that different degrees of injury of GM tissue including broken muscle fibers with cellular swelling, inflammatory cell infiltration, muscle fibrinolysis, atrophy, degeneration and necrosis, etc., were found at each time-point after modeling, while in the acupuncture treatment group, the severity of muscle injury was relatively milder particularly at the time-points of 24 h and 48 h. Compared with the normal control group, HGF protein expression levels of GM at the 3 time-points in the model group, and at 48 h in the acupuncture control group were markedly increased (P<0.05, P<0.01); while in comparison with the model group, HGF protein expression levels were remarkably down-regulated at 24 h and 48 h after acupuncture treatment (P<0.01, P<0.05). CONCLUSION: Acupuncture stimulation of Ashi-point can significantly down-regulate HGF protein expression in the GM in soft tissue contusion rats, which may contribute to its effects in relieving contusion injury of skeletal muscle.

Individual differences in perceived elevation and verticality: evidence of a common visual process.

Thel frontoparallel orientation of a long peripheral line influences two visual norms, elevation, also called the visual perception of eye level (VPEL), and orientation in the frontoparallel plane, called visually perceived vertical (VPV). However, VPEL and VPV are distinct in that different integration rules describe the combinatorial effects of two lines symmetrically located on opposite sides of the median plane. Nevertheless, we propose that the same orientation-sensitive process underlies the two discriminations. We measured the two norms while we manipulated visual orientation with 1-line and 2-line stimuli (on opposite sides of the median plane), then modeled the large and significant effect of line orientation on VPEL and VPV settings as linear averages of signals from vision and from non-visual, body-referenced, vestibular and proprioceptive mechanisms. Significant correlations are evident between observers (n = 30) in the effect of visual orientation on both VPEL and VPV, and in the baseline measures (dark value, intercept) on both norms. The latter egocentric bias is further discussed in the context of the operation of the body-referenced mechanism across different egocentric discriminations for an individual subject. Given the evidence for different integration rules, the pattern of individual co-variation implies the existence of a single, shared visual orientation process that feeds to separate integration processes.

Short-lived effects of a visual inducer during egocentric space perception and manual behavior.

A pitched visual inducer has a strong effect on the visually perceived elevation of a target in extrapersonal space, and also on the elevation of the arm when a subject points with an unseen arm to the target's elevation. The manual effect is a systematic function of hand-to-body distance (Li and Matin Vision Research 45:533-550, 2005): When the arm is fully extended, manual responses to perceptually mislocalized luminous targets are veridical; when the arm is close to the body, gross matching errors occur. In the present experiments, we measured this hand-to-body distance effect during the presence of a pitched visual inducer and after inducer offset, using three values of hand-to-body distance (0, 40, and 70 cm) and two open-loop tasks (pointing to the perceived elevation of a target at true eye level and setting the height of the arm to match the elevation). We also measured manual behavior when subjects were instructed to point horizontally under induction and after inducer offset (no visual target at any time). In all cases, the hand-to-body distance effect disappeared shortly after inducer offset. We suggest that the rapid disappearance of the distance effect is a manifestation of processes in the dorsal visual stream that are involved in updating short-lived representations of the arm in egocentric visual perception and manual behavior.

[Effects of electroacupuncture and manual acupuncture interventions on contents of serum inflammatory cytokines in rats with chronic adjuvant arthritis].

OBJECTIVE: To observe the effect of electroacupuncture (EA) or manual acupuncture of unilateral or bilateral "Zusanli" (ST 36) on the contents of serum inflammatory factors interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), and anti-inflammatory factors interleukin 2 (IL-2), interleukin 4 (IL-4) and interleukin 10 (IL-10), so as to reveal their mechanism underlying improvement of chronic arthritis. METHODS: Sixty SD rats were randomly divided into normal control, model, electroacupuncture (EA)-left (L) Zusanli (ST 36), EA-bilateral (Bi)-ST 36,and manual acupuncture (MA)-L-ST 36 groups (12 rats/group). Arthritis model was established by subcutaneous injection of complete Freund's adjuvant (0.1 mL)into the hindpaw. EA (2 Hz/100 Hz, 1-3 mA, pulse duration: 0.6 ms/0.2 ms) or manual needle stimulation was applied to the left or bilateral "Zusanli" (ST 36) for 30 min, twice every week for 4 weeks. Enzyme linked immunosorbent assay (ELISA) was used to detect the contents of serum IL-1beta, TNF-alpha, IL-2, IL-4 and IL-10, respectively. RESULTS: Compared with the normal control group, the contents of serum inflammatory factors IL-1beta and TNF-alpha, anti-inflammatory factors IL-4 and IL-10 were increased significantly in the model group (P < 0.001). In comparison with the model group, serum IL-1beta, TNF-alpha, IL-4 and IL-10 contents were down-regulated considerably in the EA-L-ST 36, EA-Bi-ST 36 and MA-L-ST 36 groups (P < 0.001, P < 0.005). Serum IL-2 content had no apparent changes after modeling in comparison with the normal group (P > 0.05). While serum IL-2 contents were markedly higher in the EA-L-ST 36, EA-Bi-ST 36 and MA-L-ST 36 groups than in the model group (P < 0.05). No significant differences were found among the EA-L-ST 36, EA-Bi-ST 36 and MA-L-ST 36 groups in serum IL-1beta, TNF-alpha, IL-2, IL-4 and IL-10 contents (P > 0.05). CONCLUSION: EA or manual acupuncture stimulation of single or bilateral ST 36 can effectively down-regulate serum inflammatory factors IL-1beta and TNF-alpha levels, and upregulate anti-inflammatory factor IL-2 level in chronic arthritis rats, which may contribute to their effects in relieving chronic arthritis.

[Effect of electroacupuncture on hippocampal NO-cGMP signaling pathway in depression rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on hippocampal nitric oxide (NO)-cyclic guanosine 3,5-monophosphate (cGMP) signaling pathway in depression rats in order to explore the underlying mechanism of EA in improving depression. METHODS: Thirty male SD rats were equally randomized into control, model and EA groups. Depression model was established by using chronic unpredictable mild stress stimulation (forced ice-water swimming, electric shock, tail-clamping, etc.) combined with lonely raising for 21 days. EA (2 Hz, 0.6 mA, 20 min) was applied to "Baihui" (GV 20) and "Yintang" (EX-HN 3), once daily for 21 days. The expression of neuronal nitric oxide synthase (nNOS) and the content of cGMP in the hippocampus were determined by immuno-histochemistry and radioimmunoassay separately. RESULTS: Many nNOS immuno-reaction (IR)-positive granular cells were observed in the hippocampus in control group, fewer found in EA group and fewest in model group. Image analysis showed that the grey value of model group was significantly higher than that of control group (P < 0.01), and that of EA group was obviously lower than that of model group (P < 0.01), suggesting upregulation of nNOS expression after EA. Compared with control group the content of cGMP in hippocampus in model group showed a decreasing trend, but without significant difference between two groups (P > 0.05). In comparison with model group, hippocampal cGMP content of EA group increased considerably (P < 0.01), being comparable to that of control group (P > 0.05). CONCLUSION: Electroacupuncture of "Baihui" (GV 20) and "Yintang" (EX-HN 3) can upregulate the expression of nNOS and the content of cGMP in the hippocampus in depression rats, maintaining a normal activity of the NO/cGMP signaling pathway, which may contribute to its effect in relieving depression.

Binocular spatial induction for the perception of depth does not cross the midline.

Although horizontal binocular retinal disparity between images in the two eyes resulting from their different views of the world has long been the centerpiece for understanding the unique characteristics of stereovision, it does not suffice to explain many binocular phenomena. Binocular depth contrast (BDC), the induction of an appearance of visual pitch in a centrally located line by pitched-from-vertical flanking lines, has particularly been the subject of a good deal of attention in this regard. In the present article, we show that BDC does not cross the median plane but is restricted to the side of the visual field containing a unilateral inducer. These results cannot be explained by the use of retinal disparity alone or in combination with any additional factors or processes previously suggested to account for stereovision. We present a two-channel three-stage neuromathematical model that accounts quantitatively for present and previous BDC results and also accounts for a large number of the most prominent features of binocular pitch perception: Stage 1 of the differencing channel obtains the difference between the retinal orientations of the images in the two eyes separately for the inducer and the test line; stage 1 of the summing channel obtains the corresponding sums. Signals from inducer and test stimuli are combined linearly in each channel in stage 2, and in stage 3 the outputs from the two channels are combined along with a bias signal from the body-referenced mechanism to yield ', the model's prediction for the perception of pitch.

A tilted frame deceives the eye and the hand.

A roll-tilted visual frame induced a vertical line to appear roll-tilted in the opposite direction (rod-and-frame illusion). This visual illusion was measured by finding the physical roll-tilt of the line that appeared vertical-visually perceived vertical (VPV). In separate measurements, the roll-tilted visual frame was also found to induce an illusion in the felt orientation of the hand. This manual illusion was measured by setting the orientation of the hand to feel vertical in the presence of the inducing frame (manually perceived vertical-MPV), with distance of the hand from the body as a parameter. The manual illusion was large when the hand/arm was fully extended (60 cm from the body). When the hand was close to the body (in the midfrontal plane), there was no manual illusion. In a third set of measurements, subjects matched the roll-tilt of the hand to a line set by the experimenter to the subject's VPV or to VPV +/- 5 degrees . These manual/visual matches (MVM) were accurate at 60 cm-the distance at which the manual illusion was greatest. In effect, the large manual illusion at this distance tended to compensate for the visual illusion when the subject matched the orientation of the hand to the VPV. However, when the hand was close to the body, where there was no manual illusion, the manual/visual match was poor (no manual illusion to compensate for the visual illusion). The results are discussed in terms of a proximal/distal model that employs a linear weighted sum of influences from body-referenced and visual mechanisms. The model accounts for 61% of the MVM in terms of the inducer's effect on MPV. Considered in isolation, the gross VPV errors in conjunction with the accurate MVM settings with the extended arm might appear to support a theory based on perception/action dissociation. However, that theory cannot explain the dramatic effects of hand-to-body distance. The present results are very similar to those previously reported for the dimension of elevation where hand-to-body distance dependence was also found to modulate visually guided manual behavior.

The field dependence/independence cognitive style does not control the spatial perception of elevation.

Earlier work described the presence of a significant connection between an individual's ability to disregard distracting aspects of a visual field in the classical rod-and-frame test (RFT), in which a subject is required to set a rod so that it will appear vertical in the presence of a square frame that is roll tilted from vertical, and in paper-and-pencil tests, in which the subject is required to find a hidden figure embedded in a more complex figure (the Embedded Figures Test [EFT]; see, e.g., Witkin, Dyk, Faterson, Goodenough, & Karp, 1962; Witkin et al., 1954; Witkin, Oltman, Raskin, & Karp, 1971). This has led to a belief in the existence of a bipolar dimension of cognitive style that is utilized in such disembedding tasks--namely, the extent to which an individual is dependent on or independent from the influence of a distracting visual field. The influence of an inducing visual field on the perception of elevation measured by the setting of a visual target to appear at eye level (the visually perceived eye level [VPEL] discrimination) has also been found to be correlated with the RFT. We have thus explored the possible involvement of the dependence/independence cognitive style on the VPEL discrimination. Measurements were made on each of 18 subjects (9 of them female, 9 male) setting a small target to the VPEL in the presence of a pitched visual field across a range of six pitches from -30 degrees (topbackward) to +20 degrees (topforward) and on each of three tests generally recognized as tests of cognitive spatial abilities: the EFT, the Gestalt Completion Test, and the Snowy Pictures Test (SPT). Although there were significant pairwise correlations relating performance on the three cognitive tests (+.73, +.48, and +.71), the correlation of each of these three with the slope of the VPEL-versus-pitch function was not significant, as it was with the slope of the perception of visual pitch of the field (PVP)-versus-pitch function. VPEL, PVP, and a cognitive factor separated into three essentially independent factors in a multiple-factor analysis, with the three cognitive tests clustering at the cognitive factor, and with no significant loading on either of the other two factors. From the above considerations and a multiple-factor analytic treatment including additional results from this and other laboratories, we conclude that the cognitive-processing style held to be involved in the performance on the EFT and the perception of vertical as measured by the RFT is not general for egocentric space perception; it does not involve the perception of elevation.

The rod-and-frame effect: the whole is less than the sum of its parts.

Since the discovery of the influence of the tilted frame on the visual perception of the orientation perceived as vertical (VPV), the frame has been treated as a unitary object-a Gestalt. We evaluated the effect of 1-line, 2-line, 3-line, and 4-line (square frame) stimuli of two different sizes, and asked whether the influence of the square frame on VPV is any greater than the additive combination of separate influences produced by the individual lines constituting the frame. We found that, for each size, the square frame is considerably less influential than the additive combination of the influences of the individual lines. The results conform to a mass action rule, in which the lengths and orientations of the individual line components are what matters and the organization of the lines into a square does not-no higher-level Gestalt property is involved in the induction effect on VPV.

Visually perceived vertical (VPV): induced changes in orientation by 1-line and 2-line roll-tilted and pitched visual fields.

We report a series of nine experiments which show that a single roll-tilted line in darkness induces changes of the orientation perceived as vertical (VPV) that are similar in magnitude and direction to those measured by Witkin and Asch (1948a) [Studies in space orientation. I. Perception of the upright with displaced visual fields. Journal of Experimental Psychology, 38, 762-782] with the classical square 4-sided frame, and we describe the configuration-independent mass-action rules by which the influences of the individual lines influences are combined. Clockwise (cw) and counterclockwise (ccw) orientations of a line produce cw and ccw displacements of the VPV setting, respectively, with effect magnitude increasing approximately linearly with line orientation (e.g., a 66.25 degrees - long line at 25 degrees horizontal eccentricity that varies in roll-tilt through +/-13.2 degrees around vertical generates a systematic variation in VPV over +/-7 degrees). The slope of the VPV-vs-roll-tilt function increases with line length along a negatively accelerated exponential function (length constant = 17.1 degrees). The influences of two bilaterally symmetric lines combine linearly and algebraically and the combined influence is linearly related to the sum of the VPVs for the 1-line components with a slope equal to 0.91 for short lines and 0.66 for long lines; thus, VPV for short lines manifests nearly complete additive summation, but for long lines, the 2-line VPV is nearer to the average of the VPV values for the two components measured separately. The effectiveness of the conjunction of two line segments within a visual scene does not depend on their separate orientations, only on their sum. Individual lines from pitched-only planes or from combinations of such planes generate identical influences to those generated from lines in frontoparallel planes with the same image orientations at the eye of the observer (their "retinal orientations"). Retinal orientation is the key to the induction of VPV change independently of the line's plane of origin.

Two wrongs make a right: linear increase of accuracy of visually-guided manual pointing, reaching, and height-matching with increase in hand-to-body distance.

Measurements were made of the accuracy of open-loop manual pointing and height-matching to a visual target whose elevation was perceptually mislocalized. Accuracy increased linearly with distance of the hand from the body, approaching complete accuracy at full extension; with the hand close to the body (within the midfrontal plane), the manual errors equaled the magnitude of the perceptual mislocalization. The visual inducing stimulus responsible for the perceptual errors was a single pitched-from-vertical line that was long (50 degrees), eccentrically-located (25 degrees horizontal), and viewed in otherwise total darkness. The line induced perceptual errors in the elevation of a small, circular visual target set to appear at eye level (VPEL), a setting that changed linearly with the change in the line's visual pitch as has been previously reported (pitch: -30 degrees topbackward to 30 degrees topforward); the elevation errors measured by VPEL settings varied systematically with pitch through an 18 degrees range. In a fourth experiment the visual inducing stimulus responsible for the perceptual errors was shown to induce separately-measured errors in the manual setting of the arm to feel horizontal that were also distance-dependent. The distance-dependence of the visually-induced changes in felt arm position accounts quantitatively for the distance-dependence of the manual errors in pointing/reaching and height matching to the visual target: The near equality of the changes in felt horizontal and changes in pointing/reaching with the finger at the end of the fully extended arm is responsible for the manual accuracy of the fully-extended point; with the finger in the midfrontal plane their large difference is responsible for the inaccuracies of the midfrontal-plane point. The results are inconsistent with the widely-held but controversial theory that visual spatial information employed for perception and action are dissociated and different with no illusory visual influence on action. A different two-system theory, the Proximal/Distal model, employing the same signals from vision and from the body-referenced mechanism with different weights for different hand-to-body distances, accounts for both the perceptual and the manual results in the present experiments.