The roles of stimulus-response compatibility and mental rotation in mirror-image and left-right decisions.

Examined the relative roles of mental rotation and stimulus-response (SR) compatibility in mirror-image and left-right decisions. 15 Ss, aged 19–43 yrs, were shown rotated letters and asked to indicate whether the letters were normal or backward (mirror-image task). Ss were then asked whether a dot would be located to the left or right of each letter if the letter was upright (viewer-centered left-right task) or if the letter was both upright and normal (letter-centered left-right task). The functions relating reaction time (RT) to angular orientation were parallel across the 3 tasks, suggesting that SR compatibility played no role, and that the Ss mentally rotated the letters to the upright in each case. A marked increase in RT to backward letters in the letter-centered task suggested a 2nd rotation in depth to restore the letters to normal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reference frames in mental rotation.

Four experiments are reported that investigate whether images or reference frames are transformed during a mental rotation task. In all experiments a display of four identical letters (P1) was presented at either +90° or –90° from upright, and subjects had to decide whether the letters were normal or mirror-image reflections. A single letter (P2) was then presented 100 ms later in a variable orientation with the same task instructions. Reaction times to P2 were assessed to determine whether an image of P2 was rotated to upright or whether an internal reference frame was rotated into congruence with P2 from the orientation of P1. The results as a whole suggest that transformations of P2 can be initiated either relative to upright or relative to the orientation of P1. They further indicate that the probability of using each reference orientation can be changed by procedural variations. The findings are most parsimoniously interpreted as suggesting that mental rotation involves the transformation of reference frames rather than the transformation of template-like representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time to identify disoriented letters: Effects of practice and font.

Measured the time taken by 32 undergraduates to name letters shown in 4 orientations (0–280°) and presented in a familiar or an unfamiliar font. Naming time increased linearly as the letters were rotated further from the upright from 0 to 120°, but not from 120 to 180°. The orientation effect on the time to identify letters was more pronounced for the less familiar font than for the more familiar font. The orientation effect was larger in the 1st half of the experiment than in the 2nd half, suggesting a practice effect. Results suggest that smaller orientation effects on letter identification time compared with the time to identify other types of visual patterns may be due to the visual familiarity of typical alphanumeric characters. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-language tests of hemispheric strategies in reading nonwords.

Four experiments explored the effects of specific language characteristics on hemispheric functioning in reading nonwords using a lateralized trigram identification task. Experiment 1 tested whether this is due to the test language or to the native language of the participants. Results showed that native language had a stronger effect on hemispheric strategies than test language. Experiment 2 showed that latency to target letters in the CVCs revealed the same asymmetry as qualitative errors for Hebrew speakers but not for English speakers and that exposure duration of the stimuli affected misses differentially according to letter position. Experiment 3 used number trigrams to equate reading conventions in the 2 languages. Qualitative error scores still revealed opposing asymmetry patterns. Experiments 1-3 used vertical presentations. Exp 4 used horizontal presentation, which eliminated sequential processing in both hemispheres in Hebrew speakers, whereas English speakers still showed sequential processing in both hemispheres. Comparison of the 2 presentations suggests that stimulus arrangement affected qualitative errors in the left visual field but not the RVF for English speakers and in both visual fields for Hebrew speakers.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Image generation and processing of generated images in the cerebral hemispheres.

Recent computational models describing the contribution of the cerebral hemispheres to visual imagery have suggested an exclusive capacity of the left hemisphere to generate multipart images. A brief review of relevant findings indicates that the evidence presented in support of this suggestion is not entirely compelling; this prompted a reexamination of this issue in a lateral tachistoscopic study on normal adults. Sixteen subjects participated in two experiments in which they had to decide whether or not a lowercase letter contained a segment extending above or below the main body of the letter. This decision was made directly on lowercase letters in one experiment (perceptual task) and on their generated images in the other experiment (imagery task). The quality of the letters (clear or blurred) and the retinal eccentricity of stimulus presentation (small or large) were orthogonally manipulated. The perceptual task yielded no main effect of visual field but a significant interaction of visual field and letter quality. By contrast, the imagery task resulted in a left visual-field superiority but no interaction involving the visual fields—a departure from predictions based on current models of visual imagery. In addition, the pattern of results in the imagery task corresponded to that obtained with blurred letters in the perceptual task, suggesting limitations in spatial resolution of visual images. Implications of these results for models of cerebral lateralization and visual imagery are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of sex hormone therapy on interhemispheric crosstalk in postmenopausal women.

Evidence exists that fluctuating levels of sex hormones affect interhemispheric interaction in women during the menstrual cycle. The present study investigated whether interhemispheric interaction is susceptible to direct hormonal manipulations via hormone therapy (HT). Sixty-eight postmenopausal women who received HT either with estrogen alone (n = 15), an estrogen-gestagen combination (n = 22) or without HT (n = 31) were investigated. Participants were asked to match letters according to their physical or name identity. Matches were presented either within or across visual half-fields. Additionally, a simple reaction time task, assumed to estimate interhemispheric transfer time (IHTT), was used. Overall, postmenopausal women showed an across-field advantage in the more demanding name-identity task but not in the less demanding physical-identity task. However, across both tasks, the groups differed in responses to within- and across-field trials: the control group performed better on across- than within-field trials, whereas both HT groups showed faster responses on within- than across-field trials. IHTT did not differ between groups. The findings suggest that postmenopausal estrogen-therapy affects the relative efficiency of interhemispheric integration by modulating within-hemisphere functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of orientation on the identification of rotated objects depend on the level of identity

Matching names and rotated line drawings of objects showed effects of object orientation that depended on name level. Large effects, in the same range as object naming, were found for rotations between 0 degrees and 120 degrees from upright with subordinate names (e.g., collie), whereas nonsignificant effects were found with superordinate (e.g., animal) and basic names (e.g., dog). These results support image normalization, after contact with orientation-invariant representations, that provide basic-level identity. They consequently fail to support theories of object recognition in which rotated object images are normalized to the upright position before contact with long-term object representations.     

Transposed-letter effects in reading: Evidence from eye movements and parafoveal preview.

Three eye movement experiments were conducted to examine the role of letter identity and letter position during reading. Before fixating on a target word within each sentence, readers were provided with a parafoveal preview that differed in the amount of useful letter identity and letter position information it provided. In Experiments 1 and 2, previews fell into 1 of 5 conditions: (a) identical to the target word, (b) a transposition of 2 internal letters, (c) a substitution of 2 internal letters, (d) a transposition of the 2 final letters, or (e) a substitution of the 2 final letters. In Experiment 3, the authors used a further set of conditions to explore the importance of external letter positions. The findings extend previous work and demonstrate that transposed-letter effects exist in silent reading. These experiments also indicate that letter identity information can be extracted from the parafovea outside of absolute letter position from the first 5 letters of the word to the right of fixation. Finally, the results support the notion that exterior letters play important roles in visual word recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Division of labor between the hemispheres for complex but not simple tasks: An implemented connectionist model.

When stimuli have to be matched in a complex task (such as whether 2 letters have the same name), then performance is better when stimuli are presented across the hemispheres of the brain, whereas for simpler tasks (such as whether 2 letters have the same shape), better performance is achieved when stimuli are presented unilaterally. The authors show that this bilateral distribution advantage effect emerged spontaneously in a neural network model learning to solve simple and complex tasks with separate input layers and separate, but interconnected, resources in a hidden layer. The authors show that relating computational models to behavioral and imaging data proves fruitful for understanding hemispheric processing and generating testable hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The characteristics of monoclonal antibodies and their antigens associated with human sperm acrosome reaction. I. The induction of acrosome reaction and monoclonal antibody production

A low blood glucose level is associated with impairment of higher cerebral function and an increase in cerebral blood flow. This study examined whether there are differences in the physiological responses to hypoglycaemia between the cerebral hemispheres. Eight healthy men participated in two hyperinsulinaemic glucose clamp studies: after 60 min at 4.5 mmol/l, blood glucose was either lowered to 2.0 mmol/l and "clamped" there for 60 min (hypoglycaemia) or continuously maintained at 4.5 mmol/l (euglycaemia). Cardiac output, middle cerebral artery velocity (transcranial Doppler) and cerebral blood flow (133-xenon inhalation) were measured during the studies. Neuropsychological tests were used to determine whether hypoglycaemia caused differential impairment of hemispheric cognitive function. Hypoglycaemia was associated with symmetrical impairment of cognitive function in both cerebral hemispheres and a rise in cardiac output (from 5.5 [0.2] to 8.7 [0.2] l.min-1, p < 0.0001, mean [standard error]), middle cerebral artery velocity (from 55 [2.6] to 64 [2.8] cm.s-1, p < 0.002), and global cerebral blood flow (from 56 [2.6] to 69 [2.9] ml.100 g-1.min-1, p < 0.005 compared to pre-insulin values). There were no differences in the blood flow response during hypoglycaemia between hemispheres and the increase in blood flow did not correlate with either the change in cardiac output or rise in plasma catecholamine levels. After 120 min of hyperinsulinaemic, euglycaemia, global cerebral blood flow rose significantly above baseline (from 58 [2.4] to 63 [2.2] ml.100 g-1.min-1, p < 0.05). In conclusion, using the techniques described, the physiological and cognitive responses of each cerebral hemisphere to hypoglycaemia were symmetrical.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of sensory limitations on hemispheric processing.

How the brain processes information is partly determined by the characteristics of the input. To examine whether the 2 cerebral hemispheres are equally affected by manipulations of quality of incoming information, 3 experiments using M. I. Posner and R. F. Mitchell's (1967) paradigm (matching pairs of letters of same or different case or name) were conducted under 8 viewing conditions, consisting of manipulations of exposure duration, retinal eccentricity, and stimulus size. The same procedure but different designs were used in the 3 studies: a between-S design in Exp I; a within-S design with viewing conditions blocked in Exp II; and a within-S design with viewing conditions mixed in Exp III. In all experiments, which used 88 18–30 yr old right-handed Ss, exposure duration and retinal eccentricity each interacted with visual fields, whereas the interaction of letter size and visual field was significant only in Exp II. Results are interpreted with respect to the properties of the visual system and its capacity to extract information in terms of the spatial-frequency spectral components of a stimulus. Methodological implications are discussed. (French abstract) (2? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus arrangement on hemispheric differences and interhemispheric interaction for processing letter trigrams.

Observers identified consonant-vowel-consonant (CVC) nonsense syllables with the letters arranged horizontally. In each of 2 experiments, there were fewer errors when stimuli were presented to the right visual field (RVF) and left hemisphere (LH) than when stimuli were presented to the left visual field (LVF) and right hemisphere (RH), and the extent to which the number of last-letter errors exceeded the number of first-letter errors was greater on LVF/RH than on RVF/LH trials. When the same stimulus was presented simultaneously to both visual fields (Experiment 2), the qualitative error pattern was very similar to the pattern obtained on LVF/RH trials. These effects replicate results obtained in earlier CVC identification experiments with letters arranged vertically. However. when a single stimulus was presented in the center of the visual field (Experiment 1), so that the first letter of the CVC projected to the LVF/RH and the last letter projected to the RVF/LH, the error pattern was a mixture of the LVF/RH and RVF/LH patterns, as if each hemisphere took the lead for processing the letter it received directly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the regulation of cognitive control: Action orientation moderates the impact of high demands in Stroop interference tasks.

Previous research has established that people vary in action orientation, a tendency toward decisiveness and initiative, versus state orientation, a tendency toward indecisiveness and hesitation (J. Kuhl & J. Beckmann, 1994b). In the present 3 studies, the authors examined whether action orientation versus state orientation regulates cognitive control under demanding conditions. Under high demands, action-oriented participants displayed better cognitive control than did state-oriented participants in a Stroop color naming task (Studies 1-3). No similar effects were found under low demands (Studies 2-3). Functional differences between action- and state-oriented participants emerged especially when the task included a high proportion of congruent Stroop trials (Study 3). These findings suggest that action-oriented individuals are better protected against goal neglect than are state-oriented individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disentangling gravitational, environmental, and egocentric reference frames in spatial neglect

Previous studies in neglect patients using rotation of the body around the roll-axis revealed neglect of visual stimuli not only in the egocentric, body-centered left but also in the environmental left. The latter has been taken as evidence for a gravity-based environment-centered component of neglect occurring independently of the subject's actual body orientation. However, by using visual stimuli in a normally lightened room, the studies confounded the gravitational upright with the visible upright of the surround. Thus, it is possible that the visible upright of the environment may have served the role of the gravitational upright relative to which neglect occurred. The present experiment evaluated the influence of gravity on contralateral neglect when no visual information was presented. In complete darkness, neglect patients' exploratory eye movements were recorded in five experimental conditions: body in normal upright position, body titled 30 degrees to the left and 30 degrees to the right, and body pitched 30 degrees backward and 30 degrees forward. In the upright orientation, the patients with neglect showed a bias of ocular exploration to the ipsilesional right side. In egocentric body coordinates, we found no significant differences between the orientation of the biased search field in the different experimental conditions showing that the search field shifted with the orientation of the body. No significant decrease or enhancement of neglect was observed when body orientation was varied in the different conditions. In conclusion, the present results revealed that the modulation of gravitational forces has no significant influence on the exploratory bias of these patients. When visual information was excluded and only graviceptive information was available, the patients' failure to explore the contralesional part of space appeared purely body-centered. The results argue against a disturbed representation of space in neglect that encodes locations in a gravity-based reference system.     

Effects of bilateral stimulation and stimulus redundancy on interhemispheric interaction.

Recent visual laterality studies have included trials in which critical stimulus information is presented simultaneously in both visual half-fields and, thereby, simultaneously to both cerebral hemispheres. To investigate interhemispheric interaction, researchers compare performance on bilateral redundant trials with performance on unilateral trials in which a single copy of the target is presented to one hemisphere or the other. The authors used the identification of nonword letter trigrams to examine the relationship between unilateral and bilateral performance when the 2 types of trials were equated for the number of locations stimulated (Experiment 1) and the number of redundant copies of the target (Experiment 2). Results suggest that when the number of stimulated locations is held constant, each of 2 copies of a target stimulus can be processed with the same efficiency and the same strategy as it would have been had it been the only copy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orientation congruency effects on the identification of disoriented shapes.

Effects of orientation on identification can be attenuated when other patterns at the same (or a similar) orientation are identified in close temporal contiguity. In Experiments 1 and 2, letters were presented simultaneously in brief masked displays. Identification accuracy was much higher when the letters had consistent orientations than when the letters had different orientations within a display. In Experiment 3, two letters were presented sequentially. Identification accuracy was higher with congruent than with incongruent orientations. The results are unexpected if one assumes that the patterns themselves are rotated until upright prior to their identification, unless pattern rotation processes can be primed, and that priming requires orientation congruence between the priming and primed stimulus. The results are expected if the orientation of a frame of reference can be adjusted to the orientation of the patterns during the identification process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right visual field superiority for letter recognition with partial report.

Experiments using partial report techniques have typically failed to find left-right visual field differences in the recognition of tachistoscopically presented letter rows. Such data represent a difficulty for theories that emphasize the relevance of cerebral hemispheric asymmetry. It is contended that the end items of a display are critical, and that a truly symmetric display should have both a left and a right end item in each visual field. In the present experiments with 36 righthanded university students, partial report procedures were employed, but a gap was placed between the left and right halves of the display. In the 1st experiment, a single-letter spatial probe procedure was used, and a clear right visual field superiority was found. In the 2nd experiment, a hemifield report procedure was used; the presence of a gap in the display enhanced the right visual field superiority, especially for shorter strings of letters. Results indicate that right visual field superiority can be obtained with partial report procedures under appropriate conditions. (French summary) (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orientation congruency effects in visual search.

Studied 24 undergraduates who searched for the letter E in a background of letter Ls and Fs in displays that had 1, 2, 4, 8, or 12 letters. The letters could be shown at 1 of 6 orientations. The displays were either congruent for orientation or incongruent. Search time increased linearly with the number of letters in the display, and more so for E-absent trials than for E-present trials. Letter orientation, in general, increased search time and produced an M-shaped function. Results demonstrate systematic orientation effects on the time to search for a simple pattern embedded in simple backgrounds. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Top-bottom and front-behind decisions on rotated objects.

Examined 2 tasks requiring the perception of the spatial relationship between an object and a dot. 24 undergraduates decided whether a dot was nearer the top or bottom of rotated drawings of objects in a top-bottom task, and whether a dot was at the front of or behind rotated objects in a front-behind task. These 2 tasks were performed with the head upright and with the head tilted clockwise and counterclockwise in separate blocks of trials in order to dissociate retinal from environmental perceptual frames of reference. Response times increased approximately linearly with increasing departure from the orientation of the perceptual reference frame in both tasks; the magnitude of the effect was similar across tasks. In the head-tilted conditions, the perceptual frame of reference was located midway between the environmental and retinal upright for both tasks. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)