Presentation software neurobehavioral systems inc,security software for apple imac,seo google mobile - For Begninners

07.12.2015
We will be provided with an authorization token (please note: passwords are not shared with us) and will sync your accounts for you. Previous studies have reported inconsistent results when comparing spatial imagery performance in the blind and the sighted, with some, but not all, studies demonstrating deficits in the blind. Experimental evidence indeed suggests that individual differences in preferences for object or spatial imagery could modulate performance on spatial tasks.
Although the object-spatial imagery continuum was originally described in relation to visual imagery, similar differences arise in haptically derived images and multisensory representations (Lacey et al., 2010, 2011), raising the possibility that individual differences may also modulate performance in the visually impaired.
Here, we examined how performance on a spatial imagery task, similar to those used in earlier studies, is affected by visual status or individual cognitive style, and how spatial imagery performance relates to a participant's sense of direction, by comparing a group of late-blind participants to an age- and gender-matched control group. Participants were scored on the SBSoDS, which uses a set of questions to assess real-world spatial navigation abilities (Hegarty et al., 2002). The spatial imagery task required imagining a previously memorized 4 × 4 matrix with one letter in each position (Figure 1). Since our blind participants varied quite widely in the age at which they lost vision, we examined the correlation between the age at which form vision was completely lost and accuracy on the spatial imagery task for the blind group.
In the present study, we showed that the visual status of participants has an impact on performance of the spatial imagery task tested here. It is worth noting that in the present study, additional processes were required for the spatial imagery task, including the generation of mental images on the basis of the auditory letter cues.
The present study also sought to assess whether individual cognitive style affects performance on a spatial imagery task. The verbalizer scores, whether self-reported (by all participants) or collected with the OSIVQ (in the sighted), were robustly negatively correlated with accuracy on the spatial imagery task. Furthermore, we found a significant positive correlation between the SBSoDS scores and the level of spatial imagery performance.
After intensive practice, unfamiliar letter strings become familiar words and reading speed increases strikingly from a slow processing to a fast and with more global recognition of words. During reading, eyes browse through sentence elements at a very fast pace of around five fixations per second on average (Kliegl et al., 2006). In addition, GBR have recently been shown to correlate tightly with the average firing rate of neural populations (Ray and Maunsell, 2011).
We measured the amplitude and duration of GBR elicited by familiar (words) and unfamiliar (pseudo-words) letter strings, as a function of syllabic length (short vs.
Five epileptic patients (P1–P5) suffered from drug-resistant partial epilepsy and were candidates for surgery in order to remove the epileptic region.
The implantation sites were selected entirely for clinical purpose with no reference to the present experimental protocol. Stimuli were 208 French words and 208 pronounceable pseudo-words (for each lexical type, 104 short, mono-syllabic, and 104 long, three-syllabic).
Before iEEG recording in patients, a behavioral experiment was conducted in healthy subjects in order to pre-test the stimuli. Intra-cerebral EEG recordings were performed while patients silently read words and pseudo-words.
Intra-cerebral EEG signals were analyzed with the software package for electrophysiological analysis (ELAN-Pack) developed in the INSERM U1028 laboratory (Aguera et al., 2011). We used two methods in order to optimally assess spectral responses and their statistical evaluation. Our main results show that reading familiar (words) and unfamiliar (pseudo-words) items of one-syllable and three-syllables length elicited GBR in the recorded nodes regions (left inferior frontal, SMG, and inferior temporo-occipital cortex).
The mRT, SD, and mean error rates (% ER) for reading words and pseudo-words are shown in Table 1.
We compared directly GBR elicited by words and pseudo-words in these three regions of interest. Our parent company, The Lovelace Respiratory Research Institute (LRRI), has the mission to serve humanity through research on the prevention, treatment, and cure of respiratory disease. This means that you will not need to remember your user name and password in the future and you will be able to login with the account you choose to sync, with the click of a button. This page doesn't support Internet Explorer 6, 7 and 8.Please upgrade your browser or activate Google Chrome Frame to improve your experience.
For example, Vecchi (1998) found that the congenitally blind were less accurate than the sighted when tested on a task that involved learning target squares and pathways on haptic matrices. The blind participants were recruited through advertisements placed with the Center for the Visually Impaired in Atlanta, Georgia, and the Georgia chapter of the National Federation of the Blind.
Sighted participants completed the OSIVQ (Blazhenkova and Kozhevnikov, 2009), so that their preferences for object imagery, spatial imagery and verbalizing could be assessed. Significant correlations across all participants between accuracy on the spatial imagery task and (A) age, (B) self-reported verbalizer scores, and (C) SBSoDS scores. The blind were less accurate than the sighted, with no effect of the duration of blindness.
The data showed a similar distribution of preferences for object and spatial imagery across the different groups, indicating that the distribution of imagery preferences is not affected by visual status. The possibility that this outcome (in the case of the self-reported scores) could simply reflect visual status was ruled out by partial correlation analysis in which this variable was controlled. This outcome is of interest for multiple reasons: it provides evidence that the spatial imagery task tested here is ecologically valid and also reinforces the idea that a better sense of direction is related to a more proficient representation of spatial information.
While this effect has been well documented at the behavioral level, its neural underpinnings are still unclear.
There were four female patients and one male patient; all were right-handed native French speakers and aged from 33 to 55 years (mean of age 44 years). However, the patients who entered this protocol were selected because their implantation sampled regions classically associated with language and reading (peri-sylvian regions).
They were selected from BRULEX lexical database for French (Content et al., 1990) and were low to high frequency. Each of these lists was presented in an individual run and the experiment itself consisted of three runs. For the alpha-band (8–12 Hz) in particular signals were band-pass filtered in that frequency band. Illustrates time × frequency representation of spectral responses in the regions of interest induced by short and long words and pseudo-words in patients 1, 2, and 5. As shown in Figure 3 and Figure A2 in Appendix, the time-resolved responses were stronger in amplitude for pseudo-words compared to words. Participants with blindness resulting in the loss of form vision at or after age 6, and age- and gender-matched sighted participants, performed a spatial imagery task requiring memorization of a 4 × 4 lettered matrix and subsequent mental construction of shapes within the matrix from four-letter auditory cues. On a similar task, the congenitally blind were less accurate than the sighted when using a spatial imagery strategy but were comparable to the sighted when using a verbal strategy (Cornoldi et al., 2009). Clinical and demographic details are provided in Table 1, which shows that the age at which the blind participants completely lost form vision ranged from 6 to 50. Thus, participants had to compute global shape by processing the spatial relationships between component parts.
It is worth noting, however, that a marginally significant difference was observed for the self-reported verbalizing scores, with the blind tending to have higher scores than the sighted.
The question is how the brain modulates the activity of the reading network according to the novelty of the items. By definition, such global processing would allow for fast semantic and phonological analysis independently of word length. We found that all items elicited clear neural responses in all three regions of interest (Broca, SMG, and ITOC), but the duration of the neural responses increased with length only for pseudo-words.


MRI revealed a left hippocampal sclerosis in four patients and no lesion in the remaining patient.
Eleven to 14 semi-rigid electrodes were implanted per patient, in cortical areas which varied depending on the suspected origin of seizures. They were placed in front of a computer (Dell PC) monitor and visualized the stimuli described above delivered by means of E-prime software. This reference has the same impedance as the other contact sites and was located in a region with no or little source of electrical field. The Hilbert transform was used to estimate the global energy in the 50- to 150-Hz range at each sample during the entire recording session in a computationally efficient way.
Next, for each band-pass filtered signal we computed the envelope using a standard Hilbert transform. Before presenting in detail the iEEG results, we show first the behavioral results obtained in pre-test in healthy subjects. As shown in Figure 1B, GBR across patients were elicited initially in inferior temporal cortices, between 100 and 200 ms after stimulus onset. Importantly, stronger responses for pseudo-words compared to words, were independent of the length of items. They also completed the Santa Barbara Sense of Direction Scale (SBSoDS) and a self-evaluation of cognitive style.
By contrast, blind and sighted participants showed equivalent performance on spatial judgments from different imagined perspectives on visually and haptically learned maps, and both groups exhibited evidence for spatial updating (Giudice et al., 2011). Despite the existence of previous research investigating the behavioral effects of reliance on different cognitive styles, the effect of individual preferences for object imagery, spatial imagery and verbalizing has not been investigated in the blind, to the best of our knowledge. Performance on this task is also expected to be modulated by imagery preference, with object imagers performing worse than spatial imagers, given the higher proficiency of the latter group at processing the spatial relationships between object parts (Kozhevnikov et al., 2005).
As is common in studies of the blind, many of them had some visual loss at birth that subsequently progressed for various reasons. Participants were asked to read and rate each item of the questionnaire on a 5-point scale, with 1 = totally disagree and 5 = totally agree, and ratings 2–4 indicating intermediate degrees of agreement or disagreement. However, the verbalizer score was higher in blind compared to sighted participants, with the difference trending toward significance [0.51 vs. The present finding of a significant negative correlation between age and spatial imagery performance thus seems consistent with previous evidence, and suggests that, besides visual status, age could be an additional factor affecting the performance in a small-scale spatial imagery task, such as the one used here.
Several models have proposed that familiar and unfamiliar words are not processed by separate networks but rather by common regions operating differently according to familiarity. After intensive practice, as unfamiliar letter strings (novel, unfamiliar words) become familiar, reading speed would increase strikingly from slow sequential to fast and more global reading and recognition. These findings further support previous findings that gamma-band modulations co-localize with BOLD variations and also indicate that fMRI may be used as a constraint to improve source reconstruction of gamma-band EEG responses. Our results provide an explanation at the neural level for the increase in reading speed with word familiarity. The stimuli were presented one at a time on the center of the screen during 500 ms and separated by a 150 ms fixation cross. Additionally, the reference was not contaminated by eye-movement artifacts or electromyographic activity from subtle muscle contractions. We further used the Hilbert transform to obtain the instantaneous amplitude of this frequency band-limited spectral response, which is a less complex signal than the time–frequency (TF) representation, and thus presents higher power for statistical comparisons. This gamma-band energy time-series could be conveniently processed to measure the mean response to each stimulus category with its SE. Moreover and for all sites, the responses to long pseudo-words (PW3) appear to last longer than responses to short (PW1) pseudo-words. Consequently, the lexical effect was obtained for the following comparisons: long words vs. The sighted participants also completed the Object-Spatial Imagery and Verbal Questionnaire (OSIVQ). Vanlierde and Wanet-Defalque (2004) required early-, late-blind and sighted participants to imagine shapes in a matrix, following line-by-line descriptions as to whether each square was black or white, and to make symmetry judgments. The Object-Spatial Imagery and Verbal Questionnaire (OSIVQ) assesses individual preferences for particular cognitive styles: verbalizing, object imagery and spatial imagery (Blazhenkova and Kozhevnikov, 2009). Moreover, preferential reliance on verbal cognitive style is predicted to impair spatial imagery performance, consistent with previous evidence on the effect of cognitive style on map learning (Pazzaglia and Moè, 2013). The total score on each of the three scales corresponds to the mean of the item scores for that scale.
However, we were able to rule out the possibility that age might have obscured the effects of other individual differences, such as visual status or cognitive style, on spatial imagery performance: blind and sighted participants were not only age-matched, but the correlations computed between age and cognitive style scores for both groups turned out to be insignificant. This hypothesis has proved difficult to test at the neural level because the effects of familiarity and length on reading occur (a) on a millisecond scale, shorter than the resolution of fMRI and (b) in regions which cannot be isolated with non-invasive EEG or MEG.
However, the time resolution of fMRI is not sufficient to demonstrate unambiguously an effect of syllabic length on the duration of neural responses.
The authors used a semantic task (living–non-living categorization) which is different from a simple reading task mainly based on word recognition, used in the present study. A total number of 344 sites were recorded from the five patients, 310 in the left hemisphere, and 34 in the right. Participants were instructed to read aloud, as accurately and as quickly as possible, each item. Stimuli were delivered by means of Presentation software (Presentation, Neurobehavioral systems) on a Dell PC with a 17″ color monitor. After the stimulus onset, the inferior temporo-occipital cortex (ITOC) elicits early GBR which propagates after 300 ms to inferior frontal gyrus (Broca’s area) and after 400 ms to supramarginal gyrus (SMG).
However, all signals were re-referenced to their nearest neighbor on the same electrode, 3.5 mm away before analysis (bipolar montage). Visual status affected performance on the spatial imagery task: the blind performed significantly worse than the sighted, independently of the age at which form vision was completely lost. Despite the demanding nature of the encoding process, the three groups performed similarly but employed different strategies, the late-blind and sighted using mental imagery while the early-blind used a coordinate system that was not visually based.
Further, we expected that the SBSoDS score would correlate positively with spatial imagery performance, indicating ecological validity for our spatial imagery task (see Wolbers and Hegarty, 2010, for a review).
The sighted controls were recruited through advertisements posted on the Emory campus and intranet. For each participant, the spatial imagery score was subtracted from the object imagery score such that a negative difference score (O-S) represents a preference for spatial imagery whereas a positive O-S represents a preference for object imagery, as described earlier (Lacey et al., 2011). These findings were interpreted to mean that basic spatial processes are intact in the blind, but limitations emerge when the simultaneous maintenance of multiple images is required. The sighted group did show a trend toward a correlation in the expected direction, with better performance tending to correlate with a higher preference for spatial (vs. Even more interestingly, the authors found that this strategy was preferred by blind people with more limited mobility skills. We overcame these limitations by using invasive intra-cerebral EEG recording in epileptic patients. The neural substrate of this transition from sequential to global processing is still unclear. Since the only non-invasive brain recording techniques with high-temporal resolution (EEG and MEG) lack the spatial precision to isolate responses from individual components of the reading network, we turned to invasive EEG recordings.
The short pseudo-words were created by recombining the onset, nucleus, and coda of short words; long pseudo-words were generated by recombining the syllables of long words.
They were written in white lowercase letters (bold Courier new 18) on a light gray background.


By construction, the mean value of that time-series across the entire recording session is equal to 100. Visual status did not affect the distribution of preferences based on self-reported cognitive style.
Since the object-spatial dimension is a continuum rather than being simply dichotomous (Kozhevnikov et al., 2010), the difference score represents the relative weight of one type of imagery over another. No time limit was set for this and no instructions were provided regarding the method of memorization, to allow for spontaneous use of individually preferred strategies. This may account for the difference in the present study between blind and sighted participants, since the capability to maintain and update spatial information was crucial in order to efficiently perform the task. By contrast, blind people who were more independent tended to prefer a mental imagery strategy, just as sighted people did, and performed at the same level as the sighted. We collaborated with five epileptic patients undergoing invasive pre-surgical intra-cerebral EEG (iEEG) to measure neural activity with millimeter and millisecond resolution in the reading network. Consequently, although the processes and regions revealed by these two tasks are partially overlapped, they are also distinct. Therefore, various medial and lateral cortical areas were evaluated, including sulcal cortex. A white screen displayed for 1000 ms before the next stimulus allowed the experimenter to check naming accuracy by pressing a keyboard button. Each item was presented for 1000 ms with 1000 ms inter-stimulus interval (see Figure 1A for experimental design).
To show that the two methods obtain similar results we show an example of gamma-band activity with each one of them (Figure A3 in Appendix). To test for significant increases or decreases compared to baseline activity, we used paired-sample Wilcoxon signed rank test, followed by false discovery rate (FDR) correction across all time samples.
Specifically, Lexicality interacted with Length; significant effect of Length has been obtained for pseudo-word but not for word reading.
Across all participants, self-reported verbalizer scores were significantly negatively correlated with accuracy on the spatial imagery task. For the blind group, either Braille versions of the consent documents were provided or the experimenter read the forms aloud to the participant prior to signature.
In the absence of a standardized tool to assess preferential imagery strategies in blind people, we followed the three-dimensional model proposed by Blazhenkova and Kozhevnikov (2009) in order to build a cognitive style self-evaluation report. To test for accurate memorization, participants were asked to identify the four-letter sequences that formed all the horizontal rows, vertical columns, 2 × 2 squares, and diagonal lines.
This correlation was clearly significant when considering the analysis conducted on the OSIVQ scores, indicating further that our spatial imagery task is a valid index of overall spatial ability. The implanted regions across patients are represented in green; the non-sampled regions are represented in blue.
This allowed for quantitative definition of the onset time and duration of activation of specific recording sites. There was a positive correlation between the SBSoDS score and accuracy on the spatial imagery task, across all participants, indicating that a better sense of direction is related to a more proficient spatial representation and that the imagery task indexes ecologically relevant spatial abilities.
All procedures conformed to the Declaration of Helsinki and were approved by the Emory University Institutional Review Board. All participants read or were read a script (see Supplementary Materials), and were then asked to classify themselves as an object imager, a spatial imager or a verbalizer by assigning a proportion score (from 0 to 1 for each dimension, so that the total equaled 1) to each cognitive style. They then had to describe the shapes represented by the four-letter sequences, read aloud by the experimenter, for all the horizontal rows, vertical columns, and the 2 × 2 squares in the four corners of the grid (note that none of these shapes appeared in the main task). In order to check whether this correlation could have been driven by the (nearly significant) discrepancy in the verbalizer scores reported by the two groups, a partial correlation, controlling for visual status, was performed. There was no such correlation in the blind, suggesting that although individual preferences exist, vision loss may override their influence on spatial imagery performance. While all items elicited strong neural responses in the three regions, we found that the duration of the neural response increases with length only for pseudo-words, in direct relation to orthographic-to-phonological conversion.
The electrode contacts were identified on each individual stereotactic scheme and then anatomically localized, using the proportional atlas of Talairach and Tournoux (1988). To avoid outliers, reaction times (RTs) more than two SD above or below the mean were discarded. Figure 1C illustrates the global cortical area covered by the electrode implantations across patients. To compare the activity from paired conditions we used the non-parametrical Kruskal–Wallis test followed by FDR correction across all time samples. Moreover, the older the participants were, the worse their performance was, indicating a detrimental effect of age on spatial imagery performance. However, this inference should be regarded as tentative in the absence of an OSIVQ-like questionnaire that is suitable for blind people. Our results validate at the neural level the hypothesis that all words are processed by a common network operating more or less efficiently depending on words’ novelty.
The reading network explored in this study is supposed to be narrower and more specific to the process of word recognition. In addition, the computer-assisted matching of post-implantation CT-scan with 3-D MRI pre-implantation, provided direct visualization of the electrode contacts with respect to the brain anatomy of each patient (Actavis, Lyon, France).
Furthermore, words and pseudo-words were matched on onsets in order to control for acoustic factors that could bias the triggering of the vocal key (Kessler et al., 2002). The mean reaction times (mRT) and the error rates by-participants (F1) and by-items (F2) for correct responses only, were analyzed by using 2 × 2 ANOVAs. Thus, spatial skills represent an important target for rehabilitative approaches to visual impairment, and individual differences, which can modulate performance, should be taken into account in such approaches. When all these questions could be answered correctly, participants proceeded to the main task.
The patients performed the task a few days after the implantation of the electrodes and all of them have previously given their informed consent to participate in the experiment. Words and pseudo-words had no neighbors in order to prevent from a potential effect of this variable on reading latencies (Andrews, 1997). Lexicality (word, pseudo-word) and Length (short; long) were within-participant factors in the analysis by-participants (F1) and they were no repeated measure factors in the by-items analysis (F2). This training procedure helped ensure similar encoding of the matrix in both sighted and blind participants despite the different modalities of presentation.
Finally, participants were given a practice run of the actual task, as described below, to accustom them to generating images cued by four-letter strings at the speed of the actual experiment and without feedback about errors. Three lists of stimuli were presented – two composed of 144 items (72 words) each and a third one composed of 128 items (64 words). For the actual spatial imagery task, participants completed 4 runs consisting of 6 blocks, each containing 3 trials (72 trials in all). Thus, within each block, the second four-letter string was compared with the first, the third with the second and the fourth with the third.
Since changing the letters necessarily changed the location of the shape in the matrix (Figure 1A), participants were instructed that they should make their decisions based on the shapes they constructed, ignoring their locations in the matrix. The experiment was conducted using Presentation software (Neurobehavioral Systems Inc., Albany, CA).



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