Estimation of functional connectivity from electromagnetic signals and the amount of empirical data required

An increasing number of neuroimaging studies are concerned with the identification of interactions or statistical dependencies between brain areas. Dependencies between the activities of different brain regions can be quantified with functional connectivity measures such as the cross-correlation coefficient. An important factor limiting the accuracy of such measures is the amount of empirical data available. For event-related protocols, the amount of data also affects the temporal resolution of the analysis. We use analytical expressions to calculate the amount of empirical data needed to establish whether a certain level of dependency is significant when the time series are autocorrelated, as is the case for biological signals. These analytical results are then contrasted with estimates from simulations based on real data recorded with magnetoencephalography during a resting-state paradigm and during the presentation of visual stimuli. Results indicate that, for broadband signals, 50–100 s of data is required to detect a true underlying cross-correlations coefficient of 0.05. This corresponds to a resolution of a few hundred milliseconds for typical event-related recordings. The required time window increases for narrow band signals as frequency decreases. For instance, approximately 3 times as much data is necessary for signals in the alpha band. Important implications can be derived for the design and interpretation of experiments to characterize weak interactions, which are potentially important for brain processing

Teaching Theory of Mind

Research Findings: An understanding of another's mental state, beliefs, or desires is often referred to as theory of mind (ToM). Pretence has been shown to be a precursor to ToM (Leslie, 1987; Lillard, 1999, 2001), and thus ToM could potentially be developed through training in complex pretence (Dockett, 1998). In the current study, we test the hypothesis that ToM development can be enhanced through teaching pretence in an educational setting and consider the implications for pupils in the foundation stage. In particular we look at how training in ToM accelerates learning and development of ToM concepts. A group of 38 children (average age = 46 months) received intense pretence training or engaged in non-pretence-related activities for 15 min, 3 times a week for 4 weeks. Practice or Policy: Analysis of the difference between pre-and posttraining performance on measures of false belief, appearance-reality, and emotion recognition showed partial evidence for enhanced ToM development in response to pretence-based play in the treatment group. These findings provide evidence that ToM is multidimensional, with contributing components developing at different rates. Moreover, the results indicate that emotive and conceptual aspects of ToM can be taught through training sessions in pretence, signifying continual development of ToM throughout childhood. The implications of utilizing pretence within education settings are discussed. © 2013 Copyright Taylor and Francis Group, LLC

Magnocellular mediated visual-spatial attention and reading ability

This study explores the relationship between attentional processing mediated by visual magnocellular (MC) processing and reading ability. Reading ability in a group of primary school children was compared to performance on a visual cued coherent motion detection task. The results showed that a brief spatial cue was more effective in drawing attention either away or towards a visual target in the group of readers ranked in the upper 25% of the sample compared to lower ranked readers. Regression analysis showed a significant relationship between attentional processing and reading when the effects of age and intellectual ability were removed. Results suggested a stronger relationship between visual attentional and non-word reading compared to irregular word reading

A binocular site for contrast-modulated masking

Contrast-modulated (CM) gratings, composed of two luminance-modulated sinusoids of similar spatial frequency, mask the detection of test sinusoids at the difference frequency. However, the mechanism underlying masking by CM gratings remains poorly understood. In this paper, we aimed to determine whether the masking of 1 cycle deg−1 LM test gratings by a 1 cycle deg−1 beat (formed from a pair of carriers at 8 and 9 cycles deg−1) occurs in monocular channels or after the site of binocular combination, or both. Threshold elevations for the detection of a 1 cycle deg−1 test grating were obtained for a number of stimulus conditions, including: (1) dichoptic CM (both 8 and 9 cycles deg−1 mask components presented to one eye, with the 1 cycle deg−1 test grating to the other); (2) dichoptic variant (8 and 9 cycles deg−1 mask gratings presented to separate eyes, with the 1 cycle deg−1 test grating presented to one eye); (3) binocular CM (all mask and test gratings presented to both eyes). As a control, masking magnitude was also measured for LM mask gratings of similar frequency (1 cycle deg−1) and effective contrast (3%) to that of the beat. For both LM and CM masks, the dichoptic condition yielded threshold elevations that were similar or greater than the binocular condition. When 8 and 9 cycles deg−1 mask components were presented to separate eyes (the dichoptic variant condition), no beat pattern was visible and no elevations in detection threshold occurred. The results demonstrate that, like LM masking, detection of a target in the presence of a CM mask does not involve purely monocular mechanisms. Further, that the site of CM masking must occur beyond the stage at which monocular matching for stereopsis takes place. This is consistent with other studies which suggest that dichoptic masking is contingent on stereo matching, and thus occurs relatively late in the hierarchy of binocular visual processing

Dorsal stream associations with orthographic and phonological processing

Several studies have indicated a key role for dorsal stream processing in lexical decoding. To examine this relationship further, performance on orthographic and phonological reading tests was compared with both steady-state visual evoked potentials and a putative behavioral measure of dorsal stream processing, coherent motion detection. Frequency analysis of the visual evoked potential data showed power at the second harmonic to be largely confined to dorsal stream regions, and significantly correlated with motion detection thresholds. Regression analyses showed that orthographic processing was significantly associated with the second harmonic power. Although consistent with previous reports, there remains a question as to why the orthographic visual evoked potential power relationship did not extend to include the coherent motion detection measures. © 2006 Lippincott Williams & Wilkins