Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Aerospace medicine and biology, an annotated bibliography. volume xi- 1962-1963 literature

Aerospace medicine and biology - annotated bibliography for 1962 and 196

Lateralised repetition priming for face recognition: priming occurs in the right hemisphere only

No description supplie

Development of a System for the Training Assessment and Mental Workload Evaluation

Several studies have demonstrated that the main cause of accidents are due to Human Factor (HF) failures. Humans are the least and last controllable factor in the activity workflows, and the availability of tools able to provide objective information about the user’s cognitive state should be very helpful in maintain proper levels of safety. To overcome these issues, the objectives of the PhD covered three topics. The first phase was focused on the study of machine-learning techniques to evaluate the user’s mental workload during the execution of a task. In particular, the methodology was developed to address two important limitations: i) over-time reliability (no recalibration of the algorithm); ii) automatic brain features selection to avoid both the underfitting and overfitting problems. The second phase was dedicated to the study of the training assessment. In fact, the standard training evaluation methods do not provide any objective information about the amount of brain activation\resources required by the user, neither during the execution of the task, nor across the training sessions. Therefore, the aim of this phase was to define a neurophysiological methodology able to address such limitation. The third phase of the PhD consisted in overcoming the lack of neurophysiological studies regarding the evaluation of the cognitive control behaviour under which the user performs a task. The model introduced by Rasmussen was selected to seek neurometrics to characterize the skill, rule and knowledge behaviours by means of the user’s brain activity. The experiments were initially ran in controlled environments, whilst the final tests were carried out in realistic environments. The results demonstrated the validity of the developed algorithm and methodologies (2 patents pending) in solving the issues quoted initially. In addition, such results brought to the submission of a H2020-SMEINST project, for the realization of a device based on such results

Paradigm free mapping: detection and characterization of single trial fMRI BOLD responses without prior stimulus information

The increased contrast to noise ratio available at Ultrahigh (7T) Magnetic Resonance Imaging (MRI) allows mapping in space and time the brain's response to single trial events with functional MRI (fMRI) based on the Blood Oxygenation Level Dependent (BOLD) contrast. This thesis primarily concerns with the development of techniques to detect and characterize single trial event-related BOLD responses without prior paradigm information, Paradigm Free Mapping, and assess variations in BOLD sensitivity across brain regions at high field fMRI. Based on a linear haemodynamic response model, Paradigm Free Mapping (PFM) techniques rely on the deconvolution of the neuronal-related signal driving the BOLD effect using regularized least squares estimators. The first approach, named PFM, builds on the ridge regression estimator and spatio-temporal t-statistics to detect statistically significant changes in the deconvolved fMRI signal. The second method, Sparse PFM, benefits from subset selection features of the LASSO and Dantzig Selector estimators that automatically detect the single trial BOLD responses by promoting a sparse deconvolution of the signal. The third technique, Multicomponent PFM, exploits further the benefits of sparse estimation to decompose the fMRI signal into a haemodynamical component and a baseline component using the morphological component analysis algorithm. These techniques were evaluated in simulations and experimental fMRI datasets, and the results were compared with well-established fMRI analysis methods. In particular, the methods developed here enabled the detection of single trial BOLD responses to visually-cued and self-paced finger tapping responses without prior information of the events. The potential application of Sparse PFM to identify interictal discharges in idiopathic generalized epilepsy was also investigated. Furthermore, Multicomponent PFM allowed us to extract cardiac and respiratory fluctuations of the signal without the need of physiological monitoring. To sum up, this work demonstrates the feasibility to do single trial fMRI analysis without prior stimulus or physiological information using PFM techniques