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The role of HG in the analysis of temporal iteration and interaural correlation
Stress estimation by the prefrontal cortex asymmetry: Study on fNIRS signals
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the brain hemodynamic activity in applications to evaluate affective disorders and stress. Using two
wavelengths of light, it is possible to monitor relative changes in the concentrations of oxyhemoglobin and
deoxyhemoglobin. Besides, the spatial asymmetry in the prefrontal cortex activity has been correlated with the
brain response to stressful situations.
Methods: We measured prefrontal cortex activity with a NIRS multi-distance device during a baseline period,
under stressful conditions (e.g., social stress), and after a recovery phase. We calculated a laterality index for the
contaminated brain signal and for the brain signal where we removed the influence of extracerebral hemodynamic
activity by using a short channel.
Results: There was a significant right lateralization during stress when using the contaminated signals, consistent
with previous investigations, but this significant difference disappeared using the corrected signals. Indeed,
exploration of the susceptibility to contamination of the different channels showed non-homogeneous spatial
patterns, which would hint at detection of stress from extracerebral activity from the forehead.
Limitations: There was no recovery phase between the social and the arithmetic stressor, a cumulative effect was
not considered.
Conclusions: Extracerebral hemodynamic activity provided insights into the pertinence of short channel corrections
in fNIRS studies dealing with emotions. It is important to consider this issue in clinical applications
including modern monitoring systems based on fNIRS technique to assess emotional states in affective disorders
A role for sensory areas in coordinating active sensing motions
Active sensing, which incorporates closed-loop behavioral selection of information during sensory acquisition, is an important feature of many sensory modalities. We used the rodent whisker tactile system as a platform for studying the role cortical sensory areas play in coordinating active sensing motions. We examined head and whisker motions of freely moving mice performing a tactile search for a randomly located reward, and found that mice select from a diverse range of available active sensing strategies. In particular, mice selectively employed a strategy we term contact maintenance, where whisking is modulated to counteract head motion and sustain repeated contacts, but only when doing so is likely to be useful for obtaining reward. The context dependent selection of sensing strategies, along with the observation of whisker repositioning prior to head motion, suggests the possibility of higher level control, beyond simple reflexive mechanisms. In order to further investigate a possible role for primary somatosensory cortex (SI) in coordinating whisk-by-whisk motion, we delivered closed-loop optogenetic feedback to SI, time locked to whisker motions estimated through facial electromyography. We found that stimulation regularized whisking (increasing overall periodicity), and shifted whisking frequency, changes that emulate behaviors of rodents actively contacting objects. Importantly, we observed changes to whisk timing only for stimulation locked to whisker protractions, possibly encoding that natural contacts are more likely during forward motion of the whiskers. Simultaneous neural recordings from SI show cyclic changes in excitability, specifically that responses to excitatory stimulation locked to whisker retractions appeared suppressed in contrast to stimulation during protractions that resulted in changes to whisk timing. Both effects are evident within single whisks. These findings support a role for sensory cortex in guiding whisk-by-whisk motor outputs, but suggest a coupling that depends on behavioral context, occurring on multiple timescales. Elucidating a role for sensory cortex in motor outputs is important to understanding active sensing, and may further provide novel insights to guide the design of sensory neuroprostheses that exploit active sensing context
Affective interaction with a virtual character through an fNIRS brain-computer interface
Affective brain-computer interfaces (BCI) harness Neuroscience knowledge to develop affective interaction from first principles. In this article, we explore affective engagement with a virtual agent through Neurofeedback (NF). We report an experiment where subjects engage with a virtual agent by expressing positive attitudes towards her under a NF paradigm. We use for affective input the asymmetric activity in the dorsolateral prefrontal cortex (DL-PFC), which has been previously found to be related to the high-level affective-motivational dimension of approach/avoidance. The magnitude of left-asymmetric DL-PFC activity, measured using functional near infrared spectroscopy (fNIRS) and treated as a proxy for approach, is mapped onto a control mechanism for the virtual agent’s facial expressions, in which action units (AUs) are activated through a neural network. We carried out an experiment with 18 subjects, which demonstrated that subjects are able to successfully engage with the virtual agent by controlling their mental disposition through NF, and that they perceived the agent’s responses as realistic and consistent with their projected mental disposition. This interaction paradigm is particularly relevant in the case of affective BCI as it facilitates the volitional activation of specific areas normally not under conscious control. Overall, our contribution reconciles a model of affect derived from brain metabolic data with an ecologically valid, yet computationally controllable, virtual affective communication environment
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
Ubiquitous Technologies for Emotion Recognition
Emotions play a very important role in how we think and behave. As such, the emotions we feel every day can compel us to act and influence the decisions and plans we make about our lives. Being able to measure, analyze, and better comprehend how or why our emotions may change is thus of much relevance to understand human behavior and its consequences. Despite the great efforts made in the past in the study of human emotions, it is only now, with the advent of wearable, mobile, and ubiquitous technologies, that we can aim to sense and recognize emotions, continuously and in real time. This book brings together the latest experiences, findings, and developments regarding ubiquitous sensing, modeling, and the recognition of human emotions
An experimental investigation of meniscus roll coating
A two-roll apparatus is used to explore experimentally the detailed fluid mechanics of
meniscus roll coating in which inlets are starved and flow rates are small. Both forward
and reverse modes of operation (with contra- and co-rotating rolls) are investigated
using optical sectioning combined with dye injection and particle imaging techniques.
That part of parameter space where meniscus coating occurs is identified by varying
the roll separation and roll speeds and hence flow rate and capillary number.
Key features of the flow structures identified in the forward mode include two large
eddies (each with saddle point, separatrix and sub-eddies), a primary fluid transfer
jet and the existence of two critical flow rates associated with the switching-on of
a second fluid transfer jet and the switching-off of the primary transfer jet followed
by a change in the flow structure. In the reverse mode, the key features are a single
large eddy consisting of two sub-eddies, a saddle point and separatrix, a primary
fluid transfer jet and once again two critical flow rates. These correspond to (i) the
switching-on of a secondary transfer jet and (ii) the disappearance of a saddle point
at the nip resulting in the merger of the primary and secondary transfer jets.
Measurements of film thickness and meniscus location made over a range of speed
ratios and capillary numbers are compared with theoretical predictions. A plate-roll
apparatus is used to confirm the presence, for very small flow rates, of a sub-ambient,
almost linear, pressure profile across the bead. Investigated also is the transition from
inlet-starved to fully flooded roll coating as flow rate is increased and the changes in
flow structure and pressure profile are observed
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