The transition between stochastic and deterministic behavior in an excitable gene circuit

We explore the connection between a stochastic simulation model and an ordinary differential equations (ODEs) model of the dynamics of an excitable gene circuit that exhibits noise-induced oscillations. Near a bifurcation point in the ODE model, the stochastic simulation model yields behavior dramatically different from that predicted by the ODE model. We analyze how that behavior depends on the gene copy number and find very slow convergence to the large number limit near the bifurcation point. The implications for understanding the dynamics of gene circuits and other birth-death dynamical systems with small numbers of constituents are discussed.Comment: PLoS ONE: Research Article, published 11 Apr 201

Technology-Enhanced Reading Therapy for People With Aphasia: Findings From a Quasirandomized Waitlist Controlled Study.

Purpose This study investigated the effects of technology-enhanced reading therapy for people with reading impairments, using mainstream assistive reading technologies alongside reading strategies. Method The study used a quasirandomized waitlist controlled design. Twenty-one people with reading impairments following stroke were randomly assigned to receive 14 hr of therapy immediately or after a 6-week delay. During therapy, participants were trained to use assistive reading technology that offered a range of features to support reading comprehension. They developed skills in using the technology independently and in applying the technology to their personal reading goals. The primary outcome measure assessed reading comprehension, using Gray Oral Reading Test-Fourth Edition (GORT-4). Secondary measures were as follows: Reading Comprehension Battery for Aphasia-Second Edition, Reading Confidence and Emotions Questionnaire, Communication Activities of Daily Living-Second Edition, Visual Analog Mood Scales, and Assessment of Living With Aphasia. Matched texts were used with the GORT-4 to compare technology-assisted and unassisted reading comprehension. Mixed analyses of variance explored change between T1 and T2, when the immediate group had received therapy but the delayed group had not, thus serving as untreated controls. Pretherapy, posttherapy, and follow-up scores on the measures were also examined for all participants. Results GORT-4 results indicated that the immediately treated group improved significantly in technology-assisted reading following therapy, but not in unassisted reading. However, the data were not normally distributed, and secondary nonparametric analysis was not significant. The control group was unstable over the baseline, improving significantly in unassisted reading. The whole-group analysis showed significant gains in assisted (but not unassisted) reading after therapy that were maintained at follow-up. The Reading Confidence and Emotions Questionnaire results improved significantly following therapy, with good maintenance of change. Results on all other secondary measures were not significant. Conclusions Technology-assisted reading comprehension improved following the intervention, with treatment compensating for, rather than remediating, the reading impairment. Participants' confidence and emotions associated with reading also improved. Gains were achieved after 14 therapy sessions, using assistive technologies that are widely available and relatively affordable, meaning that this approach could be implemented in clinical practice

Lexical Retrieval Behaviors of Subjects With Aphasia and Subjects Without Brain Damage on a Rebus Riddle Task

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Motivation and Motor Control: Hemispheric Specialization for Approach Motivation Reverses with Handedness

(SSH), according to which the hemispheric laterality of affective motivation depends on the laterality of motor control for the dominant hand (i.e., the “sword hand," used preferentially to perform approach actions) and the nondominant hand (i.e., the “shield hand," used preferentially to perform avoidance actions).To determine whether the laterality of approach motivation varies with handedness, we measured alpha-band power (an inverse index of neural activity) in right- and left-handers during resting-state electroencephalography and analyzed hemispheric alpha-power asymmetries as a function of the participants' trait approach motivational tendencies. Stronger approach motivation was associated with more left-hemisphere activity in right-handers, but with more right-hemisphere activity in left-handers.The hemispheric correlates of approach motivation reversed between right- and left-handers, consistent with the way they typically use their dominant and nondominant hands to perform approach and avoidance actions. In both right- and left-handers, approach motivation was lateralized to the same hemisphere that controls the dominant hand. This covariation between neural systems for action and emotion provides initial support for the SSH