Visual adaptation to goal-directed hand actions

Prolonged exposure to visual stimuli, or adaptation, often results in an adaptation “aftereffect” which can profoundly distort our perception of subsequent visual stimuli. This technique has been commonly used to investigate mechanisms underlying our perception of simple visual stimuli, and more recently, of static faces. We tested whether humans would adapt to movies of hands grasping and placing different weight objects. After adapting to hands grasping light or heavy objects, subsequently perceived objects appeared relatively heavier, or lighter, respectively. The aftereffects increased logarithmically with adaptation action repetition and decayed logarithmically with time. Adaptation aftereffects also indicated that perception of actions relies predominantly on view-dependent mechanisms. Adapting to one action significantly influenced the perception of the opposite action. These aftereffects can only be explained by adaptation of mechanisms that take into account the presence/absence of the object in the hand. We tested if evidence on action processing mechanisms obtained using visual adaptation techniques confirms underlying neural processing. We recorded monkey superior temporal sulcus (STS) single-cell responses to hand actions. Cells sensitive to grasping or placing typically responded well to the opposite action; cells also responded during different phases of the actions. Cell responses were sensitive to the view of the action and were dependent upon the presence of the object in the scene. We show here that action processing mechanisms established using visual adaptation parallel the neural mechanisms revealed during recording from monkey STS. Visual adaptation techniques can thus be usefully employed to investigate brain mechanisms underlying action perception.Publisher PDFPeer reviewe

Aftereffects in the perception of emotion following brief, masked adaptor faces

Adaptation aftereffects are the tendency to perceive an ambiguous target stimulus, which follows an adaptor stimulus, as different from the adaptor. A duration dependence of face adaptation aftereffects has been demonstrated for durations of at least 500ms, for identity related judgments. Here we describe the duration dependence of the adaptation aftereffects of very brief (11.7ms-500ms) backwardly masked faces, on both expression and identity category judgments of ambiguous target faces. We find significant aftereffects at minimum duration 23.5ms for emotional expression, and 47ms for identity, but these are abolished by backward masking with an inverted face, although these same adaptors can be correctly categorized above chance. The presence of a short duration adaptation effect in expression might be mediated by rapid transfer of low spatial frequency (LSF) information. We tested this possibility by comparing aftereffects in low pass and high pass filtered ambiguous targets, and found no evidence of independent adaptation of a LSF specific channel

Visual Aftereffect Of Texture Density Contingent On Color Of Frame

An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow\u27s (1990) model of modifiable inhibition

Visual Learning In The Perception Of Texture: Simple And Contingent Aftereffects Of Texture Density

Novel results elucidating the magnitude, binocularity and retinotopicity of aftereffects of visual texture density adaptation are reported as is a new contingent aftereffect of texture density which suggests that the perception of visual texture density is quite malleable. Texture aftereffects contingent upon orientation, color and temporal sequence are discussed. A fourth effect is demonstrated in which auditory contingencies are shown to produce a different kind of visual distortion. The merits and limitations of error-correction and classical conditioning theories of contingent adaptation are reviewed. It is argued that a third kind of theory which emphasizes coding efficiency and informational considerations merits close attention. It is proposed that malleability in the registration of texture information can be understood as part of the functional adaptability of perception

Adverse Aftereffects of Methotrexate as Chemotherapy on Cognitive Deficits in Rat Models

Patients with acute lymphoblastic leukemia have a high five-year survival rate thanks to methotrexate (MTX). However, cognitive side effects are reported, characterized as chemo brain. The study investigated if impulsiveness is part of the aberrant cognitive functions after being exposed to MTX in the early stage of physical development. Adolescent rats were injected with either phosphate-buffered saline (PBS) or MTX. The novel object recognition (NOR) task was conducted a month after the injections to measure the memory deficits. The discounting task was performed after the rats completed training on a fixed-ratio one schedule for both levers. The NOR test showed both the PBS and MTX rats recognized the novel object; however, the PBS group spent more time inspecting the novel object than the MTX group. Initial results from two rats (one from each group) for the discounting task showed that the PBS-treated rat preferred the immediate reward at the beginning and had increased omissions during the later trials. The MTX rat showed a consistent preference for the immediate lever across the entire procedure. These composite findings suggested cognitive deficits are not apparent within one month of MTX treatment, yet the impulsiveness is more apparent after MTX exposure

Theoretical background of rock failure at hydraulic seam fracture and aftereffect analysis

Purpose. Theoretical substantiation of the methodological foundations of possible effects and aftereffects identification of the hydraulic seam fracture (HSF) technology. Methods. The research structure and procedure includes: studying the power engineering aspect of the rock failure, the acoustical wave effects; thermodynamic analysis of rock failure, analysis of surfaces mechanoactivation at rock failure and aftereffect of the primary pore space self-development at the HSF due to the Rebinder’s effect. Findings. It was established that among the fundamental consistent patterns that determine the formation and development of the HSF technology aftereffects during formations mining, are the methodological provisions and criteria for failure parameters prediction and grinding effects, namely: the average and local energy density of geoenvironment destruction, efficiency of grinding, the average particle and pore size, the specific surface area, the specific energy consumption per unit of the resulting surface. The connection between the parameters of the acoustic wave and the size of the fractures, which forms the basis of the acoustic emission (AE) method, is experimentally confirmed. Originality. It is established that the database for evaluating the expected fracture effects in the working zone of the HSF is: AE activity, specific acoustic radiation, spectrum of signals, characteristic amplitudes under the condition of physical modeling on the model samples of the geoenvironment behavior. It is shown that the critical state of a substance corresponding to the beginning of failure at the microlevel should be considered from the standpoint of thermodynamics as a phase change (evaporation, sublimation) near the critical point, based on the temperature critical values and the specific energy of the phase change. The presence of surfaces mechanoactivation in the rock failure is experimentally proved. The hypothesis concerning the rock pore space development aftereffect during hydraulic seam fracture due to the Rebinder’s effect is presented. Practical implications. It is proposed to size up the degree of geoenvironment destruction in the process of the HSF by the Kd parameter, which is equal to the product of the maximum amplitude of acoustic signals on the total acoustic activity of the destruction zone. It is established that the conditions for rock failure at the HSF are determined by the relationship between the rock pressure P and the volume energy density W of the failure. It is shown that the level of surfaces mechanoactivation can be estimated by adsorption characteristics – the adsorption potential and the pH of the newly discovered surfaces.Мета. Теоретичне обґрунтування методологічних основ встановлення умов прояву можливих ефектів і пост-ефектів технології гідравлічного розриву пласта (ГРП). Методика. Структура та послідовність проведення дослідження включає вивчення енергетичного аспекту руйнування гірського масиву, дії акустичних хвиль, термодинамічний аналіз руйнування гірського масиву, аналіз механоактивації поверхонь при руйнуванні гірського масиву та пост-ефекту саморозвитку первинного пористого простору ГРП внаслідок дії ефекту Ребіндера. Застосовано метод акустичної емісії, потенціометрії та рН-метрії. Результати. Встановлено, що до числа фундаментальних закономірностей, які визначають формування і розвиток пост-ефектів технології ГРП при відпрацюванні продуктивних пластів, відносяться методичні положення й критерії для прогнозу показників руйнування та ефектів подрібнення, а саме: середньої та локальної густини енергії при руйнуванні геосередовища, ККД подрібнення, середній розмір часток і пор, питома поверхня, питомі витрати енергії на одиницю одержаної поверхні. Експериментально підтверджений зв’язок між параметрами акустичної хвилі та розміром тріщин, що складає основу методу акустичної емісії (АЕ). Наукова новизна. Встановлено, що базу інформації для оцінки очікуваних у робочій зоні ГРП ефектів руйнувань складають активність АЕ, питоме акустичне випромінювання, спектр сигналів, характерні амплітуди за умови фізичного моделювання поведінки геосередовища на модельних зразках. Визначено, що граничний стан речовини, що відповідає початку руйнування на мікрорівні, слід розглядати з позицій термодинаміки як фазовий перехід (випаровування, сублімація) поблизу критичної точки, виходячи із критичних значень температури і питомої енергії фазового переходу. Експериментально доведено наявність механоактивації поверхонь при руйнуванні гірського масиву. Висунута гіпотеза щодо пост-ефекту розвитку пористого простору гірського масиву при ГРП у контексті дії ефекту Ребіндера. Практична значимість. Запропоновано оцінювати ступінь руйнування геосередовища у процесі ГРП показником Кр, що дорівнює добутку максимальної амплітуди акустичних сигналів на сумарну акустичну активність зони руйнування. Встановлено, що умови руйнування гірського масиву при ГРП детермінуються співвідношенням між гірським тиском Р і об’ємною густиною енергії W деформації. Показано, що ступінь механоактивації поверхонь може бути оцінена за характеристиками адсорбції – потенціалом адсорбції та показником рН нововідкритих поверхонь.Цель. Теоретическое обоснование методологических основ установления условий проявления возможных эффектов и пост-эффектов технологии гидравлического разрыва пласта (ГРП). Методика. Структура и последовательность проведения исследования включает изучение энергетического аспекта разрушения горного массива, действия акустических волн, термодинамический анализ разрушения горного массива, анализ механоактивации поверхностей при разрушении горного массива и пост-эффекта саморазвития первичного пористого прострагства ГРП в результате действия эффекта Ребиндера. Применен метод акустической эмиссии, потенциометрии и рН-метрии. Результаты. Установлено, что к числу фундаментальных закономерностей, определяющих формирование и развитие пост-эффектов технологии ГРП при отработке продуктивных пластов, относятся методические положения и критерии для прогноза показателей разрушения и эффектов измельчения, а именно: средней и локальной плотности энергии при разрушении геосреды, КПД измельчения, средний размер частиц и пор, удельная поверхность, удельные затраты энергии на единицу полученной поверхности. Экспериментально подтверждена связь между параметрами акустической волны и размером трещин, что составляет основу метода акустической эмиссии (АЭ). Научная новизна. Установлено, что базу информации для оценки ожидаемых в рабочей зоне ГРП эффектов разрушений составляют актитивность АЭ, удельное акустическое излучение, спектр сигналов, характерные амплитуды при условии физического моделирования поведения геосреды на модельных образцах. Определено, что предельное состояние вещества, отвечающее началу разрушения на микроуровне, следует рассматривать с позиций термодинамики как фазовый переход (испарение, сублимация) вблизи критической точки, исходя из критических значений температуры и удельной энергии фазового перехода. Экспериментально доказано наличие механоактивации поверхностей при разрушении горного массива. Выдвинута гипотеза относительно пост-эффекта развития пористого пространства горного массива при ГРП в контексте действия эффекта Ребиндера. Практическая значимость. Предложено оценивать степень разрушения геосреды в процессе ГРП показателем Кр, который равен произведению максимальной амплитуды акустических сигналов на суммарную акустическую активность зоны разрушения. Установлено, что условия разрушения горного массива при ГРП детерминируются соотношением между горным давлением Р и объемной плотностью энергии W деформации. Показано, что степень механоактивации поверхностей может быть оценен по характеристикам адсорбции – потенциалом адсорбции и показателем рН новооткрытых поверхностей.The authors express their gratitude to Doctor of Physical and Mathematical Sciences Vilian Mykolayovych Bovenko for valuable advices when conducting research. In addition, thanks to Doctor of Engineering Sciences Anatolii Dmytrovych Aleksieiev for the opportunity to use a unique research unit of non-uniform triaxial load and research method revision. The authors thank to Candidate of Engineering Sciences Iryna Mykhailivna Yuriivska for consultations on the use of her original method of mechanoactivation study

The Aftereffects of TC Heartland: How to Effectively Approach Motions to Dismiss and Motions to Transfer on the Basis of Improper Venue

Prior to the Supreme Court\u27s decision in TC Heartland, the law of venue in patent infringement actions fluctuated over time. In recent history, the Eastern District of Texas became a notoriously plaintiff-friendly forum in which to litigate patent infringement actions; it was also a widely available choice of forum due to the Court of Appeals for the Federal Circuit\u27s broad reading of the patent venue statute, 28 U.S.C. § 1400(b). However, the Supreme Court in TC Heartland adopted its earlier interpretation of the patent venue statute that is much narrower than subsequent interpretive expansions. This Note surveys and categorizes motions to dismiss and motions to transfer on the basis of improper venue in patent infringement actions in the post-TC Heartland era through an overview of applicable law and an analysis of motion outcomes. The Note concludes with an issue-specific explanation of trends in such motion outcomes, suggests that the Court of Appeals for the Federal Circuit\u27s recent decision to place the burden of proof in these motions on plaintiffs will result in disproportionate victories for defendants, and proposes strategies for plaintiffs to mitigate this burden

Adolescents’ preferences for sexual dimorphism are influenced by relative exposure to male and female faces

Exposure to a particular population of faces can increase ratings of the normality and attractiveness of similar-looking faces. Such exposure can also refine the perceived boundaries of that face population, such that other faces are more readily perceived as dissimilar. We predicted that relatively less exposure to opposite-sex faces, as experienced by children at single-sex compared with mixed-sex schools, would decrease ratings of the attractiveness of sexual dimorphism in opposite-sex faces (that is, boys at single-sex schools would show a decreased preference for feminised faces, and girls at single-sex schools would show a decreased preference for masculinised faces). Consistent with this prediction, girls at single-sex compared with mixed-sex schools demonstrated significantly stronger preferences for facial femininity in both male and female faces. Boys at single-sex compared with mixed-sex schools demonstrated marginally stronger preferences for facial masculinity in male faces, but did not differ in their ratings of female faces. These effects were attenuated among some single-sex school pupils by the presence of adolescent opposite-sex siblings. These data add to the evidence that long-term exposure to a particular face population can influence judgements of other faces, and contribute to our understanding of the factors leading to individual differences in face preferences

Alpha power increase after transcranial alternating current stimulation at alpha frequency (α-tacs) reflects plastic changes rather than entrainment

Background: Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (α) frequency (8–12 Hz) enhances electroencephalographic (EEG) α-oscillation long after tACS-offset. Two mechanisms have been suggested to underlie these changes in oscillatory EEG activity: tACS-induced entrainment of brain oscillations and/or tACS-induced changes in oscillatory circuits by spike-timing dependent plasticity.<p></p> Objective: We tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment “echoes.” To this end, we used a novel, intermittent tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and endogenous α-frequency.<p></p> Methods: 12 healthy participants were stimulated at around individual α-frequency for 15–20 min in four sessions using intermittent tACS or sham. Successive tACS events were either phase-continuous or phase-discontinuous, and either 3 or 8 s long. EEG α-phase and power changes were compared after and between episodes of α-tACS across conditions and against sham.<p></p> Results: α-aftereffects were successfully replicated after intermittent stimulation using 8-s but not 3-s trains. These aftereffects did not reveal any of the characteristics of entrainment echoes in that they were independent of tACS phase-continuity and showed neither prolonged phase alignment nor frequency synchronization to the exact stimulation frequency.<p></p> Conclusion: Our results indicate that plasticity mechanisms are sufficient to explain α-aftereffects in response to α-tACS, and inform models of tACS-induced plasticity in oscillatory circuits. Modifying brain oscillations with tACS holds promise for clinical applications in disorders involving abnormal neural synchrony

The fast contribution of visual-proprioceptive discrepancy to reach aftereffects and proprioceptive recalibration

Adapting reaches to altered visual feedback not only leads to motor changes, but also to shifts in perceived hand location; “proprioceptive recalibration”. These changes are robust to many task variations and can occur quite rapidly. For instance, our previous study found both motor and sensory shifts arise in as few as 6 rotated-cursor training trials. The aim of this study is to investigate one of the training signals that contribute to these rapid sensory and motor changes. We do this by removing the visuomotor error signals associated with classic visuomotor rotation training; and provide only experience with a visual-proprioceptive discrepancy for training. While a force channel constrains reach direction 30o away from the target, the cursor representing the hand unerringly moves straight to the target. The resulting visual-proprioceptive discrepancy drives significant and rapid changes in no-cursor reaches and felt hand position, again within only 6 training trials. The extent of the sensory change is unexpectedly larger following the visual-proprioceptive discrepancy training. Not surprisingly the size of the reach aftereffects is substantially smaller than following classic visuomotor rotation training. However, the time course by which both changes emerge is similar in the two training types. These results suggest that even the mere exposure to a discrepancy between felt and seen hand location is a sufficient training signal to drive robust motor and sensory plasticity.York University Librarie