Frontal-Sensory Cortical Projections Become Dispensable for Attentional Performance Upon a Reduction of Task Demand in Mice

Top-down attention is a dynamic cognitive process that facilitates the detection of the task-relevant stimuli from our complex sensory environment. A neural mechanism capable of deployment under specific task-demand conditions would be crucial to efficiently control attentional processes and improve promote goal-directed attention performance during fluctuating attentional demand. Previous studies have shown that frontal top-down neurons projecting from the anterior cingulate area (ACA) to the visual cortex (VIS; ACAVIS) are required for visual attentional behavior during the 5-choice serial reaction time task (5CSRTT) in mice. However, it is unknown whether the contribution of these projecting neurons is dependent on the extent of task demand. Here, we first examined how behavior outcomes depend on the number of locations for mice to pay attention and touch for successful performance, and found that the 2-choice serial reaction time task (2CSRTT) is less task demanding than the 5CSRTT. We then employed optogenetics to demonstrate that suppression ACAVIS projections immediately before stimulus presentation has no effect during the 2CSRTT in contrast to the impaired performance during the 5CSRTT. These results suggest that ACAVIS projections are necessary when task demand is high, but once a task demand is lowered, ACAVIS neuron activity becomes dispensable to adjust attentional performance. These findings support a model that the frontal-sensory ACAVIS projection regulates visual attention behavior during specific high task demand conditions, pointing to a flexible circuit-based mechanism for promoting attentional behavior.

Роль интерференции в имплицитном усвоении последовательностей Струп-стимулов

Введение. Феномен интерференции позволяет выявлять существенные характеристики процесса формирования нового знания. Новизна данного исследования заключается в использовании эффекта интерференции для диссоциации эксплицитного и имплицитного научения. Проверялось предположение о том, что эффект интерференции, возникающий при реагировании на Струп-стимулы, снижает продуктивность приобретения эксплицитного знания последовательности, но не оказывает значимого влияния на имплицитное усвоение последовательности. Методы. В исследовании приняли участие 80 человек (средний возраст 22,7 лет). В эксперименте использовались задачи «the serial reaction time task», в которых требуется быстро и точно реагировать на последовательно предъявляемые стимулы. Одним испытуемым (n = 40) предъявлялись названия цветов, написанные шрифтом конгруэнтного (соответствующего) цвета, другим испытуемым (n = 40) демонстрировались названия цветов, написанные шрифтом неконгруэнтного (несоответствующего) цвета (Струп-стимулы). Требовалось, не читая слова, реагировать на цвет шрифта, которым оно написано. Для выявления эксплицитного знания последовательности использовался тест узнавания фрагментов последовательности (the recognition test). Результаты. Полученные результаты выявили статистически значимый эффект усвоения последовательности у испытуемых, выполнявших задание в конгруэнтных и неконгруэнтных условиях. При этом все испытуемые продемонстрировали низкий уровень эксплицитного знания последовательности (не более 51,9 % правильных ответов в тесте узнавания). Установлено, что имплицитное выучивание последовательности позволяет устранить эффект интерференции (задержку во времени реакции на неконгруэнтные стимулы). Обсуждение результатов. Результаты подтвердили предположение о том, что эффект интерференции не снижает продуктивность имплицитного усвоения последовательности. Отсутствие значимых различий между группами, реагировавшими на конгруэнтные и неконгруэнтные стимулы, не позволяет в полной мере оценить влияние эффекта интерференции на эксплицитное усвоение последовательности. В целом данные проведенного исследования свидетельствуют в поддержку того, что эффект интерференции затрудняет экспликацию структуры последовательности.

Adaptive aspects of impulsivity and interactions with effects of catecholaminergic agents in the 5-choice serial reaction time task: implications for ADHD

Background Work in humans has shown that impulsivity can be advantageous in certain settings. However, evidence for so-called functional impulsivity is lacking in experimental animals. Aims This study investigated the contexts in which high impulsive (HI) rats show an advantage in performance compared with mid- (MI) and low impulsive (LI) rats. We also assessed the effects of dopaminergic and noradrenergic agents to investigate underlying neurotransmitter mechanisms. Methods We tested rats on a variable inter-trial interval (ITI) version of the 5-choice serial reaction time task (5CSRTT). Rats received systemic injections of methylphenidate (MPH, 1 mg/kg and 3 mg/kg), atomoxetine (ATO, 0.3 mg/kg and 1 mg/kg), amphetamine (AMPH, 0.2 mg/kg), the alpha-2a adrenoceptor antagonist atipamezole (ATI, 0.3 mg/kg) and the alpha-1 adrenoceptor agonist phenylephrine (PHEN, 1 mg/kg) prior to behavioural testing. Results Unlike LI rats, HI rats exhibited superior performance, earning more reinforcers, on short ITI trials, when the task required rapid responding. MPH, AMPH and ATI improved performance on short ITI trials and increased impulsivity in long ITI trials, recapitulating the behavioural profile of HI. In contrast, ATO and PHEN impaired performance on short ITI trials and decreased impulsivity, thus mimicking the behavioural profile of LI rats. The effects of ATO were greater on MI rats and LI rats. Conclusions These findings indicate that impulsivity can be advantageous when rapid focusing and actions are required, an effect that may depend on increased dopamine neurotransmission. Conversely, activation of the noradrenergic system, with ATO and PHEN, led to a general inhibition of responding.

Task Demand-dependent Contribution of Frontal-Sensory Cortical Projections to Attentional Behavior in Mice

Top-down attention is a dynamic cognitive process that facilitates the detection of the task-relevant stimuli from our complex sensory environment. A neural mechanism capable of deployment under specific task-demand conditions would be crucial to efficiently control attentional processes and improve goal-directed attention performance in task demand-dependent manner. Previous studies have shown that frontal top-down neurons projecting from anterior cingulate area (ACA) to the visual cortex (VIS; ACAvis) are required for attentional behavior during the 5-choice serial reaction time task (5CSRTT) in mice. However, it is unknown whether the contribution of this projecting neurons is dependent on the extent of task demand. Here, we examine the differential contribution of ACAvis projection neurons to the attentional behavior in adult male mice performing two visual attention tasks of varying task demand: the 5CSRTT and 2-choice serial reaction time task (2CSRTT). We found that optogenetic suppression ACAvis projections immediately before stimulus presentation has no effect during the 2CSRTT in contrast to the impaired performance during the 5CSRTT. Fiber photometry calcium imaging of ACAvis neuron activity revealed that these neurons, which are recruited after errors during 5CSRTT, are not recruited during 2CSRTT. These results suggest that ACAvis projections are necessary only when task demand is high and that ACAvis neuron activity may not provide an error monitoring signal when task demand is low. Collectively, this frontal-sensory ACAvis projection regulates visual attention behavior during specific high task demand conditions, pointing to a flexible circuit-based mechanism for promoting attentional behavior.