Neuronal correlates of decisions to speak and act: Spontaneous emergence and dynamic topographies in a computational model of frontal and temporal areas

The neural mechanisms underlying the spontaneous, stimulus-independent emergence of intentions and decisions to act are poorly understood. Using a neurobiologically realistic model of frontal and temporal areas of the brain, we simulated the learning of perception–action circuits for speech and hand-related actions and subsequently observed their spontaneous behaviour. Noise-driven accumulation of reverberant activity in these circuits leads to their spontaneous ignition and partial-to-full activation, which we interpret, respectively, as model correlates of action intention emergence and action decision-and-execution. Importantly, activity emerged first in higher-association prefrontal and temporal cortices, subsequently spreading to secondary and finally primary sensorimotor model-areas, hence reproducing the dynamics of cortical correlates of voluntary action revealed by readiness-potential and verb-generation experiments. This model for the first time explains the cortical origins and topography of endogenous action decisions, and the natural emergence of functional specialisation in the cortex, as mechanistic consequences of neurobiological principles, anatomical structure and sensorimotor experience.     

A time of change: Behavioral and neural correlates of adolescent sensitivity to appetitive and aversive environmental cues

Adolescence is a developmental period that entails substantial changes in affective and incentive-seeking behavior relative to both childhood and adulthood, including a heightened propensity to engage in risky behaviors and experience persistent negative and labile mood states. This review discusses the emotional and incentive-driven behavioral changes in adolescents and their associated neural mechanisms, focusing on the dynamic interactions between the amygdala, ventral striatum, and prefrontal cortex. Common behavioral changes during adolescence may be associated with a heightened responsiveness to incentives and emotional cues while the capacity to effectively engage in cognitive and emotion regulation is still relatively immature. We highlight empirical work in humans and animals that addresses the interactions between these neural systems in adolescents relative to children and adults, and propose a neurobiological model that may account for the nonlinear changes in adolescent behavior. Finally, we discuss other influences that may contribute to exaggerated reward and emotion processing associated with adolescence, including hormonal fluctuations and the role of the social environment.     

Refining the visual-cortical hypothesis in category learning

Participants produce steep typicality gradients and large prototype-enhancement effects in dot-distortion category tasks, showing that in these tasks to-be-categorized items are compared to a prototypical representation that is the central tendency of the participant’s exemplar experience. These prototype-abstraction processes have been ascribed to low-level mechanisms in primary visual cortex. Here we asked whether higher-level mechanisms in visual cortex can also sometimes support prototype abstraction. To do so, we compared dot-distortion performance when the stimuli were size constant (allowing some low-level repetition-familiarity to develop for similar shapes) or size variable (defeating repetition-familiarity effects). If prototype formation is only mediated by low-level mechanisms, stimulus-size variability should lessen prototype effects and flatten typicality gradients. Yet prototype effects and typicality gradients were the same under both conditions, whether participants learned the categories explicitly or implicitly and whether they received trial-by-trial reinforcement during transfer tests. These results broaden out the visual-cortical hypothesis because low-level visual areas, featuring retinotopic perceptual representations, would not support robust category learning or prototype-enhancement effects in an environment of pronounced variability in stimulus size. Therefore, higher-level cortical mechanisms evidently can also support prototype formation during categorization.     

The level of frontal-temporal beta-2 band EEG synchronization distinguishes anterior cingulate cortex from other frontal regions

Recent findings indicate that complex cognitive functions are organized at a global level in the brain and rely on large-scale information processing requiring functional integration of multiple disparate neural assemblies. The critical question of the integration of distributed brain activities is whether the essential integrative role can be attributed to a specific structure in the brain or whether this ability is inherent to the cognitive network as a whole. The results of the present study show that mean values of the running correlation function in frontal-temporal EEG pairs with one electrode in the anterior cingulate cortex (ACC) are significantly higher than the same values in other frontal-temporal pairs. These findings indicate a particular role of the ACC in large-scale communication, which could reflect its unique integrative functions in cognitive processing.     

The neural correlates of movement intentions: A pilot study comparing hypnotic and simulated paralysis

The distinct feeling of wanting to act and thereby causing our own actions is crucial to our self-perception as free human agents. Disturbances of the link between intention and action occur in several disorders. Little is known, however, about the neural correlates of wanting or intending to act. To investigate these for simple voluntary movements, we used a paradigm involving hypnotic paralysis and functional magnetic resonance imaging. Eight healthy women were instructed to sequentially perform left and right hand movements during a normal condition, as well as during simulated weakness, simulated paralysis and hypnotic paralysis of the right hand. Right frontopolar cortex was selectively hypoactivated for attempted right hand movement during simulated paralysis while it was active in all other conditions. Since simulated paralysis was the only condition lacking an intention to move, the activation in frontopolar cortex might be related to the intention or volition to move.     

“啊哈！”和“哈哈！”：顿悟与幽默的脑认知成分比较

作为人类智能的高级表现形式, 顿悟和幽默存在诸多共同之处。从认知和情感组成上看, 顿悟的非连续性、突发性、重构和惊讶, 对应于幽默的失谐、失谐探测、失谐消解和愉悦, 两者存在表征机制的重叠。神经机制的研究发现, 顿悟和幽默的心理事件都伴随着400 ms左右的额中央区负波(N400)以及前扣带回、顶颞叶联合区和前额叶等脑区的活动; 同时顿悟和幽默在P300成分以及海马、右侧前部颞上回等脑区活动上存在差异。未来可借鉴幽默的认知和情感成份的脑成像研究范式, 进一步探明顿悟过程的认知和情感组成。     

Are the inhibitory and faciliatory effects during retrieval of semantically related items present in amnestic mild cognitive impairment?

Prefrontal functions subserve inhibition control for retrieval of semantically related items inducing forgetting 19 a-MCI patients and 29 controls underwent neuropsychological evaluation and retrieval-practice paradigm (RPP) to estimate baseline remember (BR), retrieval-induced facilitation (FAC) and retrieval-induced forgetting (RIF). A-MCI patients underwent also 3 T-MRI to assess relationship between regional grey matter (rGM) volumes and RPP indexes Behaviourally, RIF and FAC were both observed controls, while RIF only was observed in a-MCI patients. In patients but not in controls, RIF was associated with cognitive efficiency and FAC with memory performance. Patients showed also associations between BR and rGM volumes in the precuneus, no association was found between rGM volumes and RIF and FAC. A-MCI patients did not benefit from repeated practice during retrieval of studied items, which is likely due to their memory disorder. In contrast, patient cognitive efficiency would drive retrieval suppression of interfering stimuli.     

Cognitive Control in the Face of Fear: Reduced Cognitive-Emotional Flexibility in Women with a History of Child Abuse

Child abuse can negatively affect neurobiological systems involved in regulating emotions. Adults who were maltreated as children show diminished capacity to flexibly integrate the prefrontal and limbic circuits underlying emotion regulation. Using a facial identification Stroop task with nonemotional and emotional stimuli, we found that women who reported more childhood abuse (N = 44) were no different from women reporting less childhood abuse (N = 45) on nonemotional conflict adaptation, but were significantly less able to adapt to emotional conflict. Women who reported more abuse were especially impaired in adapting to emotional conflict when incongruent stimuli involved a fearful face. These results help characterize the relation between cognitive control and emotion regulation and highlight the far-reaching effects of childhood abuse on cognitive-emotional flexibility.