The neural basis of cognitive control: Response selection and inhibition

The functional neuroanatomy of tasks that recruit different forms of response selection and inhibition has to our knowledge, never been directly addressed in a single fMRI study using similar stimulus–response paradigms where differences between scanning time and sequence, stimuli, and experimenter instructions were minimized. Twelve right-handed participants were scanned on two standard cognitive control tasks, a stimulus–response incompatibility task, and a response inhibition task. A compound trial design allowed comparison of preparing to inhibit an upcoming automatic response to wholly inhibiting an automatic response. Furthermore, inhibiting an automatic response to perform an alternative task-relevant response was compared to wholly inhibiting an automatic response. No differences were found in prefrontal activity when preparing to inhibit an automatic response was compared to wholly inhibiting an automatic response, suggesting a mostly common network. The left inferior frontal gyrus was found to be commonly recruited during both tasks when controlled responses were required, likely due to its role in response selection. In contrast, the right inferior frontal gyrus was found to be more involved when task demands were stronger for response inhibition. Our results are largely consistent with models of cognitive control that postulate that separate psychological constructs, such as response selection and inhibition, are related processes largely served by a common prefrontal network. This prefrontal network is recruited to a greater or lesser extent depending on specific task demands.     

Neural basis of motor control and its cognitive implications

It has recently been demonstrated that human subjects and nonhuman primates adapt their arm movements when subjected to complex patterns of disturbing forces. The presence of aftereffects following the removal of the disturbing forces indicates that adaptation takes place through the development of an internal model of the disturbing force. The experimental evidence described in this paper has identified some important properties of this internal model: (1) it is limited to a region surrounding that part of the space where the disturbances had been experienced; (2) there is an enhancement of the internal model that depends only on the passage of time; and (3) there is a process of consolidation of the internal model, which takes a minimum of four hours. Anatomically, the substrate of the internal model is distributed; the motor cortex, basal ganglia, and cerebellum are interconnected structures that are active to different degrees during the acquisition of motor skills. Recent investigation of the spinal cord has suggested the existence of modules that organize the motor output in a discrete set of synergies. The outputs of these modules combine by addition, and might thus form the building blocks for the internal models represented by supraspinal structures.     

A neural basis for the development of inhibitory control

The present study explores the neural basis of the development of inhibitory control by combining functional neuroimaging with a parametric manipulation of a go–nogo paradigm. We demonstrate how the maturation of ventral fronto–striatal circuitry underlies the development of this ability. We used event–related fMRI to examine the effect of interference on neural processes involved in inhibitory control in children and adults. Nogo trials were preceded by either 1, 3 or 5 go trials and then compared to one another. Both children and adults showed an increase in errors with increasing interference. Successful response inhibition was associated with stronger activation of prefrontal and parietal regions for children than for adults. In adults, activation in ventralprefrontal regions increased with increasing interference from go trials. Unlike adults, the circuitry appeared to be maximally activated in children when suppressing a behavioral response regardless of the number of preceding responses. Furthermore, activation in ventral fronto–striatal regions correlated with both age and performance. These findings suggest that immature cognition is more susceptible to interference and this is paralleled by maturational differences in underlying fronto–striatal circuitry.     

The neural basis of event-time introspection

We explored the neural mechanisms allowing humans to report the subjective onset times of conscious events. Magnetoencephalographic recordings of neural oscillations were obtained while human subjects introspected the timing of sensory, intentional, and motor events during a forced choice task. Brain activity was reconstructed with high spatio-temporal resolution. Event-time introspection was associated with specific neural activity at the time of subjective event onset which was spatially distinct from activity induced by the event itself. Different brain regions were selectively recruited for introspection of different event types, e.g., the bilateral angular gyrus for introspection of intention. Our results suggest that event-time introspection engages specific neural networks to assess the contents of consciousness. Subjective event times should therefore be interpreted as the result of complex interactions between introspection and experience networks, rather than as direct reproduction of the individual’s conscious state or as a mere post hoc interpretation.     

The neural basis of primate social communication

A sophisticated ability both to generate displays of emotion and to respond to expressive behaviors of other individuals has emerged as a specialization in the course of primate evolution. Studies of the social behavior of nonhuman primates, especially those most related to ourselves, indicate that monkeys and apes are able to interpret social signals so as to assess the motivations of others. Studies of brain activity in monkeys looking at pictures of faces, facial expressions, and body movements, reveal regions of apparent specialized responsiveness to visual social stimuli. The existence of a discrete neural system in humans for cognition which generates a psychological model of others is suggested by patterns of deficit seen in certain neurologic syndromes. Empathy has several components and appears to lie on an evolutionary continuum.Based on a presentation given in New Orleans on February 17, 1990, at the AAAS symposium Empathy in Infancy and Later Development. Supported by the Department of Veterans Affairs.     

The sleeping brain and the neural basis of emotions

In addition to active wake, emotions are generated and experienced in a variety of functionally different states such as those of sleep, during which external stimulation and cognitive control are lacking. The neural basis of emotions can be specified by regarding the multitude of emotion-related brain states, as well as the distinct neuro- and psychodynamic stages (generation and regulation) of emotional experience.     

Influence of mental practice on development of voluntary control of a novel motor acquisition task

The purpose of this investigation was to assess whether mental practice facilitates the development of voluntary control over the recruitment of the abductor hallucis muscle to produce isolated big toe abduction. A sample of convenience of 15 women and 20 men with a mean age of 28.8 yr. (SD=5.7) and healthy feet, who were unable voluntarily to abduct the big toe, were randomly assigned to one of three groups, a mental practice group, a physical practice group, and a group who performed a control movement during practice. Each subject received neuromuscular electrical stimulation to introduce the desired movement prior to each of five practice bouts over a single session lasting 2 hr. Big toe abduction active range of motion and surface electromyographic (EMG) output of the abductor hallucis and extensor digitorum brevis muscles were measured prior to the first practice bout and following each practice bout, yielding seven acquisition trials. Acquisition is defined as an improvement in both active range of motion and in the difference between the integrated EMG of the abductor hallucis and extensor digitorum brevis muscles during successive acquisition trials. Seven members of both the mental and physical practice groups and one member of the control group met the acquisition criteria. Chi-square analysis indicated the group difference was statistically significant, suggesting mental practice was effective for this task.     

The neural basis of haptic object processing.

We review the organization of the neural networks that underlie haptic object processing and compare that organization with the visual system. Haptic object processing is separated into at least two neural pathways, one for geometric properties or shape, and one for material properties, including texture. Like vision, haptic processing pathways are organized into a hierarchy of processing stages, with different stages represented by different brain areas. In addition, the haptic pathway for shape processing may be further subdivided into different streams for action and perception. These streams may be analogous to the action and perception streams of the visual system and represent two points of neural convergence for vision and haptics.     

The neural basis of language talent in bilinguals

In a recent paper, Chee et al. report differences in the patterns of brain activation and deactivation in bilinguals with different levels of proficiency in their second language. Most intriguingly, this research addressed the issue of the neural basis of phonological working memory (PWM), which is crucial in language acquisition, in subjects who were under comparable social pressure to be bilinguals. The results led the authors to suggest that a more readily available working memory system might correlate with the attainment of superior proficiency in a second language.     

The cutaneous saltatory area and its presumed neural basis

The saltatory area, defined as that region of the skin within which two successive and spatinily separated signals will interact to produce apparent mislocalization of the prior signal, is measured by a campimetric technique applied to the palm, finger pad, and volar forearm. As contrasted with earlier measures on larger anatomical units, saltatory areas of the hand region are considerably compressed. Comparisons between cortical receptive fields and saltatory areas lead to speculation concerning the operation of the neural principle of “magnification” in the establishment of saltatory limits. The correspondence of configurational properties of both receptive fields and saltatory areas suggests a commonality of principles underlying both, but demands more information on the temporal dimensions of cortical interaction to confirm the parallelism.     

The neural basis of speech parsing in children and adults

Word segmentation, detecting word boundaries in continuous speech, is a fundamental aspect of language learning that can occur solely by the computation of statistical and speech cues. Fifty‐four children underwent functional magnetic resonance imaging (fMRI) while listening to three streams of concatenated syllables that contained either high statistical regularities, high statistical regularities and speech cues, or no easily detectable cues. Significant signal increases over time in temporal cortices suggest that children utilized the cues to implicitly segment the speech streams. This was confirmed by the findings of a second fMRI run, in which children displayed reliably greater activity in the left inferior frontal gyrus when listening to ‘words’ that had occurred more frequently in the streams of speech they had just heard. Finally, comparisons between activity observed in these children and that in previously studied adults indicate significant developmental changes in the neural substrate of speech parsing.     

The cognitive and neural basis of option generation and subsequent choice

Decision-making research has thoroughly investigated how people choose from a set of externally provided options. However, in ill-structured real-world environments, possible options for action are not defined by the situation but have to be generated by the agent. Here, we apply behavioral analysis (Study 1) and functional magnetic resonance imaging (Study 2) to investigate option generation and subsequent choice. For this purpose, we employ a new experimental task that requires participants to generate options for simple real-world scenarios and to subsequently decide among the generated options. Correlational analysis with a cognitive test battery suggests that retrieval of options from long-term memory is a relevant process during option generation. The results of the fMRI study demonstrate that option generation in simple real-world scenarios recruits the anterior prefrontal cortex. Furthermore, we show that choice behavior and its neural correlates differ between self-generated and externally provided options. Specifically, choice between self-generated options is associated with stronger recruitment of the dorsal anterior cingulate cortex. This impact of option generation on subsequent choice underlines the need for an expanded model of decision making to accommodate choice between self-generated options.     

The neural basis of obligatory decomposition of suffixed words

Recent neurolinguistic studies present somewhat conflicting evidence concerning the role of the inferior temporal cortex (IT) in visual word recognition within the first 200 ms after presentation. On the one hand, fMRI studies of the Visual Word Form Area (VWFA) suggest that the IT might recover representations of the orthographic form of words. On the other hand, influential MEG studies of responses from the occipito-temporal regions around 150 ms post-stimulus onset indicate recognition of letters as opposed to symbols but not a sensitivity to statistical properties of letter strings associated with word form representations. Recent MEG experiments support the position that the IT does represent the visual word forms of morphemes and performs morphological decomposition modulated by the statistical relations between morphemes by 170 ms post presentation (at the M170 response). Responses to heteronyms show that the M170 does not make contact with the mental lexicon where word forms are connected to meanings. We report here an MEG study of pseudo-affixed words like brother, which masked priming studies have shown are decomposed in recognition. If the M170 response from IT does index obligatory morphological decomposition based on visual word forms but not lexical entries, we should find that the statistical relation between pseudo-stem and pseudo-suffix modulates the M170 for pseudo-affixed words, as for truly affixed words. The results of this experiment confirm this prediction. In addition, surface form frequency for these words also modulates the M170, providing some support for dual route recognition for words for which decomposition is a garden path.     

Inhibitory motor control in stop paradigms: review and reinterpretation of neural mechanisms.

What is the neurophysiological locus of inhibition when preparation for a manual response is countermanded? This paper evaluates data and models that pertain to inhibitory mechanisms operating in stop paradigms. In a model of De Jong, Coles and Logan (1995), (Strategies and mechanisms in nonselective and selective inhibitory motor control. Journal of Experimental Psychology: Human Perception and Performance, 21, 3, 498-511), a mechanism for nonselective inhibition operates peripheral to the motor cortex, while a selective mechanism operates at a central cortical level. We argue, however, that a peripheral mechanism of inhibition is incorrectly inferred from inhibition data available to date. Neurophysiological and psychophysiological data suggest that inhibitory processes always involve the cortex, and inhibitory effects are exerted upstream from the primary motor cortex. The prefrontal cortex and basal ganglia are candidate agents of response inhibition, whereas possible sites of inhibition are the thalamus and motor cortex.     

语言认知老化机制及其神经基础

老龄化个体出现的认知障碍在某种程度上是由于语言的认知老化所导致,因此,了解语言认知老化的具体表现、老化机制及其神经基础对于延缓语言认知老化、矫正老年痴呆有重要意义。首先基于理解和产生两个维度,分别从词汇、句子和文本三个层面分析了语言认知老化的表现,而后着重从工作记忆的角度分析了语言认知老化的认知机制,在此基础上,进一步从词汇加工、语义提取、句法分析三个方面分析了语言认知老化的神经基础,并指出半球不对称性减弱和脑区的弥散性激活是语言认知老化的主要神经表现。最后,围绕着语言认知老化的"发展进程、领域表现形式、干预矫正方法"三个必须解决的问题展开讨论,为该领域未来的发展做出理论上的铺垫。