Functional neuroimaging of cognition: state-of-the-art

This paper presents a brief overview of functional neuroimaging studies of cognitive processes. A "publication profile" is identified for PET and fMRI studies of cognitive functions. It is shown that the number of publications has increased exponentially over the last ten years, and that a set of ten journals accounts for the vast majority of publications. It is argued that the field has moved from a state of explorative character to a state of high theoretical sophistication. With special reference to the contributions in this issue of Scandinavian Journal of Psychology, methodological, topical, regional, and clinical implications of cognitive neuroscientific studies are discussed.     

Flexibility and variability: Essential to human cognition and the study of human cognition

Traditional theories of cognition concentrate on the problem of stability, how it is that people perform the same cognitive act over and over despite different task pressures and varying circumstances. We suggest a different approach that focuses on the flexible and the inventive. From a dynamic systems perspective, intelligence is the adaptive flexibility that integrates the stability of past experience with the idiosyncrasies of the moment. In this paper we demonstrate the value of this perspective in the context of children's novel noun generalizations. We describe D-ALA, a dynamic systems model that embodies the principles of the account and use this model to explain the findings of three different experiments that show how young children flexibly and smartly adapt to novel circumstances in the task of learning new words.     

Integrating rewards and cognition in the frontal cortex

Research indicates that the dorsolateral prefrontal cortex (DLPFC) contributes to working memory and executive control, whereas the ventral frontal cortex (VFC) contributes to affective and motivational processing. Few studies have examined both the functional specificity and the integration of these regions. We did so using fMRI and a verbal working memory task in which visual cues indicated whether recall performance on an upcoming trial would be linked to a monetary reward. On the basis of prior findings obtained in delayed response tasks performed by nonhuman primates, we hypothesized that (1) VFC would show an increase only in response to a cue indicating potential for a monetary reward; (2) DLPFC would show sustained activity across a delay interval for all trials, though activity in rewarded trials would be enhanced; and (3) regions engaged in speech-based rehearsal would be relatively insensitive to monetary incentive. Our hypotheses about DLPFC and rehearsal-related regions were confirmed. In VFC regions, we failed to observe statistically significant effects of reward when the cue or delay epochs of the task were examined in isolation. However, an unexpected and significant deactivation was observed in VFC during the delay epoch; furthermore, a post hoc voxelwise analysis indicated a complex interaction between (1) the cue and delay epochs of the task and (2) the reward value of the trials. The pattern of activation and deactivation across trial types suggests that VFC is sensitive to reward cues, and that portions of DLPFC and VFC may work in opposition during the delay epoch of a working memory task in order to facilitate task performance.     

Integrating cognitive psychology, neurology and neuroimaging

In the last decade, there has been a dramatic increase in research effectively integrating cognitive psychology, functional neuroimaging, and behavioral neurology. This new work is typically conducting basic research into aspects of the human mind and brain. The present review features as examples of such integrations two series of studies by the author and his colleagues. One series, employing object recognition, mental motor imagery, and mental rotation paradigms, clarifies the nature of a cognitive process, imagined spatial transformations used in shape recognition. Among other implications, it suggests that when recognizing a hand's handedness, imagining one's body movement depends on cerebrally lateralized sensory-motor structures and deciding upon handedness depends on exact match shape confirmation. The other series, using cutaneous, tactile, and auditory pitch discrimination paradigms, elucidates the function of a brain structure, the cerebellum. It suggests that the cerebellum has non-motor sensory support functions upon which optimally fine sensory discriminations depend. In addition, six key issues for this integrative approach are reviewed. These include arguments for the value and greater use of: rigorous quantitative meta-analyses of neuroimaging studies; stereotactic coordinate-based data, as opposed to surface landmark-based data; standardized vocabularies capturing the elementary component operations of cognitive and behavioral tasks; functional hypotheses about brain areas that are consistent with underlying microcircuitry; an awareness that not all brain areas implicated by neuroimaging or neurology are necessarily directly involved in the associated cognitive or behavioral task; and systematic approaches to integrations of this kind.     

Integrating functional neuroimaging and human operant research: brain activation correlated with presentation of discriminative stimuli

Results of numerous human imaging studies and nonhuman neurophysiological studies on "reward" highlight a role for frontal, striatal, and thalamic regions in operant learning. By integrating operant and functional neuroimaging methodologies, the present investigation examined brain activation to two types of discriminative stimuli correlated with different contingencies. Prior to neuroimaging, 10 adult human subjects completed operant discrimination training in which money was delivered following button pressing (press-money contingency) in the presence of one set of discriminative stimuli, and termination of trials followed not responding (no response-next trial contingency) in the presence of a second set of discriminative stimuli. After operant training, subjects were instructed to memorize a third set of control stimuli unassociated with contingencies. Several hours after training, functional magnetic resonance imaging was performed while subjects viewed discriminative and control stimuli that were presented individually for 1,500 ms per trial, with stimulus presentations occurring, on average, every 6 s. Activation was found in frontal and striatal brain regions to both sets of discriminative stimuli relative to control stimuli. In addition, exploratory analyses highlighted activation differences between discriminative stimuli. The results demonstrate the utility of coupling operant and imaging technologies for investigating the neural substrates of operant learning in humans.     

Introduction to the special section on aging, cognition, and neuroimaging

In response to the recent increase in the number of laboratories engaged in the use of functional and structural neuroimaging to study cognitive aging, this special section has been compiled to serve as an entry into this area for the readers of Psychology and Aging. These articles are representative of the field and cover many of the issues faced by researchers in this area. This introduction presents some background into the techniques that are used and provides an overview of the articles.     

Social cognition and the human brain

Humans are exceedingly social animals, but the neural underpinnings of social cognition and behavior are not well understood. Studies in humans and other primates have pointed to several structures that play a key role in guiding social behaviors: the amygdala, ventromedial frontal cortices, and right somatosensory-related cortex, among others. These structures appear to mediate between perceptual representations of socially relevant stimuli, such as the sight of conspecifics, and retrieval of knowledge (or elicitation of behaviors) that such stimuli can trigger. Current debates concern the extent to which social cognition draws upon processing specialized for social information, and the relative contributions made to social cognition by innate and acquired knowledge.     

Developmental neuroimaging of the human ventral visual cortex

Here, we review recent results that investigate the development of the human ventral stream from childhood, through adolescence and into adulthood. Converging evidence suggests a differential developmental trajectory across ventral stream regions, in which face-selective regions show a particularly long developmental time course, taking more than a decade to become adult-like. We discuss the implications of these recent findings, how they relate to age-dependent improvements in recognition memory performance and propose possible neural mechanisms that might underlie this development. These results have important implications regarding the role of experience in shaping the ventral stream and the nature of the underlying representations.     

Functional neuroimaging studies of human emotions

Neuroimaging studies with positron emission tomography and functional magnetic resonance imaging have begun to describe the functional neuroanatomy of human emotion. Taken separately, specific studies vary in task dimensions and in type(s) of emotion studied, and are limited by statistical power and sensitivity. By examining findings across studies in a meta-analysis, we sought to determine if common or segregated patterns of activations exist in different emotions and across various emotional tasks. We surveyed over 55 positron emission tomography and functional magnetic resonance imaging activation studies, which investigated emotion in healthy subjects. This paper will review observations in several regions of interest in limbic (eg, amygdala, anterior cingulate cortex) and paralimbic (eg, medial prefrontal cortex, insula) brain regions in emotional responding.     

The use of electrophysiology in the study of early development

Electrophysiology is a timely and important tool in the study of early cognitive development. This commentary polishes the definition of event‐related potential (ERP) components; often interpreted as expressions of mental processes. Further, attention is drawn to time‐frequency analysis of the electroencephalogram (EEG) which conveys much more information than the exclusive use of traditional ERP methodology. Several studies have shown that frequency bands of the EEG undergo systematic development in early childhood. EEG frequency analysis has a potential in early risk assessment. 40 Hz gamma range oscillation bursts accompany stimulus feature binding both in infants and in adults, probably indexing grouping and selection of distributed neuronal populations. Methodological concerns are noted and the need for long‐term normative studies is stressed. Copyright © 2005 John Wiley & Sons, Ltd.     

Dissociating sources of dual-task interference using human electrophysiology

In the psychological refractory period (PRP) paradigm, two unmasked targets are presented, each of which requires a speeded response. Response times to the second target (T2) are slowed when T2 is presented shortly after the first target (T1). Electrophysiological studies have previously shown that the P3 event-related potential component is not delayed during T2 response slowing in the PRP paradigm, but that the lateralized readiness potential is delayed, which suggests a bottleneck on response selection operations but not on stimulus identification. Recently, researchers (Arnell & Duncan, 2002; Jolicoeur & Dell'Acqua, 1999) observed T2 response slowing in an encoding-speeded response (ESR) paradigm where T2 followed a masked T1 that required identification but not a speeded response. T2 response slowing in the ESR paradigm is often indistinguishable from that in the PRP paradigm, prompting some researchers to postulate a common processing bottleneck for the two paradigms. With the use of the ESR paradigm, we observed T2 response slowing and, in contrast to the PRP paradigm, we also observed corresponding P3 delays. The results suggest that dissociable bottlenecks underlie the dual-task costs from the two paradigms.