Improving reverse neuroimaging inference: cognitive domain versus cognitive complexity.
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Brain↗
Biomedical subjects
Kalina Christoff
Publications and source records attributed to Kalina Christoff.
The role of the prefrontal cortex in the maintenance of verbal working memory: an event-related FMRI analysis.
Neuroimaging studies have been inconclusive in characterizing the role of the prefrontal cortex (PFC) for maintaining increasingly larger amounts of information in working memory (WM). To address this question, the authors collected event-related functional MRI data while participants performed an item-recognition task in which the number of to-be-remembered letters was parametrically modulated. During maintenance of information in WM, the dorsolateral and the ventrolateral PFC exhibited linearly increasing activation in response to increasing WM load. Prefrontal regions could not be distinguished from one another on the basis of load sensitivity, but the dorsolateral PFC had stronger functional connectivity with the parietal and motor cortex than the ventrolateral PFC. These results suggest an increasingly important role for the PFC in actively maintaining information as the amount of that information increases.
Adult↗
Learned regulation of spatially localized brain activation using real-time fMRI.
It is not currently known whether subjects can learn to voluntarily control activation in localized regions of their own brain using neuroimaging. Here, we show that subjects were able to learn enhanced voluntary control over task-specific activation in a chosen target region, the somatomotor cortex. During an imagined manual action task, subjects were provided with continuous direction regarding their cognitive processes. Subjects received feedback information about their current level of activation in a target region of interest (ROI) derived using real-time functional magnetic resonance imaging (rtfMRI), and they received automatically-adjusted instructions for the level of activation to achieve. Information was provided both as continously upated graphs and using a simple virtual reality interface that provided an image analog of the level of activation. Through training, subjects achieved an enhancement in their control over brain activation that was anatomically specific to the target ROI, the somatomotor cortex. The enhancement took place when rtfMRI-based training was provided, but not in a control group that received similar training without rtfMRI information, showing that the effect was not due to conventional, practice-based neural plasticity alone. Following training, using cognitive processes alone subjects could volitionally induce fMRI activation in the somatomotor cortex that was comparable in magnitude to the activation observed during actual movement. The trained subjects increased fMRI activation without muscle tensing, and were able to continue to control brain activation even when real-time fMRI information was no longer provided. These results show that rtfMRI information can be used to direct cognitive processes, and that subjects are able to learn volitionally regulate activation in an anatomically-targeted brain region, surpassing the task-driven activation present before training.
Arousal↗
Neural correlates of the automatic processing of threat facial signals.
The present study examined whether automaticity, defined here as independence from attentional modulation, is a fundamental principle of the neural systems specialized for processing social signals of environmental threat. Attention was focused on either scenes or faces presented in a single overlapping display. Facial expressions were neutral, fearful, or disgusted. Amygdala responses to facial expressions of fear, a signifier of potential physical attack, were not reduced with reduced attention to faces. In contrast, anterior insular responses to facial expressions of disgust, a signifier of potential physical contamination, were reduced with reduced attention. However, reduced attention enhanced the amygdala response to disgust expressions; this enhanced amygdala response to disgust correlated with the magnitude of attentional reduction in the anterior insular response to disgust. These results suggest that automaticity is not fundamental to the processing of all facial signals of threat, but is unique to amygdala processing of fear. Furthermore, amygdala processing of fear was not entirely automatic, coming at the expense of specificity of response. Amygdala processing is thus specific to fear only during attended processing, when cortical processing is undiminished, and more broadly tuned to threat during unattended processing, when cortical processing is diminished.
Adolescent↗
Evaluating self-generated information: anterior prefrontal contributions to human cognition.
The anterior or rostrolateral prefrontal cortex (RLPFC) is frequently recruited during complex cognitive tasks across a wide range of domains, including reasoning, long-term memory retrieval, and working memory. The authors report an event-related functional MRI study, indicating that the RLPFC is specifically involved in the evaluation of internally generated information--or information that cannot be readily perceived from the external environment but has to be inferred or self-generated. The findings are consistent with a hierarchical model of lateral prefrontal organization, with RLPFC contributing only at the highest orders of cognitive transformations. This characterization of RLPFC function may help explain seemingly disparate findings across multiple cognitive domains and could provide a unified account of this region's contribution to human cognition.
Adolescent↗
Neural basis of spontaneous thought processes.
Studies examining thought processes have focused upon the deliberate, goal-directed mental processes occurring during complex cognitive tasks. Spontaneously occurring thought processes have, on the other hand, received much less attention. Such spontaneous thought processes occur frequently when no task is present or when task demands are low. Although their existence has been recognised, their study has been difficult due to lack of direct behavioural measures. Nevertheless, a number of behavioural methods based on subjects' verbal reports have been developed. Findings derived using such behavioural methods suggest that spontaneous thought processes share common cognitive mechanisms with purposeful, task-related thought processes. Furthermore, evidence from neuroimaging observations is accumulating suggesting similar conclusions about the neural basis of spontaneous thought processes. These neuroimaging findings demonstrate an overlap in the pattern of activation between various cognitive tasks and rest, with a number of higher cortical regions activated in common, including visual areas, medial temporal lobe, and lateral cortical association areas. Many of these observations have, however, been based upon comparisons between rest and tasks posing relatively high cognitive demands. In contrast, here we report an fMRI study in which rest was compared to a simple left/right response task of minimal cognitive demands. Rest was associated with greater activation in temporopolar cortex, parahippocampus, rostrolateral prefrontal cortex, parietal and visual cortical areas. Activation of temporal lobe structures was particularly extensive and robust, suggesting that long-term memory processes may form the core of spontaneous thought. By considering such long-term memory processes as an essential part of thought mechanisms, it may be possible to gain better understanding into spontaneous thought phenomena that have remained unaccounted for until now.
Adolescent↗