Showing papers by "Raymond J. Dolan published in 2000"

Dissociable Functions in the Medial and Lateral Orbitofrontal Cortex: Evidence from Human Neuroimaging Studies

Abstract: Recent imaging studies show that the orbitofrontal cortex (OFC) is activated during a wide variety of paradigms, including guessing tasks, simple delayed matching tasks and sentence completion. We suggest that, as with other regions of the prefrontal cortex, activity in the OFC is most likely to be observed when there is insufficient information available to determine the appropriate course of action. In these circumstances the OFC, rather than other prefrontal regions, is more likely to be activated when the problem of what to do next is best solved by taking into account the likely reward value of stimuli and responses, rather than their identity or location. We suggest that selection of stimuli on the basis of their familiarity and responses on the basis of a feeling of 'rightness' are also examples of selection on the basis of reward value. Within the OFC, the lateral regions are more likely to be involved when the action selected requires the suppression of previously rewarded responses.

Neural Activity Relating to Generation and Representation of Galvanic Skin Conductance Responses: A Functional Magnetic Resonance Imaging Study

Abstract: Central feedback of peripheral states of arousal influences motivational behavior and decision making. The sympathetic skin conductance response (SCR) is one index of autonomic arousal. The precise functional neuroanatomy underlying generation and representation of SCR during motivational behavior is undetermined, although it is impaired by discrete brain lesions to ventromedial prefrontal cortex, anterior cingulate, and parietal lobe. We used functional magnetic resonance imaging to study brain activity associated with spontaneous fluctuations in amplitude of SCR, and activity corresponding to generation and afferent representation of discrete SCR events. Regions that covaried with increased SCR included right orbitofrontal cortex, right anterior insula, left lingual gyrus, right fusiform gyrus, and left cerebellum. At a less stringent level of significance, predicted areas in bilateral medial prefrontal cortex and right inferior parietal lobule covaried with SCR. Generation of discrete SCR events was associated with significant activity in left medial prefrontal cortex, bilateral extrastriate visual cortices, and cerebellum. Activity in right medial prefrontal cortex related to afferent representation of SCR events. Activity in bilateral medial prefrontal lobe, right orbitofrontal cortex, and bilateral extrastriate visual cortices was common to both generation and afferent representation of discrete SCR events identified in a conjunction analysis. Our results suggest that areas implicated in emotion and attention are differentially involved in generation and representation of peripheral SCR responses. We propose that this functional arrangement enables integration of adaptive bodily responses with ongoing emotional and attentional states of the organism.

Cerebral correlates of autonomic cardiovascular arousal: a functional neuroimaging investigation in humans.

Abstract: 1 States of peripheral autonomic arousal accompany emotional behaviour, physical exercise and cognitive effort, and their central representation may influence decision making and the regulation of social and emotional behaviours However, the cerebral functional neuroanatomy representing and mediating peripheral autonomic responses in humans is poorly understood 2 Six healthy volunteer subjects underwent H215O positron emission tomography (PET) scanning while performing isometric exercise and mental arithmetic stressor tasks, and during corresponding control tasks Mean arterial blood pressure (MAP) and heart rate (HR) were monitored during scanning 3 Data were analysed using statistical parametric mapping (SPM99) Conjunction analyses were used to determine significant changes in regional cerebral blood flow (rCBF) during states of cardiovascular arousal common to both exercise and mental stressor tasks 4 Exercise and mental stressor tasks, relative to their control tasks, were associated with significantly (P < 0001) increased MAP and HR Significant common activations (increased rCBF) were observed in cerebellar vermis, brainstem and right anterior cingulate In both exercise and mental stress tasks, increased rCBF in cerebellar vermis, right anterior cingulate and right insula covaried with MAP; rCBF in pons, cerebellum and right insula covaried with HR Cardiovascular arousal in both categorical and covariance analyses was associated with decreased rCBF in prefrontal and medial temporal regions 5 Neural responses in discrete brain regions accompany peripheral cardiovascular arousal We provide evidence for the involvement of areas previously implicated in cognitive and emotional behaviours in the representation of peripheral autonomic states, consistent with a functional organization that produces integrated cardiovascular response patterns in the service of volitional and emotional behaviours

Dissociable Neural Responses in Human Reward Systems

Abstract: Reward is one of the most important influences shaping behavior. Single-unit recording and lesion studies in experimental animals have implicated a number of regions in response to reinforcing stimuli, in particular regions of the extended limbic system and the ventral striatum. In this experiment, functional neuroimaging was used to assess neural response within human reward systems under different psychological contexts. Nine healthy volunteers were scanned using functional magnetic resonance imaging during the performance of a gambling task with financial rewards and penalties. We demonstrated neural sensitivity of midbrain and ventral striatal regions to financial rewards and hippocampal sensitivity to financial penalties. Furthermore, we show that neural responses in globus pallidus, thalamus, and subgenual cingulate were specific to high reward levels occurring in the context of increasing reward. Responses to both reward level in the context of increasing reward and penalty level in the context of increasing penalty were seen in caudate, insula, and ventral prefrontal cortex. These results demonstrate dissociable neural responses to rewards and penalties that are dependent on the psychological context in which they are experienced.

Neuroimaging evidence for dissociable forms of repetition priming.

Abstract: Repetition priming has been characterized neurophysiologically as a decreased response following stimulus repetition. The present study used event-related functional magnetic resonance imaging to investigate whether this repetition-related response is sensitive to stimulus familiarity. A right fusiform region exhibited an attenuated response to the repetition of familiar stimuli, both faces and symbols, but exhibited an enhanced response to the repetition of unfamiliar stimuli. Moreover, both repetition effects were modulated by lag between successive presentations. Further experiments replicated the interactions between repetition, familiarity, and lag and demonstrated the persistence of these effects over multiple repetitions. Priming-related responses are therefore not unitary but depend on the presence or absence of preexisting stimulus representations.

Confidence in Recognition Memory for Words: Dissociating Right Prefrontal Roles in Episodic Retrieval

Abstract: We used event-related functional magnetic resonance imaging (efMRI) to investigate brain regions showing differential responses as a function of confidence in an episodic word recognition task. Twelve healthy volunteers indicated whether their old-new judgments were made with high or low confidence. Hemodynamic responses associated with each judgment were modeled with an "early" and a "late" response function. As predicted by the monitoring hypothesis generated from a previous recognition study [Henson, R. N. A., Rugg, M. D., Shallice, T., Josephs, O., & Dolan, R. J. (1999a). Recollection and familiarity in recognition memory: An event-related fMRI study. Journal of Neuroscience, 19, 3962-3972], a right dorsolateral prefrontal region showed a greater response to correct low- versus correct high-confidence judgements. Several regions, including the precuneus, posterior cingulate, and left lateral parietal cortex, showed greater responses to correct old than correct new judgements. The anterior left and right prefrontal regions also showed an old-new difference, but for these regions the difference emerged relatively later in time. These results further support the proposal that different subregions of the prefrontal cortex subserve different functions during episodic retrieval. These functions are discussed in relation to a monitoring process, which operates when familiarity levels are close to response criterion and is associated with nonconfident judgements, and a recollective process, which is associated with the confident recognition of old words.

A functional neuroanatomy of tics in Tourette syndrome.

Abstract: Background: Tics are involuntary, brief, stereotyped motor and vocal behaviors often associated with irresistible urges. They are a defining symptom of the classic neuropsychiatric disorder, Tourette syndrome (TS), and constitute an example of disordered human volition. The neural correlates of tics are not well understood and have not been imaged selectively. Methods: Event-related [ 15 O]H2O positron emission tomography techniques combined with time-synchronized audio and videotaping were used to determine the duration of, frequency of, and radiotracer input during tics in each of 72 scans from 6 patients with TS. This permitted a voxel-by-voxel correlational analysis within Statistical Parametric Mapping of patterns of neural activity associated with the tics. Results: Brain regions in which activity was significantly correlated with tic occurrence in the group included medial and lateral premotor cortices, anterior cingulate cortex, dorsolateral-rostral prefrontal cortex, inferior parietal cortex, putamen, and caudate, as well as primary motor cortex, the Broca’s area, superior temporal gyrus, insula, and claustrum. In an individual patient with prominent coprolalia, such vocal tics were associated with activity in prerolandic and postrolandic language regions, insula, caudate, thalamus, and cerebellum, while activity in sensorimotor cortex was noted with motor tics. Conclusions: Aberrant activity in the interrelated sensorimotor, language, executive, and paralimbic circuits identified in this study may account for the initiation and execution of diverse motor and vocal behaviors that characterize tics in TS, as well as for the urges that often accompany them. Arch Gen Psychiatry. 2000;57:741-748

Selective attention to emotional stimuli in a verbal go/no-go task: an fMRI study.

Abstract: Tasks requiring subjects to attend emotional attributes of words have been used to study mood-congruent information processing biases in anxiety and affective disorders. In this study we adapted an emotional go/no-go task, for use with fMRI to assess the neural substrates of focusing on emotional attributes of words in normal subjects. The key findings were that responding to targets defined on the basis of meaning of words compared to targets defined on the basis of perceptual features was associated with response in inferior frontal gyrus and dorsal anterior cingulate. Further, selecting emotional targets, whether happy or sad, was associated with enhanced response in the subgenual cingulate, while happy targets elicited enhanced neural response in ventral anterior cingulate. These findings reaffirm the importance of medial prefrontal regions in normal emotional processing.

Anatomical Segregation of Component Processes in an Inductive Inference Task

Abstract: Inductive inference underlies much of human cognition. The essential component of induction is hypothesis selection based on some criterion of relevance. The purpose of this study was to determine the neural substrate of inductive inference, particularly hypothesis selection, using fMRI. Ten volunteers were shown stimuli consisting of novel animals under two task conditions, and asked to judge whether all the animals in the set were the same type of animal. In one condition, subjects were given a rule that specified the criteria for "same type of animal". In the other condition, subjects had to infer the rule without instruction. The two conditions were further factored into easy and difficult components. Rule inference was specifically associated with bilateral hippocampal activation while the task by difficulty interaction was associated with activation in right lateral orbital prefrontal cortex. We interpret the former in terms of semantic encoding of novel stimuli, and the latter in terms of hypothesis selection. Thus, we show an anatomical dissociation between task implementation and task difficulty that may correspond to a critical psychological distinction in the processes necessary for inductive inference.

Neural consequences of competing stimuli in both visual hemifields: a physiological basis for visual extinction.

Abstract: We used positron emission tomography in healthy volunteers to test hemispheric rivalry theories for normal and pathological spatial attention, which provide an influential account of contralesional extinction on bilateral stimulation after unilateral brain injury. Subjects reported visual characters presented either unilaterally or bilaterally. An extinction-like pattern was found behaviorally, with characters in one hemifield reported less accurately when competing characters appeared in the other hemifield. Differences in neural activity for unilateral minus bilateral conditions revealed greater activation of striate and extrastriate areas for stimuli presented without competing stimuli in the other hemifield. Thus, simultaneous bilateral stimulation led to a significant reduction in response by spatiotopic visual cortex contralateral to a particular stimulus. These data provide physiological support for interhemispheric rivalry in the intact human brain, and demonstrate that such competition impacts at early levels of perceptual processing.

How does the brain sustain a visual percept

Abstract: Perception involves the processing of sensory stimuli and their translation into conscious experience. A novel percept can, once synthesized, be maintained or discarded from awareness. We used event-related functional magnetic resonance imaging to separate the neural responses associated with the maintenance of a percept, produced by single-image, random-dot stereograms, from the response evoked at the onset of the percept. The latter was associated with distributed bilateral activation in the posterior thalamus and regions in the occipito-temporal, parietal and frontal cortices. In contrast, sustained perception was associated with activation of the pre-frontal cortex and hippocampus. This observation suggests that sustaining a visual percept involves neuroanatomical systems which are implicated in memory function and which are distinct from those engaged during perceptual synthesis.

Neuronal Activity in Early Visual Areas during Global and Local Processing: A Comment on Heinze, Hinrichs, Scholz, Burchert, and Mangun

Abstract: In a paper published in the 10:4 issue of JOCN, Heinze et al. 1998) studied a directed attention task using hierarchically organized letter Navon stimuli. On the basis of negative PET and ERP findings, they argue that``early sensory inputs are not modulated to gate global vs. local visual information differentially into the two hemispheres .'' Rather, based on positive ERP findings (an N2 effect) in a divided-attention task, they argue that``later stages of cortical processing may be asymmetrically organized in the left and right hemispheres and operate in parallel to process global and local aspects of complex stimuli.'' The authors conclude that their re-sults``support models proposing that spatial frequency analysis is only asymmetric at higher stages of perceptual processing and not at the earliest stages of visual cortical analysis.'' In three previous functional-neuroimaging studies of directed-visual attention to complex-hierarchical stimuli of various types (letters made of letters, objects made of objects, and rectangles made of rectangles), we have repeatedly demonstrated hemispheric differences between global and local processing both in early visual processing areas (V2/V3). We also find that higher stages of perceptual processing that activate temporo-parietal cortex are implicated in a divided-attention task using such stimuli (Fink et al., 1996; Fink et al., 1997a). In addition, such hemispheric-differential activations at the early stages of visual processing are influenced by sti-Our PET findings are thus consistent with neuropsy-chological studies demonstrating a critical role of the temporo-parietal cortex in global/local processing (Ro-1988), functional-imaging data using fMRI (Martinez et al., 1997) showing hemispheric differences between global and local processing, and other functional-imaging data (using both PET and fMRI) on the attentional gating of early visual processing areas (Corbetta, Miezin, Dobmeyer, Shulman, & Petersen, 1990). Furthermore, electrophysiological data obtained in monkeys directly demonstrate enhanced neural activity in early visual cortex resulting from changes in attentional set The N2 effect observed by Heinze et al. (1998) is consistent with the widely accepted view that the local aspects of hierarchical letter Navon figures are preferentially processed in the left hemisphere while the global aspects of such figures are preferentially processed in the right hemisphere. Leaving aside the problem of the exact localization of ERP sources, it is important to consider whether their negative PET findings (Heinze et al., 1998) can be taken as evidence against our findings of early visual processing differences in similar experiments (Fink et al., 1997a; Fink et al., 1999). The failure of …

20 – The Neurobiology of Anxiety and Anxiety-Related Disorders: A Functional Neuroimaging Perspective

Abstract: This chapter focuses on the anxiety. Anxiety can be conceptualized as a negative cognitive-affective somatic state. The prominent feature being "a sense of uncontrollability focused on possible future threat, danger, or other upcoming, potentially negative events.” Anxiety is a normal psychological reaction to impending threat or uncertainty. It also represents both the commonest psychiatric symptom and in the form of general anxiety disorder (GAD) is one of the most prevalent syndromes. In psychopathological contexts, anxiety can occur either in isolation or as a component symptom of more widespread psychological morbidity. When anxiety is the predominant symptom, it is referred to as generalized anxiety disorder, a condition that reflects situations where patients experience pervasive anxiety in the absence of panic, agoraphobia, or other phobic symptoms. Phobic responses to stimuli such as spiders and snakes not only are common but are seen in environments where snakes and hazardous spiders are relatively rare or even absent. Many forms of anxiety arise without clear environmental precipitants. There are well-defined situations where anxiety arises directly out of individual experience. Anxiety is re-experienced in the setting of evoked trauma-related memories or actual exposure to contexts that are similar to or identical with that of the precipitating traumatic event.