Biomedical subjects

Raymond J Dolan

Publications and source records attributed to Raymond J Dolan.

82 records · Page 5Linked to original sources

PubMed2002

Neural responses during anticipation of a primary taste reward.

The aim of this study was to determine the brain regions involved in anticipation of a primary taste reward and to compare these regions to those responding to the receipt of a taste reward. Using fMRI, we scanned human subjects who were presented with visual cues that signaled subsequent reinforcement with a pleasant sweet taste (1 M glucose), a moderately unpleasant salt taste (0.2 M saline), or a neutral taste. Expectation of a pleasant taste produced activation in dopaminergic midbrain, posterior dorsal amygdala, striatum, and orbitofrontal cortex (OFC). Apart from OFC, these regions were not activated by reward receipt. The findings indicate that when rewards are predictable, brain regions recruited during expectation are, in part, dissociable from areas responding to reward receipt.

Adolescent↗

PubMed2002

Fear conditioning in humans: the influence of awareness and autonomic arousal on functional neuroanatomy.

The degree to which perceptual awareness of threat stimuli and bodily states of arousal modulates neural activity associated with fear conditioning is unknown. We used functional magnetic neuroimaging (fMRI) to study healthy subjects and patients with peripheral autonomic denervation to examine how the expression of conditioning-related activity is modulated by stimulus awareness and autonomic arousal. In controls, enhanced amygdala activity was evident during conditioning to both "seen" (unmasked) and "unseen" (backward masked) stimuli, whereas insula activity was modulated by perceptual awareness of a threat stimulus. Absent peripheral autonomic arousal, in patients with autonomic denervation, was associated with decreased conditioning-related activity in insula and amygdala. The findings indicate that the expression of conditioning-related neural activity is modulated by both awareness and representations of bodily states of autonomic arousal.

Aged↗

PubMed2002

The neural basis of mood-congruent processing biases in depression.

BACKGROUND: Mood-congruent processing biases are among the most robust research findings in neuropsychological studies of depression. Depressed patients show preferential processing of negatively toned stimuli across a range of cognitive tasks. The present study aimed to determine whether these behavioral abnormalities are associated with specific neural substrates. METHODS: Ten depressed patients and 11 healthy control subjects underwent scanning during performance of an emotional go/no-go task using functional magnetic resonance imaging. The task allowed comparison among neural response to happy, sad, and neutral words, in the context of these words as targets (ie, stimuli to which subjects were required to make a motor response) or distractors (ie, stimuli to which the motor response was withheld). RESULTS: Depressed patients showed attenuated neural responses to emotional relative to neutral targets in ventral cingulate and posterior orbitofrontal cortices. However, patients showed elevated responses specific to sad targets in rostral anterior cingulate extending to anterior medial prefrontal cortex. Unlike controls, patients showed differential neural response to emotional, particularly sad, distractors in the lateral orbitofrontal cortex. CONCLUSIONS: These findings suggest a distinct neural substrate for mood-congruent processing biases in performance. The medial and orbital prefrontal regions may play a key role in mediating the interaction between mood and cognition in affective disorder.

Adult↗

PubMed2002

The effects of interdistracter similarity on search processes in superior parietal cortex.

The superior parietal lobe has been associated with the spatial integration of visual features, an important step in the detection of particular form conjunctions. However, behavioral research has indicated that when target items can be segmented from neighboring distracters via similarity grouping, detection may not rely on spatial integration. The question therefore arises as to whether the superior parietal cortex is an integral component of conjunction search or only important in the absence of certain grouping relations. Here, we acquired measures of reaction time and event-related fMRI, while subjects searched for conjunction targets in displays containing either homogeneous or heterogeneous distracters. We confirm that under conditions of low distracter similarity, search involves parietal-motor areas associated with spatial selection. However, we also demonstrate that under conditions of high distracter similarity, search is instead associated with activation of right temporal-parietal cortex. These results suggest that the superior parietal cortex is not a necessary component of visual conjunction search and highlight a new role for the right temporal-parietal cortex in perceptual grouping.

Adult↗

PubMed2002

Volitional control of autonomic arousal: a functional magnetic resonance study.

Electrodermal activity reflects autonomic sympathetic innervation of dermal sweat glands providing an index of emotion-related bodily states of arousal. Relaxation techniques, which are facilitated by external (bio)feedback of electrodermal activity, can be used by trained subjects to actively control bodily and emotional arousal. Biofeedback relaxation provides an experimental model to explore neural mechanisms contributing to emotional representations and intentional autonomic control. We used functional magnetic resonance imaging (fMRI) to explore neural mechanisms contributing to integration of volitional intent, self-representation, and autonomic states of arousal, embodied within performance of a biofeedback relaxation exercise. Data were obtained from 17 subjects to assess brain activity during relaxation in which a visual index of electrodermal arousal was modulated by accuracy (addition of random "noise") or sensitivity (by scalar adjustments of feedback). A central matrix of cortical, subcortical and brainstem autonomic centres was activated during biofeedback relaxation, as well as regions that mediate visual and somatesthetic representations and executive control. Anterior cingulate, amygdala, and insula activity was modulated by task manipulations that increased demand on processing interoceptive representations, while variation in anterior insula activity reflected an interaction between accuracy and sensitivity of feedback. These findings identify neural substrates that support integration of perceptual processing, interoception, and intentional modulation of bodily states of arousal.

Adult↗

PubMed2002

Modulation of spatial attention by fear-conditioned stimuli: an event-related fMRI study.

Stimuli that signal threat can capture subjects' attention, leading to more efficient detection of, and faster responses to, events occurring in that part of the environment. In the present study we explored the behavioural and anatomical correlates of the modulation of spatial attention by emotion using a fear conditioning paradigm, combined with a covert spatial orienting task. Reaction times for the detection of a peripheral target, which was preceded by brief (50ms) presentations of the visual conditioned stimulus (CS+) in either the same or opposite visual field, showed an interaction between stimulus emotionality and attention shifts. We used event-related functional magnetic resonance imaging (fMRI) to characterise the associated neural responses. Consistent with previous studies, conditioning-induced enhanced responses were observed in the amygdala and extrastriate visual cortex. The modulation of spatial attention by a conditioned stimulus was associated with enhanced activity in regions of frontal and parietal cortices previously implicated in spatial attention, as well as in the lateral orbitofrontal cortex (lOFC).

Amygdala↗

PubMed2002

Scopolamine but not lorazepam modulates face repetition priming: a psychopharmacological fMRI study.

Repetition priming is a basic form of learning associated with decreased neuronal responses following stimulus repetition. In this experiment, we address cholinergic and GABAergic modulation of repetition priming in a face recognition paradigm. In experiment 1, we used event-related functional magnetic resonance imaging (fMRI) in combination with pharmacological challenge where participants were given placebo, lorazepam (2mg po), or scopolamine (0.4 mg IV) prior to study. Behavioral data showed intact priming for famous faces in the placebo and lorazepam group but impaired priming following scopolamine. In within-group analyses, a right fusiform region showed a fame by repetition interaction characterized by a response decrease to repetition of famous faces and a response enhancement to repetition of unfamous faces in the placebo group. In subjects treated with lorazepam, a main effect of repetition, driven by response decreases to repetition of famous faces, was seen in this right fusiform region. No significant repetition effects were found after scopolamine. In experiment 2, we further investigated behaviorally the cholinergic impairment of repetition priming. Participants were given either placebo or scopolamine (0.4 mg IV) after study. Behavioral data showed intact priming for famous faces in the placebo and scopolamine group. The results suggest that scopolamine but not lorazepam impair repetition priming for famous faces in a face recognition paradigm. These cholinergic impairments are likely to reflect interference with acquisition processes during study that may co-occur with a modulation of right fusiform decreases to repetition of famous faces.

Acetylcholine↗

PubMed2002

Brain activity underlying encoding and retrieval of source memory.

Neural activity elicited during the encoding and retrieval of source information was investigated with event-related functional magnetic resonance imaging (efMRI). During encoding, 17 subjects performed a natural/artificial judgement on pictures of common objects which were presented randomly in one of the four quadrants of the display. At retrieval, old pictures were mixed with new ones and subjects judged whether each picture was new or old and, if old, indicated in which quadrant it was presented at encoding. During encoding, study items that were later recognized and assigned a correct source judgement elicited greater activity than recognized items given incorrect judgements in a variety of regions, including right lateral occipital and left prefrontal cortex. At retrieval, regions showing greater activity for recognized items given correct versus incorrect source judgements included the right hippocampal formation and the left prefrontal cortex. These findings indicate a role for these regions in the encoding and retrieval of episodic information beyond that required for simple item recognition.

Adult↗

PubMed2002

Cortical and subcortical gray matter abnormalities in schizophrenia determined through structural magnetic resonance imaging with optimized volumetric voxel-based morphometry.

OBJECTIVE: Structural neuroimaging studies have suggested an association between schizophrenia and abnormalities in brain morphology such as ventricular enlargement and differences in gray matter distribution. Less consistently reported are findings of regional abnormalities such as selective differences in thalamic volume. The authors applied an unbiased technique to test for differences in cerebral morphometry between patients with schizophrenia and matched comparison subjects. METHOD: T(1)-weighted images from 20 schizophrenic patients and matched comparison subjects were processed by using optimized automated voxel-based morphometry within multiple linear regression analyses. RESULTS: Global differences in gray matter volume were seen between the schizophrenic and comparison subjects, with selective regional gray matter differences noted in the mediodorsal thalamus and across cortical regions, including the ventral and medial prefrontal cortices. Within the schizophrenic subjects, a relationship was observed between gray matter volume loss in the medial prefrontal cortex and a positive family history of schizophrenia. There was no significant difference between patients and comparison subjects in rates of proportional gray matter reduction with age. CONCLUSIONS: These observations confirm an association between thalamocortical morphometric abnormalities and schizophrenia, consistent with theoretical models of primary pathoetiological dysfunction in filtering, integration, and information transfer processes in patients with schizophrenia.

Adult↗

PubMedDate not supplied

Modulation of retrieval processing reflects accuracy of emotional source memory.

There is considerable evidence that encoding and consolidation of memory are modulated by emotion, but the retrieval of emotional memories is not well characterized. Here we manipulated the emotional context with which affectively neutral stimuli were associated during encoding, allowing us to examine neural activity associated with retrieval of emotional memories without confounding the emotional attributes of cue items and the retrieved context. Using a source memory procedure we were also able to compare how retrieval processing was modulated when the emotional encoding context was recollected or not. An interaction between emotional encoding context and accuracy of source memory revealed that successful retrieval of emotional context was associated with activity in left amygdala, and a left frontotemporal network including anterior insula, prefrontal cortex and cingulate. In contrast, when contextual retrieval was unsuccessful, items encoded in emotional contexts elicited enhanced activity in right amygdala and a right-lateralized network that included extrastriate visual areas. These findings indicate distinct effects of emotion on successful and unsuccessful retrieval of source information, including lateralization of amygdala responses.

Adolescent↗