PubMed Health⌕ Search

Biomedical subjects

Rebecca Elliott

Publications and source records attributed to Rebecca Elliott.

12 recordsLinked to original sources
PubMed2006

Serotonergic modulation of neuronal responses to behavioural inhibition and reinforcing stimuli: an fMRI study in healthy volunteers.

Serotonin (5-HT) has been implicated in the aetiology of a number of psychiatric conditions, including depression, anxiety and antisocial personality disorder. The development of these disorders may arise from alterations in underlying motivational and cognitive processes such as emotional recognition, reinforcement processing and central inhibitory control. This study aimed to localize where in the brain 5-HT modulates neuropsychological processes relevant to putative 5-HT disorders, using functional magnetic resonance imaging. We examined the effect of the antidepressant mirtazapine on brain activations associated with behavioural inhibition and reinforcement processing in healthy subjects. Forty-five men were randomly allocated to receiving mirtazapine or placebo in a double-blind fashion. A Go/No-Go, Reward/No-Reward and Loss/No-loss task were performed during functional magnetic resonance imaging using a 1.5 Tesla Philips Gyroscan scanner. Blood oxygenation level dependent (BOLD) responses were analysed using SPM2. Task activations were largely consistent with previous findings. Mirtazapine modulated brain activations in the Go/No-Go and Reward/No-Reward task. During behavioural inhibition, enhanced activations were observed in the right orbitofrontal cortex (BA47). Increased activations in bilateral parietal cortex were found during the Reward task while no significant interaction was observed in the Loss task. Our results support the suggestion of an important role of serotonin in modulating basic processes involved in psychiatric disorders. Combining drug challenge with fMRI (pharmacoMRI; pMRI) is a promising tool for investigating these processes in healthy as well as patient groups.

Adolescent↗
PubMed2005

Neuronal correlates of theory of mind and empathy: a functional magnetic resonance imaging study in a nonverbal task.

Theory of Mind (ToM), the ability to attribute mental states to others, and empathy, the ability to infer emotional experiences, are important processes in social cognition. Brain imaging studies in healthy subjects have described a brain system involving medial prefrontal cortex, superior temporal sulcus and temporal pole in ToM processing. Studies investigating networks associated with empathic responding also suggest involvement of temporal and frontal lobe regions. In this fMRI study, we used a cartoon task derived from Sarfati et al. (1997) [Sarfati, Y., Hardy-Bayle, M.C., Besche, C., Widlocher, D. 1997. Attribution of intentions to others in people with schizophrenia: a non-verbal exploration with comic strips. Schizophrenia Research 25, 199-209.]with both ToM and empathy stimuli in order to allow comparison of brain activations in these two processes. Results of 13 right-handed, healthy, male volunteers were included. Functional images were acquired using a 1.5 T Phillips Gyroscan. Our results confirmed that ToM and empathy stimuli are associated with overlapping but distinct neuronal networks. Common areas of activation included the medial prefrontal cortex, temporoparietal junction and temporal poles. Compared to the empathy condition, ToM stimuli revealed increased activations in lateral orbitofrontal cortex, middle frontal gyrus, cuneus and superior temporal gyrus. Empathy, on the other hand, was associated with enhanced activations of paracingulate, anterior and posterior cingulate and amygdala. We therefore suggest that ToM and empathy both rely on networks associated with making inferences about mental states of others. However, empathic responding requires the additional recruitment of networks involved in emotional processing. These results have implications for our understanding of disorders characterized by impairments of social cognition, such as autism and psychopathy.

Adult↗
PubMed2005

The effect of citalopram pretreatment on neuronal responses to neuropsychological tasks in normal volunteers: an FMRI study.

Changes in serotonin neurotransmission have also been implicated in the etiology and treatment of impulse control disorders, depression, and anxiety. We have investigated the effect of enhancing serotonin function on fundamental brain processes that we have proposed are abnormal in these disorders. In all, 12 male volunteers received citalopram (7.5 mg intravenously) and placebo pretreatment in a single-blind crossover design before undertaking Go/No-go, Loss/No-loss, and covert (aversive) face emotion recognition tasks during functional magnetic resonance imaging (fMRI). Blood oxygenation level dependent responses were analyzed using Statistical Parametric Mapping (SPM2). The tasks activated prefrontal and subcortical regions generally consistent with literature with lateral orbitofrontal cortex (BA47) common to the three tasks. Citalopram pretreatment enhanced the right BA47 responses to the No-go condition, but attenuated this response to aversive faces. Attenuations were seen following citalopram in the medial orbitofrontal (BA11) responses to the No-go and No-loss (ie relative reward compared with Loss) conditions. The right amygdala response to aversive faces was attenuated by citalopram. These results support the involvement of serotonin in modulating basic processes involved in psychiatric disorders but argue for a process-specific, rather than general effect. The technique of combining drug challenge with fMRI (pharmacoMRI) has promise for investigating human psychiatric disorders.

Adult↗
PubMed2004

Abnormal ventral frontal response during performance of an affective go/no go task in patients with mania.

BACKGROUND: Patients with mania show a behavioral bias toward positive information in an emotional go/no go task. This is the converse of the bias toward negative information seen in unipolar depression that we have recently related to the abnormal function of ventral and medial prefrontal cortices (PFCs). The aim of this study was to investigate the neuronal basis of the bias toward positive information in manic patients. METHODS: During performance of an emotional go/no go task using functional magnetic resonance imaging, 8 manic patients and 11 healthy controls were scanned. The task allowed comparison between neural response to happy, sad, and neutral words in the context of these words being either targets or distracters. RESULTS: Manic patients showed attenuated orbitofrontal response when all the semantic conditions were compared with a control condition; however, they showed an enhanced response of the left ventrolateral PFC to emotional relative to neutral targets, as well as enhanced ventral and medial prefrontal response to emotional, particularly happy, distracters. CONCLUSIONS: These results suggest a critical role for ventral and medial dysfunction in the pathology of mania, which might underpin aspects of cognitive and clinical symptomatology.

Adolescent↗
PubMed2004

Neurobiological substrates of antisocial and borderline personality disorder: preliminary results of a functional fMRI study.

BACKGROUND: Neuropsychological and imaging studies of patients with antisocial (ASPD) and borderline personality disorder (BPD) are suggestive of frontal lobe dysfunction in these individuals. In normal subjects functional brain imaging has been used to investigate the neuroanatomy of impulse control. There are no such imaging studies in personality-disordered populations. AIM: This study aimed to investigate which neuronal networks are involved in response inhibition in Cluster B personality disorders and whether these are different from healthy subjects. HYPOTHESIS: We hypothesized that the personality-disordered sample would have attenuated orbitofrontal cortex responses during performance of a Go/NoGo task compared with healthy controls. METHOD: Eight inpatients with a DSM-IV diagnosis of borderline or antisocial personality disorder and eight healthy controls were scanned using fMRI while performing a Go/NoGo task. Impulsivity was assessed using the Barratt Impulsivity Scale (BIS) and the Impulsiveness-Venturesomeness-Empathy (IVE) inventory. RESULTS: In the control group the main focus of activation during response inhibition was in the prefrontal cortex, specifically the right dorsolateral and the left orbitofrontal cortex. Active regions in the patient group showed a more bilateral and extended pattern of activation across the medial, superior and inferior frontal gyri extending to the anterior cingulate. CONCLUSIONS: fMRI is a useful tool to detect brain activation during response inhibition. ASPD and BPD patients activate different neural networks to successfully inhibit pre-potent responses.

Adult↗
PubMed2004

Instrumental responding for rewards is associated with enhanced neuronal response in subcortical reward systems.

The response of human reward systems to different reinforcers, including food, drugs and money, has been investigated in a number of recent functional neuroimaging studies. They have varied, however, in terms of whether or not a behavioural response was required to obtain rewards. The aim of the present study was to determine whether neuronal responses to financial reward are significantly modulated by the requirement to make a behavioural response. Twelve subjects were scanned using functional magnetic resonance imaging (fMRI) while performing a simple target detection task. Certain targets acted as cues predicting financial reinforcement; some additionally required that a movement be executed, while others did not. There were also targets that required a movement but were not predictive of reward. We observed, as expected, responses within motor and reward systems associated with main effects of movement and reward, respectively. Critically, the reward responses were significantly modulated by the requirement to make an intervening behavioural response. Blood oxygenation level-dependent (BOLD) responses in the amygdala and striatum were significantly enhanced when a movement was required, while reward-related response in the orbitofrontal cortex was independent of movement. These results suggest important dissociations within human reward systems, reflecting different properties of rewards. The striatum and amygdala may mediate the function of rewards in eliciting goal-directed behaviour, while the orbitofrontal cortex mediates incentive value.

Adult↗
PubMed2004

Neural response to emotional prosody in schizophrenia and in bipolar affective disorder.

BACKGROUND: Evidence suggests a reversal of the normal left-lateralised response to speech in schizophrenia. AIMS: To test the brain's response to emotional prosody in schizophrenia and bipolar disorder. METHOD: BOLD contrast functional magnetic resonance imaging of subjects while they passively listened or attended to sentences that differed in emotional prosody. RESULTS: Patients with schizophrenia exhibited normal right-lateralisation of the passive response to 'pure' emotional prosody and relative left-lateralisation of the response to unfiltered emotional prosody. When attending to emotional prosody, patients with schizophrenia activated the left insula more than healthy controls. When listening passively, patients with bipolar disorder demonstrated less activation of the bilateral superior temporal gyri in response to pure emotional prosody, and greater activation of the left superior temporal gyrus in response to unfiltered emotional prosody. In both passive experiments, the patient groups activated different lateral temporal lobe regions. CONCLUSIONS: Patients with schizophrenia and bipolar disorder may display some left-lateralisation of the normal right-lateralised temporal lobe response to emotional prosody.

Adult↗
PubMed2003

Differential response patterns in the striatum and orbitofrontal cortex to financial reward in humans: a parametric functional magnetic resonance imaging study.

Responses to monetary reward in humans have been assessed in a number of recent functional imaging studies, and it is clear that the neuronal substrates of financial reinforcement overlap extensively with regions responding to primary reinforcers, such as food. Money has the practical advantage of being an objectively quantifiable reinforcer. In this study, we exploit this advantage using a parametric functional magnetic resonance imaging design to look at the patterns of responding to systematically varying reward values. Twelve healthy volunteers were scanned during performance of a rewarded target detection task, in which the reward value varied between task blocks. We observed three distinct patterns of responding in different regions. Amygdala, striatum, and dopaminergic midbrain responded to the presence of rewards, regardless of value. In contrast, premotor cortex showed a linear increase in response with increasing reward value. Finally, medial and lateral foci of orbitofrontal cortex responded nonlinearly, such that response was enhanced for the lowest and highest reward values relative to the midrange. These results suggest functional distinction in response patterns within a distributed reward system.

Adult↗
PubMed2003

The neural response to emotional prosody, as revealed by functional magnetic resonance imaging.

Prosody is an important feature of language, comprising intonation, loudness, and tempo. Emotional prosodic processing forms an integral part of our social interactions. The main aim of this study was to use bold contrast fMRI to clarify the normal functional neuroanatomy of emotional prosody, in passive and active contexts. Subjects performed six separate scanning studies, within which two different conditions were contrasted: (1) "pure" emotional prosody versus rest; (2) congruent emotional prosody versus 'neutral' sentences; (3) congruent emotional prosody versus rest; (4) incongruent emotional prosody versus rest; (5) congruent versus incongruent emotional prosody; and (6) an active experiment in which subjects were instructed to either attend to the emotion conveyed by semantic content or that conveyed by tone of voice. Data resulting from these contrasts were analysed using SPM99. Passive listening to emotional prosody consistently activated the lateral temporal lobe (superior and/or middle temporal gyri). This temporal lobe response was relatively right-lateralised with or without semantic information. Both the separate and direct comparisons of congruent and incongruent emotional prosody revealed that subjects used fewer brain regions to process incongruent emotional prosody than congruent. The neural response to attention to semantics, was left lateralised, and recruited an extensive network not activated by attention to emotional prosody. Attention to emotional prosody modulated the response to speech, and induced right-lateralised activity, including the middle temporal gyrus. In confirming the results of lesion and neuropsychological studies, the current study emphasises the importance of the right hemisphere in the processing of emotional prosody, specifically the lateral temporal lobes.

Adolescent↗
PubMed2003

Executive functions and their disorders.

The term executive function defines complex cognitive processing requiring the co-ordination of several subprocesses to achieve a particular goal. Neuropsychological evidence suggests that executive processing is intimately connected with the intact function of the frontal cortices. Executive dysfunction has been associated with a range of disorders, and is generally attributed to structural or functional frontal pathology. Neuroimaging, with PET and fMRI, has confirmed the relationship; however, attempts to link specific aspects of executive functioning to discrete prefrontal foci have been inconclusive. Instead, the emerging view suggests that executive function is mediated by dynamic and flexible networks, that can be characterised using functional integration and effective connectivity analyses. This view is compatible with the clinical presentation of executive dysfunction associated with a range of pathologies, and also with evidence that recovery of executive function can occur after traumatic brain injury, perhaps due to functional reorganisation within executive networks.

Brain Injuries↗
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↗