Biomedical subjects
Jennifer Barrett
Publications and source records attributed to Jennifer Barrett.
Mechanisms of action underlying the effect of repetitive transcranial magnetic stimulation on mood: behavioral and brain imaging studies.
In a set of experiments, we applied 10-Hz repetitive transcranial magnetic stimulation (rTMS) over the left mid-dorsolateral frontal cortex (MDLFC) to investigate rTMS-induced changes in affective state and neural activity in healthy volunteers. In Experiment 1, we combined 10-Hz rTMS with a speech task to examine rTMS-induced changes in paralinguistic aspects of speech production, an affect-relevant behavior strongly linked to the ACC. In Experiment 2, we combined 10-Hz rTMS with positron emission tomography (PET) and used partial least squares (PLS) to identify a pattern of brain regions whose connectivity with the site of stimulation varied as a function of rTMS. The results of Experiment 1 revealed that following stimulation of the left MDLFC, subjects reported having less positive affect and vitality and displayed more monotonous speech. In Experiment 2, results revealed that 10-Hz rTMS influenced the covariation between blood flow at the site of stimulation (ie the left MDLFC) and blood flow in a number of affect-relevant brain regions including the perigenual anterior cingulate gyrus, insula, thalamus, parahippocampal gyrus, and caudate nucleus. Taken together, our results suggest that changes in affect and affect-relevant behaviour following 10-Hz rTMS applied over the left MDLFC may be related to changes in neural activity in brain regions widely implicated in affective states, including a frontocingulate circuit.
The role of the anterior cingulate cortex in pitch variation during sad affect.
We examined neural activity, in the frontal lobes, associated with speech production during affective states. Using functional magnetic resonance imaging (fMRI), the blood oxygen level-dependent (BOLD) response to the overt reading of emotionally neutral sentences was measured before and after a happy or sad mood induction. There was no explicit demand to produce affect-congruent speech and a cover story was used to de-emphasize the significance of the speech task in light of our experimental aims. Each fMRI measurement was acquired 6 s after the onset of sentence presentation so that speech could be recorded while the scanner noise was minimal; speech parameters (e.g. pitch variation) were extracted from the sentences and regressed against fMRI data. In the sad group we found the predicted changes in affect and pitch variation. Further, the fMRI data confirmed our hypothesis in that the 'reading effect' (i.e. the BOLD response to reading minus the BOLD response to baseline stimuli) in the supracallosal anterior cingulate cortex covaried negatively with both pitch variation and affect. Our results suggest that the anterior cingulate cortex modulates paralinguistic features of speech during affective states, thus placing this neural structure at the interface between action and emotions.
Reproductive and sexual health among young adults in Uzbekistan.
Since 1991, contraceptive use has risen significantly in Uzbekistan while reliance on abortion has declined; yet reproductive health improvements have not translated into better conditions for sexual health. The prevalence of sexually transmitted diseases increased significantly in the 1990s, and UNAIDS currently identifies the Central Asian region as a high HIV-growth zone. Structural, institutional, and attitudinal factors have contributed to the disconnection between reproductive and sexual health in Uzbekistan, even though family planning programs have been well established during the HIV pandemic. Integrating state statistics, Demographic and Health Survey data, and focus-group-discussion results, we highlight the ways in which a heavily centralized program focusing on reproductive health did little to better sexual health, especially among young adults. The example of Uzbekistan reveals pathways by which reproductive health efforts may continue to be compartmentalized, decreasing their potential contributions to sexual health, especially among young adults.
Transcranial magnetic stimulation (TMS) of the human frontal cortex: implications for repetitive TMS treatment of depression.
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive tool used to manipulate activity in specific neural circuits of the human brain. Clinical studies suggest that, in some patients with major depression, rTMS has the potential to alleviate symptoms that may be related to functional abnormalities in a frontocingulate circuit. This paper reviews the rationale for the use of rTMS in this context. The following topics are discussed: symptoms and cognition in major depression, with special emphasis on the initiation of speech; neuroimaging studies of depression; rTMS as treatment for depression; structure and function of the mid-dorsolateral frontal and anterior cingulate cortices; and combined TMS/positron emission tomography studies of frontocortical connectivity.
Affect-induced changes in speech production.
To determine how sad affect (or brief sad mood) interacts with paralinguistic aspects of speech, we investigated the effect of a happy or sad mood induction on speech production in 49 healthy volunteers. Several speech parameters measuring speech rate, loudness and pitch were examined before and after a standardized mood-induction procedure that involved viewing facial expressions. Speech samples were collected during the self-initiated reading of emotionally "neutral" sentences; there was no explicit demand to produce mood-congruent speech. Results indicated that, after the mood induction, the speech of participants in the sad group was slower, quieter and more monotonous than the speech of participants in the happy group. This speech paradigm provides a model for studying how changes in mood states interact with the motor control of speech.
Association of DRD4 in children with ADHD and comorbid conduct problems.
Recent family and twin study findings suggest that ADHD when comorbid with conduct problems may represent a particularly familial and heritable form of ADHD. Although several independent groups have shown association between the DRD4 7 repeat allele and ADHD, others have failed to replicate this finding. Previous TDT analyses of UK and Eire samples had also been negative. We set out to further examine the role of DRD4 but selecting a subgroup of children with ADHD and comorbid conduct problems. Families were recruited from Manchester, Ireland, Birmingham and London clinics. From these, 67 children who fulfilled diagnostic criteria for ADHD and who displayed conduct disorder symptoms were selected. TDT analysis, which had previously yielded negative results for the total sample, showed evidence of association between DRD4 and "ADHD with conduct problems" (7 repeat allele-24 transmissions, 13 non-transmissions; one-tailed P=0.05). These results provide further support for the role of DRD4 in ADHD. Furthermore, these results when considered together with family and twin study findings, suggest that those children with ADHD and comorbid conduct problems may be particularly informative for molecular genetic studies of ADHD. Further work is needed to examine these phenotype issues.
The effect of hypocretin replacement therapy in a 3-year-old Weimaraner with narcolepsy.
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