Biomedical subjects

Marnie Shaw

Publications and source records attributed to Marnie Shaw.

5 recordsLinked to original sources

PubMed2006

Dysfunction of dorsolateral prefrontal cortex in antipsychotic-naïve schizophreniform psychosis.

Reports of abnormal activation of the dorsolateral prefrontal cortex (dlPFC) are common in functional neuroimaging studies of schizophrenia, although very few have examined brain activity in patients close to the onset of illness. In this H(2)(15)O PET study, eight young male patients with first-episode schizophreniform psychosis and age-matched control subjects performed a version of the Stroop task that we have previously shown to engage the middle-frontal gyrus. At the time of testing, patients were antipsychotic-naïve and were scanned within 1 week of initial contact with our clinical program. All patients received a later diagnosis of schizophrenia 6 months after participating in the study. Whole-brain (within-group) and region-of-interest (between-group) analyses were carried out and data underwent spatial reproducibility testing. Compared with healthy subjects, patients showed significantly greater reaction-time (RT) interference but normal RT accuracy on the Stroop task. This pattern correlated with significant under-activation of the posterior left middle-frontal gyri in the patient versus control group. These findings support an emerging model of impaired cognitive control in schizophrenia and suggest that there is significant dysfunction of the dlPFC close to the onset of illness that may coincide with, or be modulated by, the transition-to-illness phase.

Adolescent↗

PubMed2006

Evaluating brain activity in obsessive-compulsive disorder: preliminary insights from a multivariate analysis.

Obsessive-compulsive disorder (OCD) has been linked to a dysfunction of brain corticostriatal networks, although functional imaging studies of OCD rarely apply network-sensitive analysis methods. In this study, we compared a univariate and a multivariate analysis of PET data in OCD patients and healthy subjects; the latter approach was considered more suitable for characterizing functional networks of brain activity. Although both methods suggested there was abnormal corticostriatal activity in OCD patients, the nature, extent and magnitude of this activity was clearly enhanced by the multivariate approach. Implications for the analysis of such studies are discussed.

Adult↗

PubMed2006

Reward-aversion circuitry in analgesia and pain: implications for psychiatric disorders.

Sensory and emotional systems normally interact in a manner that optimizes an organism's ability to survive using conscious and unconscious processing. Pain and analgesia are interpreted by the nervous system as aversive and rewarding processes that trigger specific behavioral responses. Under normal physiological conditions these processes are adaptive. However, under chronic pain conditions, functional alterations of the central nervous system frequently result in maladaptive behaviors. In this review, we examine: (a) the interactions between sensory and emotional systems involved in processing pain and analgesia in the physiological state; (b) the role of reward/aversion circuitry in pain and analgesia; and (c) the role of alterations in reward/aversion circuitry in the development of chronic pain and co-morbid psychiatric disorders. These underlying features have implications for understanding the neurobiology of functional illnesses such as depression and anxiety and for the development and evaluation of novel therapeutic interventions.

Adaptation, Physiological↗

PubMed2005

Functional connectivity during Stroop task performance.

Using covariance-based multivariate analysis, we examined patterns of functional connectivity in rCBF on a practice-extended version of the Stroop color-word paradigm. Color-word congruent and incongruent conditions were presented in six AB trials to healthy subjects during 12 H2(15)O PET scans. Analyses identified two reproducible canonical eigenimages (CE) from the PET data, which were converted to a standard Z score scale after cross-validation resampling and correction for random subject effects. The first CE corresponded to practice-dependent changes in covarying rCBF that occurred over early task repetitions and correlated with improved behavioral performance. This included many regions previously implicated by PET and fMRI studies of this task, which we suggest may represent two "parallel" networks: (i) a cingulo-frontal system that was initially engaged in selecting and mapping a task-relevant response (color naming) when the attentional demands of the task were greatest; and (ii) a ventral visual processing stream whose concurrent decrease in activity represented the task-irrelevant inhibition of word reading. The second CE corresponded to a consistent paradigmatic effect of Stroop interference on covarying rCBF. Coactivations were located in dorsal and ventral prefrontal regions as well as frontopolar cortex. This pattern supports existing evidence that prefrontal regions are involved in maintaining attentional control over conflicting response systems. Taken together, these findings may be more in line with theoretical models that emphasize a role for practice in the emergence of Stroop phenomena. These findings may also provide some additional insight into the nature of anterior cingulate- and prefrontal cortical contributions to implementing cognitive control in the brain.

Arousal↗

PubMed2003

Cerebral function in posttraumatic stress disorder during verbal working memory updating: a positron emission tomography study.

BACKGROUND: This study examined cerebral function in posttraumatic stress disorder (PTSD) during the updating of working memory to trauma-neutral, verbal information. METHODS: Ten PTSD and matched control subjects completed a visuoverbal target detection task involving continuous updating (Variable target condition) or no updating (Fixed target condition) of target identity, with updating activity estimated by condition comparison. RESULTS: Normal updating activity using this paradigm involved bilateral activation of the dorsolateral prefrontal cortex (DLPFC) and inferior parietal lobe. The PTSD group lacked this activation in the left hemisphere and was significantly different from control subjects in this regard, but showed additional activation in the superior parietal lobe, bilaterally. CONCLUSIONS: The pattern of parietal activation suggests a dependence on visuospatial coding for working memory representation of trauma-neutral, verbal information. Group differences in the relative involvement of the DLPFC indicate less dependence in PTSD on the executive role normally attributed to the left DLPFC for monitoring and manipulation of working memory content in posterior regions of the brain.

Female↗