Functional brain organization of preparatory attentional control in visual search

Looking for an object that may be present in a cluttered visual display requires an advanced specification of that object to be created and then matched against the incoming visual input. Here, fast event-related fMRI was used to identify the brain networks that are active when preparing to search for a visual target. By isolating the preparation phase of the task it has been possible to show that for an identical stimulus, different patterns of cortical activation occur depending on whether participants anticipate a 'feature' or a 'conjunction' search task. When anticipating a conjunction search task, there was more robust activation in ventral occipital areas, new activity in the transverse occipital sulci and right posterior intraparietal sulcus. In addition, preparing for either type of search activated ventral striatum and lateral cerebellum. These results suggest that when participants anticipate a demanding search task, they develop a different advanced representation of a visually identical target stimulus compared to when they anticipate a nondemanding search. © 2013 Elsevier B.V. All rights reserved

Neural mechanisms of top-down control during visual search: effects of template complexity

Neural mechanisms of top-down control during visual search: effects of template complexit

fMRI BOLD signal changes in elite swimmers while viewing videos of personal failure

Athletes who fail are susceptible to negative affect (NA) and impaired future performance. Functional magnetic resonance imaging (fMRI) studies have identified prefrontal, anterior cingulate, and limbic activations following negative mood provocation. Little is known about the neural correlates of negative self-reference (SR), especially in athletes. Even less is known about the neural correlates of the effects of cognitive intervention (CI) in modifying negative SR and NA in this population. In an fMRI study, 13 athletes watched a video of their own career-threatening defeat in two controlled blocks. Between fMRI blocks, they received a 20-min CI designed to assist in event reappraisal and planning for future performance. Relative increases post-CI were seen in premotor (BA6) and sensorimotor (BA4/1) cortices. Correlated with mood ratings, relatively higher pre-CI levels were seen in the ventromedial prefrontal cortex, the right dorsomedial prefrontal cortex (PFC; BA10), the right dorsolateral PFC (BA45), the anterior cingulate, and the right parahippocampus. CI may counteract the detrimental effects of NA and negative SR on premotor and motor activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83878/1/fMRI-BOLD-signal-changes-in-elite-swimmers-while-viewing-videos-of-personal-failure.pd

Abnormal function of the brain system supporting motivated attention in medicated patients with schizophrenia: An fMRI study

Background. Patients with schizophrenia have an impaired ability to generate activity that is appropriate to current circumstances and goals. Method. We report a study using functional magnetic resonance imaging (fMRI) to examine cerebral activity during a three-tone auditory oddball target detection task in a sample of 28 patients with schizophrenia and 28 healthy controls. Results. The patients exhibited significantly less activation in response to target stimuli relative to baseline in an extensive set of sites in association neocortex, paralimbic cortex, limbic structures and subcortical nuclei, yet demonstrated a normal level of activation in the sensorimotor cortex. Comparison of activity elicited by rare target stimuli with that elicited by equally rare novel stimuli makes it possible to distinguish cerebral activity associated with attention to behaviourally salient stimuli from activity associated with attending to other attention-capturing stimuli. This comparison revealed that the patients with schizophrenia also exhibited a deficit in activation of basal forebrain areas that mediate motivation during the processing of behaviourally salient stimuli, including the amygdala, ventral striatum, orbital frontal cortex and rostral anterior cingulate cortex. Conclusion. Patients with schizophrenia have a deficit in function of the brain system concerned with mediating motivation, in addition to a more general deficit in the cerebral response to attention-captivating stimuli.</p

An fMRI investigation of cerebral state and trait markers of schizophrenia

IntroductionIn a recently completed study we demonstrated that stable, medicated schizophrenic patients exhibited an anomalous pattern of cerebral activity during performance of an "N-back" working memory task. Specifically, the extent and intensity of prefrontal and parietal activation was lower in schizophrenic patients than in healthy participants. Moreover, the patients did not activate the thalamus, midbrain, or cerebellum, and they showed greater suppression of the bilateral temporal cortex relative to control subjects (Mendrek et al., 1999). The present study was designed to explore the pattern of cerebral activity in the first-episode schizophrenic patients in two stages of their illness to elucidate which elements of abnormal pattern of cerebral activity represent state and which represent a trait marker of schizophrenia.MethodsEight first-episode schizophrenic patients and eight age, sex, and IQ-matched healthy individuals participated in the study. Patients were scanned for the first time within the first week of their treatment and six to eight weeks following the first scan. The symptoms of their illness diminished significantly with antipsychotic treatment.While in the scanner participants performed the "N-back" working memory task in two 7-min. runs consisting of alternating 30-sec periods of '0-back' and '2-back' conditions with 20-sec periods of rest. During the '0-back' condition subjects were required to press the button anytime they saw an "X" appearing in the sequence of letters. In the '2-back' condition they had to press the button anytime they saw a letter that was identical to one presented two trials back.Imaging was implemented on a standard clinical GE 1.5 T whole-body MRI. Whole brain echo planar fMRI was performed using a gradient echo pulse sequence (TR/TE 3000/40 msec, flip angle 90 degrees, FOV 24x24 cm, 64 x 64 matrix, bandwidth 62.5 kHz, 3.75 x 3.75 in plane resolution, 5 mm slice thickness, 29 slices). The functional images were realigned, motion corrected and normalized into Talairach space using statistical parametric mapping (SPM96). All normalized images representing a given type of epoch ("0-back", "2-back", and "relax") in each run were averaged to generate a single image. These averaged images were then smoothed with a 12mm Gaussian filter. Separate analyses were performed for patients versus control subjects and for patients' first scanning session versus second scanning session, using the SPM random-effects toolkit.ResultsThe comparison of acutely psychotic schizophrenic patients with control participants revealed statistically significant Group by Task ("2-back" versus "0-back") interaction in several cerebral regions. Patients didn't activate left cerebellum during the performance of the "2-back" versus "0-back" condition and they failed to suppress bilateral temporal cortex and medial prefrontal cortex relative to control subjects. The comparison of the pattern of cerebral activation between patients' first and second scanning session also revealed significant interaction. During the first scanning session, while in acutely psychotic state, patients exhibited over-activation in the bilateral medial temporal cortex during performance of the "2-back" versus "0-back" condition in comparison to the second scanning session when their symptoms dissipated with neuroleptic treatment.ConclusionsPresent results obtained in acutely psychotic individuals are consistent with PET studies in chronic, medicated (Frith et al., 1995) and acutely psychotic, unmedicated (Fletcher et al.. 1996) schizophrenic patients, demonstrating that patients failed to suppress their left temporal cortex during word generation. Interestingly, however, in our previous study of remitted, medicated patients we observed greater suppression in patients' temporal cortex relative to control subjects. Therefore, it is possible that abnormal temporal activity represents a state marker of schizophrenia and as such is related to current clinical state. The finding of the left cerebellar under-activity, on the other hand, may represent a trait marker of schizophrenia because we found that deficit in both acutely psychotic and in remitted patients.ReferencesFletcher, P.C., Frith, C.D., Grasby. P.M., Friston, K.J., and Dolan, R.J. (1996). Local and distributed effects of apomorphine on fronto-temporal function in acute unmedicated schizophrenia. Journal of Neuroscience, 16, 7055-7062.Frith C.D, Friston., K.J., Herold., S., Silbersweig, D., Fletcher, P., Cahill, C., Dolan., R.J., Frackowiak, R.S.J., and Liddle, P.F. (1995). Regional brain activity in chronic schizophrenic patients during the performance of a verbal fluency task: Evidence for a failure of inhibition in left superior temporal cortex. British Journal of Psychiatry, 167, 343-349.Mendrek, A., Kiehl, K.A., Smith, A.M., Forster, B.B., Weinberg, J., &amp; Liddle, P.F. (1999). Abnormal coordination of cerebral activity during a working memory task in schizophrenia: An fMRI study. Society for Neuroscience, 25, 2099.<br/

Rostral anterior cingulate cortex dysfunction during error processing in schizophrenia

Previous research has demonstrated that patients with schizophrenia have an impaired ability to monitor erroneous responses to stimuli internally. Event-related potential (ERP) studies of error-eliciting tasks indicate that, in healthy adults, the commission of an erroneous response is associated with a fronto-centrally distributed negative voltage component termed the error negativity (Ne) or error-related negativity (ERN). In patients with schizophrenia, the Ne/ERN elicited by errors of commission (EoC) is reduced in amplitude compared with that elicited in healthy participants. Functional MRI (fMRI) studies and source localization analyses of ERP data in healthy participants suggest that EoC are associated with activity in the rostral anterior cingulate cortex (ACC). Using event-related fMRI, we examined the brain activity associated with EoC in a group of 10 patients with schizophrenia and 16 matched healthy participants. Patients were stable, partially remitted, medicated out-patients recruited from the community. Participants performed a Go/NoGo task variant that was shown previously to elicit a reduced Ne/ERN during EoC in patients with schizophrenia relative to healthy participants, as well as robust rostral ACC activation during EoC in healthy participants. Patients with schizophrenia were characterized by relative under-activity in the rostral ACC compared with healthy participants. There was also evidence for more widespread underactivity in the limbic system. In contrast to these regions of relative hypoactivity, patients with schizophrenia demonstrated hyperactivity relative to healthy participants in bilateral parietal cortex during both EoC and correctly rejected NoGo trials. Our results are consistent with previous ERP research demonstrating functional abnormalities during error processing in schizophrenia. In light of the role of the rostral ACC and other limbic structures in mediating affective and motivational behaviour, our results suggest there may be a disturbed affective or motivational response to the commission of errors in schizophrenia.</p