During rest, brain activity is synchronized between different regions widely distributed throughout the brain, forming functional networks. However, the molecular mechanisms supporting functional ...connectivity remain undefined. We show that functional brain networks defined with resting-state functional magnetic resonance imaging can be recapitulated by using measures of correlated gene expression in a post mortem brain tissue data set. The set of 136 genes we identify is significantly enriched for ion channels. Polymorphisms in this set of genes significantly affect resting-state functional connectivity in a large sample of healthy adolescents. Expression levels of these genes are also significantly associated with axonal connectivity in the mouse. The results provide convergent, multimodal evidence that resting-state functional networks correlate with the orchestrated activity of dozens of genes linked to ion channel activity and synaptic function.
Distractibility defined operationally as a lack of stability in central-gaze fixation has been studied using two different oculomotor tasks that require the suppression of reflexive saccades ...triggered by the sudden appearance of novel, peripheral visual stimuli. In the first task ('Instructed'), maintenance of central gaze fixation was based on verbal instruction, whereas, in the second task ('Non-Instructed'), it was based upon a foveating mechanism maintained by sensory stimulation during the performance of a categorization task. 15 schizophrenics and 20 healthy control subjects were tested in the two tasks. Schizophrenics made more saccades than control subjects in the Instructed task only. The Instructed task saccade rate correlated significantly with scores on neuropsychological tests sensitive to frontal lobe dysfunction. Because the type of deficit observed in schizophrenics resembled that previously seen in patients with unilateral lesions of the ventrolateral convexity of frontal lobe, frontal lobe dysfunction was proposed as underlying the high task-specific distractibility of schizophrenics.
We present a new approach to studying functional connectivity in the human brain. This approach is based on the observation that when we engage in motor activity, a discharge corollary to the motor ...command is sent from motor to sensory structures. Thus, as long as movement-related sensory input is either prevented or masked, modulation of neuronal activity in sensory structures would indicate the presence of functional connectivity between the motor and the sensory regions. Using positron emission tomography, such a central interaction between motor and sensory regions can be assessed by measuring regional changes in cerebral blood flow (CBF) in sensory regions. In this paper, we describe the experimental design and the results of two studies of corollary discharges, namely those generated during eye movements and speech. In these studies, a graded approach was used to establish the relationship between the number of eye movements or utterances and CBF in visual or auditory regions, respectively. Significant covariations between the number of movements and CBF in sensory regions were found, thus indicating the presence of functional connectivity between motor and sensory regions. In addition, interregional CBF covariations were computed and the effect of removing the intersubject variance on these covariations was evaluated. The corollary-discharge-based approach to studying functional connectivity is discussed in the context of more traditional computational approaches to network analysis in functional brain imaging.
We used positron emission tomography (PET) in ten subjects to study the brain regions involved in voluntary shifts of attention. For six scans, subjects performed a visual target detection task in ...which the location of the target was indicated in advance on some proportion of trials by the appearance of an arrow cue at fixation. The informative cues were successful in speeding reaction time to the target. Blood flow in the left putamen was correlated with the proportion of informative cues provided within a scan. We discuss this finding in terms of three possible interpretations: attentional shifts, response inhibition, and motor preparation related to the use of the right hand to respond. Blood flow in cortical regions commonly associated with attention was not related to cue ratio, a finding that may reflect automatization of the processes involved in interpreting and using the cues.
PDF
