Absolute pitch and planum temporale.

An increased leftward asymmetry of the planum temporale (PT) in absolute-pitch (AP) musicians has been previously reported, with speculation that early exposure to music influences the degree of PT asymmetry. To test this hypothesis and to determine whether a larger left PT or a smaller right PT actually accounts for the increased overall PT asymmetry in AP musicians, anatomical magnetic resonance images were taken from a right-handed group of 27 AP musicians, 27 nonmusicians, and 22 non-AP musicians. A significantly greater leftward PT asymmetry and a significantly smaller right absolute PT size for the AP musicians compared to the two control groups was found, while the left PT was only marginally larger in the AP group. The absolute size of the right PT and not the left PT was a better predictor of music group membership, possibly indicating "pruning" of the right PT rather than expansion of the left underlying the increased PT asymmetry in AP musicians. Although early exposure to music may be a prerequisite for acquiring AP, the increased PT asymmetry in AP musicians may be determined in utero, implicating possible genetic influences on PT asymmetry. This may explain why the increased PT asymmetry of AP musicians was not seen in the group of early beginning non-AP musicians.

Performance evaluation of an automated system for registration and postprocessing of CT scans.

A prototype system optimized for automatic registration of CT scans and applications such as subtraction enhancement and CT angiography was evaluated. Co-registration was performed on 50 studies of various types, including CT angiograms. Mean registration speed was 109 s; accuracy was 2.0 mm. Examples of subtraction enhancement and automatic extraction of the vascular tree are provided. Unattended registration was demonstrated in routine application. Subtraction-enhanced images and extraction of the vascular tree may be useful in clinical practice.

Schizophrenic subjects activate dorsolateral prefrontal cortex during a working memory task, as measured by fMRI.

BACKGROUND: Neuroimaging studies of schizophrenic subjects performing working memory (WM) tasks have demonstrated a relative hypoactivity of prefrontal cortex compared with normal subjects. METHODS: Using functional magnetic resonance imaging (fMRI), we compared dorsolateral prefrontal cortex (DLPFC) activation in 12 schizophrenic and 10 normal subjects during rewarded performance of a WM task. Subjects performed a modified version of the Sternberg Item Recognition Paradigm (SIRP), a continuous performance, choice reaction time (RT) task that requires WM. We compared a high WM load condition with a nonWM choice RT condition and with a low WM load condition. RESULTS: Schizophrenic subjects performed the tasks better than chance but worse than normal subjects. They showed greater activation than normal subjects in the left DLPFC but did not differ in the right DLPFC or in the control region. In the schizophrenic group, left DLPFC activation was inversely correlated with task performance, as measured by errors. CONCLUSIONS: These findings contrast with previous studies that demonstrated task-related hypofrontality in schizophrenia. Task parameters that may contribute to this difference are discussed. We hypothesize that the performance and activation differences we observed are also manifestations of prefrontal dysfunction in schizophrenia. They reflect inefficient functioning of the neural circuitry involved in WM.

Comparison of the BOLD- and EPISTAR-technique for functional brain imaging by using signal detection theory.

Two magnetic resonance imaging techniques, BOLD (blood oxygenation level dependent) and EPISTAR (echo-planar imaging and signal targeting with alternating radio-frequency), were compared for functional brain imaging. Ten volunteers were imaged performing a sequential finger to thumb opposition task alternating with no movement conditions. Techniques were compared using variance maps and signal detection theory (ROC analysis). True positive activation in regions of interest with expected task-dependent signal changes were computed versus false activation rates in regions in which no activation was expected. D-prime coefficients were calculated for each comparison and statistically compared using a paired t test. Activation in the perirolandic region was seen in all volunteers with both techniques. There was no significant difference for the d-prime between BOLD and EPISTAR. These results indicate that based on a different physiologic principle, EPISTAR is an alternative to BOLD to perform fMRI with similar results.

EEG-triggered echo-planar functional MRI in epilepsy.

We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.

Cerebral activation covaries with movement rate.

An important aspect in brain activation studies is the relationship between neuronal activity and measurable indices of function. We applied functional magnetic resonance imaging (fMRI) to investigate blood flow-related MR signal changes in response to different rates of repetitive movements of the index finger. The contralateral precentral gyrus and the posterior frontomesial cortex revealed a significant increase in MR signal over baseline for 1, 2 and 3 Hz finger movements, with a linear effect of rate in the precentral gyrus. Increased firing of neuronal aggregates or recruitment of additional neuronal units within the primary motor cortex necessary for increased output to target neurons and maintaining posture of nearby distal and proximal joints may contribute to the activation pattern.

Cortical activation in the human brain during lateral saccades using EPISTAR functional magnetic resonance imaging.

The location of the human cortical substrate underlying simple horizontal saccadic eye movements was investigated using echoplanar functional magnetic resonance imaging (fMRI) in young healthy volunteers. Echoplanar imaging with signal targeting and alternating radiofrequency (EPISTAR), a novel perfusion technique, measured signal intensity changes in one to four contiguous 10-mm slices centered to include both striate cortex and putative frontal eye fields during horizontal saccade and fixation conditions. Subtraction images of self-paced visually guided saccadic versus fixation conditions showed bilateral marked and statistically significant localized signal increases in the precentral region (Brodmann areas 4, 6) and peristriate cortex (areas 17, 18, 19) and qualitative increases in the superior medial frontal region, as identified by a Talairach-Tournoux generalized template in the brain slices that were scanned. Additional parietal activation occurred during a target-guided saccade task. Our data (i) support the localization of the human FEF, as identified by simple, nonexploratory saccadic eye movements, in the precentral motor strip and premotor cortex, (ii) show individual variability in the exact anatomical location of saccade-related activations, and (iii) confirm that the EPISTAR technique can demonstrate localized signal increases during a behavioral task.

Noninvasive perfusion imaging of human brain tumors with EPISTAR.

A total of 17 patients with histologically proven diagnoses of low-grade astrocytoma (n = 4), high-grade astrocytoma (n = 8), lymphoma (n = 3), and meningioma (n = 2) were examined by using EPISTAR MR imaging. Meningiomas had the highest EPISTAR tumor/white matter contrast and low-grade astrocytomas and lymphomas the lowest. High-grade astrocytomas demonstrated elevated EPISTAR signal with marked regional heterogeneity. There was agreement between tumor vascularity by SPECT and EPISTAR in the five cases where both were done. Our results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection.

Shared neural substrates controlling hand movements in human motor cortex.

Voluntary hand movements in humans involve the primary motor cortex (M1). A functional magnetic resonance imaging method that measures relative cerebral blood flow was used to identify a distributed, overlapping pattern of hand movement representation within the posterior precentral gyrus, which contains M1. The observed pattern resembles those reported in nonhuman primates and differs from a somatotopically organized plan typically used to portray human motor cortex organization. Finger and wrist movements activated a wide expanse of the posterior precentral gyrus, and representations for different finger movements overlapped each other and the wrist representation. Multiple sites of activation occurred in the precentral gyrus for all movements. The overlapping representations may mediate motor and cognitive functions requiring coordinated neural processing for finger and wrist actions rather than discrete control implied by somatotopic maps.

Qualitative mapping of cerebral blood flow and functional localization with echo-planar MR imaging and signal targeting with alternating radio frequency.

PURPOSE: To create qualitative maps of cerebral blood flow (CBF) with the EPISTAR (echo-planar imaging and signal targeting with alternating radio frequency) technique. MATERIALS AND METHODS: The EPISTAR technique was performed in a pig model of hypercapnia and then tested in 26 volunteers by using various paradigms for cortical activation. Echo-planar images were acquired with and without use of a radio-frequency inversion pulse applied to inflowing arterial spins. A qualitative map of CBF was then created by subtracting the image obtained without the radio-frequency pulse from that obtained with the radio-frequency pulse. RESULTS: Progressively more distal portions of the tagged vessels were seen as the inflow time was lengthened until cortical enhancement was seen for inflow times of approximately 1 second or longer. Signal intensity increases from rest to sensorimotor activation ranged from 13% to 193%. CBF changes in the motor strip, primary visual cortex, and the motor area for eye movements were well localized to the cortical gray matter ribbon. CONCLUSION: The EPISTAR technique is a rapid, noninvasive means for creating qualitative maps of CBF.