Previous functional neuroimaging studies have not determined cortical areas of selective somatosensory processing of stimulus attributes or location. To address this, we studied 20 subjects trained in two tactile tasks. For both tasks, a set of domes with gratings was used. Gratings were delivered to the immobilized finger. For each trial, a grating was first applied distally with the bars/grooves parallel to the long axis of the finger. Subjects were either required to judge if the grating orientation (GOT) or stimulation site (location task (LOT) changed during a 2nd presentation. Subjects attended to either orientation or location while activations were measured using block design fMRI at 3T. Group performance was very similar for the GOT (74% correct responses) and LOT (74%). Similar activations for both tasks were seen in the primary and secondary somatosensory cortices. The intraparietal sulcus (IPS) was preferentially activated bilaterally in most subjects during the GOT. However, there were signifi...

The capacity to attend to task demands while viewing nontask-related emotional stimuli undergoes profound development during adolescence. However, researchers are only beginning to explore neurobiological correlates of this cognitive process. In the present investigation, 17 adolescents (9-17 years of age) and 17 adults (25-36 years of age) were scanned using event-related fMRI at 3T. Subjects viewed neutral and emotional faces (angry, fearful and happy) passively and also while attending to emotional and physical features. In the initial analysis, three main results emerged. (1) Adolescents showed greater amygdala and prefrontal cortex activation than adults during passive viewing of angry vs. neutral faces. (2) Both adults and adolescents engaged ventral lateral and dorsal prefrontal regions while attending to internal fear state during angry vs neutral face viewing. (3) Greater discriminant activation emerged in adults vs. adolescents within the contrast of internal fear rating to angry faces vs. physic...

We measured brain activity, perceptual thresholds, and reading performance in a group of dyslexic and normal readers to test the hypothesis that dyslexia is associated with an abnormality in the magnocellular (M) pathway of the early visual system. Functional magnetic resonance imaging (fMRI) was used to measure brain activity in conditions designed to preferentially stimulate the M pathway. Speed discrimination thresholds, which measure the minimal increase in stimulus speed that is just noticeable, were acquired in a paradigm modeled after a previous study of M pathway-lesioned monkeys. Dyslexics showed reduced brain activity compared with controls both in primary visual cortex (V1) and in several extrastriate areas, including area MT and adjacent motion-sensitive areas (MT+) that are believed to receive a predominant M pathway input. There was a strong three-way correlation between brain activity, speed discrimination thresholds, and reading speed. Subjects with higher V1 and MT+ responses had lower per...

Functional magnetic resonance imaging (fMRI) of motor activation in the human cervical spinal cord has been attained by detecting blood oxygenization level dependent (BOLD) signal, by T2* weighted fast low angle shot (FLASH) imaging at 1.5 T (1), and similar results at 3.0 T (2). These studies showed ipsilateral response in the spinal cord during hand motion, and are important in order to determine the plausibility of functional mapping in structures of the central nervous system which are difficult to resolve. The objective of this work is to compare previously published results using FLASH-BOLD (1), with our studies using echo planar imaging (EPI) BOLD in the human spinal cord. Functional images from control volunteers were taken during sensorimotor on-off tasks, using a 1.5 T GE Signa LX scanner and T2* weighted EPI-BOLD pulse sequence, in five contiguous axial slices (8mm thick), centered at the cervical region at C6. Functional images were analyzed pixel by pixel with cross-correlation to a box car on...

We used MRI to investigate the effect of normal aging on the volume of selected brain structures in seven young (5-10 yrs.), five middle-aged (11-20 yrs.) and eight old (21-30 yrs.) monkeys (macacca mulatta). A 1.5T Signa GE scanner acquired coronal proton density- and T2-weighted images using two interleaved dual-echo spin-echo sequences [TR=3000ms; TE=30/80ms; 2.7mm slc, FOV=150mm (256 x 256), 1 nex]. The images were filtered to improve signal-to-noise, then the intra-cranial cavity (ICC) was segmented under visual guidance. Voxels within the ICC were classified and grouped into 11 structures of interest using automated statistical Expectation-Maximization (EM), and Spatially Varying Classification (SVC) segmentation algorithms adapted for monkey MRI analysis. One-way ANOVA revealed an overall significant effect of age group on the volume of forebrain white matter [F(2,17)=4.53, p=0.03]. A posteriori comparisons showed a significant reduction of forebrain white matter volume in the old-aged monkeys when ...

Quantitative MRI techniques provide a good tool for studying brain-behavior relations in vivo. In this study, we examined the relation between performance in 2 memory tasks and the volumes of given brain regions in 44 elderly participants; 25 were diagnosed with mild cognitive impairment and 19 had no cognitive impairment. Each subject underwent a high resolution MRI scan and was examined with 1) verbal and spatial versions of the Buschke controlled learning task (BCL); 2) self ordered pointing task (SOP) that assesses working memory. Volumes of the hippocampal formation (HF) and entorhinal cortex (EC) were derived from 1.6 mm gapless coronal slices taken perpendicular to the long axis of the HF, while the cingulate gyrus (CG) was segmented from images taken perpendicular to the AC-PC line. To correct for individual differences in brain size, volumes of regions of interest (ROI) were divided by total intracranial volume. Regression analyses using HF, EC, anterior and posterior CG volumes showed a task x RO...

With high resolution MRI techniques, it is now possible to examine alterations in brain anatomy in vivo and to identify regions affected in the earliest stages of Alzheimer’s disease (AD). Post mortem pathological studies have implicated the entorhinal cortex (EC) as one of the early sites of involvement in AD. Recent studies have demonstrated that both the EC and the hippocampal formation (HF)are significantly atrophied in patients with mild cognitive impairment(MCI), although there is some controversy as to which of these 2 regions is better at predicting conversion to AD. In the present study, 25 elderly participants diagnosed with MCI were examined with an MRI scan near the time of diagnosis. Follow-up clinical evaluations showed that 8 of the 25 participants converted to AD within 3 years of their initial work-up. Both HF and EC volumes were derived from 1.6 mm, gapless, coronal T1-weighted images taken perpendicular to the long axis of the HF using the Analyze software. To correct for individual diff...

Individual hippocampal neurons selectively increase their firing rates in specific spatial locations. As a population, these neurons provide a decodable representation of space that is robust against changes to sensory- and path-related cues. This neural code is sparse and distributed, theoretically rendering it undetectable with population recording methods such as functional magnetic resonance imaging (fMRI). Existing studies nonetheless report decoding spatial codes in the human hippocampus using such techniques. Here we present results from a virtual navigation experiment in humans in which we eliminated visual- and path-related confounds and statistical limitations present in existing studies, ensuring that any positive decoding results would represent a voxel-place code. Consistent with theoretical arguments derived from electrophysiological data and contrary to existing fMRI studies, our results show that although participants were fully oriented during the navigation task, there was no statistical ...

Considerable insight into the architecture of reasoning could be gained by isolating the network of brain areas that supports this essential function. This study employed fMRI and a deductive reasoning task, performed either with visual or auditory stimuli, to identify the modality-independent brain areas associated with reasoning. Anatomical and functional images were acquired on a GE Signa 1.5T scanner equipped for echoplanar imaging. The activation epoch consisted of 10 trials where each trial included the presentation of two arguments and the production of a conclusion. A voxel-by-voxel, multistage statistical analysis and a logical AND operation isolated those voxels that were associated with the task performed in both sensory modalities. A conservation stage identified the supra-modal brain regions that were conserved across all 7 subjects. The pattern of brain regions that subserved reasoning consisted of left inferior frontal gyrus (Brodmann's areas (BA) 44 and 45), medial frontal gyrus (BA 6), and...

The essential role of the cerebellum in eyeblink classical conditioning in non-human mammals is well documented, and in animals we reported high correlations between Purkinje cell number and associative learning. In elderly humans we found a dramatic relationship between cerebellar volume corrected for total cranial volume and conditioned response (CR) percentage. Neither hippocampal nor total cerebral volume correlated with conditioning. In the present study, anatomical (volumetric) brain magnetic resonance imaging (MRI), delay eyeblink conditioning, and neuropsychological testing were carried out in adults ranging in age from 24 to 87 years. The inclusion of younger adult subjects' cerebellar volume and conditioning performance maintained the very strong relationship between cerebellar volume and associative learning (r = .82; p < .005). Because of the magnitude of Purkinje cells and their dendritic arbor, it is likely that the documented smaller volume of the older adult cerebellum is associated with sh...