Behavioral research has demonstrated three major components of the lexical-semantic processing system: automatic activation of semantic representations, strategic retrieval of semantic representations, and inhibition of competitors. However, these component processes are inherently conflated in explicit lexical-semantic decision tasks typically used in functional magnetic resonance imaging (fMRI) research. Here, we combine the logic of behavioral priming studies and the neurophysiological phenomenon of fMRI priming to dissociate the neural bases of automatic and strategic lexical-semantic processes across a series of three studies. A single lexical decision task was used in all studies, with stimulus onset asynchrony or linguistic relationship between prime and target being manipulated. Study 1 demonstrated automatic semantic priming in the left mid-fusiform gyrus (mid-FFG) and strategic semantic priming in five regions: left middle temporal gyrus (MTG), bilateral anterior cingulate, anterior left inferior...

In the auditory modality, music and speech have high informational and emotional value for human beings. However, the degree of the functional specialization of the cortical and subcortical areas in encoding music and speech sounds is not yet known. We investigated the functional specialization of the human auditory system in processing music and speech by functional magnetic resonance imaging recordings. During recordings, the subjects were presented with saxophone sounds and pseudowords /ba:ba/ with comparable acoustical content. Our data show that areas encoding music and speech sounds differ in the temporal and frontal lobes. Moreover, slight variations in sound pitch and duration activated thalamic structures differentially. However, this was the case with speech sounds only while no such effect was evidenced with music sounds. Thus, our data reveal the existence of a functional specialization of the human brain in accurately representing sound information at both cortical and subcortical areas. They ...

Zebra finch males learn their songs from an adult tutor early in life. Tutor song-induced neuronal activation in the caudomedial nidopallium (NCM) in male zebra finches is related to the strength of song learning. Neurons in the NCM are also responsive to the playback of bird’s own song (BOS) as well as conspecific song. To determine which acoustic features are relevant for song responsiveness in the NCM, we used blood oxygenation level dependent (BOLD) fMRI to investigate the neuronal activation induced by sound presentation. Previous work from our group (Neuroimage, 25, 1242-55) demonstrated that BOLD fMRI is able to reveal brain activity in the NCM upon hearing conspecific song or music. In the present study we measured the BOLD response in Field L and in the NCM in 5 anaesthetized male zebra finches during presentation of BOS, song composed of randomly ordered syllables of the bird’s repertoire, reversed BOS, synthetic sounds with power and spectro-temporal modulation spectra matched to BOS (song rippl...

MRI is used to monitor longitudinal changes in CNS morphology due to injury. Gadolinium (Gd) is the standard MRI contrast agent used for CNS injury in humans. We tested the ability of gadolinium to enhance lesion contrast on lesion progression from acute to chronic time points. Animals were imaged at 5 days, 3 weeks, 7, 15, and 17 months post injury (C4), and 3 days, 4 weeks, 6, 7, 15, 16, and 17 months post injury (T9). Animals were imaged with a 7.0 Tesla horizontal bore Bruker (Bruker Biospin, Billerica, MA) via 3D Turbo RARE (FOV 7.68X2.56X2.56 cm, Matrix 512X256X256, TR 800 ms, TE 8.2 ms, RARE factor 2). Animals were anesthetized with isolflurane 1.5%, tail vein injected with 1.5 ml Omniscan (gadodiamide, Amersham Health, Princeton, NJ), then placed in a 72mm birdcage volume coil. No implanted coils were used for this study. Comparisons at different timepoints clearly revealed the lesion presence at all time points. Lesions were significantly Gd enhanced, even at 17 months. Apparent lesion volume chan...

INTRODUCTION As a sentence like “The citizens heard the election result was fixed” is being read, “the election result” may seem the direct object of “heard,” but it is the subject of a sentence complement verb. If we add a phrase before the ambiguity can be resolved – e.g. “The citizens heard the election result broadcasted on TV was fixed” – the disambiguation is further delayed. We hypothesized that sentence comprehension depends in part on dissociable resources like working memory and planning which are supported by a large-scale neural network. METHODS 240 written sentences were shown to 19 subjects, phrase by phrase: [initial] [verb] [noun] ([WM]) [concluding]. 1/2 had a direct object (DO) structure, 1/2 sentence complement (SC). 1/3 had a DO-bias verb, 1/3 SC, 1/3 no bias. 1/2 had a DO-bias noun, 1/2 SC. Half had an additional “WM phrase”. Event-related BOLD fMRI was analyzed with a random effects model (SPM99). Images were registered, aligned (Talairach) and spatially smoothed (8mm). RESULTS A 2x2x...

In the present study, we aimed to dissociate the neural correlates of two subprocesses involved in the preparatory period in the context of arbitrary, prelearned stimulus-response (S-R) associations, namely, S-R mapping and movement planning (MP). We teased apart these two subprocesses by comparing three tasks in which the complexity of both S-R mapping and MP were independently manipulated: simple reaction time (SRT) task, go/no-go reaction time (GNGRT) task, and choice reaction time (CRT) task. We found that a more complex S-R mapping, which is the common element differentiating CRT and GNGRT from SRT, was associated with higher brain activation in the left superior parietal lobe (SPL). Conversely, a greater number of planned finger movements, which is the common difference between CRT and both SRT and GNGRT, was associated with higher brain activation in a number of frontal areas, including the left supplementary motor area (SMA), left dorsal premotor cortex (dPM), and left anterior cingulate cortex (AC...

We are investigating the feasibility and reliability of using MRI as a method to accurately measure lesion volume in the spinal cord of contusion-injured mice. We compared the results of lesion volumes determined using T-1 weighted images in a 3-D gradient echo sequence on a 7T MRI with lesion volumes determined by stereological sampling of fibronectin immunoreactivity in sections processed from the same spinal cords. Histology was performed on 10 µm polyester wax-embedded sections, using the Cavalieri method. Eight week old female C57Bl/6 mice received a mild (30 kDyne), moderate (50 kDyne), or severe (70 kDyne) contusion injury at the T9 vertebral level using the IH Impactor (Infinite Horizons). Control mice received a T9 laminectomy only. Mice were tested at 3 days, and weekly after the injury for functional recovery with the BBB (Basso, Beattie, Bresnahan) and BMS (Basso Mouse Scale) locomotor rating scales. Eight weeks after injury, mice were perfused with 4% paraformaldehyde, the spinal cord collecte...

Functional magnetic resonance imaging (fMRI) has provided intriguing insights into the topography and functional organization of visual cortical areas in the human brain. However, little is known about the functional anatomy of subcortical nuclei. Here, we used high-resolution fMRI (1.5 × 1.5 × 2 mm3) at 3 tesla to investigate the retinotopic organization of the human lateral geniculate nucleus (LGN). The central 15° of the visual field were mapped using periodic flickering checkerboard stimuli that evoked a traveling wave of activity. The contralateral visual hemifield was represented with the lower field in the medial-superior portion and the upper field in the lateral-inferior portion of each LGN. The horizontal meridian was significantly overrepresented relative to the vertical meridian. The fovea was represented in posterior and superior portions, with increasing eccentricities represented more anteriorly. The magnification of the fovea relative to the periphery was similar to that described for human...

Until recently, the cerebellum was held to play its chief role in motor control. Keele and Ivry (1991) proposed that it may provide timing services subserving diverse aspects of brain function. Speech perception, which requires minute differentiation of time intervals, is compromised by cerebellar pathology and activates the right neocerebellum. In the current study, a non-speech task involving duration storage and comparison activates a lateral crus I area of the right cerebellar hemisphere (see figure). Concomitantly, a left prefrontal cluster was observed. The functional magnetic resonance imaging study employed single-shot double-echo echo-planar imaging to reduce image distortion and acquisition time with whole-brain coverage (TE = 28 and 66 ms at 1.5 T, TR = 5 sec, 28 slices, TA = 2.8 sec). Twelve healthy subjects performed two tasks: identifying pauses between tones as `short' or `long' (30-130 ms), and deciding which of two pauses was longer. The activation pattern in the discrimination task was an...

Although extensive evidence exists for the reinforcing properties of drugs of abuse such as cocaine, relatively less research has addressed the functional neuroanatomical correlates of the cognitive sequelae of these drugs. We present a functional magnetic resonance imaging study of a GO-NOGO task in which successful performance required prepotent behaviors to be inhibited. Significant cingulate, pre-supplementary motor and insula hypoactivity was observed for both successful NOGOs and errors of commission in chronic cocaine users relative to cocaine-naive controls. This attenuated response, in the presence of comparable activation levels in other task-related cortical areas, suggests cortical and psychological specificity in the locus of drug abuse-related cognitive dysfunction. The results suggest that addiction may be accompanied by a disruption of brain structures critical for the higher-order, cognitive control of behavior.