Glucocorticoids are known for their slow-acting genomic effects as transcription factors binding to a soluble steroid receptor. However, there are many reports that glucocorticoids can have immediate effects on neuronal excitability in the hypothalamus and hippocampus of mammals. While the glucocorticoid membrane receptor that presumably mediates this electrical activity has eluded researchers the immediate elctrophysiological and behavioral effects of abrupt increases in plasma levels of stress hormones are undeniable and well documented. Functional MRI with 3D computational analysis in conscious animals provides a method for identifying those brain areas and neural networks sensitive to the abrupt rise in plasma glucocorticoids that occur during a stress response. Rats showed a dose dependent change in brain activity to iv injection of a soluble steroid complex of corticosterone and 2-hydroxypropyl-B-cyclodextrin (vehicle, 1, 2.5, 10 mg/kg). The highest dose resulted in plasma corticosterone levels of ap...

Information integration across different sensory modalities contributes to object recognition, the generation of associations and long-term memory representations. Here, we used functional magnetic resonance imaging adaptation to investigate the presence of sensory integrative effects at cortical levels as early as nonprimary auditory and extrastriate visual cortices, which are implicated in intermediate stages of object processing. Stimulation consisted of an adapting audiovisual stimulus S1 and a subsequent stimulus S2 from the same basic-level category (e.g., cat). The stimuli were carefully balanced with respect to stimulus complexity and semantic congruency and presented in four experimental conditions: (1) the same image and vocalization for S1 and S2, (2) the same image and a different vocalization, (3) different images and the same vocalization, or (4) different images and vocalizations. This two-by-two factorial design allowed us to assess the contributions of auditory and visual stimulus repetiti...

Functional magnetic resonance imaging in awake monkeys and humans was used to compare object adaptation in shape-sensitive regions of these two species under identical and different size conditions. Object adaptation was similar in humans and monkeys under both conditions. Neither species showed complete size invariance, in agreement with single-cell studies. Both the macaque inferotemporal (IT) complex and human lateral occipital complex (LOC) displayed an anteroposterior gradient in object adaptation and size invariance, with the more anterior regions being more adaptable and size invariant. The results provide additional evidence for the homology between the macaque IT cortex and human LOC but also add to the growing list of differences between human and monkey intraparietal sulcus regions.

Response anticipation and response conflict processes are supported by executive control. However, few neuroimaging studies have attempted to study the relationship between these two processes in the same experimental session. In this study, we isolated brain activity associated with response anticipation (after a cue to prepare vs relax) and with response conflict (responding to a target with incongruent vs congruent flankers) and examined the independence and interaction of brain networks supporting these processes using event-related potentials (ERPs) and functional magnetic resonance imaging. Response anticipation generated a contingent negative variation ERP that correlated with shorter reaction times, and was associated with activation of a thalamo-cortico-striatal network, as well as increased gamma band power in frontal and parietal regions, and decreased spectral power in theta, alpha, and beta bands in most regions. Response conflict was associated with increased activation in the anterior cingul...

Recent neurophysiological findings from the monkey hippocampus showed dramatic changes in the firing rate of individual hippocampal cells as a function of learning new associations. To extend these findings to humans, we used blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to examine the patterns of brain activity during learning of an analogous associative task. We observed bilateral, monotonic increases in activity during learning not only in the hippocampus but also in the parahippocampal and right perirhinal cortices. In addition, activity related to simple novelty signals was observed throughout the medial temporal lobe (MTL) memory system and in several frontal regions. A contrasting pattern was observed in a frontoparietal network in which a high level of activity was sustained until the association was well learned, at which point the activity decreased to baseline. Thus, we found that associative learning in humans is accompanied by striking increases in BOLD ...

Songbirds share with humans the capacity to produce learned vocalizations (song). The neural substrate for song learning and production, the song control system (SCS), is a bilateral circuit of distinct, strongly ipsilaterally interconnected brain regions which displays a remarkable neuroplasticity. After years of bird sacrifice to study the SCS, we recently (Van der Linden et al., 2002) visualized two major song control nuclei, nucleus robustus arcopalii (RA) and X repeatedly in a living songbird using Manganese Enhanced Magnetic Resonance Imaging (MEMRI). It was our aim to extend this accomplishment and visualize the entire SCS in living songbirds taking advantage of the transsynaptic paramagnetic tract tracing capacities of manganese. To that end we stereotactically injected very small volumes (10 nl) of MnCl2 (minimizing possible neurotoxicity) into HVC of the right and into MAN (nucleus magnocellularis nidopalli anterioris) of the left hemisphere, and monitored the manganese tracing between ipsilatera...

The ability to form episodic memories requires one to bind relations between aspects of events that unfold over time. Several neuroimaging studies have investigated the encoding of specific items in isolation, however little is known about the neural mechanisms that support the formation of associations between temporally distinct items. Here, we used event-related functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms of relational binding and item-specific processing in working memory (WM), and the impact of these operations on subsequent long-term memory (LTM) formation. During scanning, subjects made decisions about pairs of words separated by a delay of 9 seconds. On each trial, they were instructed to make a perceptual judgment about the first word (S1). When the second word (S2) appeared, they were either prompted to make a semantic decision specific to S2 (item-specific trials) or to make a decision that required comparison of S2 and S1 (relational trials). After scanning...

Nigrostriatal degeneration, the pathological hallmark of Parkinson's disease (PD), is mirrored by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication. MPTP-treated animals show the common behavioral, motor, and pathological features of human disease. We demonstrated previously that adoptive transfer of Copaxone (Cop-1) immune cells protected the nigrostriatal dopaminergic pathway in MPTP-intoxicated mice. Herein, we evaluated this protection by quantitative proton magnetic resonance spectroscopic imaging (1H MRSI). 1H MRSI performed in MPTP-treated mice demonstrated that N -acetyl aspartate (NAA) was significantly diminished in the substantia nigra pars compacta (SNpc) and striatum, regions most affected in human disease. When the same regions were coregistered with immunohistochemical stains for tyrosine hydroxylase, numbers of neuronal bodies and termini were similarly diminished. MPTP-intoxicated animals that received Cop-1 immune cells showed NAA levels, in the SNpc and striatum, nearly eq...

Read science policy and advocacy news from the week of October 20, 2017

Neuroimaging studies are increasingly targeting diverse populations represented by different genetic, social, phenotypic, and geographical profiles (e.g. Rueckl et al., 2015), which are made more feasible through data collection at multiple sites using ...