Adaptive changes in early and late blind: a FMRI study of verb generation to heard nouns

Literacy for blind people requires learning Braille. Along with others, we have shown that reading Braille activates visual cortex. This includes striate cortex (V1), i.e., banks of calcarine sulcus, and several higher visual areas in lingual, fusiform, cuneus, lateral occipital, inferior temporal, and middle temporal gyri. The spatial extent and magnitude of magnetic resonance (MR) signals in visual cortex is greatest for those who became blind early in life. Individuals who lost sight as adults, and subsequently learned Braille, still exhibited activity in some of the same visual cortex regions, especially V1. These findings suggest these visual cortex regions become adapted to processing tactile information and that this cross-modal neural change might support Braille literacy. Here we tested the alternative hypothesis that these regions directly respond to linguistic aspects of a task. Accordingly, language task performance by blind persons should activate the same visual cortex regions regardless of input modality. Specifically, visual cortex activity in blind people ought to arise during a language task involving heard words. Eight early blind, six late blind, and eight sighted subjects were studied using functional magnetic resonance imaging (fMRI) during covert generation of verbs to heard nouns. The control task was passive listening to indecipherable sounds (reverse words) matched to the nouns in sound intensity, duration, and spectral content. Functional responses were analyzed at the level of individual subjects using methods based on the general linear model and at the group level, using voxel based ANOVA and t-test analyses. Blind and sighted subjects showed comparable activation of language areas in left inferior frontal, dorsolateral prefrontal, and left posterior superior temporal gyri. The main distinction was bilateral, left dominant activation of the same visual cortex regions previously noted with Braille reading in all blind subjects. The spatial extent and magnitude of responses was greatest on the left in early blind individuals. Responses in the late blind group mostly were confined to V1 and nearby portions of the lingual and fusiform gyri. These results confirm the presence of adaptations in visual cortex of blind people but argue against the notion that this activity during Braille reading represents somatosensory (haptic) processing. Rather, we suggest that these responses can be most parsimoniously explained in terms of linguistic operations. It remains possible that these responses represent adaptations which initially are for processing either sound or touch, but which are later generalized to the other modality during acquisition of Braille reading skills.     

Smoking and Drinking Behavior in Patients with Head and Neck Cancer: Effects of Behavioral Self-Blame and Perceived Control

Patients who continue to use tobacco or alcohol following treatment for head and neck cancers are at greater risk for cancer recurrence and mortality. The present study examined the effects of behavioral self-blame and perceived control over health on smoking and alcohol use in a sample of 55 patients with cancers of the head and neck. Measures of self-blame, perceived control, and depression were administered and an assessment of past and current smoking and drinking behavior was obtained. As anticipated, continued smoking after completion of oncologic treatment was predicted by the interaction of behavior specific self-blame and perceived control. Patients who attributed the cause of their cancer to their past substance use exhibited a lower likelihood of smoking only if they also held the expectancy that their future cancer-related health was contingent on their own behavior. Among patients not holding the belief that cancer recurrence was contingent on their own actions, self-blame was associated with a higher probability of continued smoking. Self-blame and perceived control had no effect on continued alcohol use.     

Standardized mean regional method for calculating global positron emission tomographic measurements

A new "mean regional" method for calculating global hemispheric values of blood flow, blood volume, and metabolism with positron emission tomography is presented. It is based on a standardized set of regions defined according to coordinates in a stereotactic atlas of the brain. Region locations in each individual scan were determined by a localization technique that is independent of the appearance of the physiological images. Measurements obtained with this mean regional method minimize contributions from nonbrain structures such as ventricles or venous sinuses and provide the necessary basis for comparisons among different subjects and laboratories.     

18F]-labeled 3-deoxy-3-fluoro-D-glucose: synthesis and preliminary biodistribution data.

A cyclotron target system for the production of anhydrous [18F] fluoride ion has been developed and used for the synthesis of carrier-free [18F]-3-deoxy-3fluoro-D-glucose (3-FDG). The synthesis is sufficiently rapid and efficient to allow production of usable amounts of 3-FDG with a 6-MeV cyclotron. Preliminary animal studies show that 3-FDG is in fact a glucose analog.     

Cingulo-opercular control network and disused motor circuits joined in standby mode

Whole-brain resting-state functional MRI (rs-fMRI) during 2 wk of upper-limb casting revealed that disused motor regions became more strongly connected to the cingulo-opercular network (CON), an executive control network that includes regions of the dorsal anterior cingulate cortex (dACC) and insula. Disuse-driven increases in functional connectivity (FC) were specific to the CON and somatomotor networks and did not involve any other networks, such as the salience, frontoparietal, or default mode networks. Censoring and modeling analyses showed that FC increases during casting were mediated by large, spontaneous activity pulses that appeared in the disused motor regions and CON control regions. During limb constraint, disused motor circuits appear to enter a standby mode characterized by spontaneous activity pulses and strengthened connectivity to CON executive control regions.

Disuse is a powerful paradigm for inducing plasticity that has uncovered key organizing principles of the human brain (1–4). Monocular deprivation—prolonged covering of one eye—revealed that multiple afferent inputs can compete for representational territory in the primary visual cortex (1). Similar competition between afferents also shapes the somatomotor system. Manipulations such as peripheral nerve deafferentation, whisker trimming, and limb constraint all drive plasticity in the primary somatosensory and motor cortex (2–4). Most plasticity studies to date have used focal techniques, such as microelectrode recordings, to study local changes in brain function. As a result, little is known about how behavior and experience shape the brain-wide functional networks that support complex cognitive operations (5).The brain is composed of networks of regions that cooperate to perform specific cognitive functions (5–8). These functional networks show synchronized spontaneous activity while the brain is at rest, a phenomenon known as resting-state functional connectivity (FC) (9–11). FC can be measured noninvasively in humans using resting-state functional MRI (rs-fMRI) and has been used to parse the brain into canonical functional networks (12, 13), including visual, auditory, and somatomotor networks (14, 15); ventral and dorsal attention networks (8, 16); a default mode network with roles in internally directed cognition and episodic memory (7, 11); a salience network thought to assess the homeostatic relevance of external stimuli (17); a frontoparietal control network supporting error processing and moment-to-moment adjustments in behavior (18–20); and a cingulo-opercular control network (CON), which maintains executive control during goal-directed behavior (18, 19, 21). Each functional network likely carries out a variety of additional functions.A more recent advance in human neuroscience has been the recognition of individual variability in network organization (22–25). Most early rs-fMRI studies examined central tendencies in network organization using group-averaged FC measurements (10, 12, 13). Recent work has demonstrated that functional networks can be identified in an individual-specific manner if sufficient rs-fMRI data are acquired, an approach termed precision functional mapping (PFM) (22, 23, 26–30). PFM respects the unique functional anatomy of each person and avoids averaging together functionally distinct brain regions across individuals.We recently demonstrated that PFM can be used to follow the time course of disuse-driven plasticity in the human brain (31). Three adult participants (Nico, Ashley, and Omar) were scanned at the same time of day for 42 to 64 consecutive days (30 min of rs-fMRI per day) before, during, and after 2 wk of dominant upper-extremity casting (Fig. 1 A and B). Casting caused persistent disuse of the dominant upper extremity during daily behaviors and led to a marked loss of strength and fine motor skill in all participants. During casting, the upper-extremity regions of the left primary somatomotor cortex (L-SM1_ue) and right cerebellum (R-Cblm_ue) functionally disconnected from the remainder of the somatomotor network. Disused motor circuits also exhibited large, spontaneous pulses of activity (Fig. 1C). Disuse pulses did not occur prior to casting, started to occur frequently within 1 to 2 d of casting, and quickly waned after cast removal.Open in a separate windowFig. 1.Experimental design and spontaneous activity pulses. (A) Three participants (Nico, Ashley, and Omar) wore casts covering the entire dominant upper extremity for 2 wk. (B) Participants were scanned every day for 42 to 64 consecutive days before, during, and after casting. All scans included 30 min of resting-state functional MRI. (C) During the Cast period, disused somatomotor circuits exhibited large pulses of spontaneous activity. (C, Left) Whole-brain ANOVA showing which brain regions contained disuse-driven pulses. (C, Right) Time courses of all pulses recorded from the disused primary somatomotor cortex.Somatomotor circuits do not function in isolation. Action selection and motor control are thought to be governed by complex interactions between the somatomotor network and control networks, including the CON (18). Prior studies of disuse-driven plasticity, including our own, have focused solely on somatomotor circuits. Here, we leveraged the whole-brain coverage of rs-fMRI and the statistical power of PFM to examine disuse-driven plasticity throughout the human brain.     

Glucose metabolism in the amygdala in depression: relationship to diagnostic subtype and plasma cortisol levels

In a previous positron emission tomography (PET) study of major depression, we demonstrated that cerebral blood flow was increased in the left amygdala in unipolar depressives with familial pure depressive disease (FPDD) relative to healthy controls [J. Neurosci. 12 (1992) 3628.]. These measures were obtained from relatively low-resolution PET images using a stereotaxic method based upon skull X-ray landmarks. The current experiments aimed to replicate and extend these results using higher-resolution glucose metabolism images and magnetic resonance imaging (MRI)-based region-of-interest (ROI) analysis. The specificity of this finding to FPDD was also investigated by assessing depressed samples with bipolar disorder (BD-D) and depression spectrum disease (DSD). Finally, the relationship between amygdala metabolism and plasma cortisol levels obtained during the scanning procedure was assessed. Glucose metabolism was measured using PET and 18F-fluorodeoxyglucose (18FDG) in healthy control (n=12), FPDD (n=12), DSD (n=9) and BD-D (n=7) samples in the amygdala and the adjacent hippocampus. The left amygdala metabolism differed across groups (P<.001), being increased in both the FPDD and BD-D groups relative to the control group. The left amygdala metabolism was positively correlated with stressed plasma cortisol levels in both the unipolar (r=.69; P<.005) and the bipolar depressives (r=0.68;.1相似文献   

Measurement of cerebral vascular extraction fractions in the rat using intracarotid injection techniques

A small volume (5 μl) common carotid arterial injection method is described for the quantitation of cerebral vascular extraction fractions (E_t) of diffusion limited tracer molecules in the rat. The method is a modification of a technique diffusion duced by Oldendorf and widely used for the study of blood-brain barrier phenomena. While the Oldendorf technique has proven valuable for estimating the relative permeabilities of substances, it is limited in measuring E_t under conditions of physiologically or pharmacologically altered permeability or blood flow. The method described in this paper — using a small volume (5 μl) common carotid injection, a freely diffusible reference tracer, [¹⁴C]butanol, and a 5 sec circulation time — allows for measurements of E_t that reflect changes in blood flow and small differences in permeability. The modified method is important for the study of the regulation of cerebral vascular permeability and flow in an inexpensive animal model.     

Emotion-induced changes in human medial prefrontal cortex: I. During cognitive task performance

Regional cerebral blood flow (BF) was examined in regions of the medial prefrontal cortex (MPFC) with positron-emission tomography while subjects performed two cognitive tasks, reading nouns aloud and generating appropriate verbs for the same nouns. The control task was passive viewing of the same words. BF was reduced in regions of the MPFC during word reading and naive verb generation, relative to a control state in which the subjects passively viewed nouns. Practicing verb generation produced improved performance, as measured by response time, which was strongly correlated with further reductions in MPFC and hypothalamic BF. After practice, when verb generation was performed on a novel list of words, reaction times slowed and the pattern of MPFC BF reverted to that seen in the word reading and naive conditions. A separate behavioral study of the verb-generation task indicated that anxiety, high during naive use-generation as measured by heart rate and self-report, decreased with practice on the task but returned with the introduction of a novel list of words. Taken together, these results suggest that the MPFC is part of a network, including the hypothalamus and brainstem, whose activity reflects a dynamic interplay between cognitive task performance and emotion.