alpha-Actinin localization in the junctional complex of intestinal epithelial cells.

We have used antibody to chicken gizzard alpha-actinin to identify and localize this molecule in chicken intestinal epithelium. The antibody binds only to alpha-actinin when tested against a crude extract of chicken gizzard. Extracts of purified epithelial cells contain a molecule which has a subunit molecular weight of 100,000 on sodium dodecyl sulphate gels and which is able to inhibit the interaction of alpha-actinin antibody and 125I-labeled chicken gizzard alpha-actinin. By indirect immunofluorescence, alpha-actinin is localized in the apical portion of chicken intestinal epithelial cells. Ethanol-fixed cryostat sections of intestine taken through the apical portion of the epithelial cells and in a plane perpendicular to the long axis of the cells show that alpha-actinin is organized in a polygonal pattern which corresponds to the outlines of the polygonally packed epithelial cells. We interpret the data as indicating that alpha-actinin is a component of the tight junction (zonula occludens) and/or the belt desmosome (zonula adherens), both of which are membrane structures known to encircle the cell and to be confined to its apical portion.

Vinculin is a component of an extensive network of myofibril-sarcolemma attachment regions in cardiac muscle fibers.

Immunofluorescent staining of bovine and avian cardiac tissue with affinity-purified antibody to chicken gizzard vinculin reveals two new sites of vinculin reactivity. First, vinculin is organized at the sarcolemma in a striking array of rib-like bands, or costameres. The costameres encircle the cardiac muscle cell perpendicular to the long axis of the fiber and overlie the I bands of the immediately subjacent sarcomeres. The second new site of vinculin reactivity is found in bovine cardiocytes at tubular invaginations of the plasma membrane. The frequency and location of these invaginations correspond to the known frequency and distribution of the transverse tubular system in bovine atrial, ventricular, and Purkinje fibers. We do not detect tubular invaginations that stain with antivinculin in avian cardiocytes and, in fact, a transverse tubular system has not been found in avian cardiac fibers. Apparent lateral Z-line attachments to the sarcolemma and its invaginations have been observed in cardiac muscle by electron microscopy in the same regions where we find vinculin. On the basis of these previous ultrastructural findings and our published evidence for a physical connection between costameres and the underlying myofibrils in skeletal muscle, we interpret the immunofluorescence data of this study to mean that, in cardiac muscle, vinculin is a component of an extensive system of lateral attachment of myofibrils to the plasma membrane and its invaginations.

Elucidating dynamic brain interactions with across-subjects correlational analyses of positron emission tomographic data: the functional connectivity of the amygdala and orbitofrontal cortex during olfactory tasks.

Covariance analyses of positron emission tomography (PET) data are used increasingly to elucidate the functional connectivity between brain regions during different cognitive tasks. Functional connectivity may be estimated by examining the covariance between regions over time or across subjects. In functional brain-mapping studies, across-subjects covariance matrices derived from within-task (nonsubtracted) and between-task (subtracted) data characterize different, complementary aspects of functional interactions. The authors study amygdala-orbitofrontal interactions during three task conditions (aversive olfaction, odor detection, and resting with eyes closed) to illustrate the strengths and limitations of across-subjects covariance analyses based on subtracted and nonsubtracted data. This example underscores the dynamic nature of connectivity between the amygdalae and orbitofrontal cortices and highlights the importance of including data from resting conditions in covariance analyses.

Neural correlates of self-induced dysphoria.

OBJECTIVE: The authors explored the question of whether acute, transient changes in mood are reflected in activation of discrete neuronal systems in the human brain. METHOD: Using positron emission tomography, they measured the regional cerebral blood flow (CBF) of seven psychiatrically healthy subjects under two conditions. During the control condition the subjects were resting with their eyes closed. During the active condition, with their eyes still closed, they were asked to imagine or recall a situation that would make them feel very sad. They were explicitly asked to experience sadness and to avoid any feelings of anger or anxiety. RESULTS: There were significant differences in regional CBF measured during the control condition and during the active condition, particularly in the inferior and orbitofrontal cortices. Women showed bilateral inferior and orbitofrontal activation, but men displayed predominantly left-sided activation in these areas. CONCLUSIONS: The authors conclude that the inferior and orbitofrontal cortices play an important role in normal emotional cognitive processes.

Organization of working memory within the human prefrontal cortex: a PET study of self-ordered object working memory.

The prefrontal cortex plays a critical role in working memory, the active maintenance of information for brief periods of time for guiding future motor and cognitive processes. Two competing models have emerged to account for the growing human and non-human primate literature examining the functional neuroanatomy of working memory. One theory holds that the lateral frontal cortex plays a domain-specific role in working memory with the dorsolateral and ventrolateral cortical regions supporting working memory for spatial and non-spatial material, respectively. Alternatively, the lateral frontal cortex may play a process-specific role with the more dorsal regions becoming recruited whenever active manipulation or monitoring of information in working memory becomes necessary. Many working memory tasks do not allow for direct tests of these competing models. The present study used a novel self-ordered working memory task and positron emission tomography to identify whether dorsal or ventral lateral cortical areas are recruited during a working memory task that required extensive monitoring of non-spatial information held within working memory. We observed increased blood flow in the right dorsolateral, but not ventrolateral, prefrontal cortex. Increases in blood flow in the dorsolateral region correlated strongly with task performance. Thus, the results support the process-specific hypothesis.

Object and spatial alternation tasks with minimal delays activate the right anterior hippocampus proper in humans.

Substantial evidence indicates that the hippocampus plays a critical role in long-term declarative memory. In contrast, the role of the human hippocampus in working memory, particularly when information needs to be maintained only for a few seconds, remains controversial. Using PET, we show robust activation of the right anterior hippocampus proper during the performance of both object and spatial alternation tasks. Hippocampal activation emerged even though subjects only had to remember a single, simple stimulus over a minimum delay of 1 s. No hippocampal activation occurred when the delay was increased to 5 s. This suggests that the role of the hippocampus in working memory is not to maintain information across a delay interval. Instead, its activity reflects a more transient function during encoding and/or retrieval. These data are among the first observations to demonstrate human hippocampal involvement in working memory.

Human cortical gustatory areas: a review of functional neuroimaging data.

In an effort to define human cortical gustatory areas we reviewed functional neuroimaging data for which coordinates standardized in Talairach proportional space were available. We observed a wide distribution of peaks within the insula and parietal and frontal opercula, suggesting multiple gustatory regions within this cortical area. Multiple peaks also emerged in the orbitofrontal cortex. However, only two peaks, both in the right hemisphere, were observed in the caudolateral orbitofrontal cortex, the region likely homologous to the secondary taste area described in monkeys. Overall significantly more peaks originated from the right hemisphere suggesting asymmetrical cortical representation of taste favoring the right hemisphere.

Genetic and state variables of neurocognitive dysfunction in schizophrenia: a twin study.

To characterize the familiality of cognitive dysfunction in schizophrenia, we studied performance on three tasks (visuospatial attention; visuolinguistic conflict, arrow-word; and Wisconsin Card Sorting Test [WCST]) by monozygotic (MZ) and dizygotic (DZ) twin pairs discordant for schizophrenia. The subject sample consisted of six MZ twin pairs, nine DZ twin pairs, and one MZ and one DZ nonschizophrenia cotwin of a patient with schizophrenia. There were two sources of cognitive dysfunction: a nonheritable, state component and a heritable, trait component. Deficits surfaced during the WCST in nonschizophrenia MZ cotwins; this impairment resolved following training in nonschizophrenia MZ cotwins, but not in the probands with schizophrenia, who performed abnormally in all tasks. The results suggest that nonheritable protective factors modulate the specific, plastic, and sometimes subtle neurocognitive deficits related to the schizophrenia genotype.

PET study of the localization and laterality of lingual somatosensory processing in humans.

Regional cerebral blood flow (rCBF) was measured using positron emission tomography (PET) during four tasks in right-handed volunteers with eyes closed: resting, protruding the tongue, stroking the left side of the protruding tongue, and stroking the right side of the protruding tongue. The primary somatosensory tongue representation (S1) mapped to the contralateral central sulcus (Brodmann (BA) 3/4) at approximately 28 mm above the intercommissural plane. Of note, stimulation of the left side of the tongue produced also an ipsilateral S1 response. Analysis of variance (ANOVA) of rCBF at S1 across all four conditions yielded only a significant effect for tongue stimulation, with no effect of laterality; the usually large asymmetries (contralateral >> ipsilateral) in S1 did not surface. We hypothesize that this atypical activation pattern arises from the tongue's specialization for language.

Functional neuroimaging of the olfactory system in humans.

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have begun to provide unique information regarding the neural underpinnings of olfactory functioning in humans. We review the relative strengths and weaknesses of PET and fMRI techniques for studying olfaction. We then review PET and fMRI studies relating to the olfactory functions of the pyriform cortex, orbitofrontal cortex, amygdala and the entorhinal/hippocampal region. A pixelwise correlational analysis of PET data is also presented in order to clarify the relationship between blood flow in the medial temporal lobes and psychoperceptual variables.

Weight loss during chronic, cervical vagus nerve stimulation in depressed patients with obesity: an observation.

Fourteen patients were treated over 2 years with cervical vagus nerve stimulation (VNS) for adjunctive therapy of severe, treatment-resistant depression. Here, we report the serendipitous observation that this treatment was associated with highly significant, gradual weight loss despite the patients' report of not dieting or exercising. The weight loss was proportional to the initial BMI, that is, the more severe the obesity, the greater the weight loss. Weight loss did not correlate with changes in mood symptoms. The vagus nerve carries visceral information to and from the brain; modulation of its activity may alter eating behavior. Chronic cervical VNS may merit controlled study for the treatment of severe obesity.

Sex-related differences in amygdala functional connectivity during resting conditions.

Recent neuroimaging studies have established a sex-related hemispheric lateralization of amygdala involvement in memory for emotionally arousing material. Here, we examine the possibility that sex-related differences in amygdala involvement in memory for emotional material develop from differential patterns of amygdala functional connectivity evident in the resting brain. Seed voxel partial least square analyses of regional cerebral blood flow data revealed significant sex-related differences in amygdala functional connectivity during resting conditions. The right amygdala was associated with greater functional connectivity in men than in women. In contrast, the left amygdala was associated with greater functional connectivity in women than in men. Furthermore, the regions displaying stronger functional connectivity with the right amygdala in males (sensorimotor cortex, striatum, pulvinar) differed from those displaying stronger functional connectivity with the left amygdala in females (subgenual cortex, hypothalamus). These differences in functional connectivity at rest may link to sex-related differences in medical and psychiatric disorders.

Deficits in selective attention following bilateral anterior cingulotomy.

Abstract Positron emission tomographic (PET) studies of normal humans undergoing specific cognitive activation paradigms have identified a region of the anterior cingulate cortex as a component of an anterior, midline attentional system involved in high-level processing selection. However, deficits in attention have not been demonstrated in patients following bilateral anterior cingulotomy, a procedure that results in lesions of adjacent anterior cingulate cortex. Task paradigms used in PET studies that recruit the anterior cingulate cortex were applied to normal, control subjects and to a patient before and after cingulotomy to provide highly sensitive and functionally targeted reaction time measures of attentional performance. In contrast to unchanged performance in several neuropsychological measures, this patient demonstrated specific deficits in attention during the subacute postoperative period, which resolved spontaneously several months after surgery. Such impairment is consistent with the evolving view of the anterior cingulate's involvement in high-level processing selection. These data show the feasibility of using information from PET activation studies of normals in the design of novel chronometric tasks useful for probing abnormalities in specific cognitive operations associated with discrete cortical regions.

Emotion, olfaction, and the human amygdala: amygdala activation during aversive olfactory stimulation.

Electrophysiologic and lesion studies of animals increasingly implicate the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contributions of the amygdala and other limbic and paralimbic regions to emotional processing, we exposed healthy subjects to aversive olfactory stimuli while measuring regional cerebral blood flow (rCBF) with positron emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF within the left amygdala and the left OFC was highly intercorrelated, indicating a strong functional interaction between these brain regions. Furthermore, the activity within the left amygdala was associated significantly with subjective ratings of perceived aversiveness. These findings provide evidence that the human amygdala participates in the hedonic or emotional processing of olfactory stimuli.

Gamma actin, spectrin, and intermediate filament proteins colocalize with vinculin at costameres, myofibril-to-sarcolemma attachment sites.

Localization of vinculin at the sarcolemma of striated muscle fibers defines an orthogonal lattice. The costameres of the lattice are the riblike bands of vinculin that run perpendicular to the long axis of the fiber, repeat in register with I bands of the subjacent myofibrils, and seem to couple the myofibril to the sarcolemma [Pardo et al 1982, 1983a]. The colocalization studies presented in this paper show that gamma actin, spectrin, and intermediate filament antigens are additional components of this lattice of costameres. In addition, the results show that gamma actin and spectrin are also components of the internal network of collars, first visualized with antibody to desmin [Granger and Lazarides, 1978], that connects the myofibrils to each other at the level of the Z line.

Cortical activation induced by intraoral stimulation with water in humans.

Studies of gustatory processing frequently utilize water as a control stimulus. However, the neural representations of intraoral stimulation with water have received little attention. We report a series of positron emission tomography studies involving intraoral stimulation with deionized distilled water. Attempting to taste water produced large, bilateral activations in insular, opercular, Rolandic and cerebellar cortices relative to resting with eyes closed or 'smelling' odorless air. The magnitude and volume of activation was substantially reduced when tasting water was contrasted with voluntary swallowing. This indicates that much of the activity induced by water reflects intraoral somatosensory or motor processing. Nevertheless, portions of the insula, operculum, post-central gyrus and cerebellum remained significantly activated in the contrast between 'tasting' water and swallowing. This activity appears to represent a specific neural correlate of fluid stimulation, and may reflect aspects of trigeminal, gustatory or thermal coding. These findings emphasize the large volume of cortex dedicated to intraoral processing, and highlight the importance of controlling for nongustatory factors in studies of gustation.

The functional neuroanatomy of voluntary swallowing.

Swallowing is a complex physiological process involving voluntary and reflexive motor activity, sensorimotor integration, salivation, and visceral regulation. Despite the numerous processes required for normal deglutition, traditional models of the central control of swallowing only emphasize the involvement of the brainstem and the inferior precentral gyrus (IPCG). However a number of neurological disorders involving other brain regions also cause dysphagia. To determine the brain regions participating in voluntary swallowing, we assayed regional cerebral blood flow (rCBF) with positron emission tomography (PET) while healthy human subjects swallowed, performed lateral tongue movements, or rested with their eyes closed. Voluntary swallowing produced strong rCBF increases within the IPCG bilaterally, the right anterior insula/claustrum, and the left cerebellum. The maxima in these regions differed from those induced by lateral tongue movements. Swallowing also produced rCBF increases in the putamen, thalamus, and several additional cortical areas, but these foci were not as clearly distinguishable from activity arising during tongue movements. These findings indicate that swallowing involves the recruitment of a large-scale distributed neural network that includes the anterior insula and cerebellum. The distributed nature of this network helps to explain why so many neurological conditions produce dysphagia.

The role of the fusiform gyrus in successful encoding of face stimuli.

PET was used to measure regional cerebral blood flow (rCBF) while memorizing pictures of unfamiliar human faces presented one at a time (FaceMemory). Other conditions included: (1) FaceRepeat-memorization of four individual faces presented repeatedly; (2) FaceWatching-viewing passively single faces without overt memory demands; and (3) Scrambled-counting dots superimposed on pictures of scrambled faces. After each FaceMemory condition and after the final FaceWatching condition scan, recall was tested by measuring face recognition. Contrasting FaceMemory and Scrambled conditions revealed several temporal activations: right midfusiform and bilateral anterior fusiform gyri. Contrasting FaceWatching and Scrambled conditions showed bilateral activation in the temporal poles and in the anterior fusiform gyri. No hippocampal activation arose from any contrast. Region of interest analyses on the above areas showed correlations with performance: (1) only rCBF in the right midfusiform correlated positively with encoding during the FaceMemory and FaceWatching conditions; (2) in the right temporal polar cortex rCBF decreased during FaceMemory and correlated positively with performance, whereas rCBF increased during FaceWatching and correlated negatively with incidental performance; and (3) activity in the anterior fusiform gyri remained constant across the conditions of FaceMemory, FaceRepeat, FaceWatching, and Scrambled and was uncorrelated with performance. These data suggest an expanded mnemonic role for the right midfusiform in depth of processing/encoding of face information, temporal polar cortex in face perception and recognition, and anterior fusiform activity in featural visual feature processing.