Showing papers on "Temporal cortex published in 1984"

Stimulus-selective properties of inferior temporal neurons in the macaque

Abstract: Previous studies have reported that some neurons in the inferior temporal (IT) cortex respond selectively to highly specific complex objects. In the present study, we conducted the first systematic survey of the responses of IT neurons to both simple stimuli, such as edges and bars, and highly complex stimuli, such as models of flowers, snakes, hands, and faces. If a neuron responded to any of these stimuli, we attempted to isolate the critical stimulus features underlying the response. We found that many of the responsive neurons responded well to virtually every stimulus tested. The remaining, stimulus-selective cells were often selective along the dimensions of shape, color, or texture of a stimulus, and this selectivity was maintained throughout a large receptive field. Although most IT neurons do not appear to be “detectors” for complex objects, we did find a separate population of cells that responded selectively to faces. The responses of these cells were dependent on the configuration of specific face features, and their selectivity was maintained over changes in stimulus size and position. A particularly high incidence of such cells was found deep in the superior temporal sulcus. These results indicate that there may be specialized mechanisms for the analysis of faces in IT cortex.

Neurochemical characteristics of early and late onset types of Alzheimer's disease.

Abstract: Brains of 49 patients who had died with Alzheimer's disease and 54 controls were examined. The Alzheimer group exhibited noticeably reduced activity of the cholinergic marker enzyme choline acetyltransferase in the cerebral cortex, but cortical concentrations of noradrenaline, gamma-aminobutyric acid, and somatostatin were also significantly reduced. Analysis of the results according to age at death showed that the older patients, dying in their 9th and 10th decades, had a relatively pure cholinergic deficit confined to temporal lobe and hippocampus, together with a reduced concentration of somatostatin confined to temporal cortex. By contrast, the younger patients, dying in their 7th and 8th decades, had a widespread and severe cholinergic deficit together with the abnormalities of noradrenaline, gamma-aminobutyric acid, and somatostatin, and the younger patients accounted for most of the abnormalities in these systems observed in the overall group. Comparison of the young subjects with Alzheimer's disease with the older controls did not support the concept of Alzheimer's disease representing an acceleration of the aging process. These results suggest that Alzheimer's disease in people aged under 80 may represent a distinct form of presenile dementia which differs in important respects from the dementia of old age.

Neurones responsive to faces in the temporal cortex: studies of functional organization, sensitivity to identity and relation to perception.

Abstract: We have investigated the distribution of cells responsive to faces within the macaque temporal cortex and their sensitivity to different face attributes. We found a functional organization of cells responsive to the sight of different views of the head. Cells of a similar type were grouped together both vertically down through the cortex, and horizontally in patches extending 0.5-2.0 mm across the surface of the cortex. A substantial proportion of cells responsive to faces were found to be sensitive to biologically important characteristics such as identity or expression. Cells were found to be highly selective for particular individuals that were familiar to the monkey with selectivity persisting across a great variety of viewing conditions such as changing face expression, orientation, colour, distance and size. Data suggested that sensitivity to identity arises at the level of specific views of the individual (e.g. full face). Information about different views may then be pooled to allow recognition independent of view. Visual transformations that make it difficult for humans to perceive faces (e.g., contrast reversal, isoluminant colour, coarsely quantized images, rotation or inversion) reduced the magnitude or increased the latency of cells' responses to faces. In this way, cell responses were related to perception and not simply to visual qualities of the image.

Access to the posterior medial temporal lobe structures in the surgical treatment of temporal lobe epilepsy.

Abstract: The authors describe a surgical technique that allows access to the posterior temporal horn of the lateral ventricle with preservation of the most functional lateral temporal cortex. Development of the technique was stimulated by the need to resect posteromedial temporal lobe structures in patients with intractable complex partial epilepsy and well-identified unilateral posterior hippocampal foci. This technique has also been of value in the resection of some lateral ventricular and posteromedial temporal lobe masses. The operation consists of three steps. No more than 4.5 cm of the anterolateral temporal lobe is removed en bloc such that the most anterior aspect of the temporal horn is entered. An incision is carried from the floor of the temporal horn through the inferior longitudinal fasciculus to the middle fossa dura mater and posteriorally into the lateral ventricular atrium. The lateral temporal cortex and white matter are then elevated with a self-retaining retractor. This exposes the posteromedial temporal horn or intraaxial mass for excision or allows en bloc resection of the entire hippocampus and medial temporal lobe structures while preserving the functional association areas of the lateral temporal cortex, including speech and visual spatial function.

Temporal lobe lesions and perception of species-specific vocalizations by macaques.

Abstract: Japanese macaques were trained to discriminate two forms of their coo vocalization before and after unilateral and bilateral ablation of the temporal cortex. Unilateral ablation of the left superior temporal gyrus, including auditory cortex, resulted in an initial impairment in the discrimination, but similar unilateral ablation of the right superior temporal gyrus had no effect. Bilateral temporal lesions including auditory cortex completely abolished the ability of the animals to discriminate their coos. Neither unilateral nor bilateral ablation of cortex dorsal to and sparing the auditory cortex had any effect on the discrimination. The perception of species-specific vocalizations by Japanese macaques seems to be mediated by the temporal cortex, with the left hemisphere playing a predominant role.

NEURAL INPUTS INTO THE NUCLEUS BASALIS OF THE SUBSTANTIA INNOMINATA (Ch4) IN THE RHESUS MONKEY

Abstract: Neurons of the nucleus basalis-substantia innominata-nucleus of the ansa peduncularis complex (Ch4) provide the major source of cholinergic innervation for the entire neocortical surface. In contrast to their widespread projections to all parts of the neocortex, these neurons receive reciprocal projections from only very few cortical areas. Most of the sensory, motor, and association areas in the frontal, parietal, occipital and temporal lobes do not seem to project back to the Ch4 complex. The Ch4 neurons receive their cortical input from prepyriform cortex, orbitofrontal cortex, the anterior insula, the temporal pole, entorhinal cortex and the medial temporal cortex. There are also subcortical inputs from septal nuclei, the nucleus accumbens-ventral pallidum complex and the hypothalamus. This organization suggests that the Ch4 complex is in a position to act as a cholinergic relay for transmitting predominantly limbic and paralimbic information to the neocortical surface. It would also appear that the cortical areas which do not project into Ch4 have no direct way of controlling the cholinergic input which they receive, whereas the limited set of cortical areas which do project into Ch4 can control not only the cholinergic innervation that they receive but also the cholinergic innervation into the entire neocortical mantle.

Direct connections of rat visual cortex with sensory, motor, and association cortices

Abstract: Each division of rat visual cortex, areas 17, 18a, and 18b, has connections with sensory, motor, and association cortices. These corticocortical connections were sampled using anterograde autoradiographic and retrograde horseradish peroxidase labeling techniques. Area 17 is connected via reciprocal pathways with each division of visual cortex, the posterior one-third of motor area 8, association area 7, and posteroventral area 36 of temporal cortex. It also receives projections from perirhinal areas 13 and 35. Area 18a has reciprocal connections with areas 17 and 18b, a patch in posterior somatosensory area 3, and dorsal auditory area 41. Like area 17, area 18a receives afferents from and projects to the posterior one-third of motor area 8. The connections of area 18a with association cortices are extensive; these regions include parietal areas 7, 39, 40, and 14, posteroventral and dorsal area 36, and perirhinal cortex. Area 18b is connected with areas 17 and 18a, a patch in medial area 3, and dorsal area 41. There are reciprocal projections between area 18b and posterior area 8. As for association cortex, area 18b projects to frontal area 11, area 7, posteroventral and dorsal area 36, and perirhinal cortex. In addition, area 18b receives input from and projects efferents to the dorsal claustrum. Most of the interconnections among areas 17, 18a, and 18b originate from neurons in layers II, III, and V and end in terminal fields in layers I–III and V. In contrast, projections of other sensory, motor, and association cortices to visual cortex originate mainly from neurons in layer V and to a lesser extent from layer II. The reciprocal pathways from visual cortex terminate predominantly in the supragranular layers. In conclusion, these corticocortical pathways provide the basis for cortical visuosensory and visuomotor integration that may aid the rat in the coordination of visually guided behaviors.

Further observations on parieto-temporal connections in the rhesus monkey.

Abstract: The origin, course, and termination of parieto-temporal connections in the rhesus monkey were studied by autoradiographic techniques. The caudal third of the inferior parietal lobule (including the adjacent lower bank of the intraparietal sulcus) is the chief source of these projections. It projects to three separate architectonic areas in the superior temporal sulcus and to three different areas on the ventral surface of the temporal lobe: the parahippocampal gyrus, presubiculum, and perirhinal cortex. The mid-inferior parietal lobule and medial surface of the parietal lobe, by contrast, project only to the caudal upper bank of the superior temporal sulcus. The rostral inferior parietal lobule and the superior parietal lobule, as well as the postcentral gyrus and rostral parietal operculum, do not project to the temporal lobe. Fibers travel from the posterior parietal region to temporal cortex by way of several different routes. One fiber bundle courses in the superior temporal gyrus and terminates in the superior temporal sulcus. Another proceeds ventrally, between the depth of the superior temporal sulcus and the geniculocalcarine tract, to the parahippocampal area. A separate bundle, coursing part of the way in the company of the cingulum bundle, conveys posterior parietal fibers to the presubiculum.

Serotonin receptor changes in dementia of the Alzheimer type.

Abstract: Serotonin receptors were assessed in post-mortem brains of control and Alzheimer-type dementia (ATD) patients using ligand binding techniques. Differential losses of serotonin S1 and S2 receptors were present in neocortex, hippocampus, and amygdala of ATD patients, whereas no significant changes were observed in basal forebrain and basal ganglia. Losses of S1 receptors were significantly age-related in the ATD group, suggesting they occurred at a later stage of the disease process. Losses of S2 receptors were considerably greater (with a reduction to 35% of control in temporal cortex) and were not age-related in ATD. Significant correlations were observed within the ATD group between S2 receptor binding and somatostatin immunoreactivity in temporal and frontal cortices. Thus the loss of S2 receptors in ATD may be a relatively early change in the disease process, and may precede the changes in ascending serotonergic neurones.

Monkeys with combined amygdalo-hippocampal lesions succeed in object discrimination learning despite 24-hour intertrial intervals.

Abstract: Monkeys with combined amygdalo-hippocampal removal show severe impairments on visual memory tasks after delays of only a minute or two, yet they learn visual discrimination habits about as quickly as normal animals with intertrial intervals of the same duration. In an attempt to resolve this discrepancy between abnormally rapid forgetting and successful retention, tests were conducted to determine whether discrimination learning would be prevented in animals with limbic lesions if intertrial intervals lasted 24 hr. The results showed that as long as the lesion did not encroach on inferior temporal cortex, the operated animals could acquire concurrent sets of 20 object discrimination habits at the same rate as normal animals, in an average of about 10 trials per set. The findings suggest that learning and retention processes are divisible into a mechanism for memory formation that is dependent on the limbic system and a mechanism for habit formation that is not.

Biochemical effects and drug levels in rats after long-term treatment with the specific 5-HT-uptake inhibitor, citalopram.

Abstract: The effects in rats of long-term administration of the potent, specific 5-HT uptake inhibitor citalopram have been investigated. Citalopram hydrobromide (MW=405) was given in the diet, 99 or 25 μmol/kg daily, for 13 days or orally, 49 μmol/kg twice a day, for 14 days. High plasma and brain levels of citalopram were found during the treatment period, whereas negligible amounts were found 24 h after withdrawal. The 5-HT uptake mechanism in blood platelets was completely blocked, since levels of whole blood 5-HT during and shortly (2 days) after treatment were decreased by 75–90%. The drug load after the two highest doses in terms of plasma drug levels was the same as in depressed patients treated with citalopram. Receptor binding technique ex vivo was applied to different brain parts to measure receptor parameters for several neurotransmitters. All data were evaluated by Eadie-Hoffstee analysis. No changes were seen in B max and K d for β-receptors (3H-dihydroalprenolol) in frontal cortex, occipital+temporal cortex, whole cortex and limbic structures, 5-HT2 receptors (3H-spiroperidol) in frontal and whole cortex, α1-receptors (3H-prazosin) in “rest of brain” and DA D-2 receptors (3H-spiroperidol) in corpus striatum and limbic structures. The uptake mechanism for 5-HT as well as the inhibitory effect of citalopram on this uptake remained unaffected in brain synaptosomes derived from control and from citalopram (99 μmol/kg)-treated rats. Thus long-term treatment with citalopram does not induce changes in neurotransmitter receptors as seen with most tricyclic as well as newer “atypical” antidepressants. Most striking is the lack of β- and 5-HT2 receptor down-regulation. Since citalopram clinically shows clear antidepressant activity, this down-regulation does not seem to be a prerequisite of antidepressant activity.

Intracellular study of human epileptic cortex: in vitro maintenance of epileptiform activity?

Abstract: Intracellular recordings were obtained in the vitro slice preparation from neurons of lateral and mesial temporal cortex removed from human epileptics suffering from intractable temporal lobe seizures. Spontaneous rhythmic synaptic events, which were capable of triggering action potential discharge, were observed in many neurons, particularly in mesial tissue slices. Such activity may reflect the epileptogenic capacity of this human cortex.

Cortical connections of the middle temporal visual area (MT) and the superior temporal cortex in owl monkeys.

Abstract: The connections of the middle temporal visual area (MT) and an adjoining superior temporal visual region (ST) were investigated with injections of 3H-proline and horseradish peroxidase (HRP) in adult owl monkeys. Injections in MT revealed an extensive pattern of intrinsic connections that appeared to be organized in a series of bands across MT. MT was found to project ipsilaterally to an array of visual areas including the first (V I) and second (V II) visual areas, the dorsolateral visual area (DL), and the dorso-medial visual area (DM). When injection sites and projection zones were related to previously described retinotopic maps, it was apparent that the projections of MT to these fields were largely homotopic. Other projections were to posterior parietal cortex, the dorsointermediate visual area (DI), the ventral visual area (V), and possibly the medial visual area (M). In addition, dense projections to cortex on the rostral border of MT were used to define a new subdivision of visual cortex, the superior temporal visual region (ST), as the major projection zone of MT. Callosal connections of MT were mainly to MT, with some terminations in DL and ST. Injections of 3H-proline into ST revealed a diffuse projection to largely layer I of MT, and dense projections to posterior parietal cortex, cortex in more rostral parts of the superior temporal sulcus, ventromedial inferior temporal cortex, and the region of the frontal eye fields. Callosal projections were largely to ST cortex of the other cerebral hemisphere. The results place MT and V II in distinctly different processing chains. While both MT and V II receive the major cortical outputs of V I, V II relays to DL and DL relays to subdivisions of inferior temporal cortex. In contrast, the most significant cortical target of MT appears to be to ST, which relays to posterior parietal cortex and other targets.

Cortical connections of area 17 in tree shrews.

Abstract: In order to better understand the organization of extrastriate cortex in tree shrews, injections in area 17 of wheat germ agglutinin or tritiated proline were used to reveal an intrinsic pattern of connections, ipsilateral connections with area 18 and two other subdivisions of cortex, and callosal connections with areas 17 and 18 of the opposite cerebral hemisphere. Areal patterns of connections were best seen in sections cut parallel to the surface of flattened cortex. Within area 17, periodic foci of labeled terminations and cells extended from and surrounded injection sites as described by Rockland et al. ('82). Single injections produced multiple foci of labeled terminations and cells in area 18. The foci tended to fuse into short bands that sometimes crossed the width of area 18. Double injections produced more foci, and multiple injections tended to produce more continuous regions of label. An overall retinotopic pattern was evident with rostral area 17 connected to rostral area 18 and caudal area 17 connected to caudal area 18. Terminations extended through layers II-VI, with some increase in density in layer IV. Cells in area 18 projecting back to area 17 were in layers III and V. The injections also allowed identification of previously undefined subdivisions of visual cortex in temporal cortex immediately adjoining area 18. Dense reciprocal connections were observed in a 13 mm2 oval of cortex on the lateral border of the middle section of area 18 that we define as the temporal dorsal area, TD. Connections indicate a crude topographic organization with lower field represented rostrally and upper field caudally. Inputs were most dense in the middle cortical layers, and labeled cells were supragranular, and less frequently, infragranular. A 10-mm2 oval of cortex near the posterior edge of the hemisphere, the temporal posterior area (TP), contained labeled cells after area 17 injections, but terminal labeling was only obvious in the dorsal part. Single injections sometimes produced quite separate dorsal and ventral zones of label in TP, suggesting a small separate dorsal division. A crude retinotopic order appears to exist within ventral TP, with the lower field most ventral. Labeled cells were largely supragranular. A fourth zone of ipsilateral connections was in posterior limbic cortex bordering area 17 on the ventromedial surface of the cerebral hemisphere. The callosal connections were reciprocal and included regions 1 mm wide on either side of the area 17 and area 18 border. Callosal connections were rougly homotopic. Callosal terminations included superficial layers, and projecting cells were both supragranular and infragranular.(ABSTRACT TRUNCATED AT 400 WORDS)

Transient projections from the fronto-parietal and temporal cortex to areas 17, 18 and 19 in the kitten.

Abstract: Using the retrograde tracers, fast blue and horseradish peroxidase we have shown the presence of projections from extensive regions of the frontoparietal and temporal cortex to areas 17, 18 and 19 in the newborn kitten. These projections are transitory as they do not exist in the adult cat. The anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin after injections in frontoparietal and temporal cortex revealed that these transitory projections terminate in the gray matter and that they could therefore play a functional role in the development of the visual cortex.

Regional and cortical laminar distributions of serotonin S2, benzodiazepine, muscarinic, and dopamine D2 receptors in human brain.

Abstract: Serotonin S2, benzodiazepine, and muscarinic receptors showed different regional distributions in the human brain but were present in all cortical areas. The laminar distributions of [3H]ketanserin, [3H]diazepam, and [3H]quinuclidinylbenzilate were investigated in the temporal cortex and revealed a high density in the IIIrd and IVth layers. Dopamine D2 receptors were not detected in the cortex.

Anatomical and physiological correlates of visual computation from striate to infero-temporal cortex

Abstract: The calculus of two-dimensional mappings is reviewed. Currently available data suggests that a conformal (isotropic) mapping is sufficient to model the global topography of primate striate cortex. The addition of a shear component to this mapping is outlined. A similar analysis is applied to the local map structure of striate cortex. Models based on a local reiteration of the complex logarithm and on Radon (and backprojection) mappings are presented. A variety of computational functions associated with the novel architectures for image processing suggested by striate cortex neuroanatomy are discussed. Applications to segmentation, perceptual invariances, shape analysis, and visual data compression are included. Finally, recent experimental results on shape analysis by neurons of infero-temporal cortex are presented.

CT-CBF correlations of cognitive deficits in multi-infarct dementia.

Abstract: Fifteen right-handed patients with Multi-Infarct Dementia underwent cognitive testing by the Jacobs Mini-Mental Scale (MMQ), and xenon contrast CT scanning. Local cerebral blood flow (LCBF) and local partition coefficient (L lambda) values were measured by stable xenon contrast CT scanning and potential methodological errors were discussed. Reduced values were graded: 0 = normal, 1 = mild, 2 = moderate, 3 = severe. Graded values were pooled and plotted on composite brain maps to display locations of abnormal L lambda and LCBF values. Topographic brain maps, showing most frequent locations of reduced L lambda values, confirmed the common anatomical locations of multiple cerebral infarcts to be distributed in both thalami, temporal lobes, basal ganglia, left internal capsule and right cingulate cortex. Gray matter flow values were reduced in similar cortical and subcortical regions. There were no correlations between MMQ scores and reduced LCBF values for caudate and lenticular nuclei. Direct and statistically significant correlations were found between reduced MMQ scores and mean LCBF values for left or right frontal cortex, left or right temporal cortex and left or right thalamus. Subgrouping MMQ tests according to functions assessed, indicated that left mid-temporal ischemia correlated with dyscalculia and memory disturbances while ischemia of both frontal lobes correlated with disorientation to time and place.

Positron emission tomographic studies of perceptual tasks.

Abstract: Metabolic mapping in conjunction with positron emission tomography was used to examine the response of the human brain to physiological stimuli. Local cerebral glucose consumption was measured by means of the fluorine-18-labeled fluorodeoxyglucose technique. The coefficient of variation of this measurement for various gray matter structures varies from 19.5 to 26.4%. If repeat measurements are made in the same subject using carbon-11-labeled deoxyglucose as the tracer, the coefficient of variation of repeat measurements for these same structures is reduced to between 5.2 and 8.7%. Stimulation of one visual field in normal subjects produced a significant (p less than 0.01) increase in metabolism in the contralateral visual cortex. An auditory stimulus consisting of a tape-recorded factual story presented through earphones to only one ear produced a significant (p less than 0.001) increase in glucose consumption in the contralateral temporal cortex. The effects of vigilance or attention on cerebral metabolism were also examined. There was significantly greater metabolism in the right versus the left inferior parietal region in subjects attending to a visual or auditory task compared with those who were not. Anxiety appeared to produce significantly greater glucose utilization in the right hemisphere compared with the left in those subjects who had a higher level of anxiety during the measurement. Metabolic mapping promises to be a powerful new tool in furthering our understanding of the organization and functioning of the human brain.

A study of somatostatin receptors in amygdaloid-kindled rat brain.

Abstract: Kindling is an animal model of epilepsy. Previously somatostatin (SRIF) was implicated in seizure activity in the brain. Recently we reported a significant increase in brain SRIF content in the temporal cortices and cortices of kindled rats. Since the interaction between the neurotransmitter and the receptor eventually is responsible for the biological response, the present study was undertaken to examine evidence for the participation of SRIF receptor in the kindled state. In this study we present a procedure for detection of SRIF receptors using radiolabeled (D-Tyr8)-SRIF as a tracer. The present study indicates that in kindled rats there are no differences in the total number or affinity of the binding sites in the temporal cortex and a slight increase in the total number of binding sites in the cortex when compared with controls. These results, in view of our other observations, suggest that in kindled rat brain there may be an increased release of SRIF but no down-regulation of SRIF receptors in temporal cortex and cortex. There appears to be a significant decrease in the number of SRIF receptors in kindled hippocampus. The mechanism by which this occurs remains unclear.

Basic science and clinical aspects of procaine HCl as a limbic system excitant.

Abstract: The literature in animals and humans which indicate that systemic procaine HCl activates limbic tissue is reviewed. Studies in cats which suggest that procaine excites limbic cells by reducing neural inhibition are then described. Evidence that power spectral analysis of high frequency EEG bands (omega or 31-55 cps) in the temporal cortical EEG reflects degree of limbic (amygdala) excitation in animals and humans is reviewed. Studies in cats are described which show that procaine selectively increases omega band activity in the amygdala and temporal cortex in a dose related fashion which parallels dose related increases in amygdaloid neural activity. Preliminary results of combining intravenous procaine and omega band analysis of scalp EEG in humans to predict therapeutic response to carbamazepine in borderline personality and affective disorder patients are then described. The effects of procaine on omega are compared to the effects of direct electrical stimulation of human limbic system in complex partial seizure patients undergoing assessment for temporal lobectomy. The results tentatively support the hypothesis that some psychiatric patients have hyperexcitable limbic systems, and those that do, show a positive behavioural response to carbamazepine.

Ganglioside pattern of normal human brain, from samples obtained at surgery. A study especially referred to alkali labile species

Abstract: The ganglioside pattern from normal human temporal cortex and cerebellum has been studied in fresh specimens obtained at surgery. The analyses have been performed by two-dimensional thin layer chromatography with an intermediate ammonia treatment which is a methodology particularly suitable for resolving alkali labile gangliosides. Alkali labile gangliosides were detected in all the analyzed specimens and their content contributed to 23% and 11% of total lipid bound sialic acid, in temporal cortex and cerebellum, respectively.

Stimulus equivalence after inferior temporal lesions in monkeys

Abstract: Monkeys with inferior temporal cortex lesions and unoperated monkeys were trained to discriminate pairs of objects and then tested for transfer after the original discriminanda were made larger or smaller, rotated, or presented as two-dimensional projections The two groups of monkeys transferred equally well to the discriminanda altered in size or orientation, but only the unoperated animals transferred to the two-dimensional representation

Transplantation of human cortex with Alzheimer's disease into rat occipital cortex; a model for the study of Alzheimer disease

Abstract: Senile dementia of the Alzheimer type (SDAT) is a major problem in the human senescent population. As this pathology cannot be reproduced in animals, research into its development is greatly impeded. The technique of implantation of the nervous tissue has been utilized in order to establish an animal model and to test the possible existence of a transmissible agent. When human temporal cortex with Alzheimer's disease is implanted in the occipital cortex of 7-week-old rats, human cerebral tissue containing abundant tangles induces in the receiver cortex a reactive fibrous gliosis. In the processes of the astrocytes, twisted filaments are evident among bundles of normal filaments. These alterations could be induced by the metabolising of abnormal filament subunits or by some infectious agent introduced by the implant.

Vitamin content of some normal human brain segments.

Abstract: Nicotinates, pantothenates, riboflavin, vitamins B6 and B12' free (acetyl) and total (free and bound) choline, biopterin, thiamin, biotin, methylated and nonmethylated folates in frontal, temporal, precentral, postcentral, and occipital cortex, thalamus, cerebellum, pons, basal ganglia, and substantia nigra were estimated. Nicotinates are significantly more concentrated in basal ganglia and thalamus than pons. Nonmethylated folate content is not significantly varied in brain segments; the pons contains more methylated folate. Riboflavin content is higher in the basal ganglia and temporal cortex than frontal cortex. Biotin is concentrated in pons and basal ganglia. Thiamin concentration is less in the postcentral cortex than the thalamus and substantia nigra. Biopterin is significantly higher in substantia nigra and basal ganglia than the other brain segments. Total choline content is high in substantia nigra, pons, and thalamus; free (acetyl) choline is significantly elevated in basal ganglia. B12 content is less concentrated in the cortex segments. B6 is highly concentrated in the basal ganglia. Pantothenate content is elevated in pons when compared to the various cortex segments and cerebellum.