Area Si Research Articles

A method of neuronal spike train study based on autoregressive analysis

The method of autoregressive (AR) analysis for neuronal spike trains (NST) is proposed in the paper. The AR model and the Green's function as well as the power spectral density function are used to process and analyse the neuronal interspike interval (ISI) sequences of cat's first somatosensory area of cortex (SI area) under various situations. With these methods the characteristics of the ISI sequence such as the AR order and parameters, memory property, correlativity and periodicity etc. can be extracted.

Will ASIC Technology Demand a New Interconnection Technology instead of Soldering in Automotive Electronics?

Automotive electronics, after 1995, will be similar to aerospace electronics because there is a demand for low weight and volume together with very high speed and ultra‐high reliability. What is different is that automotive electronics must achieve all those properties at very low cost. It will be shown that when using ASIC chips the chip area is determined by the number of pins instead of the number of components of the active circuit. As ASIC technology proceeds towards line widths in the submicrometre range, the ratio of active Si area to total chip area is becoming much less than 1. This means that on the ASIC chip there is Si area which is ‘empty’. This ‘empty’ Si area can be used for designing self‐test circuits and redundant functions on the ASIC chip at a cost penalty slightly higher than the design cost. It will also be shown that these ASICs can work in the order of 100 MHz at the chip level. Such ASIC chips will therefore have a very high reliability at the chip level due to the inherent properties of the Si and the built‐in redundancy. At the same time they can work at very high speed. From a performance point of view the best solution should be a highly miniaturised packaging technology. With self‐test circuits on the chip, there is a good correlation between wafer test and final test. Therefore, from an economical point of view, working with chips will then have an economical advantage compared with working with packaged circuits. From a reliability point of view it will be shown that the solder joints are the limiting factor. A critical review is presented of the reliability problems plaguing the SMD and soldering technology of today. It will be shown that, if SMD technology is to meet the reliability demands in a future automotive environment, it will have to have solder joint failure rates better than 30 ppm over the life, 17 years, in automotive applications. The conclusion is that a multi‐ASIC chip approach has the best potential as the solution for the future, post 1995, automotive electronics, provided there is a highly reliable chip interconnection technology available at that time.

Mask-size dependence of lattice defects generated by B- and As-implantation into submicron Si areas

Cross-sectional transmission electron microscopy observations have been carried out to clarify two-dimensional depth distributions of secondary defects generated in 100 keV B- and 80 keV As-implanted and annealed Si through fine mask patterns with dimensions ranging from 0.3 to 3.5 μ. When implanted layers are amorphized, neither defect distributions nor densities show a mask-size dependence. In this case, if amorphous shapes under the mask edge are of the teardrop type, defects composed of dislocation lines are generated as a result of the complicated recovery process of mask-edge amorphous layers. When no amorphous formation occurs, defect distribution and densities vary from one implanted layer to another for mask sizes below 0.5 (μm after high-temperature annealing e.g. at 1000 °C. These results match those for 70 keV focused B ion-beam implantation with a 0.2-μm beam diameter.

Vagal afferents and EEG rhythms in the SI area in anesthetized cats : similarities between responses to electrical and chemical (phenyldiguanide) stimulations

In anesthetized, artificially ventilated cats with open chest, bilateral stimulation of all afferent vagal fibres (pulse duration: 800 microseconds, 30 Hz, train duration 30 to 40 s) produced marked changes in the spontaneous EEG activities in the primary somatosensory cortex (Sl area). They were characterized by depressed background rhythms, with a tendency to desynchronization, decreased amplitude and number of spindles, with altered pattern, and/or evoked sustained fast rhythmic activities. These effects occurred within 1 to 5 sec during vagal stimulation. On the contrary, the EEG response was weaker or absent when only myelinated vagal afferents were stimulated (100 microseconds). I.v. injection of phenyldiguanide (PDG), used for stimulation of unmyelinated vagal sensory fibres and mainly of pulmonary afferents, induced EEG changes within the first 30 s, similar to those observed during electrical vagal stimulation. These EEG responses were unrelated to the induced hypotension. Cervical bivagotomy produced persistent changes in EEG activity, with enhancement of the magnitude, duration and number of spindles, which resembled the delayed effects induced by PDG. The present results obtained with three test agents (electrical or chemical vagal stimulation and bivagotomy) demonstrated that, in cats, vagal afferent information interacted with the spontaneous EEG rhythms in the Sl area.

Characteristics of the tooth pulp-driven neurons in a functional column of the cat's somatosensory cortex (SI).

The columnar arrangement of tooth pulp-driven (TPD) neurons in the first somatosensory cortex (SI) was studied by single unit analysis in the cat anesthetized with nitrous oxide and halothane. Tactile sensitive neurons in the oral area of SI were arranged functionally in a columnar organization. About 32% of the recorded neurons also responded to tooth pulp stimulation. Thus, the TPD neurons located in area 3b seem to be multireceptive in sensory modality. About 80% of the TPD neurons were F-type which respond with a short latency to tooth pulp stimulation and receive input from a small number of teeth. When a microelectrode penetrated through a single vertical column, most of the F-type TPD neurons encountered received common input from one or two tooth pulps. However, when an electrode was inserted across more than one column, there was no common pulpal input to the TPD neurons encountered in a track. Thus, the TPD neurons in a single column had identical peripheral and pulpal receptive fields, and the same latency of responses to tooth pulp stimulation. These characteristics would support the hypothesis that TPD (presumed nociceptive) neurons are arranged in a vertical column and it may be inferred that the columnar organization of TPD neurons in SI plays an important role in the sensory-discriminative aspects of pulpal pain.

Lattice Defects Generated by Ion Implantation into Submicron Si Areas

AbstractCross-sectional transmission electron microscopy observations have been carried out to clarify two-dimensional depth distributions of lattice defects generated in high-dose (5 x 1015 ions/cm2 ), P, As, BF2 and B implanted, annealed submicron Si areas as a function of implantation areas. Monte Carlo simulation is also adapted for ion-implantation into submicron Si through fine mask patterns to predict the effect of mask size on spatial damage and impurity profiles. Simulation results predict that the above profiles have a strong mask size dependence for regions below the critical size, where the dopant concentration decreases and damage depth moves toward the surface-side with a reduced implantation area. Some experimental results support simulation results, although most defects, mainly in the P and As implantation, are confined within the original amorphized layers, independent of mask size. However, in BF2 and B implantation, unexpected defect behavior such as variations in defect distribution from one implanted layer to another is found to occur in submicron regions doped by implantation.

Lattice Defects in High-Dose As Implantation into Localized Si Area

Cross-sectional transmission electron microscopy observations have been carried out to clarify two-dimensional depth distributions of lattice defects generated in high-dose (5×1015 and 2×1016 ions/cm2), 80 and 150 keV As-implanted, and annealed Si through 1.0 and 1.5 µm windows on (100) Si. Amorphous Si (a-Si) layer thicknesses formed by implantation range between projected range, Rp, +(5∼6) standards deviation, ΔRp, with a lateral spread of about 0.18 times a-Si thickness under the mask edge. Typical post-annealed, induced defects in such amorphous layers are mask edge defects composed of dislocation lines caused by a complicated process for recovering mask edge amorphous layers, together with commonly observed dislocation loops in high-dose As implantation. Interaction between dislocation loops and knocked-on oxygen atoms is discussed, particularly concerning the elimination or survival of As-rich precipitate-induced dislocation loops.

Optical imaging of neuronal activity.

Optical imaging of neuronal activity.

Organization of transient projections from the primary somatosensory cortex to the cerebellar nuclei in kittens

The organization of transient projections from the primary somatosensory cortex (SI) to the cerebellar nuclei was studied in neonatal cats. Tritiated amino acids were injected into the face, forelimb, or hindlimb areas of SI in 4 to 6-day-old kittens. The animals were killed 3 to 6 days later and their brains processed for autoradiography. Labeled axons were found bilaterally in the cerebellar nuclei, but, although the distribution of label was similar on both sides, the label was always much denser on the side of the injection. Each area of SI demonstrated a characteristic pattern of projection to the cerebellar nuclei. Neurons in the hindlimb area projected to the rostral part of the anterior interpositus nucleus, the caudal part of the posterior interpositus nucleus, and the medial quadrant of the dentate nucleus. Fibers from the forelimb area were directed to the caudal part of the anterior interpositus and the rostral part of the posterior interpositus. Projections from the face area terminated principally in the caudal pole of the posterior interpositus. A small transitional area between the interpositus and fastigial nuclei was labeled with all injections. These data indicate that transient neocortical projections to the deep nuclei are organized and that the somatotopy of these projections is similar to that of other cerebellar nuclear connections.

Influence of the ipsilateral hemisphere upon somatosensory evoked potential in cats.

Somatosensory evoked potentials (SEPs) were recorded on the skull corresponding to the (left) SI area by (right) superficial radial nerve stimulation. Amongst the various components of the SEP, special attention was directed to the negative component (N15) with a latency of approximately 15 ms. Changes in this potential followed by conditioning stimulation of the ipsilateral (right) hemisphere were observed and the following results were obtained: (i) when conditioning stimuli were applied to the contralateral (left) superficial radial nerve, the ipsilateral (right) thalamic VPL nucleus and the ipsilateral (right) sensory cortex, the amplitude of N15 decreased to 65-80% of the control level at C-T intervals less than 100 ms and (ii) following functional elimination of the unilateral sensory cortex by KCl application, the amplitude of N15 recorded at the opposite side significantly increased. In this condition, the inhibitory effects of the ipsilateral thalamus and contralateral peripheral nerve disappeared. From these observations, ipsilateral homologous cortex may well have an inhibitory influence upon the near field potential (N15) of the SEP.

Topical application of morphine to the rat somatosensory cortex produces analgesia to tonic pain.

Topical application of 0.01 or 0.1% morphine solution to the somatosensory SI area of the rat cerebral cortex significantly decreased the pain intensity rating in the formalin test without producing motor side effects or sensory deficits. Naloxone partially antagonizes this effect. Topical application of morphine to the striate cortex did not induce analgesia. It is suggested that the primary somatosensory SI area of the cerebral cortex plays a role in opiate pain control.

Photoluminescence studies of selective-area molecular beam epitaxy of GaAs film on Si substrate

GaAs films have been grown on Si substrates patterned with SiN by molecular beam epitaxy. The pattern consists of bare Si stripe of width ranging from 10 to 100 μm surrounded by SiN on both sides and a reference area of bare Si. 77 K photoluminescence (PL) spectrum and intensity are measured on the single crystalline GaAs films grown on these stripes and the reference area. For 1.5- and 3-μm-thick films, PL intensity from the 10 μm stripe shows 140% and 75% increase over the reference area, respectively. This remarkable increase in the PL intensity is believed due to the reduction of dislocations inside the window area. The improvement in the optical quality makes selective-area molecular beam epitaxy a very attractive technique for the fabrication of optical devices on Si substrate.

The Photoluminescence and TEM Studies of Patterned GaAs films on Si Substrate Grown by Molecular Beam Epitaxy

AbstractPatterned epitaxial GaAs films have been formed on Si substrates by either growth over patterned substrate (selective -area epitaxy) or chemical etching of patterns after growth. The optical properties of these samples are studied by 77K photoluminescence (PL) and the defect structures are investigated by transmission electron microscope (TEM). The patterned substrate consisted of bare Si stripes with width ranging from 10 µm to 100 µm surrounded by Si3N4 films on both sides and a reference area of bare Si. For 1.5 µmiann d 3 µm thick films, PL intensities from the films inside the 10 µm stripe shows 140% and 75% increase over unpatterned areas while the residual tensile stress in the patterned films is very similar to that of the unpatterned area. The increase in the photoluminescence intensity is ascribed to the reduction of crystalline defects inside the the window area. In the chemically etched sample, the pattern consisted of 4 µm by 4 µm squares and 1 mm long stripes with widths ranging from 100 µm to 4 plm. From the shift of PL peaks, a monotonic decrease in the tensile stress versus stripe width is observed. In particular, when the width of the stripe is less than 7 µm. tensile stress becomes essentially uniaxial in agreement with the results obtained by Yacobi et al [16] on a GaAs on InP sample. The polarization of the luminescence spectra parallel and perpendicular to the uniaxial stress of a 4 µm wide stripe agrees well with theoretical prediction. It is also observed that tensile stress is almost completely relieved in the 4 µm by 4 muentc hed squares.

Thalamic and corticocortical connections of the second somatic sensory area of the mouse.

Thalamic and corticocortical connections of the second somatic sensory area (SII) in the mouse cerebral cortex were investigated by means of the retrograde transport of horseradish peroxidase. Focal injections of the enzyme were made in physiologically determined locations within the parietal cortex. Results show that SII receives substantial inputs from topographically appropriate regions within the ipsilateral ventrobasal nucleus and from the ipsilateral posterior group. The limb representation, which was previously found to be responsive to auditory stimulation, received inputs also from the medial division of the medial geniculate body. The SII face representation, which is largely unresponsive to auditory stimuli, received little or no input from the medial geniculate body. SII injections yielded retrograde labeling in the topographically appropriate region in the first somatic sensory area (SI), and SI injections retrogradely labeled cells in SII in a pattern consistent with previous electrophysiological maps. Homotypical regions within SI and SII therefore appear to be reciprocally interconnected. SII also receives inputs from the ipsilateral motor cortex and from contralateral SI and SII. Finally, injections into the SI paw but not face regions yielded retrograde labeling in the thalamic ventrolateral nucleus. Thus, the distal limb representations in SI and SII each receive inputs from a third major relay nucleus (i.e., medial geniculate to SII, ventrolateral nucleus to SI) whereas the face representations do not. These results indicate a close functional interrelationship between homotypical areas in SI and SII, though the two areas differ in several important respects. It is proposed that SII in mice may complement the function of SI by helping to define the overall sensory context in which detailed tactile discriminations are made.

An experimental investigation of the parietal lobes and temperature discrimination in monkeys

Seven groups of 3 monkeys each were given preoperative training over a series of thermal discrimination tasks of increasing difficulty to use eventually their left hands to detect a 1 °C difference. One group served as an unoperated control (C), and the others were subjected to the following lesions: (1)bilateral SI-bilateral SII; (2)bilateral SI; (3)bilateral SI-contralateral SII; (4)bilateral SII-bilateral posterior parietal; (5)bilateral parietal lobectomy; and (6)contralateral parietal lobectomy. The groups were then tested again on the same tasks. No group showed any difficulty with differences larger than 12 °C, and groups 2, 4, 6 and C showed no statistical differences in their preoperative and postoperative number of trials to criteria for any of the temperature tasks. However, groups 1, 3 and 5 had considerable difficulty making discriminations ranging between 3 and 12 °C; and, although their postoperative performances were not significantly different from one another, they took statiscally more trials to discriminate the 1 ° difference in post- than in testing. Following extensive retraining, all but one of the subjects in the latter groups were able to detect the 1 °C difference It was concluded that the bilateral SI and contralateral SII areas play important roles in the monkey's ability to discriminate fine temperature differences with its hand, but that these areas are not essential to this capacity. It was also concluded that the monkey's parietal cortex plays little or no role in perceiving and reacting to noxious thermal stimulation applied to the hand.

Origin of the initial negative potential (N15) recorded on the skull by superficial radial nerve stimulation in the cat.

The origin of the initial prominent negative potential with a latency of about 15 msec (N15), recorded on the skull by superficial radial nerve stimulation was studied in the cat, and the following results were obtained. In the direct recording from the cortex, SEPs were elicited from the SI and SII areas, as well as the lateral gyrus and anterior suprasylvian gyrus. Among various wave forms recognized in the SI area, diphasic positive-negative (P-N) potential obtained from the postero-lateral part was most distinct, representing the primary evoked potential. Responses recorded on the dura and those directly on the cortex showed similar wave patterns over many sites. Although different forms of evoked potentials were recorded extensively over the skull, the most prominent negative potential was elicited at the site corresponding to the postero-lateral part of the SI area. The latency of this potential was approximately in agreement with that of the negative component of the P-N potential recorded on the cortex. Based on the intracortical laminar analysis of P-N potential, the positive component of this potential was assumed to reflect the activity of cells in the deeper layer of the cortex. The negative component, on the other hand, might represent activities of apical dendrites of the cortex. From the result of functional elimination of the cortex, however, this positive component was thought to contain potentials from far field neural structures. N15 recorded on the skull completely disappeared during cortical spreading depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Topography and cortical generators of somatosensory potentials evoked by median nerve stimulation in the cat

Epidural and cortical mapping of somatosensory evoked activity after mediannerve stimulation was performed under barbiturate anaesthesia in 6 cats. Depth profiles were made to confirm the site of the cortical generators. The area studied revealed two cortical generators in SI and one in SII. In all cases polarity changes in intracortical tracks were demonstrated. The peak latency of all these generators was 12 msec. In SI a P 8 was also a consistent finding in epidural, epicortical and intracortical measurements. No evidence, however, could be obtained for a cortical origin of the P 8. The most rostral generator of the P 12 was localized in the posterior sigmoid gyrus (area 3a). The N 12 originates from the dorso-medial bank of the coronal sulcus in SI (area 2). Histological evidence for these projections was obtained with use of electrode markation. Within the second somatosensory area one source was active; the P 12 originated just lateral to the anterior aspect of the suprasylvian sulcus in the anterior ectosylvian gyrus.

SII-projecting neurons in the rat thalamus: a single- and double-retrograde-tracing study.

Experiments were performed on adult albino rats, using single-labeling (free horseradish peroxidase [HRP] or wheatgerm agglutinin conjugated to HRP [WGA:HRP]) and double-labeling (fluorescent dyes) techniques to investigate the thalamic projections to the secondary somatosensory cortex (SII) and to demonstrate the presence and location of thalamic neurons projecting to both the primary somatosensory cortex (SI) and SII by way of branching axons. In single-labeling experiments, the tracer was injected in SI or SII with or without electrophysiological control; in double-labeling experiments, fast blue and diamidino yellow were injected into the electrophysiologically identified forelimb areas of SI and SII. Single-tracer experiments showed that after injections in SI, focused in the forelimb representation area, retrogradely labeled neurons were present mainly in the ventral third of the nucleus ventralis posterolateralis (VPL) and in the anterior part of the posterior nuclear complex (PO); labeled neurons were also present consistently in the caudal portion of PO. Injection of tracers in the forelimb or forelimb and hindlimb representation areas of SII resulted in labeling of neurons in the posterior part of PO and in the caudal part of VPL. Double-labeling experiments confirmed the distribution of neurons projecting to SI or to SII, as observed in single-labeling experiments. Some neurons labeled with both tracers were also present. These neurons are interpreted as projecting to both SI and SII by means of axon collaterals and were observed in areas of overlap of the two single-labeled population of neurons--that is, at the border between PO and the ventroposterior complex, and in the medial part of caudal PO. Comparison of these data with those obtained after injections of tracers in SI and SII of cats (Spreafico et al., 1981b) suggests that in both species thalamic neurons projecting to these two areas are largely segregated, though partially overlapping; and that thalamic neurons projecting simultaneously to SI and SII, modest in number in cats, are even sparser in rats.

Tooth pulp input to the shell region of nucleus ventralis posteromedialis of the cat thalamus.

A population of neurons in the somatosensory part of the nucleus ventralis posteromedialis (VPM proper) that responded to electrical stimulation of the tooth pulp were studied in cats under urethan-chloralose anesthesia. Two classes of units responsive to electrical stimulation of the contralateral canine tooth pulp were identified. One class was responsive only to tooth pulp stimulation and these units were designated as tooth pulp specific (TPS) units. The other class of units responded to mechanical stimulation of the contralateral trigeminal integument in addition to tooth pulp stimulation. Their receptive field characteristics identified them as wide dynamic range (WDR) units responsive to tooth pulp stimulation. Both classes of units were located in the shell region of the caudal VPM proper; TPS units were coexistent with trigeminal nociceptive specific (NS) units and were found in the dorsomedial as well as ventromedial parts of the NS zone. WDR units responsive to electrical stimulation of the tooth pulp were located in the dorsomedial as well as ventromedial parts of WDR zone, a narrow band, approximately 300 micron wide, just in front of the NS zone. Tooth pulp units in the dorsomedial shell region of the VPM proper responded to the maxillary canine tooth pulp, whereas those in the ventromedial shell region responded to the mandibular canine tooth pulp. Some tooth pulp units in these two regions were responsive to stimulation of both maxillary and mandibular canine teeth. Both TPS and WDR units were antidromically excited by electrical stimulation of the SI area of the somatosensory cortex. Cooling the dorsolateral surface of the caudal medulla oblongata reversibly blocked tooth pulp evoked responses of TPS and WDR units. Trigeminal tractotomy just above the level of the obex irreversibly abolished tooth pulp-evoked responses of TPS and WDR units. These findings suggested that TPS neurons in the marginal layer of the trigeminal subnucleus caudalis and WDR neurons in the lateral part of the subnucleus reticularis dorsalis relay afferent impulses derived from the tooth pulp to the shell region of the VPM proper.

Mixed and sensory nerve stimulations activate different cytoarchitectonic areas in the human primary somatosensory cortex SI. Neuromagnetic recordings and statistical considerations.

Magnetic responses evoked by stimulation of the mixed median nerve at the wrist and its cutaneous branches on the glabrous skin of the index and middle fingers were studied. The first responses to mixed nerve stimulation peaked at 19-24 ms, and those to cutaneous nerve stimulation about 4 ms later. The responses, up to a latency of 150 ms, reversed in polarity between the upper and lower parts of the rolandic fissure. Equivalent dipoles for the mixed nerve stimulation were stronger and they lay statistically significantly deeper from the scalp than those activated by the cutaneous nerve stimulation. It is suggested that mixed nerve stimulation activates areas 3a and 3b whereas cutaneous stimulation activates mainly area 3b at the human primary somatosensory cortex. Statistical procedures were developed for comparison of different field patterns and for determining confidence limits of source model parameters. For these purposes the quality and quantity of the noise were studied. The error caused by inaccuracies in the positioning of the magnetometer was found to be minimal in comparison with the signal noise which was estimated from the standard deviation of the averaged response.