Consciousness.

Until recently, most neuroscientists did not regard consciousness as a suitable topic for scientific investigation. This reluctance was based on certain philosophical mistakes, primarily the mistake of supposing that the subjectivity of consciousness made it beyond the reach of an objective science. Once we see that consciousness is a biological phenomenon like any other, then it can be investigated neurobiologically. Consciousness is entirely caused by neurobiological processes and is realized in brain structures. The essential trait of consciousness that we need to explain is unified qualitative subjectivity. Consciousness thus differs from other biological phenomena in that it has a subjective or first-person ontology, but this subjective ontology does not prevent us from having an epistemically objective science of consciousness. We need to overcome the philosophical tradition that treats the mental and the physical as two distinct metaphysical realms. Two common approaches to consciousness are those that adopt the building block model, according to which any conscious field is made of its various parts, and the unified field model, according to which we should try to explain the unified character of subjective states of consciousness. These two approaches are discussed and reasons are given for preferring the unified field theory to the building block model. Some relevant research on consciousness involves the subjects of blindsight, the split-brain experiments, binocular rivalry, and gestalt switching.

The future of philosophy.

There is no sharp dividing line between science and philosophy, but philosophical problems tend to have three special features. First, they tend to concern large frameworks rather than specific questions within the framework. Second, they are questions for which there is no generally accepted method of solution. And third they tend to involve conceptual issues. For these reasons a philosophical problem such as the nature of life can become a scientific problem if it is put into a shape where it admits of scientific resolution. Philosophy in the 20th century was characterized by a concern with logic and language, which is markedly different from the concerns of earlier centuries of philosophy. However, it shared with the European philosophical tradition since the 17th century an excessive concern with issues in the theory of knowledge and with scepticism. As the century ends, we can see that scepticism no longer occupies centre stage, and this enables us to have a more constructive approach to philosophical problems than was possible for earlier generations. This situation is somewhat analogous to the shift from the sceptical concerns of Socrates and Plato to the constructive philosophical enterprise of Aristotle. With that in mind, we can discuss the prospects for the following six philosophical areas: (1) the traditional mind-body problem; (ii) the philosophy of mind and cognitive science; (iii) the philosophy of language; (iv) the philosophy of society; (v) ethics and practical reasons; (vi) the philosophy of science. The general theme of these investigations, I believe, is that the appraisal of the true significance of issues in the philosophy of knowledge enables us to have a more constructive account of various other philosophical problems than has typically been possible for the past three centuries.

How to study consciousness scientifically.

The neurosciences have advanced to the point that we can now treat consciousness as a scientific problem like any other. The problem is to explain how brain processes cause consciousness and how consciousness is realized in the brain. Progress is impeded by a number of philosophical mistakes, and the aim of this paper is to remove nine of those mistakes: (i) consciousness cannot be defined; (ii) consciousness is subjective but science is objective; (iii) brain processes cannot explain consciousness; (iv) the problem of 'qualia' should be set aside; (v) consciousness is epiphenomenal; (vi) consciousness has no evolutionary function; (vii) a causal account of consciousness is necessarily dualistic; (viii) science is reductionistic, so a scientific account of consciousness would show it reducible to something else; and (ix) an account of consciousness must be an information processing account.

Effect of gingival wall on resistance to probing forces.

This study was conducted to determine whether the gingival tissue lateral to the periodontal sulcus contributes resistance to the advancement of a periodontal probe tip into the sulcus under different applied pressures. An electromechanical device was used to advance a probe tip 0.6 mm in diameter into the facial sulcus at a constant speed until resisting forces of 0.70 N were encountered. The device registered the resisting force and probe advancement simultaneously. The gingiva of all 2nd incisors, 2nd premolars, and 1st molars of 4 young adult male beagle dogs were tested. After the first measurement, the buccal gingiva of experimental sites were incised mesiodistally from the gingival margin to the alveolar crest and the sulcus was reprobed. 2 experimental and control quadrants were selected randomly resulting in 6 sets of both experimental and control data from each animal. The data were analyzed with analysis of variance. The analysis demonstrated significant variation from site to site, and dog to dog; therefore, only changes between the 1st and 2nd probings at the same sites could be compared. Less variability of probing distance in different animals occurred at higher forces; however, the incision had a significant effect on probing distance at these forces. The pressure at which probing distance had less variability among animals and least affected when the gingival sulcular wall was incised was estimated to be 106 N/cm2. This corresponds to 30 g force on the 0.6 mm diameter probe.

Gynecologic and dermatologic electrosurgical units: a comparative review.

Electrosurgery is a popular surgical technique in which high-frequency, low-voltage electrical energy produced by an electrosurgical unit is used to excise abnormal tissue with hemostasis. In this study, electrosurgical units were critically evaluated for safety, electrical specifications, design, and performance characteristics. Quantitative electrical specification and histologic thermal artifact measurements and qualitative observations were recorded for 13 electrosurgical units representing 11 manufacturers. The Aspen Sabre 180 and Laerscope e10 were considered exemplary units based on safety criteria alone. Cut-mode thermal artifact was less than 10 microns for the Cooper Leep 6000, Laserscope e10, and Utah Finesse. A maximum fulguration distance of greater than 0.5 mm was demonstrated by the Gyne-Tech Autolepe 2000 and 4000, Laserscope e10, and the Elmed ESU 30. For gynecologic electrosurgery, the Aspen Sabre 180 and Laserscope e10 were rated best, followed closely by the Utah Finesse and Finesse II and the Gyne-Tech Autolepe 4000. Dermatologic electrosurgery may be well accomplished with many of the electrosurgical units, except as noted.

Reliability of an ambulatory electromyographic activity device for musculoskeletal pain disorders.

A number of investigators in recent years have called for the development of devices that can monitor surface EMG levels in individuals' normal environments for use with patients who suffer from disorders in which the etiology or maintenance of the pathology is presumed to be due at least in part to musculoskeletal dysfunction, such as low back pain, phantom limb pain and tension headache. This study examined the test-retest reliability of just such a device. Twenty-six healthy controls wore a lightweight (24 ounce) device which measured bilateral upper trapezius EMG, as well as peak and integral motion, for 5 consecutive days for up to 18 h each day. ANOVAs on the four measures revealed no difference between any of the four measures over the 5 days. Intra-class correlation coefficients for the two EMG variables across 5 days were both significant with alpha levels set at 0.01. The two EMG measures were highly correlated (r = 0.77); the two motion measures were also highly correlated (r = 0.60), but at a lower magnitude than EMG values; the relationship between EMG and motion was significant, but the magnitude of the between EMG motion correlations (0.26 and 0.35) were lower than the within EMG or motion ones. It was concluded that the test-retest reliability of the ambulatory monitoring device is within acceptable limits. Implications for the use of the device with musculoskeletal pain disorders--particularly headache--are discussed.

In vitro cytotoxicity against human cancer cell lines during pulsed magnetic field exposure.

In an in vitro cell growth assay, carboplatin potency against A-431 cells increased after a 1 hour PMF (pulsed magnetic field) exposure (calculated peak field 5.2 mTesla, with an average field strength of 0.525 mTeslarms; pulses rose for 120 microseconds and then abruptly fell to neutral, and were repeated at a rate of 100 or 250 pulses per second). This potentiating effect was not observed with cisplatin or daunomycin. When cytotoxicity against HT-29 cells was measured, PMF exposure potentiated both carboplatin and daunomycin, but again, not cisplatin. Both cell types exhibited increased growth when exposed only to PMF. Exposure to PMF consistently increased the cell growth of these cancer cell lines, while only some in vitro antineoplastic agents were potentiated by PMFs.

Chemotherapy of human carcinoma xenografts during pulsed magnetic field exposure.

Immune deficient mice growing xenografts of HT-29 or A-431 cell lines were treated with cisplatin, carboplatin or doxorubicin in combination with one hour of wholebody pulsed magnetic field (PMF) exposure (calculated peak field 5.2 mTesla, with an average field strength of 0.525 mTeslarms; pulses rose for 120 microseconds and then abruptly fell to neutral, and were repeated at a rate of 250 pulses per second). At 24 days, the mice in each experiment were found to have significantly (p < 0.05, ANOVA) different tumor sizes among groups. The smallest mean tumor volume was consistently found in the drug+PMF group. With A-431 tumors, the cisplatin+PMF group (T) was significantly smaller, 52% [1-(100T/C)], than the cisplatin alone group (C). In HT-29 tumors, those treated with carboplatin+PMF had the smallest tumor volume at just 34% of the carboplatin-alone group. In HT-29 tumors, the doxorubicin+PMF group was 35% of the doxorubicin alone group.

The problem of consciousness.

This paper attempts to begin to answer four questions. (1) What is consciousness? (2) What is the relation of consciousness to the brain? (3) What are some of the features that an empirical theory of consciousness should try to explain? (4) What are some common mistakes to avoid?

Development of an ambulatory recorder for evaluation of muscle tension-related low back pain and fatigue in soldiers' normal environments.

We have developed an ambulatory recorder capable of monitoring low back muscle tension, trunk motion, and ratings of pain and fatigue. It weighs 22 ounces, fits into a canteen belt, and records every second for 18 hours. Eleven subjects wore the recorder during all walking hours for between 3 and 5 days. Six subjects had chronic low back pain due to muscle tension, three experienced low back pain after labor, and two had no pain. Movement and muscle tension correlated highly when subjects were pain free but not when they were in pain. Muscle tension increased before pain was experienced.

A rapid heating and cooling rate dilatometer for measuring thermal expansion in dental porcelain.

Herein we describe a dilatometer that consists of a low-mass infrared furnace for rapid heating or cooling, an optical pyrometer, and a laser interferometer. The dilatometer facilitates observations of thermal expansion at rates comparable with those in dental laboratory practice over the temperature range necessary for comparison of thermal expansion of dental porcelain and alloy. Examples of thermal expansion data obtained at a 600 degrees C/min heating rate on NIST SRM 710 glass and dental porcelain are reported. To a limited extent, thermal expansion data above the glass-transition temperature range of dental porcelain were obtained. A shift of the glass-transition temperature range to higher temperatures was observed for both materials, compared with data obtained at 20 degrees C/min.

Gingival resistance to probing forces. II. The effect of inflammation and pressure on probe displacement in beagle dog gingivitis.

This study was undertaken to determine the effect of gingival inflammation and probing pressure on probe tip placement in relation to the base of the gingival crevice and the most coronal connective tissue attachment fibers. Nine young male beagle dogs were divided into three groups as determined by clinical status of the gingiva following implementation of a protocol designed to produce gingival health and disease. An electromechanical device was used to advance 0.6 mm diameter probes into the facial gingival crevices of selected teeth and to obtain force-displacement curves. The instrument stopped the probe at pressure of either 80, 160, 320, 640, 1280, or 2560 kPa which were randomly allocated to 12 test teeth in each dog. After the probe came to rest, it was attached to the tooth. When all 12 probes were attached, the animal was sacrificed. Blocks consisting of gingiva, probe, and tooth were processed to obtain two buccolingual sections, one containing the probe and the other immediately adjacent to it. Clinical and histometric measurements were performed and the data evaluated. Although three groups of animals were discernable by clinical criteria, only two groups, health and disease, could be formulated based on the degree of histologic inflammation. The histologic grouping was used in data analysis. Histometric distances from the cemento-enamel junction to the base of the crevice (cJ), to most coronal connective tissue attachment (cC) and to the probe tip (cP) all increased with change from health to disease. However, changes in health/disease did not influence difference between distances (cP-cJ,cP-cC).(ABSTRACT TRUNCATED AT 250 WORDS)

Gingival resistance to probing forces. I. Determination of optimal probe diameter.

This paper presents the results of a study designed to determine (1) if advancement of a periodontal probe under a given force against healthy gingiva differed from its advancement under a similar force, against inflamed gingiva, and (2) to select the diameter which best distinguishes healthy gingiva from that which is inflamed to varying degrees. The teeth of eight beagle dogs were cleaned three times per week for two months until a Gingival Index (GI) of 0 and gingival fluid flow (GFF) of 9 or less, as measured by the Periotron, were obtained. Probes of diameters 0.4, 0.6, 0.7, and 0.8 mm were advanced perpendicularly against the attached gingiva in the incisor, premolar, and molar regions by an electromechanical device which simultaneously plotted force versus displacement following initial contact of the probe tip with the gingiva. These forces ranged from 0.1 to 0.9N. This process was repeated in the same animals following cessation of plaque control measures when the GI reached a value of 1 and GFF reached levels of 10 to 19. It was repeated again following placement of an irritating ligature when GI reached 2 and GFF greater than 20. An analysis of covariance showed significant differences between all three levels of health and disease for all probe diameters. F values for the 0.6 mm probe were highest at all probing forces indicating that this diameter most consistently discriminated variation of gingival health status.

Computerized analysis of resting fetal heart rate tracings.

Previous attempts to computerize the analysis of fetal heart rate (FHR) using mainframe or minicomputers were not accepted in routine clinical practice because of their complexity, cost, and lack of validation. We describe the first practical, inexpensive system integrated into a clinical protocol that analyzes and documents FHR baseline, long-term variability, and episodic events using a standard microcomputer. A comparison of computerized and manual analyses of 284 nonstress tests (NSTs) of high-risk patients revealed no significant differences in determining the number of acceleration and deceleration events and mean FHR baseline. Long-term variability and other reported data could not be compared for lack of manual techniques. The combination of standardized analysis and quantified data may improve the predictive value of the computerized NST compared with the visually analyzed NST. Other benefits include computerized archiving, data transmission by telephone, and linkage to a perinatal data base.

Electrophysiological changes in the primary sensory neuron following subchronic soman and sarin: alterations in sensory receptor function.

Cats were administered soman or sarin either in a single high dose (1 mg/kg) with pretreatment or in multiple sublethal doses to determine whether these potent organophosphorus agents could produce a delayed neurotoxicity and what, if any, pathophysiological changes occurred in peripheral sensory receptors. Neither soman nor sarin, when administered as a single high dose, produced a delayed neurotoxicity as observed behaviorally for up to 60 days. There were also no observable signs of delayed neurotoxicity when these agents were administered in multiple doses. Functional tests of proprioceptors and mechanoreceptors were performed on the cats which received multiple sublethal doses of either soman or sarin. It was found that the discharge rates of muscle spindle primary endings were depressed while the discharge rates of secondary endings were facilitated following the administration of either soman or sarin. The discharge rates of slowly adapting type 1 mechanoreceptors were also depressed. The total number of identified mechanoreceptors was reduced in both the soman- and sarin-treated animals. Conduction velocities of several of the muscle spindle and mechanoreceptor afferents were significantly decreased. The alterations in muscle spindle function may be due to changes in the muscle resulting from acetylcholinesterase inhibition. Another explanation for the changes in both muscle spindle and mechanoreceptor function may be the direct effect of the organophosphorus agents on the afferents themselves, thus altering their excitability.

Maternal dietary substrates and human fetal biophysical activity. I. The effects of tryptophan and glucose on fetal breathing movements.

To study the effects of L-tryptophan and glucose on fetal breathing activity, we examined 40 women with normal term pregnancies, randomly assigned to four equal groups who either continued fasting (group C), received 1 gm of oral tryptophan (group T), received 100 gm of oral glucose (group G), or received both substrates (group T + G). Studies lasted 210 minutes, during which fetal breathing movements were observed with real-time ultrasonography and entered and analyzed for incidence, rate, and variability on a microcomputer. Plasma glucose and tryptophan levels were determined every 30 minutes. The incidence of fetal breathing movements declined in group C and rose significantly in the other groups. Breathing rates were unchanged in groups C and T but rose significantly in groups G and T + G during peak breathing intervals. Breath interval variability did not change significantly in any study group. Maternal administration of tryptophan is associated with an alteration in fetal breathing activity but to a lesser degree than that observed after maternal glucose loading.

Effect of pressure on cerebrospinal fluid absorption in cats, baboons, and humans: comparison of the linear and logarithmic models.

To circumvent time constraints inherent in indicator clearance measurements of cerebrospinal fluid absorption, investigators have used the relationship between CSF pressure at steady state and the rate of infusion of mock CSF, in both patients and experimental animals, to evaluate the bulk absorption rate of CSF. This latter approach required mathematical model of the effect of CSF pressure on CSF bulk flow. Two such models--a fixed resistance and a variable resistance model of CSF flow through arachnoid villi--have been used in both clinical and laboratory settings. In this study, the relationship between steady state CSF pressure and mock CSF infusion rate was assessed using both mathematical models. We studied two patients, three cats, and seven baboons. Values of CSF outflow resistance calculated according to both models as well as other parameters of CSF bulk flow estimated on the basis of both models were all in the range expected from other studies. The data from these experiments do not provide justification for preferring one model over the other. Depending on the experimental or clinical situation, some of the assumptions behind both models may not be valid. Multiple direct measurements of the rates of CSF absorption and formation over a wide range of CSF pressures in individual subjects will be necessary to validate either the variable or the fixed resistance model or to suggest a more appropriate model. Until such information is available, it is probably reasonable to use both approaches for the analysis of mock CSF infusion data. CSF bulk flow parameters calculated on the basis of either the variable or the fixed resistance model should never be taken as absolute, but should be evaluated critically in the context of the clinical or experimental situation.