The effects of physiological and injurious hydrostatic pressure on murine ex vivo articular and growth plate cartilage explants: an RNAseq study

Introduction

Chondrocytes are continuously exposed to loads placed upon them. Physiological loads are pivotal to the maintenance of articular cartilage health, while abnormal loads contribute to pathological joint degradation. Similarly, the growth plate cartilage is subject to various loads during growth and development. Due to the high-water content of cartilage, hydrostatic pressure is considered one of the main biomechanical influencers on chondrocytes and has been shown to play an important role in the mechano-regulation of cartilage.

Methods

Herein, we conducted RNAseq analysis of ex vivo hip cap (articular), and metatarsal (growth plate) cartilage cultures subjected to physiological (5 MPa) and injurious (50 MPa) hydrostatic pressure, using the Illumina platform (n = 4 replicates).

Results

Several hundreds of genes were shown to be differentially modulated by hydrostatic pressure, with the majority of these changes evidenced in hip cap cartilage cultures (375 significantly upregulated and 322 downregulated in 5 MPa versus control; 1022 upregulated and 724 downregulated in 50 MPa versus control). Conversely, fewer genes were differentially affected by hydrostatic pressure in the metatarsal cultures (5 significantly upregulated and 23 downregulated in 5 MPa versus control; 7 significantly upregulated and 19 downregulated in 50 MPa versus control). Using Gene Ontology annotations for Biological Processes, in the hip cap data we identified a number of pathways that were modulated by both physiological and injurious hydrostatic pressure. Pathways upregulated in response to 50 MPa versus control, included those involved in the generation of precursor metabolites and cellular respiration. Biological processes that were downregulated in this tissue included ossification, connective tissue development, and chondrocyte differentiation.

Discussion

Collectively our data highlights the divergent chondrocyte phenotypes in articular and growth plate cartilage. Further, we show that the magnitude of hydrostatic pressure application has distinct effects on gene expression and biological processes in hip cap cartilage explants. Finally, we identified differential expression of a number of genes that have previously been identified as osteoarthritis risk genes, including Ctsk, and Chadl. Together these data may provide potential genetic targets for future investigations in osteoarthritis research and novel therapeutics.

Evidence that pyrophosphate acts as an extracellular signalling molecule to exert direct functional effects in primary cultures of osteoblasts and osteoclasts

Extracellular pyrophosphate (PPi) is well known for its fundamental role as a physiochemical mineralisation inhibitor. However, information about its direct actions on bone cells remains limited. This study shows that PPi decreased osteoclast formation and resorptive activity by ≤50 %. These inhibitory actions were associated with reduced expression of genes involved in osteoclastogenesis (Tnfrsf11a, Dcstamp) and bone resorption (Ctsk, Car2, Acp5). In osteoblasts, PPi present for the entire (0-21 days) or latter stages of culture (7-21/14-21 days) decreased bone mineralisation by ≤95 %. However, PPi present for the differentiation phase only (0-7/0-14 days) increased bone formation (≤70 %). Prolonged treatment with PPi resulted in earlier matrix deposition and increased soluble collagen levels (≤2.3-fold). Expression of osteoblast (RUNX2, Bglap) and early osteocyte (E11, Dmp1) genes along with mineralisation inhibitors (Spp1, Mgp) was increased by PPi (≤3-fold). PPi levels are regulated by tissue non-specific alkaline phosphatase (TNAP) and ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). PPi reduced NPP1 expression in both cell types whereas TNAP expression (≤2.5-fold) and activity (≤35 %) were increased in osteoblasts. Breakdown of extracellular ATP by NPP1 represents a key source of PPi. ATP release from osteoclasts and osteoblasts was decreased ≤60 % by PPi and by a selective TNAP inhibitor (CAS496014-12-2). Pertussis toxin, which prevents Gαi subunit activation, was used to investigate whether G-protein coupled receptor (GPCR) signalling mediates the effects of PPi. The actions of PPi on bone mineralisation, collagen production, ATP release, gene/protein expression and osteoclast formation were abolished or attenuated by pertussis toxin. Together these findings show that PPi, modulates differentiation, function and gene expression in osteoblasts and osteoclasts. The ability of PPi to alter ATP release and NPP1/TNAP expression and activity indicates that cells can detect PPi levels and respond accordingly. Our data also raise the possibility that some actions of PPi on bone cells could be mediated by a Gαi-linked GPCR.

Modulation of osteoblast differentiation and function by the P2X4 receptor

Bone cells are known to express multiple P2 receptor subtypes, and the functional effects of receptor activation have been described for many of these. One exception is the P2X4 receptor, which despite strong expression in osteoblasts and osteoclasts, has no defined functional activity. This study used the selective P2X4 receptor antagonists, 5-BDBD and PSB-12062, to investigate the role of this receptor in bone. Both antagonists (≥ 0.1 μM) dose-dependently decreased bone formation by 60-100%. This was accompanied by a ≤ 70% decrease in alkaline phosphatase activity, a ≤ 40% reduction in cell number, and a ≤ 80% increase in the number of adipocytes present in the culture. The analysis of gene expression showed that levels of osteoblast marker genes (e.g. Alpl, Bglap) were decreased in 5-BDBD treated cells. Conversely, expression of the adipogenic transcription factor PPARG was increased 10-fold. In osteoclasts, high doses of both antagonists were associated with a reduction in osteoclast formation and resorptive activity by ≤ 95% and ≤ 90%, respectively. Taken together, these data suggest that the P2X4 receptor plays a role in modulating bone cell function. In particular, it appears to influence osteoblast differentiation favouring the osteogenic lineage over the adipogenic lineage.

N-acetylcysteine (NAC) differentially affects arterial medial calcification and bone formation: The role of l-cysteine and hydrogen sulphide

Arterial medial calcification (AMC) is the deposition of calcium phosphate in the arteries. AMC is widely thought to share similarities with physiological bone formation; however, emerging evidence suggests several key differences between these processes. N-acetylcysteine (NAC) displays antioxidant properties and can generate hydrogen sulphide (H₂ S) and glutathione (GSH) from its deacetylation to l-cysteine. This study found that NAC exerts divergent effects in vitro, increasing osteoblast differentiation and bone formation by up to 5.5-fold but reducing vascular smooth muscle cell (VSMC) calcification and cell death by up to 80%. In vivo, NAC reduced AMC in a site-specific manner by 25% but had no effect on the bone. The actions of l-cysteine and H₂ S mimicked those of NAC; however, the effects of H₂ S were much less efficacious than NAC and l-cysteine. Pharmacological inhibition of H₂ S-generating enzymes did not alter the actions of NAC or l-cysteine; endogenous production of H₂ S was also unaffected. In contrast, NAC and l-cysteine increased GSH levels in calcifying VSMCs and osteoblasts by up to 3-fold. This suggests that the beneficial actions of NAC are likely to be mediated via the breakdown of l-cysteine and the subsequent GSH generation. Together, these data show that while the molecular mechanisms driving the actions of NAC appear similar, the downstream effects on cell function differ significantly between osteoblasts and calcifying VSMCs. The ability of NAC to exert these differential actions further supports the notion that there are differences between the development of pathological AMC and physiological bone formation. NAC could represent a therapeutic option for treating AMC without exerting negative effects on bone.

Regulation of mineralisation in bone and vascular tissue: a comparative review

Biomineralisation, the deposition of mineral onto a matrix, can be both a physiological and pathological process. Bone formation involves the secretion of an extracellular matrix (ECM) by osteoblasts and subsequent mineralisation of that matrix. It is regulated by a number of local and systemic factors and is necessary for maintenance of normal bone health. Conversely, mineralisation (or calcification) of soft tissues, including the vasculature, is detrimental to that tissue, leading to diseases such as arterial medial calcification (AMC). The mechanisms underlying AMC development are not fully defined, though it is thought that vascular smooth muscle cells (VSMCs) drive this complex, cell-mediated process. Similarly, AMC is regulated by a variety of enzymes and molecules, many of which have already been implicated in the regulation of bone mineralisation. This review will provide an overview of the similar, and sometimes opposing effects of these signalling molecules on the regulation of bone mineralisation and AMC.

2-Oxothiazolidine-4-carboxylic acid inhibits vascular calcification via induction of glutathione synthesis

Arterial medial calcification (AMC), the deposition of hydroxyapatite in the medial layer of the arteries, is a known risk factor for cardiovascular events. Oxidative stress is a known inducer of AMC and endogenous antioxidants, such as glutathione (GSH), may prevent calcification. GSH synthesis, however, can be limited by cysteine levels. Therefore, we assessed the effects of the cysteine prodrug 2-oxothiazolidine-4-carboxylic acid (OTC), on vascular smooth muscle cell (VSMC) calcification to ascertain its therapeutic potential. Human aortic VSMCs were cultured in basal or mineralising medium (1 mM calcium chloride/sodium phosphate) and treated with OTC (1-5 mM) for 7 days. Cell-based assays and western blot analysis were performed to assess cell differentiation and function. OTC inhibited calcification ≤90%, which was associated with increased ectonucleotide pyrophosphatase/phosphodiesterase activity, and reduced apoptosis. In calcifying cells, OTC downregulated protein expression of osteoblast markers (Runt-related transcription factor 2 and osteopontin), while maintaining expression of VSMC markers (smooth muscle protein 22α and α-smooth muscle actin). GSH levels were significantly reduced by 90% in VSMCs cultured in calcifying conditions, which was associated with declines in expression of gamma-glutamylcysteine synthetase and GSH synthetase. Treatment of calcifying cells with OTC blocked the reduction in expression of both enzymes and prevented the decline in GSH. This study shows OTC to be a potent and effective inhibitor of in vitro VSMC calcification. It appears to maintain GSH synthesis which may, in turn, prevent apoptosis and VSMCs gaining osteoblast-like characteristics. These findings may be of clinical relevance and raise the possibility that treatment with OTC could benefit patients susceptible to AMC.

Differing calcification processes in cultured vascular smooth muscle cells and osteoblasts

Arterial medial calcification (AMC) is the deposition of calcium phosphate mineral, often as hydroxyapatite, in the medial layer of the arteries. AMC shares some similarities to skeletal mineralisation and has been associated with the transdifferentiation of vascular smooth muscle cells (VSMCs) towards an osteoblast-like phenotype. This study used primary mouse VSMCs and calvarial osteoblasts to directly compare the established and widely used in vitro models of AMC and bone formation. Significant differences were identified between osteoblasts and calcifying VSMCs. First, osteoblasts formed large mineralised bone nodules that were associated with widespread deposition of an extracellular collagenous matrix. In contrast, VSMCs formed small discrete regions of calcification that were not associated with collagen deposition and did not resemble bone. Second, calcifying VSMCs displayed a progressive reduction in cell viability over time (≤7-fold), with a 50% increase in apoptosis, whereas osteoblast and control VSMCs viability remained unchanged. Third, osteoblasts expressed high levels of alkaline phosphatase (TNAP) activity and TNAP inhibition reduced bone formation by to 90%. TNAP activity in calcifying VSMCs was ∼100-fold lower than that of bone-forming osteoblasts and cultures treated with β-glycerophosphate, a TNAP substrate, did not calcify. Furthermore, TNAP inhibition had no effect on VSMC calcification. Although, VSMC calcification was associated with increased mRNA expression of osteoblast-related genes (e.g. Runx2, osterix, osteocalcin, osteopontin), the relative expression of these genes was up to 40-fold lower in calcifying VSMCs versus bone-forming osteoblasts. In summary, calcifying VSMCs in vitro display some limited osteoblast-like characteristics but also differ in several key respects: 1) their inability to form collagen-containing bone; 2) their lack of reliance on TNAP to promote mineral deposition; and, 3) the deleterious effect of calcification on their viability.

Isolation and Generation of Osteoblasts

This chapter describes the isolation, culture, and staining of osteoblasts. The key advantages of this assay are that it allows direct measurement of bone matrix deposition and mineralization, as well as yielding good quantities of osteoblasts at defined stages of differentiation for molecular and histological analysis. An additional focus of this chapter will be the culture of osteoblasts from less conventional animal species.

Inhibition of arterial medial calcification and bone mineralization by extracellular nucleotides: The same functional effect mediated by different cellular mechanisms

Arterial medial calcification (AMC) is thought to share some outward similarities to skeletal mineralization and has been associated with the transdifferentiation of vascular smooth muscle cells (VSMCs) to an osteoblast-like phenotype. ATP and UTP have previously been shown to inhibit bone mineralization. This investigation compared the effects of extracellular nucleotides on calcification in VSMCs with those seen in osteoblasts. ATP, UTP and the ubiquitous mineralization inhibitor, pyrophosphate (PP_i ), dose dependently inhibited VSMC calcification by ≤85%. Culture of VSMCs in calcifying conditions was associated with an increase in apoptosis; treatment with ATP, UTP, and PP_i reduced apoptosis to levels seen in non-calcifying cells. Extracellular nucleotides had no effect on osteoblast viability. Basal alkaline phosphatase (TNAP) activity was over 100-fold higher in osteoblasts than VSMCs. ATP and UTP reduced osteoblast TNAP activity (≤50%) but stimulated VSMC TNAP activity (≤88%). The effects of extracellular nucleotides on VSMC calcification, cell viability and TNAP activity were unchanged by deletion or inhibition of the P2Y₂ receptor. Conversely, the actions of ATP/UTP on bone mineralization and TNAP activity were attenuated in osteoblasts lacking the P2Y₂ receptor. Ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) hydrolyses ATP and UTP to produce PP_i . In both VSMCs and osteoblasts, deletion of NPP1 blunted the inhibitory effects of extracellular nucleotides suggesting involvement of P2 receptor independent pathways. Our results show that although the overall functional effect of extracellular nucleotides on AMC and bone mineralization is similar there are clear differences in the cellular mechanisms mediating these actions.

Retention and transfer of morse code reception skill by novices: part-whole training

The training of composite skills requiring differential responding to a large set of stimuli raises issues about how to break down the whole task into parts and which parts should be trained first. Components of Morse code reception skill were identified, separated, and used to test whether initial training on a difficult part was more effective than initial training on an easy part. Initial training on a difficult subset of stimuli and on a difficult subtask both yielded disadvantages rather than the advantage implied by recent findings with different tasks. Incremental training should begin with the part yielding the most effective strategic skills, which appear to depend on characteristics of the task. In both present experiments, easy initial training led to adoption of an effective unitization strategy for representing codes. The hypothesis that procedural reinstatement at delayed testing leads to better retention was supported and extended.

Retention and transfer of morse code reception skill by novices: part-whole training

The training of composite skills requiring differential responding to a large set of stimuli raises issues about how to break down the whole task into parts and which parts should be trained first. Components of Morse code reception skill were identified, separated, and used to test whether initial training on a difficult part was more effective than initial training on an easy part. Initial training on a difficult subset of stimuli and on a difficult subtask both yielded disadvantages rather than the advantage implied by recent findings with different tasks. Incremental training should begin with the part yielding the most effective strategic skills, which appear to depend on characteristics of the task. In both present experiments, easy initial training led to adoption of an effective unitization strategy for representing codes. The hypothesis that procedural reinstatement at delayed testing leads to better retention was supported and extended.

Cross-modality priming between odors and odor-congruent words

It is well known that the Stroop effect is subject to influence by same-modality primes, but the possibility of cross-modal priming effects is unclear. Smell is a fundamental sensory system that is assumed to have potent cross-modality priming effects. We might expect the presence of a specific odor to interfere with performance on Stroop cards containing odor-congruent words. Forty participants, half of whom were primed with an unpleasant odor and half with a pleasant odor, were examined with modified Stroop cards containing pleasant and unpleasant descriptive words. A significant Stroop card by odor group interaction was found, indicating that the presence of an odor interferes with the performance on an odor-congruent Stroop card. These findings demonstrate cross-modality priming between olfaction and vision.

Effects of cortical polarization on mental arithmetic

A biofeedback procedure was used to influence participants' cortical polarity before the presentation of single digit multiplication problems. To ensure that participants could solve the problems by direct memory retrieval of arithmetic facts, only nine different multiplication problems were used, and participants received extensive pre-experimental practice on these problems. After biofeedback training, cortical positivity before problem presentation was associated with faster response initiation times, a measure of mental calculation time, for correctly solved problems and with more multiplication errors than cortical negativity. Response execution time, a measure of motor speed, was not affected by cortical polarity. The shift in positivity from the amplitude of the slow cortical potential (SCP) before problem presentation to the amplitude of the positive slow wave (pSW) after problem presentation was less in positivity-required compared to negativity-required trials, mainly because of the manipulation of SCP starting points by biofeedback. We assume that cortical positivity is associated with direct retrieval of arithmetic facts, more precisely with the inhibition of incorrect answers. Cortical positivity before task presentation results in a reduced positive shift, a sign of less inhibition before answer production. The effect of less inhibition during positivity-required trials is to produce faster responses and more errors. The opposite might to be true of cortical negativity.

Some tests of an identical elements model of basic arithmetic skills

Two experiments tested an identical elements model of the organization of basic arithmetic skills (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994). This model assumes a distinct abstract representation for each unique combination of the basic elements (i.e., the operands and the required operation) of a problem. Participants practiced multiplication and division problems and were then tested on various altered versions of these problems. Experiment 1 confirmed the prediction of no positive transfer when the presented elements of a test problem do not exactly match those of a practice problem. Experiment 2 confirmed the prediction that there is complete transfer when the elements of the test problem match exactly with those of a practice problem. Experiment 2 also confirmed that there is both perceptually specific and nonspecific speed-up with practice. Implications for number processing and arithmetic are discussed.

Neurophysiological correlates of mental arithmetic

Thirteen subjects were extensively trained on nine multiplication problems varying in difficulty. Practice was associated with a reaction time speed up and an attenuation of the problem size effect. The introduction of previously unpracticed problems led to a performance rebound to pretraining levels, indicating practice specificity. The eventrelated potentials were characterized by a late positive complex, followed by a positive slow wave. Offset latency of positive slow wave and preresponse amplitude at parietal electrodes showed practice specificity effects that systematically changed with practice and problem size, indicating an association with the load imposed on working memory. The peak of the late positive complex probably reflects task learning or adaptation effects because it was attenuated by practice predominantly at frontal electrodes, showed no practice specificity, and was not affected by problem size.

Some tests of an identical elements model of basic arithmetic skills

Two experiments tested an identical elements model of the organization of basic arithmetic skills (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994). This model assumes a distinct abstract representation for each unique combination of the basic elements (i.e., the operands and the required operation) of a problem. Participants practiced multiplication and division problems and were then tested on various altered versions of these problems. Experiment 1 confirmed the prediction of no positive transfer when the presented elements of a test problem do not exactly match those of a practice problem. Experiment 2 confirmed the prediction that there is complete transfer when the elements of the test problem match exactly with those of a practice problem. Experiment 2 also confirmed that there is both perceptually specific and nonspecific speed-up with practice. Implications for number processing and arithmetic are discussed.

Brain potentials during mental arithmetic: effects of extensive practice and problem difficulty

Recent behavioral investigations indicate that the processes underlying mental arithmetic change systematically with practice from deliberate, conscious calculation to automatic, direct retrieval of answers from memory [Bourne, L.E.Jr. and Rickard, T.C., Mental calculation: The development of a cognitive skill, Paper presented at the Interamerican Congress of Psychology, San Jose, Costa Rica, 1991: Psychol. Rev., 95 (1988) 492-527]. Results reviewed by Moscovitch and Winocur [In: The handbook of aging and cognition, Erlbaum, Hillsdale, NJ, 1992, pp. 315-372] suggest that consciously controlled processes are more dependent on frontal lobe function than are automatic processes. It is appropriate, therefore to determine whether transitions in the locus of primary brain activity occur with practice on mental calculation. In this experiment, we examine the relationship between characteristics of event-related brain potentials (ERPs) and mental arithmetic. Single-digit mental multiplication problems varying in difficulty (problem size) were used, and subjects were trained on these problems for four sessions. Problem-size and practice effects were reliably found in behavioral measures (RT). The ERP was characterized by a pronounced late positivity after task presentation followed by a slow wave, and a negativity during response indication. These components responded differentially to the practice and problem-size manipulations. Practice mainly affected topography of the amplitude of positivity and offset latency of slow wave, and problem-size mainly offset latency of slow wave and pre-response negativity. Fronto-central positivity diminished from session to session, and the focus of positivity centered finally at centro-parietal regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term repetition effects for motoric and perceptual procedures

Two experiments examined the relationship between implicit and explicit measures of memory for information encoded in a motoric task, called data entry. In both experiments, subjects entered lists of digit sequences with a computer keypad. They were retested on the same task after a delay of up to 1 month. At retention, implicit memory for the digit lists was evidenced by faster entry of old relative to new lists in both experiments. In Experiment 1, subjects were able to discriminate old from new lists. Recognition memory of old lists was better after than before entering the lists. In Experiment 2, perceptual and motoric contributions to the old/new difference in typing speed were isolated by means of a transfer paradigm. The results showed that the entry-speed advantage for the old lists was due to the separate reinstatement at the retention test of both perceptual and motoric procedures encoded earlier. Implicit and explicit measures of memory were found to be dependent rather than independent. The findings from this study are interpreted within a framework of memory based on procedural reinstatement.

Long-term repetition effects for motoric and perceptual procedures

Two experiments examined the relationship between implicit and explicit measures of memory for information encoded in a motoric task, called data entry. In both experiments, subjects entered lists of digit sequences with a computer keypad. They were retested on the same task after a delay of up to 1 month. At retention, implicit memory for the digit lists was evidenced by faster entry of old relative to new lists in both experiments. In Experiment 1, subjects were able to discriminate old from new lists. Recognition memory of old lists was better after than before entering the lists. In Experiment 2, perceptual and motoric contributions to the old/new difference in typing speed were isolated by means of a transfer paradigm. The results showed that the entry-speed advantage for the old lists was due to the separate reinstatement at the retention test of both perceptual and motoric procedures encoded earlier. Implicit and explicit measures of memory were found to be dependent rather than independent. The findings from this study are interpreted within a framework of memory based on procedural reinstatement.

Facilitating text memory with additional processing opportunities in rapid sequential reading

Previous research indicates that during conventional reading, readers pause at particular loci within a text, presumably for the purpose of higher level processing and integration. If such pausing is necessary for efficient text comprehension and memory, then providing readers with equivalent processing opportunities with strategically placed pauses in rapid sequential visual presentation (RSVP) text displays should facilitate comprehension and memory. Three experiments are reported in which various time parameters of RSVP displays are manipulated. The results indicate that memory for specific text is facilitated when additional processing time is provided. However, how and where the additional time is distributed within a text, over broad limits, is not important. We use a method of text memory assessment that is not typically used in RSVP research and that is more sensitive to text presentation manipulations than the commonly used multiple-choice questions. This fill-in-the-blank technique also provides evidence that memory representations for texts are structured as meaningful subsentence units.

Facilitating text memory with additional processing opportunities in rapid sequential reading

Previous research indicates that during conventional reading, readers pause at particular loci within a text, presumably for the purpose of higher level processing and integration. If such pausing is necessary for efficient text comprehension and memory, then providing readers with equivalent processing opportunities with strategically placed pauses in rapid sequential visual presentation (RSVP) text displays should facilitate comprehension and memory. Three experiments are reported in which various time parameters of RSVP displays are manipulated. The results indicate that memory for specific text is facilitated when additional processing time is provided. However, how and where the additional time is distributed within a text, over broad limits, is not important. We use a method of text memory assessment that is not typically used in RSVP research and that is more sensitive to text presentation manipulations than the commonly used multiple-choice questions. This fill-in-the-blank technique also provides evidence that memory representations for texts are structured as meaningful subsentence units.

Thought disorder and schizophrenia: isolating and timing a mental event

This study explored the ability of nonparanoid schizophrenic, paranoid schizophrenic, and mixed psychiatric control (manics and schizoaffectives) patients to perform on two types of conceptual, speeded inference (SI) tasks, which differ in type of abstraction process required. The subjects (N = 30) were grouped into high and low levels of thought dysfunction, as measured by the Whitaker Index of Schizophrenic Thinking (WIST). There were no differences among the three clinical groups on the conceptual, SI tasks. Reaction times differed reliably across the two SI tasks. High-WIST subjects were impaired on SI accuracy. Significant impairment in accuracy was demonstrated by high-WIST time and error groups on the more complex SI tasks. Information processing deficit was demonstrated in terms of encoding phase and reaction time in problem-solving of the three diagnostic groups as a function of WIST levels.

Chronic alcoholism in males: cognitive deficit as a function of age of onset, age, and duration

Performance on a cognitive rule-learning task was studied in detoxified alcoholics having early/late onset and short-/long-term drinking histories, and in matched nonalcoholic controls. There were pronounced cognitive deficits in early onset and long-term alcoholics. Impairment was severest in the early onset group, even though they were on the average 15 years younger than the late onset group. Early onset alcoholics were relatively more impaired on both the abstract and the verbal Shipley measures. This group also manifested a relative deficit in ability to show positive transfer across problems. Chronicity of alcoholism also interfered with acquisition of an abstract relationship between concrete stimulus attributes. Age negatively influenced ability to perform abstractions, but not commonly tested verbal skills. The findings suggest that an early onset of alcoholism, regardless of duration of problem drinking, is particularly predictive of cognitive impairment.

Cognitive and electrophysiologic parameters during ascending and descending limbs of the blood alcohol curve

This study examined the effects of acute alcohol ingestion and prior success or failure upon cognitive performance of 40 healthy, non-alcoholic subjects, during both the ascending and descending limbs of the blood alcohol curve. Measures of physiological arousal were made with frontal/laryngeal electromyographic and skin conductance response level parameters. Major findings were: (1) cognitive performance was impaired by alcohol ingestion; (2) autonomic arousal was significantly greater after alcohol than after placebo; (3) number and amplitude of skin response were greater on the ascending than on the descending limb; (4) the anticipated effects of failure on cognitive performance were ameliorated by alcohol; and (5) differential effects of alcohol on the psychophysiological parameters were demonstrated.

Stimulus-rule interactions in concept verification

The difficulty of learning a conceptual rule has been shown to depend upon the stimulus attributes which that rule conjoins. For what appear to be separable attributes, the disjunctive rule is easier than the conjunctive. In contrast, for what appear to be integrable attributes, the conjunctive rule is easier. This paper reports six experiments designed to determine whether the integrality of stimulus attributes affects the speed of verification of the stimulus, as positive or negative, with respect to a given conjunctive or disjunctive concept. The pattern of reaction times is not consistent with the result of rule-learning experiments and does not support an integrality hypothesis. Verification times seem to be more a function of the perceptual salience of the relevant attributes of the concept. Thus, a perceptual-integrality hypothesis is an unlikely explanation of rule learning results.

Schizophrenic cognitive dysfunction: a deficit in rule transfer

This study examined conceptual rule learning (RL) deficit in male schizophrenic Ss categorized into three groups as defined by Whitaker Index of Schizophrenic Thinking (WIST). Ss were administered a conjunctive, disjunctive, conditional or biconditional rule learning task, WIST, and Shipley-Hartford Memory Scale. It was shown that: (a) the WIST reliably differentiates among three levels of thought disorder as reflected by a deficit in inter-problem transfer of rule learning; (b) certain WIST and Shipley parameters reliably predict RL performance; and (c) phenothiazine dosage levels show no influence on the WIST and no correlation with RL. The findings indicate that cognitive dysfunction in schizophrenics is evidenced by limited inductive reasoning, insufficient channel capacity for filtering out irrelevant information, and inability to gain from antecedent RL experience. Principal locus of schizophrenic thought disorder is examined within a stimulus encoding-information processing paradigm.

Limits to conceptual rule-learing by schizophrenic patients

Two studies of conceptual rule-learning by 36 hospitalized psychiatric patients revealed that (a) while all were clinically diagnosed as schizophrenic, they differed widely in their ability to discover abstract rules; (b) the Whitaker Index of Schizophrenic Thinking (WIST) strongly predicted the patients' ability to learn and to apply a conceptual rule; and (c) regardless of severity of conceptual impairment, the patients were unaffected by modest levels of externally generated irrelevant information as presented through the modality of vision. Deficits in abstractive ability, when they exist, are believed to be due to a schizophrenic patient's inability to prevent task-irrelevant information that originates in long-term memory from spilling into and despoiling the operations of working memory.

Encoding the levels of information in pictures and words

From a levels-of -processing framework (e.g., Craik & Lockhart, 1972), we derive the idea that the levels of information implicit in a stimulus, such as its physical configuration, its name, and the category to which it belongs, may become available for subsequent processing at different times after stimulus onset. In particular, tasks which allow the use of physical codes should be performed more rapidly than those which require "deeper" information. There are two important implications here: The first is that the ability to use a code does not mean that that code has been "matched to" a representation in memory. The second is that "depth" effects (i.e., physical less than name less than conceptual) should be demonstrable within both pictorial and verbal materials. The approach as a whole may be contrasted with current dual-coding approaches (e.g., Paivio, Note 1), which, while they allow for different levels of meaning in both verbal and imaginal symbolic systems, seem forced to assume that certain types of cenceptual information are more easily accommodated within the verbal system. This leads to the prediction that some kinds of conceptual information will not be directly available from pictures, but must instead become available to the subject via an interaction between the symbolic systems. We tested these assumptions with a speeded-inference task (Van Rijn, 1973), which has properties that allow for unambiguous interpretation of reaction time differences across stimulus materials which require processing to the same explicit depth. Briefly, we found that pictures yield faster inferences than do words when the same semantic information is required for performance (Experiments 1 and 2), and that physical information is available sooner than conceptual information for both pictures (Experiment 4) and words (Experiment 5). Moreover, some types of pictorial materials (e.g., representations of proper nouns) function symbolically to the extent that they do not have an advantage in discriminability over words (Experiments 6 and 7), unless physical features are added to them which are redundant with the conceptual information the subject needs to perform (Experiment 8). The results are best interpreted within a levels-of-processing framework, in which multiple codes or representations do not exist to be activated by the appropriate stimuli, but rather the stimuli themselves embody levels of information which are encoded and used as needed.

Some observations on the stability of matched shape

The stability of shape matching was determined by repeated testing of college students at 5-wk. intervals and by comparing schizophrenics receiving electroconvulsive shock therapy with a matched group not receiving shock. The data indicate that the obtained matched-shape values are not influenced by any of the variables utilized in these studies.