Longitudinal evaluation of T1ρ and T2 spatial distribution in osteoarthritic and healthy medial knee cartilage.

OBJECTIVE: To investigate longitudinal changes in laminar and spatial distribution of knee articular cartilage magnetic resonance imaging (MRI) T1ρ and T2 relaxation times, in individuals with and without medial compartment cartilage defects. DESIGN: All subjects (at baseline n = 88, >18 years old) underwent 3-Tesla knee MRI at baseline and annually thereafter for 3 years. The MR studies were evaluated for presence of cartilage defects (modified Whole-Organ Magnetic Resonance Imaging Scoring - mWORMS), and quantitative T1ρ and T2 relaxation time maps. Subjects were segregated into those with (mWORMS ≥2) and without (mWORMS ≤1) cartilage lesions at the medial tibia (MT) or medial femur (MF) at each time point. Laminar (bone and articular layer) and spatial (gray level co-occurrence matrix - GLCM) distribution of the T1ρ and T2 relaxation time maps were calculated. Linear regression models (cross-sectional) and Generalized Estimating Equations (GEEs) (longitudinal) were used. RESULTS: Global T1ρ, global T2 and articular layer T2 relaxation times at the MF, and global and articular layer T2 relaxation times at the MT, were higher in subjects with cartilage lesions compared to those without lesions. At the MT global T1ρ relaxation times were higher at each time point in subjects with lesions. MT T1ρ and T2 became progressively more heterogeneous than control compartments over the course of the study. CONCLUSION: Spatial distribution of T1ρ and T2 relaxation time maps in medial knee OA using GLCM technique may be a sensitive indicator of cartilage deterioration, in addition to whole-compartment relaxation time data.

Response of knee cartilage T1rho and T2 relaxation times to in vivo mechanical loading in individuals with and without knee osteoarthritis.

OBJECTIVE: The objective of this study was to evaluate the effects of mechanical loading on knee articular cartilage T1ρ and T2 relaxation times in patients with and without osteoarthritis (OA). DESIGN: Magnetic resonance (MR) images were acquired from 137 subjects with and without knee OA under two conditions: unloaded and loaded at 50% body weight. Three sequences were acquired: a high-resolution 3D-CUBE, a T1ρ relaxation time, and a T2 relaxation time sequences. Cartilage regions of interest included: medial and lateral femur (MF, LF); medial and lateral tibia (MT, LT), laminar analysis (superficial and deep layers), and subcompartments. Changes in relaxation times in response to loading were evaluated. RESULTS: In response to loading, we observed significant reductions in T1ρ relaxation times in the MT and LT. In both the MF and LF, loading resulted in significant decreases in the superficial layer and significant increases in the deep layer of the cartilage for T1ρ and T2. All subcompartments of the MT and LT showed significant reduction in T1ρ relaxation times. Reductions were larger for subjects with OA (range: 13-19% change) when compared to healthy controls (range: 3-13% change). CONCLUSIONS: Loading of the cartilage resulted in significant changes in relaxation times in the femur and tibia, with novel findings regarding laminar and subcompartmental variations. In general, changes in relaxation times with loading were larger in the OA group suggesting that the collagen-proteoglycan matrix of subjects with OA is less capable of retaining water, and may reflect a reduced ability to dissipate loads.

T1ρ and T2 relaxation times predict progression of knee osteoarthritis.

OBJECTIVE: To evaluate whether T(2) and T(1ρ) relaxation times of knee cartilage determined with 3T magnetic resonance imaging (MRI) at baseline predict longitudinal progression of cartilage degenerative changes. METHODS: Quantitative analysis of cartilage was performed using 3T MRI with both T(2) and T(1ρ) mapping techniques in 55 subjects without evidence of severe osteoarthritis (OA) [Kellgren-Lawrence (KL) score of 0-3] at baseline. Morphological abnormalities of cartilage, menisci, ligaments and bone marrow were analyzed on sagittal fat-saturated intermediate-weighted fast spin echo (FSE) sequences. Progression of degenerative changes was analyzed over a period of 2 years. Progression was detected in 27 subjects while in 28 subjects no changes were found. Differences between T(2) and T(1ρ) relaxation times in these two cohorts were compared using one-way analysis of variance (ANOVA) and t tests. RESULTS: Baseline T(2) and T(1ρ) values were significantly higher in the progression cohort in all compartments (P < 0.05) except the lateral tibia (LT) for T(2) and the medial tibia (MT) for T(1ρ). Progression of cartilage degenerative disease was most pronounced at the medial femoral condyles and at the femoro-patellar joint; differences between the two cohorts for T(2) and T(1ρ) were also most significant in these compartments. CONCLUSIONS: T(2) and T(1ρ) measurements were significantly higher at baseline in individuals that showed progression of cartilage abnormalities over a period of 2 years and may therefore serve as potential predictors for progression of degenerative cartilage abnormalities in knee OA.

Bone and cartilage demonstrate changes localized to bone marrow edema-like lesions within osteoarthritic knees.

OBJECTIVE: Our objective is to understand the biological and mechanical pathways linking cartilage, bone, and marrow changes in the progression of osteoarthritis (OA). The aim of the present study was to evaluate bone structure and composition within bone marrow edema-like lesion (BMEL) regions associated with knee OA. METHODS: Tibial plateau specimens (n = 18) were collected from 10 subjects with knee OA during total knee arthroplasty (TKA). Magnetic resonance (MR) imaging was used to identify BMEL and quantify metrics of cartilage composition. Micro-computed tomography (µCT) and high-resolution peripheral quantitative computed tomography (HR-pQCT) were used to quantify density and microstructure of the subchondral trabecular bone. Fourier transform infrared (FTIR) spectroscopy was used to quantify tissue composition. RESULTS: Trabecular bone within BMEL was higher in volume fraction, with more and thicker trabeculae that were more plate-like in structure compared to unaffected regions. BMEL trabecular tissue composition had decreased phosphate and carbonate content. Marrow infiltration by a fibrous collagen network and evidence of increased bone remodeling were present. Structural and compositional changes were specifically localized to regions underlying cartilage degradation. CONCLUSION: These results support the paradigm of focal interactions among bone, marrow, and cartilage in the progression of knee OA. Quantitative evaluation of tissue changes and interactions may aid in the understanding of disease pathophysiology and provide imaging markers for disease progression.

Trabecular bone structure and spatial differences in articular cartilage MR relaxation times in individuals with posterior horn medial meniscal tears.

OBJECTIVE: To analyze knee trabecular bone structure and spatial cartilage T(1ρ) and T(2) relaxation times using 3-T magnetic resonance imaging (MRI) in subjects with and without tears of posterior horn of the medial meniscus (PHMM). DESIGN: 3-T MRI from 59 subjects (>18 years), were used to evaluate PHMM tears based on modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) scoring; and to calculate apparent trabecular bone-volume over total bone volume fraction (app. BV/TV), apparent trabecular number (app. Tb.N), apparent trabecular separation (app. Tb.Sp) and apparent trabecular thickness (app. Tb.Th) for overall femur/tibia and medial/lateral femur/tibia; and relaxation times for deep and superficial layers of articular cartilage. A repeated measures analysis using Generalized Estimating Equation (GEE) was performed to compare trabecular bone and cartilage relaxation time parameters between people with (n = 35) and without (n = 24) PHMM tears, while adjusting for age and knee OA presence. RESULTS: Subjects with PHMM tears had lower app. BV/TV and app. Tb.N, and greater app. Tb.Th, and app. Tb.Sp. They also had higher T(1ρ) times in the deep cartilage layer for lateral tibia and medial femur and higher T(2) relaxation times for the deep cartilage layer across all compartments. CONCLUSIONS: PHMM tears are associated with differences in underlying trabecular bone and deep layer of cartilage. Over-load of subchondral bone can lead to its sclerosis and stress shielding of trabecular bone leading to the resorptive changes observed in this study. The results underline the importance of interactions of trabecular bone and cartilage in the pathogenesis of knee OA in people with PHMM tears.

Comparing the phenomenological qualities of stimulus-independent thought, stimulus-dependent thought and dreams using experience sampling.

Humans spend a considerable portion of their lives engaged in 'stimulus-independent thoughts' (SIT), or mental activity that occurs independently of input from the immediate external environment. Although such SITs are, by definition, different from thoughts that are driven by stimuli in one's external environment (i.e. stimulus-dependent thoughts; SDTs), at times, the phenomenology of these two types of thought appears to be deceptively similar. But how similar are they? We address this question by comparing the content of two types of SIT (dreaming and waking SITs) with the content of SDTs. In this 7 day, smartphone-based experience-sampling procedure, participants were intermittently probed during the day and night to indicate whether their current thoughts were stimulus dependent or stimulus independent. They then responded to content-based items indexing the qualitative aspects of their experience (e.g. My thoughts were jumping from topic to topic). Results indicate substantial distinctiveness between these three types of thought: significant differences between at least two of the three mental states were found across every measured variable. Implications are discussed. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Effect of membrane potential and internal pH on active sodium-potassium transport and on ATP content in high-potassium sheep erythrocytes.

Ouabain-sensitive Na+ and K+ fluxes and ATP content were determined in high potassium sheep erythrocytes at different values of membrane potential and internal pH. Membrane potential was adjusted by suspending erythrocytes in media containing different concentrations of MgCl2 and sucrose. Concomitantly either the external pH was changed sufficiently to maintain a constant internal pH or the external pH was kept constant with a resultant change of internal pH. The erythrocytes were preincubated before the flux experiment started in a medium which produced increased ATP content in order to avoid substrate limitation of the pump. It was found that an increased cellular pH reduced the rates of active transport of Na+ and K+ without significantly altering the ratio of pumped Na+/K+. This reduction was not due to limitation in the supply of ATP although ATP content decreased when internal pH increased. Changes of membrane potential in the range between -10 and +60 mV at constant internal pH did not affect the rates of active transport of Na+ or K+.

Composites, compromises, and CHARM: what is the evidence for blend memory representations?

Metcalfe's (1990) distributed memory model simulates many misinformation effects by assuming representations that superimpose information from multiple sources. In the present article, two types of evidence are reviewed for such "blend" representations: composite recollections, including items from both the original and postevent sources (e.g., a previously seen intersection is remembered with a subsequently suggested stop sign), and compromise recollections, including features that cannot be exclusively associated with either source (e.g., a green car that was later suggested to be blue is remembered as bluish green). The considerable evidence for composite recollections provides little support for blend representations. Compromise recollections, though seemingly more persuasive, are both rare and interpretable without postulating blend representations. Speculation is made about potential findings that would support blend representations.

The fate of memory: comment on McCloskey and Zaragoza.

McCloskey and Zaragoza (1985) argue that misleading postevent suggestions do not affect the availability of originally encoded information. Their hypothesis stems from empirical work using a modified paradigm in which no effect of postevent information is observed. Although their "no impairment" hypothesis is plausible, careful consideration of the predictions of their experimental test suggests that it may be insufficiently sensitive to reveal the impact of postevent information. A small effect of postevent information can be observed when their paradigm is repeated with a more sensitive recognition test. McCloskey and Zaragoza's no impairment hypothesis is also difficult to reconcile with numerous reports of "blend" memories that reflect a compromise between the original and postevent information.

Thinking too much: introspection can reduce the quality of preferences and decisions.

In Study 1, college students' preferences for different brands of strawberry jams were compared with experts' ratings of the jams. Students who analyzed why they felt the way they did agreed less with the experts than students who did not. In Study 2, college students' preferences for college courses were compared with expert opinion. Some students were asked to analyze reasons; others were asked to evaluate all attributes of all courses. Both kinds of introspection caused people to make choices that, compared with control subjects', corresponded less with expert opinion. Analyzing reasons can focus people's attention on nonoptimal criteria, causing them to base their subsequent choices on these criteria. Evaluating multiple attributes can moderate people's judgments, causing them to discriminate less between the different alternatives.

Stereotype distinctiveness: how counterstereotypic behavior shapes the self-concept.

Three experiments examined the relationship between distinctiveness and self-schematicity. Experiment 1 revealed that people were more likely to be self-schematic in domains of strong performance when they felt distinct from family and peers in those domains. Experiments 2 and 3 extended this finding into the arena of stereotypes by demonstrating that people were more likely to be self-schematic in domains of strong performance when their performance was counterstereotypic rather than stereotypic. In particular, African Americans and women were more likely to be schematic for intelligence than Caucasians and men if they performed well academically, whereas Caucasians-especially men-were more likely than African Americans to be schematic for athletics if they performed well athletically. These results suggest that counterstereotypic behavior plays a uniquely powerful role in the development of the self-concept.

Verbal vulnerability of perceptual expertise.

Three experiments explored the role of perceptual expertise in mediating the finding (termed verbal overshadowing) that describing a face can impair later recognition. In Experiment 1, verbalization impaired White participants' recognition of White faces (expert domain) but not African American faces (novice domain). In Experiment 2, judges attempted to identify targets on the basis of the verbal descriptions generated in Experiment 1. Experiment 2 revealed a significant relationship between verbalization participants' recognition performance and yoked judges' identification performance for other-race but not own-race faces, suggesting that other-race recognition may involve a unique reliance on "verbalizable" information. In Experiment 3, the interaction between verbalization and race of face was replicated with upright faces but was attenuated with inverted recognition arrays (a manipulation that reduces the influence of configural information). Collectively, these findings suggest that verbalization may disrupt the nonreportable configural processes associated with recognizing stimuli with which one is an expert.

Qualities of the unreal.

Witnesses to complex events often recall nonexistent objects after being exposed to misleading postevent information. The present series of experiments investigated whether descriptions of these "unreal" memories differ from those of memories based on perception. In Experiment 1 subjects viewed a slide sequence depicting a traffic accident. In one condition, the sequence included a slide involving a yield sign. In a second condition, subjects did not see the sign but merely had its existence suggested. Many subjects in both groups later reported seeing the sign, and these subjects provided verbal descriptions. Descriptions that resulted from suggestion were longer and contained more hedges, more reference to cognitive operations, and fewer sensory details. Experiment 2 replicated these findings with a different object. Experiment 3 investigated judges' ability to discriminate the source of the descriptions based on perception and suggestion. Although judges often employed the appropriate criteria, their performance was only slightly above chance. Experiments 4 and 5 revealed that providing judges with clues regarding differences between perceived and suggested memories facilitated discrimination. The results of these experiments indicate that subtle differences exist between perceived and suggested memories, that people have a minimal ability to detect these differences, and that instructions can improve that ability.

Attenuating verbal overshadowing through color retrieval cues.

Five experiments showed that interference resulting from verbalizing visual stimuli (verbal overshadowing) can be reduced by reintroducing visual cues present at encoding. Object color and background color were used as cues. Participants learned either easy- or hard-to-name figures and then performed an image rotation task. Before performing the imagery task, participants were re-presented with the color patch associated with each figure. Color re-presentation attenuated the impairment associated with easy-to-name stimuli (Experiment 1) as well as labeled hard-to-name stimuli (Experiment 2). However, background color cues had no effect on imagery performance (Experiment 3). Experiment 4 showed that naming the object colors at encoding makes color retrieval cues ineffective. Finally, Experiment 5 showed that object color cues can help participants to overcome previously exhibited impairment resulting from covert verbalization.

The distinctions of false and fuzzy memories.

Fuzzy-trace theory has recently been used to account for various types of "false memories" (Brainerd & Reyna, 1998, this issue). Although components of fuzzy-trace theory-in particular the distinction between gist and verbatim traces-overlap with distinctions made in other theories of memory, those in fuzzy-trace theory provide an illuminating account of the conditions under which semantic associates of previously seen items are erroneously recognized. However, the theory is less useful in explaining misinformation effects. Fuzzy-trace theory's differential success in accounting for these two types of errors follows from one of its central implications: whereas misinformation effects involve false memories, the erroneous recognition of related lures is due to a reliance on authentic, but underspecified, gist memories. As its name suggests, fuzzy-trace theory is best at explaining memory errors resulting from fuzzy traces. Consistent with this view, fuzzy-trace theory helps to explain another source of memory errors (verbal overshadowing of nonverbal memories) that may also be best characterized as resulting from a reliance on fuzzy, rather than false, memories.

Verbal overshadowing of visual memories: some things are better left unsaid.

It is widely believed that verbal processing generally improves memory performance. However, in a series of six experiments, verbalizing the appearance of previously seen visual stimuli impaired subsequent recognition performance. In Experiment 1, subjects viewed a videotape including a salient individual. Later, some subjects described the individual's face. Subjects who verbalized the face performed less well on a subsequent recognition test than control subjects who did not engage in memory verbalization. The results of Experiment 2 replicated those of Experiment 1 and further clarified the effect of memory verbalization by demonstrating that visualization does not impair face recognition. In Experiments 3 and 4 we explored the hypothesis that memory verbalization impairs memory for stimuli that are difficult to put into words. In Experiment 3 memory impairment followed the verbalization of a different visual stimulus: color. In Experiment 4 marginal memory improvement followed the verbalization of a verbal stimulus: a brief spoken statement. In Experiments 5 and 6 the source of verbally induced memory impairment was explored. The results of Experiment 5 suggested that the impairment does not reflect a temporary verbal set, but rather indicates relatively long-lasting memory interference. Finally, Experiment 6 demonstrated that limiting subjects' time to make recognition decisions alleviates the impairment, suggesting that memory verbalization overshadows but does not eradicate the original visual memory. This collection of results is consistent with a recording interference hypothesis: verbalizing a visual memory may produce a verbally biased memory representation that can interfere with the application of the original visual memory.

The verbal overshadowing effect: why descriptions impair face recognition.

Three experiments explored the verbal overshadowing effect, that is, the phenomenon that describing a previously seen face impairs recognition of this face. There were three main results: First, a verbal overshadowing effect was obtained both when subjects were provided with and when they generated a description of an earlier seen face. Second, instructing subjects at the time of test to be aware of potentially competing memories did not improve, and may even have worsened, recognition performance when the subjects had generated a description of the target face. However, these instructions improved performance and eliminated the verbal overshadowing effect when subjects were provided with someone else's description of the target face. Third, recognition of the target face was disrupted when subjects described a completely different face, such as their parent's face or a face of the opposite sex. The results are discussed in relation to two potential mechanisms: source confusion between previously encoded visual and verbal representations of the face and a shift in processing of the test faces at recognition.

Justification effects on the judgment of analogy.

Many of us share a strong intuition that justification forces us to better understand the situations we face. And there is substantial evidence indicating that this is often the case. However, there is a growing body of research showing that, under certain circumstances, explanation and justification can impair performance on a variety of cognitive tasks. In the present research, the effects of justification on judgment of the soundness of analogies were examined. Subjects judged the quality of the match between pairs of stories with varying degrees of superficial and analogical similarity. Experimental subjects either provided reasons for their judgments or wrote recollections of the target stimuli. These subjects rated the match between stimulus pairs as more sound than did control subjects. Also, providing reasons led to poorer discrimination between superficially similar aspects of the stimuli and analogous aspects. Explanations of these findings are proposed, and implications for problem solving and confidence judgment are discussed.